全文获取类型
收费全文 | 21693篇 |
免费 | 1828篇 |
国内免费 | 1385篇 |
专业分类
化学 | 1353篇 |
晶体学 | 69篇 |
力学 | 3627篇 |
综合类 | 314篇 |
数学 | 16318篇 |
物理学 | 3225篇 |
出版年
2024年 | 22篇 |
2023年 | 222篇 |
2022年 | 220篇 |
2021年 | 344篇 |
2020年 | 503篇 |
2019年 | 535篇 |
2018年 | 517篇 |
2017年 | 628篇 |
2016年 | 683篇 |
2015年 | 511篇 |
2014年 | 898篇 |
2013年 | 1842篇 |
2012年 | 915篇 |
2011年 | 1113篇 |
2010年 | 961篇 |
2009年 | 1286篇 |
2008年 | 1373篇 |
2007年 | 1383篇 |
2006年 | 1181篇 |
2005年 | 1092篇 |
2004年 | 967篇 |
2003年 | 889篇 |
2002年 | 861篇 |
2001年 | 721篇 |
2000年 | 699篇 |
1999年 | 589篇 |
1998年 | 635篇 |
1997年 | 515篇 |
1996年 | 377篇 |
1995年 | 310篇 |
1994年 | 285篇 |
1993年 | 228篇 |
1992年 | 209篇 |
1991年 | 176篇 |
1990年 | 157篇 |
1989年 | 107篇 |
1988年 | 101篇 |
1987年 | 83篇 |
1986年 | 84篇 |
1985年 | 91篇 |
1984年 | 94篇 |
1983年 | 60篇 |
1982年 | 77篇 |
1981年 | 63篇 |
1980年 | 67篇 |
1979年 | 64篇 |
1978年 | 45篇 |
1977年 | 40篇 |
1976年 | 39篇 |
1973年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 534 毫秒
991.
Shunpu Zhang Rohana J. Karunamuni 《Annals of the Institute of Statistical Mathematics》2000,52(4):612-629
In this paper we consider the deconvolution problem in nonparametric density estimation. That is, one wishes to estimate the unknown density of a random variable X, say f
X
, based on the observed variables Y's, where Y = X + with being the error. Previous results on this problem have considered the estimation of f
X
at interior points. Here we study the deconvolution problem for boundary points. A kernel-type estimator is proposed, and its mean squared error properties, including the rates of convergence, are investigated for supersmooth and ordinary smooth error distributions. Results of a simulation study are also presented. 相似文献
992.
This paper deals with quasilinear elliptic differential inclusions defined in all of N and governed in general by a nonpotential quasilinear elliptic operator of the Leray–Lions type and a multivalued term in form of a (nonmonotone) state-dependent subdifferential. We prove the existence of entire extremal solutions within a sector of an ordered pair of appropriately defined upper and lower solutions without imposing any condition at infinity. Therefore, standard variational methods cannot be applied here. Furthermore, due to the unboundedness of the domain and due to lack of monotonicity of the operators involved, no comparison results are available such that the problem under consideration becomes even more difficult. 相似文献
993.
Lian-Xi Ku 《Southeast Asian Bulletin of Mathematics》2000,24(3):375-382
In this note, we prove that, for Robins boundary value problem, a unique solution exists if fx(t, x, x), fx(t, x, x), (t), and (t) are continuous, and fx -(t), fx -(t), 4(t) 2 + 2(t) ++ 2(t), and 4(t) 2 + 2(t) + 2(t).AMS Subject Classification (2000) 34B15 相似文献
994.
M. M. Cavalcanti V. N. Domingos Cavalcanti J. A. Soriano L. A. Medeiros 《Southeast Asian Bulletin of Mathematics》2000,24(2):183-199
In this paper, we study a hyperbolic model based on the equation
with nonlinear boundary conditions given by
.We prove the existence and the uniqueness of global solutions. Also, we obtain the uniform decay of the energy without control of its derivative sign.AMS Subject Classification (2000), 35L05, 35L70, 35B40 相似文献
995.
