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   89018篇
  免费   8811篇
  国内免费   5369篇
电工技术   5936篇
技术理论   8篇
综合类   7722篇
化学工业   13786篇
金属工艺   4903篇
机械仪表   5334篇
建筑科学   6787篇
矿业工程   2526篇
能源动力   2297篇
轻工业   9906篇
水利工程   2230篇
石油天然气   4207篇
武器工业   851篇
无线电   10083篇
一般工业技术   9176篇
冶金工业   3363篇
原子能技术   1004篇
自动化技术   13079篇
  2024年   544篇
  2023年   1649篇
  2022年   3206篇
  2021年   4147篇
  2020年   3309篇
  2019年   2486篇
  2018年   2728篇
  2017年   3114篇
  2016年   2778篇
  2015年   4093篇
  2014年   5223篇
  2013年   6042篇
  2012年   6871篇
  2011年   7382篇
  2010年   6579篇
  2009年   6052篇
  2008年   6072篇
  2007年   5523篇
  2006年   5011篇
  2005年   3995篇
  2004年   2887篇
  2003年   2391篇
  2002年   2417篇
  2001年   2046篇
  2000年   1440篇
  1999年   1270篇
  1998年   758篇
  1997年   650篇
  1996年   587篇
  1995年   439篇
  1994年   350篇
  1993年   258篇
  1992年   236篇
  1991年   151篇
  1990年   121篇
  1989年   95篇
  1988年   58篇
  1987年   49篇
  1986年   36篇
  1985年   18篇
  1984年   21篇
  1983年   15篇
  1982年   19篇
  1981年   17篇
  1980年   23篇
  1979年   14篇
  1978年   2篇
  1977年   3篇
  1959年   7篇
  1951年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
对HP700圆锥破碎机的主要部件动锥建立了有限元分析模型,用ANSYS软件对动锥进行了有限元强度和刚度分析,结果输出了动锥分布及变形图,对圆锥破碎机的结够设计提供了依据。  相似文献   
22.
23.
24.
This study examined the removal of some basic dyes, such as Methylene Blue, Malachite Green and Methyl Orange, using alginate or alginate/polyaspartate composite gel beads. The adsorption of dyes from aqueous solutions at 25 °C was examined using a batch sorption technique. The effects of CaCl2 and the dye concentration on the adsorption were examined. Type-S adsorption isotherms were obtained, which is characteristic of a weak solute–solid interaction. The ionic interaction between the dye molecule and gel matrix appears to be responsible for the efficient adsorption of cationic dyes in this system. These results suggest that an alginate/polyaspartate gel can be used as an effective sorbent for water pollutants such as dyes, and the immobilization of these organic contaminants in the hydrogels from wastewater can solve one of the most important environmental problems in the related industry.  相似文献   
25.
26.
27.
Based on the optimal fusion estimation algorithm weighted by scalars in the linear minimum variance sense, a distributed optimal fusion Kalman filter weighted by scalars is presented for discrete‐time stochastic singular systems with multiple sensors and correlated noises. A cross‐covariance matrix of filtering errors between any two sensors is derived. When the noise statistical information is unknown, a distributed identification approach is presented based on correlation functions and the weighted average method. Further, a distributed self‐tuning fusion filter is given, which includes two stage fusions where the first‐stage fusion is used to identify the noise covariance and the second‐stage fusion is used to obtain the fusion state filter. A simulation verifies the effectiveness of the proposed algorithm. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
28.
We address the problem of localizing and obtaining high-resolution footage of the people present in a scene. We propose a biologically-inspired solution combining pre-attentive, low-resolution sensing for detection with shiftable, high-resolution, attentive sensing for confirmation and further analysis. The detection problem is made difficult by the unconstrained nature of realistic environments and human behaviour, and the low resolution of pre-attentive sensing. Analysis of human peripheral vision suggests a solution based on integration of relatively simple but complementary cues. We develop a Bayesian approach involving layered probabilistic modeling and spatial integration using a flexible norm that maximizes the statistical power of both dense and sparse cues. We compare the statistical power of several cues and demonstrate the advantage of cue integration. We evaluate the Bayesian cue integration method for human detection on a labelled surveillance database and find that it outperforms several competing methods based on conjunctive combinations of classifiers (e.g., Adaboost). We have developed a real-time version of our pre-attentive human activity sensor that generates saccadic targets for an attentive foveated vision system. Output from high-resolution attentive detection algorithms and gaze state parameters are fed back as statistical priors and combined with pre-attentive cues to determine saccadic behaviour. The result is a closed-loop system that fixates faces over a 130 deg field of view, allowing high-resolution capture of facial video over a large dynamic scene.  相似文献   
29.
Experimental Research on Erbium-doped Superfluorescent Fiber Source   总被引:1,自引:0,他引:1  
The effects of the variations in fiber length, fiber mirror reflectance on efficiency and output power are experimentally investigated for erbium-doped double pass backward superfluorescent fiber sources (SFSs). The influence of fiber length on mean wavelength stability (MWS) has also been demonstrated. By incorporating a short section of un-pumped erbium-doped fiber (EDF) at the output port, the pump power dependent on MWS becomes independent of pumped EDF length. This is a novel phenomenon that hasn‘t been reported up to now,and should be helpful to SFS fabrication and theory analysis. By using a fiber Michelson interferometer as spectrum slicing component,a multi-wavelength fiber source (MWFS) with ~20 channels (from 1542nm to 1559nm) is got. The MWFS has a channel spacing of ~0. 8 nm which satisfies ITUstandard. The intensity fluctuation among channels is less than 0.5dB,and the extinction ratio of all channels is above 14dB. This kind of MWFS should be useful to wavelength division multiplexing systems.  相似文献   
30.
IF板与08Al板的成形性能研究   总被引:2,自引:0,他引:2  
通过模拟成形性试验,对新型超深冲用IF钢板和传统冲压用08Al钢板的冲压成形性能进行了研究.结果表明:IF板的拉深性能、扩孔性能、胀形性能以及“拉深-胀形”复合性能等均优于08Al板,其中,扩孔性能和平面各向异性的改善最为显著;各项试验中,IF板的成形力普遍小于08Al板。  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