全文获取类型
收费全文 | 104131篇 |
免费 | 6006篇 |
国内免费 | 311篇 |
专业分类
林业 | 4516篇 |
农学 | 3575篇 |
基础科学 | 751篇 |
13214篇 | |
综合类 | 16676篇 |
农作物 | 4062篇 |
水产渔业 | 4990篇 |
畜牧兽医 | 54284篇 |
园艺 | 1229篇 |
植物保护 | 7151篇 |
出版年
2018年 | 1590篇 |
2017年 | 1731篇 |
2016年 | 1585篇 |
2015年 | 1361篇 |
2014年 | 1678篇 |
2013年 | 4221篇 |
2012年 | 2975篇 |
2011年 | 3465篇 |
2010年 | 2381篇 |
2009年 | 2454篇 |
2008年 | 3505篇 |
2007年 | 3244篇 |
2006年 | 3053篇 |
2005年 | 2824篇 |
2004年 | 2661篇 |
2003年 | 2825篇 |
2002年 | 2533篇 |
2001年 | 3236篇 |
2000年 | 3167篇 |
1999年 | 2479篇 |
1998年 | 1039篇 |
1997年 | 1120篇 |
1996年 | 962篇 |
1995年 | 1174篇 |
1994年 | 1010篇 |
1993年 | 972篇 |
1992年 | 2019篇 |
1991年 | 2245篇 |
1990年 | 2154篇 |
1989年 | 2170篇 |
1988年 | 2030篇 |
1987年 | 1958篇 |
1986年 | 2053篇 |
1985年 | 1918篇 |
1984年 | 1647篇 |
1983年 | 1383篇 |
1982年 | 977篇 |
1979年 | 1596篇 |
1978年 | 1249篇 |
1977年 | 1141篇 |
1976年 | 1080篇 |
1975年 | 1157篇 |
1974年 | 1406篇 |
1973年 | 1456篇 |
1972年 | 1385篇 |
1971年 | 1232篇 |
1970年 | 1219篇 |
1969年 | 1230篇 |
1968年 | 1067篇 |
1967年 | 1139篇 |
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
991.
The formation of roots and shoots on root segments of Rubus procerus P.J. Muell was prevented by soaking the segments for 24 h in a 10?4M solution of 2,4,5-T or a 10?5M solution of picloram. Shoot numbers were significantly increased after treatment with 10?9M and 10?10M 2,4,5-T, but picloram did not cause a significant increase in shoot numbers. Measurement of the concentration of 2,4,5-T in the extracambial tissue showed that roots treated with 10?4M 2,4,5-T contained 5× 10?8 mmole 2,4,5-T per mg dry weight, and by extrapolation, roots treated with 10?9M 2,4,5-T contained 2× 10?10 mmole/mg dry weight. Action du 2,4,5-T et du piclorame sur la régénération de la ronce (Rubus procerus P.J. Muell) è partir de fragments de racines La formation de racines et de tiges è partir de fragments de racines dc Ruhus procerus P.J. Muell a été supprimée par trempage des fragmenls pendant 24 heures dans une solution a 10?4M et de 2.4,5-T, ou dans une solution 10?5M de piclorame. Le nombre de pousses s'est accru significativement après traitement avec le 2,4,5.-T è 10?9M et 10?10M, mais le piclorame n'a pas provoqué d'accroissemcnt significatif du nombre de pousses. La mesure de la concentration de 2,4,5-T dans le tissu extra-cambial a montré que les racines trailées avec du 2,4,5-T è 10?4M contenaient 5×10?8 mmole de 2.4,5-T par mg de poids sec et par extrapolation, quc les racines traitées avec du 2,4,5-T k 10?9M devaient contenir 2 × 10?12 mmole/mg de poids sec. Die Wirkiing von 2,4,5-T und Picloram auf den Wuchs der Wurzehegmenten von Bromheeren (Rubus procerus P.J. Muell). Die Bildung von Wurzeln und Sprossen aus Wurzelsegmen-ten von Ruhu.i procerus P.J. Muell wurde durch 24-stündiges Einlegen der Wurzelstücke in 10?4M 2,4,5-T bzw 10?5M Picloram verhindert. Die Anzahl neugebiideter Sprosse wurde nach Einlegen in 10?9M und 10?10M 2,4,5-T, nicht jedoch durch Picloram, signifikant erhöht. Im extracambialen Gewebe von Wurzeln, die mit 10?4M 2,4,5-T behand-elt worden waren, wurden 5×10?8mMol 2,4,5-T je mg Trockengewiclu bestimmt. Durch Extrapolation wurde ermittclt. dass mit 10?9M 2,4,5-T behandelte Wurzeln 2× 10?12mMol/mg Trockengewicht cnthielten. 相似文献
992.
