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701.
702.
In this paper, we present the conception of the multidimensional self-affine distribution and show that the multidimensional self-affine distribution possesses the fractal property of scale-invariance under truncation, which means that theoretical study of fractals has expanded from univariate cases to multivariate cases. Application of the multidimensional self-affine distribution is illustrated by means of geochemical Au and Ag elements data sets. The fractal dimension is a parameter which can quantitatively explain the variation of geochemical elements data on some orientation. This method is applied to Au data and Ag data, but also suited for other geochemical elements data or geological data. Theory of multivariate fractal can be applied for the study of change courses of fractal system, that is, fractal dynamics. 相似文献
703.
石志强 《华东地质学院学报》2002,25(1):88-89
简述了以ORACLE数据库为后台数据库、VB6为编程工具的用电营配管理信息多媒体查询系统的一些技术概念,介绍了C/S模式和方法,以便更好地阐述用电营配管理信息查询系统是如何通过多媒体技术来实现的。 相似文献
704.
705.
Despite persistent images to the contrary, most fieldworkers are accompanied. Yet, there has been limited discussion on the nature of accompanied fieldwork, particularly by geographers. Drawing on our experiences in three countries in the tropics, we discuss the dynamics of being accompanied in “the field” by our children and female co‐researchers. Specifically, we focus on issues of access and rapport; the impacts of their presence on our positionality; and the implications these have for power relations and research outcomes. We demonstrate how being accompanied entangles our personal and professional selves and can result in more egalitarian power relations as we become “observers observed”. We argue that by paying attention to the dynamics of accompanied fieldwork, there is the potential to enhance the conceptual focus of our methodological concerns and to provide a more theoretically sophisticated mode of exploring the ways in which our multiple identities intersect while in “the field”. 相似文献
706.
Chih Ted YANG Manager Sedimentation River Hydraulics Group. Technical Service Center U.S. Bureau of Reclamation. P.O. Box D- Denver CO U.S.A. 《国际泥沙研究》2002,17(1)
1 INTRODUCTION There are three basic energy dissipation rate approaches used for the derivation of sediment transport functions. They are the gravitational power theory by Velikanov (1954), the stream power theory by Bagnold (1966), and the unit stream power theory by Yang (1973, 1979, 1984, and 1986). The theoretical basis of these approaches has been summarized by Yang (1996) in his book, Sediment Transport Theory and Practice. Yang also made comparisons of the three basic approa… 相似文献
707.
Chuan-Yi WANG Jau-Yau LU Chih-Chiang SU Associate professor Dept. of Hydraulic Engrg. Feng-Chia University Taichung Taiwan China. E-mail: cywang@fcu.edu.tw Professor Dept. of Civil Engrg. National Chung-Hsing University Taichung 《国际泥沙研究》2002,17(2)
1 INTRODUCTION There are 129 rivers in Taiwan. Most of them are short and steep with small drainage basins and rapid flows. Heavy rains and flood flows usually carry large amount of sediment. The specific peak discharge (peak discharge per unit drainage area) in Taiwan has the highest value in the world. For example, the specific peak discharge of Wu River in central Taiwan is 10.5 cms/km2, which is about 618 times that of Yangtze River in China and 35 times that of Sinno River i… 相似文献
708.
New anisotropic covariance models and estimation of anisotropic parameters based on the covariance tensor identity 总被引:2,自引:0,他引:2
Many heterogeneous media and environmental processes are statistically anisotropic. In this paper we focus on range anisotropy,
that is, stochastic processes with variograms that have direction dependent correlation lengths and direction independent
sill. We distinguish between two classes of anisotropic covariance models: Class (A) models are reducible to isotropic after
rotation and rescaling operations. Class (B) models can be separated into a product of one-dimensional functions oriented
along the principal axes. We propose a new Class (A) model with multiscale properties that has applications in subsurface
hydrology. We also present a family of Class (B) models based on non-Euclidean distance metrics that are generated by superellipsoidal
functions. Next, we propose a new method for determining the orientation of the principal axes and the degree of anisotropy,
i.e., the ratio(s) of the correlation lengths. This information reduces the degrees of freedom of anisotropic variograms and
thus simplifies the estimation procedure. In particular, Class (A) models are reduced to isotropic and Class (B) models to
one-dimensional functions. Our method is based on an explicit relation between the second-rank slope tensor (SRST), which
can be estimated from the data, and the covariance tensor. The procedure is conceptually simple and numerically efficient.
It is more accurate for regular (on-grid) data distributions, but it can also be used for sparse (off-grid) spatial distributions.
In the case of non-differentiable random fields the method can be extended using generalized derivatives. We illustrate its
implementation with numerical simulations. 相似文献
709.
商圈惠顾行为的空间衰减:幂律模式还是指数模式 总被引:1,自引:0,他引:1
以上海市商业中心为例,基于匿名手机信令数据,运用引力模型对商圈惠顾行为的衰减模式及其系数进行了验证与对比。结果表明,① 对于商圈惠顾行为,最常用的2种距离衰减函数均具有较高的拟合优度,幂律函数稍优于指数函数;② 总体来看,距离仍是影响城市居民商圈惠顾行为的关键因素,距离衰减效应呈现出随商业中心等级增大而减弱的梯度特征,幂律型衰减系数取值1~3不等,采用既定系数1或2会过高/低估计商圈辐射能力;③ 不可忽视闲暇时间对商圈惠顾行为的约束作用,与周末相比,工作日的距离衰减系数较大,且商业中心等级越低,商圈惠顾行为的衰减性越显著。 相似文献
710.
世界地理结构与美国的全球战略及军力设计 总被引:3,自引:1,他引:2
本文旨在阐明世界地理结构在大国战略制定及军力设计中的基础性作用,以助于认识中国全球发展道路上面临的地缘安全风险和机遇。由于世界陆地、人口和经济活动相对集中于东半球特别是欧亚大陆,欧亚大陆历来是世界大国逐鹿的中心舞台。美国作为人类历史上第一个非欧亚大陆上的霸权国家,一直把防范欧亚大陆上出现区域性霸权作为国家安全的最高目标。本文从世界地理结构及其动态变化的角度,分析东半球尤其是欧亚大陆孕育世界大国和人类文明的地理优势,解析美国的地理区位对其早期崛起的影响,以及在这一地理条件下其全球战略的形成,并重点探讨美国基于防范欧亚大陆出现区域性霸权的全球军力设计。文章最后指出,在中美战略博弈中,位于欧亚大陆东缘的中国具有天然的地缘优势。 相似文献