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   509315篇
  免费   5947篇
  国内免费   1357篇
电工技术   9180篇
综合类   366篇
化学工业   76388篇
金属工艺   23755篇
机械仪表   17810篇
建筑科学   12074篇
矿业工程   3446篇
能源动力   11623篇
轻工业   40623篇
水利工程   5903篇
石油天然气   10986篇
武器工业   20篇
无线电   55645篇
一般工业技术   104560篇
冶金工业   86966篇
原子能技术   11800篇
自动化技术   45474篇
  2021年   3428篇
  2019年   3278篇
  2018年   12643篇
  2017年   13109篇
  2016年   10081篇
  2015年   4417篇
  2014年   6835篇
  2013年   19667篇
  2012年   13072篇
  2011年   21705篇
  2010年   18550篇
  2009年   19330篇
  2008年   19471篇
  2007年   21020篇
  2006年   12412篇
  2005年   14303篇
  2004年   12488篇
  2003年   11929篇
  2002年   10877篇
  2001年   10285篇
  2000年   9990篇
  1999年   10139篇
  1998年   24211篇
  1997年   17756篇
  1996年   13910篇
  1995年   10385篇
  1994年   9500篇
  1993年   9208篇
  1992年   7117篇
  1991年   6963篇
  1990年   6627篇
  1989年   6692篇
  1988年   6535篇
  1987年   5545篇
  1986年   5497篇
  1985年   6364篇
  1984年   6002篇
  1983年   5511篇
  1982年   5075篇
  1981年   5287篇
  1980年   5028篇
  1979年   5031篇
  1978年   5114篇
  1977年   5855篇
  1976年   7627篇
  1975年   4591篇
  1974年   4381篇
  1973年   4405篇
  1972年   3776篇
  1971年   3472篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Russian Journal of Non-Ferrous Metals - The synthesis and sintering of the (AlN)x(SiC)1 – x solid solution have been studied under conditions of self-propagating high-temperature synthesis...  相似文献   
92.
N. Boukortt  S. Patan&#;  G. Crupi 《SILICON》2020,12(7):1585-1591
The miniaturization has become a key word for advanced integrated circuits over the last few years. It is within this context that the fin field effect tra  相似文献   
93.
94.
An alternative Equivalent Electrical Circuit for Proton Exchange Membrane Fuel Cells is modelled in this study. Both I–V characteristics and H2 consumptions corresponding to generated power under load and no-load conditions are investigated. For this purpose, H2 consumptions and I–V characteristics of three different sized PEMFCs are tested. There is a very good harmony between the model results and measured values (relative error %0.7, %6.4 and %2.5 for FC-A, FC-B and FC-C respectively). In the proposed model current passes only on parallel resistance and not on serial resistance at no-load condition. Thus, a FC with higher parallel resistance should be preferred. Another key output of this study is that based on the proposed model, performance comparison of FCs can be performed with the parameters defined in this work. Proposals made in this study can easily be used for performance analysis of FCs under for both steady state and transient analysis.  相似文献   
95.
96.
Potential mGAT4 inhibitors derived from the lead substance (S)-SNAP-5114 have been synthesized and characterized for their inhibitory potency. Variations from the parent compound included the substitution of one of its aromatic 4-methoxy and 4-methoxyphenyl groups, respectively, with a more polar moiety, including a carboxylic acid, alcohol, nitrile, carboxamide, sulfonamide, aldehyde or ketone function, or amino acid partial structures. Furthermore, it was investigated how the substitution of more than one of the aromatic 4-methoxy groups affects the potency and selectivity of the resulting compounds. Among the synthesized test substances (S)-1-{2-[(4-formylphenyl)bis(4-methoxyphenyl)-methoxy]ethyl}piperidine-3-carboxylic acid, that features a carbaldehyde function in place of one of the aromatic 4-methoxy moieties of (S)-SNAP-5114, was found to have a pIC50 value of 5.89±0.07, hence constituting a slightly more potent mGAT4 inhibitor than the parent substance while showing comparable subtype selectivity.  相似文献   
97.
98.
99.
An automated system for integrated electrophysical and optical studies of semiconductor nanoheterostructures, which operates in a wide temperature range from 15 to 475 K, is designed. The setup is intended to measure the temperature and frequency admittance and electroluminescence spectra of light-emitting diode and laser chips formed on substrates of diameter up to 50.2 mm, and the distribution of parameters over the wafer. The setup includes the closed-cycle helium cryogenic station, LCR meter, and temperature controller. The characterization results of nanoheterostructures with InGaN/GaN multiple quantum wells, which are used for creating highly efficient white and blue light-emitting diodes, are presented.  相似文献   
100.
The influence of the thermal cycling conditions on the thermal-cycling creep of a TN-1 alloy and the related irreversible deformations is studied. The conditions under which an anomalous increase in the irreversible deformations begins are determined. The structural mechanism of the irreversible deformations of an equiatomic alloy is shown to be analogous to the structural mechanism of metal creep at high temperatures: it predominantly has a dislocation character. It is proposed to use the effect of anomalous increase in the deformation of materials with reversible martensitic transformations for forming parts made of these materials at low temperatures.  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