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   19568篇
  免费   1095篇
  国内免费   346篇
电工技术   693篇
技术理论   1篇
综合类   1690篇
化学工业   2639篇
金属工艺   455篇
机械仪表   756篇
建筑科学   1983篇
矿业工程   436篇
能源动力   382篇
轻工业   2075篇
水利工程   283篇
石油天然气   330篇
武器工业   73篇
无线电   860篇
一般工业技术   2947篇
冶金工业   964篇
原子能技术   143篇
自动化技术   4299篇
  2025年   83篇
  2024年   301篇
  2023年   290篇
  2022年   316篇
  2021年   423篇
  2020年   509篇
  2019年   525篇
  2018年   449篇
  2017年   553篇
  2016年   605篇
  2015年   643篇
  2014年   1101篇
  2013年   1125篇
  2012年   1459篇
  2011年   1488篇
  2010年   1124篇
  2009年   1129篇
  2008年   942篇
  2007年   1135篇
  2006年   962篇
  2005年   811篇
  2004年   720篇
  2003年   640篇
  2002年   540篇
  2001年   415篇
  2000年   340篇
  1999年   320篇
  1998年   276篇
  1997年   229篇
  1996年   171篇
  1995年   184篇
  1994年   125篇
  1993年   112篇
  1992年   87篇
  1991年   65篇
  1990年   67篇
  1989年   76篇
  1988年   79篇
  1987年   46篇
  1986年   43篇
  1985年   60篇
  1984年   73篇
  1983年   89篇
  1982年   90篇
  1981年   29篇
  1980年   30篇
  1979年   21篇
  1978年   19篇
  1977年   17篇
  1955年   11篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Work system improvements are implemented in various manufacturing processes to prevent problems caused by human errors. However, they are almost always applied to problems which have already occurred. This paper examines a method of identifying latent human errors existing within the work systems beforehand. A procedure for applying failure mode and effect analysis to this identification problem was defined based on over 1000 empirical errors: a work system decomposition criterion and fundamental error modes for listing latent human errors, and then applied to three practical manufacturing processes in order to evaluate its effectiveness.  相似文献   
2.
3.
4.
This article is the second of two papers that review the field of spatially sensitive social scientific research into the links between social status and transport disadvantage. The first paper undertook a comprehensive review of the social scientific and transport planning literature to mark the level of development in the field and identify conceptual and methodological issues and constraints in this field of inquiry. The present article supports the advancement of socially and geographically sensitive transport research by opportunities for the development of more sophisticated spatial analytical methodologies. The approach we present is able to account for factors not previously addressed in either social or transport planning research, in particular the temporal dimensions of transport service accessibility. The article articulates the methodology through an empirical case study of socio-spatial transport disadvantage within the Gold Coast City. The article demonstrates that there are important theoretical and practical lessons to be gained for researchers and policy makers in addressing the social dimensions of transport and infrastructure provision. Further, the article argues that an attentiveness to new ways of combining and representing social and transport data-sets can promote policy relevant empirical social inquiry. The article also contributes in a productive way to the empirical knowledge of Australia's sixth-largest metropolitan area, which is often overlooked by urban scholars.  相似文献   
5.
6.
Because of the growing demand for increasingly complex computer-based systems there is now an urgent need to provide tools to assist during the design of such systems. Formal specifications and formal methods provide such assistance but their widespread adoption has been hindered by the so-called ‘math fear’ and the perception that the tools are too difficult, too time consuming and too costly to use in a commercial environment. The aim of this article is to dispel the mystery surrounding the topic and to explain what formal methods are, how and why they are used, the benefits that accrue and why the technology should be accepted on a broader front. The application of formal methods to the design of computer-based systems will be discussed without resorting to jargon or mathematics. The discussion will concentrate more on the software content of systems but the arguments apply equally well to hardware. Some of the available tools will also be introduced.  相似文献   
7.
8.
9.
Dental amalgams are based on a broad spectrum of materials differing in their chemical composition, metallurgical treatment, and in the way the initial alloys powders are prepared. In addition to their chemical composition, amalgams based on various powders differ in both their microstructure and the amount of mercury needed for preparation. All these facts may affect electrochemical processes occurring during their interaction with oral fluids, and also mercury release. While verifying the effect of the technology used for the preparation of the high‐copper ternary alloy powder on the properties of resulting amalgams, this study aimed at the mechanism of their interaction with a model saliva solution as well as mercury release was included. Measurements were done in a model saliva solution using standard electrochemical methods and exposition measurements. The interaction of individual types of amalgams with artificial saliva did not reveal any significant differences. The free corrosion potential of all these amalgams in an aerated solution settled in the range of values in which tin oxidation, resulting in a layer of insoluble corrosion producsts, turned out to be the dominant anodic process. The rate of mercury release was the lowest for amalgams based on a gas‐atomized alloy. The highest rate of mercury release, and also its dependence on time, was exhibited by lathe‐cut powder based amalgam. In addition to different volume fraction of the Ag‐Hg phase and the level of its tin alloying, this different behaviour may be explained by differences in the rate at which a layer of tin corrosion products acting as a barrier to mercury release is formed.  相似文献   
10.
This paper reports a study undertaken using techniques of static and dynamic light scattering to investigate the influence of sodium salicylate and methyl salicylate on droplet size of oil-in-water emulsions. The rates of changes were measured by determining the size and distribution of the oil droplet in the material. All emulsions showed a bimodal size distribution; the mean diameters and polydispersity were calculated from intensity. These data were analyzed with nonlinear regressions and bootstrap methodology. An amount of methyl salicylate component induced a decrease of mean diameter and standard deviation. On the contrary, sodium salicylate entailed the growth of all droplet populations and coalescence for the highest concentration.  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