全文获取类型
收费全文 | 645篇 |
免费 | 32篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 8篇 |
综合类 | 2篇 |
化学工业 | 200篇 |
金属工艺 | 23篇 |
机械仪表 | 20篇 |
建筑科学 | 31篇 |
矿业工程 | 2篇 |
能源动力 | 50篇 |
轻工业 | 31篇 |
水利工程 | 20篇 |
石油天然气 | 17篇 |
无线电 | 41篇 |
一般工业技术 | 85篇 |
冶金工业 | 17篇 |
原子能技术 | 7篇 |
自动化技术 | 127篇 |
出版年
2024年 | 3篇 |
2023年 | 10篇 |
2022年 | 24篇 |
2021年 | 38篇 |
2020年 | 42篇 |
2019年 | 34篇 |
2018年 | 48篇 |
2017年 | 42篇 |
2016年 | 41篇 |
2015年 | 32篇 |
2014年 | 43篇 |
2013年 | 61篇 |
2012年 | 39篇 |
2011年 | 52篇 |
2010年 | 30篇 |
2009年 | 28篇 |
2008年 | 22篇 |
2007年 | 14篇 |
2006年 | 9篇 |
2005年 | 8篇 |
2004年 | 6篇 |
2003年 | 7篇 |
2002年 | 11篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1976年 | 2篇 |
排序方式: 共有681条查询结果,搜索用时 15 毫秒
81.
82.
M. Bayat 《Petroleum Science and Technology》2017,35(16):1635-1641
Auto-thermal heat exchanger configurations are recognized as a novel concept in process intensification. In the current study, the influence of operating conditions in a novel coupling reactor with radial-flow pattern is investigated for heavy paraffin dehydrogenation process. Catalytic hydrogenation of nitrobenzene to aniline takes place in the exothermic side and supplies the necessary heat for the endothermic dehydrogenation of heavy paraffin reaction. The performance of the reactor is numerically investigated for various key operating variables, such as inlet molar flow rates of exothermic and endothermic streams, number of subsections, and exothermic side angle. The reactor performance is analyzed based on temperature, olefin production rate, and nitrobenzene conversion. 相似文献
83.
This article presents an overview of the commercialisation experiences of photovoltaics and draws some conclusion from the past and applies them to the future. In particular, the development for this industry in Africa is examined to identify the areas of strength and potential as well as the necessary infrastructure—for production, distribution and installation in order to support its growth. The question of capital requirement versus the efficiency of photovoltaics is highlighted and the reliabilty factor is analysed. As a result of examining the past, three issues seem crucial for the future development of photovoltaics, especially in Africa: (1) technology development; (2) education; (3) finance. These issues are addressed and their interdependence and impact on the use of photovoltaics are explored. The success stories of several photovoltaic companies in Africa, in spite of their problems, can be a source of optimism for the future contribution of this industry to the improved quality of life and economic growth as well as the employment opportunities on this continent. Finally, a method of co-operation between research in photovoltaics at the universities and local industry is proposed as part of the Research and Development (R&D) infrastructure necessary for the technical support of this field. 相似文献
84.
Leonardo C. Kammer Farhad Ein-Mozaffari Guy A. Dumont Chad P. J. Bennington 《Journal of Process Control》2005,15(1):31-38
This paper describes a mechanism for identifying the dynamics of non-ideal mixing processes. The object is to study two of the non-ideal behaviours of agitated pulp stock chests: recirculation and channelling. An initial continuous-time model, which contains physically relevant parameters, is transformed into its discrete-time counterpart. This transformation introduces some challenging identification problems, as the discrete-time parameters become a non-linear combination of the original continuous-time parameters. A system identification methodology that addresses these challenges is developed and demonstrated by means of computer simulation. The analysis of data collected from experiments on a laboratory scale model of an industrial chest shows the potential of the techniques developed in this paper. 相似文献
85.
Concrete is an inherently brittle material with a relatively low tensile strength compared to compressive strength. Reinforcement with randomly distributed short fibres presents an effective approach to the stabilization of the crack and improving the ductility and tensile strength of concrete. A variety of fibre types, including steel, synthetics, and natural fibres, have been applied to concrete. Polypropylene (PP) fibre reinforcement is considered to be an effective method for improving the shrinkage cracking characteristics, toughness, and impact resistance of concrete materials. Also, the use of PP fibre has been recommended by all of the researchers to reduce and eliminate the risk of the explosive spalling in high strength concrete at elevated temperatures. In this study, constitutive relationships are developed for normal and high-strength PP fibre reinforcement concrete (PPFRC) subjected to high temperatures to provide efficient modelling and specify the fire-performance criteria for concrete structures. They are developed for unconfined PPFRC specimens that include compressive and tensile strengths, elastic modulus, modulus of rupture, strain at peak stress as well as compressive stress–strain relationships at elevated temperatures. The proposed relationships at elevated temperature are compared with experimental results. These results are used to establish more accurate and general compressive stress–strain relationships prediction. Further experimental results for tension and the other main parameters at elevated temperature are needed in order to establish well-founded models and to improve the proposed constitutive relationships, which are general, rational, and fit well with the experimental results. 相似文献
86.
