全文获取类型
收费全文 | 10084篇 |
免费 | 228篇 |
国内免费 | 157篇 |
专业分类
化学 | 1266篇 |
晶体学 | 64篇 |
力学 | 51篇 |
综合类 | 17篇 |
数学 | 8203篇 |
物理学 | 868篇 |
出版年
2024年 | 6篇 |
2023年 | 35篇 |
2022年 | 44篇 |
2021年 | 54篇 |
2020年 | 68篇 |
2019年 | 224篇 |
2018年 | 208篇 |
2017年 | 115篇 |
2016年 | 101篇 |
2015年 | 140篇 |
2014年 | 275篇 |
2013年 | 513篇 |
2012年 | 312篇 |
2011年 | 618篇 |
2010年 | 539篇 |
2009年 | 650篇 |
2008年 | 671篇 |
2007年 | 767篇 |
2006年 | 573篇 |
2005年 | 370篇 |
2004年 | 304篇 |
2003年 | 318篇 |
2002年 | 266篇 |
2001年 | 186篇 |
2000年 | 200篇 |
1999年 | 254篇 |
1998年 | 252篇 |
1997年 | 211篇 |
1996年 | 227篇 |
1995年 | 272篇 |
1994年 | 216篇 |
1993年 | 209篇 |
1992年 | 183篇 |
1991年 | 103篇 |
1990年 | 103篇 |
1989年 | 127篇 |
1988年 | 65篇 |
1987年 | 58篇 |
1986年 | 58篇 |
1985年 | 91篇 |
1984年 | 93篇 |
1983年 | 62篇 |
1982年 | 84篇 |
1981年 | 53篇 |
1980年 | 43篇 |
1979年 | 43篇 |
1978年 | 49篇 |
1977年 | 21篇 |
1976年 | 18篇 |
1975年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
F-H实验仪与光栅光谱仪连用观测253.7nm谱线 总被引:1,自引:0,他引:1
通过F-H实验仪和光栅光谱仪的连用,可实时观测汞原子从6s6s1So态激发到6s6sSP1态,退激时,辐射出能量为4.9eV的光量子,其波长为253.7nm. 相似文献
62.
Ewa Stró?yna 《Journal of Differential Equations》2003,193(1):239-259
We solve completely the problem of classification of germs of complex planar vector fields with nilpotent singularity with respect to formal orbital equivalence. 相似文献
63.
Parameters of Gaussian multivariate models are often estimated using the maximum likelihood approach. In spite of its merits, this methodology is not practical when the sample size is very large, as, for example, in the case of massive georeferenced data sets. In this paper, we study the asymptotic properties of the estimators that minimize three alternatives to the likelihood function, designed to increase the computational efficiency. This is achieved by applying the information sandwich technique to expansions of the pseudo-likelihood functions as quadratic forms of independent normal random variables. Theoretical calculations are given for a first-order autoregressive time series and then extended to a two-dimensional autoregressive process on a lattice. We compare the efficiency of the three estimators to that of the maximum likelihood estimator as well as among themselves, using numerical calculations of the theoretical results and simulations. 相似文献
64.
Yasufumi Hashimoto 《Journal of Number Theory》2007,122(2):324-335
In [P. Sarnak, Class numbers of indefinite binary quadratic forms, J. Number Theory 15 (1982) 229-247], it was proved that the Selberg zeta function for SL2(Z) is expressed in terms of the fundamental units and the class numbers of the primitive indefinite binary quadratic forms. The aim of this paper is to obtain similar arithmetic expressions of the logarithmic derivatives of the Selberg zeta functions for congruence subgroups of SL2(Z). As applications, we study the Brun-Titchmarsh type prime geodesic theorem and the asymptotic formula of the sum of the class number. 相似文献
65.
A new preconditioned conjugate gradient (PCG)-based domain decomposition method is given for the solution of linear equations
arising in the finite element method applied to the elliptic Neumann problem. The novelty of the proposed method is in the
recommended preconditioner which is constructed by using cyclic matrix. The resulting preconditioned algorithms are well suited
to parallel computation. 相似文献
66.
A robust and efficient adaptive reweighted estimator of multivariate location and scatter 总被引:1,自引:0,他引:1
Daniel Gervini 《Journal of multivariate analysis》2003,84(1):116-144
This article proposes a reweighted estimator of multivariate location and scatter, with weights adaptively computed from the data. Its breakdown point and asymptotic behavior under elliptical distributions are established. This adaptive estimator is able to attain simultaneously the maximum possible breakdown point for affine equivariant estimators and full asymptotic efficiency at the multivariate normal distribution. For the special case of hard-rejection weights and the MCD as initial estimator, it is shown to be more efficient than its non-adaptive counterpart for a broad range of heavy-tailed elliptical distributions. A Monte Carlo study shows that the adaptive estimator is as robust as its non-adaptive relative for several types of bias-inducing contaminations, while it is remarkably more efficient under normality for sample sizes as small as 200. 相似文献
67.
Yuk-Kam Lau 《Archiv der Mathematik》2003,81(2):169-174
We establish a mean square estimate on the weight aspect for
symmetric square L-functions at every point
on the critical line.
Received: 15 February 2002 相似文献
68.
M. C. Crabb 《Journal of Fixed Point Theory and Applications》2007,2(2):171-193
We describe an equivariant version (for actions of a finite group G) of Dold’s index theory, [10], for iterated maps. Equivariant Dold indices are defined, in general, for a G-map U → X defined on an open G-subset of a G-ANR X (and satisfying a suitable compactness condition). A local index for isolated fixed-points is introduced, and the theorem
of Shub and Sullivan on the vanishing of all but finitely many Dold indices for a continuously differentiable map is extended
to the equivariant case. Homotopy Dold indices, arising from the equivariant Reidemeister trace, are also considered.
相似文献
69.
曾韧英 《应用数学与计算数学学报》1997,11(1):27-32
本文讨论定义在Banach空间上的,既具有等式约束又具有不等式约束的,非光滑(F,P)不变凸多目标规划的Wolfe对偶性,Mond-Weir型对偶性可类似讨论之。 相似文献
70.
Emulsions of perfluorotributylamine (FTBA) and perflubron were evaluated for their utility in 19F echo planar imaging. Fluorine images of the emulsions were obtained in a phantom and two mice that had been predosed. Both agents, but particularly perflubron, show potential for fluorine echo planar studies because of the long spin-spin relaxation times of the CF3 resonances. High resolution thin slice images obtained in as little as 26.6 ms are presented. 相似文献