全文获取类型
收费全文 | 889篇 |
免费 | 62篇 |
专业分类
林业 | 42篇 |
农学 | 12篇 |
基础科学 | 3篇 |
212篇 | |
综合类 | 60篇 |
农作物 | 44篇 |
水产渔业 | 59篇 |
畜牧兽医 | 400篇 |
园艺 | 44篇 |
植物保护 | 75篇 |
出版年
2023年 | 15篇 |
2022年 | 16篇 |
2021年 | 23篇 |
2020年 | 37篇 |
2019年 | 34篇 |
2018年 | 37篇 |
2017年 | 36篇 |
2016年 | 43篇 |
2015年 | 22篇 |
2014年 | 32篇 |
2013年 | 56篇 |
2012年 | 60篇 |
2011年 | 79篇 |
2010年 | 51篇 |
2009年 | 31篇 |
2008年 | 58篇 |
2007年 | 73篇 |
2006年 | 52篇 |
2005年 | 48篇 |
2004年 | 35篇 |
2003年 | 32篇 |
2002年 | 29篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 3篇 |
排序方式: 共有951条查询结果,搜索用时 265 毫秒
71.
Wing SL Harrington GJ Smith FA Bloch JI Boyer DM Freeman KH 《Science (New York, N.Y.)》2005,310(5750):993-996
Rapid global warming of 5 degrees to 10 degrees C during the Paleocene-Eocene Thermal Maximum (PETM) coincided with major turnover in vertebrate faunas, but previous studies have found little floral change. Plant fossils discovered in Wyoming, United States, show that PETM floras were a mixture of native and migrant lineages and that plant range shifts were large and rapid (occurring within 10,000 years). Floral composition and leaf shape and size suggest that climate warmed by approximately 5 degrees C during the PETM and that precipitation was low early in the event and increased later. Floral response to warming and/or increased atmospheric CO2 during the PETM was comparable in rate and magnitude to that seen in postglacial floras and to the predicted effects of anthropogenic carbon release and climate change on future vegetation. 相似文献
72.
Rota A Pregel P Cannizzo FT Sereno A Appino S 《Journal of Feline Medicine and Surgery》2011,13(6):448-450
This report describes an unusual case of uterine stump pyometra in a cat whose main clinical sign at presentation was abdominal straining. At the time of ovariohysterectomy, the surgeon reported that the uterine body had a purulent content. Nearly a month after the surgery the cat showed abdominal straining. The enlarged uterine stump, filled with purulent fluid, had caused a compression of the rectum and secondary intestinal sub-occlusion. Surgical revision consisted of draining the purulent content of the remnant of the uterine body and ablating as much of it as possible; checking of the ovarian pedicles revealed the presence of a small fragment of whitish tissue on the right side, which was shown to contain, by means of histological observation and immunohistochemical staining, ovarian tissue. Four months after surgical revision the queen did not show any pathological signs and 1 year later she is still in good health. 相似文献
73.
Giuliano Pisoni Patrizia D’Amelio Francesca Sassi Giovanni Manarolla Licia Scaccabarozzi Clara Locatelli Nausicaa Mazzocchi Mirko Baruscotti Dario DiFrancesco Paolo Moroni 《Veterinary journal (London, England : 1997)》2011,189(3):361-363
Formation of multinucleated giant cells (MGCs) by macrophage fusion is a typical cytopathic effect of lentiviral replication in caprine monocytes and MGC formation from cultured caprine peripheral blood mononuclear cells (PBMCs) has been considered to be diagnostic for small ruminant lentivirus (SRLV) infection. In this study, formation of MGCs was observed after 7–14 days when PBMCs were cultured from healthy goats free from SRLV infection. These MGCs expressed tartrate-resistant acid phosphatase, calcitonin receptor, integrin αVβ3, cathepsin K and matrix metalloproteinase 9 and were able to resorb bone in vitro in the absence of RANKL and macrophage colony stimulating factor, consistent with an osteoclast phenotype. 相似文献
74.
D'aes J Hua GK De Maeyer K Pannecoucque J Forrez I Ongena M Dietrich LE Thomashow LS Mavrodi DV Höfte M 《Phytopathology》2011,101(8):996-1004
Pseudomonas CMR12a was previously selected as an efficient biocontrol strain producing phenazines and cyclic lipopeptides (CLPs). In this study, biocontrol capacity of Pseudomonas CMR12a against Rhizoctonia root rot of bean and the involvement of phenazines and CLPs in this ability were tested. Two different anastomosis groups (AGs) of Rhizoctonia solani, the intermediately aggressive AG 2-2 and the highly aggressive AG 4 HGI, were included in growth-chamber experiments with bean plants. The wild-type strain CMR12a dramatically reduced disease severity caused by both R. solani AGs. A CLP-deficient and a phenazine-deficient mutant of CMR12a still protected bean plants, albeit to a lesser extent compared with the wild type. Two mutants deficient in both phenazine and CLP production completely lost their biocontrol activity. Disease-suppressive capacity of CMR12a decreased after washing bacteria before application to soil and thereby removing metabolites produced during growth on plate. In addition, microscopic observations revealed pronounced branching of hyphal tips of both R. solani AGs in the presence of CMR12a. More branched and denser mycelium was also observed for the phenazine-deficient mutant; however, neither the CLP-deficient mutant nor the mutants deficient in both CLPs and phenazines influenced hyphal growth. Together, results demonstrate the involvement of phenazines and CLPs during Pseudomonas CMR12a-mediated biocontrol of Rhizoctonia root rot of bean. 相似文献
75.
