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   105962篇
  免费   1681篇
  国内免费   1227篇
电工技术   1952篇
综合类   140篇
化学工业   11271篇
金属工艺   5538篇
机械仪表   3282篇
建筑科学   2162篇
矿业工程   168篇
能源动力   3203篇
轻工业   6582篇
水利工程   726篇
石油天然气   685篇
武器工业   15篇
无线电   16094篇
一般工业技术   22268篇
冶金工业   25543篇
原子能技术   1443篇
自动化技术   7798篇
  2022年   522篇
  2021年   835篇
  2020年   628篇
  2019年   771篇
  2018年   1300篇
  2017年   1254篇
  2016年   1356篇
  2015年   1033篇
  2014年   1628篇
  2013年   5084篇
  2012年   2750篇
  2011年   4035篇
  2010年   3294篇
  2009年   3896篇
  2008年   4046篇
  2007年   4231篇
  2006年   3782篇
  2005年   3375篇
  2004年   3227篇
  2003年   3063篇
  2002年   2701篇
  2001年   2998篇
  2000年   2734篇
  1999年   3106篇
  1998年   9545篇
  1997年   6203篇
  1996年   4810篇
  1995年   3189篇
  1994年   2801篇
  1993年   2733篇
  1992年   1637篇
  1991年   1599篇
  1990年   1524篇
  1989年   1331篇
  1988年   1181篇
  1987年   865篇
  1986年   892篇
  1985年   922篇
  1984年   806篇
  1983年   702篇
  1982年   707篇
  1981年   687篇
  1980年   577篇
  1979年   484篇
  1978年   416篇
  1977年   541篇
  1976年   978篇
  1975年   302篇
  1974年   278篇
  1973年   258篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
992.
Watermarking for intellectual property protection   总被引:1,自引:0,他引:1  
Fan  Y.C. Tsao  H.W. 《Electronics letters》2003,39(18):1316-1318
A new watermarking method for intellectual property (IP) protection is presented. The proposed method uses a uniquely generated stream of bits, known as a watermark, embedded into the self-test circuit to represent ownership. This scheme can detect the ownership rights of the IP provider even when the chip has been packaged. Experimental results show the proposed embedding technique can survive synthesis, placement and routing. The experimental results are given to demonstrate the proposed method.  相似文献   
993.
994.
An eigenanalysis interference canceler   总被引:4,自引:0,他引:4  
Eigenanalysis methods are applied to interference cancellation problems. While with common array processing methods the cancellation is effected by global optimization procedures that include the interferences and the background noise, the proposed technique focuses on the interferences only, resulting in superior cancellation performance. Furthermore, the method achieves full effectiveness even for short observation times, when the number of samples used for processing is of the the order of the number of interferences. Adaptive implementation is obtained with a simple, fast converging algorithm  相似文献   
995.
The performances of a hydrogen-fueled gas turbine cycle equipped with an intercooler, regenerator, hydrogen turbine and recuperative hydrogen heater are analyzed. The intercooler is very effective to prevent the condensation and freezing of water vapor in cooling the suction air. The operation of hydrogen turbine in low-temperature range can also be prevented by adopting hydrogen heater. Thermodynamic analysis has revealed that the thermal efficiency and the specific output are considerably improved compared to those of the simple gas turbine cycle.  相似文献   
996.
Previous studies have found that in American culture high-arousal positive states (HAP) such as excitement are valued more and low-arousal positive states (LAP) such as calm are valued less than they are in Chinese culture. What specific factors account for these differences? The authors predicted that when people and cultures aimed to influence others (i.e., assert personal needs and change others' behaviors to meet those needs), they would value HAP more and LAP less than when they aimed to adjust to others (i.e., suppress personal needs and change their own behaviors to meet others' needs). They test these predictions in 1 survey and 3 experimental studies. The findings suggest that within and across American and Chinese contexts, differences in ideal affect are due to specific interpersonal goals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
997.
The growth of allotriomorphic ferrite from austenite in Fe-C-X alloys is studied. Two systems have been selected: the Fe-C-Ni system, in which the substitutional alloying element is expected to have a weak interaction with both the C and the moving interface, and the Fe-C-Mo system, in which these interactions are expected to be non-negligible. The ferrite growth kinetics was measured using two types of experiments: classical isothermal heat treatments and decarburization experiments. All of the experimental observations can be quantitatively rationalized using a model that describes an evolution in interfacial conditions from paraequilibrium (PE) to local equilibrium with negligible partitioning (LENP) during growth. This article is based on a presentation made in the “Hillert Symposium on Thermodynamics & Kinetics of Migrating Interfaces in Steels and Other Complex Alloys,” December 2–3, 2004, organized by the The Royal Institute of Technology in Stockholm, Sweden.  相似文献   
998.
The addition of steel fibres to plain concrete is intended both to improve the material's ductility and that of the structure in which it is used. These two effects of steel fibres are clearly distinguishable through an analysis of cracking both at a local and a global level. This analysis is essential if the use of steel fibres is to be optimized.  相似文献   
999.
1000.
Intracavity Raman lasers   总被引:1,自引:0,他引:1  
Experimental and theoretical studies of intracavity Raman lasers are presented. Advantages of intracavity Raman lasers, particularly for low-emission cross section and broadly tunable vibronic gain media, are described. Experimental studies of a hydrogen gas Raman laser pumped inside the cavity of an alexandrite laser are presented. A theoretical model of the dynamics of a unidirectional intracavity Raman ring laser is developed and solved analytically. This model is adapted for simulation experiments  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