全文获取类型
收费全文 | 313650篇 |
免费 | 4752篇 |
国内免费 | 919篇 |
专业分类
电工技术 | 5349篇 |
综合类 | 393篇 |
化学工业 | 50213篇 |
金属工艺 | 12499篇 |
机械仪表 | 9210篇 |
建筑科学 | 7788篇 |
矿业工程 | 1926篇 |
能源动力 | 7653篇 |
轻工业 | 29794篇 |
水利工程 | 3423篇 |
石油天然气 | 7245篇 |
武器工业 | 26篇 |
无线电 | 33327篇 |
一般工业技术 | 60670篇 |
冶金工业 | 56932篇 |
原子能技术 | 7706篇 |
自动化技术 | 25167篇 |
出版年
2021年 | 2927篇 |
2019年 | 2570篇 |
2018年 | 4358篇 |
2017年 | 4405篇 |
2016年 | 4628篇 |
2015年 | 3021篇 |
2014年 | 5081篇 |
2013年 | 13468篇 |
2012年 | 8108篇 |
2011年 | 10775篇 |
2010年 | 8721篇 |
2009年 | 9784篇 |
2008年 | 9979篇 |
2007年 | 9735篇 |
2006年 | 8563篇 |
2005年 | 8085篇 |
2004年 | 7645篇 |
2003年 | 7310篇 |
2002年 | 7365篇 |
2001年 | 7145篇 |
2000年 | 6669篇 |
1999年 | 6683篇 |
1998年 | 16520篇 |
1997年 | 12188篇 |
1996年 | 9378篇 |
1995年 | 7078篇 |
1994年 | 6336篇 |
1993年 | 6246篇 |
1992年 | 4662篇 |
1991年 | 4691篇 |
1990年 | 4476篇 |
1989年 | 4470篇 |
1988年 | 4438篇 |
1987年 | 3739篇 |
1986年 | 3740篇 |
1985年 | 4315篇 |
1984年 | 4078篇 |
1983年 | 3696篇 |
1982年 | 3534篇 |
1981年 | 3663篇 |
1980年 | 3533篇 |
1979年 | 3447篇 |
1978年 | 3513篇 |
1977年 | 4045篇 |
1976年 | 5239篇 |
1975年 | 3225篇 |
1974年 | 3038篇 |
1973年 | 3062篇 |
1972年 | 2678篇 |
1971年 | 2494篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
73.
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
74.
Wireless Personal Communications - In this article compact multiple input multiple output (MIMO) antenna with triple notch at the ultra-wideband application having two identical monopole antennas... 相似文献
75.
Akopdzhanyan T. G. Chemagina E. A. Borovinskaya I. P. 《Russian Journal of Non-Ferrous Metals》2020,61(6):686-690
Russian Journal of Non-Ferrous Metals - The synthesis and sintering of the (AlN)x(SiC)1 – x solid solution have been studied under conditions of self-propagating high-temperature synthesis... 相似文献
76.
77.
The miniaturization has become a key word for advanced integrated circuits over the last few years. It is within this context that the fin field effect tra 相似文献
78.
Isaac Isarn Leïla Bonnaud Lluís Massagus ngels Serra Francesc Ferrando 《Polymer International》2020,69(3):280-290
The enhancement of the thermal conductivity, keeping the electrical insulation, of epoxy thermosets through the addition of pristine and oxidized carbon nanotubes (CNTs) and microplatelets of boron nitride (BN) was studied. Two different epoxy resins were selected: a cycloaliphatic (ECC) epoxy resin and a glycidylic (DGEBA) epoxy resin. The characteristics of the composites prepared were evaluated and compared in terms of thermal, thermomechanical, rheological and electrical properties. Two different dispersion methods were used in the addition of pristine and oxidized CNTs depending on the type of epoxy resin used. Slight changes in the kinetics of the curing reaction were observed in the presence of the fillers. The addition of pristine CNTs led to a greater enhancement of the mechanical properties of the ECC composite whereas the oxidized CNTs presented a greater effect in the DGEBA matrix. The addition of CNTs alone led to a marked decrease of the electrical resistivity of the composites. Nevertheless, in the presence of BN, which is an electrically insulating material, it was possible to increase the proportion of pristine CNTs to 0.25 wt% in the formulation without deterioration of the electrical resistivity. A small but significant synergic effect was determined when both fillers were added together. Improvements of about 750% and 400% in thermal conductivity were obtained in comparison to the neat epoxy matrix for the ECC and DGEBA composites, respectively. © 2019 Society of Chemical Industry 相似文献
79.
An alternative Equivalent Electrical Circuit for Proton Exchange Membrane Fuel Cells is modelled in this study. Both I–V characteristics and H2 consumptions corresponding to generated power under load and no-load conditions are investigated. For this purpose, H2 consumptions and I–V characteristics of three different sized PEMFCs are tested. There is a very good harmony between the model results and measured values (relative error %0.7, %6.4 and %2.5 for FC-A, FC-B and FC-C respectively). In the proposed model current passes only on parallel resistance and not on serial resistance at no-load condition. Thus, a FC with higher parallel resistance should be preferred. Another key output of this study is that based on the proposed model, performance comparison of FCs can be performed with the parameters defined in this work. Proposals made in this study can easily be used for performance analysis of FCs under for both steady state and transient analysis. 相似文献
80.