全文获取类型
收费全文 | 4576篇 |
免费 | 564篇 |
国内免费 | 429篇 |
专业分类
化学 | 444篇 |
晶体学 | 8篇 |
力学 | 477篇 |
综合类 | 131篇 |
数学 | 3744篇 |
物理学 | 765篇 |
出版年
2024年 | 8篇 |
2023年 | 55篇 |
2022年 | 53篇 |
2021年 | 105篇 |
2020年 | 143篇 |
2019年 | 154篇 |
2018年 | 157篇 |
2017年 | 202篇 |
2016年 | 210篇 |
2015年 | 124篇 |
2014年 | 217篇 |
2013年 | 503篇 |
2012年 | 225篇 |
2011年 | 225篇 |
2010年 | 197篇 |
2009年 | 242篇 |
2008年 | 287篇 |
2007年 | 281篇 |
2006年 | 248篇 |
2005年 | 253篇 |
2004年 | 205篇 |
2003年 | 192篇 |
2002年 | 218篇 |
2001年 | 161篇 |
2000年 | 141篇 |
1999年 | 122篇 |
1998年 | 103篇 |
1997年 | 105篇 |
1996年 | 71篇 |
1995年 | 68篇 |
1994年 | 52篇 |
1993年 | 39篇 |
1992年 | 26篇 |
1991年 | 21篇 |
1990年 | 19篇 |
1989年 | 21篇 |
1988年 | 11篇 |
1987年 | 14篇 |
1986年 | 3篇 |
1985年 | 19篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 9篇 |
1976年 | 3篇 |
1936年 | 2篇 |
排序方式: 共有5569条查询结果,搜索用时 15 毫秒
81.
We solve the problem of describing compatible nonlocal Poisson brackets of hydrodynamic type. We prove that for nonsingular pairs of compatible nonlocal Poisson brackets of hydrodynamic type, there exist special local coordinates such that the metrics and the Weingarten operators of both brackets are diagonal. The nonlinear evolution equations describing all nonsingular pairs of compatible nonlocal Poisson brackets of hydrodynamic type are derived in these special coordinates, and the integrability of these equations is proved using the inverse scattering transform. The Lax pairs with a spectral parameter for these equations are found. We construct various classes of integrable reductions of the derived equations. These classes of reductions are of an independent differential-geometric and applied interest. In particular, if one of the compatible Poisson brackets is local, we obtain integrable reductions of the classical Lamé equations describing all orthogonal curvilinear coordinate systems in a flat space; if one of the compatible brackets is generated by a constant-curvature metric, the corresponding equations describe integrable reductions of the equations for orthogonal curvilinear coordinate systems in a space of constant curvature. 相似文献
82.
83.
84.
This paper investigates regression quantiles (RQ) for unstable autoregressive models. The uniform Bahadur representation of the RQ process is obtained. The joint asymptotic distribution of the RQ process is derived in a unified manner for all types of characteristic roots on or outside the unit circle. It involves stochastic integrals in terms of a sequence of independent and identically distributed multivariate Brownian motions with correlated components. The related L-estimator is also discussed. The asymptotic distributions of the RQ and the L-estimator corresponding to the nonstationary componentwise arguments can be transformed into a function of a normal random variable and a sequence of i.i.d. univariate Brownian motions. This is different from the analysis based on the LSE in the literature. As an auxiliary theorem, a weak convergence of a randomly weighted residual empirical process to the stochastic integral of a Kiefer process is established. The results obtained in this paper provide an asymptotic theory for nonstationary time series processes, which can be used to construct robust unit root tests. 相似文献
85.
Hua Ning LIU Wen Peng ZHANG 《数学学报(英文版)》2007,23(5):915-924
The main purpose of this paper is to use the generalized Bernoulli numbers, Gauss sums and the mean value theorems of Dirichlet L-functions between a quadratic residue and its inverse modulo p value formula. to study the asymptotic property of the difference (a prime), and to give an interesting hybrid mean 相似文献
86.
THE NECESSARY AND SUFFICIENT CONDITIONS FOR THE SOLVABILITY OF A CLASS OF THE MATRIX INVERSE PROBLEM
Censider the solutions of the matrix inverse problem, which are symmetric positive semide finite on a subspace. Necessary and sufficient conditions for the solvability, as well as the general solution are obtained. The best approximate solution by the above solution set is given. Thus the open problem in [1] is solved. 相似文献
87.
对四分块矩阵A=A(︿) A(︿,︿′)A(︿′,︿) A(︿′)来说 ,如果 A和 A(︿)都是非奇异的 ,则A- 1 (︿′) =(A/︿) - 1 ,这里 A/ ︿=A(︿′) -A(︿′,︿) A(︿) - 1 A(︿,︿′)是 A(︿)在 A中的 Schur补 .王伯英教授指出上述等式 ,对半正定的 Hermitian矩阵而言 ,一般也是不能推广到 Moore-Penrose逆上去的 .在某些限制条件下 ,我们证明了广义逆的主子矩阵与广义 Schur补的关系是密切的 ,它使经典结果成为特例 相似文献
88.
A. Meister 《Mathematical Methods of Statistics》2007,16(1):63-76
This paper addresses the statistical problem of density deconvolution under the condition that the density to be estimated
has compact support. We introduce a new estimation procedure, which establishes faster rates of convergence for smooth densities
as compared to the optimal rates for smooth densities with unbounded support. This framework also allows us to relax the usual
condition of known error density with non-vanishing Fourier transform, so that a nonparametric class of densities is valid;
therefore, even the shape of the noise density need not be assumed. These results can also be generalized for fast decaying
densities with unbounded support. We prove optimality of the rates in the underlying experiment and study the practical performance
of our estimator by numerical simulations.
相似文献
89.
本文用另一方法证明了非对称矩阵的奇异值是处处强半光滑的,并利用这一性质给出求解逆奇异值问题的相对广义牛顿法,该方法具有Q-二阶收敛速度. 相似文献
90.
The problem considered is that of determining the shape of aplane acoustically sound-soft obstacle from the knowledge ofthe far-field pattern for one time-harmonic incident field.An iterative procedure is proposed based on two boundary integralsrepresenting the incident field and the far-field pattern, respectively.Numerical examples are included which show that the proceduregives accurate numerical approximations in relatively few iterations. 相似文献