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   203232篇
  免费   10600篇
  国内免费   140篇
林业   8605篇
农学   6305篇
基础科学   1363篇
  24973篇
综合类   36534篇
农作物   8216篇
水产渔业   9700篇
畜牧兽医   102653篇
园艺   2649篇
植物保护   12974篇
  2019年   1839篇
  2018年   2696篇
  2017年   3070篇
  2016年   2830篇
  2015年   2364篇
  2014年   2971篇
  2013年   7941篇
  2012年   5585篇
  2011年   6938篇
  2010年   4582篇
  2009年   4638篇
  2008年   6919篇
  2007年   6448篇
  2006年   6037篇
  2005年   5706篇
  2004年   5579篇
  2003年   5638篇
  2002年   5246篇
  2001年   6132篇
  2000年   6201篇
  1999年   4822篇
  1998年   2150篇
  1997年   2094篇
  1996年   1952篇
  1995年   2361篇
  1994年   2153篇
  1993年   2009篇
  1992年   4110篇
  1991年   4387篇
  1990年   4239篇
  1989年   4241篇
  1988年   3916篇
  1987年   3918篇
  1986年   4091篇
  1985年   3981篇
  1984年   3224篇
  1983年   2937篇
  1982年   1950篇
  1979年   3036篇
  1978年   2454篇
  1977年   2001篇
  1976年   2039篇
  1975年   2147篇
  1974年   2611篇
  1973年   2728篇
  1972年   2602篇
  1971年   2471篇
  1970年   2314篇
  1969年   2275篇
  1967年   1951篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
The Internet is a fast-growing technology that allows information (text as well as images) to be shared across the world in an instant. As computer systems, software, and Internet services become less expensive options, the world becomes more experienced and comfortable with these technologies. In the foreseeable future, equine veterinarians are likely to be better educated about diseases and treatments, better connected with specialists for consultations on difficult cases, able to respond to client communications more efficiently, able to accurately educate clients, and able to communicate with colleagues from across the country and the world. Additionally, there is likely to be a time when using the Internet and computers is profitable in all these ways as well as economically. Improving doctor-client relationships and patient care are goals for all veterinarians, and the Internet holds the technology to render these now and in the future.  相似文献   
112.
Contents: An insemination trial using frozen semen is described. The freezing procedure was slightly modified from the Hannover method. The insemination dose consisted of 7 medium straws containing approx 1 109 spermatozoa. A total of 28 mares of the Norwegian Trotter breed were inseminated during the 1991 season. During oestrus the mares were examined at 12 hour intervals, and the insemination was carried out after detection of ovulation. The pregnancy rate was 43% after the first insemination, increased to 68% after second and further to 75% after the third and last insemination. The foaling rate was 61.5%.  相似文献   
113.
114.
115.
116.
Trialcylglycerol (TG) lipase was isolated and partially purified from rainbow trout liver. Triacylglycerol lipase activity was assayed by measuring14C-oleic acid release from14C-triolein.14C-oleic acid release was linear for up to two hours. Optimal activity occurred at pH 7.0 and 15°C. Most of the lipase activity was recovered in the cytosolic fraction. A 27,000-fold purification was achieved after Sepharose (Bio-gel A 0.5 M, 200–400 mesh) chromatography of a resuspended 20% ammonium sulfate fraction. The molecular weight of the trout hepatic lipase as determined by size-exclusion chromatography and by SDS-polyacrylamide gel electrophoresis was 40–43 kD. Lipase-mediated hydrolysis of TG resulted in the production of diacylglycerols, monoacylglycerols, and fatty acids. Kinetic analysis indicated that Vmax=0.016 nmol/h/mg protein and that Km=0.28 mM triolein. Lipolytic activity was enhanced in the presence of cAMP/ATP-Mg2+. These results suggest that the liver of trout possesses a neutral TG lipase that is responsible for mobilizing stored TG and is catalytically activated by phosphorylation.A part of this work was presented at the Annual Meeting of the American Society of Zoologists, December 26–30, 1990, San Antonio, TX.  相似文献   
117.
The technique of cystocentesis in dogs and cats was studied. The indications and contraindications of this method are discussed, using illustrations.  相似文献   
118.
119.
Time course of grain filling pattern in two rice (Oryza sativa L.) cultivars, grown under normal and low light intensities, was studied. The number of spikelets, partially filled grains and high density grains were monitored at a 5 day interval during grain filling period from uniform panicles tagged at anthesis. The low light tolerant cultivar Swarnaprabha had more high density grains and less partially filled grains throughout the grain filling period and at harvest compared to cultivar Ratna under both normal and low light intensities. Further, the opening of spikelets in two flushes in Swarnaprabha seemed to result in a more efficient resource allocation and hence better yield as compared to Ratna, in which the opening of spikelets was in a single flush on day 10.  相似文献   
120.
Digital diseases are commonly seen in cattle. Cattle affected by digital disorders do not always respond to conservative therapy and require surgery. Surgical procedures for the common digital disorders are described, with emphasis on the different approaches to the distal interphalangeal joint.  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