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81.
82.
In geographical research the data of interest are often in the form of counts. Standard regression analysis is inappropriate for such data, but if certain assumptions are met, a form of regression based on the Poisson distribution can be used. This paper illustrates the use of Poisson regression in the computer package GLIM with an example from historical geography. Apprentice migration to Edinburgh is regressed on a combination of categorical, count, and continuous explanatory variables. 相似文献
83.
This paper deals with a method for detection of local geoid deformations; as a consequence, the methods main application concerns geoid adjustment to GPS/levelling points. This is based on the fact that these points should present no local geoid deformation to avoid errors in the adjustments. These type of miscalculations would lead to an incorrect adjustment and result in further errors in subsequent studies with GPS in the proximity at the point with local deformation.The method proposed is based on predictions of gravity disturbance from geoid undulations using Poisson integral with modified kernel, and its comparison with the gravity disturbance from GPS and gravimetric observations.The use of gravity disturbance instead of gravity anomalies has been chosen since gravity disturbance is a quantity derived from GPS and not from levelling. The loss of accuracy arising with a local height reference system is therefore theoretically avoided as far as the differences in geodetic reference systems regarding positions of gravity measurements and coefficients of the global models are accounted for.Extended numerical tests using computed geoidal undulations and the corresponding gravity disturbances obtained from the geopotential model GPM98cr computed up to degree 720 illustrate the validity of the proposed method and its usefulness as local geoid deformations detection tool.Finally, the method is tested using real GPS/Gravimetric data and geoid models IBERGEO95 and EGG97 with good results. 相似文献
84.
莺琼盆地岩石弹性物性规律的研究 总被引:4,自引:1,他引:3
利用岩芯实验室测试数据、全波列测井数据和地震资料对莺琼盆地纵横波地震参数及衍生参数的变化规律进行了详尽地分析和研究。含气岩芯的刚性模量、纵横波速度比和泊松比比含盐水岩芯的低得多;砂岩的纵横波速度比和泊松比比泥岩的低得多。当地层埋深超过2500m时,纵横波速度比、泊松比基本不受深度的影响。岩石密度和孔隙度的相关性很好;含盐水岩芯的纵横波速度比与孔隙度的相关性很差;含气岩芯的纵横波速度比与孔隙度的相关性稍好于含盐水岩芯;高温高压状态下的纵横波速度比和泊松比的变化也是有规律的。 相似文献
85.
v_p/v_s ESTIMATION IN TIBETAN CRUST FROM INVERSION OF SURFACE WAVE DISPERSIONS 相似文献
86.
87.
Jamie E. Padgett 《地震工程与结构动力学》2011,40(15):1743-1761
Deteriorating highway bridges in the United States and worldwide have demonstrated susceptibility to damage in earthquake events, with considerable economic consequences due to repair or replacement. Current seismic loss assessment approaches for these critical elements of the transportation network neglect the effects of aging and degradation on the loss estimate. However, the continued aging and deterioration of bridge infrastructure could not only increase susceptibility to seismic damage, but also have a significant impact on these economic losses. Furthermore, the contribution of individual aging components to system‐level losses, correlations between these components, and uncertainty modeling in the risk assessment and repair modeling are all crucial considerations to enhance the accuracy and confidence in bridge loss estimates. In this paper, a new methodology for seismic loss assessment of aging bridges is introduced based on the non‐homogeneous Poisson process. Statistical moments of seismic losses can be efficiently estimated, such as the expected value and variance. The approach is unique in its account for time‐varying seismic vulnerability, uncertainty in component repair, and the contribution of multiple correlated aging components. A representative case study is presented with two fundamentally distinct highway bridges to demonstrate the effects of corrosion deterioration of different bridge components on the seismic losses. Using the proposed model, a sensitivity study is also conducted to assess the effect of parameter variations on the expected seismic losses. The results reveal that the seismic losses estimated by explicitly considering the effects of deterioration of bridge components is significantly higher than that found by assuming time‐invariant structural reliability. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
88.
Multiple-expert hazard/risk assessments have considerable precedent, particularly in the Yucca Mountain site characterization
studies. A certain amount of expert knowledge is needed to interpret the geological data used in a probabilistic data analysis.
As may be the situation in science, experts disagree on crucial points. Consequently, lack of consensus in some studies is
a sure outcome. In this paper, we present a Bayesian approach to statistical modeling in volcanic hazard assessment for the
Yucca Mountain site. Specifically, we show that the expert opinion on the site disruption parameterp is incorporated into the prior distribution, π(p), based on geological information that is available. Moreover, π(p) can
combine all available geological information motivated by conflicting but realistic arguments (e.g., simulation, cluster analysis,
structural control, ..., etc.). The incorporated uncertainties about the probability of repository disruptionp
eventually will be averaged out by taking the expectation over π(p). We use the following priors in the analysis: (1) priors
selected for mathematical convenience: Beta (r,s) for (r,s) = (2, 2), (3, 3), (5, 5), (2, 1),(2, 8), (8, 2), and (1, 1);and (2) three priors motivated by expert knowledge. Sensitivity analysis is performed for each prior distribution. Our study
concludes that estimated values of hazard based on the priors selected for mathematical simplicity are uniformly higher than
those obtained based on the priors motivated by expert knowledge. And, the model using the prior, Beta (8, 2), yields the
highest hazard (=2.97 × 10-2
. The minimum hazard is produced by the “three-expert prior” (i.e., values of
p
are equally likely for
p = 10-3, 10-2,and 10-1
. The estimate of the hazard is 1.39 × 10-3, which is only about one order of magnitude smaller than the maximum value. The term, “hazard, ” is defined as the probability
of at least one disruption of a repository at the Yucca Mountain site by basaltic volcanism for the next 10,000 years. 相似文献
89.
Abstract One of the basic tasks in geomorphologic analysis is to know the probability distributions of the stream lengths of different orders. In practical applications, this information is useful for basin rainfall-runoff modelling. The objective of this study is to determine the length distributions of the Strahler streams. A Poisson process was used to derive the theoretical distributions. The result showed that the length distribution of the first-order stream is an exponential distribution and the second-order or higher order stream length is a gamma distribution. In order to verify the theoretical distributions, a digital elevation model (DEM) was adopted to calculate the stream lengths of four basins in Taiwan. Kolmogorov-Smirnov and chi-square tests were used to test the goodness-of-fit of the data. Results showed that the length distributions of the first- and second-order streams analysed by using DEM correspond with those from the derived distribution method. 相似文献
90.
为了扩大洪水信息,提高洪水模拟精度,研究超定量洪水频率分析模型。介绍了洪水超定量模型的基本理论,假设超定量洪水年发生次数服从Poisson分布,超定量洪水系列服从广义Pareto(GP)分布,给出年最大超定量洪水分布和超定量洪水重现期的计算方法,提出通过模型拟合优度检验来综合确定超定量系列阈值的方法。将超定量模型应用在海河流域小觉站洪峰频率分析中,结果表明:通过模型拟合优度检验确定超定量系列阈值的方法有效且可靠,洪水超定量系列年平均发生次数服从Poisson分布,GP分布洪峰设计值略大于P-Ⅲ分布洪峰设计值,应用在水利工程设计及风险分析中是偏安全的。 相似文献