全文获取类型
收费全文 | 20682篇 |
免费 | 2076篇 |
国内免费 | 1257篇 |
专业分类
电工技术 | 1434篇 |
技术理论 | 3篇 |
综合类 | 1408篇 |
化学工业 | 3204篇 |
金属工艺 | 1282篇 |
机械仪表 | 1267篇 |
建筑科学 | 1856篇 |
矿业工程 | 637篇 |
能源动力 | 674篇 |
轻工业 | 1372篇 |
水利工程 | 392篇 |
石油天然气 | 1221篇 |
武器工业 | 174篇 |
无线电 | 2333篇 |
一般工业技术 | 2205篇 |
冶金工业 | 1027篇 |
原子能技术 | 375篇 |
自动化技术 | 3151篇 |
出版年
2024年 | 118篇 |
2023年 | 404篇 |
2022年 | 710篇 |
2021年 | 995篇 |
2020年 | 769篇 |
2019年 | 560篇 |
2018年 | 646篇 |
2017年 | 729篇 |
2016年 | 619篇 |
2015年 | 874篇 |
2014年 | 1156篇 |
2013年 | 1218篇 |
2012年 | 1303篇 |
2011年 | 1486篇 |
2010年 | 1270篇 |
2009年 | 1236篇 |
2008年 | 1152篇 |
2007年 | 1207篇 |
2006年 | 1165篇 |
2005年 | 1023篇 |
2004年 | 720篇 |
2003年 | 579篇 |
2002年 | 600篇 |
2001年 | 515篇 |
2000年 | 532篇 |
1999年 | 534篇 |
1998年 | 360篇 |
1997年 | 316篇 |
1996年 | 281篇 |
1995年 | 227篇 |
1994年 | 173篇 |
1993年 | 118篇 |
1992年 | 107篇 |
1991年 | 87篇 |
1990年 | 51篇 |
1989年 | 49篇 |
1988年 | 34篇 |
1987年 | 19篇 |
1986年 | 17篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1959年 | 5篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
1.
Electronic Commerce Research - We consider a platform providing free content for users and earning profit from the sale of advertising. The platform can collect and analyze personal data to... 相似文献
2.
Mitigating gibbsite particle cracking and breakage during industrial alumina production can increase the quality of smelter grade alumina product by reducing the ultrafine particle content. Therefore, it is essential to investigate the particle cracking during static calcination and the breakage of calcined gibbsite particles under external force. In this work, we investigated the impact of the calcination ramping rate and the crystallite size on gibbsite particle cracking during static calcination. A slow ramping rate and a large pristine crystallite size tend to increase particle cracking. Apart from the study of particle cracking behaviour, we also investigated the breakage of calcined gibbsite particle under external force. Cracks on the particle surface can initiate breakage within the crystallite and along the grain boundary under external force. The breakage within crystallite occurs as the cleavage of the crystallite, while the breakage along the grain boundary leads to the shedding of a whole crystallite. We further explored the factors influencing the strength of calcined gibbsite particles. With increasing calcination temperature, the strength of particle increases when gibbsite converts to boehmite, and then decreases when boehmite converts into amorphous alumina. Particles containing smaller crystallites and calcined with fast ramping rates exhibit higher resistance to breakage. 相似文献
3.
Bin Feng Xin Jiang Guisheng Zou Wengan Wang Tianming Sun Heng Yang Guanlei Zhao Mingye Dong Yu Xiao Hongwei Zhu Lei Liu 《Advanced functional materials》2021,31(29):2102359
The realization of liquid metal-based wearable systems will be a milestone toward high-performance, integrated electronic skin. However, despite the revolutionary progress achieved in many other components of electronic skin, liquid metal-based flexible sensors still suffer from poor sensitivity due to the insufficient resistance change of liquid metal to deformation. Herein, a nacre-inspired architecture composed of a biphasic pattern (liquid metal with Cr/Cu underlayer) as “bricks” and strain-sensitive Ag film as “mortar” is developed, which breaks the long-standing sensitivity bottleneck of liquid metal-based electronic skin. With 2 orders of magnitude of sensitivity amplification while maintaining wide (>85%) working range, for the first time, liquid metal-based strain sensors rival the state-of-art counterparts. This liquid metal composite features spatially regulated cracking behavior. On the one hand, hard Cr cells locally modulate the strain distribution, which avoids premature cut-through cracks and prolongs the defect propagation in the adjacent Ag film. On the other hand, the separated liquid metal cells prevent unfavorable continuous liquid-metal paths and create crack-free regions during strain. Demonstrated in diverse scenarios, the proposed design concept may spark more applications of ultrasensitive liquid metal-based electronic skins, and reveals a pathway for sensor development via crack engineering. 相似文献
4.
5.
结合广珠西高速路面超薄磨耗层的具体应用,论述了超薄磨耗层对原材料技术要求、配合比设计、施工工艺和施工关键技术控制等。 相似文献
6.
Zhongyu Qiu Xiaowen Ge Naibao Huang Shixian Zhou Junjie Zhang Jiaping Xuan 《International Journal of Hydrogen Energy》2021,46(3):2952-2959
Polyethylene oxide (PEO)-polypropylene oxide (PPO)-polyethylene oxide block copolymer having different molecular weights are used as precursors of carbon materials to prepare Hollow -Derivatives carbon material as an electrocatalyst through block copolymer self-assembly. The composition and microstructure of the prepared catalysts are shown by Raman spectroscopy, X-ray diffraction (XRD), Test of nitrogen adsorption and desorption curves, High resolution transmission electron microscopy (HR-TEM) and scanning electron microscopy (HR-SEM). Oxygen was passed into alkaline electrolyte solution until the solution reached saturation state. With molecular weight increasing, the obtained sample gradually changed from block to hollow and spherical. When the molecular weight was 12600 g mol?1, the evenly hollow carbon nanocages was acquired (C-12600). In O2 saturated alkaline electrolyte (0.1 M KOH solution), C-12600's limited current density,half-wave potential and initial potential are 5.23 mA cm?2@0.4 V, 0.72 V and 0.81 V, respectively. And most important is that half-wave potential and onset potential have barely change after 2000 cycles of cyclic voltammetry. As a result, the porous carbon materials exhibited excellent electrocatalytic activity while maintaining high stability in alkaline KOH solution. 相似文献
7.
8.
9.
10.
Wu Ge Mu Yi Susilo Willy Guo Fuchun Zhang Futai 《International Journal of Information Security》2019,18(3):321-331
International Journal of Information Security - Data integrity is a critical security issue in cloud storage. The data integrity checking schemes by a third-party auditor (TPA) have attracted a lot... 相似文献