Root-treated alfalfa absorbs, translocates, and metabolizes [phenyl-14C]isopropyl carbanilate ([14C]propham). After 7 days of root treatment, the distribution of radiolabel was 73% for shoots and 27% for roots. Shoots and roots were extracted and separated into the polar, nonpolar, and solid residual components using a mixture of chloroform, methanol and water. The insoluble residues accounted for approximately 40% of the 14C found in shoots and roots. The nonpolar fraction (6.1% of the radiolabel in shoots and roots) was not characterized, but was shown to be some component other than parent propham. Propham was not found in either shoots or roots. The polar metabolites were partly purified on Amberlite XAD-2. Cellulase-liberated aglycones were derivatized and separated by high-performance liquid and gas-liquid chromatography. The infrared, nuclear magnetic resonance, and mass spectral data showed that the polar metabolites of alfalfa shoots and roots were glycoside conjugates of isopropyl 2-hydroxycarbanilate (2-hydroxypropham) and isopropyl 4-hydroxycarbanilate (4-hydroxypropham). Conjugated 4-hydroxypropham accounted for 45.9% of the 14C in the shoots and 3.4% of the 14C in the roots. Conjugated 2-hydroxypropham accounted for 3.4% of the 14C in the shoots and 1.4% of the 14C in the roots. 相似文献
993.
R. G. Richardson 《Weed Research》1975,15(5):335-337
Temperatures from 13°C to 30°C had no significant effect on the formation of shoots on root segments of Rubus procerus P. J. Muell. Shoots were not produced at 8°C. Some new roots were produced on root segments at all temperatures between 8°C and 30°C, although significantly more (P= 0·05) roots were produced at 26°C. The polarity of the root system was maintained in root segments. More shoots were formed towards the basal end, i.e. nearest the crown, and more roots towards the apical end of the root segments. 相似文献
994.
Gülşen Sertkaya Marta Martini Paolo Ermacora Rita Musetti Ruggero Osler 《Phytoparasitica》2005,33(4):380-390
During the late summer-early autumn of 2002, surveys were carried out in Turkey to determine the presence of phytoplasma diseases
in fruit trees. Phytoplasmas were detected and characterized by PCR-RFLP analysis and TEM technique in stone fruit and pear
trees in the eastern Mediterranean region of the country. Six out of 24 samples, including almond, apricot, peach, pear and
plum, gave positive results in PCR assays. RFLP analysis usingSspI andBsaAI enzymes of PCR products obtained with primer pair f01/r01 enabled identification of the phytoplasmas involved in the diseases.
Stone fruit trees, including a local apricot variety (‘Sakıt’) and a pear sample, were found to be infected with European
stone fruit yellows (ESFY, 16SrX-B) and pear decline (PD, 16SrX-C) phytoplasmas, respectively. This is the first report in
Turkey of PD phytoplasma infecting pear and of ESFY phytoplasma infecting almond, apricot, myrobalan plum and peach; ESFY
phytoplasma infecting Japanese plum was previously reported.
http://www.phytoparasitica.org posting July 21, 2005. 相似文献
995.