Sandra?N.?CatlinEmail author Peter?Guttorp Monica?T.?McCallie Janis?L.?Abkowitz 《Journal of Agricultural, Biological & Environmental Statistics》2004,9(2):216-235
Female Safari cats are offspring of domestic and Geoffroy parents, and are balanced heterozygotes with equal numbers of Blood cells containing domestic and Geoffroy-type glucose 6-phosphate dehydrogenase (G6PD),an X-chromosome derived enzyme. In previous
studies, however, we observed increasing percentages of Blood cells with Geoffroy G6PD in cats aged 4–12 years. Similarly, ratios of parental X-chromosome phenotypes greater than three
to one are common in women over age 60, while women under 40 typically exhibit one to one ratios. Using a two-compartment
hidden-Markov model of the distribution of phenotype in samples taken during the second stage of hematopoiesis (Blood cell production), we estimate, through simulation and mathematical calculation, the Geoffroy selective advantages necessary
to reproduce the data obtained from female Safari cats. It is shown that small differences in the kinetics of hematopoietic
stem cells (HSC), less than might be detected by in vitro assays, can explain the “clonal dominance” observed with aging in
cats, and by extension, human females. Conceptually, hematopoiesis in females can be viewed as a competitive exclusion process
in which two populations of HSC (defined by parental X-chromosome phenotype) compete for environmental resources. As in many
ecological examples, dominance may occur only after long periods of time. 相似文献
76.
77.
Borrelli RC Visconti A Mennella C Anese M Fogliano V 《Journal of agricultural and food chemistry》2002,50(22):6527-6533
Melanoidins, the brown polymers formed through Maillard reaction during coffee roasting, constitute up to 25% of the coffee beverages' dry matter. In this study chemical characterization of melanoidins obtained from light-, medium-, and dark-roasted coffee beans, manufactured from the same starting material, was performed. Melanoidins were separated by gel filtration chromatography and studied by MALDI-TOF mass spectrometry. Results showed that the amount of melanoidins present in the brews increased as the intensity of the thermal treatment increased, while their molecular weight decreased. The antioxidant activity of melanoidins isolated from the different brews was studied by using different methodologies. Melanoidins antiradical activity determined by ABTS(*)(+) and DMPD(*)(+) assays decreased as the intensity of roasting increased, but the ability to prevent linoleic acid peroxidation was higher in the dark-roasted samples. Data suggest that melanoidins must be carefully considered when the relevance of coffee intake in human health is studied. 相似文献
78.
Olive oil fluorescence is related to oil composition. Here it is shown that the natural clustering of different types of commercial Spanish olive oils depends on their fluorescence excitation-emission matrices (EEMs). Fifty-six commercial samples of olive oil (29 virgin olive oils, 20 pure olive oils, and 7 olive-pomace oils) were used. The clustering method was hierarchical agglomerative clustering using the Euclidean distance as a similarity measure and the average linkage. Two spectral ranges were considered (which either contained the fluorescence peak of the chlorophylls or did not), and various methods for preprocessing the fluorescence spectra were compared. The oils were clearly distinguished using the unfolded EEMs measured between lambda(ex) = 300-400 nm and lambda(em) = 400-600 nm. The optimal preprocessing was normalization of the unfolded spectra followed by column autoscaling. Also shown are the advantages of using second-order data (EEMs) instead of first-order data (a single fluorescence spectrum) for each sample. 相似文献
79.
Bicanic D Swarts J Luterotti S Helander P Fogliano V Anese M 《Journal of agricultural and food chemistry》2005,53(9):3295-3299
This study reports on the first use of the "optothermistor" as a novel, precise, fast, and low-cost detector of lycopene in a wide range of commercially available processed-tomato products. The quantitative performance of the new device was evaluated by comparing data obtained to that acquired by conventional methods, namely, absorption spectrophotometry and high-performance liquid chromatography (HPLC); the linear correlation was high (R = 0.98). The variation of data obtained with the optothermistor in a series of consecutive measurements performed with the same loading of the sample was better than 1%. However, the repeatability (RSD 0.5-9.0%, n = 3-5) achieved with the optothermistor by independent analyses (multiple loading) is comparable to that of HPLC and spectrophotometry. Results of the studies performed on the 19 products derived from tomatoes demonstrated that the optothermistor is suitable for selective, accurate, precise, and simple determination of lycopene (range = 7-75 mg/100 g of product weight) without the need for a sample pretreatment step. The estimated sensitivity of the present optothermistor is 2 mg of lycopene/100 g of product. 相似文献
80.
Laura Volterra Lucia Bonadonna Francesca Anna Aulicino 《Water, air, and soil pollution》1986,29(4):403-413
The usual media and procedures were followed to measure the concentration of fecal streptococci (MPN on Azide Dextrose and Ethyl Violet Azide broths, membrane filtration on m-Enterococcus, KF and Pfizer Selective Enterococcus agars and according to the mE procedure) in samples collected along two different marine areas. The results were evaluated on the basis of three parameters: total concentrations, number of enterococci-like colonies (namely colonies gram positive, catalase negative, coccus shaped) and rate of strictly named fecal streptococci. From the results it appears that the various media and procedures employed gave different yields and their capacity to measure fecal streptococci varies according to the origin of samples. The accompanying bacterial flora may play an important role on the selectivity of each technique to measure the fecal streptococci. 相似文献