全文获取类型
收费全文 | 96篇 |
免费 | 8篇 |
专业分类
测绘学 | 10篇 |
大气科学 | 7篇 |
地球物理 | 26篇 |
地质学 | 41篇 |
海洋学 | 7篇 |
天文学 | 6篇 |
自然地理 | 7篇 |
出版年
2021年 | 2篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 5篇 |
2014年 | 6篇 |
2013年 | 8篇 |
2012年 | 6篇 |
2011年 | 7篇 |
2010年 | 2篇 |
2009年 | 5篇 |
2008年 | 2篇 |
2007年 | 5篇 |
2006年 | 1篇 |
2005年 | 3篇 |
2004年 | 4篇 |
2003年 | 1篇 |
2002年 | 8篇 |
2001年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1986年 | 3篇 |
1980年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有104条查询结果,搜索用时 390 毫秒
61.
Maria V. Peppa Jon P. Mills Phil Moore Pauline E. Miller Jonathan E. Chambers 《地球表面变化过程与地形》2019,44(1):287-303
Landslides represent hazardous phenomena, often with significant implications. Monitoring landslides with time-series surface observations can indicate surface failure. Unmanned aerial vehicles (UAVs) employing compact digital cameras, in conjunction with structure-from-motion (SfM) and multi-view stereo (MVS) image processing approaches, have become commonplace in the geoscience research community. These methods offer relatively low-cost, flexible solutions for many geomorphological monitoring applications. However, conventionally ground control points (GCPs) are required for registration purposes, the provision of which is often expensive, difficult or even impracticable in hazardous and inaccessible terrain. In an attempt to overcome the reliance on GCPs, this paper reports research that has developed a morphology-based strategy to co-register multi-temporal UAV-derived products. It applies the attribute of curvature in combination with the scale-invariant feature transform algorithm, to generate time-invariant curvature features, which serve as pseudo-GCPs. Openness, a surface morphological digital elevation model derivative, is applied to identify relatively stable ground regions from which pseudo-GCPs are selected. A sensitivity threshold quantifies the minimum detectable change alongside unresolved biases and misalignment errors. The approach is evaluated at two study sites in the UK, first at Sandford with artificially induced surface change, and second at an active landslide at Hollin Hill, with multi-epoch SfM-MVS products derived from a consumer-grade UAV. Elevation changes and annual displacement rates at dm-level are estimated, with optimal results achieved over winter periods. The morphology-based co-registration strategy resulted in relative error ratios (i.e. mean error divided by average flying height) in the range 1:800–2500, comparable with those reported by similar studies conducted with UAVs augmented with real time kinematic (RTK)-Global Navigation Satellite Systems. Analysis demonstrates the potential of the morphology-based strategy for a semi-automatic, and practical co-registration approach to quantify surface motion. This can ultimately complement geotechnical and geophysical investigations and support the understanding of landslide behaviour, model prediction and construction of measures for mitigating risks. © 2018 John Wiley & Sons, Ltd. 相似文献
62.
Kelly D. Thomson Daniel F. Stockli Margaret L. Odlum Pauline Tolentino Cai Puigdefàbregas Julian Clark Andrea Fildani 《Basin Research》2020,32(3):485-504
This study constrains the sediment provenance for the Late Cretaceous–Eocene strata of the Ager Basin, Spain, and reconstructs the interplay between foreland basin subsidence and sediment routing within the south-central Pyrenean foreland basin during the early phases of crustal shortening using detrital zircon (DZ) U-Pb-He double dating. Here we present and interpret 837 new DZ U-Pb ages, 113 of which are new DZ (U-Th)/He double-dated zircons. U-Pb-He double dating results allow for a clear differentiation between different foreland and hinterland sources of Variscan zircons (280–350 Ma) by leveraging the contrasting thermal histories of the Ebro Massif and Pyrenean orogen, recorded by the zircon (U-Th)/He (ZHe) ages, despite their indistinguishable U-Pb age signatures. Cretaceous–Paleocene sedimentary rocks, dominated by Variscan DZ U-Pb age components with Permian–Triassic (200–300 Ma) ZHe cooling ages, were sourced from the Ebro Massif south of the Ager Basin. A provenance shift occurred at the base of the Early Eocene Baronia Formation (ca. 53 Ma) to an eastern Pyrenean source (north-east of the Ager Basin) as evidenced by an abrupt change in paleocurrents, a change in DZ U-Pb signatures to age distributions dominated by Cambro-Silurian (420–520 Ma), Cadomian (520–700 Ma), and Proterozoic–Archean (>700 Ma) age components, and the prominent emergence of Cretaceous–Paleogene (<90 Ma) ZHe cooling ages. The Eocene Corçà Formation (ca. 50 Ma), characterized by the arrival of fully reset ZHe ages with very short lag times, signals the accumulation of sediment derived from the rapidly exhuming Pyrenean thrust sheets. While ZHe ages from the Corçà Formation are fully reset, zircon fission track (ZFT) ages preserve older inherited cooling ages, bracketing the exhumation level within the thrust sheets to ca. 6–8 km in the Early Eocene. These DZ ZHe ages yield exhumation rate estimates of ca. 0.03 km/Myr during the Late Cretaceous–Paleocene for the Ebro Massif and ca. 0.2–0.4 km/Myr during the Eocene for the eastern Pyrenees. 相似文献
63.
