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61.
Andrew Harris Salvatore Alparone Alessandro Bonforte Jonathan Dehn Salvatore Gambino Luigi Lodato Letizia Spampinato 《Bulletin of Volcanology》2012,74(6):1293-1311
Between 1994 and 2010, we completed 16 thermal surveys of Vulcano’s Fossa fumarole field (Aeolian Islands, Italy). In each survey, between 400 and 1,200 vent temperatures were collected using a thermal infrared thermometer from distances of ~1?m. The results show a general decrease in average vent temperature during 1994–2003, with the average for the entire field falling from ~220°C in 1994 to ~150°C by 2003. However, between 2004 and 2010, we witnessed heating, with the average increasing to ~190°C by 2010. Alongside these annual-scale field-wide trends, we record a spatial re-organisation of the fumarole field, characterised by shut down of vent zones towards the crater floor, matched by rejuvenation of zones located towards the crater rim. Heating may be expected to be associated with deflation because increased amounts of vaporisation will remove volume from the hydrothermal system Gambino and Guglielmino (J Geophys Res 113:B07402, 2008). However, over the 2004–2010 heating period, no ground deformation was observed. Instead, the number of seismic events increased from a typical rate of 37 events per month during 1994–2000 to 195 events per month during 2004–2010. As part of this increase, we noticed a much greater number of high-frequency events associated with rock fracturing. We thus suggest that the heating event of 2004–2010 was the result of changed permeability conditions, rather than change in the heat supply from the deeper magmatic source. Within this scenario, cooling causes shut down of lower sectors and re-establishment of pathways located towards the crater rim, causing fracturing, increased seismicity and heat flow in these regions. This is consistent with the zone of rejuvenation (which lies towards and at the rim) being the most favourable location for fracturing given the stress field of the Fossa cone Sch?pa et al. (J Volcanol Geotherm Res 203:133–145, 2011); it is also the most established zone, having been active at least since the early twentieth century. Our data show the value of deploying multi-disciplinary geophysical campaigns at degassing (fumarolic) hydrothermal systems. This allows more complete and constrained understanding of the true heat loss dynamics of the system. In the case study presented here, it allows us to distinguish true heating from apparent heating phases. While the former are triggered from the bottom-up, i.e. they are driven by increases in heat supply from the magmatic source, the latter are triggered from the top-down, i.e. by changing permeability conditions in the uppermost portion of the system to allow more efficient heat flow over zones predisposed to fracturing. 相似文献
62.
63.
Estimation and spatial interpolation of rainfall intensity distribution from the effective rate of precipitation 总被引:1,自引:0,他引:1
Ming Li Quanxi Shao Luigi Renzullo 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(1):117-130
Great emphasis is being placed on the use of rainfall intensity data at short time intervals to accurately model the dynamics
of modern cropping systems, runoff, erosion and pollutant transport. However, rainfall data are often readily available at
more aggregated level of time scale and measurements of rainfall intensity at higher resolution are available only at limited
stations. A distribution approach is a good compromise between fine-scale (e.g. sub-daily) models and coarse-scale (e.g. daily)
rainfall data, because the use of rainfall intensity distribution could substantially improve hydrological models. In the
distribution approach, the cumulative distribution function of rainfall intensity is employed to represent the effect of the
within-day temporal variability of rainfall and a disaggregation model (i.e. a model disaggregates time series into sets of
higher solution) is used to estimate distribution parameters from the daily average effective precipitation. Scaling problems
in hydrologic applications often occur at both space and time dimensions and temporal scaling effects on hydrologic responses
may exhibit great spatial variability. Transferring disaggregation model parameter values from one station to an arbitrary
position is prone to error, thus a satisfactory alternative is to employ spatial interpolation between stations. This study
investigates the spatial interpolation of the probability-based disaggregation model. Rainfall intensity observations are
represented as a two-parameter lognormal distribution and methods are developed to estimate distribution parameters from either
high-resolution rainfall data or coarse-scale precipitation information such as effective intensity rates. Model parameters
are spatially interpolated by kriging to obtain the rainfall intensity distribution when only daily totals are available.
The method was applied to 56 pluviometer stations in Western Australia. Two goodness-of-fit statistics were used to evaluate
the skill—daily and quantile coefficient of efficiency between simulations and observations. Simulations based on cross-validation
show that kriging performed better than other two spatial interpolation approaches (B-splines and thin-plate splines). 相似文献
64.
