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   171369篇
  免费   1424篇
  国内免费   195篇
电工技术   2689篇
综合类   119篇
化学工业   26433篇
金属工艺   9554篇
机械仪表   5781篇
建筑科学   3066篇
矿业工程   1887篇
能源动力   2783篇
轻工业   9035篇
水利工程   2746篇
石油天然气   8696篇
武器工业   12篇
无线电   14910篇
一般工业技术   38835篇
冶金工业   29015篇
原子能技术   7045篇
自动化技术   10382篇
  2018年   3033篇
  2017年   3132篇
  2016年   3410篇
  2015年   1714篇
  2014年   3035篇
  2013年   6559篇
  2012年   4431篇
  2011年   5598篇
  2010年   4551篇
  2009年   5060篇
  2008年   5113篇
  2007年   5014篇
  2006年   4300篇
  2005年   3955篇
  2004年   3765篇
  2003年   3648篇
  2002年   3447篇
  2001年   3419篇
  2000年   3262篇
  1999年   3194篇
  1998年   7332篇
  1997年   5356篇
  1996年   3930篇
  1995年   3021篇
  1994年   2694篇
  1993年   2843篇
  1992年   2294篇
  1991年   2346篇
  1990年   2454篇
  1989年   2354篇
  1988年   2345篇
  1987年   2198篇
  1986年   2282篇
  1985年   2337篇
  1984年   2235篇
  1983年   2157篇
  1982年   2001篇
  1981年   2222篇
  1980年   2087篇
  1979年   2276篇
  1978年   2441篇
  1977年   2449篇
  1976年   3126篇
  1975年   2251篇
  1974年   2307篇
  1973年   2346篇
  1972年   2160篇
  1971年   1909篇
  1970年   1698篇
  1969年   1628篇
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
1.
Journal of Materials Science: Materials in Electronics - The ZnO and TiO2 nanopowders have been prepared by means of the pulsed laser reactive ablation of metallic (Zn, Ti) targets. The Structural,...  相似文献   
2.
Inorganic Materials - We have studied the effect of annealing on the chemical and physical properties of mineral-like host matrices for immobilization of the rare-earth–actinide fraction from...  相似文献   
3.
Semiconductors - The results of the effect of irradiation with Ar ions on the structural, electrophysical, and optical characteristics of ultraviolet Cr/4H-SiC photodetectors in the spectral range...  相似文献   
4.
In the present work it is found that the pyrotechnic composition VS-2 can be initiated with flash lamps IFC-500 and EVIS. VS-2 pyrotechnic composition contains 90% of mercury(Ⅱ) 5-hydrazinotetrazolate perchlorate and 10% of optically transparent copolymer of 2-methyl-5-vinyltetrazole and methacrylic acid (PVMT). We have found that the flash lamps make it possible to initiate combustion of VS-2 composition with its transition to detonation both in cylindrical charges placed in brass caps of 5 mm diameter and 2 mm high, and film charges with 10 mm×80 mm in size and surface weights of 60 mg·cm-2 and 90 mg·cm-2, showing ignition delay times 10 μs and 3 μs, respectively. We also measured detonation velocities for VS-2 composition film charges, which were 4375-4505 m·s-1 (of the charge being surface mass 60 mg·cm-2) and 4221-4281 m·s-1 (of the charge being surface mass 90 mg·cm-2) and their blasting action on the aluminum plate. The depths of the normal shock wave imprints at the charge-barrier interface were 0.6-0.7 mm (for surface mass of the film charges 60 mg·cm-2) and 1.2-1.3 mm (for surface mass of the film charges 90 mg·cm-2).  相似文献   
5.
Strength of Materials - The effect of the creep of materials of a structure on the nature of the contact interaction between its elements during long-term operation is investigated. The problem of...  相似文献   
6.
Journal of Communications Technology and Electronics - A modified resonator method for determining the complex permittivity of materials based on the theory of small perturbations where a resonator...  相似文献   
7.
Journal of Computer and Systems Sciences International - The replacement of complex technical system elements is optimized using a genetic algorithm. Its various operators are analyzed and modified...  相似文献   
8.
Compositional analysis of boron carbide on nanometer length scales to examine or interpret atomic mechanisms, for example, solid-state amorphization or grain-boundary segregation, is challenging. This work reviews advancements in high-resolution microanalysis to characterize multiple generations of boron carbide. First, ζ-factor microanalysis will be introduced as a powerful (scanning) transmission electron microscopy ((S)TEM) analytical framework to accurately characterize boron carbide. Three case studies involving the application of ζ-factor microanalysis will then be presented: (1) accurate stoichiometry determination of B-doped boron carbide using ζ-factor microanalysis and electron energy loss spectroscopy, (2) normalized quantification of silicon grain-boundary segregation in Si-doped boron carbide, and (3) calibration of a scanning electron microscope X-ray energy-dispersive spectroscopy (XEDS) system to measure compositional homogeneity differences of B/Si-doped arc-melted boron carbides in the as-melted and annealed conditions. Overall, the improvement and application of advanced analytical tools have helped better understand processing–microstructure–property relationships and successfully manufacture high-performance ceramics.  相似文献   
9.
Russian Engineering Research - Systems are considered for the dehydration of petroleum so as to separate water–petroleum emulsions. In particular, the low-temperature microwave (UHF)...  相似文献   
10.
Cybernetics and Systems Analysis - A new information software technology has been created, which is implemented in a software package and is destined to perform a wide, easily supplemented set of...  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