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   330721篇
  免费   2595篇
  国内免费   669篇
电工技术   4785篇
综合类   2406篇
化学工业   51364篇
金属工艺   19824篇
机械仪表   13035篇
建筑科学   6302篇
矿业工程   4317篇
能源动力   4956篇
轻工业   13199篇
水利工程   5321篇
石油天然气   13337篇
武器工业   28篇
无线电   29216篇
一般工业技术   78402篇
冶金工业   34686篇
原子能技术   11388篇
自动化技术   41419篇
  2021年   2756篇
  2019年   2737篇
  2018年   19574篇
  2017年   18764篇
  2016年   15817篇
  2015年   3639篇
  2014年   5532篇
  2013年   10250篇
  2012年   10346篇
  2011年   18103篇
  2010年   15388篇
  2009年   13529篇
  2008年   14777篇
  2007年   15465篇
  2006年   6459篇
  2005年   6722篇
  2004年   6560篇
  2003年   6428篇
  2002年   5652篇
  2001年   5042篇
  2000年   5110篇
  1999年   4309篇
  1998年   7226篇
  1997年   5860篇
  1996年   4475篇
  1995年   3666篇
  1994年   3438篇
  1993年   3631篇
  1992年   3229篇
  1991年   3386篇
  1990年   3487篇
  1989年   3371篇
  1988年   3277篇
  1987年   3263篇
  1986年   3158篇
  1985年   3317篇
  1984年   3254篇
  1983年   3146篇
  1982年   2995篇
  1981年   3048篇
  1980年   3071篇
  1979年   3259篇
  1978年   3492篇
  1977年   3463篇
  1976年   3914篇
  1975年   3212篇
  1974年   3294篇
  1973年   3342篇
  1972年   2987篇
  1971年   2756篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
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   
83.
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   
84.
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   
85.
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   
86.
87.
88.
89.
With the creation of balancing authorities by the North American Reliability Council that span large portions of the North American interconnection, and stringent requirements for real time monitoring of power system evolution, faster and more accurate state estimation algorithms that can efficiently handle systems of very large sizes are needed in the present environment. This paper presents a distributed state estimation algorithm suitable for large-scale power systems. Synchronized phasor measurements are applied to aggregate the voltage phase angles of each decomposed subsystem in the distributed state estimation solution. The aggregated state estimation solution is obtained from the distributed solution using a sensitivity analysis based update at chosen boundary buses. Placement of synchronized phasor measurements in the decomposed subsystems is also investigated in this paper. Test results on the IEEE 118-bus test bed are provided  相似文献   
90.
The hot blow forming of magnesium sheet offers significant opportunity for forming complex, lightweight parts for automotive applications. This paper characterizes the elevated-temperature formability of AZ31 magnesium sheet materials and the effect of processing conditions on the performance of these materials. In addition, magnesium sheet application development at General Motors Corporation is reviewed.  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