全文获取类型
收费全文 | 3839篇 |
免费 | 130篇 |
国内免费 | 19篇 |
专业分类
化学 | 2437篇 |
晶体学 | 16篇 |
力学 | 106篇 |
数学 | 584篇 |
物理学 | 845篇 |
出版年
2022年 | 52篇 |
2021年 | 56篇 |
2020年 | 51篇 |
2019年 | 66篇 |
2018年 | 37篇 |
2017年 | 41篇 |
2016年 | 87篇 |
2015年 | 85篇 |
2014年 | 106篇 |
2013年 | 176篇 |
2012年 | 198篇 |
2011年 | 239篇 |
2010年 | 116篇 |
2009年 | 101篇 |
2008年 | 187篇 |
2007年 | 198篇 |
2006年 | 187篇 |
2005年 | 185篇 |
2004年 | 152篇 |
2003年 | 143篇 |
2002年 | 120篇 |
2001年 | 78篇 |
2000年 | 75篇 |
1999年 | 57篇 |
1998年 | 36篇 |
1997年 | 53篇 |
1996年 | 51篇 |
1995年 | 61篇 |
1994年 | 57篇 |
1993年 | 49篇 |
1992年 | 51篇 |
1991年 | 41篇 |
1990年 | 48篇 |
1989年 | 24篇 |
1988年 | 29篇 |
1987年 | 28篇 |
1986年 | 25篇 |
1985年 | 41篇 |
1984年 | 33篇 |
1982年 | 38篇 |
1981年 | 43篇 |
1980年 | 31篇 |
1979年 | 43篇 |
1978年 | 37篇 |
1977年 | 36篇 |
1976年 | 40篇 |
1975年 | 35篇 |
1974年 | 33篇 |
1973年 | 38篇 |
1972年 | 29篇 |
排序方式: 共有3988条查询结果,搜索用时 15 毫秒
21.
An adaptive pruning algorithm for the discrete L-curve criterion 总被引:1,自引:0,他引:1
Per Christian Hansen Toke Koldborg Jensen Giuseppe Rodriguez 《Journal of Computational and Applied Mathematics》2007
We describe a robust and adaptive implementation of the L-curve criterion. The algorithm locates the corner of a discrete L-curve which is a log–log plot of corresponding residual norms and solution norms of regularized solutions from a method with a discrete regularization parameter (such as truncated SVD or regularizing CG iterations). Our algorithm needs no predefined parameters, and in order to capture the global features of the curve in an adaptive fashion, we use a sequence of pruned L-curves that correspond to considering the curves at different scales. We compare our new algorithm to existing algorithms and demonstrate its robustness by numerical examples. 相似文献
22.
Gilles Carron 《Journal of Functional Analysis》2004,212(1):222-260
We give a formula for the jump at zero of the spectral shift function associated with Schrödinger operator on manifolds with conical ends. We show that, according to its decay, a zero energy resonant state has a non-integer contribution. 相似文献
23.
Quantization consists in studying the L
r
-error induced by the approximation of a random vector X by a vector (quantized version) taking a finite number n of values. We investigate this problem for Gaussian random vectors in an infinite dimensional Banach space and in particular, for Gaussian processes. A precise link proved by Fehringer(4) and Dereich et al.
(3) relates lower and upper bounds for small ball probabilities with upper and lower bounds for the quantization error, respectively. We establish a complete relationship by showing that the same holds for the direction from the quantization error to small ball probabilities. This allows us to compute the exact rate of convergence to zero of the minimal L
r
-quantization error from logarithmic small ball asymptotics and vice versa. 相似文献
24.