The establishment of predacious mites in commercial orchards may be accelerated by the transfer of pruned wood in winter and
summer from donor orchards to release orchards. Following winter pruning, 3-year-old and older wood is collected and transported
as soon as possible in bundles to a release orchard for distribution. If the release orchard is composed of dwarf trees, then
one or two bundles of 5 kg each are placed vertically at the base of the trunk of every tree in the block (0.5 to 1 ha); if
the trees are of standard size, then four or five bundles used. Following summer pruning, annual shoots and suckers are distributed
immediately in a release orchard composed of dwarf trees by placing 12–15 branches on the foliage of fruit-bearing branches;
if the release orchard is composed of standard trees, then 50 branches are used. The pruned wood should have 20–25 leaves
and not less than one predator per leaf. The release orchard should have a light infestation (two or three mites per leaf)
of pest tetranychids. These phytophagous mites would serve as food and help establish the predators. The release orchard grower
should develop a pest management program based on the same groups of pesticides used in the donor orchard.
http://www.phytoparasitica.org posting Aug. 31, 2005. 相似文献
996.
Resistance to bifenthrin and resistance mechanisms of different strains of the two-spotted spider mite (Tetranychus urticae) from Turkey 总被引:2,自引:0,他引:2
Nine different strains of the two-spotted spider miteTetranychus urticae Koch (Acari: Tetranychidae) were collected on cotton from Adana, Antalya, Izmir, Manisa and Urfa in Turkey. Their responses
to bifenthrin were investigated using conventional bioassay and biochemical assays. LC50 and LC90 values of bifenthrin were determined for all strains by using a residual bioassay with a petri dish-spray tower. Resistance
ratios were determined by comparing the samples with a standard susceptible strain, GSS. The resistance ratios of the strains
ranged from <1 to 669-fold (at LC50). Of the investigated field strains, only three (two from Adana and one from Urfa) were resistant to bifenthrin. There was
a correlation between esterase enzyme activity and bifenthrin resistance according to polyacrylamide gel electrophoresis and
microtiter plate assays in the three resistant strains.
http://www.phytoparasitica.org posting May 17, 2005. 相似文献
997.
Annette N. Smith J. A. Vaughn M. Whatley A. Truett J. Keen 《Veterinary and comparative oncology》2005,3(1):55-55
Introduction: Vascular endothelial growth factor (VEGF) is one of the most important mediators of angiogenesis. Elevated levels within tumors, and in serum, plasma, and tumor effusion have been correlated with the development of metastatic disease, recurrence, and poor prognosis in many tumors in humans. Canine VEGF has been sequenced as homologous with the human form, and elevated serum and plasma VEGF have been found in dogs with hemangiosarcoma. Feline VEGF has also been sequenced, and shares homology with the human and canine forms.
Materials and Methods: Stored serum and plasma samples from normal cats, cats with various neoplasms, and cats with non‐neoplastic disease were evaluated with a commercial ELISA kit (R&D Systems, Minneapolis MN). Samples were run in duplicate, and a standard curve was performed for each plate. The data were analyzed for differences between populations, and between serum and plasma levels in the same patient to determine the optimal sample for evaluating VEGF in cats.
Results: In seven apparently healthy cats mean plasma VEGF was 95.6 pg/mL. In non‐neoplastic disease (7 cases), mean plasma VEGF was 117.3 pg/mL and mean serum VEGF level was 219.7 pg/mL. In ten tumor‐bearing patients mean plasma VEGF was 247.1 pg/mL, and mean serum VEGF was 322.3 pg/mL. Statistical analysis showed no significant difference between mean serum and plasma VEGF concentrations within each group or between groups (p > 0.05).
Discussion: Serum and plasma VEGF levels could not be used to distinguish between healthy cats and cats with neoplastic or non‐neoplastic disease. 相似文献
Materials and Methods: Stored serum and plasma samples from normal cats, cats with various neoplasms, and cats with non‐neoplastic disease were evaluated with a commercial ELISA kit (R&D Systems, Minneapolis MN). Samples were run in duplicate, and a standard curve was performed for each plate. The data were analyzed for differences between populations, and between serum and plasma levels in the same patient to determine the optimal sample for evaluating VEGF in cats.