Paul R. T. Newby Paul Aplin Simon J. Buckley Jim H. Chandler Jane E. Drummond David A. Holland Samantha J. Lavender Pauline E. Miller Jon P. Mills Henny Mills A. Stewart Walker Peter A. Woodsford 《The Photogrammetric Record》2009,24(125):66-102
The XXIst International Congress of Photogrammetry and Remote Sensing was held at the Beijing International Convention Centre, China, from 3rd to 11th July 2008. Reports are given on the Congress as a whole, including the General Assembly, some Technical Commission activities and the Congress Exhibition. Papers from the Congress are published in Volume XXXVII of the International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. 相似文献
64.
65.
Pauline Souloumiac Kristian Krabbenh?ft Yves M. Leroy Bertrand Maillot 《Computational Geosciences》2010,14(4):793-811
The objective is to capture the 3D spatial variation in the failure mode occurring in accretionary wedges and their analog
experiments in the laboratory from the sole knowledge of the material strength and the structure geometry. The proposed methodology
relies on the maximum strength theorem which is inherited from the kinematic approach of the classical limit analysis. It
selects the optimum virtual velocity field which minimizes the tectonic force. These velocity fields are constructed by interpolation
thanks to the spatial discretization conducted with ten-noded tetrahedra in 3D and six-noded triangles in 2D. The resulting,
discrete optimization problem is first presented emphasizing the dual formalism found most appropriate in the presence of
nonlinear strength criteria, such as the Drucker–Prager criterion used in all reported examples. The numerical scheme is first
applied to a perfectly triangular 2D wedge. It is known that failure occurs to the back for topographic slope smaller than
and to the front for slope larger than a critical slope, defining subcritical and supercritical slope stability conditions,
respectively. The failure mode is characterized by the activation of a ramp, its conjugate back thrust, and the partial or
complete activation of the décollement. It is shown that the critical slope is captured precisely by the proposed numerical
scheme, the ramp, and the back thrust corresponding to regions of localized virtual strain. The influence of the back-wall
friction on this critical slope is explored. It is found that the failure mechanism reduces to a thrust rooting at the base
of the back wall and the absence of back thrust, for small enough values of the friction angle. This influence is well explained
by the Mohr construction and further validated with experimental results with sand, considered as an analog material. 3D applications
of the same methodology are presented in a companion paper. 相似文献
66.
Janne Heiskanen Miina Rautiainen Lauri Korhonen Matti Mõttus Pauline Stenberg 《International Journal of Applied Earth Observation and Geoinformation》2011
Spectral invariants provide a novel approach for characterizing canopy structure in forest reflectance models and for mapping biophysical variables using satellite images. We applied a photon recollision probability (p) based forest reflectance model (PARAS) to retrieve leaf area index (LAI) from fine resolution SPOT HRVIR and Landsat ETM+ satellite data. First, PARAS was parameterized using an extensive database of LAI-2000 measurements from five conifer-dominated boreal forest sites in Finland, and mixtures of field-measured forest understory spectra. The selected vegetation indices (e.g. reduced simple ratio, RSR), neural networks and kNN method were used to retrieve effective LAI (Le) based on reflectance model simulations. For comparison, we established empirical vegetation index-LAI regression models for our study sites. The empirical RSR–Le regression performed best when applied to an independent test site in southern Finland [RMSE 0.57 (24.2%)]. However, the difference to the best reflectance model based retrievals produced by neural networks was only marginal [RMSE 0.59 (25.1%)]. According to this study, the PARAS model provides a simple and flexible modelling tool for calibrating algorithms for LAI retrieval in conifer-dominated boreal forests. The advantage of PARAS is that it directly uses field measurements to parameterize canopy structure (LAI-2000, hemispherical photographs) and optical properties of foliage and understory. 相似文献
67.
