全文获取类型
收费全文 | 176篇 |
免费 | 19篇 |
国内免费 | 15篇 |
专业分类
化学 | 37篇 |
力学 | 10篇 |
数学 | 72篇 |
物理学 | 91篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2019年 | 4篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 2篇 |
2015年 | 5篇 |
2014年 | 3篇 |
2013年 | 7篇 |
2012年 | 3篇 |
2011年 | 5篇 |
2010年 | 3篇 |
2009年 | 5篇 |
2008年 | 8篇 |
2007年 | 13篇 |
2006年 | 9篇 |
2005年 | 10篇 |
2004年 | 12篇 |
2003年 | 7篇 |
2002年 | 9篇 |
2001年 | 4篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 12篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 6篇 |
1982年 | 1篇 |
排序方式: 共有210条查询结果,搜索用时 78 毫秒
41.
Sergio Albeverio Yuliya Kulyba Mykola Pratsiovytyi Grygoriy Torbin 《Mathematische Nachrichten》2015,288(16):1803-1813
We study properties of the distribution of a random variable of the continued fraction form where are independent and not necessarily identically distributed random variables. We prove the singularity of and study the fine spectral structure of such measures. 相似文献
42.
We investigated the cohesion of agglomerates formed by sticking two fractal clusters, each cluster having been previously
generated by particle aggregation on a 3D lattice. The degree of cohesion of an agglomerate of a given configuration was defined
by the number of connections simultaneously established on the two stuck clusters. All the possible nonoverlapping configurations
were investigated and the corresponding porosity and brittleness as well as the pore volume and connection frequencies were
determined. The numerical study showed the greater internal cohesion of agglomerates issued from sticking of reaction-limited
aggregation (RLA) clusters compared to that of diffusion-limited-aggregation (DLA) clusters. DLA and RLA agglomerates presented
continuously decreasing pore volume frequency curves, the latter agglomerates being characterised by a greater frequency of
large pores. Comparison with typical controlled fragmentation experiments showed the number of connections to be the prevailing
factor in the cohesion of aggregates formed in aqueous suspensions under various conditions.
Received: 25 January 2001 Accepted: 16 May 2001 相似文献
43.
We consider functions represented by series ∑g G cgψ(g − 1(x)) of wavelet-type, where G is a group generated by affine functions L1,…,Ln and ψ is piecewise affine. By means of those functions we characterize the class of self-affine fractal functions, previously studied by Barnsley et al. We compute their global and local Hölder exponents and investigate points of non-differentiability. Wavelet-representations for various continuous nowhere differentiable and singular functions are presented. Another application is the construction of functions with prescribed local Hölder exponents at each point. 相似文献
44.
Robert S. Strichartz 《Transactions of the American Mathematical Society》1999,351(5):1705-1752
For a compact Hausdorff space that is pathwise connected, we can define the connectivity dimension to be the infimum of all such that all points in can be connected by a path of Hausdorff dimension at most . We show how to compute the connectivity dimension for a class of self-similar sets in that we call point connected, meaning roughly that is generated by an iterated function system acting on a polytope such that the images of intersect at single vertices. This class includes the polygaskets, which are obtained from a regular -gon in the plane by contracting equally to all vertices, provided is not divisible by 4. (The Sierpinski gasket corresponds to .) We also provide a separate computation for the octogasket (), which is not point connected. We also show, in these examples, that , where the infimum is taken over all paths connecting and , and denotes Hausdorff measure, is equivalent to the original metric on . Given a compact subset of the plane of Hausdorff dimension and connectivity dimension , we can define the isoperimetric profile function to be the supremum of , where is a region in the plane bounded by a Jordan curve (or union of Jordan curves) entirely contained in , with . The analog of the standard isperimetric estimate is . We are particularly interested in finding the best constant and identifying the extremal domains where we have equality. We solve this problem for polygaskets with . In addition, for we find an entirely different estimate for as , since the boundary of has infinite measure. We find that the isoperimetric profile function is discontinuous, and that the extremal domains have relatively simple polygonal boundaries. We discuss briefly the properties of minimal paths for the Sierpinski gasket, and the isodiametric problem in the intrinsic metric.
45.
In this paper, we investigate the limiting behavior of increments of the uniform empirical process. More precisely, we are concerned by sets of exceptional oscillation points related to large and small increments. We prove that these sets are random fractals and evaluate their Hausdorff dimensions. This work is a complement to the previous investigations carried out by Deheuvels and Mason(6) where Csörg–Révész–Stute-type increments are studied. 相似文献
46.
