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   402651篇
  免费   5345篇
  国内免费   1349篇
电工技术   7563篇
综合类   314篇
化学工业   59500篇
金属工艺   16423篇
机械仪表   13488篇
建筑科学   8347篇
矿业工程   2154篇
能源动力   11520篇
轻工业   28455篇
水利工程   4261篇
石油天然气   7914篇
武器工业   17篇
无线电   49213篇
一般工业技术   82959篇
冶金工业   74946篇
原子能技术   9181篇
自动化技术   33090篇
  2022年   2296篇
  2021年   3872篇
  2020年   2938篇
  2019年   3796篇
  2018年   6476篇
  2017年   6473篇
  2016年   6916篇
  2015年   4315篇
  2014年   7131篇
  2013年   20026篇
  2012年   11405篇
  2011年   15259篇
  2010年   12137篇
  2009年   13707篇
  2008年   14045篇
  2007年   13809篇
  2006年   12412篇
  2005年   11111篇
  2004年   10504篇
  2003年   10416篇
  2002年   9827篇
  2001年   9732篇
  2000年   9134篇
  1999年   9521篇
  1998年   24324篇
  1997年   16707篇
  1996年   12798篇
  1995年   9516篇
  1994年   8363篇
  1993年   8380篇
  1992年   6054篇
  1991年   5693篇
  1990年   5679篇
  1989年   5317篇
  1988年   5043篇
  1987年   4419篇
  1986年   4299篇
  1985年   4812篇
  1984年   4421篇
  1983年   3994篇
  1982年   3654篇
  1981年   3729篇
  1980年   3428篇
  1979年   3326篇
  1978年   3334篇
  1977年   3750篇
  1976年   4847篇
  1975年   2850篇
  1974年   2663篇
  1973年   2730篇
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
771.
Consideration is given to the possibility of controlling the efficiency of the process of superdeep penetration of a high-velocity microstriker flux into metal obstacles due to the employment of ballast elements in the jet and to additional supply of energy in compression by an explosive charge along the external perimeter.  相似文献   
772.
Experimental data on the pulsed laser radiation confinement in compensated GaAs and ZnSe with deep impurity levels are reported for the laser wavelength λ=1.55 μm and a pulse repetition frequency of up to 100 kHz. It is demonstrated that an increase in the pulse repetition rate is accompanied by a decrease in the energy confinement threshold and by an increase in the radiation attenuation coefficient. These effects are explained by the accumulation of nonequilibrium charge carriers related to a dependence of the recombination time constant on the concentration of free impurity centers.  相似文献   
773.
Heath  L.S. Ramakrishnan  N. 《Computer》2002,35(7):41-45
Fusing computing and biology expertise, bioinformatics software provides a powerful tool for organizing and mining the vast amounts of data genetics researchers are accumulating. As life scientists and computational scientists interact to create useful bioinformatics software systems, several themes or lessons recur. We identify seven themes: the nature of biological data; data storage, analysis and retrieval; computational modeling and simulation; biologically meaningful information integration; data mining; image processing and visualization; and closing the loop  相似文献   
774.
Adaptive motion control using neural network approximations   总被引:1,自引:0,他引:1  
In this paper, we present a new adaptive technique for tracking control of mechanical systems in the presence of friction and periodic disturbances. Radial Basis Functions (RBFs) are used to compensate for the effects of nonlinearly occurring parameters in the friction and periodic disturbance model. Theoretical analysis, such as stability and transient performance, is provided. Furthermore, the performance of the adaptive RBF controller and its non-adaptive counterpart are compared.  相似文献   
775.
Consideration was given to the decision making procedures based on the fuzzy messages of experts whose preferences on the set of collective decisions can also be fuzzy.  相似文献   
776.
The effect of misalignment on the electrical properties of anisotropic conductive film (ACF) joints is investigated in this work. It is found that along with the increase of misalignment, the connection resistance of ACF joints increases. When the misalignment in x-direction is less than 5 μm, the increase rate of connection resistance is quite large. Then, along with the severity of misalignment, the increase rate becomes smaller. Finally, when the misalignment is close to 20 μm, the increase rate rises again. The Holm's electric contact theory is used for understanding the connection resistance variation. On the other hand, with the increase of misalignment in x-direction, the insulation resistance between ACF joints decreases. If the misalignment exceeded 10 μm, the decrease is prominent for the Ni particle ACF joints. This phenomenon can be explained by the effect of dielectric damage of the epoxy.Computer programs are also developed to calculate the variation of the probability of open and shorting after misalignment and predicate the maximum misalignment tolerance. The results show that the open and shorting probability increase abruptly after misalignment. On the view of pad parameters, the open probability is mainly related to the pad area, while the pads gap is critical to the shorting probability. Large pads gap (small pad width) can reduce the shorting probability obviously. On the other hand, enlarging the pad area by increasing pad length decreases the open probability significantly. So comparing to square shape pad, rectangle shape pad can reduce the failure probability greatly.  相似文献   
777.
778.
779.
Recent developments in rubber-toughened structural acrylic adhesives now offer sheet steel fabricators the opportunity to replace conventional metal fastening techniques such as spot welding with lower cost, durable, more versatile structural adhesive bonding. These developments, in particular much improved ability to bond oily/waxy surfaces common to the motor car industry and improved retention of fracture toughness after exposure to paint stoving temperatures, are discussed in this paper.  相似文献   
780.
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