全文获取类型
收费全文 | 9177篇 |
免费 | 966篇 |
国内免费 | 697篇 |
专业分类
化学 | 285篇 |
晶体学 | 9篇 |
力学 | 817篇 |
综合类 | 193篇 |
数学 | 7988篇 |
物理学 | 1548篇 |
出版年
2024年 | 6篇 |
2023年 | 88篇 |
2022年 | 100篇 |
2021年 | 152篇 |
2020年 | 247篇 |
2019年 | 242篇 |
2018年 | 240篇 |
2017年 | 285篇 |
2016年 | 307篇 |
2015年 | 205篇 |
2014年 | 462篇 |
2013年 | 952篇 |
2012年 | 439篇 |
2011年 | 572篇 |
2010年 | 506篇 |
2009年 | 617篇 |
2008年 | 644篇 |
2007年 | 629篇 |
2006年 | 547篇 |
2005年 | 486篇 |
2004年 | 390篇 |
2003年 | 384篇 |
2002年 | 358篇 |
2001年 | 275篇 |
2000年 | 272篇 |
1999年 | 254篇 |
1998年 | 220篇 |
1997年 | 158篇 |
1996年 | 147篇 |
1995年 | 100篇 |
1994年 | 93篇 |
1993年 | 67篇 |
1992年 | 69篇 |
1991年 | 70篇 |
1990年 | 39篇 |
1989年 | 19篇 |
1988年 | 17篇 |
1987年 | 19篇 |
1986年 | 13篇 |
1985年 | 25篇 |
1984年 | 20篇 |
1983年 | 12篇 |
1982年 | 16篇 |
1981年 | 18篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1978年 | 11篇 |
1977年 | 7篇 |
1976年 | 10篇 |
1936年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
1.
通过引入参数,构造了一个全平面上的、含双曲函数的非齐次核函数。利用正切函数的有理分式展开,建立了最佳常数因子与正切函数高阶导数相关联的Hilbert型积分不等式。 作为应用,通过赋予参数不同的值,建立了一些有意义的特殊结果。 相似文献
2.
In this work, we present and analyze a mathematical model for tumor growth incorporating ECM erosion, interstitial flow, and the effect of vascular flow and nutrient transport. The model is of phase-field or diffused-interface type in which multiple phases of cell species and other constituents are separated by smooth evolving interfaces. The model involves a mesoscale version of Darcy’s law to capture the flow mechanism in the tissue matrix. Modeling flow and transport processes in the vasculature supplying the healthy and cancerous tissue, one-dimensional (1D) equations are considered. Since the models governing the transport and flow processes are defined together with cell species models on a three-dimensional (3D) domain, we obtain a 3D–1D coupled model. 相似文献
3.
Marcus Carlsson 《Expositiones Mathematicae》2021,39(1):149-157
von Neumann’s inequality in matrix theory refers to the fact that the Frobenius scalar product of two matrices is less than or equal to the scalar product of the respective singular values. Moreover, equality can only happen if the two matrices share a joint set of singular vectors, and this latter part is hard to find in the literature. We extend these facts to the separable Hilbert space setting, and provide a self-contained proof of the “latter part”. 相似文献
4.
5.
6.
《Discrete Mathematics》2021,344(12):112589
Let be the set of positive integers. For a nonempty set A of integers and every integer u, denote by the number of with such that . For a sequence S of positive integers, let be the counting function of S. The set is called a perfect difference set if for every positive integer u. In 2008, Cilleruelo and Nathanson (2008) [4] constructed dense perfect difference sets from dense Sidon sets. In this paper, as a main result, we prove that: let be an increasing function satisfying for any positive integer n, then for every Sidon set B and every function , there exists a set such that for every positive integer u and for all . 相似文献
7.
本文在Sobolev-Lorentz空间W2L2,q(R4)的范数约束下得到了一个最佳的二阶次临界型Adams不等式.进一步,当次临界指标逼近最佳常数时,得到了Adams泛函的上、下界的估计.本文主要采用了Lam和Lu[A new approach to sharp MoserTrudinger and Adams type inequalities:a rearrangement-free argument,J.Diff Equ.,2013,255(3):298-325]的分割水平集方法. 相似文献
8.
《Discrete Mathematics》2020,343(4):111696
For a set the -neighbourhood of is , where denotes the usual graph distance on . Harper’s vertex-isoperimetric theorem states that among the subsets of given size, the size of the -neighbourhood is minimised when is taken to be an initial segment of the simplicial order. Aubrun and Szarek asked the following question: if is a subset of given size for which the sizes of both and are minimal for all , does it follow that is isomorphic to an initial segment of the simplicial order?Our aim is to give a counterexample. Surprisingly it turns out that there is no counterexample that is a Hamming ball, meaning a set that lies between two consecutive exact Hamming balls, i.e. a set with for some . We go further to classify all the sets for which the sizes of both and are minimal for all among the subsets of of given size. We also prove that, perhaps surprisingly, if for which the sizes of and are minimal among the subsets of of given size, then the sizes of both and are also minimal for all among the subsets of of given size. Hence the same classification also holds when we only require and to have minimal size among the subsets of given size. 相似文献
9.
In this article, we have developed an overlapping Schwarz method for a weakly coupled system of convection-diffusion equations. The method splits the original domain into two overlapping subdomains. A hybrid difference scheme is proposed in which on the boundary layer region, we use the central finite difference scheme on a uniform mesh, whereas on the nonlayer region, we use the mid-point difference scheme on a uniform mesh. It is shown that the numerical approximations converge in the maximum norm to the exact solution. We have proved that, when appropriate subdomains are used, the method produces almost second-order convergence. Furthermore, it is shown that two iterations are sufficient to achieve the expected accuracy. Numerical examples are presented to support the theoretical results. The main advantage of this method used with the proposed scheme is that it reduces iteration counts very much and easily identifies in which iteration the Schwarz iterate terminates. 相似文献
10.
Yuhua Long 《Journal of Difference Equations and Applications》2020,26(7):966-986
In the present paper, we apply the method of invariant sets of descending flow to establish a series of criteria to ensure that a second-order nonlinear functional difference equation with periodic boundary conditions possesses at least one trivial solution and three nontrivial solutions. These nontrivial solutions consist of sign-changing solutions, positive solutions and negative solutions. Moreover, as an application of our theoretical results, an example is elaborated. Our results generalize and improve some existing ones. 相似文献