全文获取类型
收费全文 | 2470篇 |
免费 | 217篇 |
国内免费 | 157篇 |
专业分类
化学 | 487篇 |
晶体学 | 12篇 |
力学 | 389篇 |
综合类 | 49篇 |
数学 | 1428篇 |
物理学 | 479篇 |
出版年
2024年 | 7篇 |
2023年 | 28篇 |
2022年 | 52篇 |
2021年 | 51篇 |
2020年 | 66篇 |
2019年 | 56篇 |
2018年 | 52篇 |
2017年 | 76篇 |
2016年 | 99篇 |
2015年 | 81篇 |
2014年 | 119篇 |
2013年 | 211篇 |
2012年 | 112篇 |
2011年 | 108篇 |
2010年 | 82篇 |
2009年 | 128篇 |
2008年 | 130篇 |
2007年 | 163篇 |
2006年 | 158篇 |
2005年 | 135篇 |
2004年 | 101篇 |
2003年 | 87篇 |
2002年 | 103篇 |
2001年 | 86篇 |
2000年 | 91篇 |
1999年 | 68篇 |
1998年 | 56篇 |
1997年 | 54篇 |
1996年 | 43篇 |
1995年 | 29篇 |
1994年 | 22篇 |
1993年 | 22篇 |
1992年 | 19篇 |
1991年 | 9篇 |
1990年 | 22篇 |
1989年 | 17篇 |
1988年 | 6篇 |
1987年 | 11篇 |
1986年 | 14篇 |
1985年 | 10篇 |
1984年 | 14篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1974年 | 2篇 |
排序方式: 共有2844条查询结果,搜索用时 62 毫秒
131.
Frieder Knüppel 《Geometriae Dedicata》1999,76(3):253-264
Let V be a finite-dimensional vector-space. A linear mapping on V is called simple if V( - 1) is 1-dimensional. Let S be a set of simple bijections on V. We discuss conditions entraining that each element of S is orthogonal (respectively symplectic) under an appropriate symmetric (respectively symplectic) bilinear form on V. 相似文献
132.
On the distribution of the length of the longest increasing subsequence of random permutations 总被引:18,自引:0,他引:18
Jinho Baik Percy Deift Kurt Johansson 《Journal of the American Mathematical Society》1999,12(4):1119-1178
The authors consider the length, , of the longest increasing subsequence of a random permutation of numbers. The main result in this paper is a proof that the distribution function for , suitably centered and scaled, converges to the Tracy-Widom distribution of the largest eigenvalue of a random GUE matrix. The authors also prove convergence of moments. The proof is based on the steepest descent method for Riemann-Hilbert problems, introduced by Deift and Zhou in 1993 in the context of integrable systems. The applicability of the Riemann-Hilbert technique depends, in turn, on the determinantal formula of Gessel for the Poissonization of the distribution function of .
133.
Walter Trebels 《Proceedings of the American Mathematical Society》1999,127(10):2883-2887
Within the setting of abstract Cesàro-bounded Fourier series a -functional is introduced and characterized by the convergence behavior of some linear means. Applications are given within the framework of Jacobi, Laguerre and Hermite expansions. In particular, Ditzian's (1996) equivalence result in the setting of Legendre expansions is covered.
134.
Several new constructions for difference matrices are given. One classof constructions uses pairwise balanced designs to develop newdifference matrices over the additive group of GF (q). A second class of constructions gives difference matrices overgroups whose orders are not (necessarily) prime powers. 相似文献
135.
136.
M.A. Chmielewski 《Journal of multivariate analysis》1980,10(3):343-350
The usual assumption in multivariate hypothesis testing is that the sample consists of n independent, identically distributed Gaussian m-vectors. In this paper this assumption is weakened by considering a class of distributions for which the vector observations are not necessarily either Gaussian or independent. This class contains the elliptically symmetric laws with densities of the form f(X(n × m)) = ψ[tr(X ? M)′ (X ? M)Σ?1]. For testing the equality of k scale matrices and for the sphericity hypothesis it is shown, by using the structure of the underlying distribution rather than any specific form of the density, that the usual invariant normal-theory tests are exactly robust, for both the null and non-null cases, under this wider class. 相似文献
137.
Michael D. Perlman 《Journal of multivariate analysis》1974,4(1):22-30
It is shown that for the MANOVA problem the power function of the test based on the trace of a multivariate beta matrix is monotonically increasing in each noncentrality parameter provided that the cutoff point is not too large. This result is also true for the problem of testing independence of two sets of variates. 相似文献
138.
The criterion robustness of the standard likelihood ratio test (LRT) under the multivariate normal regression model and also the inference robustness of the same test under the univariate set up are established for certain nonnormal distributions of errors. Restricting attention to the normal distribution of errors in the context of univariate regression models, conditions on the design matrix are established under which the usual LRT of a linear hypothesis (under homoscedasticity of errors) remains valid if the errors have an intraclass covariance structure. The conditions hold in the case of some standard designs. The relevance of C. R. Rao's (1967 In Proceedings Fifth Berkeley Symposium on Math. Stat. and Prob., Vol. 1, pp. 355–372) and G. Zyskind's (1967, Ann. Math. Statist.38 1092–1110) conditions in this context is discussed. 相似文献
139.
Welch K Mousavi S Lundberg B Strømme M 《The European physical journal. E, Soft matter》2005,18(1):105-112
A newly developed method for determining the frequency-dependent complex Young's modulus was employed to analyze the mechanical
response of compacted microcrystalline cellulose, sorbitol, ethyl cellulose and starch for frequencies up to 20 kHz. A Debye-like
relaxation was observed in all the studied pharmaceutical excipient materials and a comparison with corresponding dielectric
spectroscopy data was made. The location in frequency of the relaxation peak was shown to correlate to the measured tensile
strength of the tablets, and the relaxation was interpreted as the vibrational response of the interparticle hydrogen and
van der Waals bindings in the tablets. Further, the measured relaxation strength, holding information about the energy loss
involved in the relaxation processes, showed that the weakest material in terms of tensile strength, starch, is the material
among the four tested ones that is able to absorb the most energy within its structure when exposed to external perturbations
inducing vibrations in the studied frequency range. The results indicate that mechanical relaxation analysis performed over
relatively broad frequency ranges should be useful for predicting material properties of importance for the functionality
of a material in applications such as, e.g., drug delivery, drug storage and handling, and also for clarifying the origin of hitherto unexplained molecular processes. 相似文献
140.
A common method of fitting curves and surfaces to data is to minimize the sum of squares of the orthogonal distances from the data points to the curve or surface, a process known as orthogonal distance regression. Here we consider fitting geometrical objects to data when some orthogonal distances are not available. Methods based on the Gauss–Newton method are developed, analyzed and illustrated by examples.
AMS subject classification (2000) 65D10, 65K05. 相似文献