全文获取类型
收费全文 | 12413篇 |
免费 | 736篇 |
国内免费 | 745篇 |
专业分类
化学 | 490篇 |
晶体学 | 4篇 |
力学 | 938篇 |
综合类 | 144篇 |
数学 | 10938篇 |
物理学 | 1380篇 |
出版年
2023年 | 102篇 |
2022年 | 101篇 |
2021年 | 147篇 |
2020年 | 212篇 |
2019年 | 262篇 |
2018年 | 241篇 |
2017年 | 274篇 |
2016年 | 299篇 |
2015年 | 238篇 |
2014年 | 410篇 |
2013年 | 902篇 |
2012年 | 505篇 |
2011年 | 511篇 |
2010年 | 445篇 |
2009年 | 671篇 |
2008年 | 734篇 |
2007年 | 737篇 |
2006年 | 675篇 |
2005年 | 590篇 |
2004年 | 532篇 |
2003年 | 520篇 |
2002年 | 622篇 |
2001年 | 415篇 |
2000年 | 483篇 |
1999年 | 367篇 |
1998年 | 436篇 |
1997年 | 355篇 |
1996年 | 245篇 |
1995年 | 191篇 |
1994年 | 196篇 |
1993年 | 157篇 |
1992年 | 152篇 |
1991年 | 127篇 |
1990年 | 121篇 |
1989年 | 85篇 |
1988年 | 72篇 |
1987年 | 66篇 |
1986年 | 82篇 |
1985年 | 75篇 |
1984年 | 72篇 |
1983年 | 35篇 |
1982年 | 60篇 |
1981年 | 58篇 |
1980年 | 61篇 |
1979年 | 57篇 |
1978年 | 46篇 |
1977年 | 45篇 |
1976年 | 41篇 |
1975年 | 14篇 |
1974年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
1.
This paper infers from a generalized Picone identity the uniqueness of the stable positive solution for a class of semilinear equations of superlinear indefinite type, as well as the uniqueness and global attractivity of the coexistence state in two generalized diffusive prototypes of the symbiotic and competing species models of Lotka–Volterra. The optimality of these uniqueness theorems reveals the tremendous strength of the Picone identity. 相似文献
2.
In this article, we construct and analyze a residual-based a posteriori error estimator for a quadratic finite volume method (FVM) for solving nonlinear elliptic partial differential equations with homogeneous Dirichlet boundary conditions. We shall prove that the a posteriori error estimator yields the global upper and local lower bounds for the norm error of the FVM. So that the a posteriori error estimator is equivalent to the true error in a certain sense. Numerical experiments are performed to illustrate the theoretical results. 相似文献
3.
4.
5.
In this paper, we consider a viscoelastic wave equation of variable coefficients in the presence of past history with nonlinear damping and delay in the internal feedback and dynamic boundary conditions. Under suitable assumptions, we establish an explicit and general decay rate result without imposing restrictive assumption on the behavior of the relaxation function at infinity by Riemannian geometry method and Lyapunov functional method. 相似文献
6.
In this paper, we study the existence of the uniformly minimum risk equivariant (UMRE) estimators of parameters in a class
of normal linear models, which include the normal variance components model, the growth curve model, the extended growth curve
model, and the seemingly unrelated regression equations model, and so on. The necessary and sufficient conditions are given
for the existence of UMRE estimators of the estimable linear functions of regression coefficients, the covariance matrixV and (trV)α, where α > 0 is known, in the models under an affine group of transformations for quadratic losses and matrix losses, respectively.
Under the (extended) growth curve model and the seemingly unrelated regression equations model, the conclusions given in literature
for estimating regression coefficients can be derived by applying the general results in this paper, and the sufficient conditions
for non-existence of UMRE estimators ofV and tr(V) are expanded to be necessary and sufficient conditions. In addition, the necessary and sufficient conditions that there
exist UMRE estimators of parameters in the variance components model are obtained for the first time. 相似文献
7.
M.A. Tawhid 《Journal of Optimization Theory and Applications》2002,113(1):149-164
In this paper, we give some sufficient conditions for the local uniqueness of solutions to nonsmooth variational inequalities where the underlying functions are H-differentiable and the underlying set is a closed convex set/polyhedral set/box/polyhedral cone. We show how the solution of a linearized variational inequality is related to the solution of the variational inequality. These results extend/unify various similar results proved for C
1 and locally Lipschitzian variational inequality problems. When specialized to the nonlinear complementarity problem, our results extend/unify those of C
2 and C
1 nonlinear complementarity problems. 相似文献
8.
Matt Visser Carlos Barceló Stefano Liberati 《General Relativity and Gravitation》2002,34(10):1719-1734
Condensed matter systems, such as acoustics in flowing fluids, light in moving dielectrics, or quasiparticles in a moving superfluid, can be used to mimic aspects of general relativity. More precisely these systems (and others) provide experimentally accessible models of curved-space quantum field theory. As such they mimic kinematic aspects of general relativity, though typically they do not mimic the dynamics. Although these analogue models are thereby limited in their ability to duplicate all the effects of Einstein gravity they nevertheless are extremely important—they provide black hole analogues (some of which have already been seen experimentally) and lead to tests of basic principles of curved-space quantum field theory. Currently these tests are still in the realm of gedanken-experiments, but there are plausible candidate models that should lead to laboratory experiments in the not too distant future. 相似文献
9.
We discuss an error estimation procedure for the global error of collocation schemes applied to solve singular boundary value problems with a singularity of the first kind. This a posteriori estimate of the global error was proposed by Stetter in 1978 and is based on the idea of Defect Correction, originally due to Zadunaisky. Here, we present a new, carefully designed modification of this error estimate which not only results in less computational work but also appears to perform satisfactorily for singular problems. We give a full analytical justification for the asymptotical correctness of the error estimate when it is applied to a general nonlinear regular problem. For the singular case, we are presently only able to provide computational evidence for the full convergence order, the related analysis is still work in progress. This global estimate is the basis for a grid selection routine in which the grid is modified with the aim to equidistribute the global error. This procedure yields meshes suitable for an efficient numerical solution. Most importantly, we observe that the grid is refined in a way reflecting only the behavior of the solution and remains unaffected by the unsmooth direction field close to the singular point. 相似文献
10.
This paper through discussing subdifferentiability and convexity of convex functions shows that a Banach space admits an equivalent
uniformly [locally uniformly, strictly] convex norm if and only if there exists a continuous uniformly [locally uniformly,
strictly] convex function on some nonempty open convex subset of the space and presents some characterizations of super-reflexive
Banach spaces.
Supported by NSFC 相似文献