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   468001篇
  免费   5670篇
  国内免费   2063篇
电工技术   8848篇
技术理论   5篇
综合类   1242篇
化学工业   74781篇
金属工艺   23473篇
机械仪表   16338篇
建筑科学   10170篇
矿业工程   4898篇
能源动力   9032篇
轻工业   33444篇
水利工程   6348篇
石油天然气   16178篇
武器工业   269篇
无线电   44793篇
一般工业技术   102015篇
冶金工业   73635篇
原子能技术   14619篇
自动化技术   35646篇
  2021年   4836篇
  2019年   4438篇
  2018年   7954篇
  2017年   8208篇
  2016年   8722篇
  2015年   5434篇
  2014年   9032篇
  2013年   20009篇
  2012年   13836篇
  2011年   17676篇
  2010年   14234篇
  2009年   15495篇
  2008年   16357篇
  2007年   16139篇
  2006年   13733篇
  2005年   12028篇
  2004年   11236篇
  2003年   10646篇
  2002年   10605篇
  2001年   10454篇
  2000年   10009篇
  1999年   9450篇
  1998年   18969篇
  1997年   14434篇
  1996年   10999篇
  1995年   8587篇
  1994年   7991篇
  1993年   8019篇
  1992年   6585篇
  1991年   6451篇
  1990年   6586篇
  1989年   6464篇
  1988年   6139篇
  1987年   5651篇
  1986年   5560篇
  1985年   6092篇
  1984年   5933篇
  1983年   5622篇
  1982年   5143篇
  1981年   5317篇
  1980年   5109篇
  1979年   5436篇
  1978年   5551篇
  1977年   5673篇
  1976年   6882篇
  1975年   5056篇
  1974年   4972篇
  1973年   5001篇
  1972年   4400篇
  1971年   4023篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
A magnetooptical method of measurement of viscosity, which is based on recording the optical response (induced by the magnetic-field pulses) of a two-layer system resulting from the sedimentation of ferroparticles dispersed in the liquid under study, has been proposed. The procedure has been described and the results of measurement of the rheokinetics of a number of media, including polymer compositions formed into a thin film, in heating, evaporation, and polymerization have been presented.  相似文献   
992.
A powerful concept to cope with resource limitations and information redundancy in wireless sensor networks is the use of collaboration groups to distill information within the network and suppress unnecessary activities. When the phenomena to be monitored have large geographical extents, it is not obvious how to define these collaboration groups. This article presents the application of geometric duality to form such groups for sensor selection and non-local phenomena tracking. Using a dual-space transformation, which maps a non-local phenomenon (e.g., the edge of a half-plane shadow) to a single point in the dual space and maps locations of distributed sensor nodes to a set of lines that partitions the dual space, one can turn off the majority of the sensors to achieve resource preservation without losing detection and tracking accuracy. Since the group so defined may consist of nodes that are far away in physical space, we propose a hierarchical architecture that uses a small number of computationally powerful nodes and a massive number of power constrained motes. By taking advantage of the continuity of physical phenomena and the duality principle, we can greatly reduce the power consumption in non-local phenomena tracking and extend the lifetime of the network.  相似文献   
993.
Studied the effects of variations in base rate (BR) information and temporal context on predictions of violence and hindsight bias (HB). 270 undergraduates estimated the likelihood of violent offenders committing another violent offense based upon fictitious case history information. Ss were given 1 of 2 population BRs of the likelihood of reoffending (30% or 70%) and a recidivism estimation question that was phrased either predictively, predictively with a given outcome of either recidivism or no recidivism, or postdictively. Although different offenders were perceived as differentially likely to reoffend, estimated likelihood of recidivism was affected by neither BR nor temporal phrasing of the estimation task. A 2nd study of 182 undergraduates, using shorter case histories, also found no BR effect. HB effects were weak and inconsistent in both studies. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
994.
995.
Algorithms are proposed that construct first integrals and Lyapunov functions for stability analysis of stationary solutions of differential equations describing mechanical systems of linked bodies.Translated from Kibernetika i Sistemnyi Analiz, No. 1, pp. 138–148, January–February, 1992.  相似文献   
996.
997.
998.
999.
1000.
Mastication of gutta percha (trans-polyisoprene) resulted in the selective scission of molecules, producing a narrower distribution of lower molecular weights. The mechanical properties of the samples also underwent a significant change due to mastication. The greater the content of incompatible substances (salts and oxides) in commercial gutta percha. the more substantial were these effects. The atmosphere (air, N2, O2) in which the experiments were conducted yielded significantly different results. The decrease in molecular weight was far greater in an O2 atmosphere than under a current of nitrogen or air, owing to the combination of double bonds with O2.  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