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261.
In this paper we have described the proceduresused, input data applied and results achieved in ourefforts to develop seismic hazard maps of Honduras.The probabilistic methodology of Cornell is employed.Numerical calculations were carried out by making useof the computer code SEISRISK III. To examine theimpact of uncertainties in seismic and structuralcharacteristics, the logic tree formalism has beenused. We compiled a de-clustered earthquake cataloguefor the region comprising 1919 earthquakes occurringduring the period from 1963 to 1997. Unified momentmagnitudes were introduced. Definition of aseismotectonic model of the whole region under review,based on geologic, tectonic and seismic information,led to the definition of seven seismogenetic zones forwhich seismic characteristics were determined. Fourdifferent attenuation models were considered. Resultsare expressed in a series of maps of expected PGA for60% and 90% probabilities of nonexceedence in a50-year interval which corresponds to return periodsof 100 and 475 years, respectively. The highest PGAvalues of about 0.4g (90% probability ofnon-exceedence) are expected along the borders withGuatemala and El Salvador. 相似文献
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Virginia Ruiz-Villanueva Bruno Mazzorana Ernest Bladé Livia Bürkli Pablo Iribarren-Anacona Luca Mao Futoshi Nakamura Diego Ravazzolo Dieter Rickenmann Marcos Sanz-Ramos Markus Stoffel Ellen Wohl 《地球表面变化过程与地形》2019,44(9):1694-1709
Inorganic sediment is not the only solid-fraction component of river flows; flows may also carry significant amounts of large organic material (i.e. large wood), but the characteristics of these wood-laden flows (WLFs) are not well understood yet. With the aim to shed light on these relatively unexamined phenomena, we collected home videos showing natural flows with wood as the main solid component. Analyses of these videos as well as the watersheds and streams where the videos were recorded allowed us to define for the first time WLFs, describe the main characteristics of these flows and broaden the definition of wood transport regimes (adding a new regime called here hypercongested wood transport). According to our results, WLFs may occur repeatedly, in a large range of catchment sizes, generally in steep, highly confined single thread channels in mountain areas. WLFs are typically highly unsteady and the log motion is non-uniform, as described for other inorganic sediment-laden flows (e.g. debris flows). The conceptual integration of wood into our understanding of flow phenomena is illustrated by a novel classification defining the transition from clear water to hypercongested, wood and sediment-laden flows, according to the composition of the mixture (sediment, wood, and water). We define the relevant metrics for the quantification and modelling of WLFs, including an exhaustive discussion of different modelling approaches (i.e. Voellmy, Bingham and Manning) and provide a first attempt to simulate WLFs. We draw attention to WLF phenomena to encourage further field, theoretical, and experimental investigations that may contribute to a better understanding of flows in river basins, leading to more accurate predictions, and better hazard mitigation and management strategies. © 2019 John Wiley & Sons, Ltd. 相似文献
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Zonda wind is a typical downslope windstorm over the eastern slopes of the Central Andes in Argentina,which produces extremely warm and dry conditions and creates substantial socioeconomic impacts.The aim of this work is to obtain an index for predicting the probability of Zonda wind occurrence.The Principal Component Analysis(PCA)is applied to the vertical sounding data on both sides of the Andes.Through the use of a binary logistic regression,the PCA is applied to discriminate those soundings associated with Zonda wind events from those that are not,and a probabilistic forecasting tool for Zonda occurrence is obtained.This index is able to discriminate between Zonda and non-Zonda events with an effectiveness close to 91%.The best model consists of four variables from each side of the Andes.From an eventbased statistical perspective,the probability of detection of the mixed model is above 97%with a probability of false detection lower than 7%and a missing ratio below 1%.From an alarm-based perspective,models exhibit false alarm rate below 7%,a missing alarm ratio lower than 1.5%and higher than 93%for the correct alarm ratio.The zonal component of the wind on both sides of the Andes and the windward temperature are the key variables in class discrimination.The vertical structure of Zonda wind includes two wind maximums and an unstable lapse rate at midlevels on the lee side and a wind maximum at 700 h Pa accompanied by a relatively stable layer near the mountain top. 相似文献
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Fault-controlled dolostone geometries in a transgressive–regressive sequence stratigraphic framework
Shuqing Yao Enrique Gomez-Rivas Juan Diego Martín-Martín David Gómez-Gras Anna Travé Albert Griera John A. Howell 《Sedimentology》2020,67(6):3290-3316
This study investigates the geometries of fault-controlled dolostone geobodies and their structural and sequence stratigraphic controls, which provide new insights for the prediction and production of fault-controlled dolomitized hydrocarbon reservoirs. A very thick succession (>1600 m) of Aptian–Albian shallow-marine carbonates of the Benassal Formation that crop out in the Benicàssim area (Maestrat Basin, eastern Spain) is partly replaced by dolomite, resulting in dolostone geometries ranging from massive patches to stratabound bodies. Detailed mapping, systematic logging and correlation were carried out to characterize the structural, sedimentary and sequence stratigraphic framework of the area and to constrain the principal controls on the full-range of dolostone geometries. The results show that carbonate sediments accumulated in a half graben stacked in three transgressive–regressive sequences. Large-scale massive dolostone patches (with up to kilometre extension) formed near large-scale faults indicating that they acted as entry points for warm dolomitizing fluids into the basin. These dolostone patches laterally pass to large stratabound bodies that extend for long distances (at least 7 km) away from feeding faults, forming a continuum. The presence of a regional unconformity and a clastic fine-grain low-permeability unit (Escucha Formation) on top of the Benassal Formation likely constrained the dolomitization fluids to an up to 580 m thick interval below the base of the Escucha Formation. Thus, only limestones within this interval, corresponding to the two uppermost transgressive–regressive sequences, were dolomitized. There is a clear relationship between the stratigraphic framework and the preferred replaced beds. Dolomitization preferentially affected sediments deposited in inner to middle ramp settings with predominant wackestone to packstone textures. Such facies are laterally most abundant in the east of the study area (i.e. basinward) and vertically in layers around the maximum flooding zone of the top sequence, which is preferentially affected by dolomitization. 相似文献
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A streamflow drought climatology was developed over the Central Andes of Argentina, a semi-arid region highly vulnerable to climatic variations, based on the analysis of daily historical streamflow records. A threshold level approach was applied on a daily basis for three different severity levels in order to depict the main characteristics of droughts – number of drought events, mean duration and mean severity – over the period 1957–2014. Based on three annual indices that summarize the frequency of drought events, their duration and severity, we identified the main regional dry periods and the main modes of variability through an empirical decomposition. These modes are linked to La Niña conditions on inter-annual time scales and the Pacific Decadal Oscillation for the decadal variations, showing the influence of the tropical Pacific Ocean in the development of streamflow drought conditions and its relevance for potential predictability of hydroclimatic variations over the region. 相似文献
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Ramos Claudete Gindri dos Santos de Medeiros Diego Gomez Leandro Oliveira Luis Felipe Silva Schneider Ivo André Homrich Kautzmann Rubens Muller 《Natural Resources Research》2020,29(3):1583-1600
Natural Resources Research - This study was focused on physical, petrographical, mineralogical, and chemical characterization of a volcanic-rock mining by-product (dacite rock), as well as on... 相似文献