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101.
Federico Rossetti Francesca Tecce Andrea Billi Mauro Brilli 《Contributions to Mineralogy and Petrology》2007,153(6):743-760
Fluid–rock interaction was investigated in the inner aureole of the Late Miocene Monte Capanne pluton on Elba Island (Tuscany,
central Italy) by integrating structural, petrological, fluid inclusion, and stable isotope analyses. In the north-western
sector of the aureole (Procchio–Spartaia area), calc–silicates alternate with nearly pure carbonate layers at the metre scale.
Close to the pluton, the prograde metamorphic sequence includes calc–silicates that transition within a few metres to overlying
nearly pure calcite marbles. The calc–silicates are extensively metasomatised to form massive wollastonite-grossular-bearing
exoskarn. The mineralogical assemblage found in the marbles and the unshifted carbon and oxygen isotopic ratios in calcite
attest that the fluid phase was internally buffered. On the other hand, the calc–silicates constituted channels for infiltration
of disequilibrium fluids of magmatic origin. Fluid infiltration was enhanced by hydrofracturing and structurally-controlled
by existing planar anisotropies in calc–silicates (layering and lithological boundaries). At the metamorphic peak (∼600°C
and 1.5–2 kbar), the marble–calc–silicate interface acted as a barrier to fluids exsolved from the crystallising intrusions,
separating two different flow patterns in the inner aureole: a high fluid–flux region on its higher grade side (Wol-zone)
and a low fluid–flux region on the lower-grade side (Cpx zone). Results of this study: (1) documented that fluid pathways
in the aureole rocks at the top of the pluton were largely horizontal, controlled by the lithological layering and the pluton–host
rock contact; and (2) elucidated the primary control exerted by the structural and rheological properties of the host rocks
on the geometry of fluid flow during pluton emplacement. 相似文献
102.
Deep-sea exploration is rapidly improving our understanding of volatiles geochemistry in mid-ocean-ridge igneous products. It is also placing greater constraints on degassing processes of the Earth’s mantle, with the result that degassing models based on vapour-melt equilibrium are no longer able to explain the increasing number of data. In fact, such models force to postulate an upper mantle strongly heterogeneous at any scale, and cannot account for the widespread carbon supersaturation of the recovered igneous products. Here we review the global He-Ar-CO2 dataset of fluid inclusions in mid-ocean-ridge glasses using the framework of advanced modelling of multicomponent bubble growth in magmas. We display that non-equilibrium fractionations among He, Ar and CO2, driven by their different diffusivities in silicate melts, are common in most of the natural conditions of magma decompression and their signature strongly depends on pressure of degassing. Due to the comparable Ar and CO2 diffusivity, magma degassing at low pressure fractionates both the He/Ar and He/CO2 ratio by a similar extent, while the slower CO2 diffusion at high pressure causes early kinetic effects on Ar/CO2 ratio and dramatically changes the degassing path. On this ground, the very different geochemical signatures among suites of data coming from different ridge segments mainly depend on the depth of the magma chamber where the melt was stored. Besides, the variations inside a single suite highlight variable ascent speed and cooling rate of the emplaced lava. The large variations in both the He/CO2 and Ar/CO2 ratios at almost constant He/Ar, displayed in glasses coming from the Mid-Atlantic Ridge 24-30°N segment and the Rodriguez Triple Junction, are therefore interpreted as a high-pressure signature. In contrast, the simultaneous increase in both He/CO2 and He/Ar of the East Pacific Rise, Pito Seamount and South-East Indian Ridge data sets suggests the dominance of low-pressure fractionation, implying that the shallow magma chambers are at a lower depth than those of the Mid-Atlantic Ridge 24-30°N and Rodriguez Triple Junction. Our conclusions support the presence of a relationship between spreading rate and depth of high-temperature zones below ridges, and are consistent with the depth of magma chambers as suggested from seismic studies. Non-equilibrium degassing explains the volatile systematics of mid-ocean-ridge basalts by starting from a single mantle-derived magma, dispensing with the supposed need for heterogeneities in abundance ratios of volatiles in the mantle below oceanic ridges. 相似文献
103.
