全文获取类型
收费全文 | 17965篇 |
免费 | 159篇 |
国内免费 | 35篇 |
专业分类
林业 | 3737篇 |
农学 | 1350篇 |
基础科学 | 139篇 |
2999篇 | |
综合类 | 889篇 |
农作物 | 2187篇 |
水产渔业 | 1875篇 |
畜牧兽医 | 1798篇 |
园艺 | 1132篇 |
植物保护 | 2053篇 |
出版年
2023年 | 9篇 |
2022年 | 11篇 |
2021年 | 25篇 |
2020年 | 38篇 |
2019年 | 23篇 |
2018年 | 2779篇 |
2017年 | 2740篇 |
2016年 | 1243篇 |
2015年 | 120篇 |
2014年 | 83篇 |
2013年 | 116篇 |
2012年 | 904篇 |
2011年 | 2245篇 |
2010年 | 2158篇 |
2009年 | 1295篇 |
2008年 | 1411篇 |
2007年 | 1658篇 |
2006年 | 125篇 |
2005年 | 188篇 |
2004年 | 172篇 |
2003年 | 222篇 |
2002年 | 132篇 |
2001年 | 55篇 |
2000年 | 78篇 |
1999年 | 32篇 |
1998年 | 22篇 |
1997年 | 9篇 |
1996年 | 5篇 |
1995年 | 13篇 |
1994年 | 10篇 |
1993年 | 18篇 |
1992年 | 25篇 |
1991年 | 7篇 |
1990年 | 11篇 |
1989年 | 18篇 |
1988年 | 22篇 |
1987年 | 14篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1975年 | 4篇 |
1973年 | 4篇 |
1972年 | 5篇 |
1969年 | 10篇 |
1968年 | 8篇 |
1961年 | 6篇 |
1960年 | 4篇 |
1958年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
猪肺炎支原体黏附因子基因R1R2区的克隆及表达 总被引:4,自引:0,他引:4
根据GenBank登录的猪肺炎支原体232株P97基因和J株黏附因子基因设计了1对引物,以我国猪肺炎支原体Z株(强毒株)基因组DNA为模板,通过PCR方法扩增了该株黏附因子基因的部分序列。经序列分析后,重新设计了1对带有EcoRI和HindⅢ酶切位点的引物,并经引物的定点突变,PCR扩增了Z株黏附因子的R1R2区。扩增产物经双酶切后克隆到表达载体pET-32(a) 中。该重组质粒经酶切鉴定后,将其具有正确阅读框架的重组质粒转化到大肠杆菌BL21(DE3)感受态细胞,37℃下经IPTG诱导表达,得到相对分子质量约29000的融合蛋白,表达量约为11%。 相似文献
4.
5.
6.
Evaluation of a Killed Vaccine Against Porcine Pleuropneumonia Due to Haemophilus pleuropneumoniae 总被引:20,自引:2,他引:18
Higgins R Larivière S Mittal KR Martineau GP Rousseau P Cameron J 《The Canadian veterinary journal. La revue veterinaire canadienne》1985,26(2):86-89
A bacterin containing serotypes 1 and 5 of Haemophilus pleuropneumoniae was developed for the prevention and the control of porcine pleuropneumonia. It was injected intramuscularly into three groups of ten piglets, the first group with one dose, the second one with two doses and the third one with three doses at two-week intervals. Another group of ten piglets did not receive the vaccine. All the piglets were then challenged by an aerosol of mixed suspensions of H. pleuropneumoniae serotypes 1 and 5. Two and three injections of vaccine completely prevented mortality, whereas half of the control piglets and of those receiving only one dose of vaccine died. All surviving piglets, both control and vaccinated, had severe signs of respiratory disease for at least 36 hours after exposure to challenge. Moreover, vaccination did not induce the production of antibodies at high titers. Local reactions were not noted after vaccination and at postmortem; ten weeks after the challenge, there were no signs of abscess formation or induration. 相似文献
7.
8.
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
9.
10.