全文获取类型
收费全文 | 358072篇 |
免费 | 6222篇 |
国内免费 | 1527篇 |
专业分类
电工技术 | 6368篇 |
综合类 | 497篇 |
化学工业 | 57711篇 |
金属工艺 | 15316篇 |
机械仪表 | 10635篇 |
建筑科学 | 8903篇 |
矿业工程 | 2165篇 |
能源动力 | 8634篇 |
轻工业 | 32523篇 |
水利工程 | 3774篇 |
石油天然气 | 8248篇 |
武器工业 | 27篇 |
无线电 | 36817篇 |
一般工业技术 | 73096篇 |
冶金工业 | 63325篇 |
原子能技术 | 8329篇 |
自动化技术 | 29453篇 |
出版年
2021年 | 3230篇 |
2019年 | 2863篇 |
2018年 | 5399篇 |
2017年 | 5315篇 |
2016年 | 5777篇 |
2015年 | 4039篇 |
2014年 | 6238篇 |
2013年 | 16581篇 |
2012年 | 9783篇 |
2011年 | 12737篇 |
2010年 | 10406篇 |
2009年 | 11594篇 |
2008年 | 11924篇 |
2007年 | 11824篇 |
2006年 | 10185篇 |
2005年 | 9225篇 |
2004年 | 8532篇 |
2003年 | 8180篇 |
2002年 | 8151篇 |
2001年 | 7961篇 |
2000年 | 7440篇 |
1999年 | 7569篇 |
1998年 | 18358篇 |
1997年 | 13600篇 |
1996年 | 10610篇 |
1995年 | 7940篇 |
1994年 | 7050篇 |
1993年 | 6916篇 |
1992年 | 5203篇 |
1991年 | 5114篇 |
1990年 | 4875篇 |
1989年 | 4869篇 |
1988年 | 4709篇 |
1987年 | 4096篇 |
1986年 | 4058篇 |
1985年 | 4739篇 |
1984年 | 4473篇 |
1983年 | 4055篇 |
1982年 | 3831篇 |
1981年 | 4044篇 |
1980年 | 3913篇 |
1979年 | 3789篇 |
1978年 | 3806篇 |
1977年 | 4509篇 |
1976年 | 5974篇 |
1975年 | 3525篇 |
1974年 | 3328篇 |
1973年 | 3379篇 |
1972年 | 2897篇 |
1971年 | 2708篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
102.
103.
104.
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
105.
Ming-Puu Chen Asta Y. Z. Lord Yu-Yao Cheng Ku-Chou Tai Wen-Harn Pan 《Journal of Computer Assisted Learning》2020,36(3):383-396
Reflective judgement is crucial for medical-related practitioners in dealing with controversial issues. However, the conformity phenomenon is likely to occur and interfere with reflective judgement learning during interactive activities. Effective strategies are required to moderate the conformity behaviour tendency (CBT) and improve reflective judgement performance (RJP). This study demonstrates two significant results: (a) Compared with the guided self-reflection learning strategy, the online collective reflection (OCR) learning strategy effectively weakened the learners' general CBT while dealing with professional controversial issues; and (b) a significantly negative correlation between the RJP achieved and the change of CBT in online environment was detected in the OCR group. The implications and potential applications in higher education were discussed. Further studies are needed to confirm the long-term effects and the extending application to other professional studies. 相似文献
106.
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
107.
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
108.
Sebastian Roth Peter Stockinger Jakob Steff Simon Steimle Dr. Viktor Sautner Prof. Dr. Kai Tittmann Prof. Dr. Jürgen Pleiss Prof. Dr. Michael Müller 《Chembiochem : a European journal of chemical biology》2020,21(18):2615-2619
The family of NAD(P)H-dependent short-chain dehydrogenases/reductases (SDRs) comprises numerous biocatalysts capable of C=O or C=C reduction. The highly homologous noroxomaritidine reductase (NR) from Narcissus sp. aff. pseudonarcissus and Zt_SDR from Zephyranthes treatiae, however, are SDRs with an extended imine substrate scope. Comparison with a similar SDR from Asparagus officinalis (Ao_SDR) exhibiting keto-reducing activity, yet negligible imine-reducing capability, and mining the Short-Chain Dehydrogenase/Reductase Engineering Database indicated that NR and Zt_SDR possess a unique active-site composition among SDRs. Adapting the active site of Ao_SDR accordingly improved its imine-reducing capability. By applying the same strategy, an unrelated SDR from Methylobacterium sp. 77 (M77_SDR) with distinct keto-reducing activity was engineered into a promiscuous enzyme with imine-reducing activity, thereby confirming that the ability to reduce imines can be rationally introduced into members of the “classical” SDR enzyme family. Thus, members of the SDR family could be a promising starting point for protein approaches to generate new imine-reducing enzymes. 相似文献
109.
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
110.
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