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   268篇
  免费   30篇
  国内免费   1篇
林业   10篇
基础科学   1篇
  28篇
综合类   72篇
农作物   9篇
水产渔业   11篇
畜牧兽医   158篇
园艺   4篇
植物保护   6篇
  2023年   3篇
  2021年   2篇
  2020年   7篇
  2019年   3篇
  2018年   9篇
  2017年   5篇
  2016年   8篇
  2015年   10篇
  2014年   8篇
  2013年   18篇
  2012年   8篇
  2011年   17篇
  2010年   6篇
  2009年   7篇
  2008年   4篇
  2007年   8篇
  2006年   13篇
  2005年   9篇
  2004年   7篇
  2003年   4篇
  2002年   2篇
  2001年   3篇
  2000年   4篇
  1999年   3篇
  1998年   7篇
  1997年   8篇
  1996年   5篇
  1995年   5篇
  1994年   7篇
  1993年   5篇
  1992年   7篇
  1991年   6篇
  1990年   4篇
  1989年   6篇
  1988年   2篇
  1986年   2篇
  1985年   4篇
  1984年   2篇
  1983年   4篇
  1973年   2篇
  1972年   3篇
  1971年   3篇
  1967年   2篇
  1966年   2篇
  1946年   2篇
  1945年   2篇
  1944年   8篇
  1942年   2篇
  1941年   2篇
  1932年   2篇
排序方式: 共有299条查询结果,搜索用时 338 毫秒
81.
Left dorsal displacement of the large colon is a condition unique to the horse that results in an obstruction of the colon and signs of colic. This condition may be successfully treated medically with analgesia, i.v. or oral fluids and feed restriction, exercise with or without administration of phenylephrine, or rolling under general anaesthesia with or without administration of phenylephrine, or a combination of these conservative options. Surgical correction via standing left flank laparotomy or, more commonly, ventral midline laparotomy under general anaesthesia, is required in cases where conservative therapy is unsuccessful. Recurrence rates range from 3.2% to 21%. Surgical attempts to prevent recurrence of this condition include large colon resection, colopexy, and ablation of the nephrosplenic space.  相似文献   
82.
83.
84.
A 0.6-centimeter-thick sublayer was found in horizontal flow profiles obtained by traversing a heated thermistor from 19 centimeters above to 2 centimeters below the water-sediment interface in 200-meter-deep water on the Oregon continental shelf. In this sublayer the speed of the current varies linearly with distance above the sediment. Estimates of viscous stress from this sublayer and turbulent stress from the profile agree within 5 percent. Stress calculated from a current-meter spectrum agrees within its 95 percent confidence limits.  相似文献   
85.
86.
The obligate intracellular prokaryote Chlamydia trachomatis is the etiological agent of trachoma and is a primary causative pathogen of sexually transmitted genital tract disease; both diseases affect millions of people each year. The cloning of genes encoding the enzyme or enzymes producing the genus-specific lipopolysaccharide antigen of Chlamydia into Escherichia coli is reported here. The cloned chlamydial lipopolysaccharide antigen appears to be a hybrid lipopolysaccharide molecule composed of both Chlamydia and Escherichia coli components. The chlamydial lipopolysaccharide antigen is expressed on the surfaces of the viable Escherichia coli recombinants. These findings may have a significant impact on defining the role of this highly conserved antigen in the pathogenesis and diagnosis of chlamydial infections.  相似文献   
87.
The hyphae of the water mold Achyla bisexualis generate electrical currents that enter the growing tips and leave farther back. An inward-moving current also precedes branching and predicts the site of branch emergence; during the branching process, the current at the original tip declines or even reverses transiently without any change in growth rate. The inward current probably acts as an early signal during branch differentiation. The flow of specific ions rather than the flow of electrical charge probably serves to localize growth.  相似文献   
88.
The first direct images of the Jovian aurora at ultraviolet wavelengths were obtained by the Hubble Space Telescope Faint Object Camera near the time of the Ulysses spacecraft encounter with Jupiter on 8 February 1992. The auroral oval is not uniformly luminous. It exhibits a brightness minimum in the vicinity of longitude 180 degrees . In the few images available, the brightest part of the oval occurs in late afternoon Jovian time. The observed oval is not concentric with calculated ovals in the O(6) model of Connerney. The size of the oval is consistent with auroral particles on field lines with magnetic L parameter >8, indicating significant migration from lo, its torus, or both, if these are their origins.  相似文献   
89.
90.
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