首页 | 官方网站   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   310416篇
  免费   3734篇
  国内免费   713篇
工业技术   314863篇
  2021年   2277篇
  2019年   2147篇
  2018年   3617篇
  2017年   3450篇
  2016年   3548篇
  2015年   2542篇
  2014年   4453篇
  2013年   14283篇
  2012年   7385篇
  2011年   10133篇
  2010年   7906篇
  2009年   9159篇
  2008年   9618篇
  2007年   9604篇
  2006年   8530篇
  2005年   7905篇
  2004年   7777篇
  2003年   7510篇
  2002年   7361篇
  2001年   7562篇
  2000年   7222篇
  1999年   7563篇
  1998年   17720篇
  1997年   12865篇
  1996年   10124篇
  1995年   7898篇
  1994年   7214篇
  1993年   6918篇
  1992年   5295篇
  1991年   5073篇
  1990年   4944篇
  1989年   4797篇
  1988年   4682篇
  1987年   3891篇
  1986年   4013篇
  1985年   4720篇
  1984年   4283篇
  1983年   4024篇
  1982年   3609篇
  1981年   3767篇
  1980年   3460篇
  1979年   3430篇
  1978年   3233篇
  1977年   3824篇
  1976年   4857篇
  1975年   2788篇
  1974年   2665篇
  1973年   2677篇
  1972年   2216篇
  1971年   1965篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Comments on L. R. Goldberg's (see record 1993-17546-001) history of the Big Five framework of personality traits and elaborated on its use. The reasons why industrial/organizational psychologists de-emphaszied the impact of personality on the job peformance in the late 1960s and 1970s and re-emphasized it in the 1980s are addressed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
103.
SCG10 is a neuron-specific, membrane-associated protein that is highly concentrated in growth cones of developing neurons. Previous studies have suggested that it is a regulator of microtubule dynamics and that it may influence microtubule polymerization in growth cones. Here, we demonstrate that in vivo, SCG10 exists in both phosphorylated and unphosphorylated forms. By two-dimensional gel electrophoresis, two phosphoisoforms were detected in neonatal rat brain. Using in vitro phosphorylated recombinant protein, four phosphorylation sites were identified in the SCG10 sequence. Ser-50 and Ser-97 were the target sites for protein kinase A, Ser-62 and Ser-73 for mitogen-activated protein kinase and Ser-73 for cyclin-dependent kinase. We also show that overexpression of SCG10 induces a disruption of the microtubule network in COS-7 cells. By expressing different phosphorylation site mutants, we have dissected the roles of the individual phosphorylation sites in regulating its microtubule-destabilizing activity. We show that nonphosphorylatable mutants have increased activity, whereas mutants in which phosphorylation is mimicked by serine-to-aspartate substitutions have decreased activity. These data suggest that the microtubule-destabilizing activity of SCG10 is regulated by phosphorylation, and that SCG10 may link signal transduction of growth or guidance cues involving serine/threonine protein kinases to alterations of microtubule dynamics in the growth cone.  相似文献   
104.
This paper focuses on the hydrodynamics of third sound on a superfluid 3 He film. We solve the hydrodynamical equations in the limit of thick films with weak interaction with the substrate. The surface tension at the free interface is shown to have a large effect on the third sound velocity and on the attenuation for frequencies larger than 1Hz. In the case of a diffusely scattering substrate a ripplon-like dispersion relation is found for this frequency range.  相似文献   
105.
Heat transfer of highly consistent shear-thinning fluids flowing in a horizontal cylindrical channel has been investigated numerically and experimentally when the outer channel wall is subjected to a constant convective heat exchange. The case considered being cooling, a possible ice deposit must be taken into account. The variation of the rheological properties with temperature must be considered as well.  相似文献   
106.
107.
108.
The biotransformation of oxazepam by Bifidobacterium bifidum was studied. The major metabolite was purified by chromatographic methods and found to be desmethyldiazepam using NMR, IR and other physicochemical data.  相似文献   
109.
Butyl, hexyl, and 2-ethylhexyl diesters of 1,1-bis(5-carboxyl-2-furyl)-2,2-dichloroethene, hexyl and 2-ethylhexyl diesters of 1,1-bis(5-carboxyl-2-furyl) ketone, and the hexyl diester of 1,1-bis(5-carboxyl-2-furyl)methane were synthesized from furfural and evaluated for their plasticizing abilities toward PVC, by the application of dynamic mechanical thermal analysis and [di(2-ethylhexyl) phthalate] as a standard of reference. © 1995 John Wiley & Sons, Inc.  相似文献   
110.
A review of isolates of Neisseria meningitidis and other laboratory evidence of meningococcal infection was carried out for the period 1990-1995. Thirty-three patients with evidence of meningococcal disease were identified over the six year period. Group B organisms were the most commonly identified, but an increase in Group C has occurred and is almost equal in number. Data from clinical, laboratory and public health sources should be centralized in a National Surveillance Centre.  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-23

京公网安备 11010802026262号