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   1531篇
  免费   34篇
电工技术   15篇
化学工业   283篇
金属工艺   25篇
机械仪表   29篇
建筑科学   79篇
矿业工程   17篇
能源动力   36篇
轻工业   132篇
水利工程   7篇
石油天然气   8篇
武器工业   1篇
无线电   108篇
一般工业技术   186篇
冶金工业   388篇
原子能技术   11篇
自动化技术   240篇
  2022年   8篇
  2021年   9篇
  2020年   9篇
  2019年   11篇
  2018年   17篇
  2017年   12篇
  2016年   19篇
  2015年   26篇
  2014年   29篇
  2013年   90篇
  2012年   46篇
  2011年   71篇
  2010年   50篇
  2009年   73篇
  2008年   56篇
  2007年   63篇
  2006年   72篇
  2005年   66篇
  2004年   64篇
  2003年   48篇
  2002年   54篇
  2001年   45篇
  2000年   33篇
  1999年   33篇
  1998年   43篇
  1997年   43篇
  1996年   40篇
  1995年   25篇
  1994年   30篇
  1993年   28篇
  1992年   30篇
  1991年   12篇
  1990年   28篇
  1989年   12篇
  1988年   10篇
  1987年   15篇
  1986年   18篇
  1985年   23篇
  1984年   25篇
  1983年   22篇
  1982年   15篇
  1981年   13篇
  1980年   11篇
  1979年   14篇
  1978年   11篇
  1977年   13篇
  1976年   21篇
  1975年   10篇
  1974年   9篇
  1973年   10篇
排序方式: 共有1565条查询结果,搜索用时 147 毫秒
1.
2.
Terry.lee 《程序员》2004,(4):21-22
本部分将讲述PortletConfig对象及其PortletContext对象的概念及应用。  相似文献   
3.
Several N-(phosphonomethyl) amides have previously been reported to act as particularly effective flame retardants for cellulose. It has also been demonstrated previously that the efficiency of a flame retardant on cellulose frequently parallels its ability to phosphorylate cellulosic hydroxyls at elevated temperatures. This study of the hydrolysis and alcoholysis reactions of N-(phosphonomethyl) amides establishes their unique reactivity. An explanation for this high reactivity is proposed on the basis of intramolecular assistance of the attack of water or alcohols at phosphorus by the carbonyl oxygen of the amide moiety.  相似文献   
4.
5.
We have devised a new scheme for coding designers' cognitive actions from video/audio design protocols. Designers' actions are coded into four cognitive levels; physical, perceptual, functional and conceptual. Relations between actions belonging to different levels, such as dependencies and triggering relations, are also coded. The present scheme has two benefits. First, we found that design actions are definable in a systematic way using the vocabulary of the scheme, and thus a designer's cognitive behaviours in each of local design stages is represented as a structure composed of defined primitive actions. This is expected to lay the foundation for microscopic analyses of how particular types of actions contribute to the formation of key design ideas. Second, this scheme is suitable for macroscopic analyses of how designers cognitively interact with their own sketches. We examined, for a practising architect, the ways in which drawing, inspection of drawings, perception, and functional thoughts correlated with one another in his design process. The findings suggest that design sketches serve not only as external memory or as a provider of visual cues for association of non-visual information, but also as a physical setting in which design thoughts are constructed on the fly.  相似文献   
6.
7.
8.
Various measures, such as Margin and Bias/Variance, have been proposed with the aim of gaining a better understanding of why Multiple Classifier Systems (MCS) perform as well as they do. While these measures provide different perspectives for MCS analysis, it is not clear how to use them for MCS design. In this paper a different measure based on a spectral representation is proposed for two-class problems. It incorporates terms representing positive and negative correlation of pairs of training patterns with respect to class labels. Experiments employing MLP base classifiers, in which parameters are fixed but systematically varied, demonstrate the sensitivity of the proposed measure to base classifier complexity.  相似文献   
9.
Models and methods are presented for determining practical limits of the packing density of TRISO particles in fuel pebbles for a pebble-bed reactor (PBR). These models are devised for designing and interpreting fuel testing experiments. Two processes for particle failure are accounted for: failure of touching particles at the pressing stage in the pebble manufacturing process and failure due to inner pressure buildup during irradiation. The second process gains importance with increasing fuel temperature, which limits the particle packing density and the corresponding fuel enrichment. Suggestions for improvements to the models are presented.  相似文献   
10.
The lattice constants of boron carbides have been determined by powder X-ray diffraction for samples with compositions between about 7.7 and 20.5 at.% carbon. The boundaries of the single-phase region are at about 9 at.% carbon and near, but likely somewhat less than, 20 at.% carbon. The composition dependence of the lattice constants thus established provides a method of assessing the carbon concentration of unknown materials. In particular, assignment of the approximate composition of single crystals used in previous studies allows for a systematic examination of changes in interatomic separation as a function of composition. These changes are discussed in terms of a structural model of the boron carbide solid solution.  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