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   522730篇
  免费   5462篇
  国内免费   1644篇
工业技术   529836篇
  2021年   4593篇
  2019年   4411篇
  2018年   12962篇
  2017年   13339篇
  2016年   12029篇
  2015年   5543篇
  2014年   9002篇
  2013年   20704篇
  2012年   14872篇
  2011年   21891篇
  2010年   18363篇
  2009年   19146篇
  2008年   19733篇
  2007年   20602篇
  2006年   13141篇
  2005年   13582篇
  2004年   12762篇
  2003年   12400篇
  2002年   11380篇
  2001年   10899篇
  2000年   10635篇
  1999年   10255篇
  1998年   22143篇
  1997年   16348篇
  1996年   12498篇
  1995年   9826篇
  1994年   8832篇
  1993年   8984篇
  1992年   6987篇
  1991年   6925篇
  1990年   6822篇
  1989年   6710篇
  1988年   6351篇
  1987年   5918篇
  1986年   5844篇
  1985年   6362篇
  1984年   5971篇
  1983年   5677篇
  1982年   5279篇
  1981年   5432篇
  1980年   5369篇
  1979年   5329篇
  1978年   5533篇
  1977年   5856篇
  1976年   7163篇
  1975年   4909篇
  1974年   4958篇
  1973年   4992篇
  1972年   4348篇
  1971年   3933篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Strength of Materials - Methodical aspects of experimental investigation of brittle materials under local edge loading by scratching the specimen surface with a Rockwell indenter to its edge...  相似文献   
92.
Measurement Techniques - A method is proposed for transferring the unit of mean power of laser radiation by means of measuring high-intensity power (kilowatts), with the possibility of constant...  相似文献   
93.
Puzanov  A. S.  Obolenskiy  S. V.  Kozlov  V. A. 《Semiconductors》2020,54(8):946-950
Semiconductors - On the basis of the Monte Carlo algorithm, a method for calculating the energy spectrum of hot nonequilibrium electrons and holes in the track of a primary recoil atom after being...  相似文献   
94.
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   
95.
96.
97.
Here we report some recent biophysical issues on the preparation of solute-filled lipid vesicles and their relevance to the construction of “synthetic cells.” First, we introduce the “semi-synthetic minimal cells” as the liposome-based cell-like systems, which contain a minimal number of biomolecules required to display simple and complex biological functions. Next, we focus on recent aspects related to the construction of synthetic cells. Emphasis is given to the interplay between the methods of synthetic cell preparation and the physics of solute encapsulation. We briefly introduce the notion of structural and compositional “diversity” in synthetic cell populations.  相似文献   
98.
99.
Programming and Computer Software - Image segmentation using a hierarchical sequence of piecewise constant approximations that minimally differ from the original image in terms of the total squared...  相似文献   
100.
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