全文获取类型
收费全文 | 5193篇 |
免费 | 539篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 53篇 |
综合类 | 1篇 |
化学工业 | 1439篇 |
金属工艺 | 166篇 |
机械仪表 | 308篇 |
建筑科学 | 91篇 |
矿业工程 | 3篇 |
能源动力 | 243篇 |
轻工业 | 440篇 |
水利工程 | 9篇 |
石油天然气 | 1篇 |
无线电 | 1009篇 |
一般工业技术 | 1309篇 |
冶金工业 | 152篇 |
原子能技术 | 69篇 |
自动化技术 | 450篇 |
出版年
2024年 | 6篇 |
2023年 | 81篇 |
2022年 | 86篇 |
2021年 | 194篇 |
2020年 | 139篇 |
2019年 | 173篇 |
2018年 | 212篇 |
2017年 | 202篇 |
2016年 | 235篇 |
2015年 | 213篇 |
2014年 | 317篇 |
2013年 | 367篇 |
2012年 | 421篇 |
2011年 | 468篇 |
2010年 | 338篇 |
2009年 | 321篇 |
2008年 | 357篇 |
2007年 | 212篇 |
2006年 | 184篇 |
2005年 | 162篇 |
2004年 | 186篇 |
2003年 | 157篇 |
2002年 | 132篇 |
2001年 | 94篇 |
2000年 | 84篇 |
1999年 | 81篇 |
1998年 | 89篇 |
1997年 | 52篇 |
1996年 | 40篇 |
1995年 | 26篇 |
1994年 | 22篇 |
1993年 | 12篇 |
1992年 | 14篇 |
1991年 | 6篇 |
1990年 | 15篇 |
1989年 | 12篇 |
1988年 | 3篇 |
1987年 | 10篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有5743条查询结果,搜索用时 6 毫秒
11.
Kum‐Il Lee Yong‐Sik Yim Sang‐Wook Chung Jiaqiu Wei Jong Il Rhee 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(9):1036-1045
A two‐dimensional (2D) spectrofluorometer was used to monitor various fermentation processes with recombinant E coli for the production of 5‐aminolevulinic acid (ALA). The whole fluorescence spectral data obtained during a process were analyzed using artificial neural networks, ie self‐organizing map (SOM) and feedforward backpropagation neural network (BPNN). The SOM‐based classification of the whole spectral data has made it possible to qualitatively associate some process parameters with the normalized weights and variances, and to select some useful combinations of excitation and emission wavelengths. Based on the classified fluorescence spectra a supervised BPNN algorithm was used to predict some of the process parameters. It was also shown that the BPNN models could elucidate some sections of the process's performance, eg forecasting the process's performance. Copyright © 2005 Society of Chemical Industry 相似文献
12.
13.
14.
Quantitative analysis of isothermal crystallization kinetics of PLA/clay nanocomposite and PLA/clay/regenerated cellulose fiber (RCF) hybrid composite has been conducted. The crystallization rate constant (k) according to Avrami equation was higher in PLA/clay nanocomposite than in PLA/clay/RCF hybrid composite at the same crystallization temperature. The equilibrium melting temperature obtained by Hoffman–Weeks equation was almost same in both composites, whereas stability parameter was greater in hybrid composite than in nanocomposite. Activation energy of hybrid composite for crystallization was larger than that of nanocomposite. The value of nucleation parameter (Kg) and surface free energy (se) of hybrid composite were larger than nanocomposite, indicating that hybrid composite has a less folding regularity than nanocomposite. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
15.
Jung-Ho Song Jung-Woo Park Eun-Deok Sim Yongsoon Baek 《Photonics Technology Letters, IEEE》2005,17(9):1791-1793
Amplified spontaneous emission (ASE) spectra of passive waveguide integrated lasers have been studied to estimate the coupling efficiency and the reflectivity at the butt-joints between active and passive waveguides. A new method has been proposed for the analysis of ASE to extract the coupling efficiency and reflectivity at the butt-joints. This method was applied experimentally to estimate the coupling and reflection of the passive waveguide integrated lasers with different amounts of vertical misalignments of active and passive waveguides. 相似文献
16.
Woo Yong Sung Seung Min Lee Wal Jun Kim Jong Girl Ok Ho Young Lee Yong Hyup Kim 《Diamond and Related Materials》2008,17(6):1003-1007
Complementary electroplating combined with electrophoresis enhanced the field emission characteristics of emitters by improving the adhesions between CNT emitters and substrate. The emitting current of the CNT emitters prepared by our combined method increased nine times higher than that of CNT emitters prepared by electrophoresis only, since electroplating improved the adhesion of CNT emitters. During the life-time measurement for 10 h, the emitting current of CNT emitters fabricated by electrophoresis only was drastically decreased to 13% of the initial current, while that prepared by the combination of electrophoresis and successive electroplating decreased to 64% of the initial current. We suggest that our method is a promising approach for the efficient fabrication of reliable CNT emitters. 相似文献
17.
18.
Ehsani M. Bilgic M.O. Khan S. Laskai L. Seung Gi Jeong 《Power Electronics, IEEE Transactions on》1995,10(4):511-518
The bang-bang controlled capacitor coupled converter (C3) is described in this paper. Due to the converter's inherent commutating property, the C3 can accommodate thyristors as well as high-power gate turn-off switches, due to zero-current switching transitions. The zero-current switching is achieved at no current stress increase, therefore, the topology is considered appropriate for high-power processing. DC and small signal AC models are derived for the bang-bang controlled C3, a design procedure is proposed, and simulation results are discussed. Finally, oscillograms from a proof of principle prototype circuit are presented 相似文献
19.
20.
Understanding information sharing is an important challenge to modern organizations, and is likely to be increasingly considered when IT investment decisions are made world-wide. Our research study investigated the influence of cultural factors on information sharing in China. It was postulated that social network structures such as guanxi, Confucian dynamism, and collectivism could explain the degree to which information sharing took place between people in China. It was found that guanxi, Confucian dynamism, and collectivism all had a significant influence on information sharing. 相似文献