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311.
Massimo Chiaradia Othmar Müntener Bernardo Beate Denis Fontignie 《Contributions to Mineralogy and Petrology》2009,158(5):563-588
In the Northern Andes of Ecuador, a broad Quaternary volcanic arc with significant across-arc geochemical changes sits upon
continental crust consisting of accreted oceanic and continental terranes. Quaternary volcanic centers occur, from west to
east, along the Western Cordillera (frontal arc), in the Inter-Andean Depression and along the Eastern Cordillera (main arc),
and in the Sub-Andean Zone (back-arc). The adakite-like signatures of the frontal and main arc volcanoes have been interpreted
either as the result of slab melting plus subsequent slab melt–mantle interactions or of lower crustal melting, fractional
crystallization, and assimilation processes. In this paper, we present petrographic, geochemical, and isotopic (Sr, Nd, Pb)
data on dominantly andesitic to dacitic volcanic rocks as well as crustal xenolith and cumulate samples from five volcanic
centers (Pululagua, Pichincha, Ilalo, Chacana, Sumaco) forming a NW–SE transect at about 0° latitude and encompassing the
frontal (Pululagua, Pichincha), main (Ilalo, Chacana), and back-arc (Sumaco) chains. All rocks display typical subduction-related
geochemical signatures, such as Nb and Ta negative anomalies and LILE enrichment. They show a relative depletion of fluid-mobile
elements and a general increase in incompatible elements from the front to the back-arc suggesting derivation from progressively
lower degrees of partial melting of the mantle wedge induced by decreasing amounts of fluids released from the slab. We observe
widespread petrographic evidence of interaction of primary melts with mafic xenoliths as well as with clinopyroxene- and/or
amphibole-bearing cumulates and of magma mixing at all frontal and main arc volcanic centers. Within each volcanic center,
rocks display correlations between evolution indices and radiogenic isotopes, although absolute variations of radiogenic isotopes
are small and their values are overall rather primitive (e.g., εNd = +1.5 to +6, 87Sr/86Sr = 0.7040–0.70435). Rare earth element patterns are characterized by variably fractionated light to heavy REE (La/YbN = 5.7–34) and by the absence of Eu negative anomalies suggesting evolution of these rocks with limited plagioclase fractionation.
We interpret the petrographic, geochemical, and isotopic data as indicating open-system evolution at all volcanic centers
characterized by fractional crystallization and magma mixing processes at different lower- to mid-crustal levels as well as
by assimilation of mafic lower crust and/or its partial melts. Thus, we propose that the adakite-like signatures of Ecuadorian
rocks (e.g., high Sr/Y and La/Yb values) are primarily the result of lower- to mid-crustal processing of mantle-derived melts,
rather than of slab melts and slab melt–mantle interactions. The isotopic signatures of the least evolved adakite-like rocks
of the active and recent volcanoes are the same as those of Tertiary ”normal” calc-alkaline magmatic rocks of Ecuador suggesting
that the source of the magma did not change through time. What changed was the depth of magmatic evolution, probably as a
consequence of increased compression induced by the stronger coupling between the subducting and overriding plates associated
with subduction of the aseismic Carnegie Ridge. 相似文献
312.
Fabrizio Murgia Riccardo Biddau Alessandro Concas Roberto Demontis Luca Fanfani Zeno Heilmann Cristian Lai Giuditta Lecca Eva Lorrai Marino Marrocu Vittorio Alessandro Marrone Laura Muscas Elisaveta Peneva Andrea Piras Massimo Pisu Gabriella Pusceddu Guido Satta Daniela Theis Andrea Vacca Paolo Valera Ana Melina Vallenilla Ferrara Ernesto Bonomi 《Earth Science Informatics》2009,2(1-2):5-21
GRIDA3 (Shared Resources Manager for Environmental Data Analysis and Applications) is a multidisciplinary project designed to deliver an integrated system to forge solutions to some environmental challenges such as the constant increase of polluted sites, the sustainability of natural resources usage and the forecast of extreme meteorological events. The GRIDA3 portal is mainly based on Web 2.0 technologies and EnginFrame framework. The portal, now at an advanced stage of development, provides end-users with intuitive Web-interfaces and tools that simplify job submission to the underneath computing resources. The framework manages the user authentication and authorization, then controls the action and job execution into the grid computing environment, collects the results and transforms them into an useful format on the client side. The GRIDA3 Portal framework will provide a problem-solving platform allowing, through appropriate access policies, the integration and the sharing of skills, resources and tools located at multiple sites across federated domains. 相似文献
313.
