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排序方式: 共有4189条查询结果,搜索用时 15 毫秒
991.
王振平 《西安邮电学院学报》2000,5(4):51-53
论述了人口老龄化及养老保障制度的现状 ,讨论了公众普遍关心的热点问题 ,提出解决问题的对策和相关建议。 相似文献
992.
CP树脂砂的常温性能和高温性能等多方面与呋喃树脂砂进行比较,探讨CP树脂砂用于铸钢件生产上的优势;生产证明,该种树脂砂对防止铸钢件裂纹较为有利。 相似文献
993.
珠钢CSP热连轧机张力控制系统分析 总被引:2,自引:2,他引:0
本文从影响热连轧张力控制因素的液压活套传动、测量机理、各种参数的计算方法,控制方法和原理及控制器的构件进行详细分析。 相似文献
994.
The thermal behaviour of a balcony board with integrated glass fibre reinforced plastic (GFRP) elements replacing the compression reinforcement rods, is investigated by means of measurement as well as numerical analysis. For this reason a specimen consisting of an externally insulated brick wall and a representative part of a balcony is tested under a steady state temperature gradient of 30 K in a guarded hot box. Additionally to the normative requirements, temperature sensors are placed on critical sites within the construction, prior to the pouring of cement, to help the verification of the numerical analysis carried out simultaneously. Measured and calculated results are compared and some numerical parameter studies are carried out to quantify the advantage of glass fibre reinforced plastic elements over conventional balcony boards from a thermal point of view. 相似文献
995.
Yuya Mukainakano Kaori Yoshida Kazu Okumura Kimio Kunimori Keiichi Tomishige 《Catalysis Today》2008,132(1-4):101-108
Pd–Ni bimetallic catalysts prepared by co-impregnation and sequential impregnation methods were compared in the catalytic performance in oxidative steam reforming of methane. The sequential impregnation was more effective to the suppression of hot spot formation. According to the structural analysis by in situ quick-scanning X-ray absorption fine structure (QXAFS) during the temperature programmed reduction, the sequential impregnation method gave the bimetallic particles with higher Pd surface composition because of the low possibility of the Pd–Ni bond formation. Higher surface composition of Pd with higher reducibility than Ni is connected to the enhancement of the catalyst reducibility and the suppression of the hot spot formation. 相似文献
996.
997.
Hot flow behavior of boron microalloyed steels 总被引:1,自引:0,他引:1
E. Lpez-Chipres I. Mejía C. Maldonado A. Bedolla-Jacuinde M. El-Wahabi J.M. Cabrera 《Materials Science and Engineering: A》2008,480(1-2):49-55
This research work studies the effect of boron contents on the hot flow behavior of boron microalloyed steels. For this purpose, uniaxial hot-compression tests were carried out in a low carbon steel microalloyed with four different amounts of boron over a wide range of temperatures (950, 1000, 1050 and 1100 °C) and constant true strain rates (10−3, 10−2 and 10−1 s−1). Experimental results revealed that both peak stress and peak strain tend to decrease as boron content increases, which indicates that boron additions have a solid solution softening effect. Likewise, the flow curves show a delaying effect on the kinetics of dynamic recrystallization (DRX) when increasing boron content. Deformed microstructures show a finer austenitic grain size in the steel with higher boron content (grain refinement effect). Results are discussed in terms of boron segregation towards austenitic grain boundaries during plastic deformation, which increases the movement of dislocations, enhances the grain boundary cohesion and modificates the grain boundary structure. 相似文献
998.
The effect of the roof solar reflectance on the thermal performance of a building is often ignored. However, there are significant differences in heat gain from light and dark-coloured roof surfaces. In this paper an equation for the average daily downward heat flow of a sunlit roof is derived. Using building simulation, it is first shown that the thermal mass of the roof does not significantly affect the overall daily heat gain (although it causes a time lag and reduction in peak heat flow). As a consequence the daily heat gain from the roof may be estimated by integrating the equation for the steady-state downward heat transfer over the day. For north Australia the derived equation suggests that a light-coloured roof has about 30% lower total (air temperature difference and solar-driven) heat gain than a dark-coloured one. The effect of aging (change in solar reflectance with time) is considered in the calculations and a relationship between the solar absorptance of new and aged material is suggested. A classification of roof colours with respect to their solar absorptance (dark, medium, light and reflective) is proposed to enable a quick and simple assessment of the effect of roof colour on the heat gain and R-value. 相似文献
999.
An investigation of the potential for natural ventilation and building orientation to achieve thermal comfort in warm and humid climates 总被引:2,自引:0,他引:2
The aim of this study was to analyze the most important factor, the climatic conditions with respect to thermal comfort in buildings. The impact of building location and climate and orientation on thermal comfort were investigated.With the help of dynamic computer simulations the different hourly weather data were analyzed. First of all the climate determines the amount of solar radiation and mean outside temperature that a building is exposed to. The climate also influences the amount of energy that is used for heating and cooling but also the amount of energy that is used for lighting. There is solar excess which determines the amount of solar energy that is unwanted in the building. With growing amounts of glass and a glazing system that allows large solar heat gains,the impact of orientation is substantial. A detailed analysis was conducted to evaluate the potentials for improving thermal comfort. Detailed results are given in sample graphics and tables in the study. In a tropical climate the improvement in comfort by NV range between 9% and 41% (Kuala Lumpur in April). For a subtropical climate the improvements vary between 3% and 14%. In a temperate climate the improvements vary between 8% and 56%. The results showed that NV has a good potential in tropical and temperate climates but not in subtropical climates. Especially in Hong Kong it seems to be very difficult to apply NV. The results showed that in particular in the hottest period (summer) the potential for comfort improvements is rather small. The design of climate responsive building envelopes should take this into consideration. 相似文献
1000.
Microcrystalline silicon carbide (μc-SiC) was prepared at low substrate temperatures using Hot Wire chemical vapor deposition (HWCVD). High crystalline volume fractions were achieved at high hydrogen dilution and high deposition pressure. Without intentional doping, such material shows high dark conductivity and high optical absorption below the band gap. The material prepared at low deposition pressure or low hydrogen dilution, on the other hand, shows much lower conductivity and sub-gap absorption, but high spin densities up to 5 × 1019 cm−3. This high absorption can be attributed to free carriers, different to μc-Si:H where a correlation between the sub-gap absorption and the spin density is observed. 相似文献