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   842794篇
  免费   93943篇
  国内免费   482篇
  937219篇
  2018年   7736篇
  2017年   7580篇
  2016年   10414篇
  2015年   13459篇
  2014年   15922篇
  2013年   23439篇
  2012年   26043篇
  2011年   26515篇
  2010年   17847篇
  2009年   16512篇
  2008年   23500篇
  2007年   24200篇
  2006年   22798篇
  2005年   21804篇
  2004年   21650篇
  2003年   20620篇
  2002年   20104篇
  2001年   40901篇
  2000年   40884篇
  1999年   32436篇
  1998年   10859篇
  1997年   11533篇
  1996年   10851篇
  1995年   9947篇
  1994年   9869篇
  1993年   9725篇
  1992年   26395篇
  1991年   25279篇
  1990年   24786篇
  1989年   24317篇
  1988年   22342篇
  1987年   21041篇
  1986年   19587篇
  1985年   19523篇
  1984年   15906篇
  1983年   13625篇
  1982年   10303篇
  1981年   9153篇
  1980年   8806篇
  1979年   15036篇
  1978年   11634篇
  1977年   10588篇
  1976年   9851篇
  1975年   10810篇
  1974年   11544篇
  1973年   11308篇
  1972年   10341篇
  1971年   9286篇
  1970年   8112篇
  1969年   7554篇
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
41.
42.
The preservation of purine ring as purine bases appears to be a common feature of camel liver. Hepatic guanine appears to be actively converted into GMP in the camel rather than further degraded. The limiting step of guanine degradation appears to be the lack of hepatic guanase activity. Higher purine bases over uric acid ratios were found in camel urine with respect to those of zebu.  相似文献   
43.
Smooth-muscle myosin purified as described by Persechini & Hartshorne [(1983) Biochemistry 22, 470-476] contains trace amounts of calmodulin and myosin light-chain kinase, which can be removed by Ca2+-dependent hydrophobic-interaction chromatography followed by calmodulin-Sepharose affinity chromatography. The resultant column-purified myosin exhibits properties similar to those of the non-purified myosin, e.g. actin activation of the Mg2+-ATPase requires Ca2+/calmodulin-dependent phosphorylation of the two 20 kDa light chains. However, unlike the non-purified myosin, the column-purified myosin undergoes a time-dependent transition to a form which no longer requires phosphorylation for actin activation of the myosin Mg2+-ATPase. This transition is identified as a time-dependent change in conformation of the column-purified myosin from a 10 S to 6 S form and is caused by slow oxidation of the column-purified myosin, since it could be prevented by storage under N2 and reversed by 5 mM-dithiothreitol.  相似文献   
44.
45.
The study of the specific epidemiological and clinical features of Q fever revealed the existence of an active focus of infection among humans due to their contacts with agricultural animals in one of the districts of the region. The focus was manifested by group morbidity among the cattle-tending personnel of a dairy farm. The source of this infection was cattle. The infection was transferred mainly through the air. The disease took a moderately severe course. The study of the rickettsial contamination of humans, animals and ticks suggested the presence of the active epidemic process and made it possible to work out concrete antiepidemic measures.  相似文献   
46.
47.
48.
49.
50.
The content of neurospecific proteins S-100, GFA and D2 was measured in malignant cerebral tumors by electrophoresis with the use of monospecific antisera. Concomitant measurement of proteins S-100 and GFA is a more reliable diagnostic criterion as to the tumor histogenesis than study of each protein alone. D2 protein appeared to be the most stable specific marker.  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