全文获取类型
收费全文 | 636039篇 |
免费 | 8982篇 |
国内免费 | 2032篇 |
专业分类
电工技术 | 11634篇 |
综合类 | 487篇 |
化学工业 | 97685篇 |
金属工艺 | 25444篇 |
机械仪表 | 20039篇 |
建筑科学 | 14282篇 |
矿业工程 | 3618篇 |
能源动力 | 17765篇 |
轻工业 | 50216篇 |
水利工程 | 6775篇 |
石油天然气 | 12913篇 |
武器工业 | 28篇 |
无线电 | 74182篇 |
一般工业技术 | 127840篇 |
冶金工业 | 116793篇 |
原子能技术 | 14310篇 |
自动化技术 | 53042篇 |
出版年
2021年 | 6324篇 |
2020年 | 4917篇 |
2019年 | 6003篇 |
2018年 | 9952篇 |
2017年 | 9663篇 |
2016年 | 10363篇 |
2015年 | 6576篇 |
2014年 | 10751篇 |
2013年 | 30204篇 |
2012年 | 16853篇 |
2011年 | 22764篇 |
2010年 | 18238篇 |
2009年 | 20625篇 |
2008年 | 21030篇 |
2007年 | 20633篇 |
2006年 | 18326篇 |
2005年 | 16659篇 |
2004年 | 15646篇 |
2003年 | 15470篇 |
2002年 | 14861篇 |
2001年 | 14654篇 |
2000年 | 13827篇 |
1999年 | 14271篇 |
1998年 | 35922篇 |
1997年 | 25470篇 |
1996年 | 19645篇 |
1995年 | 14745篇 |
1994年 | 13105篇 |
1993年 | 12997篇 |
1992年 | 9570篇 |
1991年 | 9148篇 |
1990年 | 9033篇 |
1989年 | 8753篇 |
1988年 | 8476篇 |
1987年 | 7266篇 |
1986年 | 7223篇 |
1985年 | 8190篇 |
1984年 | 7624篇 |
1983年 | 6951篇 |
1982年 | 6491篇 |
1981年 | 6608篇 |
1980年 | 6208篇 |
1979年 | 6048篇 |
1978年 | 6169篇 |
1977年 | 7034篇 |
1976年 | 9073篇 |
1975年 | 5405篇 |
1974年 | 5076篇 |
1973年 | 5208篇 |
1972年 | 4430篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
105.
106.
Kalli Sai Bhavani Tummala Anusha Pradeep Kumar Brahman 《International Journal of Hydrogen Energy》2021,46(13):9199-9214
In the present study, we report an eco-friendly and simple route to design and synthesize novel nanocomposite catalyst based on platinum nanoparticles anchored on binary support of graphitic carbon nitride (g-C3N4) and cobalt-metal-organic framework (ZIF-67). For this purpose, ZIF-67 was prepared by precipitation method and g-C3N4 was prepared through thermal polymerization method. Later, ZIF-67 and g-C3N4 were hybridized through sonication to get homogeneous g–C3N4–ZIF-67 nanocomposite support material. Platinum nanoparticles (PtNPs) were uniformly deposited on g–C3N4–ZIF-67 by an electrochemical method. The as-developed nanocatalyst was characterized by morphological, structural and electrochemical techniques. The electrocatalytic activity of PtNPs@g–C3N4–ZIF-67 nanocatalyst towards butanol oxidation was evaluated via CV, CA, LSV and EIS in an alkaline medium. Results revealed that the proposed catalyst showed greatly enhanced electrooxidation of butanol in terms of high magnificent current density, lower oxidation potential, excellent long-term stability, large surface area, low charge transfer resistance and less toxic ability. Enhanced catalytic performance of the proposed catalyst could be ascribed to the synergistic effect of g–C3N4–ZIF-67 nanocomposite and PtNPs. The PtNPs@g–C3N4–ZIF-67 catalyst holds promising potential applications to be used as an anodic electrocatalyst for the development of high-performance alkaline fuel cells. 相似文献
107.
108.
Strength of Materials - The use of a damping system is one of the seismic protection systems that improve the seismic response of structures. The proposed methodology estimates the location (which... 相似文献
109.
Loboda P. I. Minitsky A. V. Byba Ye. G. Sysoev M. O. Radchuk S. V. 《Powder Metallurgy and Metal Ceramics》2020,58(11-12):651-656
Powder Metallurgy and Metal Ceramics - The infiltration of aluminum melts into porous metal skeletons produced by powder metallurgy methods, including 3D printing, under a pressure gradient was... 相似文献
110.
As a solid state joining process, ultrasonic spot welding has been proven to be a promising technique for joining copper alloys. However, challenges still remain in employing ultrasonic spot welding to join copper alloys. This article comprehensively reviews the current state of ultrasonic spot welding of copper alloys with a number of critical issues including materials flow, plastic deformation, temperature distribution, vibration, relative motion, vertical displacement, interface friction coefficient, online monitoring technique, coupled with the macrostructure and microstructure, the mechanical properties and electrical conductivity. In addition, the future trends in this field are provided. 相似文献