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   113524篇
  免费   6209篇
  国内免费   45篇
林业   7812篇
农学   4944篇
基础科学   786篇
  15580篇
综合类   14526篇
农作物   5660篇
水产渔业   7352篇
畜牧兽医   52631篇
园艺   2287篇
植物保护   8200篇
  2021年   828篇
  2020年   920篇
  2019年   1095篇
  2018年   4368篇
  2017年   4619篇
  2016年   3109篇
  2015年   1761篇
  2014年   2093篇
  2013年   4237篇
  2012年   4261篇
  2011年   6077篇
  2010年   4534篇
  2009年   3707篇
  2008年   5079篇
  2007年   5066篇
  2006年   3516篇
  2005年   3122篇
  2004年   2971篇
  2003年   3037篇
  2002年   2679篇
  2001年   3574篇
  2000年   3519篇
  1999年   2693篇
  1998年   1020篇
  1997年   1076篇
  1996年   927篇
  1995年   1045篇
  1994年   916篇
  1993年   927篇
  1992年   1965篇
  1991年   2014篇
  1990年   1949篇
  1989年   1967篇
  1988年   1726篇
  1987年   1699篇
  1986年   1729篇
  1985年   1619篇
  1984年   1293篇
  1983年   1100篇
  1982年   757篇
  1979年   1153篇
  1978年   891篇
  1975年   854篇
  1974年   980篇
  1973年   931篇
  1972年   896篇
  1971年   874篇
  1970年   824篇
  1969年   808篇
  1967年   763篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
51.
52.
53.
54.
55.
56.
57.
58.
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   
59.
60.
Estrogen and progesterone receptors (ER, PR) were measured in cytosol fractions from 18 primary canine mammary carcinomas by use of biochemical assays. One or both receptors were detected (> 10 fmol/mg of cytosol protein) in 11 tumors: 5 ER and PR; 2 ER only; 4 PR only. Mean cytoplasmic receptor concentrations (fmol/mg of cytosol protein) were 22.8 +/- 2.9 (SEM) for ER and 51.0 +/- 10.3 for PR in tumors containing ER and PR, 28.8 +/- 12.1 for ER in tumors containing only ER and 13.2 +/- 1.5 for PR in tumors containing only PR. Estrogen or progesterone receptors or both were identified in 6 of 9 tubular adenocarcinomas, 4 of 5 papillary adenocarcinomas, and 1 of 1 squamous cell carcinoma. These receptors were not identified in solid carcinomas (n = 2) or a single spindle cell carcinoma. Although the number of cases was limited, survival times of dogs tended to be longest in those with tumors containing ER alone or in combination with PR, intermediate in those with tumors containing only PR, and shortest in those with tumors without ER or PR. A correlation was not apparent between receptor status and age, presence of ovaries, tumor size, or histologic classification of the tumor. In the analysis of this series, the extent of surgery (mastectomy of the involved gland vs unilateral or bilateral mastectomy) did not appear to influence the outcome of the disease, and metastasis to regional lymph nodes did not appear to be a reliable prognostic indicator.  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