全文获取类型
收费全文 | 1089篇 |
免费 | 60篇 |
国内免费 | 55篇 |
专业分类
化学 | 52篇 |
力学 | 260篇 |
综合类 | 4篇 |
数学 | 742篇 |
物理学 | 146篇 |
出版年
2024年 | 2篇 |
2023年 | 13篇 |
2022年 | 4篇 |
2021年 | 10篇 |
2020年 | 16篇 |
2019年 | 27篇 |
2018年 | 20篇 |
2017年 | 25篇 |
2016年 | 22篇 |
2015年 | 30篇 |
2014年 | 47篇 |
2013年 | 96篇 |
2012年 | 27篇 |
2011年 | 74篇 |
2010年 | 66篇 |
2009年 | 66篇 |
2008年 | 77篇 |
2007年 | 57篇 |
2006年 | 64篇 |
2005年 | 60篇 |
2004年 | 47篇 |
2003年 | 58篇 |
2002年 | 46篇 |
2001年 | 35篇 |
2000年 | 31篇 |
1999年 | 33篇 |
1998年 | 34篇 |
1997年 | 27篇 |
1996年 | 22篇 |
1995年 | 12篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 6篇 |
1985年 | 7篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有1204条查询结果,搜索用时 31 毫秒
991.
K. C. Patidar 《Journal of Difference Equations and Applications》2016,22(6):817-849
In this paper, we review many recent developments and further applications of nonstandard finite difference (NSFD) methods encountered in the past decade. In particular, it is a follow up article of the one published in 2005 [K.C. Patidar, On the use of non-standard finite difference methods, J. Differ. Equ. Appl. 11 (2005), pp. 735–758]. It also includes those research contributions in this field that are very significant and published prior to the above article but were not included in the above paper simply because we did not have access to them when we wrote the above article. We also give a detailed account on various definitions/notions of NSFD methods appeared in the literature in past two decades. All contributions are listed chronologically except that in some instances we have grouped certain works to show connectivity in those fields. While categorizing these research contributions, we considered a number of different application areas. Moreover, due to space limitations, firstly, we have not included all works that used NSFD methodology but certainly important contributions are given due consideration, and secondly, we have only included the salient features of the proposed numerical schemes for many of these contributions and ignored other contents where the involved approaches sound fairly standard thus implying why these methods are known robust. Of course, the cases when there is a specific variation, in the theoretical analysis of these NSFD schemes, are highlighted with more details. 相似文献
992.
讨论了四阶强阻尼非线性波动方程的Hermite型混合有限元方法,并证明了半离散格式下解的存在唯一性.基于该元积分恒等式结果,利用插值与Ritz投影之间的误差估计,可得到半离散格式下O(h~3)阶的超逼近性质,再借助于插值后处理技术导出整体超收敛.进而,通过构造一个新的金离散格式,得到了O(h~3+τ~2)的超逼近和超收敛结果. 相似文献
993.
Zhi Lan Wang 《数学学报(英文版)》2016,32(8):901-910
We propose a conjecture on the generating series of Chern numbers of tautological bundles on symmetric products of curves and establish the rank 1 and rank -1 case of this conjecture. Thus we compute explicitly the generating series of integrals of Segre classes of tautological bundles of line bundles on curves, which has a similar structure as Lehn's conjecture for surfaces. 相似文献
994.
Let (X, G) be an association scheme. We say that (X, G) is flat if it is homogeneous and if any two distinct points have at most one common g-neighbor for each g ∈ G. In this paper we prove that any nondiscrete equitable partition of (X, G) has at most one singleton if (X, G) is flat, and {X} is the unique equitable partition without any singleton if (X, G) is flat and |X| is a prime.
This work was supported for two years by Korea Research Foundation Grant (KRF-2006-003-C00010) and Pusan National University
Research Grant.
Received: January 31, 2007. Final version received: Novmeber 14, 2007. 相似文献
995.
Hermano Frid 《Bulletin of the Brazilian Mathematical Society》2008,39(3):315-340
Let be a separable Hilbert space, an open convex subset, and f: a smooth map. Let Ω be an open convex set in with , where denotes the closure of Ω in . We consider the following questions. First, in case f is Lipschitz, find sufficient conditions such that for ɛ > 0 sufficiently small, depending only on Lip(f), the image of Ω by I + ɛf, (I + ɛf)(Ω), is convex. Second, suppose df(u): is symmetrizable with σ(df(u)) ⊆ (0,∞), for all u ∈ , where σ(df(u)) denotes the spectrum of df(u). Find sufficient conditions so that the image f(Ω) is convex. We establish results addressing both questions illustrating our assumptions and results with simple examples.
