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   287793篇
  免费   3269篇
  国内免费   967篇
电工技术   4263篇
综合类   2454篇
化学工业   42864篇
金属工艺   14941篇
机械仪表   9980篇
建筑科学   6124篇
矿业工程   2715篇
能源动力   5712篇
轻工业   16374篇
水利工程   4154篇
石油天然气   8056篇
武器工业   22篇
无线电   30564篇
一般工业技术   60859篇
冶金工业   36910篇
原子能技术   6867篇
自动化技术   39170篇
  2021年   2050篇
  2019年   2001篇
  2018年   17867篇
  2017年   16829篇
  2016年   13791篇
  2015年   2817篇
  2014年   3990篇
  2013年   8913篇
  2012年   8738篇
  2011年   16402篇
  2010年   13958篇
  2009年   11909篇
  2008年   13241篇
  2007年   14088篇
  2006年   5675篇
  2005年   6276篇
  2004年   5712篇
  2003年   5683篇
  2002年   4888篇
  2001年   4561篇
  2000年   4353篇
  1999年   4249篇
  1998年   10234篇
  1997年   7209篇
  1996年   5539篇
  1995年   4139篇
  1994年   3607篇
  1993年   3846篇
  1992年   2994篇
  1991年   3017篇
  1990年   2890篇
  1989年   2853篇
  1988年   2874篇
  1987年   2509篇
  1986年   2569篇
  1985年   2854篇
  1984年   2687篇
  1983年   2554篇
  1982年   2300篇
  1981年   2270篇
  1980年   2346篇
  1979年   2360篇
  1978年   2382篇
  1977年   2489篇
  1976年   2876篇
  1975年   2190篇
  1974年   2068篇
  1973年   2166篇
  1972年   1943篇
  1971年   1755篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
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   
45.
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   
46.
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   
47.
The microstructure and properties of the functional coatings formed by impact friction processing of product surfaces with a flexible tool are studied. It is established that the processing produces a hard nanostructured surface layer with fragments up to 0.13 µm in size, as it is achieved by severe plastic deformation.  相似文献   
48.
Based on the phase transformation theories, especially the T0 concept of bainite transformation, alloy optimisation of bainitic steel with carbides has been carried out aiming at the produce of plastic mould with large cross-section. The effect of manganese and silicon on proeutectoid ferrite and bainite transformation is explored by dilatometric analysis, XRD and different microscopy techniques. The results show that after the alloy optimisation, the transformation of proeutectoid ferrite is suppressed and when the cooling rate is lower than 0·1°C?s??1, the new lower bainite transformation appears by decreasing carbon capacity of austenite and promoting carbide precipitation. Industrial production proves that the optimised alloy SDP1 can meet the demand for the plastic mould with the thickness of 1050?mm.  相似文献   
49.
Protection of Metals and Physical Chemistry of Surfaces - The possibility is shown of creating a chart of local corrosion damage in the walls of heat-exchange tubes on the basis of the data of...  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