首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   83910篇
  免费   4688篇
  国内免费   56篇
林业   2918篇
农学   2320篇
基础科学   563篇
  9184篇
综合类   14871篇
农作物   3081篇
水产渔业   3929篇
畜牧兽医   45824篇
园艺   881篇
植物保护   5083篇
  2018年   1032篇
  2017年   1170篇
  2016年   1085篇
  2015年   935篇
  2014年   1172篇
  2013年   3055篇
  2012年   2119篇
  2011年   2703篇
  2010年   1656篇
  2009年   1768篇
  2008年   2594篇
  2007年   2407篇
  2006年   2412篇
  2005年   2131篇
  2004年   2088篇
  2003年   2077篇
  2002年   1969篇
  2001年   2700篇
  2000年   2803篇
  1999年   2134篇
  1998年   823篇
  1997年   831篇
  1996年   815篇
  1995年   1029篇
  1994年   898篇
  1993年   856篇
  1992年   1947篇
  1991年   2091篇
  1990年   1934篇
  1989年   1936篇
  1988年   1828篇
  1987年   1935篇
  1986年   1986篇
  1985年   1883篇
  1984年   1489篇
  1983年   1301篇
  1982年   882篇
  1979年   1373篇
  1978年   1125篇
  1977年   976篇
  1976年   942篇
  1975年   988篇
  1974年   1275篇
  1973年   1298篇
  1972年   1237篇
  1971年   1154篇
  1970年   1097篇
  1969年   964篇
  1968年   832篇
  1967年   869篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
Humoral immune responses of black-footed penguins (Spheniscus demersus) to DNA-mediated immunization with a beta-galactosidase reporter gene expression plasmid were evaluated. Six male and 6 female adult penguins received either test plasmid, pCMV-beta, containing the beta-galactosidase gene or control plasmid, pCI, lacking a gene for expression. Three birds from each group were used previously in a diluent control group and given one injection of sterile saline. All samples were screened for anti-beta-galactosidase antibodies by indirect enzyme-linked immunosorbent assay with anti-chicken immunoglobulin G as secondary antibody. Antibodies to beta-galactosidase were detected in the sera of pCMV-beta-inoculated penguins, with a peak response on day 21. Antibody titers of the test plasmid group versus both control groups on days 21, 28, and 42 differed significantly. These results demonstrate that black-footed penguins can be safely transfected with the gene encoding beta-galactosidase and will mount a humoral response against the in vivo-expressed protein. Knowledge from this initial study can be applied to the development of DNA-mediated vaccines against specific infectious diseases of penguins.  相似文献   
83.
84.
85.
The effect of Harderian adenectomy on the antibody response in chickens   总被引:2,自引:0,他引:2  
Intact chicks and those that had their glands of Harder (GH) removed (GHx) at 1 day of age were studied for their response to optically or intraperitoneally (IP) applied antigens. Following exposure of the chicks to sheep red blood cells (SRBCs), killed Brucella abortus, or bovine serum albumin (BSA), serum and tear samples were collected and assayed for antibodies. Of the two sources of antibodies, the serum generally had higher levels than did the tears. The only exception to this occurred in the intact chicks inoculated by the eye, in which serum and tear levels were equivalent. With SRBCs, no difference could be detected between the two routes of inoculation. However, IP inoculation produced higher levels of antibody in the serum of intact and GHx chicks inoculated with B. abortus or BSA and in the tears of the GHx chicks exposed to B. abortus. Removal of the GH resulted in a consistent decrease in antibody levels in the tears, regardless of the route of exposure. Although this effect was noted with all three antigens, it was more pronounced in the trials using B. abortus and BSA. This finding is discussed in terms of describing the importance of the GH as a source of antibodies to optically applied antigens, and its importance as a route of circulating antibody egress. Furthermore, the feasibility of using the antibody response in tears to a test antigen is discussed as a means of measuring the immune status of a functioning GH.  相似文献   
86.
87.
88.
89.
90.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号