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   113914篇
  免费   6422篇
  国内免费   360篇
林业   4251篇
农学   3483篇
基础科学   843篇
  13766篇
综合类   19511篇
农作物   4356篇
水产渔业   5389篇
畜牧兽医   60609篇
园艺   1264篇
植物保护   7224篇
  2018年   1646篇
  2017年   1834篇
  2016年   1672篇
  2015年   1447篇
  2014年   1803篇
  2013年   4521篇
  2012年   3136篇
  2011年   3849篇
  2010年   2506篇
  2009年   2638篇
  2008年   3716篇
  2007年   3442篇
  2006年   3333篇
  2005年   2959篇
  2004年   2862篇
  2003年   2859篇
  2002年   2693篇
  2001年   3657篇
  2000年   3682篇
  1999年   2825篇
  1998年   1133篇
  1997年   1154篇
  1996年   1082篇
  1995年   1322篇
  1994年   1153篇
  1993年   1076篇
  1992年   2452篇
  1991年   2691篇
  1990年   2441篇
  1989年   2497篇
  1988年   2318篇
  1987年   2390篇
  1986年   2467篇
  1985年   2307篇
  1984年   1853篇
  1983年   1608篇
  1982年   1090篇
  1979年   1808篇
  1978年   1461篇
  1977年   1249篇
  1976年   1255篇
  1975年   1314篇
  1974年   1661篇
  1973年   1681篇
  1972年   1600篇
  1971年   1414篇
  1970年   1384篇
  1969年   1303篇
  1968年   1136篇
  1967年   1167篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The records of 71 horses with small intestinal disorders requiring surgical correction were disorders requiring surgical correction were reviewed to compare the prevalence of laminitis in those horses treated prophylactically with heparin and the prevalence of horses not treated with heparin. The prevalence of laminitis was 13% (9/71), and there was no significant difference (P less than 0.05) in the prevalence of laminitis between the 2 groups. The lack of significant benefit after treatment with heparin indicates that further work needs to be done on the equine coagulation system before heparin can be advocated for prevention of laminitis.  相似文献   
102.
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   
103.
Abstract. Experiments were started in 1967 to investigate the effects of soil mixing on fen peat soil. Peaty topsoil was mixed with mineral subsoil to a maximum depth of 80 cm at two sites, one with a clay subsoil, the other sand. Mixing was done on a commercial scale with a range of implements. After initial increases, yields of arable crops on both mixed soils were subsequently similar to those on unmixed soil. Residual herbicide activity was enhanced on mixed soils, and evidence of peat conservation was obtained at one site. The practice has not been taken up commercially because of the high capital cost of mixing and lack of serious problems which had been predicted following peat wastage.  相似文献   
104.
105.
106.
107.
108.
109.
110.
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