Roberto Danovaro Norberto Della Croce Antonio Dell'Anno Mauro Fabiano Daniela Marrale Daniela Martorano 《Progress in Oceanography》2000,46(2-4)
Downward fluxes of labile organic matter (lipids, proteins and carbohydrates) at 200 (trap A) and 1515 m depth (trap B), measured during a 12 months sediment trap experiment, are presented, together with estimates of the bacterial and cyanobacterial biomasses associated to the particles. The biochemical composition of the settling particles was determined in order to provide qualitative and quantitative information on the flux of readily available organic carbon supplying the deep-sea benthic communities of the Cretan Sea. Total mass flux and labile carbon fluxes were characterised by a clear seasonality. Higher labile organic fluxes were reported in trap B, indicating the presence of resuspended particles coming from lateral inputs. Particulate carbohydrates were the major component of the flux of labile compounds (on annual average about 66% of the total labile organic flux) followed by lipids (20%) and proteins (13%). The biopolymeric carbon flux was very low (on annual average 0.9 and 1.2 gC m−2 y−1, at trap A and B). Labile carbon accounted for most of the OC flux (on annual average 84% and 74% in trap A and B respectively). In trap A, highest carbohydrate and protein fluxes in April and September, corresponded to high faecal pellet fluxes. The qualitative composition of the organic fluxes indicated a strong protein depletion in trap B and a decrease of the bioavailability of the settling particles as a result of a higher degree of dilution with inorganic material. Quantity and quality of the food supply to the benthos displayed different temporal patterns. Bacterial biomass in the sediment traps (on average 122 and 229 μgC m−2 d−1 in trap A and B, respectively) was significantly correlated to the flux of labile organic carbon, and particularly to the protein and carbohydrate fluxes. Cyanobacterial flux (on average, 1.1 and 0.4 μgC m−2 d−1, in trap A and B, respectively) was significantly correlated with total mass and protein fluxes only in trap A. Bacterial carbon flux, equivalent to 84.2 and 156 mgC m−2 y−1, accounted for 5–6.5% of the labile carbon flux (in trap A and B respectively) and for 22–41% protein pool of the settling particles. These results suggest that in the Cretan Sea, bacteria attached to the settling particles represent a potential food source of primary importance for deep-sea benthic communities. 相似文献
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107.
Giusj Valentina Fichera Cristina Maria Belfiore Mauro Francesco La Russa Silvestro Antonio Ruffolo Donatella Barca Riccardo Frontoni Giuliana Galli Antonino Pezzino 《Geoarchaeology》2015,30(2):79-99
Roman mortars were collected from the Villa dei Quintili in Rome, an archaeological site consisting of numerous edifices from nine construction phases dating from the 2nd century A.D. to modern times. A multianalytical approach was used on 34 mortar samples to infer the evolution of production techniques over time and to identify the source area of calcareous raw materials used in the preparation of the lime. Optical microscopy, scanning electron microscopy coupled with an energy‐dispersive system, and laser ablation inductively coupled plasma mass spectrometry were used to study the samples. The major and trace element data were compared with the compositions of two types of limestone samples (Calcare Massiccio and Calcare Maiolica) collected from the Cornicolani Mountains. The results suggest that the technological practices and the calcareous raw materials used for lime production remained unchanged over the time period considered (2nd century A.D. to 3rd century A.D.). The compositions of lime‐related particles in the mortars match those of Calcare Maiolica, which suggests its use as raw material for lime production. On the whole, the results are in agreement with data from existing literature regarding both the use by Roman builders of specific raw materials for the mortars’ production and the relative supply area. 相似文献
108.
The Averno 2 fissure eruption: a recent small-size explosive event at the Campi Flegrei Caldera (Italy) 总被引:1,自引:0,他引:1
Mauro Antonio Di Vito Ilenia Arienzo Giuseppe Braia Lucia Civetta Massimo D’Antonio Valeria Di Renzo Giovanni Orsi 《Bulletin of Volcanology》2011,73(3):295-320
The Averno 2 eruption (3,700 ± 50 a B.P.) was an explosive low-magnitude event characterized by magmatic and phreatomagmatic
explosions, generating mainly fall and surge beds, respectively. It occurred in the Western sector of the Campi Flegrei caldera
(Campanian Region, South Italy) at the intersection of two active fault systems, oriented NE and NW. The morphologically complex
crater area, largely filled by the Averno lake, resulted from vent activation and migration along the NE-trending fault system.
