全文获取类型
收费全文 | 1791篇 |
免费 | 269篇 |
国内免费 | 460篇 |
专业分类
测绘学 | 188篇 |
大气科学 | 239篇 |
地球物理 | 722篇 |
地质学 | 721篇 |
海洋学 | 387篇 |
天文学 | 29篇 |
综合类 | 118篇 |
自然地理 | 116篇 |
出版年
2024年 | 1篇 |
2023年 | 19篇 |
2022年 | 27篇 |
2021年 | 37篇 |
2020年 | 62篇 |
2019年 | 68篇 |
2018年 | 62篇 |
2017年 | 68篇 |
2016年 | 78篇 |
2015年 | 96篇 |
2014年 | 90篇 |
2013年 | 165篇 |
2012年 | 102篇 |
2011年 | 102篇 |
2010年 | 102篇 |
2009年 | 112篇 |
2008年 | 126篇 |
2007年 | 134篇 |
2006年 | 139篇 |
2005年 | 111篇 |
2004年 | 113篇 |
2003年 | 100篇 |
2002年 | 69篇 |
2001年 | 60篇 |
2000年 | 64篇 |
1999年 | 56篇 |
1998年 | 51篇 |
1997年 | 40篇 |
1996年 | 40篇 |
1995年 | 41篇 |
1994年 | 32篇 |
1993年 | 25篇 |
1992年 | 18篇 |
1991年 | 20篇 |
1990年 | 13篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有2520条查询结果,搜索用时 451 毫秒
61.
62.
中国地质统计学(空间信息统计学)发展的回顾与前景 总被引:23,自引:0,他引:23
讨论了地质统计学(空间信息统计学)发展的若干问题,其内容包括4部分:1.地质统计学的理论及方法;2.关于软件系统的现状;3.关于实际应用;4.地质统计学发展前景的若干看法。 相似文献
63.
This paper designs three quasi-geostrophic barotropic models with a radial/horizontal grid length being 2 kin,one in the polar coordinates,one on a stationary typhoon circulation condition and another on a non-stationary typhoon circulation condition in the Cartesian coordinates,to investigate the effects of azimuthal and radial linear advections,and nonlinear advection on the inward propagation of mesoscale vorticity and the changes of typhoon intensity.Results show that the azimuthal linear advection may result in the formation of spiral vorticity bands;the radial linear advection in a certain parameter set is able to transfer vorticity inwards,leading to a slight enhancement of typhoon;the nonlinear advection of perturbation vorticity on a stationary typhoon circulation condition may transfer more vorticities inwards,thus resulting in a distinct enhancement of typhoon;and the nonlinear advection on a non-stationary typhoon circulation condition possesses duality,i.e.on the one hand,the advection increases the vorticity of inward propagation,thus favorable to the intensification of typhoon,and on the other hand,in the inward propagation process of vorticity the originally concentric and axisymmetric structure of typhoon basic flow is damaged,and a complex flow pattern forms,which in turn tends to weaken the circulation of typhoon.At last the paper discusses the possible applications of those results in typhoon intensity prediction. 相似文献
64.
65.
地貌单位线(GIUH)基于流域地貌特征和概率方法,在我国许多地区得到广泛应用。针对面雨量分布不均问题,通过分析初始概率的变化,考虑GIUH的非线性改正,并用实际资料进行了验证。 相似文献
66.
Improving Sequential Simulation with a Structured Path Guided by Information Content 总被引:1,自引:0,他引:1
Multiple-point simulation is a newly developed geostatistical method that aims at combining the strengths of two mainstream geostatistical methods: object-based and pixel-based methods. It maintains the flexibility of pixel-based algorithms in data conditioning, while enhancing its capability of reproducing realistic geological shapes, which is traditionally reserved to object-based algorithms. However, the current snesim program for multiple-point simulation has difficulty in reproducing large-scale structures, which have a significant impact on the flow response. To address this problem, we propose to simulate along a structured path based on an information content measure. This structured path accounts for not only the information from the data, but also some prior structural information provided by geological knowledge. Various case studies show a better reproduction of large-scale structures. This concept of simulating along a structured path guided by information content can be applied to any sequential simulation algorithms, including traditional variogram-based two-point geostatistical algorithms. 相似文献
67.
Indicator Simulation Accounting for Multiple-Point Statistics 总被引:7,自引:0,他引:7
Geostatistical simulation aims at reproducing the variability of the real underlying phenomena. When nonlinear features or large-range connectivity is present, the traditional variogram-based simulation approaches do not provide good reproduction of those features. Connectivity of high and low values is often critical for grades in a mineral deposit. Multiple-point statistics can help to characterize these features. The use of multiple-point statistics in geostatistical simulation was proposed more than 10 years ago, on the basis of the use of training images to extract the statistics. This paper proposes the use of multiple-point statistics extracted from actual data. A method is developed to simulate continuous variables. The indicator kriging probabilities used in sequential indicator simulation are modified by probabilities extracted from multiple-point configurations. The correction is done under the assumption of conditional independence. The practical implementation of the method is illustrated with data from a porphyry copper mine. 相似文献
68.
基于非线性平差模型的坐标转换公式 总被引:4,自引:2,他引:4
用线性近似法以及非线性参数估计法讨论了直角坐标系七参数转换模型,指出改进的Gauss-Newton方法具有理论严密、计算简洁、易于编程、精度较高等持点。对于处理类似坐标转换的非线性模型具有重要的理论和实践意义。 相似文献
69.
It has been well studied that the γ-function explicit method can be effective in providing favorable numerical dissipation for linear elastic systems. However, its performance for nonlinear systems is unclear due to a lack of analytical evaluation techniques. Thus, a novel technique is proposed herein to evaluate its efficiency for application to nonlinear systems by introducing two parameters to describe the stiffness change. As a result, the numerical properties and error propagation characteristics of the γ-function explicit method for the pseudodynamic testing of a nonlinear system are analytically assessed. It is found that the upper stability limit decreases as the step degree of nonlinearity increases; and it increases as the current degree of nonlinearity increases. It is also shown that this integration method provides favorable numerical dissipation not only for linear elastic systems but also for nonlinear systems. Furthermore, error propagation analysis reveals that the numerical dissipation can effectively suppress the severe error propagation of high frequency modes while the low frequency responses are almost unaffected for both linear elastic and nonlinear systems. 相似文献
70.
Introduction The velocity field of surface plate motion can be split into a poloidal and a toroidal parts.At the Earth′s surface,the toroidal component is manifested by the existence of transform faults,and the poloidal component by the presence of convergence and divergence,i.e.spreading and subduc-tion zones.They have coupled each other and completely depicted the characteristics of plate tec-tonic motions.The mechanism of poloidal field has been studied fairly clearly which is related to … 相似文献