全文获取类型
收费全文 | 332424篇 |
免费 | 3473篇 |
国内免费 | 977篇 |
专业分类
电工技术 | 5400篇 |
综合类 | 2470篇 |
化学工业 | 47845篇 |
金属工艺 | 19390篇 |
机械仪表 | 14069篇 |
建筑科学 | 6833篇 |
矿业工程 | 3268篇 |
能源动力 | 6162篇 |
轻工业 | 16651篇 |
水利工程 | 4672篇 |
石油天然气 | 8969篇 |
武器工业 | 22篇 |
无线电 | 34454篇 |
一般工业技术 | 73225篇 |
冶金工业 | 40752篇 |
原子能技术 | 7636篇 |
自动化技术 | 45056篇 |
出版年
2021年 | 2097篇 |
2019年 | 2036篇 |
2018年 | 22195篇 |
2017年 | 21727篇 |
2016年 | 16048篇 |
2015年 | 3178篇 |
2014年 | 4104篇 |
2013年 | 9062篇 |
2012年 | 10193篇 |
2011年 | 21353篇 |
2010年 | 18758篇 |
2009年 | 16364篇 |
2008年 | 17287篇 |
2007年 | 19458篇 |
2006年 | 5785篇 |
2005年 | 8914篇 |
2004年 | 7109篇 |
2003年 | 6879篇 |
2002年 | 5384篇 |
2001年 | 4630篇 |
2000年 | 4456篇 |
1999年 | 4273篇 |
1998年 | 10247篇 |
1997年 | 7228篇 |
1996年 | 5557篇 |
1995年 | 4159篇 |
1994年 | 3646篇 |
1993年 | 3890篇 |
1992年 | 3015篇 |
1991年 | 3047篇 |
1990年 | 2895篇 |
1989年 | 2864篇 |
1988年 | 2876篇 |
1987年 | 2512篇 |
1986年 | 2572篇 |
1985年 | 2857篇 |
1984年 | 2693篇 |
1983年 | 2561篇 |
1982年 | 2307篇 |
1981年 | 2277篇 |
1980年 | 2349篇 |
1979年 | 2369篇 |
1978年 | 2385篇 |
1977年 | 2491篇 |
1976年 | 2878篇 |
1975年 | 2189篇 |
1974年 | 2069篇 |
1973年 | 2166篇 |
1972年 | 1940篇 |
1971年 | 1760篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
Programming and Computer Software - Modern computer systems often include specialized processors that are programmed in domain-specific languages. The compiler-in-the-loop technology, which assumes... 相似文献
133.
134.
We show that in the presence of magnetic field, two superconducting phases with the center-of-mass momentum of Cooper pair parallel to the magnetic field are induced in Dresselhaus spin–orbit-coupled superconductor. Specifically, at small magnetic field, the center-of-mass momentum is induced due to the energy-spectrum distortion and no unpairing region with vanishing singlet correlation appears. We refer to this superconducting state as the drift-BCS state. By further increasing the magnetic field, the superconducting state falls into the Fulde–Ferrell state with the emergence of the unpairing regions. The observed abrupt enhancement of the center-of-mass momenta and suppression on the order parameters during the transition indicate the occurrence of a first-order phase transition. Enhanced Pauli limit and hence enlarged magnetic-field regime of the Fulde–Ferrell state, due to the spin-flip terms of the spin–orbit coupling, are revealed. We also address the triplet correlations induced by the spin–orbit coupling, and show that the Cooper-pair spin polarizations, generated by the magnetic field and center-of-mass momentum with the triplet correlations exhibit totally different magnetic-field dependences between the drift-BCS and Fulde–Ferrell states. 相似文献
135.
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
136.
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
137.
This study addresses the thermo‐diffusion and the diffusion‐thermo phenomena in a semi‐infinite absorbent channel whose walls are contracting/expanding, with heat source/sink effects. The governing partial differential equations with suitable boundary conditions are transformed to a system of dimensionless ordinary differential equations. An analytic solution of the problem has been found using a technique called homotopy analysis method (HAM). HAM gives consistently valid answers to the problem over an extensive variety of parameters and also provides better accuracy. To validate the analytical results, a comparison has been presented with a numerical solution calculated by using the parallel shooting method. The effects of dimensionless parameters, that is, deformation parameter, Reynolds number, Soret and Dufour numbers, and heat source/sink parameter on the expressions of velocity, temperature, and concentration profiles are analyzed graphically to understand the physics of the deformable channel. It has been noted that the velocity across the channel is higher for the expanding channel, as compared to that for the contracting channel. Also the Soret and Dufour number increases the temperature of the fluid, and decreases the concentration. The temperature profile has an increasing behavior in the case of heat source, and a decreasing behavior in the case of heat sink. 相似文献
138.
139.
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
140.
L. S. Belevskii N. V. Koptseva I. V. Belevskaya Yu. Yu. Efimova 《Russian Metallurgy (Metally)》2015,2015(9):753-758
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