全文获取类型
收费全文 | 144860篇 |
免费 | 8256篇 |
国内免费 | 110篇 |
专业分类
林业 | 5700篇 |
农学 | 4734篇 |
基础科学 | 925篇 |
17053篇 | |
综合类 | 26095篇 |
农作物 | 5957篇 |
水产渔业 | 7101篇 |
畜牧兽医 | 74258篇 |
园艺 | 1784篇 |
植物保护 | 9619篇 |
出版年
2018年 | 1888篇 |
2017年 | 2158篇 |
2016年 | 2040篇 |
2015年 | 1810篇 |
2014年 | 2179篇 |
2013年 | 5625篇 |
2012年 | 3977篇 |
2011年 | 4740篇 |
2010年 | 3168篇 |
2009年 | 3126篇 |
2008年 | 4690篇 |
2007年 | 4493篇 |
2006年 | 4202篇 |
2005年 | 4037篇 |
2004年 | 3805篇 |
2003年 | 3909篇 |
2002年 | 3646篇 |
2001年 | 4533篇 |
2000年 | 4326篇 |
1999年 | 3510篇 |
1998年 | 1531篇 |
1997年 | 1492篇 |
1996年 | 1325篇 |
1995年 | 1639篇 |
1994年 | 1431篇 |
1993年 | 1438篇 |
1992年 | 2913篇 |
1991年 | 3053篇 |
1990年 | 2973篇 |
1989年 | 3022篇 |
1988年 | 2748篇 |
1987年 | 2793篇 |
1986年 | 2931篇 |
1985年 | 2795篇 |
1984年 | 2304篇 |
1983年 | 2031篇 |
1982年 | 1447篇 |
1979年 | 2075篇 |
1978年 | 1635篇 |
1977年 | 1468篇 |
1976年 | 1402篇 |
1975年 | 1512篇 |
1974年 | 1861篇 |
1973年 | 1929篇 |
1972年 | 1845篇 |
1971年 | 1758篇 |
1970年 | 1660篇 |
1969年 | 1575篇 |
1968年 | 1264篇 |
1967年 | 1404篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Protective activities of heat-inactivated (60 degrees C for 30 min) merthiolate preserved Bordetella bronchiseptica and B. pertussis bacterins were compared in intraperitoneally immunized mice challenged intracerebrally (i.p./i.c.) or intraperitoneally (i.p./i.p.). In the i.p./i.c. assay (Kendrick test), a B. pertussis bacterin protected mice against challenge with B. pertussis 18-323, as well as against phase I cytotoxic and non-cytotoxic strains of B. bronchiseptica. A B. bronchiseptica bacterin, prepared from a phase I cytotoxic strain, gave protection against two phase I B. bronchiseptica strains, irrespective of their cytotoxin-production. A non-cytotoxic phase I strain of B. bronchiseptica elicited protection against the homologous strain only. Neither cytotoxic nor non-cytotoxic B. bronchiseptica strains protected mice challenged with B. pertussis 18-323. Vaccines prepared from phase III strains of B. bronchiseptica were not protective at all against any of the challenge strains. No such differences in the protective activities of the bacterins could be detected by the i.p./i.p. method. They seem to cross-protect equally well. The results indicate that the Kendrick test may be useful in testing potency of different B. bronchiseptica bacterins. 相似文献
102.
A field experiment was conducted during the winter seasons of 1992–93 and 1993–94 at Anand to study the effect of FYM, nitrogen and source of fertilizer on growth and yield of mustard [ Brassica juncea (L.) Czernj & Cosson]. The results showed significant variation in leaf area index (LAI), crop growth rate (CGR), dry matter production and seed yield. The direct effect of farmyard manure (FYM) was conspicuous in improving the growth of mustard. FYM application at 10 tonnes ha−1 significantly increased the LAI, CGR and dry matter accumulation per plant at almost all the stages during first year study (1992–93) and in pooled analysis. Similarly, nitrogen application registered maximum LAI, CGR at 75 kg level and RGR and NAR at 50 kg level at almost all the during both years. Sulphur carrying source (Ammonium sulphate plus single super phosphate) increased all stages growth characters. Maximum dry matter accumulation per plant and seed yield were recorded with highest levels of FYM (20 tonnes ha−1 ), N (75 kg ha−1 ) and source having S. Seed yield was strongly associated with LAI and dry matter accumulation per plant at all the stages. 相似文献
103.
