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   198951篇
  免费   2134篇
  国内免费   638篇
电工技术   4116篇
综合类   124篇
化学工业   26927篇
金属工艺   7552篇
机械仪表   5500篇
建筑科学   4073篇
矿业工程   747篇
能源动力   4689篇
轻工业   14456篇
水利工程   1702篇
石油天然气   2842篇
武器工业   7篇
无线电   27416篇
一般工业技术   37612篇
冶金工业   45606篇
原子能技术   3592篇
自动化技术   14762篇
  2021年   1260篇
  2019年   1296篇
  2018年   2150篇
  2017年   2126篇
  2016年   2197篇
  2015年   1503篇
  2014年   2635篇
  2013年   7998篇
  2012年   4508篇
  2011年   6164篇
  2010年   4973篇
  2009年   5819篇
  2008年   6191篇
  2007年   6246篇
  2006年   5669篇
  2005年   5331篇
  2004年   5278篇
  2003年   5123篇
  2002年   4928篇
  2001年   5329篇
  2000年   4930篇
  1999年   5454篇
  1998年   15699篇
  1997年   10377篇
  1996年   7970篇
  1995年   5812篇
  1994年   5036篇
  1993年   5053篇
  1992年   3395篇
  1991年   3278篇
  1990年   3220篇
  1989年   3050篇
  1988年   2795篇
  1987年   2244篇
  1986年   2310篇
  1985年   2621篇
  1984年   2328篇
  1983年   2075篇
  1982年   1915篇
  1981年   2055篇
  1980年   1800篇
  1979年   1664篇
  1978年   1664篇
  1977年   2025篇
  1976年   2714篇
  1975年   1427篇
  1974年   1374篇
  1973年   1321篇
  1972年   1130篇
  1971年   959篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
We consider a distributed source coding system in which several observations must be encoded separately and communicated to the decoder by using limited transmission rate. We introduce a robust distributed coding scheme which flexibly trades off between system robustness and compression efficiency. The optimality of this coding scheme is proved for various special cases.  相似文献   
72.
The cooling and solidification of melted drops during their movement in an immiscible cooling medium is widely employed for granulation in the chemical industry, and a study of these processes to provides a basis for the design of the granulation tower height and the temperature of the cooling medium is reported. A physical model of the cooling and solidification of the drop is established and the numerical calculation is performed. The influences of the key factors in the solidification, i.e., Bi number, drop diameter, temperature of the cooling medium, etc. are presented. The cooling and solidification during wax granulation in a water‐cooling tower and during urea granulation in an air‐cooling tower (spraying tower) are described in detail. Characteristics of the solidification and temperature distribution within the particle at different times are shown. The model and calculations can be used for structure design of the granulation tower and optimization of the operation parameters.  相似文献   
73.
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   
74.
75.
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   
76.
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   
77.
78.
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   
79.
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