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   428168篇
  免费   48358篇
  国内免费   164篇
  2018年   3957篇
  2016年   5355篇
  2015年   7037篇
  2014年   8291篇
  2013年   11418篇
  2012年   13014篇
  2011年   13453篇
  2010年   9196篇
  2009年   8527篇
  2008年   12323篇
  2007年   12799篇
  2006年   12015篇
  2005年   11502篇
  2004年   11516篇
  2003年   10778篇
  2002年   10608篇
  2001年   17563篇
  2000年   17572篇
  1999年   14031篇
  1998年   5082篇
  1997年   5323篇
  1996年   4965篇
  1995年   4663篇
  1994年   4540篇
  1993年   4592篇
  1992年   11715篇
  1991年   11633篇
  1990年   11389篇
  1989年   10979篇
  1988年   10572篇
  1987年   10167篇
  1986年   9435篇
  1985年   9308篇
  1984年   7818篇
  1983年   6754篇
  1982年   5213篇
  1981年   4665篇
  1980年   4495篇
  1979年   7464篇
  1978年   5892篇
  1977年   5419篇
  1976年   5232篇
  1975年   5623篇
  1974年   6333篇
  1973年   6206篇
  1972年   5782篇
  1971年   5237篇
  1970年   4658篇
  1969年   4588篇
  1968年   4427篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Experiments on conscious rabbits were made to elaborate motor conditioned reflexes through pairing stimuli with electrocutaneous reinforcement applied every 30 s. Neuronal activity in the sensorimotor cortex and putamen was recorded during formation and reproduction of the conditioned reflexes before and after haloperidol injection (0.2 mg/kg i. v.). In the putamen, haloperidol increased the number of neurons exhibiting trace conditioned activity and made the intensity and duration of these processes rise. The changes seen in the sensorimotor cortex were opposite in nature. Inhibition of trace conditioned activity in the sensorimotor cortex depended mainly on the decreased amplitude of the reaction conditioned component. The role of the dopaminergic system in the interaction of the neostriatum and sensorimotor cortex and in formation and reproduction of trace conditioned activity of both the structures is discussed.  相似文献   
22.
23.
24.
The Fis protein: it''s not just for DNA inversion anymore   总被引:36,自引:0,他引:36  
  相似文献   
25.
Changes in the properties of adenylate cyclase from the lungs of tuberculotic guinea pigs were revealed. The number of beta-adrenergic receptors in the lungs was found to be reduced by 30% at the second and by 70% at the third stage of the disease. The degree and the value of Ka for adenylate cyclase activation by isoproterenol remained thereby unchanged. The basal activity of adenylate cyclase was increased by 20% against the control level at the second stage and decreased by 20% at the third stage of the disease. At these periods, the stimulating effects of guanylyl imidodiphosphate, NaF and forskolin on lung adenylate cyclase were diminished. The experimental results point to the significant role of the enzymes of cAMP metabolism and reflect the course of the tuberculosis process in experimental animals.  相似文献   
26.
The immunization of mice with the protein fraction of B. pertussis strain 305 has made it possible to obtain hybridomas producing monoclonal antibodies to B. pertussis antigens. Ascitic fluids containing monoclonal antibodies react in the ELISA in high titers and actively agglutinate B. pertussis strains 305 and 475.  相似文献   
27.
28.
29.
30.
Regulation of many cell systems has been shown to be mediated by Inositol 1,4,5-trisphosphate which causes a release of calcium from intracellular sites. We have shown that release of Ca2+ from sarcoplasmic reticulum microsomes was not stimulated by IP3. The phorbol ester, TPA, also had no effect on Ca2+ release or Ca2+ ATPase activity. Thus, it is unlikely that the breakdown of polyphosphatidylinositides serves as a second messenger to mediate release of Ca2+ in skeletal muscle.  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