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   288421篇
  免费   3135篇
  国内免费   817篇
电工技术   5034篇
综合类   165篇
化学工业   45555篇
金属工艺   11914篇
机械仪表   8617篇
建筑科学   6894篇
矿业工程   1837篇
能源动力   6781篇
轻工业   25960篇
水利工程   3202篇
石油天然气   7089篇
武器工业   16篇
无线电   31506篇
一般工业技术   57133篇
冶金工业   51542篇
原子能技术   7538篇
自动化技术   21590篇
  2021年   2122篇
  2018年   3710篇
  2017年   3654篇
  2016年   3946篇
  2015年   2486篇
  2014年   4269篇
  2013年   12079篇
  2012年   6896篇
  2011年   9273篇
  2010年   7611篇
  2009年   8675篇
  2008年   8965篇
  2007年   8852篇
  2006年   7850篇
  2005年   7329篇
  2004年   6812篇
  2003年   6567篇
  2002年   6639篇
  2001年   6508篇
  2000年   6185篇
  1999年   6239篇
  1998年   14782篇
  1997年   11047篇
  1996年   8580篇
  1995年   6535篇
  1994年   5924篇
  1993年   5798篇
  1992年   4488篇
  1991年   4444篇
  1990年   4289篇
  1989年   4307篇
  1988年   4259篇
  1987年   3600篇
  1986年   3597篇
  1985年   4163篇
  1984年   3969篇
  1983年   3624篇
  1982年   3427篇
  1981年   3562篇
  1980年   3424篇
  1979年   3368篇
  1978年   3448篇
  1977年   3927篇
  1976年   5044篇
  1975年   3161篇
  1974年   3009篇
  1973年   3028篇
  1972年   2652篇
  1971年   2475篇
  1970年   2107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