Pauline Durand-Riard Lise Salles Mary Ford Guillaume Caumon Jeanne Pellerin 《Marine and Petroleum Geology》2011,28(8):1530-1539
The analysis of basin dynamics and burial evolution requires a good understanding of sediment compaction. Classically, decompaction of sediments is performed in one dimension at a well location, using either a simple compaction/depth relationship or more complex elasto-plastic models. This paper presents a new approach combining sequential decompaction with 3D restoration to allow for a true 3D basin analysis. Decompaction is performed in 3D after each restoration step, thus taking into account possible tectonic events and lateral thickness variations. Care is taken to apply decompaction to ensure volume continuity especially around faults. This approach is particularly suitable for syn-depositional folds whose growth strata constrain tectonic evolution through time.The proposed approach is applied to the sand-rich turbiditic reservoir analogue of Annot (SE France) where two fictitious wells are used to compare the new 3D technique to a well decompaction analysis. Coupling restoration and decompaction leads to an improved assessment of the basin history: an uplift of the underlying units is identified, which was not detected using decompaction on wells only. Such differences may have a significant impact on possible hydrocarbon maturation models of the basin. Moreover, the geometry of the restored and decompacted models can better constrains the basin history, and influence our understanding of potential hydrocarbon migration pathways. 相似文献
68.
Voronoi grids conforming to 3D structural features 总被引:1,自引:0,他引:1
Romain Merland Guillaume Caumon Bruno Lévy Pauline Collon-Drouaillet 《Computational Geosciences》2014,18(3-4):373-383
Flow simulation in a reservoir can be highly impacted by upscaling errors. These errors can be reduced by using simulation grids with cells as homogeneous as possible, hence conformable to horizons and faults. In this paper, the coordinates of 3D Voronoi seeds are optimized so that Voronoi cell facets honor the structural features. These features are modeled by piecewise linear complex (PLC). The optimization minimizes a function made of two parts: (1) a barycentric function, which ensures that the cells will be of good quality by maximizing their compactness; and (2) a conformity function, which allows to minimize the volume of cells that is isolated from the Voronoi seed w.r.t., a structural feature. To determine the isolated volume, a local approximation of the structural feature inside the Voronoi cells is used to cut the cells. It improves the algorithm efficiency and robustness compared to an exact cutting procedure. This method, used jointly with an adaptive gradient solver to minimize the function, allows dealing with complex 3D geological cases. It always produces a Voronoi simulation grid with the desired number of cells. 相似文献
69.
Seasonal dynamic of a shallow freshwater lens due to irrigation in the coastal plain of Ravenna,Italy 总被引:1,自引:0,他引:1
Alexander Vandenbohede Pauline N. Mollema Nicolas Greggio Marco Antonellini 《Hydrogeology Journal》2014,22(4):893-909
Irrigation in low-lying coastal plains may enhance the formation of fresh groundwater lenses, which counteract salinization of groundwater and soil. This study presents seasonal dynamics of such a freshwater lens and discusses its influence on the salinity distribution of the unconfined aquifer in the coastal plain of Ravenna, Italy, combining field observations with numerical modeling (SEAWAT). The lens originates from an irrigation ditch used as a water reservoir for spray irrigation. The geometry of the freshwater lens shows seasonal differences because of freshwater infiltration during the irrigation season and upconing of deeper saltwater for the remainder of the year. The extent of the freshwater lens is controlled by the presence of nearby drainage ditches. Irrigation also results in a temperature anomaly in the aquifer because of the infiltration of warm water during the irrigation season. The surficial zone in the vicinity of the irrigation ditch is increased considerably in thickness. Finally, different irrigation alternatives and the influence of sea-level rise are simulated. This shows that it is necessary to integrate irrigation planning into the water management strategy of the coastal zone to have maximum benefits for freshening of the aquifer and to make optimal use of the existing infrastructure. 相似文献
70.
This study evaluates two (of the many) modelling approaches to flood forecasting for an upland catchment (the River South Tyne at Haydon Bridge, England). The first modelling approach utilizes ‘traditional’ hydrological models. It consists of a rainfall–runoff model (the probability distributed model, or PDM) for flow simulation in the upper catchment. Those flows are then routed to the lower catchment using two kinematic wave (KW) routing models. When run in forecast‐mode, the PDM and KW models utilize model updating procedures. The second modelling approach uses neural network models, which use a ‘pattern‐matching’ process to produce model forecasts.Following calibration, the models are evaluated in terms of their fit to continuous stage data and flood event magnitudes and timings within a validation period. Forecast times of 1 h, 2 h and 4 h are selected (the catchment has a response time of approximately 4 h). The ‘traditional’ models generally perform adequately at all three forecast times. The neural networks produce reasonable forecasts of small‐ to medium‐sized flood events but have difficulty in forecasting the magnitude of the larger flood events in the validation period. Possible modifications to the latter approach are discussed. © Crown copyright 2002. Reproduced with the permission of Her Majesty's stationery office. Published by John Wiley & Sons, Ltd. 相似文献