This paper investigates the mathematical well‐posedness of the variational model of quasi‐static growth for a brittle crack proposed by Francfort and Marigo in [15]. The starting point is a time discretized version of that evolution which results in a sequence of minimization problems of Mumford and Shah type functionals. The natural weak setting is that of special functions of bounded variation, and the main difficulty in showing existence of the time‐continuous quasi‐static growth is to pass to the limit as the time‐discretization step tends to 0. This is performed with the help of a jump transfer theorem which permits, under weak convergence assumptions for a sequence {un} of SBV‐functions to its BV‐limit u, to transfer the part of the jump set of any test field that lies in the jump set of u onto that of the converging sequence {un}. In particular, it is shown that the notion of minimizer of a Mumford and Shah type functional for its own jump set is stable under weak convergence assumptions. Furthermore, our analysis justifies numerical methods used for computing the time‐continuous quasi‐static evolution. © 2003 Wiley Periodicals, Inc. 相似文献
25.
If
is a quasitriangular Lie bialgebra, the formal Poisson group
can be given a braiding structure. This was achieved by Weinstein and Xu using purely geometrical means, and independently by the authors by means of quantum groups. In this paper we compare these two approaches. First, we show that the braidings they produce share several similar properties (in particular, the construction is functorial); secondly, in the simplest case (G=SL2) they do coincide. The question then rises of whether they are always the same this is positively answered in a separate paper. 相似文献
26.
Claude Didierjean Julien Marin Emmanuel Wenger Jean‐Paul Briand Andr Aubry Gilles Guichard 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(3):o200-o203
X‐ray studies reveal that tert‐butyl (6S)‐6‐isobutyl‐2,4‐dioxopiperidine‐1‐carboxylate occurs in the 4‐enol form, viz. tert‐butyl (6S)‐4‐hydroxy‐6‐isobutyl‐2‐oxo‐1,2,5,6‐tetrahydropyridine‐1‐carboxylate, C14H23NO4, when crystals are grown from a mixture of dichloromethane and pentane, and has an axial orientation of the isobutyl side chain at the 6‐position of the piperidine ring. Reduction of the keto functionality leads predominantly to the corresponding β‐hydroxylated δ‐lactam, tert‐butyl (4R,6S)‐4‐hydroxy‐6‐isobutyl‐2‐oxopiperidine‐1‐carboxylate, C14H25NO4, with a cis configuration of the 4‐hydroxy and 6‐isobutyl groups. The two compounds show similar molecular packing driven by strong O—H⋯O=C hydrogen bonds, leading to infinite chains in the crystal structure. 相似文献
27.
Transverse displacement at total reflection near the grazing angle: a way to discriminate between theories 总被引:1,自引:0,他引:1
F. Pillon H. Gilles S. Girard M. Laroche O. Emile 《Applied physics. B, Lasers and optics》2005,80(3):355-357
The transverse shift is observed and precisely measured at total internal reflection on a dielectric interface for a circularly polarized light beam when the incident angle is scanned from the critical angle up to the grazing angle close to 90°. The experimental results show with no doubt that the transverse displacement exists far away from the critical angle and only vanishes at grazing angle. A comparison with theories also allows a discrimination between the most different theoretical models traditionally used to interpret physically this effect. 相似文献
28.
We report the first total synthesis of the cytotoxic marine alkaloids caulibugulone A-D. This synthesis confirmed the assigned structures and provided sufficient material for further biological testing. 相似文献
29.
A. Filarowski A. Koll A. Kochel J. Kalenik P. E. Hansen 《Journal of Molecular Structure》2004,700(1-3):67-72
The crystal structures of two ortho-hydroxy ketones (5-chloro-2-hydroxyacetophenone (I K) and 3,5-dichloro-2-hydroxyacetophenone (II K)) have been determined with X-ray diffraction at 100 K. A comparison of steric effects on properties of pseudoaromatic hydrogen bonds in ortho-hydroxy acetophenone and ortho-hydroxy ketimines have been carried out with the application of crystallographic data.
Nuclear quadrupole resonance (NQR) spectra have been measured and interpreted. 相似文献
30.
A. Hansen M.H. Jensen K. Sneppen G. Zocchi 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(1):157-161
We present a statistical mechanics treatment of the stability of globular proteins which takes explicitly into account the
coupling between the protein and water degrees of freedom. This allows us to describe both the cold and the warm unfolding,
thus qualitatively reproducing the known thermodynamics of proteins.
Received: 19 March 1998 / Revised and Accepted: 25 May 1998 相似文献