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111.
建立微小非对称圆环点冲击下拍的理论模型,通过实验验证其有效性。微小非对称圆环是分析大钟拍现象的简化模型,微小非对称圆环的每一对径向振动模态的固有频率非常接近,这对模态互相干涉下出现拍现象。最后利用拍的理论模型绘制沿圆周拍的分布图,详细分析拍的分布特性,为校正钟的拍频声提供理论依据。 相似文献
112.
Guohua Tu Xiaohui Zhao Meiliang Mao Jianqiang Chen Xiaogang Deng Huayong Liu 《International Journal of Computational Fluid Dynamics》2014,28(5):171-186
The construction of Euler fluxes is an important step in shock-capturing/upwind schemes. It is well known that unsuitable fluxes are responsible for many shock anomalies, such as the carbuncle phenomenon. Three kinds of flux vector splittings (FVSs) as well as three kinds of flux difference splittings (FDSs) are evaluated for the shock instability by a fifth-order weighted compact nonlinear scheme. The three FVSs are Steger–Warming splitting, van Leer splitting and kinetic flux vector splitting (KFVS). The three FDSs are Roe's splitting, advection upstream splitting method (AUSM) type splitting and Harten–Lax–van Leer (HLL) type splitting. Numerical results indicate that FVSs and high dissipative FDSs undergo a relative lower risk on the shock instability than that of low dissipative FDSs. However, none of the fluxes evaluated in the present study can entirely avoid the shock instability. Generally, the shock instability may be caused by any of the following factors: low dissipation, high Mach number, unsuitable grid distribution, large grid aspect ratio, and the relative shock-internal flow state (or position) between upstream and downstream shock waves. It comes out that the most important factor is the relative shock-internal state. If the shock-internal state is closer to the downstream state, the computation is at higher susceptibility to the shock instability. Wall-normal grid distribution has a greater influence on the shock instability than wall-azimuthal grid distribution because wall-normal grids directly impact on the shock-internal position. High shock intensity poses a high risk on the shock instability, but its influence is not as much as the shock-internal state. Large grid aspect ratio is also a source of the shock instability. Some results of a second-order scheme and a first-order scheme are also given. The comparison between the high-order scheme and the two low-order schemes indicates that high-order schemes are at a higher risk of the shock instability. Adding an entropy fix is very helpful in suppressing the shock instability for the two low-order schemes. When the high-order scheme is used, the entropy fix still works well for Roe's flux, but its effect on the Steger–Warming flux is trivial and not much clear. 相似文献
113.
In this paper, we study the existence problem of axisymmetricthree-dimensional finger solutions of MullinsSekerkaequation. The finger solutions are travelling wave solutionswhose finger-shaped interfaces are moving along a certain directionat a constant speed within a cylindrical domain. The existenceof at least one axisymmetric three-dimensional finger solutionis obtained through a fixed-point argument of the Hilbert transformation. 相似文献
114.
The Gegenbauer reconstruction method was first proposed in 1992, but in early studies no attempts were made to optimize the relevant parameters of this method. These parameters were allowed to grow proportionally with the number of nodes which, in many cases, resulted in exponential convergence for a selected range of the proportionality constants. Early studies also made clear that very large error bounds could be expected if these key parameters were not chosen carefully. Subsequent studies then pointed out that, although unrelated to the method’s analytically predictable domains of poor accuracy, round-off errors could also sabotage the method’s accuracy. The challenge of successfully implementing a Gegenbauer reconstruction then rests on understanding the performance trade-offs we can expect when choosing the key parameters in accordance with different objectives.In this study, we propose a new strategy for choosing optimal parameters in the Chebyshev-Gegenbauer reconstruction method, specifically to achieve numerical stability. This strategy is based on asymptotic analysis as well as minimization problems in one and two dimensions. The effectiveness of our approach, which could also be applied to a wider selection of polynomials is then illustrated with results from numerical experiments. 相似文献
115.
We study the cutoff phenomenon for generalized riffle shuffles where, at each step, the deck of cards is cut into a random number of packs of multinomial sizes which are then riffled together. © 2007 Wiley Periodicals, Inc. Random Struct. Alg., 2008 相似文献
116.
Michael Bildhauer Martin Fuchs 《Calculus of Variations and Partial Differential Equations》2005,24(3):309-340
We establish several smoothness results for local minimizers of non-autonomous variational integrals with anisotropic growth
conditions.
Mathematics Subject Classification (2000) 49N60, 49N99 相似文献
117.
Scott A. Sarra 《Numerical Algorithms》2006,41(1):17-33
Digital total variation filtering is analyzed as a fast, robust, post-processing method for accelerating the convergence of
pseudospectral approximations that have been contaminated by Gibbs oscillations. The method, which originated in image processing,
can be combined with spectral filters to quickly post-process large data sets with sharp resolution of discontinuities and
with exponential accuracy away from the discontinuities. 相似文献
118.
This paper deals with the Lipschitz regularity of minimizers for a class of variational obstacle problems with possible occurrence of the Lavrentiev phenomenon. In order to overcome this problem, the availment of the notions of relaxed functional and Lavrentiev gap is needed. The main tool used here is a crucial Lemma which reveals to be needed because it allows us to move from the variational obstacle problem to the relaxed-functional-related one. This is fundamental in order to find the solutions’ regularity that we intended to study. We assume the same Sobolev regularity both for the gradient of the obstacle and for the coefficients. 相似文献
119.
120.