全文获取类型
收费全文 | 2323篇 |
免费 | 189篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 41篇 |
综合类 | 4篇 |
化学工业 | 444篇 |
金属工艺 | 24篇 |
机械仪表 | 35篇 |
建筑科学 | 80篇 |
能源动力 | 48篇 |
轻工业 | 142篇 |
水利工程 | 3篇 |
石油天然气 | 3篇 |
武器工业 | 1篇 |
无线电 | 524篇 |
一般工业技术 | 453篇 |
冶金工业 | 335篇 |
原子能技术 | 17篇 |
自动化技术 | 378篇 |
出版年
2023年 | 17篇 |
2022年 | 23篇 |
2021年 | 43篇 |
2020年 | 41篇 |
2019年 | 62篇 |
2018年 | 79篇 |
2017年 | 52篇 |
2016年 | 64篇 |
2015年 | 77篇 |
2014年 | 90篇 |
2013年 | 214篇 |
2012年 | 95篇 |
2011年 | 130篇 |
2010年 | 99篇 |
2009年 | 110篇 |
2008年 | 94篇 |
2007年 | 102篇 |
2006年 | 83篇 |
2005年 | 65篇 |
2004年 | 67篇 |
2003年 | 75篇 |
2002年 | 54篇 |
2001年 | 54篇 |
2000年 | 62篇 |
1999年 | 42篇 |
1998年 | 99篇 |
1997年 | 74篇 |
1996年 | 57篇 |
1995年 | 41篇 |
1994年 | 49篇 |
1993年 | 34篇 |
1992年 | 24篇 |
1991年 | 31篇 |
1990年 | 33篇 |
1989年 | 30篇 |
1988年 | 17篇 |
1987年 | 13篇 |
1986年 | 17篇 |
1985年 | 15篇 |
1984年 | 12篇 |
1983年 | 15篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 12篇 |
1979年 | 4篇 |
1977年 | 9篇 |
1976年 | 8篇 |
1974年 | 6篇 |
1973年 | 3篇 |
1970年 | 3篇 |
排序方式: 共有2532条查询结果,搜索用时 0 毫秒
1.
2.
3.
Tsang T.K.K. Kuan-Yu Lin El-Gamal M.N. 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2008,55(3):214-218
This paper presents design techniques of CMOS ultra-wide-band (UWB) amplifiers for multistandard communications. The goal of this paper is to propose a compact, simple, and robust topology for UWB low-noise amplifiers, which yet consumes a relatively low power. To achieve this goal, a common-gate amplifier topology with a local feedback is employed. The first amplifier uses a simple inductive peaking technique for bandwidth extension, while the second design utilizes a two-stage approach with an added gain control feature. Both amplifiers achieve a flat bandwidth of more than 6 GHz and a gain of higher than 10 dB with supply voltages of 1.8-2.5 V. Designs with different metal thicknesses are compared. The advantage of using thick-metal inductors in UWB applications depends on the chosen topology. 相似文献
4.
Yi‐Hung Chen Ching‐Yuan Chang Wei‐Ling Su Chun‐Yu Chiu Yue‐Hwa Yu Pen‐Chi Chiang Chiung‐Fen Chang Je‐Lueng Shie Chyow‐San Chiou Sally IM Chiang 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(1):68-75
This study investigates the ozonation of CI Reactive Black 5 (RB5) by using the rotating packed bed (RPB) and completely stirred tank reactor (CSTR) as ozone contactors. The RPB, which provides high gravitational force by adjusting the rotational speed, was employed as a novel ozone contactor. The same ozone dosage was separately introduced into either the RPB or the CSTR for the investigation, while the experimental solution was continuously circulated within the apparatus consisting of the RPB and CSTR. The decolorization and mineralization efficiencies of RB5 in the course of ozonation are compared for these two methods. Moreover, the dissolved and off‐gas ozone concentrations were simultaneously monitored for the further analysis. As a result, the ozone mass transfer rate per unit volume of the RPB was significantly higher because of its higher mass transfer coefficient and gas–liquid concentration driving force. Furthermore, ozonation kinetics was found to be independent of the gravitational magnitude of an ozone gas–liquid contactor. Therefore, the results suggest employing RPBs as ozone‐contacting devices with the advantage of volume reduction. The experimental results, which can be used for further modeling of the ozonation process in the RPB, also show the requirement of correct design for the RPB. Consequently, the present study is useful for the understanding of practical application of RPBs. Copyright © 2004 Society of Chemical Industry 相似文献
5.
