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   11089篇
  免费   924篇
  国内免费   13篇
电工技术   85篇
综合类   6篇
化学工业   2720篇
金属工艺   136篇
机械仪表   344篇
建筑科学   502篇
矿业工程   26篇
能源动力   239篇
轻工业   2237篇
水利工程   86篇
石油天然气   20篇
无线电   807篇
一般工业技术   2158篇
冶金工业   714篇
原子能技术   26篇
自动化技术   1920篇
  2024年   39篇
  2023年   161篇
  2022年   137篇
  2021年   371篇
  2020年   319篇
  2019年   311篇
  2018年   444篇
  2017年   456篇
  2016年   560篇
  2015年   477篇
  2014年   613篇
  2013年   1127篇
  2012年   985篇
  2011年   775篇
  2010年   573篇
  2009年   550篇
  2008年   588篇
  2007年   512篇
  2006年   458篇
  2005年   309篇
  2004年   276篇
  2003年   247篇
  2002年   237篇
  2001年   147篇
  2000年   126篇
  1999年   111篇
  1998年   153篇
  1997年   126篇
  1996年   91篇
  1995年   90篇
  1994年   80篇
  1993年   72篇
  1992年   45篇
  1991年   33篇
  1990年   23篇
  1989年   23篇
  1988年   28篇
  1987年   19篇
  1986年   26篇
  1985年   31篇
  1984年   25篇
  1983年   18篇
  1982年   23篇
  1981年   18篇
  1980年   18篇
  1979年   23篇
  1978年   12篇
  1977年   11篇
  1976年   17篇
  1973年   13篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Currently, most of the information available in the Web is adapted primarily for human consumption, but there is so much information that can no longer be processed by a person in a reasonable time, either in digital or physical formats. To solve this problem, the idea of the Semantic Web arose. The Semantic Web deals with adding machine-readable information to Web pages. Ontologies represent a very important element of this web, as they provide a valid and robust structure to represent knowledge based on concepts, relations, axioms, etc. The need for overcoming the bottleneck provoked by the manual construction of ontologies has generated several studies and research on obtaining semiautomatic methods to learn ontologies. In this sense, this paper proposes a new ontology learning methodology based on semantic role labeling from digital Spanish documents. The method makes it possible to represent multiple semantic relations specially taxonomic and partonomic ones in the standardized OWL 2.0. A set of experiments has been performed with the approach implemented in educational domain that show promising results.  相似文献   
22.
23.
24.
Incorporation of ions in the active layer of organic semiconductor devices may lead to attractive device properties like enhanced injection and improved carrier transport. In this paper, we investigate the effect of the salt concentration on the operation of light‐emitting electrochemical cells, using experiments and numerical calculations. The current density and light emission are shown to increase linearly with increasing ion concentration over a wide range of concentrations. The increasing current is accompanied by an ion redistribution, leading to a narrowing of the recombination zone. Hence, in absence of detrimental side reactions and doping‐related luminescence quenching, the ion concentration should be as high as possible.  相似文献   
25.
Zhao SB  Becker JJ  Gagné MR 《Organometallics》2011,30(15):3926-3929
A high-yielding fluorination of (triphos)Pt-R(+) has been achieved using an array of F(+) sources, with XeF(2) yielding R-F in minutes. The C-F coupling proved to be a stereoretentive process that proceeds via a concerted reductive elimination from a putative dicationic Pt(IV) center. The larger the steric congestion of the (triphos)Pt-C(sp3) (+) complexes, the more efficient the fluorination, seemingly a result of sterically accelerated C-F reductive elimination along with simultaneous deceleration of its competing processes (β-H elimination).  相似文献   
26.
27.
28.
29.
This work presents a multiscale strong discontinuity approach to tackle key challenges in modeling localization behavior in granular media: accommodation of discontinuities in the kinematic fields, and direct linkage to the underlying grain-scale information. Assumed enhanced strain (AES) concepts are borrowed to enhance elements for post-localization analysis, but are reformulated within a recently-proposed hierarchical multiscale computational framework. Unlike classical AES methods, where material properties are usually constants or assumed to evolve with some arbitrary phenomenological laws, this framework provides a bridge to extract evolutions of key material parameters, such as friction and dilatancy, based on grain scale computational or experimental data. More importantly, the phenomenological softening modulus typically used in AES methods is no longer required. Numerical examples of plane strain compression tests are presented to illustrate the applicability of this method and to analyze its numerical performance.  相似文献   
30.
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