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   1636850篇
  免费   147709篇
  国内免费   1428篇
  2021年   18603篇
  2019年   16584篇
  2018年   20529篇
  2017年   19254篇
  2016年   30349篇
  2015年   44097篇
  2014年   52139篇
  2013年   78715篇
  2012年   49411篇
  2011年   40828篇
  2010年   48903篇
  2009年   48729篇
  2008年   37000篇
  2007年   36034篇
  2006年   38512篇
  2005年   39430篇
  2004年   38268篇
  2003年   35467篇
  2002年   33341篇
  2001年   48401篇
  2000年   45793篇
  1999年   42291篇
  1998年   27281篇
  1997年   26948篇
  1996年   26249篇
  1995年   24392篇
  1994年   23993篇
  1993年   23266篇
  1992年   35686篇
  1991年   34268篇
  1990年   32797篇
  1989年   33223篇
  1988年   30397篇
  1987年   29185篇
  1986年   27474篇
  1985年   28949篇
  1984年   27228篇
  1983年   24027篇
  1982年   22770篇
  1981年   21740篇
  1980年   20350篇
  1979年   23327篇
  1978年   21011篇
  1977年   19725篇
  1976年   18969篇
  1975年   19108篇
  1974年   19986篇
  1973年   20243篇
  1972年   17458篇
  1971年   15857篇
排序方式: 共有10000条查询结果,搜索用时 937 毫秒
931.
932.
933.
The Oral History and Literature of the Wolof People of Waalo, Northern Senegal. Samba Diop. Lewiston, Canada; Edwin Mellen Press, 1995. 389 pp.  相似文献   
934.
935.
936.
Individual-site isotherms add experimental data which may allow for a more detailed definition of the parameters in a system with interacting binding sites. Individual-site isotherms accomplish the following: (A) In general, they define little more than the total or combined isotherm except to reveal the existence of different sites. (B) Under the limiting conditions of symmetrical interactions in two site systems they define: (1) the ratio of the unperturbed or intrinsic binding constants rather than their actual values, (2) the unperturbed shape of the total isotherm, that is, the shape of the total isotherm if there were no ligand dependent interactions between the sites, and (3) the perturbation of the shape of the total isotherm derived from interactions between the sites. (C) They do not define the nature of the interactions; that is, they do not resolve the free energies of the interactions between the sites. (D) When some assumptions about the nature of the interactions are made they may aid in defining some free energies of interaction between the sites.  相似文献   
937.
The muscle phase of Trichinella spiralis and of Trichinella sp. isolated in the Arctic was compared in experimental and wild animals. Reproductive capacity indices (RCI) of the Trichinella sp. isolate were significantly lower in laboratory rodents but were similar to T. spiralis in wild rodents. Sprague-Dawley rats were the most refractory to the Trichinella sp. isolate of all laboratory rodents. Outbred strains of mice were more susceptible to both T. spiralis and the Trichinella sp. isolate than inbred strains of mice. T. spiralis muscle larvae survived longer in mice and the survival of both T. spiralis and the Trichinella sp. isolate larvae was higher in female mice. While single pair interbreeding experiments showed reproductive isolation between T. spiralis and the Trichinella sp. isolate, multiple pair and transplant breeding experiments showed reproductive compatibility. Male and female infective larvae of T. spiralis and the Trichinella sp. isolate differed morphometrically, but a convergence in size of worms was observed after prolonged passages of the parasites in mice. Passaging history of the isolate and host species was found to have a significant effect on Trichinella morphology. It is proposed that the Trichinella sp. isolate is a physiological variant of T. spiralis and not a distinct species.  相似文献   
938.
Elevated serum gamma-glutamyl transferase (GGT) levels were found in 29% of 155 chronic alcoholics undergoing detoxification treatment. Alkaline phosphatase (AP) was increased in 16%, alanine aminotransferase--SGPT (ALT) in 12% of the patients, while 23% had elevations of either AP or ALT or both. Of the foregoing parameters, GGT was the best single indicator of liver involvement. In course of the follow-ups GGT/ALT correlation improved, but GGT/AP correlation deteriorated. In 9 patients, abstinence during follow-up was associated with progressive decrease in previously elevated serum GGT. Because of its unique sensitivity, GGT may be useful as a screening and/or monitoring aid in alcoholism.  相似文献   
939.
Editorial     
  相似文献   
940.
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