6.
Most of the UK nuclear power reactors are gas-cooled and graphite moderated. As well as acting as a moderator the graphite also acts as a structural component providing channels for the coolant gas and control rods. For this reason the structural integrity assessments of nuclear graphite components is an essential element of reactor design. In order to perform graphite component stress analysis, the definition of the constitutive equation relating stress and strain for irradiated graphite is required. Apart from the usual elastic and thermal strains, irradiated graphite components are subject to additional strains due to fast neutron irradiation and radiolytic oxidation. In this paper a material model for nuclear graphite is presented along with an example of a stress analysis of a nuclear graphite moderator brick subject to both fast neutron irradiation and radiolytic oxidation. 相似文献
7.
Effect of grain boundary phase on the thermal conductivity of aluminium nitride ceramics 总被引:2,自引:0,他引:2
Ching -Fong Chen M. E. Perisse A. F. Ramirez N. P. Padture H. M. Chan 《Journal of Materials Science》1994,29(6):1595-1600
AIN with high thermal conductivity was fabricated by pressureless sintering with Y2O3 as the sintering aid. The thermal conductivity was observed to increase with sintering time (up to 8 h) at 1810 °C. The distribution of the sintering aid was identified as one of the major factors influencing the thermal conductivity in AIN. Non-uniform distribution of the grain boundary phase was found to be associated with a significant amount of porosity, resulting in the enhancement of phonon scattering and thereby lowering the thermal conductivity. 相似文献
8.
9.
Ching‐Nan Chuang Liang Chao Ying‐Jie Huang Tar‐Hwa Hsieh Hung‐Yi Chuang Shu‐Chi Lin Ko‐Shan Ho 《应用聚合物科学杂志》2008,107(6):3917-3924
The synthesis of a p‐toluidine/formaldehyde (PTF) resin was performed, and the effects of the molar ratio of the individual monomers and the polymerization conditions on the structure of the PTF resin were studied. Fourier transform infrared and 13C‐NMR spectra were used to characterize the PTF. Wide‐angle X‐ray diffraction patterns revealed the crystalline structures of various PTFs. Polarized optical microscopy revealed that the molar ratio of the monomers had a strong effect on the crystalline morphologies. A longer polymerization time turned out a polymer with a higher intrinsic viscosity and molecular weight, which led to differences in the proton conductivity. All of the PTFs showed a higher proton conductivity than a commercial Nafion membrane at 90–100°C and 0% relative humidity. The proton conductivity of the PTF series could be improved by sulfonation with sulfuric acid and could be maintained after blending with polyurethane. Pure methanol could be used as a fuel source because of the insolubility and nonwetting properties of PTF in methanol to increase the output current density for a PTF membrane electrode assembly. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2008 相似文献
10.
The Wabash River Integrated Methanol and Power Production from Clean Coal Technologies (IMPPCCT) project is investigating an Early Entrance Coproduction Plant (EECP) concept to evaluate integrated electrical power generation and methanol production from coal and other carbonaceous feedstocks. Research, development and testing (RD&T) that is currently being conducted under the project is evaluating cost effective process systems for removing contaminants, particularly sulfur species, from the generated gas which contains mainly synthesis gas (syngas), CO2 and steam at concentrations acceptable for the methanol synthesis catalyst. The RD&T includes laboratory testing followed by bench-scale and field testing at the SG Solutions Gasification Plant located in West Terre Haute, Indiana. Actual synthesis gas produced by the plant was utilized at system pressure and temperature for bench-scale field testing. 相似文献