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91.
A new approach to computing sub-surface stresses in an elastic half-space subjected to a line loading is presented. The approach
is based on the discrete element method (DEM) in which the material continuum is replaced by a set of convex, rigid, interacting
elements connected through visco-elastic fibers. A Hertzian pressure profile with, and without surface traction is applied
to a semi-infinite domain created by gluing together discrete elements. Stresses are calculated from the inter-element joint
forces that develop due to relative motion of the elements. Newton’s laws are employed to simulate the motion of each element.
The stress distribution obtained from the discrete element model compares very well with that obtained from continuum elasticity
models. The paper illustrates the applicability of the DEM to analysis of contacts at the microlevel and serves as a foundation
to further studies in fracture and fatigue of bearing materials. 相似文献
92.
3D Printing: 3D Printing of Highly Stretchable and Tough Hydrogels into Complex,Cellularized Structures (Adv. Mater. 27/2015) 下载免费PDF全文
93.
Membrane bioreactor for treatment of pharmaceutical wastewater containing acetaminophen 总被引:1,自引:0,他引:1
Farshid Pajoum Shariati Bahreh Madadkhah Salmasi Christelle Wisniewski 《Desalination》2010,250(2):798-800
Treatment of pharmaceutical wastewater is a real challenge for wastewater engineers. In this study, a pilot-scale system including an external loop airlift membrane bioreactor (ELAMBR) was applied for treatment of a synthetic pharmaceutical wastewater. The performance of this system was evaluated in removal of acetaminophen as the main pollutant of a pharmaceutical wastewater. A conventional activated sludge (CAS process) laboratory system was used in parallel with this system to compare both systems in regard to their ability for acetaminophen removal. The performance of the ELAMBR system was monitored for approximately one month to investigate the long-term operational stability of the system and possible effects of solids retention time on the efficiency of removal of acetaminophen. The removal efficiency was significantly higher in the ELAMBR system than the CAS process. 100% of the acetaminophen was removed after 2 days in this system. The results also showed that initial concentration of acetaminophen, chemical oxygen demand (COD) and mixed liquid suspended solids (MLSS) are the most effective parameters in removal of a pollutant such as acetaminophen. This study demonstrates the usefulness of ELAMBR system for pharmaceutical wastewater treatment with the advantages such as: (i) simple operation and maintenance, (ii) efficient removal of pharmaceutical pollutant and COD and (iii) low-energy consumption. 相似文献
94.
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96.
Farshid Jandaghi Alaee Bhushan Lal Karihaloo 《Canadian Metallurgical Quarterly》2003,129(9):1028-1038
A new retrofitting technique based on a material [Cardiff Fiber Reinforced Concrete (CARDIFRC)] compatible with concrete has been developed at Cardiff University. It overcomes some of the problems associated with the current techniques based on externally bonded steel plates and fiber-reinforced plastic laminates which are due to the mismatch of their tensile strength and stiffness with that of the concrete structure being retrofitted. CARDIFRC is characterized by high tensile/flexural strength and high energy-absorption capacity (i.e., ductility). The special characteristics of CARDIFRC make it particularly suitable for repair, remedial and upgrading activities (i.e., retrofitting) of existing concrete structures. It has been shown that damaged reinforced concrete beams can be successfully strengthened and rehabilitated in a variety of different retrofit configurations using precast CARDIFRC strips adhesively bonded to the prepared surfaces of the damaged beams. To predict the moment resistance of the beams retrofitted in this manner an analytical model is introduced in the present paper. This model takes a fracture mechanics approach and follows the initiation and growth of the flexural crack that eventually leads to the failure of the retrofitted beams. The results of this analytical model are found to be in very good agreement with the test results. 相似文献
97.
Lubricin and hyaluronic acid (HA), molecular constituents of synovial fluid, have long been theorized to play a role in joint lubrication and wear protection. While lubricin has been shown to function as a boundary lubricant, conflicting evidence exists as to the boundary lubricating ability of hyaluronic acid. Here, we use colloidal force microscopy to explore the friction behavior of these two molecules on the microscale between chemically uniform hydrophilic (hydroxyl-terminated) and hydrophobic (methyl-terminated) surfaces in physiological buffer solution. Behaviors on both surfaces are physiologically relevant since the heterogeneous articular cartilage surface contains both hydrophilic and hydrophobic elements. Friction between hydrophobic surfaces was initially high (μ=1.1, at 100nN of applied normal load) and was significantly reduced by lubricin addition while friction between hydrophilic surfaces was initially low (μ=0.1) and was slightly increased by lubricin addition. At lubricin concentrations above 200 μg/ml, friction behavior on the two surfaces was similar (μ=0.2) indicating that nearly all interaction between the two surfaces was between adsorbed lubricin molecules rather than between the surfaces themselves. In contrast, addition of HA did not appreciably alter the frictional behavior between the model surfaces. No synergistic effect on friction behavior was seen in a physiological mixture of lubricin and HA. Lubricin can equally mediate the frictional response between both hydrophilic and hydrophobic surfaces, likely fully preventing direct surface-to-surface contact at sufficient concentrations, whereas HA provides considerably less boundary lubrication. 相似文献
98.