Results: In seven apparently healthy cats mean plasma VEGF was 95.6 pg/mL. In non‐neoplastic disease (7 cases), mean plasma VEGF was 117.3 pg/mL and mean serum VEGF level was 219.7 pg/mL. In ten tumor‐bearing patients mean plasma VEGF was 247.1 pg/mL, and mean serum VEGF was 322.3 pg/mL. Statistical analysis showed no significant difference between mean serum and plasma VEGF concentrations within each group or between groups (p > 0.05).
Discussion: Serum and plasma VEGF levels could not be used to distinguish between healthy cats and cats with neoplastic or non‐neoplastic disease. 相似文献
998.
D. W. Knapp B. Filion M. C. Filion N. C. Phillips 《Veterinary and comparative oncology》2005,3(1):46-47
Introduction: Mycobacterial cell wall‐DNA complex (MCC) is a bifunctional anticancer agent that induces cancer cell apoptosis and stimulates cytokine synthesis by immune cells. Intravesical MCC is currently being evaluated in humans with high‐grade urinary bladder cancer. Evaluation of MCC in dogs with transitional cell carcinoma (TCC) will allow mechanistic studies in a natural animal model of TCC, and a potentially beneficial therapy for dogs with this cancer. In this study, we have determined the anticancer activity of MCC against canine TCC cells in vitro .
Methods: Canine TCC cells (K9TCC cell line) were incubated with MCC (0.05–100 μg/ml, 0.5–72 hours). Cellular proliferation was measured by MTT reduction. Cell cycle was analyzed by flow cytometry with propidium iodide. Apoptosis was identified by flow cytometry using anti‐active‐caspase‐3/PE and anti‐cleaved‐PARP/FITC antibodies. Apoptosis‐inducing activity of 100 μg/ml MCC in combination with piroxicam (0.1–1.0 uM) was evaluated.
Results: MCC inhibited K9TCC cell proliferation in a concentration‐dependent manner (maximal activity – 45% at 100 μg/ml MCC) in association with the presence of activated caspase‐3 and cleaved PARP. Inhibition of proliferation and apoptosis‐inducing activities of MCC were independent of cell cycle phase. A thirty‐minute exposure of MCC was sufficient for optimal activity. Piroxicam (0.5 uM) enhanced apoptosis‐inducing activity of MCC.
Conclusions: MCC induces apoptosis in K9TCC cells. This activity is potentiated by piroxicam. Following positive results in vitro , in vivo studies have been initiated. One dog, treated to date, has had a minor reduction in tumor volume following the first course of treatment with no treatment‐related toxicity. 相似文献
Methods: Canine TCC cells (K9TCC cell line) were incubated with MCC (0.05–100 μg/ml, 0.5–72 hours). Cellular proliferation was measured by MTT reduction. Cell cycle was analyzed by flow cytometry with propidium iodide. Apoptosis was identified by flow cytometry using anti‐active‐caspase‐3/PE and anti‐cleaved‐PARP/FITC antibodies. Apoptosis‐inducing activity of 100 μg/ml MCC in combination with piroxicam (0.1–1.0 uM) was evaluated.
Results: MCC inhibited K9TCC cell proliferation in a concentration‐dependent manner (maximal activity – 45% at 100 μg/ml MCC) in association with the presence of activated caspase‐3 and cleaved PARP. Inhibition of proliferation and apoptosis‐inducing activities of MCC were independent of cell cycle phase. A thirty‐minute exposure of MCC was sufficient for optimal activity. Piroxicam (0.5 uM) enhanced apoptosis‐inducing activity of MCC.
Conclusions: MCC induces apoptosis in K9TCC cells. This activity is potentiated by piroxicam. Following positive results in vitro , in vivo studies have been initiated. One dog, treated to date, has had a minor reduction in tumor volume following the first course of treatment with no treatment‐related toxicity. 相似文献
999.
A. K. LeBlanc ‡§ G. E. Mauldin R. J. Milner K. L. Cooke T. A. LaDue G. N. Mauldin 《Veterinary and comparative oncology》2005,3(1):47-48
Introduction: MOPP chemotherapy is useful for relapsed canine lymphoma. This study evaluates the efficacy of this protocol after substitution of CCNU (lomustine) or BiCNU (carmustine) for mechlorethamine (C/B‐OPP).
