全文获取类型
收费全文 | 3505篇 |
免费 | 575篇 |
国内免费 | 380篇 |
专业分类
化学 | 329篇 |
晶体学 | 12篇 |
力学 | 633篇 |
综合类 | 47篇 |
数学 | 2399篇 |
物理学 | 1040篇 |
出版年
2024年 | 23篇 |
2023年 | 57篇 |
2022年 | 92篇 |
2021年 | 110篇 |
2020年 | 101篇 |
2019年 | 94篇 |
2018年 | 128篇 |
2017年 | 145篇 |
2016年 | 183篇 |
2015年 | 110篇 |
2014年 | 158篇 |
2013年 | 327篇 |
2012年 | 209篇 |
2011年 | 215篇 |
2010年 | 184篇 |
2009年 | 225篇 |
2008年 | 171篇 |
2007年 | 202篇 |
2006年 | 165篇 |
2005年 | 156篇 |
2004年 | 153篇 |
2003年 | 132篇 |
2002年 | 126篇 |
2001年 | 106篇 |
2000年 | 123篇 |
1999年 | 112篇 |
1998年 | 76篇 |
1997年 | 84篇 |
1996年 | 52篇 |
1995年 | 54篇 |
1994年 | 46篇 |
1993年 | 56篇 |
1992年 | 46篇 |
1991年 | 39篇 |
1990年 | 25篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 12篇 |
1986年 | 16篇 |
1985年 | 19篇 |
1984年 | 16篇 |
1983年 | 8篇 |
1982年 | 20篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1973年 | 2篇 |
排序方式: 共有4460条查询结果,搜索用时 62 毫秒
1.
2.
Rong Yin Jihui Zhang Xudong Shang 《Mathematical Methods in the Applied Sciences》2020,43(15):8736-8752
This paper is dedicated to studying the following Schrödinger–Poisson system Under some different assumptions on functions V(x), K(x), a(x) and f(u), by using the variational approach, we establish the existence of positive ground state solutions. 相似文献
3.
In this paper, we investigate the evolution of joint invariants under invariant geometric flows using the theory of equivariant moving frames and the induced invariant discrete variational complex. For certain arc length preserving planar curve flows invariant under the special Euclidean group , the special linear group , and the semidirect group , we find that the induced evolution of the discrete curvature satisfies the differential‐difference mKdV, KdV, and Burgers' equations, respectively. These three equations are completely integrable, and we show that a recursion operator can be constructed by precomposing the characteristic operator of the curvature by a certain invariant difference operator. Finally, we derive the constraint for the integrability of the discrete curvature evolution to lift to the evolution of the discrete curve itself. 相似文献
4.
Johannes Elschner Rainer Hinder Gunther Schmidt 《Advances in Computational Mathematics》2002,16(2-3):139-156
This paper is devoted to the numerical study of diffraction by periodic structures of plane waves under oblique incidence. For this situation Maxwell's equations can be reduced to a system of two Helmholtz equations in R
2 coupled via quasiperiodic transmission conditions on the piecewise smooth interfaces between different materials. The numerical analysis is based on a strongly elliptic variational formulation of the differential problem in a bounded periodic cell involving nonlocal boundary operators. We obtain existence and uniqueness results for discrete solutions and provide the corresponding error analysis. 相似文献
5.
An applied cell mapping method for optimal control problems 总被引:1,自引:0,他引:1
W. H. Zhu 《Journal of Optimization Theory and Applications》1989,60(3):485-500
From the application point of view, a series of modifications are proposed for the cell mapping method discussed in Ref. 1 for the optimal control analysis of dynamical systems. The cell order around the target set is rearranged. A set of common discriminate principles is used for the selection of the optimal one among competing control strategies of the same cost. Inequality constraints of the system are taken into account. The number of elements in the set of allowable time intervals is not prescribed, but left open. These modifications seem to make the cell mapping method more efficient for analyzing feedback systems and for obtaining their global optimal control information. The algorithms presented in this paper could broaden the application of the cell mapping approach of Ref. 1 to a wider class of engineering problems. 相似文献
6.
Equilibrium Problems with Applications to Eigenvalue Problems 总被引:5,自引:0,他引:5
In this paper, we consider equilibrium problems and introduce the concept of (S)+ condition for bifunctions. Existence results for equilibrium problems with the (S)+ condition are derived. As special cases, we obtain several existence results for the generalized nonlinear variational inequality studied by Ding and Tarafdar (Ref. 1) and the generalized variational inequality studied by Cubiotti and Yao (Ref. 2). Finally, applications to a class of eigenvalue problems are given. 相似文献
7.
We consider a useful modification of the inexact implicit method with a variable parameter in Wang et al. J Optim Theory 111:
431–443 (2001) for generalized mixed monotone variational inequalities. One of the contributions of the proposed method in
this paper is that the restrictions imposed on the variable parameter are weaker than the ones in Wang et al. J Optim Theory
111: 431–443 (2001). Another contribution is that we establish a sufficient and necessary condition for the convergence of
the proposed method to a solution of the general mixed monotone variational inequality. 相似文献
8.
A localH-theorem is derived for a recently proposed extension of Enskog kinetic theory to a dense model fluid composed of particles with interactions extending beyond a hard core.On leave from: Katedra Fizyki, Uniwersytetu Szczecinskiego, 70-451 Szczecin, Poland. 相似文献
9.
The finite-difference method is a numerical technique for obtaining approximate solutions to differential equations. The main
objective of the present study is to give a new aspect to the finite-difference method by using a variational derivative.
By applying this formulation, accurate values of the buckling loads of beams and frames with various end supports are obtained.
The performance of this formulation is verified by comparison with numerical examples in the literature
__________
Published in Prikladnaya Mekhanika, Vol. 41, No. 7, pp. 139–144, July 2005. 相似文献
10.