Spinelli G 《Nonlinear dynamics, psychology, and life sciences》2003,7(4):329-361
Heterochromatin represents 30% of eukaryotic genome in Drosophila and 15% in humans. Despite extensive research spanning many decades, its evolutionary significance, as well as the forces that guarantee its maintenance, are still elusive. Many theoretical and experimental approaches have led researchers to propose several conceptual frameworks to elucidate the nature of this huge mysterious genetic material and its spreading in all eukaryotic genomes. Junk DNA as well as selfish genetic material are two examples of such attempts, but several lines of evidence suggest that such explanations are incomplete. In fact, if the selfish DNA hypothesis does not explain the mapping of genetic functions in heterochromatin, then the junk DNA hypothesis is incomplete in describing both emergence of genetic functions and their maintenance in the eukaryotic heterochromatin. Recent developments in the physics of complex systems and mathematical concepts such as fractals provide new conceptual clues to answer several basic questions concerning the emergence of heterochromatin in eukaryotic genomes, its evolutionary significance, the forces that guarantee its maintenance, and its peculiar behavior in the eukaryotic cell. The aim of this paper is to provide a new theoretical framework for the heterochromatin, considering such genetic material in physical terms as a complex adaptive system. We apply some computer calculations to demonstrate the nonlinearity of the flux of genetic information along the phylogenic tree. Fractal dimensions of representative heterochromatic sequences are provided. A theory is proposed in which heterochromatin is considered a system that evolves in a self-organized manner at the edge of cellular and environmental chaos. 相似文献
47.
Ajit Sadana 《Applied biochemistry and biotechnology》1998,73(2-3):89-112
The diffusion-limited binding kinetics of antigen (analyte), in solution with antibody (receptor) immobilized on a biosensor
surface, is analyzed within a fractal framework. Most of the data presented is adequately described by a single-fractal analysis.
This was indicated by the regression analysis provided by Sigmaplot. A single example of a dual-fractal analysis is also presented.
It is of interest to note that the binding-rate coefficient (k) and the fractal dimension (Df) both exhibit changes in the same and in the reverse direction for the antigen-antibody systems analyzed. Binding-rate coefficient
expressions, as a function of the Df developed for the antigen-antibody binding systems, indicate the high sensitivity of thek on the Df when both a single- and a dual-fractal analysis are used. For example, for a single-fractal analysis, and for the binding
of antibody Mab 0.5β in solution to gpl20 peptide immobilized on a BIAcore biosensor, the order of dependence on the Df was 4.0926. For a dual-fractal analysis, and for the binding of 25-100 ng/mL TRITC-LPS (lipopolysaccharide) in solution with
polymyxin B immobilized on a fiberoptic biosensor, the order of dependence of the binding-rate coefficients, k1 and k2 on the fractal dimensions, Df1 and Df2, were 7.6335 and-11.55, respectively. The fractional order of dependence of thek(s) on the Df(s) further reinforces the fractal nature of the system. Thek(s) expressions developed as a function of the Df(s) are of particular value, since they provide a means to better control biosensor performance, by linking it to the heterogeneity
on the surface, and further emphasize, in a quantitative sense, the importance of the nature of the surface in biosensor performance. 相似文献
48.
Yu. I. Aristov N. Lisitsa V. I. Zaikovski J. Lorenc A. B. Jarzebski 《Reaction Kinetics and Catalysis Letters》1996,58(2):367-375
A fractal analysis of three base catalyzed silica aerogels was performed using different experimental techniques: image analysis of electron micrographs, SAXS and study of pore size distribution determined from nitrogen adsorption isotherms. The aerogels appeared to exhibit self-similar properties over the range from 3–10 to 50–130 nm. The values of mass fractal dimension varied from 1.75 to 2.05 depending on the reactants concentration (TEOS, H2O) and were found to be similar irrespective of the method applied. 相似文献
49.
We investigate the multi-scale structure of a tree network obtained by constructal theory and we propose a new geometrical framework to quantify deviations from scale invariance observed in many fields of physics and life sciences. We compare a constructally deduced fluid distribution network and one based on an assumed fractal algorithm. We show that: (i) the fractal network offers lower performance than the constructal object, and (ii) the constructal object exhibits a parabolic scaling explained in the context of the entropic skins geometry based on a scale diffusion equation in the scale space. Constructal optimization is equivalent to an equipartition of scale entropy production over scale space in the context of entropic skins theory. The association of constructal theory with entropic skins theory promises a deterministic theory to explain and build optimal arborescent structures. 相似文献
50.
We show the Talbot effect for Cantor transmittances, which are obtained as a product superposition of periodic components. The self-images for each periodic component can be superimposed with the self-images or the optical noise corresponding to the remaining components. Due to the integer scaling factor among periodic components, there are also self-images positions for the complete fractal structure. 相似文献