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   192848篇
  免费   10372篇
  国内免费   151篇
林业   9798篇
农学   6543篇
基础科学   1270篇
  25547篇
综合类   31106篇
农作物   7771篇
水产渔业   9711篇
畜牧兽医   95225篇
园艺   3040篇
植物保护   13360篇
  2019年   1801篇
  2018年   3513篇
  2017年   3856篇
  2016年   3209篇
  2015年   2474篇
  2014年   3064篇
  2013年   7511篇
  2012年   5792篇
  2011年   7492篇
  2010年   5144篇
  2009年   5080篇
  2008年   7101篇
  2007年   6925篇
  2006年   5865篇
  2005年   5571篇
  2004年   5256篇
  2003年   5524篇
  2002年   4992篇
  2001年   5711篇
  2000年   5670篇
  1999年   4533篇
  1998年   1985篇
  1997年   1939篇
  1996年   1783篇
  1995年   2175篇
  1994年   1878篇
  1993年   1772篇
  1992年   3590篇
  1991年   3816篇
  1990年   3704篇
  1989年   3746篇
  1988年   3444篇
  1987年   3368篇
  1986年   3512篇
  1985年   3376篇
  1984年   2814篇
  1983年   2463篇
  1982年   1713篇
  1979年   2608篇
  1978年   2055篇
  1977年   1820篇
  1976年   1811篇
  1975年   1923篇
  1974年   2293篇
  1973年   2338篇
  1972年   2201篇
  1971年   2083篇
  1970年   1984篇
  1969年   1962篇
  1967年   1782篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Twelve isolates of bovine rotavirus, originating from eight dairy herds in Quebec known to have frequent epizootics of diarrhea in young calves in the last five years, were successfully propagated in cell cultures. The 12 isolates produced clear-cut plaques in BSC-1 cells and, except for one isolate, agglutinated human group "O" erythrocytes to an higher titer than bovine erythrocytes. Antisera to each isolate were produced in rabbits and used to study their antigenic relationships. All the isolates shared the group-specific immunofluorescent antigen and were antigenically related as demonstrated by the seroneutralization and hemagglutination-inhibition tests. However, the relationships to the Nebraska rotavirus was quite weak in cases of two Quebec isolates. When the genomes of the various isolates were compared by polyacrylamide gel electrophoresis, at least three different reproducible fractionation patterns could be identified.  相似文献   
992.
Generally accepted criteria were used to identify typical nucleated thrombocytes and typical small lymphocytes in chicken-blood smears subjected to modified-Wright staining. Other cells, here referred to as "intermediate cells," were difficult to classify because in some aspects they resembled thrombocytes while they also had features typical of small lymphocytes. The "intermediate cells" had small, round or oval nuclei with coarsely condensed chromatin, characteristic of both thrombocytes and small lymphocytes. In addition, "intermediate cells" had moderately abundant cytoplasmic volumes, typical of thrombocytes but blue cytoplasm lacking both granules and vacuoles, which is characteristic of small lymphocytes. It made little difference to the thrombocyte count whether these cells were classified as thrombocytes or small lymphocytes; however, this decision made a substantial difference to the lymphocyte count in some chicken-blood smears. Most "intermediate cells" (351 of 410 cells examined) were nonfluorescent after treatment with formaldehyde gas. Furthermore, most "intermediate cells" failed to acquire characteristic pigments when subjected to either Grimelius staining (179 of 204 cells examined) or periodic acid-Schiff staining (173 of 206 cells examined). Typical small lymphocytes reacted in the same way, failing to fluoresce after gaseous formaldehyde treatment (65 of 65 cells examined) and failing to react during Grimelius staining (41 of 44 cells examined) or periodic acid-Schiff staining (21 of 21 cells examined). In contrast, almost all typical thrombocytes became fluorescent in response to gaseous formaldehyde (709 of 718 cells examined) and gave positive reactions when subjected to Grimelius staining (381 of 382 cells examined) or periodic acid-Schiff staining (322 of 326 cells examined). These findings suggested that "intermediate cells" should be classified as lymphocytes in differential cell counts.  相似文献   
993.
994.
995.
996.
997.
998.
999.
1000.
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