We also show how our first main result immediately apply to provide an invariance principle for finite difference schemes
for nonlinear ordinary differential equations in Hilbert spaces. The main application of the theory developed in this paper
concerns our second result and provides an invariance principle for certain convex sets in an L
2-space under the flow of a class of kinetic transport equations so called BGK model.
相似文献
996.
In this paper we investigate the L2-solutions of vector refinement equations with exponentially decaying masks and a general dilation matrix. A vector refinement equation with a general dilation matrix and exponentially decaying masks is of the formwhere the vector of functions φ=(φ1,…,φr)T is in is an exponentially decaying sequence of r×r matrices called refinement mask and M is an s×s integer matrix such that limn→∞M-n=0. Associated with the mask a and dilation matrix M is a linear operator Qa on given byThe iterative scheme is called vector subdivision scheme or vector cascade algorithm. The purpose of this paper is to provide a necessary and sufficient condition to guarantee the sequence to converge in L2-norm. As an application, we also characterize biorthogonal multiple refinable functions, which extends some main results in [B. Han, R.Q. Jia, Characterization of Riesz bases of wavelets generated from multiresolution analysis, Appl. Comput. Harmon. Anal., to appear] and [R.Q. Jia, Convergence of vector subdivision schemes and construction of biorthogonal multiple wavelets, Advances in Wavelet (Hong Kong, 1997), Springer, Singapore, 1998, pp. 199–227] to the general setting. 相似文献
997.
998.
Electronic Structures of Organometallic Complexes of f Elements. 67 First Parametric Analysis of the Absorption Spectrum of a Molecular Compound of CeIIIμ: Tris(η5‐tetramethylcyclopentadienyl)cerium(III) The absorption spectra (in the IR/NIR/Vis/UV range) of Ce(C5Me4H)3 ( 1 ) and La(C5Me4H)3 ( 2 ) were recorded at room and low temperatures. From the spectra obtained, two alternative closely related crystal field (CF) splitting patterns of 1 could be derived, and simulated by fitting the free parameters of a phenomenological Hamiltonian. The fact that the difference of the experimental energies of the barycenters of CF levels of the multiplets 2F7/2 and 2F5/2 is larger than in the gaseous free Ce3+ ion (“anti”‐relativistic nephelauxetic effect) could be explained by coupling effects of these multiplets via the CF, resulting in lower spin‐orbit coupling parameters than in the case of the gaseous free Ce3+ ion. The experimentally derived CF splitting pattern of 1 is compared with the predictions of previous non‐relativistic SW‐Xα and relativistic DV‐Xα calculations. 相似文献
999.
We prove the convergence, up to a subsequence, of the spatial semidiscrete scheme for the one-dimensional Perona-Malik equation ut=(?′x(ux)), , when the initial datum is 1-Lipschitz out of a finite number of jump points, and we characterize the problem satisfied by the limit solution. In the more difficult case when has a whole interval where is negative, we construct a solution by a careful inspection of the behaviour of the approximating solutions in a space-time neighbourhood of the jump points. The limit solution u we obtain is the same as the one obtained by replacing ?(⋅) with the truncated function min(?(⋅),1), and it turns out that u solves a free boundary problem. The free boundary consists of the points dividing the region where |ux|>1 from the region where |ux|?1. Finally, we consider the full space-time discretization (implicit in time) of the Perona-Malik equation, and we show that, if the time step is small with respect to the spatial grid h, then the limit is the same as the one obtained with the spatial semidiscrete scheme. On the other hand, if the time step is large with respect to h, then the limit solution equals , i.e., the standing solution of the convexified problem. 相似文献
1000.
In the high frequency regime, the geometrical-optics approximation for the Helmholtz equation with a point source results in an Eikonal equation for traveltime and a transport equation for amplitude. Because the point-source traveltime field has an upwind singularity at the source point, all formally high-order finite-difference Eikonal solvers exhibit first-order convergence and relatively large errors. In this paper, we propose to first factor out the singularities of traveltimes, takeoff angles, and amplitudes, and then we design high-order Lax–Friedrichs sweeping schemes for point-source traveltimes, takeoff angles, and amplitudes. Numerical examples are presented to demonstrate the performance of our new method. 相似文献