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   23199篇
  免费   1062篇
  国内免费   323篇
电工技术   477篇
综合类   545篇
化学工业   4161篇
金属工艺   531篇
机械仪表   765篇
建筑科学   908篇
矿业工程   182篇
能源动力   626篇
轻工业   2328篇
水利工程   262篇
石油天然气   183篇
武器工业   27篇
无线电   2463篇
一般工业技术   2983篇
冶金工业   4815篇
原子能技术   172篇
自动化技术   3156篇
  2023年   135篇
  2022年   413篇
  2021年   565篇
  2020年   322篇
  2019年   406篇
  2018年   465篇
  2017年   441篇
  2016年   498篇
  2015年   411篇
  2014年   606篇
  2013年   1144篇
  2012年   892篇
  2011年   1106篇
  2010年   812篇
  2009年   876篇
  2008年   863篇
  2007年   870篇
  2006年   758篇
  2005年   637篇
  2004年   702篇
  2003年   916篇
  2002年   1217篇
  2001年   1023篇
  2000年   595篇
  1999年   564篇
  1998年   1688篇
  1997年   1015篇
  1996年   762篇
  1995年   508篇
  1994年   380篇
  1993年   404篇
  1992年   199篇
  1991年   160篇
  1990年   158篇
  1989年   147篇
  1988年   149篇
  1987年   124篇
  1986年   123篇
  1985年   167篇
  1984年   86篇
  1983年   90篇
  1982年   86篇
  1981年   112篇
  1980年   106篇
  1979年   61篇
  1978年   53篇
  1977年   139篇
  1976年   275篇
  1975年   54篇
  1973年   52篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
101.
On-body communications around the human torso are considered, using ultra-wideband transmissions. The velocity of the diffracted wave propagating around the body is extracted from frequency- domain spatial correlation analyses.  相似文献   
102.
103.
104.
A new version of the front-end application specific integrated circuit (ASIC) for co-planar-grid (CPG) sensors is presented. Compared to the first version, the ASIC is optimized for signal/noise performance, modified in peaking time, and it implements timing signals to measure the depth of interaction using the grids signals only. Experimental results using state-of the-art CPG sensors and different approaches for reducing the error due to electron trapping are reported. A new technique that makes use of the sum and difference of the grids signals is also presented.  相似文献   
105.
106.
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   
107.
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   
108.
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   
109.
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   
110.
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   
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