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   51135篇
  免费   540篇
  国内免费   790篇
电工技术   846篇
综合类   52篇
化学工业   6582篇
金属工艺   3372篇
机械仪表   1429篇
建筑科学   886篇
矿业工程   151篇
能源动力   1451篇
轻工业   2267篇
水利工程   356篇
石油天然气   1386篇
无线电   4255篇
一般工业技术   10741篇
冶金工业   7254篇
原子能技术   870篇
自动化技术   10567篇
  2021年   342篇
  2020年   276篇
  2019年   373篇
  2018年   665篇
  2017年   657篇
  2016年   743篇
  2015年   540篇
  2014年   1013篇
  2013年   2551篇
  2012年   2159篇
  2011年   4135篇
  2010年   2576篇
  2009年   2715篇
  2008年   2280篇
  2007年   2338篇
  2006年   1835篇
  2005年   1788篇
  2004年   1686篇
  2003年   1646篇
  2002年   1332篇
  2001年   1119篇
  2000年   964篇
  1999年   999篇
  1998年   2115篇
  1997年   1657篇
  1996年   1440篇
  1995年   983篇
  1994年   757篇
  1993年   774篇
  1992年   597篇
  1991年   572篇
  1990年   524篇
  1989年   485篇
  1988年   369篇
  1987年   402篇
  1986年   364篇
  1985年   381篇
  1984年   305篇
  1983年   300篇
  1982年   301篇
  1981年   296篇
  1980年   349篇
  1979年   341篇
  1978年   294篇
  1977年   415篇
  1976年   629篇
  1975年   308篇
  1974年   292篇
  1973年   311篇
  1972年   272篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
A novel technique for both online and offline computation is presented. With this technique, a reconstruction analysis in elementary particle physics, otherwise prohibitively long, has been accomplished. It will be used online in an upcoming Fermilab experiment to reconstruct more than 100000 events per second and to trigger on the basis of that information. The technique delivers 40 gigaoperations per second, has a bandwidth on the order of gigabytes per second, and has a modest cost. An overview of the program, details of the system, and performance measurements are presented  相似文献   
62.
Unsatisfactory conditions of storage of decontamination waste (DW) in the storages formed in the territory of Belarus after the Chernobyl accident require the evaluation of the level of protection of the environment and population. The potential hazard of the decontamination waste burial grounds (DWBGs) has been evaluated based on the use of a generalized multichamber model that was verified by comparing the calculation results and the results obtained by the American (GW SCREEN) model. The characteristics of the 24 largest and most hazardous DWBGs are given and the evaluations of their safety are presented. The zones of influence of these storages, whose size varies from 100 to 330 m, have been determined. The reliability of the prediction evaluation of a possible hazardous radioactive contamination of water near the storages has been verified using the Dudichi DWBG as an example.  相似文献   
63.
We formulate the inverse problem of scattering of electromagnetic fields by thin defects and analyze numerical algorithms used for its solution. It is shown that, in the two-dimensional case, the shape of a thin defect is completely determined by the scattered field given on a certain curve for a fixed value of the wave number. For the solution of the inverse scattering problem, we propose to use the procedure of iterative regularization based on the gradient methods. We deduce expressions for the Fréchet derivative of the operator of direct scattering problem with Dirichlet conditions imposed on the surface of a scatterer.  相似文献   
64.
65.
This paper presents a mathematical model that is capable of calculating the ampacity of a wide variety of power cable designs consisting of an arbitrary number of layers on a cable reel. The model considers round cables with copper conductors. The validity and accuracy of the ampacity model were verified by comparing the predicted temperature distribution within the reel with measured temperatures collected during an extensive testing program conducted at the US Bureau of Mines (USBM). The mathematical model predicted a temperature distribution within the cable layers that was very close to the measured variation in temperature. The value of the program is illustrated by calculating ampacities for several copper conductor sizes  相似文献   
66.
67.
Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 1, pp. 14–15, January, 1992.  相似文献   
68.
The optimal design of the high power plate and grid modulated selective amplifier is examined in this paper. For the analysis purposes, the linear model of constant plate current characteristics for HF power triode is applied. The carrier wave state of the unmodulated amplifier is chosen so to enable the realization of the high levels of modulation. The results are obtained immediateZy, and the estimated error is acceptable. The estimated characteristic values of this high power and high efficiency HF amplifier are shown in the corresponding diagrams.  相似文献   
69.
It has been reported that high-temperature (~1100°C) N2 O-annealed oxide can block boron penetration from poly-Si gates to the silicon substrate. However, this high-temperature step may be inappropriate for the low thermal budgets required of deep-submicron ULSI MOSFETs. Low-temperature (900~950°C) N2O-annealed gate oxide is also a good barrier to boron penetration. For the first time, the change in channel doping profile due to compensation of arsenic and boron ionized impurities was resolved using MOS C-V measurement techniques. It was found that the higher the nitrogen concentration incorporated at Si/SiO2 interface, the more effective is the suppression of boron penetration. The experimental results also suggest that, for 60~110 Å gate oxides, a certain amount of nitrogen (~2.2%) incorporated near the Si/SiO2 interface is essential to effectively prevent boron diffusing into the underlying silicon substrate  相似文献   
70.
In this study, it is demonstrated that the incorporation of fluorine can enhance poly-Si/Si interfacial oxide break-up in the poly-Si emitter contacted p+-n shallow junction formation. The annealing temperature for breaking up the poly-Si/Si interfacial oxide has been found to be as low as 900°C. As a result, the junction depth of the BF2-implanted device is much larger than that of the boron-implanted device  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