The eruption generated a complex sequence of pyroclastic deposits, including pumice fall deposits in the lower portion, and
prevailing surge beds in the intermediate-upper portion. The pyroclastic sequence has been studied through stratigraphical,
morphostructural and petrological investigations, and subdivided into three members named A through C. Member A was emplaced
during the first phase of the eruption mainly by magmatic explosions which generated columns reaching a maximum height of
10 km. During this phase the eruption reached its climax with a mass discharge rate of 3.2 106 kg/s. Intense fracturing and fault activation favored entry of a significant amount of water into the system, which produced
explosions driven by variably efficient water-magma interaction. These explosions generated wet to dry surge deposits that
emplaced Member B and C, respectively. Isopachs and isopleths maps, as well as areal distribution of ballistic fragments and
facies variation of surge deposits allow definition of four vents that opened along a NE oriented, 2 km long fissure. The
total volume of magma extruded during the eruption has been estimated at about 0.07 km3 (DRE). The erupted products range in composition from initial, weakly peralkaline alkali-trachyte, to last-emplaced alkali-trachyte.
Isotopic data and modeling suggest that mixing occurred during the Averno 2 eruption between a more evolved, less radiogenic
stored magma, and a less evolved, more radiogenic magma that entered the shallow reservoir to trigger the eruption. The early
phases of the eruption, during which the vent migrated from SW to the center of the present lake, were fed by the more evolved,
uppermost magma, while the following phases extruded the less evolved, lowermost magma. Integration of the geological and
petrological results suggests that the Averno 2 complex eruption was fed from a dyke-shaped shallow reservoir intruded into
the NE-SW fault system bordering to the west the La Starza resurgent block, within the caldera floor. 相似文献
109.
Overview of the Italian strong motion database ITACA 1.0 总被引:3,自引:2,他引:1
Francesca Pacor Roberto Paolucci Lucia Luzi Fabio Sabetta Andrea Spinelli Antonella Gorini Mario Nicoletti Sandro Marcucci Luisa Filippi Mauro Dolce 《Bulletin of Earthquake Engineering》2011,9(6):1723-1739
The Italian Strong Motion Database, ITACA, was developed within projects S6 and S4, funded in the framework of the agreements
between the Italian Department of Civil Protection (Dipartimento della Protezione Civile, DPC) and the Istituto Nazionale
di Geofisica e Vulcanologia (INGV), starting from 2005. The alpha version of the database was released in 2007 and subsequently
upgraded to version 1.0 after: (i) including the most recent strong motion data (from 2005 to 2007) recorded in Italy, in
addition to the 2008 Parma earthquake, M 5.4, and the M ≥ 4.0, 2009 Abruzzo seismic events; (ii) processing the raw strong
motion data using an updated procedure; (iii) increasing the number of stations with a measured shear wave velocity profile;
(iv) improving the utilities to retrieve time series and ground motion parameters; (v) implementing a tool for selecting time
series in agreement with design-response spectra; (vi) compiling detailed station reports containing miscellaneous information
such as photo, maps and site parameters; (vii) developing procedures for the automatic generation of station reports and for
the updating of the header files. After such improvements, ITACA 1.0 was published at the web site , in 2010. It presently contains 3,955 three-component waveforms, comprising the most complete catalogue of the Italian accelerometric
records in the period 1972–2007 (3,562 records) and the strongest events in the period 2008–2009. Records were mainly acquired
by DPC through its Accelerometric National Network (RAN) and, in few cases, by local networks and temporary stations or networks.
This paper introduces the published version of the Italian Strong Motion database (ITACA version 1.0) together with main improvements
and new functionalities. 相似文献
110.
Barbara Borzi Fabio Dell��Acqua Marta Faravelli Paolo Gamba Gianni Lisini Mauro Onida Diego Polli 《Bulletin of Earthquake Engineering》2011,9(2):675-690
The aim of this paper is to disseminate knowledge in the seismic science community about a possible tool which is not largely
popular, despite its potential usefulness. In this paper it will be shown how satellite remotely sensed images may represent
a powerful source of information where traditional sources of information are unable to deliver it, or at least to do so timely.
Even when traditional information flow can ensure delivery, an advantage may still be found in terms of sooner availability
and smaller amount of labour required. In the case shown here a vulnerability study was made on a vast industrial area in
the gulf of Siracusa, Sicily, Italy. A series of concurrent factors made it particularly troublesome to obtain information
on the structures found in the site (tanks, pipes, chimneys, roads, ...), required to suitably carry out the study. Satellite
images were then acquired to obtain the information needed. Processing of the images was carried out relying on in-house software
formerly developed for similar information extraction issues, and integrated with new, specifically developed elements, some
pieces of information were obtained useful for seismic risk evaluation. In particular, location, footprint, elevation of significant
structures (e.g. tanks, chimneys) could be evaluated, obtaining results in a format compatible with the most widespread GIS
(Geographic Information System) standards. Such compatibility allowed a considerable savings on labour time required to lay
a GIS of the area, which is a fundamental tool for risk and vulnerability analyses. 相似文献