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   22904篇
  免费   1040篇
  国内免费   318篇
电工技术   498篇
综合类   545篇
化学工业   4134篇
金属工艺   551篇
机械仪表   807篇
建筑科学   925篇
矿业工程   181篇
能源动力   681篇
轻工业   2342篇
水利工程   261篇
石油天然气   186篇
武器工业   27篇
无线电   2573篇
一般工业技术   3185篇
冶金工业   3818篇
原子能技术   183篇
自动化技术   3365篇
  2023年   121篇
  2022年   217篇
  2021年   544篇
  2020年   355篇
  2019年   410篇
  2018年   486篇
  2017年   450篇
  2016年   498篇
  2015年   428篇
  2014年   654篇
  2013年   1213篇
  2012年   978篇
  2011年   1166篇
  2010年   887篇
  2009年   932篇
  2008年   912篇
  2007年   923篇
  2006年   791篇
  2005年   653篇
  2004年   752篇
  2003年   952篇
  2002年   1237篇
  2001年   1045篇
  2000年   618篇
  1999年   551篇
  1998年   1370篇
  1997年   897篇
  1996年   647篇
  1995年   441篇
  1994年   327篇
  1993年   363篇
  1992年   203篇
  1991年   156篇
  1990年   151篇
  1989年   147篇
  1988年   135篇
  1987年   120篇
  1986年   122篇
  1985年   162篇
  1984年   96篇
  1983年   100篇
  1982年   88篇
  1981年   109篇
  1980年   103篇
  1979年   64篇
  1978年   52篇
  1977年   102篇
  1976年   194篇
  1975年   52篇
  1973年   52篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
102.
Focused ion beam (FIB) and nano-probing were applied for failure analysis of three-dimensional stacked circuits with copper through-silicon-vias between the stacked chips. The failure analysis was done after high temperature storage and thermal cycling tests. Passive voltage contrast in FIB allowed to pinpoint the open sites. FIB cross-sections showed the presence of opens at the bottom of the copper vias. The failure cause was suspected to be an interlayer particle, which was confirmed by optical profilometry. Nano-probing was used on another sample to pinpoint the failure location through the measurement of the local resistance within the daisy chains. The failure was traced out to be related with surface contamination.  相似文献   
103.
The Y2O3: Yb3 , Er3 microstructures were fabricated by a hydrothermal method without surfactants.The microstructures structure was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM,KYKY 1000B).The up-conversion luminescence spectra were studied under 978 nm laser diode excitation.In Yb3 and Er3 codoped Y2 O3 microcrystals, the relative intensity of green emission became stronger as the morphology of sample changed from wires to films.  相似文献   
104.
This study provides a meta-analysis of research on the associations between relationship conflict, task conflict, team performance, and team member satisfaction. Consistent with past theorizing, results revealed strong and negative correlations between relationship conflict, team performance, and team member satisfaction. In contrast to what has been suggested in both academic research and introductory textbooks, however, results also revealed strong and negative (instead of the predicted positive) correlations between task conflict, team performance, and team member satisfaction. As predicted, conflict had stronger negative relations with team performance in highly complex (decision making, project, mixed) than in less complex (production) tasks. Finally, task conflict was less negatively related to team performance when task conflict and relationship conflict were weakly, rather than strongly, correlated. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
105.
The effect of the deposition rate on the structural and morphological properties of TiN and ZrN single layers and TiN/ZrN multilayers deposited by radiofrequency reactive magnetron sputtering has been studied. The total pressure was kept constant and the growth rate variation was obtained by small difference of nitrogen concentration in the fed gas. The decreasing deposition rate results in a structural change in the thin films from (111) orientation to (100) one. As consequence the surface morphology becomes smoother. Films roughness is strongly related with texture and it decreases with an increase in the (100) X-ray diffraction line intensity. In order to achieve a clear interpretation of our experimental results, the ratio between the N+ ions of the plasma and the atoms number reaching the substrate was considered. At high deposition rate with respect to the N+ concentration, the chemical potential of transition metal on (100) growth surface is higher than (111) one favouring the (111) orientation of the films. On the contrary, when the growth rate is low with respect to the nitrogen concentration, the chemical potential of transition metal on (111) growth surface is higher than the (100) one leading to a preferential growth in the (100) direction.  相似文献   
106.
Here we report synthesis and characterization of high quality samples of the superconducting system Mg1−x Al x B2, with a novel optimized preparation method, in a wide range of Al concentration. All the physical properties of the samples can be tuned continuously with increasing Al content. We have characterized the samples for their structural, morphological and magnetic properties with high resolution XRD, SEM-EDS and susceptibility measurements. We have prepared a large number of Al doped MgB2 in the range 0<x<0.57. All the samples are bulk superconductors and the critical temperature show a smooth and regular behavior as a function of x. This work was supported by European project 517039 “Controlling Mesoscopic Phase Separation” (COMEPHS) (2005). An erratum to this article can be found at  相似文献   
107.
Recent years have witnessed major governmental initiatives regarding critical infrastructure protection (CIP). During that same time, critical infrastructures (CIs) have undergone massive institutional restructuring under the headings of privatization, deregulation and liberalization. Little research has gone into understanding the interactions between these two developments. In this article, we outline the consequences of institutional restructuring for the changing ways in which CIs ensure the reliability and security of their networks and services. Neither Normal Accident Theory nor High‐Reliability Theory can account for reliability under these conditions. We then investigate the implications of these findings for CIP.  相似文献   
108.
109.
可实现性k-ε模型在水轮机流场计算中的应用   总被引:9,自引:1,他引:8  
本文针对目前水轮机转轮内部流场计算中存在的偏工况计算困难的问题,探讨了一种不同于标准k-ε模型的可实现性k-ε模型(Realizablek-ε在水轮机偏工况计算中的应用。文章首先对该模型的优点进行了分析。然后针对某混流式转轮进行了计算,计算与实验结果比较表明,二者在设计工况附近时十分接近;在小开底小流量下,对转轮的主要特征的预测也是成功的。但小开度下计算值与实测值之间的差别也表明,在水轮机偏工况计算中,该湍流模型有待进一步改进。  相似文献   
110.
框架结构焦仓的定向倒塌爆破   总被引:4,自引:1,他引:3  
徐顺香  陈德志 《爆破》2003,20(1):51-52,55
介绍了框架结构焦仓定向爆破拆除的设计与施工,着重介绍了爆破参烽的选取及安全防护措施。达到预期的爆破效果。  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