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   78203篇
  免费   1063篇
  国内免费   691篇
电工技术   1455篇
综合类   47篇
化学工业   11842篇
金属工艺   3526篇
机械仪表   2748篇
建筑科学   1764篇
矿业工程   514篇
能源动力   2036篇
轻工业   7165篇
水利工程   860篇
石油天然气   2323篇
武器工业   41篇
无线电   7637篇
一般工业技术   17032篇
冶金工业   12566篇
原子能技术   2663篇
自动化技术   5738篇
  2022年   585篇
  2021年   1045篇
  2020年   800篇
  2019年   885篇
  2018年   1715篇
  2017年   1685篇
  2016年   1915篇
  2015年   1080篇
  2014年   1708篇
  2013年   4072篇
  2012年   2492篇
  2011年   2975篇
  2010年   2530篇
  2009年   2799篇
  2008年   2714篇
  2007年   2622篇
  2006年   2244篇
  2005年   1960篇
  2004年   1873篇
  2003年   1817篇
  2002年   1734篇
  2001年   1759篇
  2000年   1754篇
  1999年   1643篇
  1998年   3790篇
  1997年   2704篇
  1996年   1980篇
  1995年   1546篇
  1994年   1345篇
  1993年   1375篇
  1992年   1005篇
  1991年   1058篇
  1990年   1086篇
  1989年   1058篇
  1988年   952篇
  1987年   884篇
  1986年   887篇
  1985年   949篇
  1984年   789篇
  1983年   777篇
  1982年   685篇
  1981年   699篇
  1980年   671篇
  1979年   653篇
  1978年   630篇
  1977年   781篇
  1976年   950篇
  1975年   584篇
  1974年   559篇
  1973年   554篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The results of investigations performed by specialists at Research and Design Institute of Electrical Technology together with other enterprises, institutes, and organizations concerning the formulation of a strategy for the development of nuclear power in Russia in the first half of the 21st century are presented. The individual stages of the work, key assumptions, ideas, and recommendations, on which the strategy is based, the initiatives which the President of the Russian Federation advanced at the millennium summit held at the United Nations, and the international INPRO project initiated by Russia are examined. It is concluded that innovative development and a transition to building as quickly as possible nuclear power objects that meet the requirements and demands of the new century are necessary. __________ Translated from Atomnaya énergiya,Vol. 103, No. 1, pp. 5–15, July, 2007.  相似文献   
992.
A semiconductor-based master-oscillator power-amplifier operating at 977 nm is demonstrated to emit more than 10 W continuous wave in a nearly diffraction limited beam with a narrow spectral bandwidth. The device consists of a distributed Bragg reflector laser and a flared amplifier monolithically integrated on a single chip  相似文献   
993.
994.
995.
Scholars who study close relationships often measure the same concept with both observational ratings and questionnaire items. In studies where this has been done, the correlations between the two measures have often been low, and one reason may be a "context by measurement" confound. Observational ratings are usually based on behaviors during a specific task, whereas most questionnaire responses are based on a broader context such as "during the past month." In 2001, a total of 292 young couples were videotaped during a discussion task and asked to report on their own behavior and that of their partner during the discussion task and during the past month. The data were configured as a multitrait, multimethod matrix, and the magnitudes of the correlations were estimated with confirmatory factor analysis. The resulting correlations between observer ratings and questionnaire reports of hostile behavior during the videotaped discussion were roughly twice the magnitude of the correlations between observer rating and questionnaire reports during the past month. This suggests that the correspondence between behavioral categories and the content of questionnaire items is greater than previous studies have indicated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
996.
We consider the problem of common linear copositive Lyapunov function existence for positive switched linear systems. In particular, we present a necessary and sufficient condition for the existence of such a function for switched systems with two constituent linear time-invariant systems. Several applications of this result are also given.  相似文献   
997.
For the system with a small parameter under nonlinearities, consideration was given to the problem of optimal speed. The values of the multivariable control actions are bounded in the Euclidean norm. The theorem of existence and asymptotic properties of the solution of this problem was proved. It underlies the algorithm to construct asymptotic arbitrary-order approximations to the optimal control.  相似文献   
998.
The basic design solutions and characteristics of the VBéR-300 reactor system for the power-generating units of 150–300 MW(e) nuclear power plants and regional nuclear heat-and-electricity plants are described. The reactor system implemented as a unit is based on the technologies and solutions used for marine nuclear power systems, which have been corroborated by experience in operating nuclear-powered icebreakers. The technical-economic advantages of floating power-generating units are substantiated. __________ Translated from Atomnaya énergiya, Vol. 102, No. 1, pp. 35–39, January, 2007.  相似文献   
999.
Using qualitative data, Blom and Monk (2003) derived a theory of why people choose to personalise the appearance of their PCs and mobile phones. This paper describes some quantitative data that provide some support for, and some modifications to, the theory. Individuals having personal home pages were recruited to fill in a questionnaire that assesses dispositions to personalise and its effects. In addition the 82 home pages were inspected to assess the extent of personalisation. This correlated significantly with the dispositions 'Frequency of Use' and 'Knowledge of Personalisation'. The questionnaire items corresponding to effects were factor analysed. A four-factor solution suggested item groupings similar, but not identical, to those used in the theory. There are significant positive correlations between the extent of personalisation and cognitive effects and enduring emotional effects. The value of quantitative data for confirming and refining a qualitative theory is discussed.  相似文献   
1000.
In the last years, there is carried out an intensive search for new molding mixtures capable of replacing sand-argillaceous mixtures whose properties have already been well studied. Unfortunately, the majority of them form a mold in the course of the hardening of a bonding agent, which requires creating a complex system for the regeneration of the used sand. In this connection, we investigated a waterless molding mixture with the use of organobentonite as the binder, which does not require any changes in the technological process of green-sand molding. The influence of the amount and composition of the solvent on the properties of waterless mixtures is estimated.  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