全文获取类型
收费全文 | 216746篇 |
免费 | 12063篇 |
国内免费 | 6244篇 |
专业分类
电工技术 | 8160篇 |
技术理论 | 12篇 |
综合类 | 10757篇 |
化学工业 | 33494篇 |
金属工艺 | 11823篇 |
机械仪表 | 11144篇 |
建筑科学 | 12689篇 |
矿业工程 | 4270篇 |
能源动力 | 4919篇 |
轻工业 | 12466篇 |
水利工程 | 3628篇 |
石油天然气 | 7527篇 |
武器工业 | 951篇 |
无线电 | 25984篇 |
一般工业技术 | 32721篇 |
冶金工业 | 9205篇 |
原子能技术 | 1858篇 |
自动化技术 | 43445篇 |
出版年
2024年 | 464篇 |
2023年 | 2005篇 |
2022年 | 3366篇 |
2021年 | 4972篇 |
2020年 | 3822篇 |
2019年 | 3221篇 |
2018年 | 17565篇 |
2017年 | 17022篇 |
2016年 | 13276篇 |
2015年 | 5482篇 |
2014年 | 6408篇 |
2013年 | 8152篇 |
2012年 | 11497篇 |
2011年 | 18197篇 |
2010年 | 16094篇 |
2009年 | 13290篇 |
2008年 | 14409篇 |
2007年 | 15009篇 |
2006年 | 7676篇 |
2005年 | 7799篇 |
2004年 | 5750篇 |
2003年 | 5277篇 |
2002年 | 4414篇 |
2001年 | 3789篇 |
2000年 | 3589篇 |
1999年 | 3794篇 |
1998年 | 3185篇 |
1997年 | 2763篇 |
1996年 | 2486篇 |
1995年 | 2055篇 |
1994年 | 1636篇 |
1993年 | 1286篇 |
1992年 | 1043篇 |
1991年 | 800篇 |
1990年 | 622篇 |
1989年 | 534篇 |
1988年 | 404篇 |
1987年 | 304篇 |
1986年 | 206篇 |
1985年 | 175篇 |
1984年 | 103篇 |
1983年 | 86篇 |
1982年 | 90篇 |
1981年 | 60篇 |
1980年 | 49篇 |
1968年 | 49篇 |
1966年 | 48篇 |
1965年 | 50篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
102.
103.
CFD Modeling of Active Volume Creation in a Non‐Newtonian Fluid Agitated by Submerged Recirculating Jets 下载免费PDF全文
Computational fluid dynamics (CFD) models were employed to investigate flow conditions inside a model reactor in which yield stress non‐Newtonian liquid is mobilized using submerged recirculating jets. The simulation results agree well with the experimental results of active volume in the reactor obtained using flow visualization by the authors in a previous study. The models developed are capable of predicting a critical jet velocity (vc) that determines the extent of active volume obtained due to jet mixing. The vc values are influenced both by the rheological properties of the liquid and the nozzle orientation. The liquid with higher effective viscosity leads to higher vc for a downward facing injection nozzle. However, an upward facing injection nozzle along with a downward facing suction nozzle generates enhanced complementary flow fields which overcome the rheological constraints of the liquid and lead to lower vc. 相似文献
104.
105.
106.
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
107.
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
108.
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
109.
110.
Yao Dajie Liu Xiaofei Wu Jian 《International Journal of Control, Automation and Systems》2020,18(9):2251-2258
International Journal of Control, Automation and Systems - In this paper, the tracking problem for a class of uncertain nonlinearly parameterized systems with input delay based the adaptive... 相似文献