Daniel J. Burba DVM Michael A. Collier DVM Lawrence E. Default PhD Olivia Hanson-Painton PhD Harold C. Thompson Jr. Claude L. Holder 《Journal of Equine Veterinary Science》1993,13(12):696-703
The uptake and distribution of intramuscularly (IM) administered tritium-labeled polysulfated glycosaminoglycan (3H-PSGAG) in serum, synovial fluid, and articular cartilage of eight horses was quantitated, and hyaluronic acid (HA) concentration of the middle carpal joint was evaluated in a pharmacokinetic study. A full-thickness articular cartilage defect, created on the distal articular surface of the left radial carpal bone of each horse served as an osteochondral defect model. 3H-PSGAG (500 mg) was injected IM, between 14 and 35 days after creation of the defects. Scintillation analysis of serum and synovial fluid, collected from both middle carpal joints at specific predetermined times up to 96 hours post-injection, revealed mean 3H-PSGAG concentrations peaked at 2 hours post-injection. 3H-PSGAG was detected in cartilage and subchondral bone 96 hours post-injection in samples from all eight horses. There were no statistically significant differences in 3H-PSGAG concentration of synovial fluid or cartilage between cartilage defect and control (right middle carpal) joints.
HA assay of synovial fluid revealed concentrations significantly increased at 24, 48, and 96 hours post-injection in both joints. The concentration nearly doubled 48 hours post-injection. However, no statistically significant differences were found between synovial concentrations of HA in cartilage defect and control joints.
3H-PSGAG administered IM to horses, was distributed in the blood, synovial fluid, and articular cartilage. HA concentrations in synovial fluid increased after IM administration of polysulfated glycosaminoglycan. 相似文献
104.
A. I. Rey & C. J. López-Bote 《Journal of animal physiology and animal nutrition》2001,85(9-10):281-292
The objective of this study was to assess the effect of dietary copper and/or vitamin E supplementation on composition and oxidation of M. longissimus in Iberian pigs and to compare it with meat samples from pigs produced extensively and fed with acorn and grass. Grass had the highest α-tocopherol content (> 150 mg/kg DM), while acorns had the highest copper concentration (78.1 mg/kg DM). Dietary treatment did not affect copper composition in muscle and no interactions were detected between copper and α-tocopherol. The α-tocopherol content in muscle from pigs fed diets supplemented with α-tocopheryl acetate (100 mg/kg feed) was 1.5 times greater (p < 0.0001) than those from pigs receiving a basel diet. M. longisssimus dorsi from pigs fed extensively had a higher concentration of α-tocopherol than those fed in confinement with the basel level of α-tocopheryl acetate, but lower values than pigs fed supplemented levels. Total n -3 fatty acids (p < 0.02) and hematin (p < 0.0001) concentrations were significantly higher in muscle from pigs fed extensively than when fed in confinement. Muscle homogenates from Iberian pigs fed in extensive conditions showed significantly (p < 0.02) higher susceptibility to oxidation than those from pigs fed mixed diets. Dietary α-tocopheryl acetate supplementation (100 mg/kg feed) significantly (p < 0.05) reduced lipid oxidation of muscle, while dietary copper concentration did not modify susceptibility to lipid oxidation. 相似文献
105.
The reagent carrier Reflotron-Creatinine was tested for its suitability for whole blood and plasma samples of dogs and cats. It showed a very good correlation between the results of Reflotron-Creatinine and the reference method. Using plasma the results of both methods were extremely close. Using whole blood with a hematocrit of up to 50% good results could be achieved. If the hematocrit exceeded 50% large deviations could result. 相似文献
106.
