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   501640篇
  免费   7669篇
  国内免费   2416篇
电工技术   9718篇
技术理论   5篇
综合类   1312篇
化学工业   79893篇
金属工艺   20709篇
机械仪表   15055篇
建筑科学   12436篇
矿业工程   3242篇
能源动力   11413篇
轻工业   46952篇
水利工程   5617篇
石油天然气   11698篇
武器工业   258篇
无线电   54150篇
一般工业技术   96872篇
冶金工业   90853篇
原子能技术   11583篇
自动化技术   39959篇
  2021年   4244篇
  2019年   3758篇
  2018年   6431篇
  2017年   6392篇
  2016年   6938篇
  2015年   4881篇
  2014年   8078篇
  2013年   21792篇
  2012年   13278篇
  2011年   17786篇
  2010年   14426篇
  2009年   15893篇
  2008年   16871篇
  2007年   16901篇
  2006年   14870篇
  2005年   13408篇
  2004年   12255篇
  2003年   11681篇
  2002年   11788篇
  2001年   11723篇
  2000年   11005篇
  1999年   11005篇
  1998年   25353篇
  1997年   18756篇
  1996年   14526篇
  1995年   11087篇
  1994年   10084篇
  1993年   9824篇
  1992年   7694篇
  1991年   7462篇
  1990年   7320篇
  1989年   7380篇
  1988年   7043篇
  1987年   6068篇
  1986年   6050篇
  1985年   6902篇
  1984年   6655篇
  1983年   6134篇
  1982年   5587篇
  1981年   5902篇
  1980年   5556篇
  1979年   5675篇
  1978年   5643篇
  1977年   6238篇
  1976年   8013篇
  1975年   5090篇
  1974年   4854篇
  1973年   4881篇
  1972年   4195篇
  1971年   3842篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
Fefelov  S. A.  Kazakova  L. P.  Bogoslovskiy  N. A.  Bylev  A. B.  Yakubov  A. O. 《Semiconductors》2020,54(4):450-453
Semiconductors - The current–voltage characteristics measured on Ge2Sb2Te5 thin films in the current mode are studied. The effect of multilevel recording is established when applying...  相似文献   
65.
Powder Metallurgy and Metal Ceramics - The infiltration of aluminum melts into porous metal skeletons produced by powder metallurgy methods, including 3D printing, under a pressure gradient was...  相似文献   
66.
As a solid state joining process, ultrasonic spot welding has been proven to be a promising technique for joining copper alloys. However, challenges still remain in employing ultrasonic spot welding to join copper alloys. This article comprehensively reviews the current state of ultrasonic spot welding of copper alloys with a number of critical issues including materials flow, plastic deformation, temperature distribution, vibration, relative motion, vertical displacement, interface friction coefficient, online monitoring technique, coupled with the macrostructure and microstructure, the mechanical properties and electrical conductivity. In addition, the future trends in this field are provided.  相似文献   
67.
68.
Theoretical Foundations of Chemical Engineering - A set of measures to establish the technology for manufacturing highly active sources of γ radiation with an active part from...  相似文献   
69.
Metallurgical and Materials Transactions B - The quality requirements of aluminum products are steadily increasing, and the presence of non-metallic inclusions have a large impact on the quality of...  相似文献   
70.
Upper Barremian – Lower Aptian inner platform “Urgonian” limestones in the Mont de Vaucluse region, SE France, consist of alternating metre-scale microporous and tight intervals. This paper focuses on the influence of structural deformation on the reservoir properties of the Urgonian limestone succession in a study area near the town of Rustrel. Petrographic, petrophysical and structural data were recovered from five fully-cored boreholes, from the walls of a 100 m long underground tunnel, and from a 50 m long transect at a nearby outcrop. The data allowed reservoir property variations in the Urgonian limestones to be studied from core to reservoir scale. Eleven Reservoir Rock Types (RRTs) were identified based on petrographic features (texture, grain size), reservoir properties (porosity, permeability), and the frequency of structural discontinuities such as fractures, faults and stylolites. Tight and microporous reservoir rock types were distinguished. Tight reservoir rock types were characterised by early cementation of intergranular pore spaces and by the presence of frequent structural discontinuities. By contrast microporous reservoir rock types contained preserved intragranular microporosity and matrix permeability, but had very few structural discontinuities. Observed vertical alternations of microporous and tight rock types are interpreted to have been controlled by the early diagenesis of the Urgonian carbonates. Deformation associated with regional-scale tectonic phases, including Albian – Cenomanian “Durancian” uplift (∼105 to 96 Ma) and Pyrenean compression (∼55 to 25 Ma), resulted in the modification of the initial petrophysical properties of the Urgonian limestones. An early diagenetic imprint conditioned both the intensity of structural deformations and the associated circulations of diagenetic and meteoric fluids. Evolution of the Reservoir Rock Types is therefore linked both to the depositional conditions and to subsequent phases of structural deformation.  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