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   19739篇
  免费   842篇
  国内免费   505篇
电工技术   203篇
技术理论   1篇
综合类   369篇
化学工业   6879篇
金属工艺   2814篇
机械仪表   1015篇
建筑科学   175篇
矿业工程   69篇
能源动力   540篇
轻工业   271篇
水利工程   21篇
石油天然气   34篇
武器工业   60篇
无线电   2758篇
一般工业技术   4518篇
冶金工业   309篇
原子能技术   148篇
自动化技术   902篇
  2024年   29篇
  2023年   291篇
  2022年   330篇
  2021年   493篇
  2020年   482篇
  2019年   444篇
  2018年   453篇
  2017年   473篇
  2016年   494篇
  2015年   508篇
  2014年   992篇
  2013年   1006篇
  2012年   1065篇
  2011年   1698篇
  2010年   1200篇
  2009年   1180篇
  2008年   1176篇
  2007年   1133篇
  2006年   1224篇
  2005年   938篇
  2004年   859篇
  2003年   670篇
  2002年   543篇
  2001年   387篇
  2000年   384篇
  1999年   452篇
  1998年   419篇
  1997年   349篇
  1996年   331篇
  1995年   202篇
  1994年   194篇
  1993年   132篇
  1992年   122篇
  1991年   119篇
  1990年   91篇
  1989年   91篇
  1988年   52篇
  1987年   11篇
  1986年   17篇
  1985年   5篇
  1984年   6篇
  1983年   6篇
  1982年   11篇
  1981年   2篇
  1980年   4篇
  1976年   3篇
  1975年   5篇
  1974年   2篇
  1973年   5篇
  1955年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
张锦 《光电工程》1996,23(1):53-58
介绍了计算机光学零件图自动绘制软件系统的功能,给出了用该软件完成的光学零件图图样,对程序设计过程中的难点及处理方法也进行了详细阐述。  相似文献   
102.
介绍HS─2000双反射镜补偿式高速摄影系统的补偿原理、结构及其试验结果。  相似文献   
103.
测量平动物体位移的光纤传感器已有许多报导,而测量转动物体位移的光纤传感器却很少,从原理和实验两方面对后一问题作了研究。  相似文献   
104.
介绍了一种光纤式机器人触觉传感器,分析了这种传感器的静态特性,并通过理论分析和实验研究提出了一种消除干扰的方法。实验结果证明,传感器的最大绝对误差为0.053kg,相对误差为0.62%。  相似文献   
105.
光盘用光学头物镜性能的综合评估   总被引:1,自引:0,他引:1  
杨勋  曾吉勇 《光电工程》1994,21(2):49-52
论述了采用波象差均方根、点扩展函数、光学传递函数对高次旋转对称非球面光学头物镜性能进行综合评估的方法。作者在正则坐标理论基础〔1〕上编制了光学头物镜性能综合评估软件。给出了评估实例。  相似文献   
106.
Using the ray trace method,three-section semiconductor lasers are studied .An analytic expression of output power for the three-section semiconductor lasers is derived for the first time.Frome this expression,threshold condition is also obtained.  相似文献   
107.
Statistical studies of branched ester latex and paint properties   总被引:3,自引:0,他引:3  
Vinyl versatate, butyl acrylate and 2-ethylhexyl acrylate were compared as comonomer, for colloid-stabilized vinyl acetate latex polymers to assess their impact on latex coating properties. Vinyl versatate afforded advantages in scrub resistance, gloss, hydrophobicity and higher glass transition temperatures. Butyl acrylate developed better wet adhesion efficiency, gel content and hiding efficiency. 2-Ethylhexyl acrylate offered performance comparable to butyl acrylate in hiding efficiency, lowering copolymer glass transition temperatures, and gloss development. Combinations of these monomers, in many instances, afforded a better balance of performance properties than individual monomers alone. In the subject study, a simplex-centroid design was utilized to statistically map polymer compositions for determining the effect of comonomer composition on latex and paint film properties. In addition to developing contour maps of polymer and paint properties as a function of composition, a technique for studying structure-property relationships is presented.  相似文献   
108.
Iron pyrite films prepared by sulfur vapor transport   总被引:4,自引:0,他引:4  
Iron films deposited via thermal evaporation, with a thickness between 100 and 250 nm, were converted into FeS2 by open sulfur transport using nitrogen as a gas vector. The films thus obtained constituted a single pyrite phase and were optically highly absorbing. The sulfurization process was optimized. As a result, sample temperature and conversion time were found to be the major determining parameters. The films were characterized using several methods. The crystallinity and phase identification were determined by X-ray diffractometry. Scanning electron microscopy showed a homogeneous surface of both iron and pyrite layers. Optical transmission measurements confirmed the highly absorbing character of FeS2 and allowed the determination of direct (1.35 eV) and indirect (0.82 eV) transitions.  相似文献   
109.
An optical system for fast IR radiometry designed for investigations of thin film thermal properties and pulsed laser melting was analyzed in this work. A methodology for determination of the view factor from calibration measurements was developed. The view factor (0.0255) of the optical system containing two paraboloid mirrors was determined experimentally from calibration measurements on pure metals and metallic alloys. The knowledge of the view factor was then applied to normal emissivity investigations at IR wavelengths. The emissivity of tungsten films prepared by magnetron sputtering was determined for different deposition conditions, varying between 0.036 and 0.071. Liquid phase emissivities of Cu, Mo, Ni, Si, Sn, Ti, and steel were also determined and were found to be higher than solid-state emissivities as predicted from the literature. A knowledge of the liquid-state emissivity of silicon enabled recalculation of the IR signal evolution to the temperature evolution, during and after a nanosecond laser pulse. This was not possible by use of the usual calibration because of silicon’s semi-transparent behavior in the IR range (1–10 μm) in the solid-state phase.  相似文献   
110.
The optical and thermal properties of prepared poly(ethylene oxide)/MnCl2 films were studied as a function of MnCl2 concentration at room temperature. The observed optical energy gap (Eopt) and energy gap tail (ΔE) were determined from the measured absorption spectra. It was found that the optical energy gap decreases with MnCl2 concentration, and the absorption coefficient reduces sharply at concentration of 5 wt% MnCl2 compared with the neat PEO. Differential scanning calorimetry (DSC) measurement shows that the heat of fusion increases with the MnCl2 concentration, while the melting point decreases. Correlation between the observed optical energy gap and heat of fusion is presented.  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