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   136005篇
  免费   7350篇
  国内免费   84篇
林业   5184篇
农学   4035篇
基础科学   848篇
  14780篇
综合类   28213篇
农作物   5447篇
水产渔业   6157篇
畜牧兽医   68796篇
园艺   1620篇
植物保护   8359篇
  2018年   1572篇
  2017年   1781篇
  2016年   1689篇
  2015年   1468篇
  2014年   1759篇
  2013年   4846篇
  2012年   3428篇
  2011年   4077篇
  2010年   2663篇
  2009年   2601篇
  2008年   3965篇
  2007年   3840篇
  2006年   3715篇
  2005年   3571篇
  2004年   3331篇
  2003年   3484篇
  2002年   3302篇
  2001年   3914篇
  2000年   3821篇
  1999年   3118篇
  1998年   1378篇
  1997年   1302篇
  1995年   1412篇
  1994年   1325篇
  1993年   1271篇
  1992年   2758篇
  1991年   2845篇
  1990年   2841篇
  1989年   2969篇
  1988年   2668篇
  1987年   2725篇
  1986年   2812篇
  1985年   2715篇
  1984年   2225篇
  1983年   1959篇
  1982年   1435篇
  1981年   1294篇
  1979年   1998篇
  1978年   1643篇
  1977年   1454篇
  1976年   1337篇
  1975年   1515篇
  1974年   1919篇
  1973年   1901篇
  1972年   1918篇
  1971年   1836篇
  1970年   1722篇
  1969年   1542篇
  1968年   1219篇
  1967年   1382篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
45.
46.
47.
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   
48.
49.
Disseminated Aspergillus terreus infection was diagnosed in ten previously healthy adult dogs--nine German shepherds and one dalmatian. The disease was characterized by the presence of multiple granulomas and infarcts in a wide range of organs. The kidney, spleen, and skeletal system were most commonly and severely affected. Fungal hyphae were demonstrated in large numbers within granulomas and thrombi, and A. terreus was readily isolated by culture. This disseminated mycosis appears unique; in this series of cases there was no apparent predisposing factor, portal of entry, or primary focus for dissemination of the infection.  相似文献   
50.
1. White blood cell responses of broilers, turkeys and ducks were examined at regular intervals after being subjected to various degrees of food restriction. 2. Restricted-fed broilers showed increases in heterophil and basophil numbers, together with a corresponding decrease in lymphocytes. The heterophil/lymphocyte ratio was raised. There were no differences between broiler strains. 3. After only one week of feeding restricted diets, heterophils were significantly raised in selected and unselected 2-week-old ducks. At 21 weeks of age, those ducks receiving 50% of food required to achieve their ad libitum-fed body weight had raised heterophils. 4. Ducks receiving food to achieve 25% of ad libitum-fed birds produced a marked basophilia, but no heterophilia. 5. After two weeks of food restriction, turkeys responded with significant heterophil/lymphocyte ratios following two degrees of restricted feeding. 6. It was concluded that in some poultry, a heterophilia may be the response to mild to moderate stress but a basophilia may result after severely stressing birds.  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