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   188821篇
  免费   10392篇
  国内免费   108篇
林业   7720篇
农学   6014篇
基础科学   1321篇
  22527篇
综合类   33233篇
农作物   7054篇
水产渔业   9532篇
畜牧兽医   96347篇
园艺   2373篇
植物保护   13200篇
  2018年   2450篇
  2017年   2651篇
  2016年   2502篇
  2015年   2191篇
  2014年   2703篇
  2013年   7003篇
  2012年   5000篇
  2011年   6192篇
  2010年   4017篇
  2009年   4091篇
  2008年   6217篇
  2007年   5846篇
  2006年   5701篇
  2005年   5282篇
  2004年   5253篇
  2003年   5240篇
  2002年   5073篇
  2001年   5968篇
  2000年   5774篇
  1999年   4733篇
  1998年   2015篇
  1997年   1980篇
  1996年   1888篇
  1995年   2234篇
  1994年   2099篇
  1993年   2014篇
  1992年   3979篇
  1991年   4156篇
  1990年   4260篇
  1989年   4142篇
  1988年   3844篇
  1987年   3860篇
  1986年   3983篇
  1985年   3820篇
  1984年   3252篇
  1983年   2894篇
  1982年   1970篇
  1981年   1847篇
  1980年   1821篇
  1979年   2943篇
  1978年   2437篇
  1977年   2103篇
  1976年   1919篇
  1975年   2024篇
  1974年   2565篇
  1973年   2621篇
  1972年   2565篇
  1971年   2339篇
  1970年   2208篇
  1969年   2096篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
141.
Individual antigens of goats   总被引:1,自引:0,他引:1  
  相似文献   
142.
As anaerobic sampling and culture techniques improved, the documented prevalence of anaerobic bacteria in periodontal disease has increased. The anaerobic bacteria have become more well-known in humans and consequently in dogs, since this species is a major model in periodontal studies. A review of the literature related to anaerobic flora is described.  相似文献   
143.
Cellular alterations in level of expression of mRNA encoding for prostaglandin endoperoxide synthase were quantified within ovarian tissues of sheep obtained before, during and after induction of the preovulatory surge of LH and ovulation with LHRH. This was accomplished by isotopic in situ hybridization using a selective cRNA probe to ovine prostaglandin endoperoxide synthase mRNA. A significant elevation in mRNA was detected within the theca interna of the preovulatory follicle at 8, 16 and 24 hr following administration of LHRH. Very close to the time of ovulation (ie., at 24 hr post-LHRH) a marked rise in mRNA was observed in association with epithelial cells covering the apical surface of the follicle. Ovarian cyclooxygenase metabolites of arachidonic acid produced during the ovulatory process in the ewe originate within the thecal layer and germinal epithelium of the follicle destined to ovulate.  相似文献   
144.
The practice of small animal theriogenology is rewarding, but frustrations exist concerning technologic advances as compared with other species. Reproductive clinicians striving to practice good quality medicine readily identify topics of common concern: causes that are not identified or therapeutics that are not available or applicable. Improved collaboration among theriogenologists specializing in small animal practice is evidenced by growing attendance at national and international scientific meetings, increased scientific publications, and internet communications.  相似文献   
145.
One-month-old Syrian hamsters of the APA and Std: golden strains were inoculated intraperitoneally with 10(5) PFU/head of the D variant of encephalomyocarditis (EMC) virus and examined virologically and pathologically up to 7 days after inoculation. APA hamsters developed apparent hyperglycemia due to pancreatic islet cell damage while Std:golden hamsters did not. Hamsters of both strains showed clear histopathologic changes in the testis with prominent viral replication as well as in the brain, heart and exocrine pancreas. The susceptibility to EMC virus-infection was higher in males than in females and in APA than in Std: golden hamsters.  相似文献   
146.
An ammonium sulfate fraction of Taenia hydatigena cyst fluid (ThFAS) was further fractionated by hydrophobic interaction chromatography, using alkylagarose and omega-amino alkylagarose columns, in an effort to isolate and purify a specific diagnostic antigen in the ThFAS preparation. The less than 12 kDa antigen was found to have an affinity for immobilized alkanes with chain length of six carbons or greater. The antigen was recovered in an ethylene glycol eluate from a hexylagarose column then analyzed by Western blot; it reacted with bovine and human cysticercosis infection sera and with specific monoclonal antibodies but not with control sera or fascioliasis infection sera. When the eluate was used as coating antigen in a plate ELISA assay no false positive reactions were seen in sera from cattle infected with Fasciola hepatica; false positive reactions were observed for the unfractionated ThFAS antigen preparation.  相似文献   
147.
148.
149.
150.
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