全文获取类型
收费全文 | 568535篇 |
免费 | 6660篇 |
国内免费 | 2023篇 |
专业分类
电工技术 | 10123篇 |
综合类 | 739篇 |
化学工业 | 84781篇 |
金属工艺 | 25948篇 |
机械仪表 | 19397篇 |
建筑科学 | 13333篇 |
矿业工程 | 3649篇 |
能源动力 | 13095篇 |
轻工业 | 44742篇 |
水利工程 | 6457篇 |
石油天然气 | 12385篇 |
武器工业 | 56篇 |
无线电 | 63678篇 |
一般工业技术 | 116621篇 |
冶金工业 | 97396篇 |
原子能技术 | 13718篇 |
自动化技术 | 51100篇 |
出版年
2021年 | 3875篇 |
2019年 | 3666篇 |
2018年 | 13042篇 |
2017年 | 13444篇 |
2016年 | 10708篇 |
2015年 | 4942篇 |
2014年 | 7798篇 |
2013年 | 21976篇 |
2012年 | 14528篇 |
2011年 | 23583篇 |
2010年 | 19856篇 |
2009年 | 20890篇 |
2008年 | 21284篇 |
2007年 | 22700篇 |
2006年 | 14201篇 |
2005年 | 15867篇 |
2004年 | 14214篇 |
2003年 | 13525篇 |
2002年 | 12684篇 |
2001年 | 12099篇 |
2000年 | 11570篇 |
1999年 | 11789篇 |
1998年 | 28134篇 |
1997年 | 20511篇 |
1996年 | 15900篇 |
1995年 | 12153篇 |
1994年 | 10844篇 |
1993年 | 10736篇 |
1992年 | 8051篇 |
1991年 | 7927篇 |
1990年 | 7610篇 |
1989年 | 7568篇 |
1988年 | 7264篇 |
1987年 | 6375篇 |
1986年 | 6345篇 |
1985年 | 7212篇 |
1984年 | 6759篇 |
1983年 | 6231篇 |
1982年 | 5856篇 |
1981年 | 5970篇 |
1980年 | 5849篇 |
1979年 | 5636篇 |
1978年 | 5668篇 |
1977年 | 6417篇 |
1976年 | 8401篇 |
1975年 | 5076篇 |
1974年 | 4868篇 |
1973年 | 4874篇 |
1972年 | 4201篇 |
1971年 | 3829篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
Bochkareva N. I. Ivanov A. M. Klochkov A. V. Kogotkov V. S. Rebane Yu. T. Virko M. V. Shreter Y. G. 《Semiconductors》2015,49(6):827-835
Semiconductors - It is shown that the emission efficiency and the 1/f noise level in light-emitting diodes with InGaN/GaN quantum wells correlate with how the differential resistance of a diode... 相似文献
105.
106.
107.
108.
109.
Enas Taha Sayed Hussain Alawadhi A.G. Olabi Aisha Jamal Menna Salah Almahdi Juiaria Khalid Mohammad Ali Abdelkareem 《International Journal of Hydrogen Energy》2021,46(8):5975-5983
Microbial fuel cell (MFC) is a promising technology for simultaneous wastewater treatment and energy harvesting. The properties of the anode material play a critical role in the performance of the MFC. In this study, graphene oxide was prepared by a modified hummer's method. A thin layer of graphene oxide was incorporated on the carbon brush using an electrophoretic technique. The deoxygenated graphene oxide formed on the surface of the carbon brush (RGO-CB) was investigated as a bio-anode in MFC operated with real wastewater. The performance of the MFC using the RGO-CB was compared with that using plain carbon brush anode (PCB). Results showed that electrophoretic deposition of graphene oxide on the surface of carbon brush significantly enhanced the performance of the MFC, where the power density increased more than 10 times (from 33 mWm?2 to 381 mWm?2). Although the COD removal was nearly similar for the two MFCs, i.e., with PCB and RGO-CB; the columbic efficiency significantly increased in the case of RGO-CB anode. The improved performance in the case of the modified electrode was related to the role of the graphene in improving the electron transfer from the microorganism to the anode surface, as confirmed from the electrochemical impedance spectroscopy measurements. 相似文献
110.
In this work was investigated the effect of the addition of barium titanate (BaTiO3) on electrical properties of two chemically recyclable thermosets, polyhemiaminal (PHA) and polyhexahydro‐s‐triazine (PHT), both fabricated from 4,4′‐oxydianiline (ODA), an ether derivative of aniline and paraformaldehyde. Thermal and mechanical properties as well as chemical recyclability of the two polymers and their nanocomposites/nanodielectrics were also investigated. In addition, a quantitative analysis was conducted of the nanoparticle dispersion in the PHA‐/PHT‐based BaTiO3‐containing nanocomposites using transmission electron microscopy imaging and the nearest‐neighbor distance index and this index was used to analyze the investigated properties in connection with the proper mechanisms. Regarding the electrical properties for both neat polymers, conductivity values of the order of 10?8 S m?1 at 100 Hz were observed and dielectric constant values close to 2.80 for both polymers at 1 kHz. The addition of 0.5 wt% of BaTiO3 ferroelectric nanoparticles increased by about 44% the dielectric constant (1 kHz) and conductivity (102 Hz) of the PHA‐based nanocomposite. PHA and PHT exhibited glass transition temperature (Tg) values in the range 125–180 °C. An increase of 7 °C in Tg was observed after the incorporation of 0.5 wt% of BaTiO3 into PHA. Concerning the mechanical properties, values in the range 4.00–4.45 GPa for reduced modulus and 0.30–0.43 GPa for nanohardness for PHA and PHT polymers were observed. Independently of filler content or polymer matrix, both mechanical properties were enhanced after the addition of BaTiO3. The chemical recycling of PHA/PHT and all nanocomposites in the initial ODA reagent after sulfuric acid treatment was successfully characterized using the NMR and Fourier transform infrared spectroscopic techniques. © 2018 Society of Chemical Industry 相似文献