全文获取类型
收费全文 | 325篇 |
免费 | 31篇 |
国内免费 | 34篇 |
专业分类
测绘学 | 21篇 |
大气科学 | 50篇 |
地球物理 | 167篇 |
地质学 | 84篇 |
海洋学 | 37篇 |
天文学 | 3篇 |
综合类 | 7篇 |
自然地理 | 21篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 6篇 |
2020年 | 12篇 |
2019年 | 10篇 |
2018年 | 7篇 |
2017年 | 17篇 |
2016年 | 14篇 |
2015年 | 11篇 |
2014年 | 21篇 |
2013年 | 34篇 |
2012年 | 11篇 |
2011年 | 29篇 |
2010年 | 16篇 |
2009年 | 33篇 |
2008年 | 37篇 |
2007年 | 27篇 |
2006年 | 23篇 |
2005年 | 14篇 |
2004年 | 10篇 |
2003年 | 13篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 6篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1984年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有390条查询结果,搜索用时 46 毫秒
71.
Hwong-wen Ma 《Stochastic Environmental Research and Risk Assessment (SERRA)》2000,14(3):195-206
The selection of optimal management strategies for environmental contaminants requires detailed information on the risks
imposed on populations. These risks are characterized by both inter-subject variability (different individuals having different
levels of risk) and by uncertainty (there is uncertainty about the risk associated with the Yth percentile of the variability distribution). In addition, there is uncertainty introduced by the inability to agree fully
on the appropriate decision criteria. This paper presents a methodology for incorporating uncertainty and variability into
a multi-medium, multi-pathway, multi-contaminant risk assessment, and for placing this assessment into an optimization framework
to identify optimal management strategies. The framework is applied to a case study of a sludge management system proposed
for North Carolina and the impact of stochasticity on selection of an optimal strategy considered. Different sets of decision
criteria reflecting different ways of treating stochasticity are shown to lead to different selections of optimal management
strategies. 相似文献
72.
Abstract Many data structures are possible for the storage of topological information for computer-based maps. The PAN graph is here suggested as an aid in the selection of a strategy appropriate to the application. Examples are given for the mapping of triangular networks and Thiessen polygons. Application of the technique is appropriate to both education in, and design of, spatial data structures for automated cartography and geographical information systems 相似文献
73.
致密油气层的物性(孔隙度和渗透率)较差.针对致密储层,目前常用的氦气法孔隙度测量方法存在两个不足:器壁压变性参数G定义不明确;膨胀前压力设置普遍偏小.本次基于氦气法孔隙度测量装置岩心室的应力应变力学分析和不确定度理论分析,开发了一种面向致密储层的氦孔隙度测量方法.本次提出的方法给出了器壁压变性参数G的解析式,并基于G的解析式推导出了新的孔隙度计算公式,将刻度系数减少到1个,简化了刻度过程.其次,基于不确定度理论得到的孔隙度测量不确定度表明:氦气法测量致密储层孔隙度的膨胀前压力大于2 MPa基本可以将孔隙度绝对误差控制在0.5%以内.与高压压汞法孔隙度测量结果对比发现,该方法测量孔隙度的相对偏差在14%以内,远低于常规氦气法测量孔隙度的相对偏差(50%). 相似文献
74.
Prediction of coastal hazards due to climate change is fraught with uncertainty that stems from complexity of coastal systems, estimation of sea level rise, and limitation of available data. In-depth research on coastal modeling is hampered by lack of techniques for handling uncertainty, and the available commercial geographical information systems (GIS) packages have only limited capability of handling uncertain information. Therefore, integrating uncertainty theory with GIS is of practical and theoretical significance. This article presents a GIS-based model that integrates an existing predictive model using a differential approach, random simulation, and fuzzy set theory for predicting geomorphic hazards subject to uncertainty. Coastal hazard is modeled as the combined effects of sea-level induced recession and storm erosion, using grid modeling techniques. The method is described with a case study of Fingal Bay Beach, SE Australia, for which predicted responses to an IPCC standard sea-level rise of 0.86 m and superimposed storm erosion averaged 12 m and 90 m, respectively, with analysis of uncertainty yielding maximum of 52 m and 120 m, respectively. Paradoxically, output uncertainty reduces slightly with simulated increase in random error in the digital elevation model (DEM). This trend implies that the magnitude of modeled uncertainty is not necessarily increased with the uncertainties in the input parameters. Built as a generic tool, the model can be used not only to predict different scenarios of coastal hazard under uncertainties for coastal management, but is also applicable to other fields that involve predictive modeling under uncertainty. 相似文献
75.
