全文获取类型
收费全文 | 175篇 |
免费 | 12篇 |
国内免费 | 8篇 |
专业分类
化学 | 109篇 |
力学 | 6篇 |
数学 | 50篇 |
物理学 | 30篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 2篇 |
2014年 | 8篇 |
2013年 | 18篇 |
2012年 | 11篇 |
2011年 | 15篇 |
2010年 | 14篇 |
2009年 | 10篇 |
2008年 | 18篇 |
2007年 | 13篇 |
2006年 | 8篇 |
2005年 | 4篇 |
2004年 | 7篇 |
2003年 | 9篇 |
2002年 | 7篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1980年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有195条查询结果,搜索用时 0 毫秒
131.
The cell rotation graph D(G) on the strongly connected orientations of a 2-edge-connected plane graph G is defined. It is shown that D(G) is a directed forest and every component is an in-tree with one root; if T is a component of D(G), the reversions of all orientations in T induce a component of D(G), denoted by T−, thus (T,T−) is called a pair of in-trees of D(G); G is Eulerian if and only if D(G) has an odd number of components (all Eulerian orientations of G induce the same component of D(G)); the width and height of T are equal to that of T−, respectively. Further it is shown that the pair of directed tree structures on the perfect matchings of a plane elementary bipartite graph G coincide with a pair of in-trees of D(G). Accordingly, such a pair of in-trees on the perfect matchings of any plane bipartite graph have the same width and height. 相似文献
132.
The Wiener index of a connected graph (molecule graph) G is the sum of the distances between all pairs of vertices of G, which was reported by Wiener in 1947 and is the oldest topological index related to molecular branching. In this paper, simple formulae of the expected value of the Wiener index in a random polygonal chain and the asymptotic behavior of this expectation are established by solving a difference equation. Based on the results above, we obtain the average value of the Wiener index of all polygonal chains with n polygons. As applications, we use the unified formulae to obtain the expected values of the Wiener indices of some special random polygonal chains which were deeply discussed in the context of organic chemistry or statistical physics. 相似文献
133.
The algebraic connectivity of a graph G is the second smallest eigenvalue of its Laplacian matrix. Let ■n be the set of all trees of order n. In this paper, we will provide the ordering of trees in ■n up to the last eight trees according to their smallest algebraic connectivities when n ≥ 13. This extends the result of Shao et al. [The ordering of trees and connected graphs by algebraic connectivity. Linear Algebra Appl., 428, 1421-1438 (2008)]. 相似文献
134.
Khoshnevisan Davar Kim Kunwoo Mueller Carl Shiu Shang-Yuan 《Journal of statistical physics》2020,179(2):502-534
Journal of Statistical Physics - The study of intermittency for the parabolic Anderson problem usually focuses on the moments of the solution which can describe the high peaks in the probability... 相似文献
135.
136.
137.
This paper presents an analysis of the coupled vibration of asymmetric core structures in tall buildings. The governing equation
of free vibration and its corresponding eigenvalue problem, which is a set of equations for laterally flexural vibrations
in two different directions coupled by a warping-St. Venant torsional vibration, are derived. Based on the Calerkin method,
a generalized approximate method is developed for the analysis of coupled vibration and thus proposed for determining the
natural frequencies and mode shapes of the structure in triply-coupled vibration. The results of the proposed method for the
example structure show good agreement with those of the FEM analysis. The proposed method has been shown to provide a simple
and rapid, yet accurate, means for coupled vibration analysis of core structures. 相似文献
138.
Parallel domain decomposition method for finite element approximation of 3D steady state non‐Newtonian fluids 下载免费PDF全文
We introduce a stabilized finite element method for the 3D non‐Newtonian Navier–Stokes equations and a parallel domain decomposition method for solving the sparse system of nonlinear equations arising from the discretization. Non‐Newtonian flow problems are, generally speaking, more challenging than Newtonian flows because the nonlinearities are not only in the convection term but also in the viscosity term, which depends on the shear rate. Many good iterative methods and preconditioning techniques that work well for the Newtonian flows do not work well for the non‐Newtonian flows. We employ a Galerkin/least squares finite element method, with stabilization parameters adjusted to count the non‐Newtonian effect, to discretize the equations, and the resulting highly nonlinear system of equations is solved by a Newton–Krylov–Schwarz algorithm. In this study, we apply the proposed method to some inelastic power‐law fluid flows through the eccentric annuli with inner cylinder rotation and investigate the robustness of the method with respect to some physical parameters, including the power‐law index and the Reynolds number ratios. We then report the superlinear speedup achieved by the domain decomposition algorithm on a computer with up to 512 processors. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
139.
A complete cubic Halin graph is a cubic Halin graph whose characteristic tree is a complete cubic tree, in which all leaves are at the same distance from the root vertex. In this work, we determine the strong chromatic index of the complete cubic Halin graph. 相似文献
140.
The paper studies a discrete counterpart of Gerber et al. (2006). The surplus of an insurance company (before dividends) is modeled as a time-homogeneous Markov chain with possible changes of size +1,0,−1,−2,−3,…. If a barrier strategy is applied for paying dividends, it is shown that the dividends-penalty identity holds. The identity expresses the expected present value of a penalty at ruin in terms of the expected discounted dividends until ruin and the expected present value of the penalty at ruin if no dividends are paid. For the problem of maximizing the difference between the expected discounted dividends until ruin and the expected present value of the penalty at ruin, barrier strategies play a prominent role. In some cases an optimal dividend barrier exists. The paper discusses in detail the special case where the distribution of the change in surplus does not depend on the current surplus (so that in the absence of dividends the surplus process has independent increments). A closed-form result for zero initial surplus is given, and it is shown how the relevant quantities can be calculated recursively. Finally, it is shown how optimal dividend strategies can be determined; typically, they are band strategies. 相似文献