Inheritance process for β-glucan content in oat caryopsis
Due to the fact that there are only few studies concerning β-glucans in oat caryopsis with regard to plant-breeding aspects, three oat crosses were performed (cross 19 = low × high, cross 86 = low × low, cross 98 = high × high). In all of the three oat crosses, lower β-glucan content (% DM) was recorded in F, than in F, indicating that the β-glucan content (% DM) at a higher heterozygoty grade is lower than at a reduced heterozygoty grade. This points to a dominant inheritance of lower β-glucan content (% DM). A tendency towards the female β-glucan content (% DM) could not be proven. Thus, it can be started from a nuclear genetic inheritance of the β-glucan content (% DM). In most cases, the experiments showed a normal distribution of β-glucan content (% DM), indicating for several genes a quantitative inheritance of β-glucan content (% DM). By means of the regression of the F3 -lines to the F2 -plants, the narrow-sense heritability could be calculated for the cross 86 (h2 = 0.51***) and the cross 98 (h2 = 0.48***). The heritability for the cross 19 was not significant. 相似文献
Due to the fact that there are only few studies concerning β-glucans in oat caryopsis with regard to plant-breeding aspects, three oat crosses were performed (cross 19 = low × high, cross 86 = low × low, cross 98 = high × high). In all of the three oat crosses, lower β-glucan content (% DM) was recorded in F, than in F, indicating that the β-glucan content (% DM) at a higher heterozygoty grade is lower than at a reduced heterozygoty grade. This points to a dominant inheritance of lower β-glucan content (% DM). A tendency towards the female β-glucan content (% DM) could not be proven. Thus, it can be started from a nuclear genetic inheritance of the β-glucan content (% DM). In most cases, the experiments showed a normal distribution of β-glucan content (% DM), indicating for several genes a quantitative inheritance of β-glucan content (% DM). By means of the regression of the F
107.
Mark G Papich 《Veterinary Clinics of North America: Equine Practice》2003,19(3):645-63, vi
Antibiotics will always be needed in horses for many types of infections, but the adverse consequences also must be considered. For the conditions described in this article, there is justification for antibiotic therapy. The intestinal problems that antibiotics can induce are among the risks from their administration to horses. Disruption of the endogenous bacterial population, colitis, and diarrhea are the most common complications from antibiotic therapy. 相似文献
108.
109.
Benny J. Woody DVM MS Michael J. Murphy DVM PhD AIlen C. Ray PhD Robert A. Green DVM PhD 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1992,6(1):23-28
The clinical signs and laboratory changes of brodifacoum (BDF) intoxicated dogs and their response to vitamin K1 treatment were examined. Brodifacoum, a second-generation anticoagulant rodenticide, was fed to four dogs for 3 consecutive days producing a cumulative dose of 1.1 mg BDF/kg body weight. Clinical observations of the animals were made daily throughout the study. Monitored laboratory parameters included: one-stage prothrombin time (OSPT), activated partial thromboplastin time (APTT), activated coagulation time (ACT), complete blood counts, thrombocyte counts, and serum chemistry values. Response to vitamin K1 therapy was evaluated clinically and by laboratory tests. Serum BDF concentrations were monitored. Inappetence and hemorrhagic tendencies were exhibited by day 5 postrodenticide exposure. One-stage prothrombin time, APTT, and ACT were 25% greater than time zero values at 24, 24, and 72 hours postdosing, respectively. All laboratory parameters returned to normal within 48 hours of initiating vitamin K1 therapy (0.83 mg/kg orally, TID for 5 days). Serum brodifacoum concentrations were highest (1065-1215 ng/mL) during the 3 days after BDF dosing and were detectable (3.0-7.5 ng/mL) until day 24 postexposure. A mean BDF elimination half-life of 6 +/- 4 days was observed. 相似文献
110.
R. Zabielski S. G. Pierzynowski 《Journal of animal physiology and animal nutrition》1992,68(3):146-150
Eine Methode zur langfristigen Lymphsammlung aus der jejunalen Lymphbahn bei Schweinen und Schafen Es wird eine Methode zur langfristigen Lymphsammlung im Dünndarmbereich von Schweinen und Schafen vorgestellt. Mit Hilfe eines chirurgischen Eingriffs wurde ein Silikon-Katheder im truncus lymphaticus jejunalis implantiert. Zusätzlich wurde ein zweiter Katheter in die hintere vena cava in Richtung Herz eingesetzt. Beide Katheter wurden sofort miteinander verbunden, um die Wiedereinführung der jejunalen Lymphe in den Blutkreislauf zu gewährleisten. Der negative Druck in der hinteren vena cava im Thoraxteil förderte den Lymphfluß durch das Katheter im truncus lymphaticus jejunalis. Der preprandiale Lymphfluß des Jéjunums betrug bei Schweinen 0,3 ml/h/kg Körpergewicht und stieg postprandial auf 0,78 ml/h/kg an. Beim Schaf betrug der Basiswert 0,75 ml/h/kg. Er stieg nach intraduodenaler Infusion von Rapsöl auf 4,75 ml/h/kg. Eine mechanische Stimulation der intestinalen Receptoren durch 0,9% NaCl-Lösung stimulierte ebenfalls den Lymphfluß. 相似文献