Degradation of RC (reinforced concrete) in maritime structures has become a worldwide problem due to its excessive costs of maintenance, repair and replacement in addition to its environmental impacts and safety issues. Degradation of both concrete and steel which is the main reason of reduction in the service life of RC structures strongly depends on the diffusion process of moisture and aggressive species. In this paper, the major and popular mathematical models of diffusion process in concrete are surveyed and investigated. Predominantly in these models, the coefficient of chloride diffusion into the concrete is assumed to be constant. Whereas, experimental records indicate that diffusion coefficient is a function of time. Subsequently, data analysis and comparisons between the existing analytical models for predicting the diffusion coefficient with the existing experimental database are carried out in this study. Clearly, these comparisons reveal that there are gaps between the existing mathematical models and previously recorded experimental results. Perhaps, these gaps may be interpreted as influence of the other affecting parameters on the diffusion coefficient such as temperature, aggregate size and relative humidity in addition to the water cement ratio. Accordingly, the existing mathematical models are not adequate enough to predict the diffusion coefficient precisely and further studies need to be performed. 相似文献
87.
Farhad?M.?HossainEmail author M.?HasanuzzamanEmail author N.?A.?Rahim H.?W.?Ping 《Clean Technologies and Environmental Policy》2015,17(4):859-871
Malaysia is rich in renewable energy (RE) resources. Hybrid systems of these resources can contribute strongly to the electrification and sustainable development of rural areas that do not have access to electricity grids. The integration of the generation of hybrid renewable power in remote and rural areas supplies the required power demand and mitigates emissions. Thus, this study reviews the latest literature (theses, journals articles, and conference proceedings) on the need for electricity in remote rural communities, on hybrid RE systems, on environmental impact, and on economic regulation in Malaysia. Power in this country is mainly generated by fossil fuels that emit high concentrations of greenhouse gases. Thus, RE is a potential alternative for to electrify rural areas, to meet current and future energy demands, and to mitigate emissions. Moreover, Malaysia has pledged to reduce its carbon-emission intensity by a maximum of 40 % (2005 level) by the year 2020. Therefore, the implementation of RE technologies in this country is significantly aided by RE projects, research and development activities, technologies, energy policies, and future direction. This review concludes that solar, wind, hydro, and biomass energy, as well as a hybrid of these, can effectively electrify rural areas. 相似文献
88.
89.
A. Shahrjerdi F. Mustapha M. Bayat D. L. A. Majid 《Journal of Mechanical Science and Technology》2011,25(9):2195-2209
Second-order shear deformation theory (SSDT) is employed to analyze vibration of temperature-dependent solar functionally
graded plates (SFGP’s). Power law material properties and linear steady-state thermal loads are assumed to be graded along
the thickness. Two different types of SFGP’s such as ZrO2/Ti-6Al-4V and Si3N4/SUS304 are considered. Uniform, linear, nonlinear, heat-flux and sinusoidal thermal conditions are imposed at the upper and
lower surface for simply supported SFGPs. The energy method is applied to derive equilibrium equations, and solution is based
on Fourier series that satisfy the boundary conditions (Navier’s method). Non-dimensional results are compared for temperature-dependent
and temperature-independent SFGP’s and validated with known results in the literature. Numerical results indicate the effect
of material composition, plate geometry, and temperature fields on the vibration characteristics and mode shapes. The results
obtained using the SSDT are very close to results from other shear deformation theories. 相似文献
90.
S. Farhad Masoudi 《Journal of Fusion Energy》2010,29(3):275-278
The ion acceleration inside the collisionless plasma sheath is investigated at the presence of external magnetic field. By using the fluid model, the number and momentum equations of the ions and the Boltzmann and Poisson equations are solved numerically in the case that the ion beam has a small divergency at the plasma sheath boundary. It is shown that the kinetic energy of the ions has a strong dependency to the magnitude of divergency when the magnetic field has a small component parallel to the sheath boundary. 相似文献