全文获取类型
收费全文 | 21530篇 |
免费 | 1798篇 |
国内免费 | 923篇 |
专业分类
电工技术 | 1199篇 |
技术理论 | 2篇 |
综合类 | 1379篇 |
化学工业 | 3612篇 |
金属工艺 | 1199篇 |
机械仪表 | 1395篇 |
建筑科学 | 1941篇 |
矿业工程 | 751篇 |
能源动力 | 578篇 |
轻工业 | 1208篇 |
水利工程 | 362篇 |
石油天然气 | 1533篇 |
武器工业 | 145篇 |
无线电 | 2211篇 |
一般工业技术 | 2597篇 |
冶金工业 | 1055篇 |
原子能技术 | 232篇 |
自动化技术 | 2852篇 |
出版年
2024年 | 83篇 |
2023年 | 400篇 |
2022年 | 587篇 |
2021年 | 890篇 |
2020年 | 725篇 |
2019年 | 612篇 |
2018年 | 659篇 |
2017年 | 737篇 |
2016年 | 621篇 |
2015年 | 817篇 |
2014年 | 1120篇 |
2013年 | 1228篇 |
2012年 | 1407篇 |
2011年 | 1447篇 |
2010年 | 1327篇 |
2009年 | 1180篇 |
2008年 | 1157篇 |
2007年 | 1126篇 |
2006年 | 1193篇 |
2005年 | 1110篇 |
2004年 | 662篇 |
2003年 | 583篇 |
2002年 | 515篇 |
2001年 | 491篇 |
2000年 | 452篇 |
1999年 | 602篇 |
1998年 | 472篇 |
1997年 | 399篇 |
1996年 | 371篇 |
1995年 | 324篇 |
1994年 | 242篇 |
1993年 | 143篇 |
1992年 | 130篇 |
1991年 | 114篇 |
1990年 | 90篇 |
1989年 | 72篇 |
1988年 | 54篇 |
1987年 | 28篇 |
1986年 | 31篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
2.
Yujie Chen Yiping Song Zhen Zhang Yali Chen Qiliang Deng Shuo Wang 《Advanced functional materials》2021,31(41):2104885
Various products, including foods and pharmaceuticals, are sensitive to temperature fluctuations. Thus, temperature monitoring during production, transportation, and storage is critical. Facile indicators are required to monitor temperature conditions via color changes in real time. This study aimed to prepare and apply thiol-functionalized covalent organic frameworks (COFs) as a novel indicator for monitoring thermal history and temperature abuse. The COFs underwent obvious color changes from bright yellow to purple after exposure to different temperatures for varying durations. The reaction kinetics are analyzed under isothermal conditions, which reveal that the order of reaction rates is k−20°C < k4°C < k20°C < k35°C < k55°C. The activation energy (Ea) of the COFs is calculated using the Arrhenius equation as 50.71 kJ moL−1. The COFs are capable of sensitive color changes and offer a broad temperature tracking range, thereby demonstrating their application potential for the monitoring of temperature and time exposure history during production, transportation, and storage. This excellent performance thermal history indicator also shows promise for expanding the application field of COFs. 相似文献
3.
4.
5.
Huizhu Cai Bingbing Chen Xiao Zhang Yuchen Deng Dequan Xiao Ding Ma Chuan Shi 《Nano Research》2021,14(1):122-130
Over recent years,catalytic materials of Fe-N-C species have been recognized being active for oxygen reduction reaction(ORR).However,the identification of active site remains challenging as it generally involves a pyrolysis process and mixed components being obtained.Herein Fe3C/C and Fe2N/C samples were synthesized by temperature programmed reduction of Fe precursors in 15%CH4/H2and pure NH3,respectively.By acid leaching of Fe2N/C sample,only single sites of FeN4species were presented,providing an ideal model for identification of catalytic functions of the single sites of FeN4in ORR.A correlation was conducted between the concentration of FeⅡN4in low spin state by Mossbauer spectra and the kinetic current density at 0.8 V in alkaline media,and such a structure-performance correlation assures the catalytic roles of low spin FeⅡN4 species as highly active sites for the ORR. 相似文献
6.
7.
Weikang Dong Ruishi Qi Tiansheng Liu Yi Li Ning Li Ze Hua Zirui Gao Shuyuan Zhang Kaihui Liu Jiandong Guo Peng Gao 《Advanced materials (Deerfield Beach, Fla.)》2020,32(46):2002014
Hyperbolic phonon polaritons (HPhPs) in orthorhombic-phase molybdenum trioxide (α-MoO3) show in-plane hyperbolicity, great wavelength compression, and ultralong lifetime, therefore holding great potential in nanophotonic applications. However, its polaritonic response in the far-infrared (FIR) range remains unexplored due to challenges in experimental characterization. Here, monochromated electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) is used to probe HPhPs in α-MoO3 in both mid-infrared (MIR) and FIR frequencies and correlate their behaviors with microstructures and orientations. It is found that low structural symmetry leads to various phonon modes and multiple Reststrahlen bands (RBs) over a broad spectral range (over 70 meV) and in different directions (55–63 meV and 119–125 meV along the b-axis, 68–106 meV along the c-axis, and 101–121 meV along the a-axis). These HPhPs can be selectively excited by controlling the direction of swift electrons. These findings provide new opportunities in nanophotonic and optoelectronic applications, such as directed light propagation, hyperlenses, and heat transfer. 相似文献
8.
9.
Shuyi Fu Wenrui Feng Ying Jia Tielong Deng Wenzhong Wang Guling Zhang Junli Fu 《International Journal of Hydrogen Energy》2021,46(21):11544-11555
ZnO/Cu2S nanotube arrays are fabricated firstly by a facile and capping-agent-free method, and the photo-electrochemical performance has been studied systematically. The results show that ZnO/Cu2S nanotube arrays achieve enhanced photo-electrochemical water splitting performance and the photocurrent densities of ZnO/Cu2S are 7.9 times than that of ZnO at 0 V versus Ag/AgCl. The performance of the ZnO/Cu2S nanotube arrays can be adjusted by changing the amount of Cu2S microcrystals. The results confirm that the enhanced photo-electrochemical performance of ZnO/Cu2S is due to the significantly improved visible light absorption, effective separation of photo-induced carriers due to the well band energy match and the formed p-n junction between ZnO and Cu2S. 相似文献
10.