全文获取类型
收费全文 | 7378篇 |
免费 | 1103篇 |
国内免费 | 1039篇 |
专业分类
测绘学 | 2043篇 |
大气科学 | 1133篇 |
地球物理 | 1985篇 |
地质学 | 1492篇 |
海洋学 | 819篇 |
天文学 | 478篇 |
综合类 | 730篇 |
自然地理 | 840篇 |
出版年
2024年 | 22篇 |
2023年 | 86篇 |
2022年 | 161篇 |
2021年 | 228篇 |
2020年 | 255篇 |
2019年 | 330篇 |
2018年 | 221篇 |
2017年 | 305篇 |
2016年 | 337篇 |
2015年 | 357篇 |
2014年 | 394篇 |
2013年 | 458篇 |
2012年 | 461篇 |
2011年 | 491篇 |
2010年 | 386篇 |
2009年 | 471篇 |
2008年 | 406篇 |
2007年 | 510篇 |
2006年 | 488篇 |
2005年 | 381篇 |
2004年 | 331篇 |
2003年 | 305篇 |
2002年 | 254篇 |
2001年 | 247篇 |
2000年 | 187篇 |
1999年 | 183篇 |
1998年 | 248篇 |
1997年 | 141篇 |
1996年 | 139篇 |
1995年 | 131篇 |
1994年 | 131篇 |
1993年 | 110篇 |
1992年 | 80篇 |
1991年 | 53篇 |
1990年 | 42篇 |
1989年 | 67篇 |
1988年 | 33篇 |
1987年 | 31篇 |
1986年 | 16篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 1篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1954年 | 4篇 |
排序方式: 共有9520条查询结果,搜索用时 9 毫秒
31.
32.
33.
34.
Modelling Positional Uncertainty of Line Features by Accounting for Stochastic Deviations from Straight Line Segments 总被引:1,自引:0,他引:1
Sytze de Bruin 《Transactions in GIS》2008,12(2):165-177
The assessment of positional uncertainty in line and area features is often based on uncertainty in the coordinates of their elementary vertices which are assumed to be connected by straight lines. Such an approach disregards uncertainty caused by sampling and approximation of a curvilinear feature by a sequence of straight line segments. In this article, a method is proposed that also allows for the latter type of uncertainty by modelling random rectangular deviations from the conventional straight line segments. Using the model on a dense network of sub‐vertices, the contribution of uncertainty due to approximation is emphasised; the sampling effect can be assessed by applying it on a small set of randomly inserted sub‐vertices. A case study demonstrates a feasible way of parameterisation based on assumptions of joint normal distributions for positional errors of the vertices and the rectangular deviations and a uniform distribution of missed sub‐vertices along line segments. Depending on the magnitudes of the different sources of uncertainty, not accounting for potential deviations from straight line segments may drastically underestimate the positional uncertainty of line features. 相似文献
35.
36.
Dynamic data integration for structural modeling: model screening approach using a distance-based model parameterization 总被引:2,自引:0,他引:2
This paper proposes a novel history-matching method where reservoir structure is inverted from dynamic fluid flow response.
The proposed workflow consists of searching for models that match production history from a large set of prior structural
model realizations. This prior set represents the reservoir structural uncertainty because of interpretation uncertainty on
seismic sections. To make such a search effective, we introduce a parameter space defined with a “similarity distance” for
accommodating this large set of realizations. The inverse solutions are found using a stochastic search method. Realistic
reservoir examples are presented to prove the applicability of the proposed method. 相似文献
37.
In this paper, we formulate a finite-element procedure for approximating the coupled fluid and mechanics in Biot’s consolidation
model of poroelasticity. We approximate the flow variables by a mixed finite-element space and the displacement by a family
of discontinuous Galerkin methods. Theoretical convergence error estimates are derived and, in particular, are shown to be
independent of the constrained specific storage coefficient, c
o
. This suggests that our proposed algorithm is a potentially effective way to combat locking, or the nonphysical pressure
oscillations, which sometimes arise in numerical algorithms for poroelasticity. 相似文献
38.
39.
Patterns of crystallographic preferred orientation are referred to as texture. The specific subject of texture analysis is
the experimental determination and interpretation of the statistical distribution of orientations of crystals within a specimen
of polycrystalline material, which could be metals or rocks. The objective is to relate an observed pattern of preferred orientation
to its generating processes and vice versa. In geosciences, texture of minerals in rocks is used to infer constraints on their
tectono-metamorphic history. Since most physical properties of crystals, such as elastic moduli, the coefficients of thermal
expansion, or chemical resistance to etching depends on crystal symmetry and orientation, the presence of texture imparts
directional properties to the polycrystalline material.
A major issue of mathematical texture analysis is the resolution of the inverse problem to determine a reasonable orientation
density function on SO(3) from measured pole intensities on
, which relates to the inverse of the totally geodesic Radon transform. This communication introduces a wavelet approach into
mathematical texture analysis. Wavelets on the two-dimensional sphere
and on the rotational group SO(3) are discussed, and an algorithms for a wavelet decomposition on both domains following the
ideas of Ta-Hsin Li is given. The relationship of these wavelets on both domains with respect to the totally geodesic Radon
transform is investigated. In particular, it is shown that the Radon transform of these wavelets on SO(3) are again wavelets
on
. A novel algorithm for the inversion of experimental pole intensities to an orientation density function based on this relationship
is developed. 相似文献
40.
在系统地分析了目前各种测震学地震预报方法科学思路的基础上,认为测震学地震预报方法基本上可以分为两大类。一类是以已经发生的一些地震作为未来可能发生的地震的“因”,即由于已经发生的地震对区域应力场的影响,导致未来发生较强地震。这一类包括的预报方法较多,如空区、条带、b值、地震迁移、相关地震等等及其由此衍生出来的各种方法。另一类是把已经发生的一些地震作为区域应力场增强的“果”,即已经发生的地震是区域应力场增强过程中的一种反映,而未来地震不一定是已经发生的地震所导致的结果。这一类包括“地震窗口”、小震群活动等方法。针对第一类方法,各种预报方法都是力图从地震三要素中提取未来地震的信息,而具体作法又都是利用地震三要素这个多维空间的某个剖面。为了从地震活动诸要素的多维空间提取综合信息,我们对每个地震加入了破裂面方位,构成了地震第四要素,并依据地震4要素建立了地震综合效应场函数。地震综合效应场函数概括了多种测震学地震预报方法的科学思路和预报经验,从而可以形成测震学的综合预报方法。 相似文献