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   1352篇
  免费   73篇
  国内免费   1篇
林业   28篇
农学   24篇
基础科学   2篇
  79篇
综合类   297篇
农作物   45篇
水产渔业   48篇
畜牧兽医   820篇
园艺   16篇
植物保护   67篇
  2021年   15篇
  2020年   11篇
  2019年   18篇
  2018年   19篇
  2017年   13篇
  2016年   16篇
  2015年   20篇
  2014年   21篇
  2013年   34篇
  2012年   59篇
  2011年   62篇
  2010年   27篇
  2009年   27篇
  2008年   52篇
  2007年   56篇
  2006年   33篇
  2005年   33篇
  2004年   40篇
  2003年   41篇
  2002年   48篇
  2001年   35篇
  2000年   48篇
  1999年   44篇
  1997年   11篇
  1996年   14篇
  1993年   14篇
  1992年   22篇
  1991年   23篇
  1990年   36篇
  1989年   32篇
  1988年   16篇
  1987年   22篇
  1986年   24篇
  1985年   22篇
  1984年   22篇
  1983年   22篇
  1982年   11篇
  1981年   10篇
  1980年   10篇
  1979年   12篇
  1978年   14篇
  1977年   12篇
  1975年   12篇
  1974年   26篇
  1973年   20篇
  1972年   26篇
  1971年   17篇
  1970年   16篇
  1969年   10篇
  1966年   11篇
排序方式: 共有1426条查询结果,搜索用时 15 毫秒
991.
992.
Highlights of a first effort in sorting out rare gases in lunar material are solar wind rare gases in abundance; variable (20)Ne/(22)Ne but constant (21)Ne/ (22)Ne ratios in fractions of the trapped neon; cosmogenic rare gases similar to those found in meteorites, except for copious (131)Xe in one rock but not in another; at Tranquillity Base a rock 4.1 x 10(9) years old which reached the surface 35 to 65 million years ago, amid soil whose particles have typically been within a meter of the surface for 10(9) years or more.  相似文献   
993.
994.
Background: Chronic pancreatitis (CP) is common in dogs. The cause is unknown. In humans, different causes of pancreatitis have histologically distinct appearances. The histopathologic lesions in English Cocker Spaniels (ECS) with CP were noted to be histologically different than those of other breeds with CP. Hypothesis: CP in ECS is distinct from CP in other breeds and is characterized by a duct destruction similar to what is observed in autoimmune CP of humans. Animals: Eight ECS and 9 other breeds with histologically confirmed CP recruited over an 8‐year period and 50 postmortem control dogs with CP. Methods: Clinical, clinicopathological, and ultrasonographic findings were recorded. Histological sections were compared with a normal dog and 59 dogs of other breeds with CP. Immunohistochemistry using anti‐CD3, anti‐CD79a, and anti‐cytokeratin antibodies was used to evaluate distribution and type of lymphocytic inflammation and appearance of pancreatic ducts. Results: Four male and 4 female ECS presented at a mean age of 7.2 years. Clinical signs were similar in ECS and other breeds. The pancreas was enlarged and hypoechoic in 4 ECS and 2 controls. Histopathology was characterized by interlobular and periductular fibrosis and inflammation in ECS compared with intralobular disease in most other breeds. Immunohistochemistry identified prominent anti‐CD3+ lymphocytic infiltrates around venules and ducts and a marked absence of interlobular ducts in ECS compared with mixed T‐cell infiltration and ductular hyperplasia in most other breeds with CP. Conclusions and Clinical Importance: CP in ECS is distinct from CP in other breeds and is notably duct destructive.  相似文献   
995.
996.
997.
998.
Rubin GM  Lewis EB 《Science (New York, N.Y.)》2000,287(5461):2216-2218
The sequence of the Drosophila melanogaster genome presented in this issue of Science is the latest milestone in nine decades of research on this organism. Genetic and physical mapping, whole-genome mutational screens, and functional alteration of the genome by gene transfer were pioneered in metazoans with the use of this small fruit fly. Here we look at some of the instances in which work on Drosophila has led to major conceptual or technical breakthroughs in our understanding of animal genomes.  相似文献   
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