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   760807篇
  免费   15687篇
  国内免费   5578篇
电工技术   16587篇
技术理论   2篇
综合类   5179篇
化学工业   114216篇
金属工艺   29174篇
机械仪表   24350篇
建筑科学   22577篇
矿业工程   4589篇
能源动力   21287篇
轻工业   69385篇
水利工程   7970篇
石油天然气   13990篇
武器工业   660篇
无线电   90004篇
一般工业技术   139340篇
冶金工业   139995篇
原子能技术   13459篇
自动化技术   69308篇
  2022年   6062篇
  2021年   8963篇
  2020年   6657篇
  2019年   7344篇
  2018年   11252篇
  2017年   11468篇
  2016年   11779篇
  2015年   9801篇
  2014年   15022篇
  2013年   36745篇
  2012年   23181篇
  2011年   31234篇
  2010年   24906篇
  2009年   27285篇
  2008年   27987篇
  2007年   27115篇
  2006年   24259篇
  2005年   21784篇
  2004年   20053篇
  2003年   19486篇
  2002年   18410篇
  2001年   18519篇
  2000年   17058篇
  1999年   18156篇
  1998年   44706篇
  1997年   31316篇
  1996年   23948篇
  1995年   18130篇
  1994年   15730篇
  1993年   15336篇
  1992年   10983篇
  1991年   10306篇
  1990年   9948篇
  1989年   9567篇
  1988年   8992篇
  1987年   7732篇
  1986年   7552篇
  1985年   8681篇
  1984年   8040篇
  1983年   7167篇
  1982年   6728篇
  1981年   6869篇
  1980年   6432篇
  1979年   6208篇
  1978年   5862篇
  1977年   7060篇
  1976年   9172篇
  1975年   5060篇
  1974年   4743篇
  1973年   4941篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
The catalytic activities of alumina prepared from an Al alkoxide-amine adduct monomer for the reaction of cyclopentene oxide with piperidine was determined after various pretreatments, including calcination and exposure to moisture. They were compared with the activity of alumina prepared by the conventional hydrolysis method. It was found that the as-prepared sample from the alkoxide-amine monomer preparation was five times more active than a conventional preparation, suggesting that it has a higher density of surface Lewis acid sites. However, its activity was much more severely suppressed by exposure to moisture.  相似文献   
62.
The purpose of this paper is to introduce a new I DDQ measurement technique based on active successive approximations, called ASA-I DDQ. This technique has unique features facilitating a speed-up in I DDQ measurement. Experimental results suggest that a significant speed-up factor (up to 4) can be obtained over the QuiC-Mon technique. Such a speed-up is a key element in the replacement of single-threshold I DDQ testing since it amplifies the effectiveness of post-processing techniques.  相似文献   
63.
64.
For pt.I see ibid., p.42-55 (2003). The development of a comprehensive decision support system, GMCR II, for the systematic study of real-world interactive decision problems is presented. The companion paper (Part I), discusses how GMCR II elicits, stores, and manages conflict models; here (Part II), the focus is on GMCR IIs analysis and output interpretation subsystems. Specifically, this paper describes the powerful and efficient analysis engine contained in GMCR II, its informative output presentation and interpretation facilities, and a number of follow-up analyses. Furthermore, an illustrative case study is used to demonstrate how GMCR II can be conveniently applied in practice.  相似文献   
65.
The problem considered in this paper is the design and tuning of the control system of a power-split continuously variable transmission (CVT) used in high-power tractors. Power-split CVTs are characterized by the combination of a traditional mechanical transmission and by a continuously-variable transmission. This guarantees, at the same time, smooth variations of the transmission-ratio and high efficiency of the overall transmission system. The control architecture of an hydrostatic power-split CVT is constituted by three main parts: 1) servo-controller on the current of the valve which drives the hydraulic transmission; 2) a servo-controller on the hydraulic transmission-ratio; and 3) a synchronizer which coordinates the hydraulic and the mechanical parts of the CVT. In this work, these three controllers are fully developed, including: design, implementation, and evaluation on an experimental system.  相似文献   
66.
The current Internet and wireless networks are harsh environments for transporting high-bandwidth multimedia data. We examine the technical issues involved, and describe an end-to-end solution to support a Web-based learn-on-demand system that operates in a wireless campus environment.  相似文献   
67.
This paper describes a novel planar antenna sensor created for the purpose of noninvasive temperature measurements using microwave radiometry. In order to improve radiometric measurements in industrial applications, a new generation of sensors is introduced, composed of a metallic sheet. Simulations based upon the method of moments is used both to design and to determine their electromagnetic performances. This paper also describes a radiometric device using these sensors to measure and control the temperature of food products during deep freezing processes. The results and discussions are presented.  相似文献   
68.
This paper describes techniques for the on-chip measurement of high-frequency and/or high-bandwidth electrical phenomena in ultra large-scale integration environments. The techniques rely on the integration of multiple compact and robust electronic test devices, or cores, at various locations within an integrated circuit. The cores consist primarily of signal generators that approximate the output of a sigma-delta modulator using finite repetitious bit patterns and a small set of highly robust analog components. They are capable of digitizing on-chip signals at gigahertz rates even using low-cost manufacturing processes. Simple communication between the multiple cores enables the migration of many "board-level" type measurements down to the chip level.  相似文献   
69.
70.
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