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   119948篇
  免费   9712篇
  国内免费   4341篇
电工技术   6302篇
技术理论   5篇
综合类   5088篇
化学工业   19415篇
金属工艺   5924篇
机械仪表   7822篇
建筑科学   6111篇
矿业工程   2044篇
能源动力   4189篇
轻工业   8960篇
水利工程   2093篇
石油天然气   3308篇
武器工业   838篇
无线电   17896篇
一般工业技术   17396篇
冶金工业   8247篇
原子能技术   1528篇
自动化技术   16835篇
  2024年   373篇
  2023年   1542篇
  2022年   2894篇
  2021年   4276篇
  2020年   3158篇
  2019年   2679篇
  2018年   3328篇
  2017年   3571篇
  2016年   3687篇
  2015年   4326篇
  2014年   5767篇
  2013年   7838篇
  2012年   8278篇
  2011年   9453篇
  2010年   7938篇
  2009年   7759篇
  2008年   7701篇
  2007年   6954篇
  2006年   6154篇
  2005年   5088篇
  2004年   4054篇
  2003年   3284篇
  2002年   3076篇
  2001年   2529篇
  2000年   2230篇
  1999年   1970篇
  1998年   2671篇
  1997年   1800篇
  1996年   1530篇
  1995年   1238篇
  1994年   943篇
  1993年   820篇
  1992年   601篇
  1991年   564篇
  1990年   475篇
  1989年   452篇
  1988年   355篇
  1987年   300篇
  1986年   270篇
  1985年   245篇
  1984年   208篇
  1983年   160篇
  1982年   159篇
  1981年   141篇
  1980年   145篇
  1979年   116篇
  1978年   95篇
  1977年   126篇
  1976年   158篇
  1975年   80篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
A device able to electrokinetically concentrate cationic samples has many potential medical and industrial applications, but until now has remained undeveloped due to the lack of a commercial anion-permselective material leading to a prohibitively complex fabrication procedure. Herein, a novel multiscale-porous anion exchange membrane (MP-AEM) that enables the convenient and scalable electrokinetic concentration of cationic species is proposed. A mechanically enhanced multiscale-porous structure with a solid framework is realized by adopting polyester resin as an additive to overcome the intrinsic limitations of the AEM material. The scalable MP-AEM-embedded electrokinetic concentrator is devised based on the peculiar properties of the MP-AEM that for allow both ion and fluid transport. With the MP-AEM, the concentrator is fabricated in a highly streamlined manner consisting only of a simple insertion and assembly. The concentration performance of the MP-AEM-embedded electrokinetic concentrator is demonstrated with a positively charged fluorescent dye and a fluorescein-labeled protein, and the results show enrichment factors of 250 and 500, respectively. The MP-AEM makes cationic electrokinetic concentration more accessible and scalable, thereby enabling further progress in a wide range of fields.  相似文献   
93.
This paper examines what influences trust in mobile social commerce environment. Drawing on trust-based acceptance model (i.e. cognitive and emotional trust) and online review features (i.e. profile photo, linguistic style, and reported experience), we examine how these factors affect trust in mobile social commerce. Hypotheses were tested using survey data. The results of our model showed that there are significant influences of profile photo, reported experience, cognitive, and emotional trust towards trust in ms-commerce. This work contributes to existing literature by examining the roles of previous trust in mobile payments and online reviews on trust in mobile social commerce.  相似文献   
94.
Machine Intelligence Research - This paper proposes an image encryption algorithm LQBPNN (logistic quantum and back propagation neural network) based on chaotic sequences incorporating quantum...  相似文献   
95.
The electrochemical reduction of carbon dioxide (CO2) to hydrocarbons is a challenging task because of the issues in controlling the efficiency and selectivity of the products. Among the various transition metals, copper has attracted attention as it yields more reduced and C2 products even while using mononuclear copper center as catalysts. In addition, it is found that reversible formation of copper nanoparticle acts as the real catalytically active site for the conversion of CO2 to reduced products. Here, it is demonstrated that the dinuclear molecular copper complex immobilized over graphitized mesoporous carbon can act as catalysts for the conversion of CO2 to hydrocarbons (methane and ethylene) up to 60%. Interestingly, high selectivity toward C2 product (40% faradaic efficiency) is achieved by a molecular complex based hybrid material from CO2 in 0.1 m KCl. In addition, the role of local pH, porous structure, and carbon support in limiting the mass transport to achieve the highly reduced products is demonstrated. Although the spectroscopic analysis of the catalysts exhibits molecular nature of the complex after 2 h bulk electrolysis, morphological study reveals that the newly generated copper cluster is the real active site during the catalytic reactions.  相似文献   
96.
97.
The microstructure and mechanical properties of Mg–6Zn–1Y and Mg–6Zn–3Y(wt%) alloys under different cooling rates were investigated. The results show that the second dendrite arm spacing(SDAS) of Mg–6Zn–1Y and Mg–6Zn–3Y is reduced by 32 and 30% with increasing cooling rates(Rc) from 10.2 to 23 K/s, which can be predicted using a empirical model of SDAS=68 R 0:45:45cand SDAS=73 R 0c, respectively. The compressive strength of both alloys increases with increasing the cooling rate, which is attributed to the increase of volume fraction(Vf) of secondary phases under high cooling rate. The interaction of the cooling rate and component with SDAS has been theoretically analyzed using interdependence theory.  相似文献   
98.
Minds and Machines - To address the rising concern that algorithmic decision-making may reinforce discriminatory biases, researchers have proposed many notions of fairness and corresponding...  相似文献   
99.
100.
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