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   19747篇
  免费   1043篇
  国内免费   633篇
电工技术   659篇
综合类   516篇
化学工业   1740篇
金属工艺   1114篇
机械仪表   537篇
建筑科学   887篇
矿业工程   300篇
能源动力   346篇
轻工业   811篇
水利工程   238篇
石油天然气   335篇
武器工业   65篇
无线电   1737篇
一般工业技术   1418篇
冶金工业   586篇
原子能技术   171篇
自动化技术   9963篇
  2024年   34篇
  2023年   137篇
  2022年   255篇
  2021年   371篇
  2020年   288篇
  2019年   274篇
  2018年   290篇
  2017年   313篇
  2016年   344篇
  2015年   377篇
  2014年   674篇
  2013年   899篇
  2012年   1336篇
  2011年   3697篇
  2010年   1650篇
  2009年   1513篇
  2008年   1136篇
  2007年   1006篇
  2006年   894篇
  2005年   998篇
  2004年   909篇
  2003年   943篇
  2002年   574篇
  2001年   496篇
  2000年   414篇
  1999年   233篇
  1998年   259篇
  1997年   186篇
  1996年   132篇
  1995年   151篇
  1994年   119篇
  1993年   80篇
  1992年   39篇
  1991年   51篇
  1990年   40篇
  1989年   52篇
  1988年   33篇
  1987年   18篇
  1986年   20篇
  1985年   18篇
  1984年   41篇
  1983年   20篇
  1982年   18篇
  1981年   18篇
  1980年   11篇
  1979年   9篇
  1978年   7篇
  1977年   7篇
  1974年   6篇
  1973年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
This paper sketches the contours of the evolving international/monetary system and examines the various roles of the intemediation mechanisms. Then it examines the extent to which the financial system is independent from the “real economy” and the various ways in which it impacts it. The paper discusses some views in good currency on the dynamics of the technology-trade-finance nexus and shows how the financial system influences organization, location and technology choices in meso-innovation systems. The final section of the paper looks at the policy implications that might be derived from the analysis and suggests some directions for the future research.  相似文献   
42.
本文针对黄河拉西瓦地下水电站工程,对节理岩体诸参数对围岩破损区范围的影响进行了敏感性分析。指出了主要敏感参数,对这些参数影响围岩破损区的趋势和可能程度进行了讨论,并对勘察和施工提出了一些意见。  相似文献   
43.
44.
45.
China's electric power reform has followed the western reform format, however, it doest not seem to have endorsed the liberalization ideology underlying the reform model. This raises the concern of whether and how a competitive power market may be established and reform objectives reached. The new market competition model is easy to build in theory. The experience of many countries suggests that the market reform is extremely difficult because of the interruptions by different interest groups. To transform a centrally planned power sector into a competitive power market is a daunting task. Policy makers need to take into consideration the transitional nature of the economy and power industry as they implement the competitive power market model.  相似文献   
46.
The selection of valuable features is crucial in pattern recognition. In this paper we deal with the issue that part of features originate from directional instead of common linear data. Both for directional and linear data a theory for a statistical modeling exists. However, none of these theories gives an integrated solution to problems, where linear and directional variables are to be combined in a single, multivariate probability density function. We describe a general approach for a unified statistical modeling, given the constraint that variances of the circular variables are small. The method is practically evaluated in the context of our online handwriting recognition system frog on hand and the so-called tangent slope angle feature. Recognition results are compared with two alternative modeling approaches. The proposed solution gives significant improvements in recognition accuracy, computational speed and memory requirements.  相似文献   
47.
The Apollonius Tenth Problem, as defined by Apollonius of Perga circa 200 B.C., has been useful for various applications in addition to its theoretical interest. Even though particular cases have been handled previously, a general framework for the problem has never been reported. Presented in this paper is a theory to handle the Apollonius Tenth Problem by characterizing the spatial relationship among given circles and the desired Apollonius circles. Hence, the given three circles in this paper do not make any assumption regarding on the sizes of circles and the intersection/inclusion relationship among them. The observations made provide an easy-to-code algorithm to compute any desired Apollonius circle which is computationally efficient and robust.  相似文献   
48.
Years have lapsed since the inauguration of the first Wireless Application Protocol (WAP) application. One of the main reasons for the lukewarm response so far may be attributed to the lack of a “Killer” application. Many companies and developers have attempted to replicate email services (an Internet Killer appplication) within the WAP realm, but till now, no significant success has been reported. This paper will first discuss on the key functions which are lacking in the present WAP-email service, and which are arguably necessary if a much larger user base is to be attracted to these services. A new system will be proposed which can enable the user to send files residing in a remote personal computer (PC) as attachments to his emails using WAP-enabled mobile devices. The implementation of the system will be presented in details. Issue relating to the connection to various types of email servers and the security of the system will also be addressed in the paper.  相似文献   
49.
美国西雅图先锋广场历史保护区的形成   总被引:1,自引:0,他引:1  
黄治 《规划师》2004,20(4):91-93
考察美国西雅图先锋广场历史保护区形成的过程,可以看出城市历史文化遗存的保护是经济与历史文化合力作用的结果,公众参与在城市历史文化保护工作中发挥着重要的作用。我国城市经济高速发展,保护与发展的矛盾冲突还没得到很好解决,先锋广场的例子对我们具有一定的参考价值。  相似文献   
50.
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