全文获取类型
收费全文 | 582篇 |
免费 | 16篇 |
国内免费 | 4篇 |
专业分类
化学 | 318篇 |
晶体学 | 3篇 |
力学 | 23篇 |
数学 | 68篇 |
物理学 | 190篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 25篇 |
2020年 | 21篇 |
2019年 | 9篇 |
2018年 | 10篇 |
2017年 | 12篇 |
2016年 | 26篇 |
2015年 | 18篇 |
2014年 | 11篇 |
2013年 | 28篇 |
2012年 | 56篇 |
2011年 | 42篇 |
2010年 | 34篇 |
2009年 | 33篇 |
2008年 | 32篇 |
2007年 | 29篇 |
2006年 | 28篇 |
2005年 | 25篇 |
2004年 | 17篇 |
2003年 | 6篇 |
2002年 | 8篇 |
2001年 | 10篇 |
2000年 | 11篇 |
1999年 | 12篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 7篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1970年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有602条查询结果,搜索用时 62 毫秒
81.
82.
83.
Díez D Sanchez JM Rodilla JM Rocha PM Mendes RS Paulino C Marcos IS Basabe P Urones JG 《Molecules (Basel, Switzerland)》2005,10(8):1005-1009
Incubation of sclareol with Rhizopus stolonifer affords in high yield a mixture of triols with 18-hydroxy-sclareol as the main component. 相似文献
84.
C. Mendes 《Algebra Universalis》2005,54(3):279-290
An Ockham algebra
that satisfies the identity
is called a Kn, m-algebra. Generalizing some results obtained in [2], J. Varlet and T. Blyth, in [3, Chapter 8], study congruences on K1, 1-algebras. In particular, they describe the complement (when it exists) of a principal congruence and characterize these congruences
that are complemented. In this paper we study the same question for Kn, m-algebras.
Received March 24, 2005; accepted in final form April 28, 2005. 相似文献
85.
H. V. Ribeiro R. S. Mendes L. C. Malacarne S. Picoli P. A. Santoro 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,75(3):327-334
A random walk-like model is considered to discuss statistical aspects of tournaments. The model is applied to soccer leagues
with emphasis on the scores. This competitive system was computationally simulated and the results are compared with empirical
data from the English, the German and the Spanish leagues and showed a good agreement with them. The present approach enabled
us to characterize a diffusion where the scores are not normally distributed, having a short and asymmetric tail extending
towards more positive values. We argue that this non-Gaussian behavior is related with the difference between the teams and
with the asymmetry of the scores system. In addition, we compared two tournament systems: the all-play-all and the elimination
tournaments. 相似文献
86.
k-Core organization of complex networks 总被引:1,自引:0,他引:1
We analytically describe the architecture of randomly damaged uncorrelated networks as a set of successively enclosed substructures--k-cores. The k-core is the largest subgraph where vertices have at least k interconnections. We find the structure of k-cores, their sizes, and their birthpoints--the bootstrap percolation thresholds. We show that in networks with a finite mean number zeta2 of the second-nearest neighbors, the emergence of a k-core is a hybrid phase transition. In contrast, if zeta2 diverges, the networks contain an infinite sequence of k-cores which are ultrarobust against random damage. 相似文献
87.
A parametrization methodology for evaluating the solvation free energy, using the polarizable continuum model implemented in Gamess software, is presented in a formulation which makes use of a group contribution conception to construct the cavities. The systems studied include alkanes, alcohols, aldehydes and ketones embeded in a continuous medium simulating the water as the solvent. For each family, the CH2, OH, and C=O moieties of atoms are put together in single spheres forming a group. The cavities are constructed in two different ways, one for the electrostatic component and the other for nonelectrostatic contributions, i.e., the cavitation, dispersion, and repulsion components of free energy of solvation. A multivariate analysis is performed to obtain an assembly of variables, for each homologous series, able to give the results which are close to experiment. The analysis is addressed in order to (i) compare the theoretical free energy of solvation with the experimental trends of the solutes in aqueous media, when the chain is increased, (ii) compare the behavior of each component of free energy with the increasing CH2 number, (iii) investigate the influence of the oxygen atom on the components, and (iv) quantify the relative contribution of each component to the final free energy of solvation for some homologous series. 相似文献
88.
The equilibrium tilt angle profile in a cell limited by two concentric cylinders filled with nematic liquid crystals is determined for strong homeotropic anchoring at the surfaces. The anchoring condition is such that the nematic director is perpendicular to the cylinder axes and a radial nonuniform electric field is applied to investigate a Fréedericksz transition. The distortions induced by the field remain in the plane perpendicular to the cylinder axes, and a threshold field is analytically determined indicating a transition from a pure splay to a splay-bend conformation of the director. It is shown that this transition can be induced by the thickness of the region between the two cylinders, and can be detected even in the absence of an external field. If the maximum value of the tilt angle is assumed as an order parameter, its behavior near to the transition can be used to obtain the critical exponent, which is the same as the one obtained in the mean field approximation. These results are indications that nontrivial consequences may occur when complex fluids are subject to non-planar geometries. 相似文献
89.
Pantaleón D. Romero Jéferson R. P. Coêlho Catarina Mendes de Jesus 《Mathematical Methods in the Applied Sciences》2020,43(14):8177-8191
The aim of this paper is to introduce a computational tool that checks theoretical conditions in order to determine whether a weighted graph, as a topological invariant of stable maps, can be associated to stable maps without cusps (ie, fold maps) from closed surfaces to the projective plan. 相似文献
90.
Abraão Mendes 《Journal of Geometric Analysis》2018,28(2):1245-1257
In this paper, we obtain an analogue of Toponogov theorem in dimension 3 for compact manifolds \(M^3\) with nonnegative Ricci curvature and strictly convex boundary \(\partial M\). Here we obtain a sharp upper bound for the length \(L(\partial \Sigma )\) of the boundary \(\partial \Sigma \) of a free boundary minimal surface \(\Sigma ^2\) in \(M^3\) in terms of the genus of \(\Sigma \) and the number of connected components of \(\partial \Sigma \), assuming \(\Sigma \) has index one. After, under a natural hypothesis on the geometry of M along \(\partial M\), we prove that if \(L(\partial \Sigma )\) saturates the respective upper bound, then \(M^3\) is isometric to the Euclidean 3-ball and \(\Sigma ^2\) is isometric to the Euclidean disk. In particular, we get a sharp upper bound for the area of \(\Sigma \), when \(M^3\) is a strictly convex body in \(\mathbb {R}^3\), which is saturated only on the Euclidean 3-balls (by the Euclidean disks). We also consider similar results for free boundary stable CMC surfaces. 相似文献