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   309773篇
  免费   3746篇
  国内免费   713篇
电工技术   6193篇
综合类   560篇
化学工业   46740篇
金属工艺   10324篇
机械仪表   8819篇
建筑科学   7899篇
矿业工程   862篇
能源动力   8568篇
轻工业   31084篇
水利工程   2534篇
石油天然气   3669篇
武器工业   8篇
无线电   39707篇
一般工业技术   58442篇
冶金工业   56664篇
原子能技术   5458篇
自动化技术   26701篇
  2021年   2275篇
  2019年   2140篇
  2018年   3607篇
  2017年   3449篇
  2016年   3538篇
  2015年   2540篇
  2014年   4439篇
  2013年   14271篇
  2012年   7363篇
  2011年   10111篇
  2010年   7900篇
  2009年   9131篇
  2008年   9600篇
  2007年   9577篇
  2006年   8504篇
  2005年   7889篇
  2004年   7759篇
  2003年   7497篇
  2002年   7337篇
  2001年   7546篇
  2000年   7206篇
  1999年   7549篇
  1998年   17662篇
  1997年   12838篇
  1996年   10098篇
  1995年   7874篇
  1994年   7206篇
  1993年   6905篇
  1992年   5287篇
  1991年   5068篇
  1990年   4934篇
  1989年   4783篇
  1988年   4673篇
  1987年   3886篇
  1986年   4007篇
  1985年   4718篇
  1984年   4275篇
  1983年   4022篇
  1982年   3603篇
  1981年   3761篇
  1980年   3457篇
  1979年   3419篇
  1978年   3225篇
  1977年   3816篇
  1976年   4848篇
  1975年   2780篇
  1974年   2661篇
  1973年   2675篇
  1972年   2216篇
  1971年   1963篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
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   
133.
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   
134.
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   
135.
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   
136.
137.
138.
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   
139.
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   
140.
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