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   29064篇
  免费   2642篇
  国内免费   49篇
电工技术   1550篇
综合类   888篇
化学工业   11500篇
金属工艺   523篇
机械仪表   676篇
建筑科学   1321篇
矿业工程   212篇
能源动力   299篇
轻工业   2653篇
水利工程   188篇
石油天然气   80篇
武器工业   2篇
无线电   1041篇
一般工业技术   5002篇
冶金工业   2047篇
原子能技术   125篇
自动化技术   3648篇
  2023年   730篇
  2022年   473篇
  2021年   887篇
  2020年   833篇
  2019年   743篇
  2018年   776篇
  2017年   529篇
  2016年   851篇
  2015年   1021篇
  2014年   1128篇
  2013年   2114篇
  2012年   1001篇
  2011年   1026篇
  2010年   1277篇
  2009年   1379篇
  2008年   899篇
  2007年   871篇
  2006年   691篇
  2005年   631篇
  2004年   636篇
  2003年   536篇
  2002年   526篇
  2001年   374篇
  2000年   278篇
  1999年   307篇
  1998年   582篇
  1997年   416篇
  1996年   427篇
  1995年   388篇
  1994年   333篇
  1993年   408篇
  1992年   325篇
  1991年   253篇
  1990年   280篇
  1989年   295篇
  1988年   267篇
  1987年   274篇
  1986年   280篇
  1985年   269篇
  1984年   299篇
  1983年   266篇
  1982年   250篇
  1981年   321篇
  1980年   255篇
  1979年   279篇
  1977年   248篇
  1976年   252篇
  1975年   286篇
  1973年   431篇
  1972年   256篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
This paper explores the linkage between the entrepreneurial orientation of established firms and the development of radical innovation. Through five case studies in firms involved in radical innovation, three propositions are developed, suggesting that proactiveness, risk‐taking and autonomy stimulate the development of radical innovation, whereas competitive aggressiveness does not necessarily do so, as radical innovations are directed towards the creation of entirely new arenas of business, where existing competitors are not present.  相似文献   
2.
3.
4.
In advancement of Pyrosil®‐technology a new kind of precursor delivery was developed, build and tested on real substrates. A Lab‐demonstrator was build to demonstrate the resources of the technology.  相似文献   
5.
The Two-Dimensional Clifford-Fourier Transform   总被引:1,自引:0,他引:1  
Recently several generalizations to higher dimension of the Fourier transform using Clifford algebra have been introduced, including the Clifford-Fourier transform by the authors, defined as an operator exponential with a Clifford algebra-valued kernel. In this paper an overview is given of all these generalizations and an in depth study of the two-dimensional Clifford-Fourier transform of the authors is presented. In this special two-dimensional case a closed form for the integral kernel may be obtained, leading to further properties, both in the L 1 and in the L 2 context. Furthermore, based on this Clifford-Fourier transform Clifford-Gabor filters are introduced. AMS subject classification numbers: 42B10, 30G35 Fred Brackx received a diploma degree in mathematics from Ghent University, Belgium, in 1970 and a Ph.D. degree in mathematics from the same university in 1973. Since 1984 he is professor for mathematical analysis at Ghent University and currently he is leading the Clifford Research Group. His main interests are function theory and functional analysis for functions with values in quaternion and Clifford algebras. The research covers Clifford distributions, generalized Fourier, Radon and Hilbert transforms, orthogonal polynomials and multi-dimensional wavelets. Nele De Schepper received a diploma degree in mathematics from Ghent University, Belgium, in 2001. Since then she holds an assistantship at the Department of Mathematical Analysis of Ghent University and is a member of the Clifford Research Group. Her main interests are function theory and functional analysis for functions with values in Clifford algebras. The research covers generalized Fourier transforms, orthogonal polynomials and multi-dimensional wavelets. Frank Sommen received a diploma degree in mathematics from Ghent University, Belgium, in 1978, a Ph.D. degree in mathematics from the same university in 1980, and a habilitation degree in mathematical analysis in 1984. From 1978 until 1999 he was at the National Fund for Scientific Research (Flanders). Since 2000 he holds a Research professorship at Ghent University. His main interests are function theory and functional analysis for functions with values in quaternion and Clifford algebras. The research covers Clifford distributions, generalized Fourier, Radon and Hilbert transforms, orthogonal polynomials and multi-dimensional wavelets, algebraic analysis, hyperfunctions and radial algebra.  相似文献   
6.
This paper presents an approach to assist authors during the authoring of multimedia presentations. We extend the existing authoring support by integrating processes of topic identification, content collection and discourse structure building in a single environment. This integration allows identification of the context of the authoring process. Our approach combines this process context awareness with explicit domain and discourse knowledge to steer system suggestions. We evaluate our approach with an experimental system prototype.  相似文献   
7.
A cohort of 2nd-grade students provided comparisons of academic and social competence based on school retention/promotion decisions. Sample groups were (a) retained, (b) at risk for retention, (c) special education, and (d) promoted. Findings suggested most children with academic deficiencies are identified by schools early and are sorted into educational treatments differing in intensity that represent a continuum of competence. The authors provide empirical evidence counter to the assumptions that retained students have the requisite ability to catch up and have more problem behaviors than other low-achieving students. The relevance of high-stakes test scores for promotion/retention decisions and the parallels between schools' implementation of retention policy and implementation of regulations for identifying children with disabilities are included in the discussion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
8.
9.
A direct method is described for computing a hysteresis point (double turning point) corresponding to a cusp point of a system ofn nonlinear equations inn variables depending on two parameters. By addition of two equations a minimally extended system ofn+2 nonlinear equations is constructed for which the hysteresis point is an isolated solution. An efficient implementation of Newton's method is presented not requiring evaluations of second derivatives of the original problem. Two numerical examples show the efficiency of theQ-quadratically convergent method.  相似文献   
10.
Ob Betriebsvereinbarungen im Sinne des § 4 Abs. 1 BDSG eine „andere Rechtsvorschrift” sind und damit die Regelungen des BDSG einschr?nken dürfen, geh?rt zu den Standardfragen des praktischen Arbeitnehmerdatenschutzes. Die Autoren befürworten eine weite betriebliche Regelungskompetenz, beschr?nken diese aber zum Schutz der Arbeitnehmer durch eine Reihe datenschutzrechtlicher Mindestanforderungen, die Betriebsvereinbarungen einzuhalten haben.  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