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   248974篇
  免费   1665篇
  国内免费   265篇
电工技术   4041篇
综合类   91篇
化学工业   40321篇
金属工艺   15143篇
机械仪表   10061篇
建筑科学   4175篇
矿业工程   3759篇
能源动力   3873篇
轻工业   9696篇
水利工程   4087篇
石油天然气   13006篇
武器工业   28篇
无线电   20186篇
一般工业技术   62747篇
冶金工业   32140篇
原子能技术   11134篇
自动化技术   16416篇
  2021年   2754篇
  2019年   2730篇
  2018年   5428篇
  2017年   5709篇
  2016年   6044篇
  2015年   3052篇
  2014年   5322篇
  2013年   10079篇
  2012年   7304篇
  2011年   8925篇
  2010年   7293篇
  2009年   8103篇
  2008年   8171篇
  2007年   7855篇
  2006年   6356篇
  2005年   5561篇
  2004年   5478篇
  2003年   5299篇
  2002年   5132篇
  2001年   4947篇
  2000年   4938篇
  1999年   4253篇
  1998年   7173篇
  1997年   5832篇
  1996年   4420篇
  1995年   3653篇
  1994年   3423篇
  1993年   3623篇
  1992年   3215篇
  1991年   3359篇
  1990年   3482篇
  1989年   3370篇
  1988年   3268篇
  1987年   3260篇
  1986年   3156篇
  1985年   3316篇
  1984年   3253篇
  1983年   3146篇
  1982年   2993篇
  1981年   3045篇
  1980年   3071篇
  1979年   3257篇
  1978年   3490篇
  1977年   3460篇
  1976年   3911篇
  1975年   3211篇
  1974年   3294篇
  1973年   3341篇
  1972年   2987篇
  1971年   2754篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
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   
113.
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   
114.
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   
115.
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   
116.
117.
118.
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   
119.
Sol–gel films are actively investigated during the last decade as possible candidates for environmentally friendly pre-treatments. However, the important drawback in this case is the lack of active corrosion protection and self-healing ability.  相似文献   
120.
A simulation of flow field and tracer homogenization was performed using the commercial CFD software FLUENT 6.1. The aim is to investigate the potential of CFD software to predict concentration distribution of added tracer in cylindrical vessels. The calculated results – dimensionless velocity profiles, power and pumping numbers, dimensionless concentration curves, and mixing times – were compared with experiments in stirred vessels. In Part I, the study was performed for vessels agitated by one or two impellers on a centric shaft. Two different impellers were used – a 6‐bladed 45° pitched blade turbine and a standard Rushton turbine. The standard k‐? turbulence model and multiple reference frames method were used for the simulations. The influence of the grid type was also investigated; three types of grid – a structured, unstructured and a special user‐defined grid – were studied.  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