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   74418篇
  免费   4254篇
  国内免费   47篇
林业   3416篇
农学   2732篇
基础科学   518篇
  9302篇
综合类   11721篇
农作物   2754篇
水产渔业   3799篇
畜牧兽医   38338篇
园艺   997篇
植物保护   5142篇
  2018年   1125篇
  2017年   1214篇
  2016年   1120篇
  2015年   953篇
  2014年   1203篇
  2013年   2775篇
  2012年   2199篇
  2011年   2649篇
  2010年   1825篇
  2009年   1883篇
  2008年   2766篇
  2007年   2506篇
  2006年   2461篇
  2005年   2255篇
  2004年   2313篇
  2003年   2293篇
  2002年   2168篇
  2001年   2471篇
  2000年   2477篇
  1999年   2007篇
  1998年   953篇
  1997年   844篇
  1996年   819篇
  1995年   896篇
  1994年   883篇
  1993年   816篇
  1992年   1589篇
  1991年   1602篇
  1990年   1732篇
  1989年   1558篇
  1988年   1482篇
  1987年   1386篇
  1986年   1422篇
  1985年   1382篇
  1984年   1170篇
  1983年   1060篇
  1982年   677篇
  1979年   1037篇
  1978年   829篇
  1977年   749篇
  1976年   708篇
  1975年   747篇
  1974年   803篇
  1973年   853篇
  1972年   831篇
  1971年   776篇
  1970年   756篇
  1969年   781篇
  1967年   684篇
  1966年   656篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
31.
Summary Acute febrile diseases are characterized by specific and non-specific symptoms. The non-specific responses are presented under the headings: fever, inflammation and pain, experimental models for investigating febrile reactions, haematologic changes, blood biochemical changes, cardiovascular effects, changes in gastric function, and the effects of fever upon pharmacokinetics of drugs. It was the purpose of this review to describe present concepts of thermoregulation and fever, the associated reactions produced by bacterial pyrogens and the mechanisms of these reactions. The available data illustrate, that many questions have not yet been clearly answered. However, the entire field of research involving endogenous substances, such as interleukin-1, is now moving ahead with great speed. Furthermore, there is some evidence which suggests that fever and the associated lower plasma zinc and iron levels act together as a co-ordinated non-specific host defence mechanism. Since experimental fever has a distinct effect upon the pharmacokinetics of drugs, more attention should be given to this aspect.  相似文献   
32.
33.
34.
35.
36.
37.
38.
39.
40.
Observations on transplacental infection with bluetongue virus in sheep   总被引:1,自引:0,他引:1  
Twenty-four ewes were inoculated with 1 of 2 strains of bluetongue virus type 4 at 40, 60, or 80 days of gestation. Two ewes aborted, 2 ewes died, and 1 was killed during the experiment, but their fetuses were recovered. At term, 2 mummified fetuses, 4 dead lambs, and 17 clinically healthy lambs were produced by 12 sheep, and the remaining 7 sheep were barren. Porencephaly and cerebellar dysgenesis were found in term lambs born to sheep inoculated at 40 and 60 days of gestation. Radiographic examination of 12 fetuses showed developmental ages far less than their chronologic age; 8 fetuses had skeletal growth-retardation lines, which were also observed in the dead lambs. A systemic lymphoreticular hyperplasia was observed in the dead lambs and in all lambs at 12 weeks of age; in 4 of the latter, granulomatous reactions were present in the liver and kidney. Lungs of the full-term lambs were reduced in weight and showed poor alveolar development and mononuclear cell infiltration, which persisted in the 12-week-old lambs. It was concluded that bluetongue virus is capable of causing not only gross abnormalities of the CNS, but also generalized growth retardation and fetal lymphoreticular hyperplasia.  相似文献   
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