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   40146篇
  免费   1418篇
  国内免费   79篇
电工技术   447篇
综合类   37篇
化学工业   8560篇
金属工艺   1029篇
机械仪表   762篇
建筑科学   2100篇
矿业工程   259篇
能源动力   1254篇
轻工业   3415篇
水利工程   407篇
石油天然气   232篇
武器工业   8篇
无线电   2679篇
一般工业技术   6694篇
冶金工业   7453篇
原子能技术   362篇
自动化技术   5945篇
  2022年   304篇
  2021年   545篇
  2020年   478篇
  2019年   531篇
  2018年   660篇
  2017年   697篇
  2016年   763篇
  2015年   624篇
  2014年   991篇
  2013年   2720篇
  2012年   1668篇
  2011年   2106篇
  2010年   1520篇
  2009年   1617篇
  2008年   1915篇
  2007年   1874篇
  2006年   1604篇
  2005年   1454篇
  2004年   1320篇
  2003年   1253篇
  2002年   1224篇
  2001年   748篇
  2000年   712篇
  1999年   686篇
  1998年   716篇
  1997年   600篇
  1996年   697篇
  1995年   632篇
  1994年   637篇
  1993年   611篇
  1992年   540篇
  1991年   369篇
  1990年   485篇
  1989年   483篇
  1988年   423篇
  1987年   448篇
  1986年   415篇
  1985年   555篇
  1984年   525篇
  1983年   469篇
  1982年   488篇
  1981年   484篇
  1980年   376篇
  1979年   385篇
  1978年   354篇
  1977年   324篇
  1976年   278篇
  1975年   329篇
  1974年   262篇
  1973年   292篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
The pipelined architecture and parallel organization of the AT&T Pixel Machine image computer are described and demonstrated with applications for the visualization of multidimensional fractals, particularly linear fractals and quaternion/ stacked Julia sets. Techniques for pushing the Pixel Machine to its peak abilities are described and apply to more recent parallel image computers as well.  相似文献   
52.
For users of an executive information system (EIS), the EIS interface is the system and is crucial to the EIS's success. These guidelines for designing EIS interfaces are based on studies of actual EIS interfaces that meet the unique information needs of executives.  相似文献   
53.
54.
α,ω-Methacrylate-terminated poly(1,3-dioxolane)s (polyDXL) were synthesized by cationic ring-opening polymerization of DXL in the presence of methylene-bis(oxyethylmethacrylate) as transfer agent. If the initiator concentration is small compared with the transfer agent concentration, the molecular weights of the polymers are governed by the ratio of the reacted monomer to the reacted transfer agent. The α,ω-methacrylate-terminated polyDXLs obtained undergo free radical polymerization with formation of polyacetal networks. The properties of the networks as function of the molecular weight of the corresponding prepolymers are reported.  相似文献   
55.
56.
Characterisation of raw materials for Portland cement manufacture by use of the methylene blue adsorption method is discussed. The method is shown to be a simple, convenient ‘rule of thumb’ procedure. It provides a guide to the quantity and type of argillaceous minerals present in a given raw material sample.  相似文献   
57.
Experiments showing the frequency and amplitude of the flow induced motion of the gate for a 2- and a 4-in. swing check valve have been performed. The gate motion is due to turbulence in approach flow. We have found the dominant turbulent frequency of the approach flow is about half the natural frequency of the valves. The valves appear to be almost critically damped. Because of this, the valves respond almost as they would to a static force of the magnitude characteristic of the turbulent fluctuation in the flow. Both the dimensionless exciting force and the damping ratio have been found to be independent of valve size so the above statements are true for larger valves also. The recommended valve oscillation amplitudes and frequencies are used to calculate the wear at the shaft and at the stop. For an unpegged check valve, such as one of the 10-in. valves which was used at the San Onofre Nuclear Generation Station, it was found that shaft bearing wear would amount to 0.27 in.3/year and stop wear to 0.03 in.3/year.  相似文献   
58.
Analyses of human object recognition abilities led to the hypothesis that 2 kinds of spatial relation representations are used in human vision. Evidence for the distinction between abstract categorical spatial relation representations and specific coordinate spatial relation representations was provided in 4 experiments. These results indicate that Ss make categorical judgments—on/off, left/right, and above/below—faster when stimuli are initially presented to the left cerebral hemisphere, whereas they make evaluations of distance—in relation to 2 mm, 3 mm, or 1 in. (2.54 cm)—faster when stimuli are initially presented to the right cerebral hemisphere. In addition, there was evidence that categorical representations developed with practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
59.
60.
传统制导弹药自动驾驶仪的设计要求精确的气动模型,并依赖于变增益(gainschedule),以说明系统的非线性.本文给出了一种简化自动驾驶仪设计程序的方法:在单一飞行条件下设计逆控制器,将逆控制器与在线神经网络组合,以说明因近似逆引起的误差,这样减少了大量设计程序及精确的气动数据.这些数据在大攻角或其它情况下很重要,因为这些领域中的空气动力特征变得高度非线性化.研究发现:逆的选择在其实现的过程中很重要,所以详细讨论.最后,给出该方法在非线性6自由度制导弹药中的模拟结果.  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