Antonella Boselli Mario Armenante Loredana D’Avino Massimo D’Isidoro Gianluca Pisani Nicola Spinelli Xuan Wang 《Boundary-Layer Meteorology》2009,132(1):151-165
The evolution of the planetary boundary layer and the influence of local circulation phenomena over Naples (southern Italy,
40.838° N, 14.183° E, 118 m above sea level) have been studied by systematic lidar measurements of aerosol optical properties
and vertical distributions carried out from May 2000 to August 2003, in the course of the EARLINET project. In particular,
our data show the development of aerosol layers typically located in the range between 1,000 and 2,300 m, with variable thickness.
The optical properties of the observed layers have been determined. In order to analyse the evolution of the planetary boundary
layer, detailed observations of complete diurnal cycles have also been performed. The analysis of lidar measurements of vertical
profiles of wind speed and wind direction and air mass back-trajectories allowed us to characterize the sea-breeze circulation
influence on both the planetary boundary-layer evolution and the observed aerosol vertical distribution. 相似文献
314.
Preparatory talks to the next round of negotiations seem to indicate that a comprehensive agreement to mitigate climate change will not be easily attainable, despite the intentions of the US administration and the high expectations surrounding the Copenhagen meeting. One key reason is to what extent fast growing economies, and especially China, should take actions to reduce their growth of emissions. This paper argues that a turning point for international negotiations on climate change could be achieved if China were to agree on carbon obligations in the future. Results from modelling work suggest that the optimal investment behaviour is to anticipate the implementation of a climate policy by roughly 10 years, and that thus future commitments—if credible—could lead to significantly earlier steps towards carbon mitigation. If fast growing economies, and foremost China, believe in the long term objective of global stabilization of carbon concentrations, it might be economically rationale to sign on future targets, provided developed countries take on immediate action. Such a provision could be beneficial for both the developing and developed world. 相似文献
315.
Valentina Bruno Carmelo Ferlito Mario Mattia Carmelo Monaco Massimo Rossi Danila Scandura 《地学学报》2016,28(5):356-363
Continuous GPS (CGPS) data, collected at Mt. Etna between April 2012 and October 2013, clearly define inflation/deflation processes typically observed before/after an eruption onset. During the inflationary process from May to October 2013, a particular deformation pattern localised in the upper North Eastern sector of the volcano suggests that a magma intrusion had occurred a few km away from the axis of the summit craters, beneath the NE Rift system. This is the first time that this pattern has been recorded by CGPS data at Mt. Etna. We believe that this inflation process might have taken place periodically at Mt. Etna and might be associated with the intrusion of batches of magma that are separate from the main feeding system. We provide a model to explain this unusual behaviour and the eruptive regime of this rift zone, which is characterised by long periods of quiescence followed by often dangerous eruptions in which vents can open at low elevation and thus threaten the villages in this sector of the volcano. 相似文献
316.
Massimo Cassiani 《Boundary-Layer Meteorology》2013,146(2):207-233
A new approach is proposed to predict concentration fluctuations in the framework of one-particle Lagrangian stochastic models. The approach is innovative since it allows the computation of concentration fluctuations in dispersing plumes using a Lagrangian one-particle model with micromixing but with no need for the simulating of background particles. The extension of the model for the treatment of chemically reactive plumes is also accomplished and allows the computation of plume-related chemical reactions in a Lagrangian one-particle framework separately from the background chemical reactions, accounting for the effect of concentration fluctuations on chemical reactions in a general, albeit approximate, manner. These characteristics should make the proposed approach an ideal tool for plume-in-grid calculations in chemistry transport models. The results are compared to the wind-tunnel experiments of Fackrell and Robins (J Fluid Mech, 117:1–26, 1982) for plume dispersion in a neutral boundary layer and to the measurements of Legg et al. (Boundary-Layer Meteorol, 35:277–302, 1986) for line source dispersion in and above a model canopy. Preliminary reacting plume simulations are also shown comparing the model with the experimental results of Brown and Bilger (J Fluid Mech, 312:373–407, 1996; Atmos Environ, 32:611–628, 1998) to demonstrate the feasibility of computing chemical reactions in the proposed framework. 相似文献
317.
