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   115231篇
  免费   1969篇
  国内免费   471篇
电工技术   1124篇
综合类   2345篇
化学工业   17893篇
金属工艺   5489篇
机械仪表   3623篇
建筑科学   3960篇
矿业工程   805篇
能源动力   2108篇
轻工业   6290篇
水利工程   1585篇
石油天然气   548篇
武器工业   2篇
无线电   11280篇
一般工业技术   21239篇
冶金工业   9181篇
原子能技术   568篇
自动化技术   29631篇
  2021年   384篇
  2020年   334篇
  2019年   403篇
  2018年   14828篇
  2017年   13750篇
  2016年   10396篇
  2015年   1058篇
  2014年   950篇
  2013年   2307篇
  2012年   4313篇
  2011年   10855篇
  2010年   9305篇
  2009年   6680篇
  2008年   8106篇
  2007年   9082篇
  2006年   1361篇
  2005年   2361篇
  2004年   2153篇
  2003年   2167篇
  2002年   1555篇
  2001年   729篇
  2000年   789篇
  1999年   629篇
  1998年   649篇
  1997年   527篇
  1996年   648篇
  1995年   556篇
  1994年   546篇
  1993年   545篇
  1992年   498篇
  1991年   345篇
  1990年   438篇
  1989年   423篇
  1988年   386篇
  1987年   426篇
  1986年   384篇
  1985年   515篇
  1984年   491篇
  1983年   443篇
  1982年   464篇
  1981年   445篇
  1980年   353篇
  1979年   365篇
  1978年   329篇
  1977年   307篇
  1976年   268篇
  1975年   318篇
  1974年   243篇
  1973年   279篇
  1972年   154篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
In this paper, we consider the classical finite mixture model, which is an effective tool for modeling lifetime distributions for random samples from heterogeneous populations. We discuss new results on stochastic comparison for two finite mixtures when each of them is drawn from one of the following semiparametric families, i.e., proportional hazards, accelerated lifetime and proportional reversed hazards.  相似文献   
22.
23.
24.
Variations of Incomplete Open Cubes is the major project by the twentieth-century conceptual artist Sol LeWitt. In this paper we interpret the enumerative component of the project as embeddings of graphs. This formulation permits use of an algorithm to check the completeness of the list of the structures produced by the artist. Our conclusion is that the artist found the correct number of structures (that is, 122), but that his list contains a mistake in the presentation of a pair of incomplete cubes, a discovery that appears not to have been noted before.  相似文献   
25.
26.
27.
28.
Understanding semantic word shifts in scientific domains is essential for facilitating interdisciplinary communication. Using a data set of published papers in the field of information retrieval (IR), this paper studies the semantic shifts of words in IR based on mining per-word topic distribution over time. We propose that semantic word shifts not only occur over time, but also over topics. The shifts are examined from two perspectives, the topic-level and the context-level. According to the over-time word-topic distribution, stable words and unstable words are recognized. The diverging and converging trends in the unstable type reveal characteristics of the topic evolution process. The context-level shifts are further detected by similarities between word vectors. Our work associates semantic word shifts with the evolving of topics, which facilitates a better understanding of semantic word shifts from both topics and contexts.  相似文献   
29.
Research funding has been seen as one of the most important resource in the reward system of science. And usage of publications denotes an interesting perspective of user behavior in scientific communication. This study aims to address the relationship between funding and Usage Count, which is a new metrics item established on the platform of Web of Science. Full records of 300,010 articles published in 2013 were downloaded in October 2015, and divided into six disciplines, including information science library science, education educational research, economics, computer science, materials science, and chemistry. Seven indicators were proposed to measure the impact, including Funding rate, Citation per paper, Usage rate, Usage per paper, Citation difference, Usage difference, and Conversion rate. It concluded funding has impact on usage and citation, and funded papers attract more usage, but varying in different disciplines. Usage Count can be used in the extension of citation metrics but with limits. This study originally engages with usage metrics and detected that there is positive correlation between usage and funding.  相似文献   
30.
Recent increase in the number of digital photos in the content sharing and social networking websites has created an endless demand for techniques to analyze, navigate, and summarize these images. In this paper, we focus on image collection summarization. Earlier methods in image collection summarization consider representativeness and diversity criteria while recent ones also consider other criteria such as image quality, aesthetic or appeal. In this paper, we propose a multi-criteria context-sensitive approach for social image collection summarization. In the proposed method, two different sets of features are combined while each one looks at different criteria for image collection summarization: social attractiveness features and semantic features. The first feature set considers different aspects that make an image appealing such as image quality, aesthetic, and emotion to create attractiveness score for input images while the second one covers semantic content of images and assigns semantic score to them. We use social network infrastructure to identify attractiveness features and domain ontology for extracting ontology features. The final summarization is provided by integrating the attractiveness and semantic features of input images. The experimental results on a collection of human generated summaries on a set of Flickr images demonstrate the effectiveness of the proposed image collection summarization approach.  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