The paper presents results obtained by analyzing high-resolution ionospheric vertical total electron content (vTEC) data set evaluated from a chain of European ground-based Global Positioning System (GPS) stations and its equivalent slab thickness, as well as the F2-layer critical frequency foF2 and propagation factor M(3000)F2 from nearby ionosonde stations over the period 2006–2007. The study covers data within an area between 36°N and 68°N geographic latitude, and 7°W and 21°E geographic longitude during these last two years of minimum solar activity in the 23rd solar cycle. It reveals 15 extraordinary events, all of which exhibited some form of large short-lived vTEC and foF2 enhancements of the duration of small-magnitude solar-terrestrial events. The results clearly show a well-defined vTEC and foF2 storm-like disturbance patterns developed under these conditions. They prove that there are still some open questions related to the large electron density variations during weak disturbances that require additional study for both their relevance to different Global Navigation Satellite Systems (GNSS) applications and their role in the formation and evolution of the daytime ionosphere at middle latitudes. 相似文献
65.
Maria Giovanna Durante Luigi Di Sarno George Mylonakis Colin A. Taylor Armando Lucio Simonelli 《地震工程与结构动力学》2016,45(7):1041-1061
An effective way to study the complex seismic soil‐structure interaction phenomena is to investigate the response of physical scaled models in 1‐g or n‐g laboratory devices. The outcomes of an extensive experimental campaign carried out on scaled models by means of the shaking table of the Bristol Laboratory for Advanced Dynamics Engineering, University of Bristol, UK, are discussed in the present paper. The experimental model comprises an oscillator connected to a single or a group of piles embedded in a bi‐layer deposit. Different pile head conditions, that is free head and fixed head, several dynamic properties of the structure, including different masses at the top of the single degree of freedom system, excited by various input motions, e.g. white noise, sinedwells and natural earthquake strong motions recorded in Italy, have been tested. In the present work, the modal dynamic response of the soil–pile–structure system is assessed in terms of period elongation and system damping ratio. Furthermore, the effects of oscillator mass and pile head conditions on soil–pile response have been highlighted, when the harmonic input motions are considered. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
66.
Luca Salvati Sofia Bajocco Tomaso Ceccarelli Luigi Perini 《The Professional geographer》2013,65(4):647-663
This article analyzes the territorial disparities in the level of land vulnerability (TDLV) to soil degradation caused by five processes (soil erosion, salinization, sealing, contamination, and compaction) as well as by climate variations in Italy in 1990 and 2000. The analysis reveals, for each soil degradation process, a typical spatial distribution across Italy. Three processes (soil salinization, compaction, and sealing) contribute significantly to the increase in land vulnerability, which is mainly concentrated in risky areas. The observed disparities highlight a growing environmental divide between northern Italy (an economically developed region, not at risk of desertification) and southern Italy and the two main islands (dry, disadvantaged regions at risk of desertification). The knowledge of such a territorial divide and of the underlying soil degradation processes is regarded as important for environmental policies at the country and regional scales aimed at sustaining the economic and socioenvironmental cohesion between areas that are either vulnerable or nonvulnerable to soil degradation. The proposed approach should be seen as part of a decision-making tool informing policies and supporting the design of management solutions, hopefully reversing disparities in land vulnerability to soil degradation. 相似文献
67.
The predictability of meteo-oceanographic events 总被引:1,自引:1,他引:0
We have explored the predictability of storms in a small enclosed basin with a complicated surrounding orography. We have
considered two exceptional storms in the far past and three mild events happened in recent years. A posteriori forecasts have
been done up to 6 days before the events. The results have been compared versus measured data and the related analysis. Good
predictability (10–15% error in surface wind speed and wave height) have been found up to day 4, mildly larger (<30%) up to
day 6 before the event. In no case was a storm missed. This suggests that the effective predictability in more open basins
may extend to even larger ranges. 相似文献
68.
