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   1354542篇
  免费   121760篇
  国内免费   1511篇
  2021年   17755篇
  2019年   16141篇
  2018年   17369篇
  2017年   16143篇
  2016年   27845篇
  2015年   42341篇
  2014年   50525篇
  2013年   76739篇
  2012年   35605篇
  2011年   23550篇
  2010年   42914篇
  2009年   44476篇
  2008年   22587篇
  2007年   20574篇
  2006年   26274篇
  2005年   27239篇
  2004年   26607篇
  2003年   24217篇
  2002年   22569篇
  2001年   35132篇
  2000年   32725篇
  1999年   32391篇
  1998年   25518篇
  1997年   25310篇
  1996年   24796篇
  1995年   23003篇
  1994年   22816篇
  1993年   21901篇
  1992年   27850篇
  1991年   25980篇
  1990年   24597篇
  1989年   25390篇
  1988年   23352篇
  1987年   22103篇
  1986年   21244篇
  1985年   23152篇
  1984年   22809篇
  1983年   20042篇
  1982年   20753篇
  1981年   19971篇
  1980年   18571篇
  1979年   19024篇
  1978年   18025篇
  1977年   17285篇
  1976年   16458篇
  1975年   16097篇
  1974年   16790篇
  1973年   17115篇
  1972年   14677篇
  1971年   13419篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
When rats received glucagon or insulin every 2 h after partial hepatectomy (Hx), hepatic putrescine content was increased above control levels at 6 and 12 h, respectively. When the two hormones were combined, the increased levels were additive. Hepatic ornithine decarboxylase activity was above control levels at 12 h after insulin treatment. Hepatic spermidine N1-acetyltransferase activity was enhanced at 6 h only when glucagon was dosed. Putrescine administration from 0 to 4 h or from 6 to 10 h increased hepatic DNA synthesis to similar levels 22 h after Hx. These results suggest that glucagon and insulin additively stimulate hepatic putrescine production after Hx. This may explain the cooperative stimulation of liver regeneration by both hormones.  相似文献   
972.
There was a range of severity of parasitism of stem-borer larvae by Hymenoptera and Nematoda and much premature death of the larvae. A nematode, Panagrolaimus rigidus, normally considered to be saprophytic, was implicated in some mortality of stem-borer larvae.  相似文献   
973.
974.
975.
We here report the second record of a developmentally aberrant strain of a cellular slime mold from natural populations and demonstrate that this Dictyostelium mucoroides variant is capable of undergoing normal morphogenesis in the presence of the phycomycete fungus, Mucor hiemalis. The synergism is induced by an extracellular product(s) which is diffusable through thin agar membranes and is released by the fungus. The presence of the fungus not only induces stalk formation in this stalkless variant, but also increases the rate of sorocarp formation in 3 of 5 additional species of cellular slime molds assayed.  相似文献   
976.
977.
Summary On adapting brackish waterAnguilla anguilla to fresh water it was noted that, while the plasma sodium, magnesium,pCO2 and pH were held reasonably constant, there was a substantial fall in chloride concentration (–33 mEq). The gradient of the linear correlations between plasma sodium and chloride also fell (brackish water gradient=0.92, fresh water gradient=0.21) indicating that a new pattern of plasma ion interrelationships was being established. Comparison with plasma Na/Cl ion ratios from other fishes suggested that this phenomenon was peculiar toA. anguilla. Corresponding with the very low plasma chloride levels plasma bicarbonate was four to five times that found in other fishes, and this was thought related to the finding that the haematocrit value almost doubled during adaptation to fresh water. In fresh water adapted fish a fall in plasma chloride was associated with a rise in plasma bicarbonate, however the charge compensation effect of this response was only partial as summing the common plasma cations and anions left an anion deficit of about 34 mEq to be accounted for.  相似文献   
978.
979.
980.
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