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   286475篇
  免费   2272篇
  国内免费   914篇
电工技术   4997篇
综合类   242篇
化学工业   41589篇
金属工艺   17607篇
机械仪表   11731篇
建筑科学   5492篇
矿业工程   2847篇
能源动力   4904篇
轻工业   15324篇
水利工程   4326篇
石油天然气   10969篇
武器工业   51篇
无线电   26058篇
一般工业技术   66220篇
冶金工业   42783篇
原子能技术   9514篇
自动化技术   25007篇
  2021年   2150篇
  2019年   2131篇
  2018年   10890篇
  2017年   11392篇
  2016年   8588篇
  2015年   2815篇
  2014年   4217篇
  2013年   9289篇
  2012年   8240篇
  2011年   14396篇
  2010年   12912篇
  2009年   12447篇
  2008年   12553篇
  2007年   14138篇
  2006年   5995篇
  2005年   8047篇
  2004年   6835篇
  2003年   6427篇
  2002年   5226篇
  2001年   4706篇
  2000年   4597篇
  1999年   4347篇
  1998年   10115篇
  1997年   7280篇
  1996年   5376篇
  1995年   4250篇
  1994年   3780篇
  1993年   3888篇
  1992年   3087篇
  1991年   3178篇
  1990年   3258篇
  1989年   3121篇
  1988年   3050篇
  1987年   2859篇
  1986年   2930篇
  1985年   3031篇
  1984年   2820篇
  1983年   2716篇
  1982年   2497篇
  1981年   2730篇
  1980年   2574篇
  1979年   2753篇
  1978年   2904篇
  1977年   3046篇
  1976年   3855篇
  1975年   2679篇
  1974年   2704篇
  1973年   2728篇
  1972年   2528篇
  1971年   2260篇
排序方式: 共有10000条查询结果,搜索用时 15 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.
The thermodynamics modeling of a Reiner–Philippoff-type fluid is essential because it is a complex fluid with three distinct probable modifications. This fluid model can be modified to describe a shear-thinning, Newtonian, or shear-thickening fluid under varied viscoelastic conditions. This study constructs a mathematical model that describes a boundary layer flow of a Reiner–Philippoff fluid with nonlinear radiative heat flux and temperature- and concentration-induced buoyancy force. The dynamical model follows the usual conservation laws and is reduced through a nonsimilar group of transformations. The resulting equations are solved using a spectral-based local linearization method, and the accuracy of the numerical results is validated through the grid dependence and convergence tests. Detailed analyses of the effects of specific thermophysical parameters are presented through tables and graphs. The study reveals, among other results, that the buoyancy force, solute and thermal expansion coefficients, and thermal radiation increase the overall wall drag, heat, and mass fluxes. Furthermore, the study shows that amplifying the space and temperature-dependent heat source parameters allows fluid particles to lose their cohesive force and, consequently, maximize flow and heat transfer.  相似文献   
5.
Theoretical Foundations of Chemical Engineering - The reaction of nickel(II) hydroxide and a mixed ammonia–carbonate solution to form nickel(II) aqua–ammonia complexes is studied in the...  相似文献   
6.
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   
7.
Cybernetics and Systems Analysis - It is noted that fuzzy methods are widely used to substantiate rational decisions in multi-criteria analysis of complex systems since the operating conditions of...  相似文献   
8.
Chemistry and Technology of Fuels and Oils - The review examines biomass of animal origin in terms of a potential renewable raw material for obtaining CO2-neutral fuel unaffecting the carbon...  相似文献   
9.
Strength of Materials - Methods of elastic solutions and interchangeable elasticity parameters for solving nonlinear boundary value problems of mechanics are considered, making it possible to...  相似文献   
10.
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   
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