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111.
112.
M.A. Di Vito R. Sulpizio G. Zanchetta M. D'Orazio 《Journal of Volcanology and Geothermal Research》2008
The lithological and compositional characteristics of eighteen different pyroclastic deposits of Campanian origin, dated between 125 cal ky BP and 22 cal ky BP, were described. The pyroclastic deposits were correlated among different outcrops mainly located on the Apennine slopes that border the southern Campanian Plain. They were grouped in two main stratigraphic and chronologic intervals of regional significance: a) between Pomici di Base (22.03 cal ky BP; Somma–Vesuvius) and Campanian Ignimbrite (39 cal ky BP; Campi Flegrei) eruptions; and b) older than Campanian Ignimbrite eruption. Three new 14C AMS datings support the proposed correlations. Six eruptions were attributed to the Pomici di Base-Campanian Ignimbrite stratigraphic interval, while twelve eruptions are older than Campanian Ignimbrite. Of the studied deposits two originated from Ischia island, five are related to Campi Flegrei, and three to Somma–Vesuvius. Two eruptions have an uncertain correlation with Somma–Vesuvius or Campi Flegrei, while six eruptions remain of uncertain source. Minimum volumes of five eruptions were assessed, ranging between 0.5 km3 and 4 km3. Two of the studied deposits were correlated with Y-3 and X-5 tephra layers, which are widely dispersed in the central Mediterranean area. The new stratigraphic and chronologic data provide an upgraded chrono-stratigraphy for the explosive activity of Neapolitan volcanoes in the period between 125 and 22 cal ky BP. 相似文献
113.
Francesco G. Carollo Costanza Di Stefano Vito Ferro Vincenzo Pampalone Francesco Sanzone 《地球表面变化过程与地形》2016,41(7):867-874
In order to measure soil loss in equipped plots the estimate of the weight of solid material intercepted at their lower end is required. At the experimental area of Sparacia, Sicily, the runoff produced by an erosive event is collected within storage tanks with a capacity of about 1 m3. In this paper, the use of a new sampler is proposed to measure easily the weight of solid material eroded from an experimental plot and collected into a storage tank. The sampler is a cylinder having a closing valve at the bottom. Two different series of runs were carried out both to test the reliability of the sampler and to establish a sampling procedure, respectively. An analysis of various sampling configurations usable in the field differentiated by the number and location of sampling verticals in the tank cross‐section was finally carried out. The results of the present investigation are that the concentration measurement by the sampler was more accurate than that obtained by other methods involving a collection tank, agitation and sampling of the suspension. This sampler is cheap and usable in combination with a quick field sampling procedure which is particularly advisable when the number of plots equipped at an experimental area is large. The sampler was tested using a clay soil contained within cylinders and a cubic tank, but it appeared also to be usable with coarser sediment than clay and in combination with tanks having a different shape. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
114.
R. Sulpizio R. Cioni M. A. Di Vito D. Mele R. Bonasia P. Dellino 《Bulletin of Volcanology》2010,72(5):539-558
The stratigraphic succession of the Pomici di Avellino Plinian eruption from Somma-Vesuvius has been studied through field
and laboratory data in order to reconstruct the eruption dynamics. This eruption is particularly important in the Somma-Vesuvius
eruptive history because (1) its vent was offset with respect to the present day Vesuvius cone; (2) it was characterised by
a distinct opening phase; (3) breccia-like very proximal fall deposits are preserved close to the vent and (4) the pyroclastic
density currents generated during the final phreatomagmatic phase are among the most widespread and voluminous in the entire
history of the volcano. The stratigraphic succession is, here, divided into deposits of three main eruptive phases (opening,
magmatic Plinian and phreatomagmatic), which contain five eruption units. Short-lived sustained columns occurred twice during
the opening phase (Ht of 13 and 21.5 km, respectively) and dispersed thin fall deposits and small pyroclastic density currents onto the volcano
slopes. The magmatic Plinian phase produced the main volume of erupted deposits, emplacing white and grey fall deposits which
were dispersed to the northeast. Peak column heights reached 23 and 31 km during the withdrawal of the white and the grey
magmas, respectively. Only one small pyroclastic density current was emplaced during the main Plinian phase. In contrast,
the final phreatomagmatic phase was characterised by extensive generation of pyroclastic density currents, with fallout deposits
very subordinate and limited to the volcano slopes. Assessed bulk erupted volumes are 21 × 106 m3 for the opening phase, 1.3–1.5 km3 for the main Plinian phase and about 1 km3 for the final phreatomagmatic phase, yielding a total volume of about 2.5 km3. Pumice fragments are porphyritic with sanidine and clinopyroxene as the main mineral phases but also contain peculiar mineral
phases like scapolite, nepheline and garnet. Bulk composition varies from phonolite (white magma) to tephri-phonolite (grey
magma). 相似文献
115.
