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261.
In this study, a high-resolution characteristic-based finite-volume (FV) method on unstructured grids [Int. J. Numer. Method Eng. 50 (2001) 11; Int. J. Heat Fluid Flow 21 (2000) 432] is extended by a matrix-free implicit dual-time stepping scheme for the numerical simulation of steady and unsteady flow and heat transfer with porous media. The method has been used to study the characteristics of a complex problem: flow and heat transfer in a channel with multiple discrete porous blocks, which was originally proposed by Huang and Vafai [J. Thermophys. Heat Transfer 8 (3) (1994) 563]. In addition, flow and heat transfer in a channel partially or fully filled with porous layers and containing solid protruding blocks with constant heat flux on its lower surface are also investigated in details. Hydrodynamic and heat transfer results are reported for both steady and transient flow cases. In particular, the effects of Darcy and Reynolds numbers on heat transfer augmentation and pressure loss are studied. An in-depth discussion of the formation and variation of recirculation is presented and the existence of optimum porous insert is demonstrated. At high Reynolds numbers the flow in the porous channel exhibits a cyclic characteristics although unlike the non-porous channel flow, the cyclic vortex development is only restricted to a small area behind the last solid block, while temperature changes more slowly and does not exhibit cyclic variations over a long period of time. It is shown that for all the cases studied altering some parametric values can have significant and interesting effects on both flow pattern as well as heat transfer characteristics. 相似文献
262.
263.
AUNIFORMLYDIFFERENCESCHEMEOFSINGULARPERTURBATIONPROBLEMFORASEMILINEARORDINARYDIFFERENTIALEQUATIONWITHMIXEDBOUNDARYVALUECONDIT... 相似文献
264.
Based on the successive iteration in the Taylor series expansion method,a three-point explicit compact difference scheme with arbitrary order of accuracy is derived in this paper.Numerical characteristics of the scheme are studied by the Fourier analysis. Unlike the conventional compact difference schemes which need to solve the equation to obtain the unknown derivatives in each node,the proposed scheme is explicit and can achieve arbitrary order of accuracy in space.Application examples for the convection- diffusion problem with a sharp front gradient and the typical lid-driven cavity flow are given.It is found that the proposed compact scheme is not only simple to implement and economical to use,but also is effective to simulate the convection-dominated problem and obtain high-order accurate solution in coarse grid systems. 相似文献
265.
Based on the successive iteration in the Taylor series expansion method, a three-point explicit compact difference scheme with arbitrary order of accuracy is derived in this paper. Numerical characteristics of the scheme are studied by the Fourier analysisl Unlike the conventional compact difference schemes which need to solve the equation to obtain the unknown derivatives in each node, the proposed scheme is explicit and can achieve arbitrary order of accuracy in space. Application examples for the convectiondiffusion problem with a sharp front gradient and the typical lid-driven cavity flow are given. It is found that the proposed compact scheme is not only simple to implement and economical to use, but also is effective to simulate the convection-dominated problem and obtain high-order accurate solution in coarse grid systems. 相似文献
266.
High velocity flows which are exposed to strong rarefaction waves and creating low densities regions in it present difficulties
and inaccuracies for numerical resolution. In particular, variables related to the internal energy are wrongly evaluated.
Use of classical schemes solving the Euler equations in conservative variables introduces significant errors in the determination
of temperature. We recommend to employ a non-conservative formulation of the energy equation. Results found to be more accurate
in using the present internal energy formulation. In order to have the formulation available for both shock and strong rarefaction
waves, we propose a hybrid formulation of conservative and non-conservative ones, depending on a shock indicator. The results
are compared with exact solutions and show a significant improvement of the accuracy. The method is then extended to two-dimensional
cases.
Received 28 March 1997 / Accepted 18 June 1997 相似文献
267.
The interaction of a two-phase flow with a
wedge where a stationary shock wave is initially settled is studied
in a two-dimensional configuration. Before the introduction of
the dispersed phase, the flow around the wedge is a supersonic
one phase flow such as an attached stationary shock wave is
present. Then, the dispersed phase is introduced upstream the
initial position of the stationary shock wave. The purpose of
this study is to point out two-phase and droplets break-up
effects on the oblique shock wave. The two-dimensional
equations are solved by a TVD scheme where fluxes are computed
by using Riemann solver for the gas phase equations and also
for the dispersed phase equations wich is an original approach
due to the authors (Saurel et al. 1994). In addition to drag
forces and heat and mass transfers, the process of droplets
fragmentation based on the particle oscillation is considered.
Accepted April 28, 1995 相似文献
268.
利用NND有限差分格式,发展了一种新的完全隐式的有限体积数值方法,以求解与时间相关的N-S方程.对通过单元体界面的无粘流和粘性流通量均作隐式处理.对绕流钝锥体和不同攻角的气动辅助实验飞行器的高超声速粘性流和化学反应流获得了定常数值解.对流加热率和流场电子密度的计算值与实验数据进行了比较,符合较好,证实了本方法的精确性. 相似文献
269.
The effects of combining functionally graded materials (FGMs) of different inhomogeneous property gradients on the mode-3 propagation characteristics of an interfacial crack are numerically investigated. Spontaneous interfacial crack propagation simulations were performed using the newly developed spectral scheme. The numerical scheme derived and implemented in the present work can efficiently simulate planar crack propagation along functionally graded bimaterial interfaces. The material property inhomogeneity was assumed to be in the direction normal to the interface. Various bimaterial combinations were simulated by varying the material property inhomogeneity length scale. Our parametric study showed that the inclusion of a softening type FGM in the bimaterial system leads to a reduction in the fracture resistance indicated by the increase in crack propagation velocity and power absorbed. An opposite trend of increased fracture resistance was predicted when a hardening material was included in the bimaterial system. The cohesive tractions and crack opening displacements were altered due to the material property inhomogeneity, but the stresses ahead of the cohesive zone remained unaffected. 相似文献
270.
IntroductionThemixingflowfieldresultingfromasonicgaseousinjectioninjectedtransverselyintoasupersonicfreestreamisencounteredinmanyfieldssuchasrocketmotorthrustvectorcontrolsystems,supersoniccombustion ,high_speedflightvehiclereactioncontroljets,andgas_t… 相似文献