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   435689篇
  免费   6341篇
  国内免费   1527篇
电工技术   7429篇
综合类   335篇
化学工业   65463篇
金属工艺   17762篇
机械仪表   13636篇
建筑科学   10283篇
矿业工程   2673篇
能源动力   11227篇
轻工业   38913篇
水利工程   4833篇
石油天然气   9479篇
武器工业   27篇
无线电   51617篇
一般工业技术   86841篇
冶金工业   77655篇
原子能技术   9578篇
自动化技术   35806篇
  2021年   3683篇
  2020年   2780篇
  2019年   3487篇
  2018年   5995篇
  2017年   6035篇
  2016年   6606篇
  2015年   4172篇
  2014年   7055篇
  2013年   19679篇
  2012年   11720篇
  2011年   15914篇
  2010年   12608篇
  2009年   14081篇
  2008年   14619篇
  2007年   14551篇
  2006年   13052篇
  2005年   11893篇
  2004年   11195篇
  2003年   10992篇
  2002年   10423篇
  2001年   10857篇
  2000年   9913篇
  1999年   10416篇
  1998年   25155篇
  1997年   17612篇
  1996年   13381篇
  1995年   10182篇
  1994年   8875篇
  1993年   8990篇
  1992年   6653篇
  1991年   6386篇
  1990年   6154篇
  1989年   5976篇
  1988年   5882篇
  1987年   4903篇
  1986年   4884篇
  1985年   5771篇
  1984年   5282篇
  1983年   4910篇
  1982年   4484篇
  1981年   4504篇
  1980年   4374篇
  1979年   4267篇
  1978年   4127篇
  1977年   4526篇
  1976年   5485篇
  1975年   3679篇
  1974年   3452篇
  1973年   3622篇
  1972年   2999篇
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
91.
Metallurgical and Materials Transactions A - Hybrid nanocomposites have potential as wear-resistant materials. However, synthesizing these nanocomposites by conventional molten state methods result...  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.
95.
Magnetic MnFe2O4 nanopowders were synthesized by an original solvothermal method in the absence and in the presence of tetra-n-butylammonium bromide (TBAB) and Tween 80 (TW) as surfactants. Manganese ferrite/polyaniline (PANI) hybrid materials were synthesized by in situ polymerization of aniline on the surface of MnFe2O4 using ammonium persulfate as oxidant. The purpose of the study was to investigate the influence of the two surfactants on the properties of the MnFe2O4 powders and of their composites with PANI. The specific surface area, the cumulative surface area of pores and the cumulative volume of pores are influenced by the nature of surfactant in case of MnFe2O4 powders and are higher by comparison to those of the MnFe2O4/PANI hybrid materials. The values of saturation magnetization in case of MnFe2O4 powders are higher than those of the hybrid materials and are not influenced by the surfactant nature. These features revealed that MnFe2O4 powders can be efficiently used as adsorbents for the purification of wastewaters. The values of the electrical conductivity of the composites exhibit a significant increase in comparison to the MnFe2O4 powders and depend on the surfactant nature. The highest value of electrical conductivity was achieved by the composite obtained using Tween 80 as surfactant (σDC = 54.5·10?5S?m?1) which was close to that of PANI (σDC = 61.2·10?5 S?m?1). The fact that the magnetic and electric properties of the synthesized MnFe2O4/PANI composites can be changed by design, demonstrate the high potential of these materials to be used in magneto-electric applications.  相似文献   
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.
100.
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