在无真实观测值的情况下,本文利用广义三角帽方法评估了五种GRACE时变重力场模型(CSR、GFZ、GRGS、HUST发布的球谐系数解和JPL发布的Mascon解)反演中国大陆地区2003-2013年水储量变化的不确定性.研究结果表明,CSR、GFZ、JPL、HUST和GRGS反演月水储量变化不确定性的区域平均RMS分别为14.4 mm、26.3 mm、25.3 mm、26.6 mm和56.1 mm,其中GRGS的结果未恢复泄漏信号;在季和年尺度上,模型的不确定性均小于月尺度;扣除周期和趋势信号后,各模型反演结果更为一致.除长江流域外,CSR在13个流域的不确定性均小于其他模型,GRGS反演各流域水储量变化的不确定性通常较大,且可能高估了温带大陆性气候地区水储量的波动;CSR和JPL的不确定性受流域周边水文特征、气候类型、流域面积和形状的影响相对较小,不确定性变化范围分别为2.3~17.1 mm和5.6~22.5 mm,GFZ和HUST受影响较大,不确定性变化范围分别为5.5~35.1 mm和4.0~40.6 mm.本文的研究结果为GRACE产品不确定性评估提供了新的途径,为GRACE时变重力场模型的选取提供参考. 相似文献
76.
电热板加热消解法和微波消解法是目前海洋沉积物样品消解的常用方法。为了比较这两种处理方法对检测结果准确性的影响程度,文章依据《测量不确定度的评定与表示》技术规定中的相关要求对海洋沉积物中铜含量测定过程中采取的两种消解方法进行了不确定度评定与对比,建立了模型,并对各不确定度分量进行分析和量化,计算出两种消解方法测量沉积物中铜含量的相对合成不确定度分别为0.06721和0.04033,扩展不确定度分别为4.0mg/kg和2.4mg/kg。通过比较两种消解方法对测定结果不确定度的贡献,发现微波消解法明显优于电热板加热法。 相似文献
77.
Models under location uncertainty are derived assuming that a component of the velocity is uncorrelated in time. The material derivative is accordingly modified to include an advection correction, inhomogeneous and anisotropic diffusion terms and a multiplicative noise contribution. In this paper, simplified geophysical dynamics are derived from a Boussinesq model under location uncertainty. Invoking usual scaling approximations and a moderate influence of the subgrid terms, stochastic formulations are obtained for the stratified Quasi-Geostrophy and the Surface Quasi-Geostrophy models. Based on numerical simulations, benefits of the proposed stochastic formalism are demonstrated. A single realization of models under location uncertainty can restore small-scale structures. An ensemble of realizations further helps to assess model error prediction and outperforms perturbed deterministic models by one order of magnitude. Such a high uncertainty quantification skill is of primary interests for assimilation ensemble methods. MATLAB® code examples are available online. 相似文献
78.
本文概述了一维土层地震反应分析等效线性化方法评价结果不确定性研究的进展,比较了中美两国核设施土层地震反应分析中参数不确定性的处理方法。基于实测数据,令参数随机变化,建立土层剖面模型,采用随机振动理论方法,分析了土层动力特性、剪切波速、基岩地震动输入界面对评价结果的影响。结果表明,土层剪切波速的不确定性对评价结果影响最大,主要表现为加速度反应谱平台段的延长。对比参数随机变化模型和最佳估计模型的计算结果可知,随机振动理论反映了土层对基岩地震动的影响,将随机模型分析结果的中值加减1倍标准差基本可以包络最佳估计模型的分析结果。 相似文献
79.
80.
Uncertainty analysis and probabilistic segmentation of electrical resistivity images: the 2D inverse problem 下载免费PDF全文
Juan Luis Fernández‐Martínez Shan Xu Colette Sirieix Zulima Fernández‐Muniz Joëlle Riss 《Geophysical Prospecting》2017,65(Z1):112-130
In this paper, we present the uncertainty analysis of the 2D electrical tomography inverse problem using model reduction and performing the sampling via an explorative member of the Particle Swarm Optimization family, called the Regressive‐Regressive Particle Swarm Optimization. The procedure begins with a local inversion to find a good resistivity model located in the nonlinear equivalence region of the set of plausible solutions. The dimension of this geophysical model is then reduced using spectral decomposition, and the uncertainty space is explored via Particle Swarm Optimization. Using this approach, we show that it is possible to sample the uncertainty space of the electrical tomography inverse problem. We illustrate this methodology with the application to a synthetic and a real dataset coming from a karstic geological set‐up. By computing the uncertainty of the inverse solution, it is possible to perform the segmentation of the resistivity images issued from inversion. This segmentation is based on the set of equivalent models that have been sampled, and makes it possible to answer geophysical questions in a probabilistic way, performing risk analysis. 相似文献