We suggest that the solar corona is stationarily heated by Joule dissipation of magnetohydrodynamic (MHD) turbulence. This turbulence is continuously being fed by subphotospheric convective motions at very low wavenumbers where the plasma can be considered ideal. The cascade process due to the nonlinear interaction of the turbulent modes, effectively transfers energy to even shorter wavenumbers until Joule effect becomes dominant and converts the cascading magnetic energy into heat.Assuming that a stationary spectrum is established, we show that MHD turbulence naturally provides a way of enhancing the Joule dissipation of macroscopic magnetic stresses and a heating rate can be derived. 相似文献
116.
Mauro Di Vito Lucio Lirer Giuseppe Mastrolorenzo Giuseppe Rolandi 《Bulletin of Volcanology》1987,49(4):608-615
On 29 September 1538 a week-long eruption began in Campi Flegrei forming a new volcano, Monte Nuovo. From contemporary accounts of the eruption, it has been possible to reconstruct the main phases of activity. These phases may be correlated with different depositional units identified in the field. The eruption opened with a hydromagmatic phase, during which a large amount of external water (meteoric or sea water) was able to interact with the magma. The exhaustion of the water supply and decrease in volatile content initiated a change in the dynamic conditions of eruption, which became more purely magmatic in character and less explosive. 相似文献
117.
In this paper sediment yield data, measured from 1978 to 1994 in two small Calabrian basins (W2 and W3) reafforested with eucalyptus trees (Eucalyptus occidentalis Engl.), and the Modified Universal Soil Loss Equation (MUSLE) applied in a distributed form are used to evaluate the anti-erosive effects of eucalyptus cover. At first step the sediment yield measurements observed in W2 basin are used to estimate a single cover management factor representative of the eucalyptus coppice and equal to the median value (0·164) of the cover management factor values calculated for each runoff event. Then, the reliability of the selected representative cover management factor is verified on W3 by comparing the cumulative distribution function (CDF) of the measured sediment yield with the CDF of the calculated one. Finally, the temporal analysis of the crop and management factor is developed searching, at monthly and annual scale, the correlation between crop anti-erosive effectiveness and rainfall erosivity index. © 1998 John Wiley & Sons, Ltd. 相似文献
118.
In this paper, a new flow resistance equation for rill flow was deduced applying dimensional analysis and self‐similarity theory. At first, the incomplete self‐similarity hypothesis was used for establishing the flow velocity distribution whose integration gives the theoretical expression of the Darcy–Weisbach friction factor. Then the deduced theoretical resistance equation was tested by some measurements of flow velocity, water depth, cross section area, wetted perimeter, and bed slope carried out in 106 reaches of some rills shaped on an experimental plot. A relationship between the velocity profile, the channel slope, and the flow Froude number was also established. The analysis showed that the Darcy–Weisbach friction factor can be accurately estimated by the proposed theoretical approach based on a power–velocity profile. 相似文献