Methods: Patient signalment, response to chemotherapy, toxicity and survival data were abstracted from medical records of dogs from receiving C/B‐OPP between 1998 and 2004.
Results: Fifty‐eight dogs received C/B‐OPP rescue chemotherapy during the study period. The median remission duration after initial chemotherapy, consisting of CHOP‐based therapy in 91% of dogs, was 133 days (range, 10 to 932 days). Thirty‐eight of fifty‐eight dogs (66%) responded to C/B‐OPP rescue after relapse (22 CR, 16 PR), for a median of 48 days (range, 2 to 359 days). Overall, C/B‐OPP extended survival by a median of 90 days (range, 2 to 426 days). Twenty‐four dogs (41%) experienced one or more episodes of Grade II or higher gastrointestinal toxicity. Forty‐one dogs (71%) experienced one or more episodes of Grade II or higher hematologic toxicity. Twelve dogs (20%) developed regenerative anemia with diarrhea consistent with gastrointestinal hemorrhage. Treatment delays due to hematologic toxicity occurred in 37 dogs (63%). There were 16 nonfatal treatment‐related episodes of sepsis requiring hospitalization. 5 dogs died due to sepsis and/or chemotherapy‐related complications.
Conclusions: C/B‐OPP chemotherapy has activity against relapsed canine lymphoma which is similar to that of traditional MOPP rescue therapy. Moderate to severe hematologic toxicity was observed. Further work is warranted to optimize drug doses and scheduling. 相似文献
Methods: Patient signalment, response to chemotherapy, toxicity and survival data were abstracted from medical records of dogs from receiving C/B‐OPP between 1998 and 2004.
Results: Fifty‐eight dogs received C/B‐OPP rescue chemotherapy during the study period. The median remission duration after initial chemotherapy, consisting of CHOP‐based therapy in 91% of dogs, was 133 days (range, 10 to 932 days). Thirty‐eight of fifty‐eight dogs (66%) responded to C/B‐OPP rescue after relapse (22 CR, 16 PR), for a median of 48 days (range, 2 to 359 days). Overall, C/B‐OPP extended survival by a median of 90 days (range, 2 to 426 days). Twenty‐four dogs (41%) experienced one or more episodes of Grade II or higher gastrointestinal toxicity. Forty‐one dogs (71%) experienced one or more episodes of Grade II or higher hematologic toxicity. Twelve dogs (20%) developed regenerative anemia with diarrhea consistent with gastrointestinal hemorrhage. Treatment delays due to hematologic toxicity occurred in 37 dogs (63%). There were 16 nonfatal treatment‐related episodes of sepsis requiring hospitalization. 5 dogs died due to sepsis and/or chemotherapy‐related complications.
Conclusions: C/B‐OPP chemotherapy has activity against relapsed canine lymphoma which is similar to that of traditional MOPP rescue therapy. Moderate to severe hematologic toxicity was observed. Further work is warranted to optimize drug doses and scheduling. 相似文献
1000.
F. Gentilini C. Calzolari A. Buonacucina M. Di Tommaso G. Militerno P. Famigli Bergamini 《Veterinary and comparative oncology》2005,3(2):87-97
Waldenström Macroglobulinemia is a low‐grade immunosecretory disorder associated with lymphoid tumours, which is rarely reported in veterinary medicine. In this study, we describe two clinical cases of this rare syndrome in dogs, each characterized by a different onset and clinical course. In one case, a hyperacute onset and aggressive behaviour of the neoplasm was observed. Absolute serum viscosity (SV) was retrospectively evaluated in order to explain clinical findings. Rotational viscosimetry showed good precision in measuring SV. Both dogs had SV values higher than a control groups of healthy dogs although only one subject developed hyperviscosity symptoms and complications. At high paraprotein concentrations, a slight reduction of the M‐component was associated with a marked decrease in SV. Thus, this work suggests that SV assessment is a relevant tool for managing monoclonal gammopathies, whose usefulness should be further confirmed in larger cohorts of dogs. 相似文献