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91.
运用飞机专家的知识和经验,模拟飞机专家解决问题的思维方式,建立了用来查找异常原因的智能性程序系统,从而为飞机的故障诊断维修工作提供了一种科学、可行的新方法. 相似文献
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93.
Crossflow instability plays very important role in the transition of the boundary layer on a swept wing, typical in the engineering
applications. Experiments revealed that the linear stability theory well predicted the form of the crossflow vortices, but
usually much overpredicted their growth rate. Using nonlinear theory of hydrodynamic stability, combined with some other considerations,
we were able to obtain the growth rate in good agreement with experimental observations.
The project supported by the National Natural Science Foundation of China, Grant No. 19572048 相似文献
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96.
Azize Akcayoglu 《Experimental Thermal and Fluid Science》2011,35(1):112-120
This paper presents the results of an experimental study of flow structure in horizontal equilateral triangular ducts having double rows of half delta-wing type vortex generators mounted on the duct’s slant surfaces. The test ducts have the same axial length and hydraulic diameter of 4 m and 58.3 mm, respectively. Each duct consists of double rows of half delta wing pairs arranged either in common flow-up or common flow-down configurations. Flow field measurements were performed using a Particle Image Velocimetry Technique for hydraulic diameter based Reynolds numbers in the range of 1000-8000. The secondary flow field differences generated by two different vortex generator configurations were examined in detail. The secondary flow is found stronger behind the second vortex generator pair than behind the first pair but becomes weaker far from the second pair in the case of Duct1. However, the strength of the secondary flow is found nearly the same behind the first and the second vortex generator pair as well as far from the second vortex generator pair in the case of Duct2. Both ducts are able to create a counter-rotating and a second set of twin foci. Duct2 is able to create the second set of twin foci in an earlier streamwise location than Duct1, as these foci are well-known to their heat transfer augmentation. A larger vortex formation area and a greater induced vorticity field between vortex pairs are observed for Duct2 compared with Duct1. As the induced flow field between the vortex pairs increases the heat transfer, and as the flow field between the vortex cores is found larger in the case of Duct2, therefore, it is expected to obtain better heat transfer characteristics for Duct2 compared with Duct1. 相似文献
97.
H. Tran C. Boulet S. Stefani G. Piccioni 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(6):925-936
Precise modelling of infrared absorption by carbon dioxide is of primary importance for radiative transfer calculations in CO2-rich atmospheres like those of Venus and Mars. Despite various measurements and theoretical models dedicated to this subject, accurate data at different temperatures and pressures are still lacking in numerous spectral regions. In this work, using two Fourier Transform Spectrometers, we have measured spectra of pure CO2 in a large spectral region range, from 750 to 8500 cm−1 at various densities (3-57 amagat) and temperatures (230-473 K). Comparisons between measured dipolar absorption bands and spectra calculated with the widely used Lorentz line shape show very large discrepancies. This result is expected since the Lorentz approach neglects line-coupling effects due to intermolecular collisions which transfer absorption from the wings to the band center. In order to account for this effect, a theoretical approach based on the impact and Energy Corrected Sudden approximations has been developed. Comparisons of this model with numerous laboratory spectra in a wide range of pressure, temperature and spectral domain show satisfactory agreements for band centers and near wing regions where the impact approximation is valid. However, as expected, due to the breakdown of the impact approximation, the model fails when considering far wing regions. In the absence of precise models accounting for line-mixing and finite collision duration (non impact) effects, empirical approximations are proposed in order to model the far wings. 相似文献
98.
In this paper, we investigate the role of morphing on flight dynamics of two birds by simulating the flow over rigid and morphing wings that have the characteristics of two different birds, namely the Giant Petrel and Dove Prion. The simulation of a flapping rigid wing shows that the root of the wing should be placed at a specific angle of attack in order to generate enough lift to balance the weight of the bird. However, in this case the generated thrust is either very small, or even negative, depending on the wing shape. Further, results show that morphing of the wing enables a significant increase in the thrust and propulsive efficiency. This indicates that the birds actually utilize some sort of active wing twisting and bending to produce enough thrust. This study should facilitate better guidance for the design of flapping air vehicles. 相似文献
99.
论述了边界元法、有限元法、光滑粒子水动力学法、有限体积法、工程算法与混合分析法在飞行器水上迫降中的应用和发展,总结了不同方法的优缺点,指明了未来的研究重点,为进一步开展水上迫降研究提供参考. 相似文献
100.
This study was carried out on a three-dimensional wing with a freedom in translational direction under a prescribed up and down heaving motion. The investigation focused on how the system kinematics and structural parameters affect the dynamic response of a wing with a relatively small span length. The induced wing motion is a result of the system stability breakdown, which has only been observed by previous researches in the two-dimensional case. The results obtained indicate that the evolution of the wing locomotion is controlled not only by the flapping frequency but also influenced by the system inertia as well as the wing aspect ratio and density ratio. Moreover, initial perturbation effect on wings flexibility plays a role in the evolution development. 相似文献