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241.
Experimental investigation and simulation of flow boiling of nanofluids in different flow directions
In this work, the flow boiling of TiO2/water and Al2O3/water nanofluids was investigated experimentally and simulated with two phases. Experimental results were obtained in two directions and compared together. The volume fraction and heat transfer coefficient obtained from the vertical tube were compared with those obtained from the horizontal tube. The results showed that the contours of vapor volume fraction in horizontal tube are completely different from the vertical tube, which is due to the buoyancy effect. Moreover, the effect of nanoparticles on both flow directions was almost the same, while heat transfer coefficient was not the same in these flow directions. Based on the experimental result, presence of nanoparticles in the base fluid cannot increase the heat transfer coefficient. 相似文献
242.
对EAST装置偏滤器位形的放电中发生的垂直位移不稳定性的全过程进行了模拟,计算了磁轴垂直位移及垂直位移不稳定性的增长率。模拟的结果与实验结果符合得较好。 相似文献
243.
244.
基于等离子体参数随大半径/小半径变化的规律,分析了电流平顶段垂直磁场与相关等离子体参数的关系。垂直磁场的非线性部分用于分析非感应电流驱动效应,包括自举电流效应。此外,对于给定的等离子体电流,推导了平顶段垂直磁场与线平均密度之间的关系,并进一步研究压缩后的等离子体。基于EAST第41195次放电的数据分析表明,垂直磁场强度的增大可以使得等离子体温度、密度、βp和自举电流份额获得提升,为等离子体参数高参数,特别是βp提供了一种可能性参考。 相似文献
245.
A theoretical study on vertical finite cracks detection in low carbon steel (A36) blocks using pulsed laser spot thermography (PLST) was carried out in this paper. The basic principle of PLST was described. The 3D heat conduction model of flux transfer under pulsed laser spot excitation was established and calculated using finite element method (FEM). The effect of laser-crack distance to temperature abrupt jump across the vertical finite cracks was analyzed, and results show that the optimum laser-crack distance is the radius of laser spot. The relationship between geometric parameters of cracks and temperature abrupt jump was studied, and results show larger geometric size of cracks leads to greater peak values of temperature abrupt jump, and tends to stable values at certain size. 相似文献
246.
An e-epidemic model of malicious codes in the computer network through vertical transmission is formulated. We have observed that if the basic reproduction number is less than unity, the infected proportion of computer nodes disappear and malicious codes die out and also the malicious codes-free equilibrium is globally asymptotically stable which leads to its eradication. Effect of anti-virus software on the removal of the malicious codes from the computer network is critically analyzed. Analysis and simulation results show some managerial insights that are helpful for the practice of anti-virus in information sharing networks. 相似文献
247.
248.
This letter presents the design, simulation, fabrication, and successful demonstration of a variable optical attenuator (VOA) based on a micromachined micromirror combined with an optical fiber collimator. The micromirror has a size of 500 μm in diameter and a rotational resonance of 4.94 kHz. The micromirror was actuated by vertical comb drive which was fabricated by bulk micromachining process on a silicon on insulator (SOI) wafer. The VOA operates at a low driving voltage of 4.4 V corresponding to the rotation angle of 0.3°. The turn-on and turn-off response time of the VOA are 1.6 ms and 2.74 ms, respectively. Finally, the optical attenuation was measured and an optical attenuation as large as 40 dB was obtained. 相似文献
249.
Gabriel Pérez Julià Coma Camila Barreneche Alvaro de Gracia Miguel Urrestarazu Silvia Burés Luisa F. Cabeza 《Applied Acoustics》2016
Vertical Greenery Systems (VGS) are promising contemporary Green Infrastructure which contribute to the provision of several ecosystem services both at building and urban scales. Among others, the building acoustic insulation and the urban noise reduction could be considered. Traditionally vegetation has been used to acoustically insulate urban areas, especially from the traffic noise. Now, with the introduction of vegetation in buildings, through the VGS, it is necessary to provide experimental data on its operation as acoustic insulation tool in the built environment. In this study the acoustic insulation capacity of two VGS was conducted through in situ measurements according to the UNE-EN ISO 140-5 standard. From the results, it was observed that a thin layer of vegetation (20–30 cm) was able to provide an increase in the sound insulation of 1 dB for traffic noise (in both cases, Green Wall and Green Facade), and an insulation increase between 2 dB (Green Wall) and 3 dB (Green Facade) for a pink noise. In addition to the vegetation contribution to sound insulation, the influence of other factors such as the mass factor (thickness, density and composition of the substrate layer) and type of modular unit of cultivation, the impenetrability (sealing joints between modules) and structural insulation (support structure) must be taken into account for further studies. 相似文献
250.
In consideration of the complexity and the high cost of the dual CCD intersection vertical target when it is used indoor. A novel measuring principle of one linear array CCD camera vertical target is presented. One low-power semiconductor sector-like laser with projection board is used to be the lamp-house of the CCD camera. The detection light screen of the CCD camera and the laser lamp-house are adjusted to same plane. When the projectile through the detection light screen, it blocks the part light of the laser and leaves a shadow of projectile on the board. The shadow and its coordinate are acquired and calculated by the CCD camera and computer, and the projectile coordinate of X and Y can be gotten through image processing and further calculation. The measuring principle and the formulas are given, and the measuring error is analyzed. The result indicates that the coordinate error of X and Y less than 1.5 and 2.2 mm, respectively, when the detection light screens is 1 m × 1 m, The principle presented has the advantages that measurement principle is simple, low cost and easy engineering. 相似文献