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   1348篇
  免费   8篇
  国内免费   12篇
系统科学   26篇
丛书文集   1篇
教育与普及   1篇
理论与方法论   13篇
现状及发展   252篇
研究方法   212篇
综合类   803篇
自然研究   60篇
  2020年   5篇
  2018年   14篇
  2017年   17篇
  2016年   7篇
  2015年   12篇
  2014年   16篇
  2013年   18篇
  2012年   99篇
  2011年   188篇
  2010年   37篇
  2009年   9篇
  2008年   101篇
  2007年   102篇
  2006年   95篇
  2005年   119篇
  2004年   93篇
  2003年   72篇
  2002年   87篇
  2001年   21篇
  2000年   14篇
  1999年   8篇
  1994年   3篇
  1992年   2篇
  1991年   7篇
  1990年   8篇
  1989年   2篇
  1988年   4篇
  1987年   7篇
  1986年   6篇
  1985年   4篇
  1984年   4篇
  1983年   4篇
  1982年   5篇
  1981年   5篇
  1980年   3篇
  1979年   4篇
  1978年   9篇
  1977年   14篇
  1976年   8篇
  1975年   9篇
  1974年   14篇
  1973年   7篇
  1972年   7篇
  1971年   12篇
  1970年   14篇
  1969年   17篇
  1968年   12篇
  1967年   11篇
  1966年   10篇
  1965年   7篇
排序方式: 共有1368条查询结果,搜索用时 15 毫秒
151.
152.
153.
T L Thompson  W E Thomas 《Experientia》1985,41(11):1437-1438
Administration of the organophosphate compound soman in rats resulted in an inhibition of choline acetyltransferase activity in almost all brain regions examined. Enzyme activity was inhibited by 20-50% in various brain regions 30 min after soman injection (94-120 micrograms/kg). Enzyme activity in two regions decreased with time to a near zero level by 3 h after injection.  相似文献   
154.
A unique "integrated hard-templating strategy" is described for facile synthesis of a carbonaceous mate-rial with a novel three-dimensional (3D) branched hollow...  相似文献   
155.
An analytic hierarchy process model of group consensus   总被引:1,自引:0,他引:1  
In group decision making, a certain degree of consensus is necessary to derive a meaningful and valid outcome. This paper proposes a consensus reaching model for a group by using the Analytic Hierarchy Process (AHP). It supports people to improve their group consensus level through an updating of their judgments. In this model, a moderator suggests the most discoraant aeclslon manet to update his judgment in each step. The proposed consensus reaching model allows decision makers to accept or reject the suggestion from the moderator. This model ensures that the judgment updating is effective and the final solution will be of acceptable consistency. Finally, a numerical example is given to illustrate the validity of the proposed consensus reaching model.  相似文献   
156.
157.
The mechanisms whereby G protein-coupled receptors (GPCR) activate signalling pathways involved in mRNA translation are ill-defined, in contrast to tyrosine kinase receptors (TKR). We compared a GPCR and a TKR, both endogenously expressed, for their ability to mediate phosphorylation of 70-kDa ribosomal S6 kinase p70S6K in primary rat Sertoli cells at two developmental stages. In proliferating cells stimulated with follicle-stimulating hormone (FSH), active p70S6K was phosphorylated on T389 and T421/S424, through cAMP-dependent kinase (PKA) and phosphatidyl-inositide-3 kinase (PI3K) antagonizing actions. In FSH-stimulated differentiating cells, active p70S6K was phosphorylated solely on T389, PKA and PI3K independently enhancing its activity. At both developmental stages, insulin-induced p70S6K regulation was consistent with reported data. Therefore, TKR and GPCR trigger distinct p70S6K active conformations. p70S6K developmental regulation was formalized in a dynamic mathematical model fitting the data, which led to experimentally inaccessible predictions on p70S6K phosphorylation rate.  相似文献   
158.
159.
Cyclase-associated proteins are highly conserved proteins that have a role in the regulation of actin dynamics. Higher eukaryotes have two isoforms, CAP1 and CAP2. To study the in vivo function of CAP2, we generated mice in which the CAP2 gene was inactivated by a gene-trap approach. Mutant mice showed a decrease in body weight and had a decreased survival rate. Further, they developed a severe cardiac defect marked by dilated cardiomyopathy (DCM) associated with drastic reduction in basal heart rate and prolongations in atrial and ventricular conduction times. Moreover, CAP2-deficient myofibrils exhibited reduced cooperativity of calcium-regulated force development. At the microscopic level, we observed disarrayed sarcomeres with development of fibrosis. We analyzed CAP2’s role in actin assembly and found that it sequesters G-actin and efficiently fragments filaments. This activity resides completely in its WASP homology domain. Thus CAP2 is an essential component of the myocardial sarcomere and is essential for physiological functioning of the cardiac system, and a deficiency leads to DCM and various cardiac defects.  相似文献   
160.
The early fall diet of Oregon blue grouse ( Dendragapus obscurus pallidus ) from Wallowa County, Oregon, was determined from 145 crops obtained during 1981 and 1982. Of more than 50 plant and animal foods in the diet, short-horned grasshoppers ( Acrididae ), prickly lettuce ( Lactuca serriola ), yellow salsify ( Tragopogon dubius ), wild buck-wheat ( Eriogonum spp.), and snowberry ( Symphoricarpos albus ) occurred in 30% or more of the crops and collectively amounted to 68% of the diet by weight. Seven of the 12 most common foods were consumed differentially by the four sex and age classes of birds. Results indicated that blue grouse foraged in forest and grassland habitats.  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