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   389054篇
  免费   5410篇
  国内免费   1702篇
电工技术   7639篇
综合类   349篇
化学工业   55848篇
金属工艺   17040篇
机械仪表   11265篇
建筑科学   9510篇
矿业工程   1321篇
能源动力   10287篇
轻工业   36850篇
水利工程   3332篇
石油天然气   4174篇
武器工业   6篇
无线电   47519篇
一般工业技术   72111篇
冶金工业   79948篇
原子能技术   7654篇
自动化技术   31313篇
  2021年   2521篇
  2019年   2504篇
  2018年   4131篇
  2017年   4060篇
  2016年   4352篇
  2015年   3295篇
  2014年   5503篇
  2013年   17475篇
  2012年   9374篇
  2011年   13219篇
  2010年   10619篇
  2009年   12074篇
  2008年   12572篇
  2007年   12591篇
  2006年   11283篇
  2005年   10486篇
  2004年   10038篇
  2003年   9753篇
  2002年   9710篇
  2001年   9171篇
  2000年   8233篇
  1999年   9208篇
  1998年   25083篇
  1997年   17585篇
  1996年   13282篇
  1995年   10278篇
  1994年   8916篇
  1993年   8736篇
  1992年   6209篇
  1991年   6079篇
  1990年   5587篇
  1989年   5486篇
  1988年   5388篇
  1987年   4628篇
  1986年   4589篇
  1985年   5409篇
  1984年   4853篇
  1983年   4452篇
  1982年   4138篇
  1981年   4189篇
  1980年   3925篇
  1979年   3798篇
  1978年   3728篇
  1977年   4575篇
  1976年   6500篇
  1975年   3209篇
  1974年   3137篇
  1973年   3162篇
  1972年   2634篇
  1971年   2413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.
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.
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.
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   
7.
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   
8.
Traditional West African pearl millet couscous products are popular; however, their preparation is laborious, time-consuming and energy-demanding, involving agglomeration, steaming, drying and sieving steps. In this study, a process was developed to produce millet couscous using a high pressure, high temperature and low-cost single-screw extruder. The innovation was to directly process the cooked low-moisture extrudate to a couscous product by drying and milling to the appropriate particle size (ranging between 1 and 2 mm). Throughput for the traditional process as prepared for commercial sale is 50 kg per day, but with the same amount of labour, the extrusion process yields ~350 kg per day. A consumer sensory study held in Niamey (Niger) showed that the extruded millet couscous was comparable to traditional couscous, though this was dependent on selection of the proper millet variety. This novel extrusion process could stimulate small- to medium-scale manufacturing of couscous and couscous-type products in West Africa.  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.
Wireless Personal Communications - Nowadays, Wireless Sensor Networks (WSNs) is enhancing for different applications. Simultaneously, energy consumption for processing the tasks in most of the...  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