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   251039篇
  免费   6253篇
  国内免费   2622篇
电工技术   6827篇
技术理论   5篇
综合类   3115篇
化学工业   36005篇
金属工艺   10684篇
机械仪表   8678篇
建筑科学   7837篇
矿业工程   2502篇
能源动力   6332篇
轻工业   18121篇
水利工程   2563篇
石油天然气   6613篇
武器工业   403篇
无线电   32927篇
一般工业技术   43669篇
冶金工业   48340篇
原子能技术   4207篇
自动化技术   21086篇
  2022年   2342篇
  2021年   3560篇
  2020年   2605篇
  2019年   2725篇
  2018年   3778篇
  2017年   3890篇
  2016年   3769篇
  2015年   3577篇
  2014年   5294篇
  2013年   11035篇
  2012年   7740篇
  2011年   9689篇
  2010年   8110篇
  2009年   8608篇
  2008年   8927篇
  2007年   8906篇
  2006年   8502篇
  2005年   7756篇
  2004年   6769篇
  2003年   6425篇
  2002年   6155篇
  2001年   6293篇
  2000年   6098篇
  1999年   6889篇
  1998年   16761篇
  1997年   11306篇
  1996年   8926篇
  1995年   6658篇
  1994年   5708篇
  1993年   5478篇
  1992年   3740篇
  1991年   3551篇
  1990年   3451篇
  1989年   3229篇
  1988年   2953篇
  1987年   2344篇
  1986年   2396篇
  1985年   2664篇
  1984年   2365篇
  1983年   2099篇
  1982年   1933篇
  1981年   2071篇
  1980年   1807篇
  1979年   1665篇
  1978年   1663篇
  1977年   2029篇
  1976年   2715篇
  1975年   1426篇
  1974年   1370篇
  1973年   1318篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
ProKappa is an expert system tool kit developed by IntelliCorp in C using X-Windows for graphical interface. The SUN 3 or 4 version costs $9995/£7000 and $2595/£1800 for the interactive C environment.
This review covers ProKappa version 1.1, installed on a colour SUN SPARC Station 1 with the minimum recommended values of 12 Mb of memory and 30 Mb of swap space.
IntelliCorp can be contacted in the USA at 1975 El Camino Real West, Mountain View, CA 94040-2216 (+1 (415) 965-5500) and in the UK at 10 Jewry Street, Winchester, Hampshire SO23 8RZ (+44 (0)962 735348).  相似文献   
62.
63.
We present measurements of the electron, positive ion, and photon emission accompanying the fracture in vacuum of poly-crystalline 95/5 lead zirconate-titanate. The intensities of the charged-particle components of this fractoemission are shown to depend strongly on the direction (relative to the direction of fracture) and magnitude of polarization. The most intense emission is observed when the fracture surfaces are perpendicular to the polarization direction. The emission intensity increases monotonically with polarization. These results are interpreted in terms of a model involving charge separation on the fracture surfaces leading to a microdischarge during fracture. Implications to the interpretation of triboluminesence effects are discussed.  相似文献   
64.
The results presented in the literature, which attempt to elucidate the mechanisms by which triglyceride oils are bleached by earths, are reviewed. The impact of this work and how the mechanistic proposals affect changes in oil properties are considered, with particular emphasis on the needs of the palm oil processor. Important properties include color, metals and phosphorus content and oxidative stability of the oil. Investigations made in our own laboratories have been aimed at elucidating the effect of varying physical and chemical properties of the bleaching earth on the quality of bleached and deodorized oils. Techniques used in this work are pore-size distribution, surface area, scanning and transmission electron microscopy and a variety of chemical and X-ray analysis methods. The ability to vary such parameters in montmorillonite clays by alteration of process conditions to give materials with specific performance characteristics is demonstrated. Comparisons are made between acid-activated montmorillonites and other clay types.  相似文献   
65.
66.
The influence of liquid penetration at grain boundary regions on the rate of advance of the solid-liquid interface during isothermal solidification of transient liquid phase (TLP) brazed nickel joints has been examined. The test samples used in this study were Ohno-cast nickel with a grain size of >4 mm and a fine-grained nickel with a grain size of around 40 μm. Both Ni-base materials had the same chemical composition. The rate of isothermal solidification was greater when fine-grained nickel was employed during TLP brazing using Ni-11 wt pct P filler metal at 1200 °C. Liquid penetration at grain boundaries accelerates the isothermal solidification process by increasing the effective solid-liquid interfacial area and increasing the rate of solute diffusion into the base material. An analysis of electron channeling patterns has confirmed that random high-angle boundaries have a greater influence on the rate of isothermal solidification than ordered boundaries including small-angle or twin boundaries. Formerly Visiting Scientist, Department of Metallurgy and Materials Science, University of Toronto. Formerly Postdoctoral Fellow, Department of Metallurgy and Materials Science, University of Toronto  相似文献   
67.
68.
本文评价了塑料闪烁片用作软β核素探测器时的计数效率、β谱、本底谱和康普顿电子谱的特征。文中强调:采用胶合光导剂构成的系统是一种新型探测器(软β核素内部样品塑料闪烁探测器)。本文提出内部样品固体探测器、胶合光导剂和胶合闪烁光导剂的新概念。  相似文献   
69.
70.
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