Kmar Ben İsmail-Lattrache Kamel Boukhalfa Pratul Kumar Saraswati Mohamed Soussi Luigi Jovane 《Geodinamica Acta》2013,26(1-2):94-121
The orthophragminids in lower Bartonian Reineche Limestone member, a fossiliferous shallow-marine unit exposed in Cap Bon peninsula in Tunisia, are represented by 17 species assigned to Discocyclinidae Galloway 1928 and Orbitoclypeidae Brönnimann 1946. These taxa, associated with nummulitids and alveolinids, belong to the lineages of Discocyclina Gümbel 1870, Nemkovella, 1987, Orbitoclypeus Silvestri 1907, and Asterocyclina Gümbel 1870, described for the first time from north Africa lying at the southern margin of Tethyan ocean during Paleogene. We identified Nemkovella evae, previously not recorded in upper Lutetian/lower Bartonian and younger Eocene deposits of northern Tethyan platforms, and erected a new subspecies, N. evae reinechensis n. ssp. A comparison of Reineche orthophraminids, assigned to orthophragmines zone (OZ) 12 and shallow benthic zone (SBZ 17), to the well-described coeval assemblages at northern Tethyan platforms in Italy, Hungary, Turkey, and to those in Kutch Basin in the Indian subcontinent suggests that some species are confined to certain paleogeographic domains. Orbitoclypeus haynesi, the only orbitoclypeid and the most abundant orthophragminid in lower Bartonian deposits in Kutch, appears to be the most common orbitoclypeid in Reineche Limestone. In Europe, this species is not known and is replaced by Orbitoclypeus varians, the most common orbitoclypeid in middle Eocene of central Europe. Both species occur in varying proportions in marine successions in Turkey. Asterocyclina sireli, identified so far only in Turkey, occurs in Reineche Limestone and in lower Bartonian deposits in Kutch. This species is recorded for the first time in the Indian subcontinent. Relying on present study, as well as our recent studies in Kutch Basin, we conclude that the generic and specific diversity of orthophragminids decreases eastward from the peri-Mediterranean region to Indian subcontinent and to the western Pacific. 相似文献
69.
Roberto Sulpizio Rosanna Bonasia Pierfrancesco Dellino Mauro A. Di Vito Luigi La Volpe Daniela Mele Giovanni Zanchetta Laura Sadori 《Journal of Volcanology and Geothermal Research》2008
Ash samples from tephra layers correlated with the Pomici di Avellino (Avellino Pumice) eruption of Somma-Vesuvius were collected in distal archives and their composition and particle morphology investigated in order to infer their behaviour of transportation and deposition. Differences in composition and particle morphologies were recognised for ash particles belonging to the magmatic Plinian and final phreatomagmatic phases of the eruption. The ash particles were dispersed in opposite directions during the two different phases of the eruption, and these directions are also different from that of coarse-grained fallout deposits. In particular, ash generated during magmatic phase and injected in the atmosphere to form a sustained column shows a prevailing SE dispersion, while ash particles generated during the final phreatomagmatic phase and carried by pyroclastic density currents show a general NW dispersion. These opposite dispersions indicate an ash dispersal influenced by both high and low atmosphere dynamics. In particular, the magmatic ash dispersal was first driven by stratospheric wind towards NE and then the falling particles encountered a variable wind field during their settling, which produced the observed preferential SE dispersal. The wind field encountered by the rising ash clouds that accompanied the pyroclastic density currents of the final phreatomagmatic phase was different with respect to that encountered by the magmatic ash, and produced a NW dispersal. These data demonstrate how ash transportation and deposition are greatly influenced by both high and low atmosphere dynamics. In particular, fine-grained particles transported in ash clouds of small-scale pyroclastic density currents may be dispersed over distances and cover areas comparable with those injected into the stratosphere by Plinian, sustained columns. This is a point not completely addressed by present day mitigation plans in case of renewal of activity at Somma-Vesuvius, and can yield important information also for other volcanoes potentially characterised by explosive activity. 相似文献
70.
Ciro Del Negro Luigi Fortuna Alexis Herault Annamaria Vicari 《Bulletin of Volcanology》2008,70(7):805-812
Since the mechanical properties of lava change over time, lava flows represent a challenge for physically based modeling.
This change is ruled by a temperature field which needs to be modeled. MAGFLOW Cellular Automata (CA) model was developed
for physically based simulations of lava flows in near real-time. We introduced an algorithm based on the Monte Carlo approach
to solve the anisotropic problem. As transition rule of CA, a steady-state solution of Navier-Stokes equations was adopted
in the case of isothermal laminar pressure-driven Bingham fluid. For the cooling mechanism, we consider only the radiative
heat loss from the surface of the flow and the change of the temperature due to mixture of lavas between cells with different
temperatures. The model was applied to reproduce a real lava flow that occurred during the 2004–2005 Etna eruption. The simulations
were computed using three different empirical relationships between viscosity and temperature. 相似文献