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   15909篇
  免费   1822篇
  国内免费   808篇
电工技术   850篇
综合类   1071篇
化学工业   2760篇
金属工艺   329篇
机械仪表   1156篇
建筑科学   1146篇
矿业工程   217篇
能源动力   459篇
轻工业   1063篇
水利工程   79篇
石油天然气   896篇
武器工业   100篇
无线电   3920篇
一般工业技术   2496篇
冶金工业   289篇
原子能技术   247篇
自动化技术   1461篇
  2024年   68篇
  2023年   287篇
  2022年   469篇
  2021年   572篇
  2020年   644篇
  2019年   586篇
  2018年   516篇
  2017年   652篇
  2016年   694篇
  2015年   706篇
  2014年   1090篇
  2013年   963篇
  2012年   1085篇
  2011年   1146篇
  2010年   926篇
  2009年   944篇
  2008年   863篇
  2007年   888篇
  2006年   843篇
  2005年   725篇
  2004年   611篇
  2003年   583篇
  2002年   428篇
  2001年   370篇
  2000年   363篇
  1999年   269篇
  1998年   223篇
  1997年   169篇
  1996年   138篇
  1995年   114篇
  1994年   121篇
  1993年   111篇
  1992年   63篇
  1991年   50篇
  1990年   51篇
  1989年   34篇
  1988年   26篇
  1987年   15篇
  1986年   21篇
  1985年   22篇
  1984年   25篇
  1983年   18篇
  1982年   18篇
  1981年   3篇
  1980年   3篇
  1979年   3篇
  1976年   3篇
  1964年   2篇
  1959年   2篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
81.
In this paper, we present an approach toward pedestrian detection and tracking from infrared imagery using joint shape and appearance cues. A layered representation is first introduced and a generalized expectation-maximization (EM) algorithm is developed to separate infrared images into background (still) and foreground (moving) layers regardless of camera panning. In the two-pass scheme of detecting pedestrians from the foreground layer: shape cue is first used to eliminate non-pedestrian moving objects and then appearance cue helps to locate the exact position of pedestrians. Templates with varying sizes are sequentially applied to detect pedestrians at multiple scales to accommodate different camera distances. To facilitate the task of pedestrian tracking, we formulate the problem of shot segmentation and present a graph matching-based tracking algorithm that jointly exploits the shape, appearance and distance information. Experimental results with both OSU Infrared Image Database and WVU Infrared Video Database are reported to demonstrate the accuracy and robustness of our algorithm.  相似文献   
82.
基础锚栓预埋加固方案   总被引:1,自引:0,他引:1  
结合工程实例 ,介绍轻钢结构系统基础锚栓预埋、加固解决方案 ,并介绍了加固系统的制作及使用方法 ,可供工程人员参考  相似文献   
83.
利用自行研制的“光电阴极多信息量测试系统”首次对国产三代微光管中的GaAs光电阴极的均匀性进行了光谱响应测试 ,结果表明该国产三代微光管存在明显的非均匀性。利用曲线拟合方法估算了GaAs光电阴极的材料性能参数 ,发现表面逸出概率不一致是非均匀性的主要原因 ,GaAs材料的少子扩散长度 (1 1 2~ 1 82 ) μm ,与阴极厚度相当 ,后界面复合速率在 (1× 1 0 5~ 1× 1 0 6 )cm/s之间 ,它限制了阴极灵敏度的提高  相似文献   
84.
Fluorescent photon down conversion for the improvement of the blue response of ZnO/CdS/Cu(In,Ga)Se2 heterojunction solar cells and modules is investigated. Fluorescent dyes of the series Lumogen® F are analyzed by optical transmission and reflection as well as by photoluminescence measurements. A spectral transfer matrix formalism is introduced that allows to predict the suitability of a luminescent dye as a down-converter for a given solar cell from its absorption/emission properties. We find that Lumogen® F Violet 570 and Lumogen® F Yellow 083 as well as a combination of both yields improvements for Cu(In,Ga)Se2 solar modules. Particularly, we find that the short circuit current density of a Cu(In,Ga)Se2 mini-module is improved by 1.5 mA cm− 2 when applying a varnish with a combination of Lumogen® F Violet and Yellow. About 0.5 mA cm− 2 of this improvement is due to a reduced overall reflectance and an improvement of 1 mA cm− 2 results from the frequency conversion by the dyes.  相似文献   
85.
