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Sebastian H. Mernild M.Sc. & Ph.D. Bent Hasholt 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):13-25
A classification of watercourses proposed by Hasholt 1999 has been tested in Denmark using data from detailed field investigations from 42 watercourses and their surrounding area. Three types of landscapes are included: the moraine landscape from the Weichselian glaciation, the moraine landscape from the Saalian glaciation and the outwash plains. The performance of the classification in separating types of watercourses is discussed and modifications are suggested. 相似文献
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Sebastian B. Hammerschmidt Earl E. Davis Andre Hüpers Achim Kopf 《Geo-Marine Letters》2013,33(5):405-418
Along the Nankai Trough megasplay fault off SE Japan, the effect of fluid migration on subduction-related seismogenesis and tsunamigenesis remains unresolved. To investigate the existence and role of fluid flow, a SmartPlug borehole observatory was installed at Site C0010 of the Integrated Ocean Drilling Program NanTroSEIZE Kumano transect, where a shallow branch of the fault was intersected and in situ fluid pressure monitored from August 2009 to November 2010. The tidal signal in the formation showed no phase shift relative to seafloor loading. The attenuation of 0.73 reflects the loading efficiency accurately, and enabled calculation of a formation compressibility of 1.0×10–9 Pa–1 and a hydraulic diffusivity (HD) of 1.5×10–5 m2 s–1. A similar HD is predicted by a tidal response model based on SmartPlug pressure data. By contrast, permeability measurements on intact samples from Site C0004 SE along-strike the splay fault and from Site C0006 in the frontal thrust zone were found to be similar and one magnitude smaller respectively, despite having a higher porosity. This is explained by the presence of fractures, which are covered by the larger scale of in situ measurements at Site C0010. Consequently, HD can be set to be at least 10–5 m2 s–1 for the splay fault and 10–6 m2 s–1 for the frontal thrust fault zone. Considering recent publications makes fluid flow at the splay fault unlikely, despite the presence of fractures. If the influence of fractures is limited, then processes leading to fault weakening may be enhanced. 相似文献
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Natural processes generate spatial fields which reflect their specific properties. In this paper the effect of the direction of processes on the resulting spatial fields is investigated. This is done by extending the concept of reversibility used for time series to space. A novel copula based measure of asymmetry is defined which is an indicator of directional dependence. Contrary to traditional geostatistics where all points separated by a vector are considered irrespective of its sign, in this study the direction of the vector is also taken into consideration, leading to differences in the dependence corresponding to the vector \({\mathbf {h}}\) and \({-}{\mathbf {h}}\). The concept of directional dependence and the corresponding measure of asymmetry are defined using spatial copulas, and are thus independent of the scale of measurement. The result is a bivariate directional third-order moment based measure which can identify the direction in which the processes generating the spatial field acted. A statistical test to find the statistical significance of the asymmetry indicating directional dependence is presented. The methodology is tested on a number of synthetic and observed cases. Precipitation and groundwater quality parameters obtained using numerical models are first investigated. Regular dense grids obtained by numerical simulations show good correspondence between properties of the modeled processes and the new measure introduced. Measured variables observed on sparse irregular networks show similar behavior to the theoretical examples. Mean flow directions in groundwater and advection directions of precipitation fields can be detected from single snapshots. As a further example, dominant wind directions in the Sahara are found by investigating the digital terrain model. 相似文献
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Carolina Lauro Stella M. Moreiras Sebastian Junquera Ivan Vergara Rafael Toural Johannes Wolf Ruben Tutzer 《Environmental Earth Sciences》2017,76(5):213
The Central-West region of Argentina was seriously affected by a series of convective summer storms on January–February of 2013 generating many debris flows and rockfall in the Central Andes mountain regions. In particular, the unreported 8th February event caused the sad death of a 10-year-old child being completely ignored by society and local authorities. Despite this, meteorological conditions associated with this event and further episodes were rarely measured and determined mainly due to scarce meteorological stations in Andean mountain areas. In this paper, meteorological data from CMORPH algorithm and measurements of surrounding gauges were analyzed for estimating the triggering precipitation value of this event. As well, the particular debris flow channeled into the main branch of the Amarilla gully in the Agua Negra valley was geomorphologically described. The amount of precipitation associated with this debris flow was 5.5 and 13.2 mm accumulated previous to the event. This violent debris flow was generated in a talus zone in a periglacial environment located just below a covered rock glacier. However, the influence of the permafrost thawing in this process is not feasible. The altitude of the 0 °C isotherm was lower during the previous days of the event, and no monitoring on permafrost is available for this area. The volume of removed mass was estimated in 5 × 104 m3, and the mean velocity was 35 km/h. Boulders of 4 m diameter were found in the source area, while the deposit is up to 75% sandy with clasts that hardly exceed 10 cm in the alluvial fan distal part. Herein the main objective is to advice about the probable catastrophic impact of similar events in the future. These findings could be useful for hazard remediation, mitigation, and prevention plans for the Agua Negra international pass under construction. 相似文献
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While it is well-known that texture can be used to classify very high resolution (VHR) data, the limits of its applicability have not been unequivocally specified. This study examines whether it is possible to divide satellite images into two classes associated with “low” and “high” texture values in the initial stage of processing VHR images. This approach can be effectively used in object-oriented classification. Based on the panchromatic channel of KOMPSAT-2 images from five areas of Europe, datasets with down-sampled pixel resolutions of 1, 2, 4, 8, and 16 m were prepared. These images were processed using different texture analysis techniques in order to discriminate between basic land cover classes. Results were assessed using the normalized feature space distance expressed by the Jeffries–Matusita distance. The best results were observed for images with the highest resolution processed by the Laplacian filter. Our research shows that a classification approach based on the idea of “low” and “high” textures can be effectively applied to panchromatic data with a resolution of 8 m or higher. 相似文献