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   746934篇
  免费   9676篇
  国内免费   1928篇
电工技术   13528篇
综合类   641篇
化学工业   116469篇
金属工艺   29453篇
机械仪表   23733篇
建筑科学   17549篇
矿业工程   4736篇
能源动力   19708篇
轻工业   64029篇
水利工程   8406篇
石油天然气   16559篇
武器工业   44篇
无线电   83789篇
一般工业技术   148663篇
冶金工业   130950篇
原子能技术   16879篇
自动化技术   63402篇
  2021年   6703篇
  2020年   5028篇
  2019年   6414篇
  2018年   10961篇
  2017年   11157篇
  2016年   11882篇
  2015年   7586篇
  2014年   12771篇
  2013年   34879篇
  2012年   20289篇
  2011年   27853篇
  2010年   22169篇
  2009年   24663篇
  2008年   25308篇
  2007年   25012篇
  2006年   22050篇
  2005年   20024篇
  2004年   19096篇
  2003年   18700篇
  2002年   17890篇
  2001年   17787篇
  2000年   16796篇
  1999年   16990篇
  1998年   39347篇
  1997年   28254篇
  1996年   21898篇
  1995年   16791篇
  1994年   15038篇
  1993年   14738篇
  1992年   11252篇
  1991年   10767篇
  1990年   10599篇
  1989年   10235篇
  1988年   9881篇
  1987年   8684篇
  1986年   8402篇
  1985年   9747篇
  1984年   8846篇
  1983年   8378篇
  1982年   7568篇
  1981年   7713篇
  1980年   7277篇
  1979年   7312篇
  1978年   7105篇
  1977年   7898篇
  1976年   9889篇
  1975年   6330篇
  1974年   6056篇
  1973年   6187篇
  1972年   5165篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Journal of Communications Technology and Electronics - Abstract—The two-dimensional diffraction problem of a plane polarized TM-wave on two identical solid silver nanocylinders is considered....  相似文献   
12.
Hassan  Lovelu  Khan  K. A. 《Microsystem Technologies》2020,26(3):1031-1041

The efficiency of any electric cell or battery is very important. To keep it in mind it has been studied the columbic efficiency, voltaic efficiency and energy efficiency of a PKL (Pathor Kuchi Leaf) Quasi Voltaic Cell or Modified Voltaic Cell. It was found that the columbic efficiency data illustrated that this efficiency was lower comparing to other efficiencies may be the absence of salt bridge or separator between the electrodes. Because, our designed and fabricated PKL cell does not have any salt bridge. So that the internal resistance is lower than the traditional voltaic cell and as a result more current was found. The voltage and current changes with time and I–V characteristics for PKL unit cell, module, panel and array have also been studied. It is shown that the voltaic and energy efficiency have been studied. However, the highest efficiency was obtained for 40% PKL sap with 5% secondary salt in 55% aqueous solution, which implies that the concentration of PKL juice can play an important role regarding efficiency. It was also found that the average energy efficiency was 97.43% and it was also found that the average voltaic efficiency was 57.29%. Finally, morphological study FESEM (Field Emission Scanning Electron Microscopy) has also been performed. It is seen that the results confirmed that Zn was deposited on the Cu surface during the electro deposition process in PKL solution. Using AAS, it has been measured the concentration of [Cu2+] as a reactant ion and the concentration of [Zn2+] as a product ion those have been tabulated and graphically discussed. The variation of pH has also been studied with time and which was also tabulated and graphically discussed.

  相似文献   
13.
Photonic Network Communications - Optical packet switching is a prominent technology proposing not only a reduction in the energy consumption by the elimination of numerous...  相似文献   
14.
15.
16.
17.
18.

Stability constants and formation enthalpies of supramolecular complexes of crown ethers and their cyclic and acyclic analogues are determined on the basis of experimental data obtained by different physicochemical methods in the terms of a general approach developed and implemented in the ChemEqui software package. The established regularities of variation of stability of complexes are discussed as dependent on the ligand structure, nature of the cation, solvent, and anion. The applicability of the suggested method of determining complexation selectivity is shown for multicomponent equilibria in solutions.

  相似文献   
19.
A layer-by-layer analysis of the structures, the phase compositions, and the defect substructures of differentially hardened rails has been carried by optical and transmission electron microscopy. It is found that the material volume of the rail head fillet is cooled faster than the volume located along the central axis.  相似文献   
20.
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