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   557857篇
  免费   7089篇
  国内免费   984篇
电工技术   10369篇
综合类   461篇
化学工业   85490篇
金属工艺   23202篇
机械仪表   18284篇
建筑科学   12227篇
矿业工程   4306篇
能源动力   14298篇
轻工业   44842篇
水利工程   6913篇
石油天然气   14886篇
武器工业   39篇
无线电   59897篇
一般工业技术   115266篇
冶金工业   95600篇
原子能技术   14688篇
自动化技术   45162篇
  2021年   5199篇
  2020年   4011篇
  2019年   5267篇
  2018年   9207篇
  2017年   9419篇
  2016年   9832篇
  2015年   6028篇
  2014年   10247篇
  2013年   26106篇
  2012年   15776篇
  2011年   21099篇
  2010年   16974篇
  2009年   18823篇
  2008年   19073篇
  2007年   18769篇
  2006年   16288篇
  2005年   14746篇
  2004年   13991篇
  2003年   13570篇
  2002年   12680篇
  2001年   12221篇
  2000年   11480篇
  1999年   11286篇
  1998年   26996篇
  1997年   19473篇
  1996年   14992篇
  1995年   11917篇
  1994年   10758篇
  1993年   10512篇
  1992年   8239篇
  1991年   8023篇
  1990年   7941篇
  1989年   7670篇
  1988年   7391篇
  1987年   6658篇
  1986年   6461篇
  1985年   7329篇
  1984年   6641篇
  1983年   6362篇
  1982年   5717篇
  1981年   5850篇
  1980年   5586篇
  1979年   5690篇
  1978年   5637篇
  1977年   6149篇
  1976年   7656篇
  1975年   5071篇
  1974年   4867篇
  1973年   4944篇
  1972年   4257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.
Journal of Engineering Physics and Thermophysics - The generalized nonlocal thermoelastic model in the context of Eringen’s nonlocal elasticity is applied to investigate the...  相似文献   
3.
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   
4.
Chemistry and Technology of Fuels and Oils - This article considers the alternatives for treatment of the raffinate produced at a unit for the extraction of benzene-containing fractions and the...  相似文献   
5.
In the current work, numerical simulations are achieved to study the properties and the characteristics of fluid flow and heat transfer of (Cu–water) nanofluid under the magnetohydrodynamic effects in a horizontal rectangular canal with an open trapezoidal enclosure and an elliptical obstacle. The cavity lower wall is grooved and represents the heat source while the obstacle represents a stationary cold wall. On the other hand, the rest of the walls are considered adiabatic. The governing equations for this investigation are formulated, nondimensionalized, and then solved by Galerkin finite element approach. The numerical findings were examined across a wide range of Richardson number (0.1 ≤ Ri ≤ 10), Reynolds number (1 ≤ Re ≤ 125), Hartmann number (0 ≤ Ha ≤ 100), and volume fraction of nanofluid (0 ≤ φ ≤ 0.05). The current study's findings demonstrate that the flow strength increases inversely as the Reynolds number rises, which pushes the isotherms down to the lower part of the trapezoidal cavity. The Nuavg rises as the Ri rise, the maximum Nuavg = 10.345 at Ri = 10, Re = 50, ϕ = 0.05, and Ha = 0; however, it reduces with increasing Hartmann number. Also, it increase by increasing ϕ, at Ri = 10, the Nuavg increased by 8.44% when the volume fraction of nanofluid increased from (ϕ = 0–0.05).  相似文献   
6.
7.
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   
8.
Russian Engineering Research - A mathematical model of a heat store based on melting of the working medium is verified by means of an experiment. The model describes a heat store containing a...  相似文献   
9.
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   
10.
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   
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