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   287834篇
  免费   3067篇
  国内免费   817篇
电工技术   5036篇
综合类   163篇
化学工业   45446篇
金属工艺   11898篇
机械仪表   8613篇
建筑科学   6865篇
矿业工程   1836篇
能源动力   6741篇
轻工业   25922篇
水利工程   3190篇
石油天然气   7089篇
武器工业   16篇
无线电   31473篇
一般工业技术   56984篇
冶金工业   51418篇
原子能技术   7533篇
自动化技术   21495篇
  2021年   2102篇
  2018年   3675篇
  2017年   3625篇
  2016年   3905篇
  2015年   2468篇
  2014年   4239篇
  2013年   12031篇
  2012年   6832篇
  2011年   9222篇
  2010年   7575篇
  2009年   8652篇
  2008年   8937篇
  2007年   8817篇
  2006年   7830篇
  2005年   7312篇
  2004年   6806篇
  2003年   6560篇
  2002年   6634篇
  2001年   6506篇
  2000年   6178篇
  1999年   6234篇
  1998年   14763篇
  1997年   11042篇
  1996年   8575篇
  1995年   6532篇
  1994年   5920篇
  1993年   5792篇
  1992年   4480篇
  1991年   4440篇
  1990年   4289篇
  1989年   4304篇
  1988年   4259篇
  1987年   3599篇
  1986年   3599篇
  1985年   4165篇
  1984年   3968篇
  1983年   3623篇
  1982年   3423篇
  1981年   3563篇
  1980年   3424篇
  1979年   3366篇
  1978年   3449篇
  1977年   3924篇
  1976年   5043篇
  1975年   3159篇
  1974年   3008篇
  1973年   3025篇
  1972年   2652篇
  1971年   2476篇
  1970年   2104篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Sol–gel films are actively investigated during the last decade as possible candidates for environmentally friendly pre-treatments. However, the important drawback in this case is the lack of active corrosion protection and self-healing ability.  相似文献   
82.
Heat resistant coatings are required primarily for stacks, exhaust pipes, reactors, space crafts and similar equipments that are permanently or occasionally exposed to elevated temperatures. High-temperature coatings are generally based on silicone resin with ceramic and metallic pigments. In this study, iron oxide, cobalt oxide (thermo chromic compound) and aluminum oxide are used for the preparation of four new types of coloured pigments. The thermal resistant characteristics of these ceramic pigments were studied by differential thermal analysis, thermo gravimetric analysis and differential scanning calorimetric analysis. These ceramic pigments are found to be thermally stable up to 400 °C.  相似文献   
83.
84.
Complexation of chitosan in aqueous solutions by low molecular weight electrolytes is one of the simplest methods for the preparation of aqueous chitosan dispersions. In this work, the influence of storage time, sulfate concentration, method of preparation and surfactant content on some properties of the resultant chitosan dispersions (turbidity, viscosity and zeta potential) was analyzed. Turbidimetry was adequate to monitor the formation of particles, while viscometry was suitable to monitor changes in the dispersing phase. An analysis of the properties of these systems, mainly in terms of particle–particle and macromolecule–macromolecule interactions was carried out. Copyright © 2004 Society of Chemical Industry  相似文献   
85.
The latest developments and in particular important synthetic aspects for the preparation of modern poly(styrene‐divinylbenzene) (PS‐DVB) based liquid chromatography (LC) supports are reviewed. In this context, the chemistry of particular porous and nonporous, functionalized, monolithic, coated silica and more specialized mixed organic PS‐DVB media is covered. Special consideration is given to modern approaches such as micro‐(μ)‐HPLC and coating techniques and their most important applications. Synthetic particularities relevant to the corresponding applications are outlined.  相似文献   
86.
87.
The purpose of this paper is to provide an analysis of the alternative modelling systems for office information systems. More specifically, we are interested in identifying the current research trends of merging office modelling ideas together with concepts that owe their origin to the object-oriented paradigm and to artificial intelligence. In this respect an office model is defined as encompassing three domains: passive office objects; dynamically defined and manipulated office procedures; and goal-directed office tasks. Following this definition we exploit the potential of using the object-oriented and knowledge representation techniques for modelling each of the three domains using evidence from real-world applications.  相似文献   
88.
89.
90.
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