Antonella Bertagnini Alessio Di Roberto Massimo Pompilio 《Bulletin of Volcanology》2011,73(9):1229-1243
The persistent normal activity of Stromboli is occasionally interrupted by sudden and highly energetic explosive events called
Strombolian paroxysms. These phenomena together with landslide-generated tsunamis represent the most hazardous manifestations
of present-day volcanic activity at Stromboli. The most recent paroxysms, on 5 April 2003 and 15 March 2007, have drawn attention
to these energetic events because they significantly threatened inhabitants and tourists. Historical accounts and field evidence
indicate, however, that even larger paroxysms, in terms of volume, dispersal of products and intensity of explosive phenomena,
occurred in the recent past. During these paroxysms incipiently welded spatter deposits mantled the north and south rims of
the Sciara del Fuoco down to low elevations, extending much farther than the similar deposits from recent observed events
(5 April 2003 and 15 March 2007). In order to identify, characterize and discriminate among products of these outstanding
spatter-forming eruptions, more than 50 stratigraphic sections were measured and sampled. Stratigraphic, sedimentological
and radiometric (14C) data indicate that only two paroxysms produced spatter that reached very low elevations and inhabited areas: the first
occurred in the 16th century and the last in AD 1930. Analysis of texture and deposit components reveals that the early phases
of the two eruptions were driven by distinctly different eruptive dynamics. Both identified paroxysms are at least one order
of magnitude greater than any similar event observed by monitoring systems at Stromboli. These two large paroxysms were the
most powerful volcanic events at Stromboli in the last eighteen centuries. 相似文献
318.
Massimo Cortini Loredana Cilento Alessandro Rullo 《Journal of Volcanology and Geothermal Research》1991,48(1-2)
The ground level in the Campi Flegrei caldera has never been stationary in the last 2,000 years. Historical data, and a nearly continuous tide-gauge record 20 years long, show that uplift and sinking have taken place on a variety of different time scales. In addition, the Campi Flegrei volcanic system appears to be sensitive to weak external forces such as tidal forces. We infer from these elements that the Campi Flegrei system is far from thermodynamic equilibrium, and suggest that its dynamics may be chaotic. We analyze the short-term variations of the ground level, and find that they can be described in a low-dimensional phase space. The dynamics of the Campi Flegrei system seems to have been phase-locked with tidal forces in the period following the 1970–1972 climax, and to have undergone a transition to chaos in some moment that preceded the presently continuing sinking phase. 相似文献
319.
AN ION PROBE CONTRIBUTION TO RARE EARTH ELEMENT INVESTIGATION OF GABBRO GOG-1 USING SECONDARY ION MASS SPECTROMETRY 总被引:1,自引:0,他引:1
Luisa OTTOLINI Piero BOTTAZZI Riccardo VANNUCCI Massimo ODDONE 《Geostandards and Geoanalytical Research》1992,16(1):13-19
An updated REE measurement of Gabbro GOG-1 was carried out by means of secondary ion mass spectrometry (SIMS). The availability of high amount of rock powder allowed the sample to be well ground and homogenized before analysis. Fused glass pellets were employed for SIMS investigations. REE data were compared with new ICP-AES and NAA analyses. REE results from all employed analytical techniques show good agreement and are consistent with in-situ SIMS measurements of REE in major mineral phases forming GOG-1. Extensive homogeneity tests seem to confirm the possibility to using this rock as a reference material for earth sciences. 相似文献
320.
Riccardo Tribuzio Massimo Tiepolo Stefania Fiameni 《Contributions to Mineralogy and Petrology》2008,155(5):619-633
The layered sequence from Niagara Icefalls (northern Victoria Land, Antarctica) is related to the Cambrian-Early Ordovician
Ross Orogeny. The sequence consists of dunites, harzburgites, orthopyroxenites, melagabbronorites and gabbronorites of cumulus
origin. The Mg# of olivine, spinel, orthopyroxene and clinopyroxene from these rocks yields positive correlations, thus indicating
formation from melts that mainly evolved through fractional crystallisation. The following fractionation sequence was identified:
olivine (up to 94 mol% forsterite) + Cr-rich spinel → olivine + orthopyroxene ± spinel → orthopyroxene → orthopyroxene + anorthite-rich
plagioclase ± clinopyroxene. Clinopyroxenes retain the peculiar trace element signature of boninite melts, such as extremely
low concentrations of HREE and HFSE, and LILE enrichment over REE and HFSE. U–Pb isotope data on zircons separated from a
gabbronorite have allowed us to constrain the age of emplacement of the Niagara Icefalls sequence at ∼514 Ma. The occurrence
of inherited zircons dated at ∼538 Ma indicates that the boninitic melts experienced, at least locally, crustal contamination.
The Niagara Icefalls sequence can be related to a regional scale magmatic event that affected the eastern margin of the Gondwana
supercontinent in the Middle Cambrian. We propose that the formation of the sequence was associated with the development of
an embryonic back-arc basin in an active continental margin.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献