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   9416篇
  免费   717篇
  国内免费   763篇
电工技术   311篇
综合类   1820篇
化学工业   96篇
金属工艺   99篇
机械仪表   403篇
建筑科学   284篇
矿业工程   71篇
能源动力   26篇
轻工业   94篇
水利工程   53篇
石油天然气   50篇
武器工业   44篇
无线电   736篇
一般工业技术   277篇
冶金工业   565篇
原子能技术   19篇
自动化技术   5948篇
  2024年   31篇
  2023年   113篇
  2022年   230篇
  2021年   258篇
  2020年   193篇
  2019年   130篇
  2018年   110篇
  2017年   147篇
  2016年   167篇
  2015年   196篇
  2014年   455篇
  2013年   379篇
  2012年   526篇
  2011年   588篇
  2010年   524篇
  2009年   558篇
  2008年   658篇
  2007年   703篇
  2006年   682篇
  2005年   670篇
  2004年   530篇
  2003年   514篇
  2002年   350篇
  2001年   344篇
  2000年   268篇
  1999年   205篇
  1998年   167篇
  1997年   161篇
  1996年   125篇
  1995年   138篇
  1994年   127篇
  1993年   98篇
  1992年   78篇
  1991年   68篇
  1990年   41篇
  1989年   44篇
  1988年   34篇
  1987年   24篇
  1986年   22篇
  1985年   33篇
  1984年   31篇
  1983年   18篇
  1982年   10篇
  1981年   14篇
  1980年   12篇
  1979年   10篇
  1978年   11篇
  1977年   10篇
  1975年   15篇
  1971年   7篇
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
991.
992.
Reviews the book, Handbook of functional neuroimaging of cognition by Roberto Cabeza and Alan Kingstone. In fairness to the contributors of this excellent volume, much of the contents deals with sober reflection on the difficulties and uncertainties of interpreting the neuroimaging data in a variety of domains such as attention, vision, semantic and episodic memory, language, and working memory. In general, the authors of this volume present a fair, sophisticated, and valuable overview of the progress (or lack thereof) that functional imaging has contributed in a variety of different domains. This book provides a sense of a field that is undergoing rapid development and that clearly will have much to offer in the future. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
993.
To facilitate queries over semi-structured data, various structural summaries have been proposed. Structural summaries are derived directly from data and serve as the indexes for evaluating path expressions. We introduce D(k)-index, an adaptive structural summary, for general graph-structured data. Building on previous 1-index and A(k)-index, D(k)-index is also based on the concept of bisimilarity. However, as a generalization of 1-index and A(k)-index, D(k)-index possesses the adaptive ability to adjust its structure to changes in query load. It also enables efficient update algorithms, which are crucial to real applications but have not been adequately addressed in previous literatures. Our experiments show that D(k)-index is a more effective structural summary than previous static ones as a result of its query load sensitivity. In addition, the update operations on it can be performed more efficient than on its predecessors.  相似文献   
994.
995.
A language for manipulating ASN.1 print files is defined as an addition to the ASN.1 data definition language as specified in the ISO standards 8824 and 8825. The language has syntax similar in spirit to SQL, and provides analogous operations. Together, ASN.1 and the manipulation language define a model that can represent attribute hierarchies, multivalued attributes, optional attributes, both ordered and unordered attributes and tuples, and unnamed attributes—constructs that are absent in the traditional relational model. In addition, the proposed model allows the semantics of order, homogeneity, optionality, choosability, and uniqueness to be attached to constructs and construct elements. The approach is well suited for modeling data where form is important, such as text and flat file databases having ad hoc formats. It also supports modeling relations. The primary motivation for developing this language is to provide a common model for a database integration approach where some of the databases are in the form of formatted flat file text, while others are relational. Although the approach is general and can be applied in many different areas, scientific database and tool integration was the primary motive for its development.  相似文献   
996.
This paper proposes a metalanguage for representing communication among participants in a session of a group decision support system (GDSS). Such a vehicle can be used for setting standards and designing specific user interfaces with GDSS.Three different roles of participants are identified: chairperson, chauffeur and regular participant. The tasks and activities of each role are analyzed. Based on the analysis, communications requirements are derived. The requirements lead to a design of a metalanguage consisting of 15 different commands. The paper concludes by displaying the structure and syntax of each command.The work described here is conceptual and could be considered as a proposal for GDSS language design.  相似文献   
997.
《视听说》课是现代外语教学发展的需要,是科学技术发展和电教事业发展的产物.  相似文献   
998.
浅谈维吾尔语对偶词   总被引:1,自引:0,他引:1  
分析了维吾尔语对偶词的语音、语义、语用特点,阐述了对偶词的产生、发展过程,并着重就对偶词的结构做了分析。  相似文献   
999.
In this paper, we present a formalism called feature grammar and its application to several problems of semantic analysis. Our extension concerns the structure of the feature value sets, which can be complex, and the definition of unification, which is dependent on this structure. Moreover, we introduce generation rules for feature symbols in order to determine well-formed symbols, which form the alphabet of a formal language for natural language analysis.  相似文献   
1000.
We prove that there exists no algorithm to decide whether the language generated by a context-free grammar is dense with respect to the lexicographic ordering. As a corollary to this result, we show that it is undecidable whether the lexicographic orderings of the languages generated by two context-free grammars have the same order type.  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