Jeannette Van Iseghem 《Acta Appl Math》2000,61(1-3):351-365
The aim of this paper is the expansion of a matrix function in terms of a matrix-continued fraction as defined by Sorokin and Van Iseghem. The function under study is the Weyl function or resolvent function of an operator, given in the standard basis by a bi-infinite band matrix, with p subdiagonals and q superdiagonals, where the p + q – 1 intermediate diagonals are zero. The main goal of this paper is to find, for the moments, an explicit form in terms of the coefficients of the continued fraction, called genetic sums, which lead to a generalization of the notion of a Stieltjes continued fraction. These results are extension of some results already found for the vector case (p = 1) and are a step in the direction towards the solution of the direct and inverse spectral problem. The actual computation of the approximants of the given function as the convergents of the continued fraction is shown to be effective. Some possible extensions are considered. 相似文献
996.
袁锦昀 《应用数学学报(英文版)》2000,16(2):130-139
1.IntroductionThegeneralizedleastsquaresproblem,definedasmin(Ax--b)"W--'(Ax--b),(1.1)xacwhereAERm",m>n,bERm,andWERm'misasymmetricandpositivedefinitematrix,isfrequentlyfoundwhensolvingproblemsinstatistics,engineeringandeconomics.Forexample,wegetgeneralizedleastsquaresproblemswhensolvingnonlinearregressionanalysisbyquasi-likelihoodestimation,imagereconstructionproblemsandeconomicmodelsobtainedbythemaximumlikelihoodmethod(of.[1,21).Paige[3,4]investigatestheproblemexplicitly.Hechangestheorig… 相似文献
997.
We consider a one-dimensional incompressible flow through a porous medium undergoing deformations such that the porosity and the hydraulic conductivity can be considered to be functions of the flux intensity. The medium is initially dry and we neglect capillarity, so that a sharp wetting front proceeds into the medium. We consider the open problem of the continuation of the solution possibly in the case of onset of singularities, which can be interpreted as a local collapse of the medium. In particular we analyze the case in which the boundary pressure has a piecewise constant derivative. 相似文献
998.
51. IntroductionLet fi C Re (n = 1,2) be a bounded smooth domain. Consider the following nonhomogeneous initial-boundary value problem for the unsaturated Landau-Lifshitz systems offerromagnetic spin chain with Gilbert damping constant afl > 0,where adZ is the exchange constallt, u = (u', u', u'), "o(x) is smooth and satisfies the unsaturated condition, i.e., Ilo(~)I gi constant, and in IVuol' < co, "o(x)IOn = op(x). DenoteW(x) = luo(x)I. We assume 0 < m = mane < M ~ mpxW. Throughout t… 相似文献
999.
The evolution Boussinesq equations describe the evolution of the temperature and velocity fields of viscous incompressible Newtonian fluids. Very often, they are a reasonable model to render relevant phenomena of flows in which the thermal effects play an essential role. In the paper we prescribe non-Dirichlet boundary conditions on a part of the boundary and prove the existence and uniqueness of solutions to the Boussinesq equations on a (short) time interval. The length of the time interval depends only on certain norms of the given data. In the proof we use a fixed point theorem method in Sobolev spaces with non-integer order derivatives. The proof is performed for Lipschitz domains and a wide class of data. 相似文献
1000.
Petr Knobloch 《Applications of Mathematics》2000,45(2):99-129
We investigate a finite element discretization of the Stokes equations with nonstandard boundary conditions, defined in a bounded three-dimensional domain with a curved, piecewise smooth boundary. For tetrahedral triangulations of this domain we prove, under general assumptions on the discrete problem and without any additional regularity assumptions on the weak solution, that the discrete solutions converge to the weak solution. Examples of appropriate finite element spaces are given. 相似文献