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   805811篇
  免费   94743篇
  国内免费   963篇
  901517篇
  2018年   7115篇
  2017年   6790篇
  2016年   10002篇
  2015年   14696篇
  2014年   16795篇
  2013年   23285篇
  2012年   27149篇
  2011年   27606篇
  2010年   18426篇
  2009年   16860篇
  2008年   24236篇
  2007年   25132篇
  2006年   23211篇
  2005年   22486篇
  2004年   22320篇
  2003年   21003篇
  2002年   20358篇
  2001年   34900篇
  2000年   35025篇
  1999年   28060篇
  1998年   10566篇
  1997年   10788篇
  1996年   10343篇
  1995年   9644篇
  1994年   9472篇
  1993年   9356篇
  1992年   23057篇
  1991年   22374篇
  1990年   22003篇
  1989年   21448篇
  1988年   19523篇
  1987年   18751篇
  1986年   17524篇
  1985年   17205篇
  1984年   14528篇
  1983年   12585篇
  1982年   9738篇
  1981年   8800篇
  1980年   8194篇
  1979年   13683篇
  1978年   10852篇
  1977年   9836篇
  1976年   9169篇
  1975年   10179篇
  1974年   11117篇
  1973年   10896篇
  1972年   9790篇
  1971年   9044篇
  1970年   7603篇
  1969年   7454篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
In cortical areas of the lizard, Podarcis hispanica, Timm staining reveals a distinct pattern of lamination. At the electron-microscope level, virtually all of the reaction product is located in the synaptic vesicles of Timm-positive boutons. Using linear-regression analysis, the area density of Timm-positive bouton profiles as well as the numerical and volume density of stained vesicles were found to be closely correlated with the light-microscopic densitometric values obtained for each Timm-positive cortical zone. We discuss the possibility of estimating stereological electron-microscopic data parameters from densitometric measurements at the light-microscope level.  相似文献   
992.
It has been found that fertility alpha 2-microglobulin content in male and female serum does not exceed 20 ng/ml and 40 ng/ml, respectively. A high level of fertility alpha 2-microglobulin was found in the serum in early pregnancy, with its concentration decreased by parturition.  相似文献   
993.
994.
995.
The potential impact of frog diseases on basic research is discussedin practical terms.  相似文献   
996.
997.
998.
Acetylcholine, oxotremorine and carbachol, compounds that exhibit muscarinic agonist activity, maximally inhibited basal prolactin secretion from GH3 cells by approx. 50% and intracellular cyclic AMP levels by approx. 20%. Both parameters were inhibited with similar potencies by each agonist. These inhibitory effects were blocked by a muscarinic but not by a nicotinic receptor antagonist. In the presence of VIP or IBMX, which raise intracellular cyclic AMP levels and stimulate hormone release, the degree of muscarinic inhibition was increased, but the potency remained unchanged. Similar changes in the secretory rate of prolactin and growth hormone occurred in these and in cell perifusion experiments. These results suggest that the inhibition of hormone secretion from GH3 cells by muscarinic agonists is mediated by a decrease in intracellular cyclic AMP levels.  相似文献   
999.
The distribution, synthesis transport, and glycosylation of rat-liver DT-diaphorase has been investigated. The enzyme could be isolated using specific antibodies, mainly from the soluble supernatant but also from microsomal vesicles, Golgi membrane, and mitochondria. 40% of the microsomal enzyme was located in the lumen or on the interior side of the membrane, the rest remaining as an integral non-extractable part of the membrane. Synthesis of DT-diaphorase takes place on both free and bound ribosomes, although it was found to be transported in a sequential manner from the rough to the smooth endoplasmic reticulum and also subsequently to the mitochondria. The rough and smooth microsomal DT-diaphorase contains covalently bound carbohydrate, but no sugar moiety could be detected bound to the cytoplasmic form of the enzyme.  相似文献   
1000.
Summated electrical activity of the human amygdaloid nucleus was investigated in the neurosurgical clinic by chronically implanted electrodes. It was found that odoriferous stimulation of this structure produced bursts of rapid rhythm (20–30 cps, 30–50 µV). The quasisinusoidal waves of olfactory rhythm consist of sinusoidal components which are more pronounced within the 20–30-Hz frequency range. Spindling of 1–3 sec duration occurs at the end of inhalation and the beginning of exhalation in time with breathing. During monorhinal breathing this activity, whose amplitude depends on degree of olfactory stimulation, can only be recorded ipsilaterally. Room air also activates the amygdaloid nucleus, but less strongly than odoriferous substances: No characteristic odor-dependent differences were discovered in the frequency range of the olfactory rhythm within a 20–30-Hz band.Institute of Physiology, Kiev State University, Kiev. Translated from Neirofiziologiya, Vol. 18, No. 1, pp. 61–69, January–February, 1986.  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