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   5761篇
  免费   198篇
  国内免费   12篇
电工技术   62篇
综合类   1篇
化学工业   1140篇
金属工艺   100篇
机械仪表   90篇
建筑科学   324篇
矿业工程   21篇
能源动力   195篇
轻工业   539篇
水利工程   49篇
石油天然气   42篇
武器工业   1篇
无线电   324篇
一般工业技术   925篇
冶金工业   1114篇
原子能技术   30篇
自动化技术   1014篇
  2023年   34篇
  2022年   59篇
  2021年   90篇
  2020年   85篇
  2019年   76篇
  2018年   103篇
  2017年   84篇
  2016年   138篇
  2015年   102篇
  2014年   181篇
  2013年   377篇
  2012年   269篇
  2011年   351篇
  2010年   251篇
  2009年   218篇
  2008年   286篇
  2007年   257篇
  2006年   213篇
  2005年   209篇
  2004年   154篇
  2003年   146篇
  2002年   147篇
  2001年   87篇
  2000年   86篇
  1999年   94篇
  1998年   135篇
  1997年   130篇
  1996年   88篇
  1995年   96篇
  1994年   72篇
  1993年   89篇
  1992年   89篇
  1991年   55篇
  1990年   58篇
  1989年   59篇
  1988年   51篇
  1987年   52篇
  1986年   60篇
  1985年   74篇
  1984年   71篇
  1983年   76篇
  1982年   58篇
  1981年   51篇
  1980年   52篇
  1979年   76篇
  1978年   56篇
  1977年   54篇
  1976年   45篇
  1975年   44篇
  1973年   28篇
排序方式: 共有5971条查询结果,搜索用时 15 毫秒
21.
22.
The surface and interface properties of Pd0.9Cr0.1/SiC Schottky diode gas sensors both before and after annealing are investigated using Auger electron spectroscopy (AES), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). At room temperature the alloy reacted with SiC and formed PdxSi only in a very narrow interfacial region. After annealing for 250 h at 425°C, the surface of the Schottky contact area has much less silicon and carbon contamination than that found on the surface of an annealed Pd/SiC structure. Palladium silicides (PdxSi) formed at a broadened interface after annealing, but a significant layer of alloy film is still free of silicon and carbon. The chromium concentration with respect to palladium is quite uniform down to the deep interface region. A stable catalytic surface and a clean layer of Pd0.9Cr0.1 film are likely responsible for significantly improved device sensitivity.  相似文献   
23.
The authors highlight several possible ways in which the construction industry could lower present emissions of the greenhouse gas, carbon dioxide. It is an excellent discussion document and is recommended reading.  相似文献   
24.
25.
Two laboratory-scale plasma reactors, an alternating current (AC) energized ferroelectric (high dielectric ceramic) packed bed reactor and a nanosecond pulsed corona reactor, were constructed. This study was done to develop baseline engineering data to demonstrate the feasibility of the application of plasma reactors to the destruction of various volatile organic compounds (VOCs) at PPM levels. Complete destruction was obtained for toluene. Conversions of methylene chloride at 95% and trichlorotrifluoroethane (known as CFC-113) at 67% were achieved for the plasma reactors used. The conversion was dependent on the mean electron energy in the reactor and was also related to how strongly halogen species were bonded with carbon  相似文献   
26.
Abstract: Facility location and customer allocation problems are pervasive in industry and in the private sector. In this paper, we outline a new approach to solving these problems that avoids the need to resort to integer programming techniques. The approach exploits the mathematical structure of the problem as well as characteristics frequently found in applied location/allocation problems. Using this approach, large scale problems are readily solvable on personal computers. We illustrate the approach on a small example and provide computational results based on a real-world application of the technique. Extensions to include additional problem features are also discussed.  相似文献   
27.
28.
A neurostimulator application-specific integrated circuit (ASIC) with scalable circuitry that can stimulate 14 channels, has been developed for an epi-retinal vision prosthesis. This ASIC was designed to allow seven identical units to be connected to control up to 98 channels, with the ability to stimulate 14 electrodes simultaneously. The neurostimulator forms part of a vision prosthesis, designed to restore vision to patients who have lost their sight due to retinal diseases such as retinitis pigmentosa and macular degeneration. For charge balance, the neurostimulator was designed to stimulate with current sources and sinks operating together, and with the ability to drive a hexagonal mosaic of electrodes to reduce the electrical crosstalk that occurs when multiple bipolar stimulation sites are active simultaneously. A hexagonal mosaic of electrodes surrounds each stimulation site and has been shown to effectively isolate each site, increasing the ability to inject localized independent charge into multiple regions simultaneously.  相似文献   
29.
This study focuses on the visualization of a series of large earthquake simulations collectively called TeraShake. The simulation series aims to assess the impact of San Andreas Fault earthquake scenarios in Southern California. We discuss the role of visualization in gaining scientific insight and aiding unexpected discoveries.  相似文献   
30.
Noel D. Uri 《Applied Energy》1996,54(4):355-373
This study begins by asking whether fluctuations in the price of crude oil have affected agricultural employment in the USA. After reviewing previous assessments of the issue, the existence of an empirical relationship between agricultural employment and crude-oil price volatility is established using Granger causality. Subsequently, the nature of the relationship is estimated with the results suggesting that at least three full years are required before the measurable impacts of a percentage change in the real price of crude oil on the change in agricultural employment are exhausted. Finally, the structural stability of the functional relationship between the change in agricultural employment and the volatility of the price of crude oil, the percentage changes in expected net farm income, realized technological innovation, and the wage rate are examined.  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