全文获取类型
收费全文 | 17469篇 |
免费 | 78篇 |
专业分类
林业 | 3686篇 |
农学 | 1306篇 |
基础科学 | 141篇 |
2850篇 | |
综合类 | 905篇 |
农作物 | 2123篇 |
水产渔业 | 1830篇 |
畜牧兽医 | 1654篇 |
园艺 | 1124篇 |
植物保护 | 1928篇 |
出版年
2023年 | 11篇 |
2022年 | 10篇 |
2021年 | 25篇 |
2020年 | 18篇 |
2019年 | 28篇 |
2018年 | 2759篇 |
2017年 | 2723篇 |
2016年 | 1202篇 |
2015年 | 85篇 |
2014年 | 44篇 |
2013年 | 41篇 |
2012年 | 863篇 |
2011年 | 2182篇 |
2010年 | 2132篇 |
2009年 | 1297篇 |
2008年 | 1366篇 |
2007年 | 1642篇 |
2006年 | 90篇 |
2005年 | 144篇 |
2004年 | 138篇 |
2003年 | 180篇 |
2002年 | 90篇 |
2001年 | 21篇 |
2000年 | 62篇 |
1999年 | 18篇 |
1998年 | 14篇 |
1997年 | 12篇 |
1993年 | 16篇 |
1992年 | 13篇 |
1991年 | 18篇 |
1990年 | 20篇 |
1989年 | 18篇 |
1988年 | 17篇 |
1987年 | 22篇 |
1986年 | 15篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1974年 | 7篇 |
1971年 | 9篇 |
1970年 | 7篇 |
1969年 | 7篇 |
1968年 | 9篇 |
1967年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
3.
Samuel Jakovljevic DVM MSc DVR Nicole MacLaren DVM 《Veterinary radiology & ultrasound》1995,36(5):457-457
4.
5.
The T.M.E. System of Feed Evaluation. I.R. Sibbald, Animal Research Centre Contribution 83‐1, Animal Research Centre, Ottawa, Ontario, Canada.
Physiology and Behaviour of the Pigeon, edited by M. Abs. 1983. 360 pages, illustrated. London, Academic Press Ltd. Price £34.00. ISBN 0 12 042950 0. 相似文献
6.
7.
8.
1. The amino acid composition of the whole body protein of 28‐ and 56‐d‐old turkeys is reported.
2. There were some differences between the two ages; these could largely be reconciled by considering the likely differences in the proportion of feather protein.
3. The results were compared with similar values for the chicken and goose; overall there is a striking similarity, both in absolute concentrations and relative proportions of amino acids. 相似文献
9.
The systemic fungicides furalaxyl, metalaxyl and ofurace, 1 Ofurace is the proposed BSI and ISO common name for α-(2-chloro-N-2,6-xylylacetamido)-γ-butyrolactone. used to control diseases caused by phycomycetes, were extremely active in vitro against Pythium ultimum, Phytophthora nicotianae and Phytophthora palmivora. Sporangia production was reduced more than mycelial growth but germination of sporangia and zoospores was relatively unaffected. Less than 1% of the metalaxyl or furalaxyl, present in media at the ED50 for hyphal growth, was firmly absorbed by Phyt. palmivora mycelium; uptake was against a concentration gradient and was characterised by a rapid accumulation followed by a more gradual release. Respiration and wall synthesis were not inhibited, whilst membrane permeability was unaffected. Lipid patterns were altered but these changes were probably of secondary importance. The fungicides inhibited protein and nucleic acid synthesis; RNA production was particularly affected. There was some evidence of a reduction in nuclear division. The primary effect of furalaxyl and metalaxyl probably involves impaired biosynthesis of RNA so that mitosis is inhibited; ofurace may act in the same way. 相似文献
10.
A. Schots J. De Boer A. Schouten J. Roosien J. F. Zil Verentant H. Pomp L. Bouwman-Smits H. Overmars F. J. Gommers B. Visser W. J. Stiekema J. Bakker 《European journal of plant pathology / European Foundation for Plant Pathology》1992,98(2):183-191
Engineering resistance against various diseases and pests is hampered by the lack of suitable genes. To overcome this problem we started a research program aimed at obtaining resistance by transfecting plants with genes encoding monoclonal antibodies against pathogen specific proteins. The idea is that monoclonal antibodies will inhibit the biological activity of molecules that are essential for the pathogenesis. Potato cyst nematodes are chosen as a model and it is thought that monoclonal antibodies are able to block the function of the saliva proteins of this parasite. These proteins are, among others, responsible for the induction of multinucleate transfer cells upon which the nematode feeds. It is well documented that the ability of antibodies to bind molecules is sufficient to inactivate the function of an antigen and in view of the potential of animals to synthesize antibodies to almost any molecular structure, this strategy should be feasible for a wide range of diseases and pests.Antibodies have several desirable features with regard to protein engineering. The antibody (IgG) is a Y-shaped molecule, in which the domains forming the tips of the arms bind to antigen and those forming the stem are responsible for triggering effector functions (Fc fragments) that eliminate the antigen from the animal. Domains carrying the antigen-binding loops (Fv and Fab fragments) can be used separately from the Fc fragments without loss of affinity. The antigen-binding domains can also be endowed with new properties by fusing them to toxins or enzymes. Antibody engineering is also facilitated by the Polymerase Chain Reaction (PCR). A systematic comparison of the nucleotide sequence of more than 100 antibodies revealed that not only the 3′-ends, but also the 5′-ends of the antibody genes are relatively conserved. We were able to design a small set of primers with restriction sites for forced cloning, which allowed the amplification of genes encoding antibodies specific for the saliva proteins ofGlobodera rostochiensis. Complete heavy and light chain genes as well as single chain Fv fragments (scFv), in which the variable parts of the light (VL) and heavy chain (VH) are linked by a peptide, will be transferred to potato plants. A major challenge will be to establish a correct expression of the antibody genes with regard to three dimensional folding, assembly and intracellular location. 相似文献