全文获取类型
收费全文 | 2009篇 |
免费 | 95篇 |
国内免费 | 16篇 |
专业分类
电工技术 | 44篇 |
综合类 | 7篇 |
化学工业 | 466篇 |
金属工艺 | 45篇 |
机械仪表 | 60篇 |
建筑科学 | 77篇 |
矿业工程 | 5篇 |
能源动力 | 123篇 |
轻工业 | 142篇 |
水利工程 | 20篇 |
石油天然气 | 14篇 |
无线电 | 193篇 |
一般工业技术 | 464篇 |
冶金工业 | 154篇 |
原子能技术 | 13篇 |
自动化技术 | 293篇 |
出版年
2024年 | 6篇 |
2023年 | 26篇 |
2022年 | 55篇 |
2021年 | 80篇 |
2020年 | 62篇 |
2019年 | 55篇 |
2018年 | 95篇 |
2017年 | 68篇 |
2016年 | 69篇 |
2015年 | 46篇 |
2014年 | 74篇 |
2013年 | 138篇 |
2012年 | 85篇 |
2011年 | 106篇 |
2010年 | 94篇 |
2009年 | 90篇 |
2008年 | 96篇 |
2007年 | 99篇 |
2006年 | 67篇 |
2005年 | 65篇 |
2004年 | 42篇 |
2003年 | 48篇 |
2002年 | 30篇 |
2001年 | 29篇 |
2000年 | 19篇 |
1999年 | 31篇 |
1998年 | 42篇 |
1997年 | 28篇 |
1996年 | 29篇 |
1995年 | 30篇 |
1994年 | 26篇 |
1993年 | 24篇 |
1992年 | 22篇 |
1991年 | 22篇 |
1990年 | 10篇 |
1989年 | 15篇 |
1988年 | 9篇 |
1987年 | 17篇 |
1986年 | 15篇 |
1985年 | 19篇 |
1984年 | 14篇 |
1983年 | 13篇 |
1982年 | 10篇 |
1981年 | 12篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1977年 | 14篇 |
1976年 | 11篇 |
1975年 | 4篇 |
排序方式: 共有2120条查询结果,搜索用时 531 毫秒
71.
72.
73.
An investigation of the electrical transport properties of graphene-oxide thin films 总被引:3,自引:0,他引:3
Gunasekaran Venugopal Karthikeyan KrishnamoorthyRajneesh Mohan Sang-Jae Kim 《Materials Chemistry and Physics》2012,132(1):29-33
The electrical transport properties of graphene-oxide (GO) thin films were investigated. The GO was synthesized by a modified Hummers method and was characterized by X-ray diffraction and UV-visible spectroscopy. The thin film of GO was made on a Si/SiO2 substrate by drop-casting. The surface morphology of the GO film was analyzed by using scanning electron microscopy and atomic force microscopy techniques. Temperature dependent resistance and current-voltage measurements were studied using four-terminal method at various temperatures (120, 150, 175, 200, 250 and 300 K) and their charge transport followed the 3D variable range hopping mechanism which was well supported by Raman spectra analysis. The presence of various functional groups in GO were identified by using high resolution X-ray photo electron (XPS) and Fourier transform infra red (FT-IR) spectroscopic techniques. Graphene-oxide thin film field effect transistor devices show p-type semiconducting behavior with a hole mobility of 0.25 cm2 V−1 s−1 and 0.59 cm2 V−1 s−1 when measured in air and vacuum respectively. 相似文献
74.
75.
76.
77.
G. Mohan Kumar P. Ilanchezhiyan Jin Kawakita Jinsub Park R. Jayavel 《Journal of Materials Science: Materials in Electronics》2013,24(8):2989-2994
One-dimensional Mn doped ZnO nanocrystallites were synthesized through a facile low temperature surfactant free chemical route. The crystallite structure and morphological evolution of the particles were revealed to be of wurtzite phase and rod like structures from the X-ray diffraction and transmission electron microscopic analysis, respectively. Using Raman spectroscopy the role of oxygen related defects and phase purity in the Mn substituted ZnO systems were studied systematically. A significant suppression in the sub-band edge emission was visualized in the room temperature emission spectra of the Mn doped systems. The intensity ratio in between the near-band edge and defect-level emissions was observed to increase, signifying the reduction in oxygen related defects and revealing their influence on the crystallinity on the Mn substituted ZnO species. These variations were correlated with the increasing number of Mn ions in the host lattice, which results with their passivating action on the surface defects. 相似文献
78.
P. Ilanchezhiyan C. Siva T. W. Kang G. Mohan Kumar 《Journal of Materials Science: Materials in Electronics》2016,27(6):5557-5562
Solution processed wide band gap dielectrics have nowadays started to receive renewed interest for practical application in semiconductor electronics. In this regard, undoped and gadolinium (Gd) doped zirconia (ZrO2) nanocrystallites were colloidally processed and their potential for dielectric applications has been demonstrated. X-ray diffraction measurements revealed the effective crystallization of nanostructures and the successful substitution of Gd ions into the cubic ZrO2 matrix. The particulate-like characteristics of undoped and Gd doped ZrO2 nanostructures were examined through the electron microscopes, which hardly revealed any difference among them. The optical band gap of ZrO2 nanostructures was determined to be around 4.64–4.80 eV from the absorbance measurements. The potential of Gd doped ZrO2 nanostructures for dielectric functions were evaluated through electrochemical impedance spectroscopic measurements. The improved capacitance values estimated from the Nyquist plots suggests the potential of the investigated materials for low power and low voltage electronic applications. 相似文献
79.
V. Srinivas Ch. Kodanda Rama Rao N. Mohan Rao 《Tribology - Materials, Surfaces & Interfaces》2018,12(2):107-114
This paper studies the effect of surface modification of multiwall carbon nanotubes (MWCNTs) prior to dispersion in engine oil to improve the tribological properties. The MWCNTs are stabilised in the lubricant with two different surfactants cetrimonium bromide (CTAB) and sorbitan monooleate (SPAN 80) and the effect of surfactants on the tribological properties has been studied. Pristine and surface modified MWCNTs in weight per cent range of 0·5% are dispersed in CI4 plus diesel engine oil. The foaming tendency and other physico-chemical properties of test lubricant have been studied to investigate the effect of nano materials and surfactants. The anti-wear and anti-friction properties are tested on a four ball wear tester and the comparison is made to assess the relative performance of pristine MWCNTs over surface modified MWCNTs. A strong influence of the surface modification technique is found on lubricating and physico-chemical properties. Both CTAB and SPAN 80 could keep the MWCNTs stable in the lubricant without compromising the foaming tendency of lubricant and other physico-chemical properties. The friction and wear characteristics of lubricants have improved with the dispersion of surface modified MWCNTs while there is no improvement in the properties of lubricant dispersed with pristine MWCNTs. 相似文献
80.
Wireless Personal Communications - Nowadays, Wireless Sensor Networks (WSNs) is enhancing for different applications. Simultaneously, energy consumption for processing the tasks in most of the... 相似文献