Heather J. Avens 《Polymer》2008,49(22):4762-4768
Surface modification by surface-mediated polymerization necessitates control of the grafted polymer film thicknesses to achieve the desired property changes. Here, a microarray format is used to assess a range of reaction conditions and formulations rapidly in regards to the film thicknesses achieved and the polymerization behavior. Monomer formulations initiated by eosin conjugates with varying concentrations of poly(ethylene glycol) diacrylate (PEGDA), N-methyldiethanolamine (MDEA), and 1-vinyl-2-pyrrolidone (VP) were evaluated. Acrylamide with MDEA or ascorbic acid as a coinitiator was also investigated. The best formulation was found to be 40 wt% acrylamide with MDEA which yielded four to eightfold thicker films (maximum polymer thickness increased from 180 nm to 1420 nm) and generated visible films from fivefold lower eosin surface densities (2.8 versus 14 eosins/μm2) compared to a corresponding PEGDA formulation. Using a microarray format to assess multiple initiator surface densities enabled facile identification of a monomer formulation that yields the desired polymer properties and polymerization behavior across the requisite range of initiator surface densities.  相似文献   
86.
This paper comes true a system of facial detection and location. Firstly, it realizes the facial detection of candidate region used skin color for the given image, and considers the influence of similar skin. Secondly, it realizes the location for eye region used the gray characteristic of eye and correction of central measurement, and makes further selection for facial candidate region. The end, it normalizes the facial image and makes it as front standard image, so realizes the facial characteristic location.  相似文献   
87.
By using Ni0‐mediated polymerization, we have systematically synthesized a series of fluorene‐based copolymers composed of blue‐, green‐, and red‐light‐emitting comonomers with a view to producing polymers with white‐light emission. 2,7‐Dibromo‐9,9‐dihexylfluorene, {4‐(2‐[2,5‐dibromo‐4‐{2‐(4‐diphenylamino‐phenyl)‐vinyl}‐phenyl]‐vinyl)‐phenyl}‐diphenylamine (DTPA), and 2‐{2‐(2‐[4‐{bis(4‐bromo‐phenyl)amino}‐phenyl]‐vinyl)‐6‐tert‐butyl‐pyran‐4‐ylidene}‐malononitrile (TPDCM) were used as the blue‐, green‐, and red‐light‐emitting comonomers, respectively. It was found that the emission spectra of the resulting copolymers could easily be tuned by varying their DTPA and TPDCM content. Thus with the appropriate red/green/blue (RGB) unit ratio, we were able to obtain white‐light emission from these copolymers. A white‐light‐emitting diode using the polyfluorene copolymer containing 3 % green‐emitting DTPA and 2 % red‐emitting TPDCM (PG3R2) with a structure of indium tin oxide/poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonic acid)/PG3R2/Ca/Al was found to exhibit a maximum brightness of 820 cd m–2 at 11 V with Commission Internationale de L'Eclairage (CIE) coordinates of (0.33,0.35), which are close to the standard CIE coordinates for white‐light emission (0.33,0.33).  相似文献   
88.
以实际工程为背景,采用门式刚架轻型房屋钢结构设计规程,对带吊车门式刚架、吊车梁、抗风柱及基础的受力特点、设计方法进行分析,解决了设计中所遇到的问题。  相似文献   
89.
垂直定向液晶光阀及光电特性的研究   总被引:2,自引:0,他引:2  
系统地讨论了排列相畸变模式液晶光阀结构,原理和制作,结合实际测试对其等效电路和电学匹配进行了分析,详细讨论了它的光电特性及相互关系,实测的液晶垂直排列方式工作的液晶光阀性能指标为,分辨率大于50lp/mm,白光输入灵敏度为6.77μW/cm^2,响应时间为200ms/300ms,白光输出对比度为200:1。  相似文献   
90.
彭国贤 《光电子技术》1995,15(2):122-129
本文叙述自动化仪表用光柱显示技术的工作原理及器件结构,重点论述直流等离子体光柱,发光二极管光柱,真空荧光及液晶光柱器件的结构和驱动电路,还展望光柱显示的发展趋势。  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