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   486467篇
  免费   23752篇
  国内免费   11562篇
电工技术   18815篇
技术理论   31篇
综合类   17573篇
化学工业   78824篇
金属工艺   24610篇
机械仪表   24403篇
建筑科学   27633篇
矿业工程   10822篇
能源动力   12997篇
轻工业   33673篇
水利工程   7060篇
石油天然气   24257篇
武器工业   2242篇
无线电   54152篇
一般工业技术   73497篇
冶金工业   52216篇
原子能技术   7896篇
自动化技术   51080篇
  2023年   5061篇
  2022年   8828篇
  2021年   12997篇
  2020年   9642篇
  2019年   8791篇
  2018年   10668篇
  2017年   11795篇
  2016年   10746篇
  2015年   12903篇
  2014年   16769篇
  2013年   25208篇
  2012年   22646篇
  2011年   26233篇
  2010年   22171篇
  2009年   22076篇
  2008年   21744篇
  2007年   21434篇
  2006年   21429篇
  2005年   19267篇
  2004年   13955篇
  2003年   12692篇
  2002年   11748篇
  2001年   11057篇
  2000年   11611篇
  1999年   13157篇
  1998年   18132篇
  1997年   13868篇
  1996年   11784篇
  1995年   9129篇
  1994年   7979篇
  1993年   6682篇
  1992年   5347篇
  1991年   4656篇
  1990年   4032篇
  1989年   3869篇
  1988年   3578篇
  1987年   2919篇
  1986年   2694篇
  1985年   2975篇
  1984年   2687篇
  1983年   2464篇
  1982年   2219篇
  1981年   2289篇
  1980年   2099篇
  1979年   2148篇
  1978年   2122篇
  1977年   2366篇
  1976年   3188篇
  1975年   1833篇
  1973年   1772篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
在实验室条件下对用丙烯腈-苯乙烯共聚物在硫酸存在下的水解磺化产物(HSAS)处理的泥浆性能进行了评定。HSAS处理的泥浆有较小的滤失性,较好的耐盐和抗高温性。  相似文献   
122.
An instrument is proposed for continuously tracking the Sun and measuring its height by the use of a laser gyrometer as measuring converter. The accuracy in photoelectric sighting on the Sun is improved by greatly reducing the light fluxes to be compared by screening out the central part of the Sun's image in the focal plane. Translated from Izmeritel'naya Tekhnika, No. 3, pp. 7–9, March, 1994.  相似文献   
123.
The authors survey published results on the application of metal diffraction gratings as laser power or energy dividers when the laser beam is split into two approximately equal pans. The normal incidence of laser radiation on metal diffraction gratings of various profiles in the case of three propagating diffraction orders n=0, ±1 is discussed, along with the case of oblique incidence with only two propagating diffraction orders n=0 and n =–1.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 22–26, February, 1994.  相似文献   
124.
The mass and charge identification of secondary particles with Z < 4 by a large CsI(T1) scintillation detector is performed using pulse shape analysis and time-of-flight methods. The dependence of the light output on E, A and Z is studied in the energy range of 1–20 MeV/A and special attention is paid to the integration time of the photomultiplier anode signal. It is found that the behaviour of the calibration curves strongly depends on the choice of the integration time interval.  相似文献   
125.
126.
The users' interest can be mined from the web cache and can be used widely. The interest can be specialized by the two-tuple (term, weight) in the simple interest model, in which the association relations are not mined, and then the interest cannot be associated in expressing the users' interest. Based on analyzing the WWW cache model, this letter brings forward a two-dimensional interest model and gives the interrelated methods on how to store the two-dimensional interest model effectively.  相似文献   
127.
A modification to the `shape-invariant' sinusoidal speech model is proposed, whereby the phases of the component sinewaves used for the excitation are made to add coherently at each glottal closure. Applied to pitch and time-scale modification, higher quality synthetic speech is produced when large changes are required  相似文献   
128.
游梁式抽油机二次平衡分析   总被引:1,自引:0,他引:1  
张春雨  乔国维 《石油机械》1998,26(11):40-41,50
为解决游梁式抽油机能耗大、效率低的问题,设计了二次平衡装置。这种装置通过是挂在抽油机后端的平衡重的平衡作用,降低一次平衡曲柄轴净扭矩的两个峰值,达到减少能耗提高效率的目的。对抽油机的二次平衡作了较详尽的理论分析,给出了实行二次平衡后曲柄轴净扭矩的计算公式和安装二次平衡装置前后曲柄轴净扭矩曲线图。在大庆油田两口井上进行的现场试验结果表明,安装二次平衡装置后,两口井年节约电费分别为0.25万元和1.17万元,经济效益明显。  相似文献   
129.
Presents the Satellite Communications Network Expert (SaNE), a knowledge-based aid designed to provide engineering support for fault diagnosis. The SaNE is composed of two elements: a satcom network model, which simulates the structure and functionality of a system based loosely upon a large military satcom network, and a diagnostic component, which uses knowledge- and model-based reasoning techniques to analyse system anomalies and diagnose possible causes for the alarms such networks generate. The development cycle is described, emphasising lessons learnt during development and testing and the advantages and disadvantages of the techniques applied. The goal of the SaNE project is primarily commercial acceptance rather than innovation. The authors illustrate how novel concepts can be implemented in a practical system without compromising this goal  相似文献   
130.
Dissolved organic carbon (DOC) dynamics were investigated over a two year period in the Upper Rhǒne River to examine the role of side-arms in providing DOC to the main channel in relation to discharge fluctuations, especially floods. Concentrations of DOC are shown to remain low in space and in time (average 1.5 mg ?1) and to be more related to global hydrological events (precipitation) than to any local flushing for backwaters during floods. The results do not support the general assumption that side-arms are the providers of DOC to the main channel.  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