全文获取类型
收费全文 | 140篇 |
免费 | 2篇 |
国内免费 | 10篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 3篇 |
地球物理 | 27篇 |
地质学 | 45篇 |
海洋学 | 4篇 |
天文学 | 3篇 |
综合类 | 1篇 |
自然地理 | 67篇 |
出版年
2022年 | 1篇 |
2019年 | 2篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 1篇 |
2013年 | 7篇 |
2012年 | 4篇 |
2011年 | 2篇 |
2010年 | 5篇 |
2009年 | 3篇 |
2008年 | 4篇 |
2007年 | 10篇 |
2006年 | 6篇 |
2005年 | 8篇 |
2004年 | 1篇 |
2003年 | 5篇 |
2002年 | 3篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 11篇 |
1996年 | 13篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 3篇 |
排序方式: 共有152条查询结果,搜索用时 15 毫秒
1.
On the practice of estimating fractal dimension 总被引:11,自引:0,他引:11
Coastlines epitomize deterministic fractals and fractal (Hausdorff-Besicovitch) dimensions; a divider [compass] method can be used to calculate fractal dimensions for these features. Noise models are used to develop another notion of fractals, a stochastic one. Spectral and variogram methods are used to estimate fractal dimensions for stochastic fractals. When estimating fractal dimension, the objective of the analysis must be consistent with the method chosen for fractal dimension calculation. Spectal and variogram methods yield fractal dimensions which indicate the similarity of the feature under study to noise (e.g., Brownian noise). A divider measurement method yields a fractal dimension which is a measure of complexity of shape. 相似文献
2.
Abstract. Growth of the shallow-water gorgonian Lophogorgia ceratophyta was investigated in an infralittoral station located in La Spezia Gulf, Ligurian Sea. Mean annual height growth rate was estimated to be 2.57 cm · a-1. The fractal dimension of the colonies was found to gradually evolve in complexity, exhibiting a simpler branching pattern in younger specimens. The maintenance of a low, invariable ramification complexity as an optimal choice in managing relationships between water and the colony's living tissues is also discussed. 相似文献
3.
Rescaled-range and power spectrum analyses on well-logging data 总被引:6,自引:0,他引:6
Chun-Feng Li 《Geophysical Journal International》2003,153(1):201-212
4.
We use high resolution Monte Carlo simulations to study the dispersive mixing in two-phase, immiscible, porous media flow that results from the interaction of the nonlinearities in the flow equations with geologic heterogeneity. Our numerical experiments show that distinct dispersive regimes occur depending on the relative strength of nonlinearity and heterogeneity. In particular, for a given degree of multiscale heterogeneity, controlled by the Hurst exponent which characterizes the underlying stochastic model for the heterogeneity, linear and nonlinear flows are essentially identical in their degree of dispersion, if the heterogeneity is strong enough. As the heterogeneity weakens, the dispersion rates cross over from those of linear heterogeneous flows to those typical of nonlinear homogeneous flows. 相似文献
5.
We evaluate the complete spectrum of the generalized fractal dimension of the spatial pattern of microearthquakes in Southern Italy, revealing a multifractal distribution structure. Our analysis is focused on the dependence of the multifractal distribution on the size of the selected area and the kind of seismicity in the area. As the size of the window varies, we observe that the capacity, information and correlation dimensions vary significantly, while both d ∞ and d −infin; remain unchanged within their errors limits. We interpret this result in terms of the observation that our data are mainly clustered around a linear fault (the Sisifo fault). When we restrict the selected windows around the fault, clustering around a line (the fault) is highlighted. The capacity dimension changes from about 1.8 to about 1.4 and the correlation dimension decreases because we observe in detail the clustering of the seismicity along the fault, which approximates the maximum intense clustering of the whole data set. Although our results are strongly influenced by the fact that the data are dominated by the epicentres located on the fault, we can conclude that multifractal analysis can be a very useful tool to discriminate the seismicity linked to a particular fault in a given area. 相似文献
6.
Multifractal modeling and spatial statistics 总被引:9,自引:0,他引:9
In general, the multifractal model provides more information about measurements on spatial objects than a fractal model. It also results in mathematical equations for the covariance function and semivariogram in spatial statistics which are determined primarily by the second-order mass exponent. However, these equations can be approximated by power-law relations which are comparable directly to equations based on fractal modeling. The multifractal approach is used to describe the underlying spatial structure of De Wijs 's example of zinc values from a sphalerite-bearing quartz vein near Pulacayo, Bolivia. It is shown that these data are multifractal instead of fractal, and that the second-order mass exponent (=0.979±0.011 for the example) can be used in spatial statistical analysis. 相似文献
7.
Johannes Bruining Diederik van Batenburg Larry W. Lake An Ping Yang 《Mathematical Geology》1997,29(6):823-848
Random field generators serve as a tool to model heterogeneous media for applications in hydrocarbon recovery and groundwater
flow. Random fields with a power-law variogram structure, also termed fractional Brownian motion (fBm) fields, are of interest
to study scale dependent heterogeneity effects on one-phase and two-phase flow. We show that such fields generated by the
spectral method and the Inverse Fast Fourier Transform (IFFT) have an incorrect variogram structure and variance. To illustrate
this we derive the prefactor of the fBm spectral density function, which is required to generate the fBm fields. We propose
a new method to generate fBm fields that introduces weighting functions into the spectral method. It leads to a flexible and
efficient algorithm. The flexibility permits an optimal choice of summation points (that is points in frequency space at which
the weighting function is calculated) specific for the autocovariance structure of the field. As an illustration of the method,
comparisons between estimated and expected statistics of fields with an exponential variogram and of fBm fields are presented.
For power-law semivariograms, the proposed spectral method with a cylindrical distribution of the summation points gives optimal
results. 相似文献
8.
9.
10.
城市地理研究中的单分形、多分形和自仿射分形 总被引:1,自引:0,他引:1
分形几何学在城市地理研究中具有广泛的应用,然而很多基本概念却让初学者感到迷惑。如何区分单分形、自仿射分形与多分形,是一个基本而重要的问题。简单分形容易理解,而真实的地理现象很少是单分形的。城市生长过程具有自仿射特征,而城市空间格局却具有多分形性质。作者发现,各种分形的共性在于三个方面:标度律、分数维和熵守恒。论文基于标度、分维和熵守恒公式,借助隐喻城市生长的规则分形来区分单分形、多分形和自仿射分形,讨论分形系统演化的机理、分形与空间自相关和空间异质性的联系,同时澄清一些在地理分形研究中的常见错误概念。最后以城市位序-规模分布为例,说明并对比单分形和多分形在城市地理研究中的建模与应用思路。 相似文献