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   503294篇
  免费   4542篇
  国内免费   1283篇
电工技术   8482篇
综合类   2523篇
化学工业   73157篇
金属工艺   25661篇
机械仪表   17697篇
建筑科学   9970篇
矿业工程   4785篇
能源动力   9268篇
轻工业   26401篇
水利工程   6734篇
石油天然气   14745篇
武器工业   35篇
无线电   54076篇
一般工业技术   109820篇
冶金工业   76896篇
原子能技术   14044篇
自动化技术   54825篇
  2021年   3770篇
  2019年   3748篇
  2018年   20977篇
  2017年   20145篇
  2016年   17310篇
  2015年   4863篇
  2014年   7643篇
  2013年   17247篇
  2012年   13985篇
  2011年   23152篇
  2010年   19456篇
  2009年   18374篇
  2008年   20024篇
  2007年   20681篇
  2006年   11426篇
  2005年   11407篇
  2004年   11230篇
  2003年   10933篇
  2002年   10056篇
  2001年   9813篇
  2000年   9528篇
  1999年   9293篇
  1998年   22193篇
  1997年   15590篇
  1996年   11951篇
  1995年   9094篇
  1994年   8130篇
  1993年   8279篇
  1992年   6282篇
  1991年   6247篇
  1990年   6325篇
  1989年   6041篇
  1988年   5686篇
  1987年   5157篇
  1986年   5128篇
  1985年   5571篇
  1984年   5227篇
  1983年   4882篇
  1982年   4599篇
  1981年   4781篇
  1980年   4561篇
  1979年   4657篇
  1978年   4845篇
  1977年   5157篇
  1976年   6329篇
  1975年   4346篇
  1974年   4379篇
  1973年   4384篇
  1972年   3849篇
  1971年   3481篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Ohtoshi  T. 《Electronics letters》1987,23(11):570-571
A theoretical expression is derived for the far fields of semiconductor lasers with coated facets. It is shown that the far fields are different for uncoated, antireflection-coated and high-reflection-coated lasers. The correction factor for the far fields is shown to depend on the transmission coefficient of the facets.  相似文献   
112.
113.
Validity on the well-known Onsager reciprocal relations L 12=L 21 is verified in the kinetic theory of gases taking into account mass and heat transfer near the surface. Using an analytical solution to the ellipsoidal statistical equation (providing for the true Prandtl number), it is demonstrated that the Onsager relations are obeyed, at least to within exponential corrections of the type exp(−1/Kn) in the Knudsen number.  相似文献   
114.
It is established that the capillary rise of a liquid has an oscillatory character, in contrast to the commonly accepted opinion that a vertical capillary is filled at a monotonically varying velocity. The value of the tangential shear stress arising in an ascending liquid is evaluated for ethyl alcohol and distilled water.  相似文献   
115.
The purpose and current construction status, at the Institute of Theoretical and Experimental Physics, of an experimental electronuclear setup, combining a pulsed proton linear accelerator (36 MeV, 0.5 mA) and a subcritical blanket thermal-power assembly 100 kW, are discussed. The main equipment is already available or is being built in industry. The setup can be used to investigate the dynamics of the interaction of a linac–driver and a subcritical reactor and problems concerning the accelerator–driver and the target–blanket assembly. The proton beams and neutron fluxes will be used for applied purposes. In the future it will be possible to increase substantially the current and energy of the proton beam.  相似文献   
116.
We propose an asynchronous structure for implementation on a SoC. An intersegment topological arrangement preserves parallelization and, through a so-called central arbiter, efficiently organizes communication with high signaling speed in the proposed structure. Researchers proposed the concept of segmenting buses primarily for multicomputer architectures. More recent approaches address on-chip implementation of segmented buses. We present an asynchronous segmented-bus architecture targeted for the modular design of high-performance SoC applications. The structure not only enables faster operation than a conventional bus system but also offers lower power consumption per transferred data item. This is possible because segmentation is realized in such a way that the majority of data transfers in the system are intrasegment transactions on relatively short wires with low or moderate capacitive loads.  相似文献   
117.
A.V. Kolobov  P. Fons 《Thin solid films》2007,515(19):7534-7537
We discuss specific features of Te-based compounds that made them the best materials for the phase-change data storage. It is demonstrated that the phase-change recording is due to a switch of Ge atoms between octahedral and tetrahedral symmetry positions within the Te face-centered cubic lattice. It is this nature of the transition that makes the Te-based media fast and stable. The driving force for this transition is also discussed. The chapter is concluded by introduction of a concept of the super-resolution near-field structure (super-RENS) disc that allows to reduce a bit size well below the diffraction limit and makes 100 GB/disc storage a reality.  相似文献   
118.
119.
120.
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