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   318142篇
  免费   19498篇
  国内免费   10206篇
电工技术   14245篇
技术理论   17篇
综合类   16170篇
化学工业   51599篇
金属工艺   17024篇
机械仪表   17048篇
建筑科学   21049篇
矿业工程   6700篇
能源动力   7931篇
轻工业   18740篇
水利工程   5127篇
石油天然气   12816篇
武器工业   1618篇
无线电   37808篇
一般工业技术   45706篇
冶金工业   15077篇
原子能技术   2778篇
自动化技术   56393篇
  2024年   1024篇
  2023年   3757篇
  2022年   6770篇
  2021年   9245篇
  2020年   6806篇
  2019年   5856篇
  2018年   19761篇
  2017年   19763篇
  2016年   15931篇
  2015年   9179篇
  2014年   11447篇
  2013年   14507篇
  2012年   17385篇
  2011年   24995篇
  2010年   21553篇
  2009年   18613篇
  2008年   19206篇
  2007年   19702篇
  2006年   12735篇
  2005年   12318篇
  2004年   8815篇
  2003年   8298篇
  2002年   7695篇
  2001年   6497篇
  2000年   6065篇
  1999年   6490篇
  1998年   5834篇
  1997年   4790篇
  1996年   4326篇
  1995年   3635篇
  1994年   3024篇
  1993年   2350篇
  1992年   1861篇
  1991年   1431篇
  1990年   1107篇
  1989年   951篇
  1988年   749篇
  1987年   528篇
  1986年   420篇
  1985年   348篇
  1984年   223篇
  1983年   204篇
  1982年   175篇
  1981年   154篇
  1980年   152篇
  1979年   103篇
  1978年   68篇
  1977年   69篇
  1976年   81篇
  1954年   68篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
State space explosion is a key problem in the analysis of finite state systems. The sweep-line method is a state exploration method which uses a notion of progress to allow states to be deleted from memory when they are no longer required. This reduces the peak number of states that need to be stored, while still exploring the full state space. The technique shows promise but has never achieved reductions greater than about a factor of 10 in the number of states stored in memory for industrially relevant examples. This paper discusses sweep-line analysis of the connection management procedures of a new Internet standard, the Datagram Congestion Control Protocol (DCCP). As the intuitive approaches to sweep-line analysis are not effective, we introduce new variables to track progress. This creates further state explosion. However, when used with the sweep-line, the peak number of states is reduced by over two orders of magnitude compared with the original. Importantly, this allows DCCP to be analysed for larger parameter values. Somsak Vanit-Anunchai was partially supported by an Australian Research Council Discovery Grant (DP0559927) and Suranaree University of Technology. Guy Edward Gallasch was supported by an Australian Research Council Discovery Grant (DP0559927).  相似文献   
72.
This paper presents an approach of measuring in real-time the vector of finger that is pointing to an object. DSP is used in the operation processing unit in order to do the real-time processing. The steps include the extraction of flesh-colored regions from an image, the labeling of the flesh-colored regions, and the detection of two characteristic positions on the finger so that the direction that the finger is pointing at will be calculated. The entire process takes about 29 msec, which makes it possible to have the frame rate of 34 fps. With this frame rate, this measurement approach is considered real-time and promising to be merged into other application systems. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008  相似文献   
73.
磷矿中七种金属元素的光谱法测定   总被引:2,自引:0,他引:2  
陈名樑 《山西冶金》2004,27(1):36-37
研究了磷矿样品中7种金属元素锰、钴、镍,锌、铬、钼及铋的分析方法,选择了灵敏度高干扰少的谱线,绘制出工作曲线,对样品进行了科学处理,不必进行化学分离即可对七种元素同时测定,经合成样分析、回收实验及样品测定,证明此方法精确可靠,其回收率在98%-102%之间。  相似文献   
74.
该文介绍了Mall的产生条件和国内发展概况,并结合实例分析,着重论述建筑设计方面的有关问题。  相似文献   
75.
A new type of piezoelectric linear motor incorporating a traveling wave has been developed. The linear motor is comprised of a stator and a carriage. The stator design, which consists of a meander-line structure and gear teeth mounted on the meander-line structure, is the focus of this article. The meander-line structure is constructed with bimorph actuators arranged in a line. These actuators are driven by two phased sets of alternating current (ac) in order to generate a traveling wave. The traveling wave is transferred to the gear teeth, by which the carriage is driven. Modeling of the stator is derived by use of a strain energy method. The performance of various materials is evaluated by analytical and experimental methods. The analytical and the experimental results are quite approximate. Modal analysis is investigated using ANSYS. Appropriate modes associated with ultrasonic levels of resonant frequency are selected to obtain desired motion and to enhance the output performance. Surface speed for various applied input voltage are studied and indicate a nearly linear relationship. The stator in combination with the carriage makes up the linear motor.  相似文献   
76.
77.
This study investigates the ozonation of CI Reactive Black 5 (RB5) by using the rotating packed bed (RPB) and completely stirred tank reactor (CSTR) as ozone contactors. The RPB, which provides high gravitational force by adjusting the rotational speed, was employed as a novel ozone contactor. The same ozone dosage was separately introduced into either the RPB or the CSTR for the investigation, while the experimental solution was continuously circulated within the apparatus consisting of the RPB and CSTR. The decolorization and mineralization efficiencies of RB5 in the course of ozonation are compared for these two methods. Moreover, the dissolved and off‐gas ozone concentrations were simultaneously monitored for the further analysis. As a result, the ozone mass transfer rate per unit volume of the RPB was significantly higher because of its higher mass transfer coefficient and gas–liquid concentration driving force. Furthermore, ozonation kinetics was found to be independent of the gravitational magnitude of an ozone gas–liquid contactor. Therefore, the results suggest employing RPBs as ozone‐contacting devices with the advantage of volume reduction. The experimental results, which can be used for further modeling of the ozonation process in the RPB, also show the requirement of correct design for the RPB. Consequently, the present study is useful for the understanding of practical application of RPBs. Copyright © 2004 Society of Chemical Industry  相似文献   
78.
79.
80.
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