There is considerable interest in modeling the performance of ad hoc networks analytically. This paper presents approximate
analytical models for the throughput performance of single-hop and multi-hop ad hoc networks. The inherent complexity of analysis
of a multi-hop ad hoc network together with the fact that the behavior of a node is dependent not only on its neighbors' behavior,
but also on the behavior of other unseen nodes makes multi-hop network analysis extremely difficult. However, our approach
in this paper to analyze multi-hop networks offers an accurate approximation with moderate complexity. Our approach is based
on characterizing the behavior of a node by its state and the state of the channel it sees. This approach is used to carry
out an analysis of single-hop and multi-hop ad hoc networks in which different nodes may have different traffic loads. In
order to validate the model, it is applied to IEEE 802.11-based networks, and it is shown through extensive simulations that
the model is very accurate.
Farshid Alizadeh-Shabdiz received his B.Sc. in 1989 at University of Science and Technology, M.Sc. in 1991 at Tehran University, Iran, and D.Sc. in
2004 at the George Washington University. He is a senior research engineer in Advanced Solution Group, part of Cross Country
Automotive Services, and he is also a part time faculty member at Boston University.
Dr. Alizadeh-Shabdiz was part of the design and implementation team of the three first satellite-based mobile networks: ICO
global medium orbit satellite network voice and data services, Thuraya GEO satellite network, and the first phase of Inmarsat
high speed data network. His research interests include MAC layer, physical layer and network layer of wireless and satellite
networks.
Suresh Subramaniam received the Ph.D. degree in electrical engineering from the University of Washington, Seattle, in 1997. He is an Associate
Professor in the Department of Electrical and Computer Engineering at the George Washington University, Washington, DC. His
research interests are in the architectural, algorithmic, and performance aspects of communication networks, with particular
emphasis on optical and wireless ad hoc networks.
Dr. Subramaniam is a co-editor of the books “Optical WDM Networks – Principles and Practice” and “Emerging Optical Network
Technologies: Architectures, Protocols, and Performance”. He has been on the program committees of several conferences including
Infocom, ICC, Globecom, and Broadnets, and served as TPC Co-Chair for the 2004 Broadband Optical Networking Symposium. He
currently serves on the editorial boards of Journal of Communications and Networks and IEEE Communications Surveys and Tutorials.
He is a co-recipient of the Best Paper Award at the 1997 SPIE Conference on All-Optical Communication Systems. 相似文献
99.
Sedigheh Ghanbarzadeh Nodehi G. V. Shivashankar Jacques Prost Farshid Mohammad-Rafiee 《Journal of the Royal Society Interface》2021,18(176)
We analyse the stem cell nucleus shape fluctuation spectrum obtained from optical confocal microscopy on an hour time scale with 10 s resolution. In particular, we investigate the angular and time dependencies of these fluctuations, define appropriate correlation functions that reveal the fundamentally out of equilibrium nature of the observed fluctuations as well as their global anisotropy. Langevin equations respecting the symmetry of the system allow us to model the damped oscillatory behaviour of the time correlations. 相似文献
100.
A powdered natural clinoptilolite-rich tuff (100 mesh) from Semnan region of Iran was successfully converted to higher value-added synthetic zeolite A (submicron particles of ~ 200–300 nm) in a single stage procedure under a hydrothermal condition. Effect of different parameters such as crystallization temperature, sodium hydroxide concentration, solid/liquid ratio (the mass of clinoptilolite; g; to the volume of sodium hydroxide solution; ml) and crystallization duration on the final product were investigated. The formation of zeolite A was ascertained by X-ray powder diffraction, X-ray florescence (chemical analysis), and scanning electron microscopy techniques. The results were revealed that reaction temperature of 353 K, sodium hydroxide concentration of 2 M, crystallization time of 4 h, and solid to liquid ratio of 1/18 were optimized condition for this conversion. 相似文献