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Global demand for power has significantly increased, but power generation and transmission capacities have not increased proportionally with this demand. As a result, power consumers suffer from variou... 相似文献
3.
AHMAD Aldarouich 《计算机辅助绘图.设计与制造(英文版)》2008,(2)
Motion control can be considered as the synergistic collaboration of mechanical and electrical engineering, computer science and information technology to apply a controlled force to achieve useful motion in fluid or soiled electromechanical systems. With the development of computer, electronics, and automatic control theory, motion control comes to a new stage. Great applications are based on the characteristics, stemming from advantages of electronics and modern control technology achievements, having a v... 相似文献
4.
Shameem Ahmed Moushumi Sharmin Sheikh I. Ahamed 《Universal Access in the Information Society》2008,7(4):273-283
Universal access from a handheld device (such as a PDA, cell phone) at any time or anywhere is now a reality. Ubicomp Assistant
(UA) (Sharmin et al. in Proceedings of the 21st annual ACM symposium on applied computing (ACM SAC 2006), Dijon, France, pp
1013–1017, 2006) is an integral service of MARKS (Sharmin et al. in Proceedings of the third international conference on information
technology: new generations (ITNG 2006), Las Vegas, Nevada, USA, pp 306–313, 2006). It is a middleware developed for handheld
devices, and has been designed to accommodate different types of users (e.g., education, healthcare, marketing, or business).
This customizable service employs the ubiquitous nature of current short range, low-power wireless connectivity and readily
available, low-cost lightweight mobile devices. These devices can reach other neighbouring devices using a free short-range
ad hoc network. To the best of the authors’ knowledge, the UA service is the only service designed for these devices. This
paper presents the details of Ubi-App, a ubiquitous application for universal access from any handheld device, which uses
UA as a service. The results of a usability test and performance evaluation of the prototype show that Ubi-App is useful,
easy to use, easy to install, and does not degrade the performance of the device. 相似文献
5.
M. AHMAD W. AHMAD M. U. RAJPUT A. QAYYUM 《核技术(英文版)》2005,16(6):325-329
The thermal neutron capture gamma ray facility at Pakistan Research Reactor (PARR-1) is being used for the re-estimation of various properties like capture cross-sections, resonance integral, absolute gamma intensities, etc. of different isotopes. The data for gamma ray transitions from the capture of thermal neutrons by ^55Mn are not in good agreement specifically below 2 MeV. So there is a need to re-estimate its intensities with better accuracy. Analytical grade MnCl2 powder and high purity Mn metal pieces were used in this study. Standard ^152Eu and ^60Co radioactive sources as well as thermal neutron capture γ-rays in chlorine were chosen for efficiency calibration. The k0 standardization technique was applied for these measurements to eliminate systematic errors in efficiencies. Chlorine also acted as a comparator in k0-factor calculations. The results have been tabulated for the main gamma rays from ^56Mn in the low as well as in the medium energy regions. The absolute intensities are in good agreement with most of the reported values. 相似文献
6.
Coral reefs exhibit patterns of zonation. In this study we have evaluated the usefulness of Landsat-TM digital data as a tool for discrimination and mapping of reef zones. Classification, on bands 1, 2 and 3, and grouping of classes into reef zones was carried out with the aid of canonical variate analysis and minimum spanning trees. Thirteen reef zones can be identified and mapped, at a spatial scale relevant to their dimensions, with confidence. These zones can be further subdivided and mapped as spatially coherent subzones, in order to provide detailed information regarding the density of coral cover on the reef flat. In addition, the canonical variate analysis provides the basis for the aggregation of classes into sub-zones on interpreted primary productivity gradients, which is of relevance to coral reef management, monitoring and research. 相似文献
7.
Solar energy is an abundant renewable energy resource that can be used to provide high process heat necessary to run thermochemical processes for production of various solar fuels and commodities. In a solar reactor, sunlight is concentrated into a receiver through a small opening called the aperture. However, obtaining and maintaining semiconstant high temperatures inside a solar reactor is a challenge. This is because the incident solar radiation can fluctuate depending on the position of the sun and the weather conditions. For fixed aperture size reactors, changes in incident solar flux directly affect the temperature inside the reactor. This paper presents a novel solar reactor with variable aperture mechanism that is designed and manufactured at our lab. Radiation heat transfer analysis of this reactor concept is studied via Monte Carlo (MC) ray tracing. MC ray tracing module is coupled to a steady-state one-dimensional energy equation solver. Energy equation is solved for the wall and gas, accounting for the absorption, emission, and convection. Incoming direct flux values for a typical day are obtained from National Renewable Energy Lab database. Results show that for a perfectly insulated reactor, the average temperature of the working fluid may be kept appreciably constant throughout the day if aperture diameter is varied between 3 cm and 1.5 cm for incoming fluxes starting with 400 W/m2 at 05:12 a.m., reaching peak value of 981 W/m2 at noon, and eventually receiving 400 W/m2 at 6:58 p.m., which can make the solar reactor run about 13 hr continuously at 1500 K semiconstant temperature. 相似文献
8.
9.
The influence of gas atmosphere packaging (1) 15% CO2, 40% 02, 45% N2; (2) 60% CO2 40% 02 (3) 10% CO2, 5% 02, 85% N2; (4) film overwrap (control) on the microbial growth and succession on steaks was studied during storage. Treatment 3 was most effective in reducing psychrotrophic growth on steaks. Pseudomonas species dominated the microflora for all packaging treatments during early storage. In all gas atmospheres. Serratia liquefaciens increased with storage time and the 10% CO2 atmosphere showed the greatest increase. Enterobacter aerogenes appeared late in the storage period in all atmospheres and Yersinia enterocolitica was isolated after 12 days of storage from steaks in atmosphere 1. 相似文献
10.
Rajesh Shende Senthil Subramanian Shameem Hasan Steven Apperson Rajagopalan Thiruvengadathan Keshab Gangopadhyay Shubhra Gangopadhyay Paul Redner Deepak Kapoor Steven Nicolich Wendy Balas 《Propellants, Explosives, Pyrotechnics》2008,33(2):122-130
This paper reports on the synthesis of the nanoenergetic composites containing CuO nanorods and nanowires, and Al‐nanoparticles. Nanorods and nanowires were synthesized using poly(ethylene glycol) templating method and combined with Al‐nanoparticles using ultrasonic mixing and self‐assembly methods. Poly(4‐vinylpyridine) was used for the self‐assembly of Al‐nanoparticles around the nanorods. At the optimized values of equivalence ratio, sonication time, and Al‐particle size, the combustion wave speed of 1650 m s−1 was obtained for the nanorods‐based energetics. For the composite of nanowires and Al‐nanoparticles the speed was increased to 1900 m s−1. The maximum combustion wave speed of 2400 m s−1 was achieved for the self‐assembled composite, which is the highest known so far among the nanoenergetic materials. It is possible that in the self‐assembled composites, the interfacial contact between the oxidizer and fuel is higher and resistance to overall diffusional process is lower, thus enhancing the performance. 相似文献