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排序方式: 共有361条查询结果,搜索用时 15 毫秒
91.
92.
This study introduced a novel energy saving cooling system, i.e. a combined cycle coupled with a traditional vapor compression cycle with a pumped liquid two-phase cooling cycle. The system has two operation modes, i.e. the compression cycle mode driven by compressor and the pump cycle mode driven by refrigerant pump. A multi-purpose test bench was constructed to experimentally evaluate the performance of the integrated cycle system under various operation conditions. The effects of cycle working condition and the shift temperature between the two operation modes on the overall cycle performance were investigated in detail. It is found that the novel cycle system has a higher EER compared to the traditional compressor system when the ambient temperature is relatively low. The further experimental results and comparative annual energy saving analysis also indicated that the proper shift temperature is about −5 °C from the system EER and cooling capacity point of view. 相似文献
93.
This paper presents a comparative analysis on leakage losses of a rolling piston type rotary compressor with refrigerants of R290, R22 and R410a. In particular, the difference of leakage losses characteristics between R290 compressor and that of other refrigerant compressors has been studied. Leakage losses through radial clearance, clearances between rolling piston faces and the cylinder head walls, clearances between the sliding vane faces and the cylinder head walls, as well as the clearances between the sides of the sliding vane and the side walls of the chutes inside the cylinder have been studied in the present methodology. Radial leakage caused by the wall velocity has been taken into account in the present study. Simulation results indicate that smaller radial clearance is required for R290 compressor to obtain relatively high efficiency comparing to that of R22 and R410a compressors under the same condition. 相似文献
94.
This paper presents a study of refrigerant desorption leading to foam formation in refrigerant-oil mixtures undergoing controlled depressurization. An experimental apparatus was designed and constructed to allow measurements of the depressurization rate, foam height and refrigerant gas mass flux resulting from expansion and desorption from a saturated liquid mixture. Quantitative data and high-speed video analyses were used to identify the main physical mechanisms in the foaming process, namely, bubble cavitation and growth, foam growth and foam decay. The experimental results for the maximum foam height, foam lifetime and liquid supersaturation during desorption were explored as a function of the overall initial refrigerant mass fraction and system temperature. A mathematical model based on integral mass balances was proposed and compared with the experimental data with deviations smaller than 20%. 相似文献
95.
96.
This paper presents experimental results on the shut-down and start-up characteristics of a residential split system R-410A air-conditioner with a capillary tube. During shut-down, the transient characteristics are evaluated by measuring the high and low side pressures and temperatures of the system. The dynamic behavior of the system after start-up is also investigated at the standard cooling capacity rating condition of which the dry and wet bulb temperatures for the indoor and outdoor are 27/19.5 and 35/24°C, respectively. All experiments are performed in a psychrometric calorimeter. The cooling capacity, power consumption, dehumidification capacity and cycle characteristics after start-up are analyzed. The test results show that the cooling capacity and the coefficient of performance (COP) after start-up can be expressed as the combination of two exponential functions of time, approaching the cooling capacity of steady-state. 相似文献
97.
This paper addresses the problem of absorption of refrigerant vapor in a stagnant layer of lubricant oil. The bulk motion of the solute is described in terms of apparent diffusion coefficients that encompass both molecular diffusion and possible macroscopic motion induced by liquid density instability and surface tension. In absorption of refrigerant mixtures, diffusion in the vapor and liquid phases are coupled with a thermodynamic model for interfacial equilibrium. Results are compared with experimental data available in the literature for absorption of several refrigerants in polyol ester oil (POE68). The adequacy of the formulation is assessed in the light of its basic assumptions and performance of the model. 相似文献
98.
Eduardo Navarro de Andrade Eric Skowron Victor W. Goldschmidt Eckhard A. Groll 《International Journal of Refrigeration》1999,22(6):499
The concentration of oil in refrigerants (while in liquid state) can be measured with an acoustic velocity sensor. The transit time for an acoustic signal can be related to the oil concentration and temperature of the liquid mixture. The performance of the sensor is dependent on the properties of the oil and refrigerant, and their miscibility. In general, a thorough calibration becomes necessary. It is shown in this paper that for concentrations less than 10%, an approximation can be made for the estimate of concentration hence eliminating the need for an elaborate calibration procedure. 相似文献
99.
基于Java3D的虚拟现实建模方法 总被引:13,自引:1,他引:13
当前的虚拟现实建模主要用OpenGL,VRML等语言,分别存在着难以掌握学习、不易 控制等缺点。给出了一种基于Java3D构建方法,即用Java3D描述虚拟物体的几何和物理 特征,充分利用Java语言的面向对象的特征和初学者易学易用的特点来构造虚拟现实场 景。 相似文献
100.
A practical representation for the transport coefficients of pure refrigerants R32, R125, R134a, and R125+R32 mixtures is presented which is valid in the vapor–liquid critical region. The crossover expressions for the transport coefficients incorporate scaling laws near the critical point and are transformed to regular background values far away from the critical point. The regular background parts of the transport coefficients of pure refrigerants are obtained from independently fitting pure fluid data. For the calculation of the background contributions of the transport coefficients in binary mixtures, corresponding-states correlations are used. The transport property model is compared with thermal conductivity and thermal diffusivity data for pure refrigerants, and with thermal conductivity data for R125+R32 mixtures. The average relative deviations between the calculated values of the thermal conductivity and experimental data are less than 4–5% at densities ρ0.1ρc and temperatures up to T=2Tc. 相似文献