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   70476篇
  免费   3403篇
  国内免费   2197篇
电工技术   2526篇
综合类   2030篇
化学工业   10678篇
金属工艺   4633篇
机械仪表   3249篇
建筑科学   3137篇
矿业工程   1112篇
能源动力   2317篇
轻工业   4443篇
水利工程   937篇
石油天然气   2938篇
武器工业   259篇
无线电   7380篇
一般工业技术   14093篇
冶金工业   8428篇
原子能技术   1153篇
自动化技术   6763篇
  2023年   707篇
  2022年   1406篇
  2021年   2004篇
  2020年   1556篇
  2019年   1435篇
  2018年   1758篇
  2017年   1809篇
  2016年   1792篇
  2015年   2047篇
  2014年   2534篇
  2013年   4347篇
  2012年   3448篇
  2011年   3883篇
  2010年   3197篇
  2009年   3422篇
  2008年   3205篇
  2007年   3202篇
  2006年   2769篇
  2005年   2377篇
  2004年   1978篇
  2003年   1659篇
  2002年   1623篇
  2001年   1559篇
  2000年   1403篇
  1999年   1467篇
  1998年   2473篇
  1997年   1954篇
  1996年   1712篇
  1995年   1207篇
  1994年   954篇
  1993年   886篇
  1992年   687篇
  1991年   648篇
  1990年   582篇
  1989年   534篇
  1988年   400篇
  1987年   433篇
  1986年   392篇
  1985年   388篇
  1984年   314篇
  1983年   306篇
  1982年   308篇
  1981年   306篇
  1980年   356篇
  1979年   342篇
  1978年   295篇
  1977年   416篇
  1976年   631篇
  1975年   309篇
  1973年   312篇
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
71.
Worsening of the environmental situation in many regions of Russia in recent decades is to a great degree due to production and refining of oil and gas with a high hydrogen sulfide content. Industrial methods of utilization of hydrogen sulfide are extremely irrational: it is either burned in flares or used for production of sulfur whose quality and quantity pose new problems related to its use.  相似文献   
72.
The microscopic structures of PLZT(7.9/70/30 and x/65/35, x = 7 or 8) ceramics were studied by means of transmission electron microscopy. The presence of micro-regions in PLZTs was first verfied.  相似文献   
73.
74.
Strain endurance experiments on a filled elastomer were performed at several temperatures. It was found that superimposed prestraining accelerated the ageing process. This process was caused by microstructural changes in the elastomer. In order to evaluate the mechanical properties of a filled elastomer it is necessary to take into consideration not only the ageing effects but also the loading history.  相似文献   
75.
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   
76.
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   
77.
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   
78.
79.
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   
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