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   37745篇
  免费   3148篇
  国内免费   3189篇
电工技术   3158篇
技术理论   5篇
综合类   2469篇
化学工业   2452篇
金属工艺   298篇
机械仪表   1440篇
建筑科学   1323篇
矿业工程   186篇
能源动力   1357篇
轻工业   454篇
水利工程   272篇
石油天然气   229篇
武器工业   178篇
无线电   2627篇
一般工业技术   2957篇
冶金工业   874篇
原子能技术   150篇
自动化技术   23653篇
  2024年   102篇
  2023年   595篇
  2022年   447篇
  2021年   732篇
  2020年   1012篇
  2019年   1081篇
  2018年   1013篇
  2017年   1368篇
  2016年   1471篇
  2015年   1328篇
  2014年   2258篇
  2013年   3466篇
  2012年   1811篇
  2011年   2299篇
  2010年   1673篇
  2009年   2176篇
  2008年   2166篇
  2007年   2157篇
  2006年   1876篇
  2005年   1686篇
  2004年   1423篇
  2003年   1341篇
  2002年   1228篇
  2001年   983篇
  2000年   977篇
  1999年   889篇
  1998年   793篇
  1997年   707篇
  1996年   642篇
  1995年   554篇
  1994年   497篇
  1993年   480篇
  1992年   368篇
  1991年   353篇
  1990年   279篇
  1989年   216篇
  1988年   186篇
  1987年   164篇
  1986年   137篇
  1985年   180篇
  1984年   187篇
  1983年   167篇
  1982年   147篇
  1981年   96篇
  1980年   71篇
  1979年   85篇
  1978年   61篇
  1977年   67篇
  1976年   19篇
  1975年   13篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Technology can take many forms from the development of sophisticated electronics to the application of basic procedural principles. Technology transfer can also take several forms, however, in this case, it is the transfer of technological principles between application domains that is of primary interest. This paper presents a framework (the Five ‘M’s framework) that can be used to consider the likely success of technology transfer. The framework is based upon a sociotechnical system approach. The framework is illustrated with an evaluation of the introduction of intelligent cruise control into motor vehicles. It is argued that this is a technological concept first developed as an aerospace application in the form of the autopilot. In this case, it is argued that the transfer of this technology in its current form may potentially compromise safety.  相似文献   
72.
A fast room temperature microwave detection system based on the Schottky Barrier-diode detector was created at the KEK ATF (Accelerator Test Facility). It was tested using Coherent Synchrotron Radiation (CSR) generated by the 1.28 GeV electron beam in the damping ring. The speed performance of the detection system was checked by observing the CSR from a multi-bunch (2.8 ns bunch separation time) beam. The theoretical estimations of CSR power yield from an edge of bending magnet as well as new injection tuning method are presented. A very high sensitivity of CSR power yield to the longitudinal electron distribution in a bunch is discussed.  相似文献   
73.
研究了多径信道下OFDM系统的一种新的载波频率跟踪算法,这种算法以判决反馈和接收端的时域信号重构为基础。推导了估计结果的精确解,比较了使用原估计结果和新的估计结果进行频偏补偿时系统跟踪性能的不同。通过对算法的仔细分析,发现除了通常的加性噪声外,信道估计误差、子载波数目和子载波的调制方式也影响频偏的估计结果和跟踪范围,而且子载波的数目和调制方式是决定性的因素。这种频率跟踪方法的优点是即使在很低的信噪比下仍然能获得高的跟踪精度,且实现相对简单。  相似文献   
74.
75.
76.
We give an elementary proof of the well-known fact that shift-invariant operators onL 2[0, ∞) are represented by transfer functions which are bounded and analytic on the right open half-plane. We prove a generalization to Banach space-valuedL p -functions, where 1≤p<∞. We show that the result no longer holds forp=∞. This research was supported partially by the Weizmann Fellowship, and partially by the Air Force Office of Scientific Research under Contract F49620-86-C-0111.  相似文献   
77.
We obtain a necessary and sufficient condition for a discrete-time nonlinear system to be locally state equivalent to the nonlinear observer form. The result looks similar to the continuous counterpart except for the fact that Ad-operation is utilized instead of ad-operation.  相似文献   
78.
The objective of this note is to propose a method for stabilization of structurally fixed modes in expansions of LTI dynamic systems in the scope of overlapping decentralized control design based on the expansion/contraction framework, enabling successful design for a broader class of problems than considered so far. The method is based on a judicious choice of complementary matrices in the expanded space. Numerical examples are provided to illustrate simplicity and efficiency of the proposed approach.  相似文献   
79.
A constant trend towards more compact mechanical systems with higher power densities and increased thermo-mechanical loads emphasises the importance of the development of new design approaches and novel tribological systems. Ignoring this may cause a significant slow down in technological and industrial development. Tribotronics or active tribology based on adaptive performance is thought of as being critical in the implementation of smart machine concepts. Recognition of the importance of tribotronics, or active control of system loss outputs, such as those through friction and wear will have significant beneficial economic consequences as a result of the associated accelerated rate of technological progress. These smart tribotronic systems can be embedded in a great variety of machines and mechanisms. If this integration is made at the design stage, products that are more flexible, efficient and reliable can be produced. The concept of tribotronics is presented and discussed in this paper. Some illustrative examples that show the feasibility of an “active” approach are given. In addition, various possibilities already reported in literature are discussed.  相似文献   
80.
The Florida Department of Transportation (FDOT) is in the process of implementing Pontis, a Bridge Management System, to provide decision support to engineers in the headquarters and district offices as they make routine policy, programming, and budgeting decisions regarding the preservation and improvement of the state’s bridges. As part of this effort, an ongoing research program is underway to adapt the system to FDOT needs as well as to advance the state of the art in several areas important to the Department. Most of the research results are organized around a new project-level decision support framework that complements and builds on Pontis’ existing network-level analysis. Specific new models include accident risk and user cost due to roadway width and alignment deficiencies; user cost of load capacity and vertical clearance restrictions, and moveable bridge openings; project-level prediction models for bridge element condition and costs; and prediction of economics of scale and scoping possibilities. The new models are built into a highly graphical spreadsheet model for decision support use.  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