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41.
An experimental study has been carried out of the low speed Coanda wall jet with both streamwise and axisymmetric curvature. A single component laser Doppler technique was used, and by taking several orientations at a given point, values of the three mean velocities and five of the six Reynolds stresses were obtained. The lateral divergence and convex streamwise curvature both enhanced the turbulence in the outer part of the jet compared with a plane two-dimensional wall jet. The inner layer exhibited a large separation of the positions of maximum velocity and zero shear stress. It was found that the streamwise mean velocity profile became established very rapidly downstream of the slot exit. The profile appeared fairly similar at later downstream positions, but the mean radial velocity and turbulence parameters showed the expected nonself preservation of the flow. Removal of the streamwise curvature resulted in a general return of the jet conditions toward those expected of a plane wall jet. The range and accuracy of the data may be used for developing turbulence models and computational techniques for this type of flow. 相似文献
42.
This second segment of the two‐part paper systematically examines several turbulence models in the context of two flows, namely a vortex flow created by an inclined jet in crossflow, and the flow field in a diffusing S‐shaped duct. The test cases are chosen on the basis of availability of high‐quality and detailed experimental data. The tested turbulence models are integrated to solid surfaces and consist of: Rodi's two‐layer k–ε model, Wilcox's k–ω model, Menter's two‐equation shear–stress‐transport model, and the one‐equation model of Spalart and Allmaras. The objective of the study is to establish the prediction accuracy of these turbulence models with respect to three‐dimensional separated flows with streamline curvature. At the same time, the study establishes the minimum spatial resolution requirements for each of these turbulence closures, and identifies the proper low‐Mach‐number preconditioning and artificial diffusion settings of a Reynolds‐averaged Navier–Stokes algorithm for optimum rate of convergence and minimum adverse impact on prediction accuracy. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
43.
It is argued that the most important test of the understanding of any experiment is whether or not the results are consistent with the equations and boundary conditions believed to govern the flow. If they are not, then either the measurements are incorrect, the equations or boundary conditions are wrong, or the experiment performed was not the one believed to have been done. It is suggested that many apparently contradictory experimental results are, in fact, the result of the latter and have not been recognized as such because of a failure to apply the governing equations to the data. The arguments are supported by examples from turbulent shear flow experiments. 相似文献
44.
Some experiments were made for the buoyant jet from a square orifice with a square disc placed on it in static ambient and concentration along the axis in self-similar area behind disc was measured. And at the same time a three-dimensional mathematical model was established to simulate the whole flowing under different conditions. All the results predicted by the numerical calculation were substantiated by the experiments. The results were compared with experiential formula for obstructed round buoyant vertical jets in static ambient and it was found that the two concentration distributions had good accordance. Star shape of temperature isolines on cross-sections in the near areas from the disc was found and it was a very special figure for obstructed square buoyant vertical jets with a square disc. The shape will transform to concentric circles gradually alike to the round buoyant vertical jet in self-similar area with increasing of the distance from the disc. 相似文献
45.
The characteristics of large coherent structures in turbulent, periodically-excited, as well as naturally-developing bubbly jets are investigated, and interactions between bubbles and large-scale vortices are studied quantitatively. 相似文献
46.
V. G. Pimshtein 《Journal of Applied Mechanics and Technical Physics》2007,48(5):636-640
The velocity of propagation of toroidal and oblique vortices formed in subsonic and supersonic turbulent jets under longitudinal
internal and transverse external excitation by finite-amplitude saw-tooth acoustic waves is studied experimentally. It is
demonstrated that the convection velocity of vortices is not constant, and the character of its variation depends on the vortex
shape.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 5, pp. 21–25, September–October, 2007. 相似文献
47.
近年来,随着高功率激光实验装置的广泛应用,成像技术和模拟分析技术水平的进一步提高,实验室天体物理研究取得了一些新的重要进展,如激光等离子体实验中对流等离子体磁场结构,冲击波中磁场的湍流放大效应,实验室模拟原恒星喷流中磁场的准直效应和太阳风与偶极磁场之间相互作用等方面的研究。这些研究加深了人们对原恒星以及Herbig—Haro天体喷流、超新星遗迹冲击波、地球磁层中磁场活动等天体物理现象的理解。文章对上述几个方向进行了介绍,并对未来研究方向做一些展望。 相似文献
48.
49.
50.
N.
zkan A. St. J. Murphy R. N. Boyd A. L. Cole M. Famiano R. T. Güray M. Howard L.
ahin J. J. ZachR. deHaan J. Grres M. C. WiescherM. S. IslamT. Rauscher 《Nuclear Physics A》2002,710(3-4)
Total cross section measurements for the 102Pd(p, γ)103Ag and 116Sn(p, γ)117Sb reactions have been performed in the proton energy range 2.6 to 4.25 MeV, and for the 112Sn(α, γ)116Te reaction over the alpha beam energy range 7.0 to 10.5 MeV. An activation technique was used in which gamma rays from decays of the reaction products were detected off-line by two hyper-pure germanium detectors in a low background environment. Where possible, reaction rates are derived and the results compared to those of calculations generated by the NON-SMOKER and the MOST statistical model codes so as to judge their applicability for describing the cross sections needed for network calculations of nucleosynthesis in explosive astrophysical environments via the γ- and rp-processes. 相似文献