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   102956篇
  免费   1485篇
  国内免费   1225篇
电工技术   1942篇
综合类   139篇
化学工业   10491篇
金属工艺   5462篇
机械仪表   3197篇
建筑科学   2035篇
矿业工程   159篇
能源动力   2966篇
轻工业   6089篇
水利工程   706篇
石油天然气   667篇
武器工业   15篇
无线电   15957篇
一般工业技术   21808篇
冶金工业   25285篇
原子能技术   1382篇
自动化技术   7366篇
  2022年   408篇
  2021年   700篇
  2020年   531篇
  2019年   681篇
  2018年   1138篇
  2017年   1095篇
  2016年   1179篇
  2015年   927篇
  2014年   1497篇
  2013年   4678篇
  2012年   2580篇
  2011年   3854篇
  2010年   3104篇
  2009年   3728篇
  2008年   3904篇
  2007年   4083篇
  2006年   3697篇
  2005年   3338篇
  2004年   3185篇
  2003年   3030篇
  2002年   2675篇
  2001年   2980篇
  2000年   2721篇
  1999年   3085篇
  1998年   9452篇
  1997年   6165篇
  1996年   4765篇
  1995年   3171篇
  1994年   2790篇
  1993年   2725篇
  1992年   1631篇
  1991年   1596篇
  1990年   1519篇
  1989年   1325篇
  1988年   1175篇
  1987年   864篇
  1986年   891篇
  1985年   921篇
  1984年   805篇
  1983年   699篇
  1982年   702篇
  1981年   688篇
  1980年   568篇
  1979年   477篇
  1978年   416篇
  1977年   535篇
  1976年   959篇
  1975年   301篇
  1974年   278篇
  1973年   257篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Yeom  H.J. Park  Y.C. Chang  Y.H. 《Electronics letters》2007,43(25):1410-1411
Presented is an eigen filter to remove autogenic electrical stimulation artefacts and M-waves while preserving the volitional electromyographic signal. The optimality of the eigen filter is shown, along with simulated and measured data to indicate its superior performance over conventional prediction error filters.  相似文献   
992.
Summary Fourier transform infrared spectroscopy and birefringence measurements have been used to study the changes in molecular orientation which occur on drawing of plasticized as compared to pure polystyrene (PS) at a temperature T=Tg+Cte. No influence of plasticizers on orientation can be detected whatever the interactions between small molecules and PS chains are. Comparison with previous results obtained on PS-poly(vinylmethyl ether) compatible blends confirms the importance of the macromolecular nature of the second component to enhance the friction coefficient leading to higher level of chain orientation.  相似文献   
993.
994.
本文用不同的测试技术和方法测定了锗酸铋(BGO)单晶的比热(300~800K)热膨胀系数(100~1100K)和导温系数(140~700K),进而导出了 BGO 单晶不同温度下的导热系数、定容比热、德拜温度和格虑内森数。本文还对 BGO 单晶热物理性质的变化规律作了理论解释。  相似文献   
995.
We describe planar buried heterostructure lasers which have low capacitance (lpF), large bandwidth (19GHz), high power (>20mW/facet) and high temperature operation (100°C). These lasers are very suitable for long-distance, highspeed digital and analogue signal transmission.  相似文献   
996.
Woodceramics Prepared from Wood Powder/Phenolated Wood Composite   总被引:2,自引:0,他引:2  
In this paper, composites were made from wood powder and its phenolated product, and then were carbonized into woodceramics. The effects of the content of the phenolated wood in the composites on the forming ability, size, density, compressive strength, volume electrical resistivity, and specific surface area of the woodceramics were investigated. It is suggested that in the preparation of woodceramics, phenolic resin can possibly be substituted totally by phenolated wood that is the main constituent of liquefied wood.  相似文献   
997.
New integrated optical devices combining an InGaAsP/InP HPT and an inner-stripe LED are proposed and their fabrication processes are described. The device functions of light amplification, optical bistability, and optical switching are demonstrated in the 1-μm wavelength region.  相似文献   
998.
In order to investigate the influence of puffer volume V/sub P/ and operating force to dielectric performance of GCB at current interruption, we calculated the prospective dielectric withstand voltage V/sub W/ between arcing contacts. The withstand voltage was calculated by the electric field strength appeared on arcing contacts and the allowable electric field strength E/sub W//sup */ of hot gas due to thermal puffer action. We could clarify that large initial puffer volume V/sub P/ can increase withstand voltage V/sub W/ at current breaking point and also that an optimum point exists in operating force F. For example, it was found that in case of the operating force of 1000 kgf, the puffer volume V/sub P/ of 1.2 liter would be best choice in the interrupting condition of i=50 kA and arcing time of 1.35 cycle.  相似文献   
999.
The Polarization and Directionality of the Earth's Reflectance (POLDER) spatial polarimeter was onboard the Advanced Earth Observation Satellite (ADEOS) satellite that flew from August 1996 to June 30, 1997. POLDER measured both multidirectional reflectance and polarization in visible and near-infrared spectral bands with a very wide field of view. An accurate absolute radiometric calibration is essential for the scientific exploitation of radiance measurements of the Earth. POLDER inflight radiometric calibration has been performed at the Centre National d'Etudes Spatiales (CNES), French National Space Studies Center, from measurements taken only on well-characterized targets. This paper presents the results of the POLDER in-flight radiometric interband calibration over clouds for channels 443 and 490 nm. The method is based on the comparison of measurements to simulations. Selected measurements correspond to observations over oceans for high, thick convective cumulonimbus and for low, thick stratocumulus. Simulations are calculated using the discrete ordinate computing method. An error budget considers the sensitivity of this calibration method to cloud microphysics, to cloud top altitude, and to aerosols and gaseous loading. Calibration results are discussed for different simulated cloud models  相似文献   
1000.
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