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   217602篇
  免费   20255篇
  国内免费   11687篇
电工技术   14830篇
技术理论   13篇
综合类   15673篇
化学工业   33788篇
金属工艺   12561篇
机械仪表   14188篇
建筑科学   16446篇
矿业工程   7103篇
能源动力   6410篇
轻工业   17122篇
水利工程   4593篇
石油天然气   12161篇
武器工业   2151篇
无线电   25478篇
一般工业技术   24686篇
冶金工业   10234篇
原子能技术   2727篇
自动化技术   29380篇
  2024年   1173篇
  2023年   4126篇
  2022年   7902篇
  2021年   10403篇
  2020年   7821篇
  2019年   6055篇
  2018年   6754篇
  2017年   7557篇
  2016年   6778篇
  2015年   9354篇
  2014年   11601篇
  2013年   13822篇
  2012年   15548篇
  2011年   16187篇
  2010年   14142篇
  2009年   13372篇
  2008年   12985篇
  2007年   12277篇
  2006年   12064篇
  2005年   10044篇
  2004年   6865篇
  2003年   5475篇
  2002年   4938篇
  2001年   4511篇
  2000年   4203篇
  1999年   4409篇
  1998年   3517篇
  1997年   2965篇
  1996年   2769篇
  1995年   2240篇
  1994年   1816篇
  1993年   1319篇
  1992年   1072篇
  1991年   801篇
  1990年   578篇
  1989年   484篇
  1988年   376篇
  1987年   259篇
  1986年   220篇
  1985年   135篇
  1984年   117篇
  1983年   89篇
  1982年   92篇
  1981年   72篇
  1980年   76篇
  1979年   32篇
  1978年   25篇
  1977年   24篇
  1976年   26篇
  1951年   19篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
A technique for SiO2 formation by liquid-phase deposition (LPD) at nearly room temperature for low-temperature processed (LTP) polysilicon thin-film transistor (poly-Si TFT) was developed. LPD SiO2 film with a lower P-etch rate shows a dense structure. LPD SiO2 also exhibits good electrical characteristics. LTP poly-Si thin-film transistors (TFTs) with LPD SiO 2 as the gate insulator have been fabricated and investigated. Their characteristics indicate performance adequate for their use as pixel transistors in liquid crystal displays (LCDs)  相似文献   
32.
33.
The use of the analytically decoupled near-tip displacement solutions as an alternative approach, is presented in this paper for the efficient finite element evaluation of the decoupled weight functions for an orthotropic 2-D crack. This alternative approach has been validated by directly comparing the prior weight function results with a symmetric mesh approach in the crack-tip neighborhood, and indirectly by comparing the calculated stress intensity factors (KI(II)) values using the computed weight functions with available KI(II) solutions of the 2-D mixed mode orthotropic cracks. In addition, this approach with analytically decoupled near-tip displacement solutions for calculating weight functions at all locations, can facilitate further extension of weight function evaluations to a more general 2-D anisotropic crack.  相似文献   
34.
There is no good method to measure the shape and the strain distributions of a structure changing with time. We have previously proposed the Fourier transform grid method (FTGM) to measure the three-dimensional shape and surface strain distributions of stationary objects by analysing the two-dimensional grating images recorded with two cameras. In the stereoscopic method, it is very important to determine the accurate geometric parameters of the camera system. In this paper, the positions and the directions of cameras are accurately determined using the FTGM applied to images of a reference object on which a two-dimensional grating is drawn. Applications for analysing shape and strain distributions of vibrating rubber plates and a moving human skin are shown.  相似文献   
35.
In this paper, we address agent coordination from a dynamic systems perspective and propose a dynamic coordination model, which is inspired by biological metabolic systems. A new coordination mechanism through dynamic local adjustment (CDLA) is presented, and coordination is achieved when every agent utilizes explicitly the global system dynamics and performs iteratively a dynamic local adjustment procedure. The CDLA mechanism is investigated in an example multiagent shop floor system. The results show that the example manufacturing process is well-coordinated and the coordination approach is practically applicable and effective  相似文献   
36.
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   
37.
La doping effects on intergrowth Bi2WO6–Bi3TiNbO9 ferroelectric ceramics were studied by X-ray diffraction, electron probe microanalysis and dielectric spectroscopy. It was found that the La3+ distribution, ferroelectric phase transition and dielectric relaxation behavior are apparently affected by La doping. With increasing La3+ content, the site of dopant ion varies, the grain growth of Bi5TiNbWO15 is restrained, the Curie temperature is reduced and broadened. Furthermore, two dielectric relaxation loss peaks were observed both in temperature and frequency spectra. The calculated relaxation parameters revealed the oxygen vacancy related to the relaxation process.  相似文献   
38.
在聚全氟乙丙烯(FEP)中添加 TiO_2和 Al_2O_3,通过热压成型的方法制备了 FEP/TiO_2复合材料和 FEP/Al_2O_3复合材料,研究了氧化物添加量对复合材料介电常数、介电损耗和高频击穿性能的影响。结果表明,随氧化物含量的增加,复合材料的介电常数和介电损耗均增加;在同一添加量下,TiO_2对复合体系的介电性能影响较大。FEP/TiO_2复合材料的高频击穿性能随 TiO_2含量的增加而下降,在 TiO_2含量为4.0%(质量分数,下同)时,复合材料的损伤阈值已降为 FEP 材料损伤阈值的48.9 %。而 FEP/Al_2O_3复合材料的高频击穿性能随 Al_2O_3含量的增加而升高,当 Al_2O_3含量为1.2%时,复合材料的损伤阈值已增大到 FEP 材料损伤阈值的2倍,达到313 J/m~2。  相似文献   
39.
利用电机学理论分析了影响电机起动转矩、起动电流、最大转矩和最小转矩的因素。  相似文献   
40.
An anti-plane, semi-infinite crack in polarized ceramics is analyzed using the theory of elastic dielectrics with electric field gradient. The effects of electric field gradient on electromechanical fields around the crack is examined.  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