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41.
<正>We report here new geochemical and geochronological data from mafic-ultramafic rock suites in the Ankara Mélange in north-central Turkey,and present a new tectonic model for its origin.Considered as one of most important relics of the Neotethyan realm in the region,the Ankara Mélange occurs between the Sakarya Continent 相似文献
42.
Carmela Freda Mario Gaeta Biagio Giaccio Fabrizio Marra Danilo M. Palladino Piergiorgio Scarlato Gianluca Sottili 《Bulletin of Volcanology》2011,73(3):241-256
Generally, the intensity and magnitude of explosive volcanic activity increase in parallel with SiO2 content. Pyroclastic-flow-forming eruptions in the Colli Albani ultrapotassic volcanic district (Italy) represent the most
striking exception on a global scale, with volumes on the order of tens of cubic kilometres and K-foiditic compositions (SiO2 even <42 wt.%). Here, we reconstruct the pre-eruptive scenario and event dynamics of the ~456 ka Pozzolane Rosse (PR) eruption,
the largest mafic explosive event of the Colli Albani district. In particular, we focus on the driving mechanisms for the
unusually explosive eruption of a low-viscosity, mafic magma. Geologic, petrographic and geochemical data with mass balance
calculations, supported by experimental data for Colli Albani magma compositions, provide evidence for significant ingestion
of carbonate wall rocks by the Pozzolane Rosse K-foiditic magma. Moreover, the scattered occurrence of cored bombs in Pozzolane
Rosse pyroclastic-flow deposits records carbonate entrainment even at the eruptive time scale, as also tested quantitatively
by thermal modelling of magma–carbonate interaction and carbonate assimilation experiments. We suggest that the addition of
free CO2 from decarbonation of country rocks was the major factor controlling magma explosivity. High CO2 activity in the volatile component, coupled with magma depressurisation, produced extensive leucite crystallisation at short
time scales, resulting in a dramatic increase in magma viscosity and volatile pressurisation, which was manifested a change
of eruptive dynamics from early effusion to the Pozzolane Rosse's highly explosive eruption climax. 相似文献
43.
Gianluca Masi 《Icarus》2003,163(2):389-397
The likely existence of bodies orbiting the Sun with aphelia Q < 0.983 AU has been suggested by numerical simulations of the dynamical evolution of the near-Earth objects (NEOs) population. For obvious reasons, these hypothetical minor bodies are called inner-Earth objects (IEOs). While much progresses has been made in learning more about the Amor, Apollo, and Aten population from surveys optimized for their discovery, no large, systematic, and similar observation projects devoted to the search of IEOs have been started. For their own orbital nature, IEOs can be observed only at small solar elongations (<90°), corresponding to regions of the sky currently neglected by the modern, ongoing surveys. This paper discusses a possible ground-based approach to look for IEOs, providing some useful tricks and the results of simulated surveys devoted to their discovery. It will be shown that such a search promises interesting results, the setup of a dedicated project being highly recommended. 相似文献
44.
Antonello Maruotti Antonio Punzo Gianluca Mastrantonio Francesco Lagona 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(6):1725-1740
The modelling of animal movement is an important ecological and environmental issue. It is well-known that animals change their movement patterns over time, according to observable and unobservable factors. To trace the dynamics of behaviors, to identify factors influencing these dynamics and unobserved characteristics driving intra-subjects correlations, we introduce a time-dependent mixed effects projected normal regression model. A set of animal-specific parameters following a hidden Markov chain is introduced to deal with unobserved heterogeneity. For the maximum likelihood estimation of the model parameters, we outline an expectation–maximization algorithm. A large-scale simulation study provides evidence on model behavior. The data analysis approach based on the proposed model is finally illustrated by an application to a dataset, which derives from a population of Talitrus saltator from the beach of Castiglione della Pescaia (Italy). 相似文献
45.
Gianluca Iezzi Zhenxian Liu Giancarlo Della Ventura 《Physics and Chemistry of Minerals》2009,36(6):343-354
The high-pressure behavior of three synthetic amphiboles crystallized with space group P21/m at room conditions in the system Li2O–Na2O–MgO–SiO2–H2O has been studied by in situ synchrotron infrared absorption spectroscopy. The amphiboles have compositions ANa B(Na
x
Li1 − x
Mg1) CMg5 Si8 O22(OH)2 with x = 0.6, 0.2 and 0.0, respectively. The high-P experiments up to 32 GPa were carried out on the U2A beamline at Brookhaven National Laboratory (NY, USA) using a diamond
anvil cell under non-hydrostatic or quasi-hydrostatic conditions. The two most intense absorption bands in the OH-stretching
infrared spectra can be assigned to two non-equivalent O–H dipoles in the P21/m structure, bonded to the same local environment M1M3Mg3–OH–ANa, and pointing toward two differently kinked tetrahedral rings. In all samples these bands progressively merge to give a
unique symmetrical absorption with increasing pressure, suggesting a change in symmetry from P21/m to C2/m. The pressure at which the transition occurs appears to be linearly correlated to the aggregate B-site dimension. The infrared
spectra collected for amphibole B(Na0.2Li0.8Mg1) in the frequency range 50 to 1,400 cm−1 also show a series of changes with increasing pressure. The data reported here support the inference of Iezzi et al. (Am
Miner 91:479–482, 2006a) regarding a new high-pressure amphibole polymorph. 相似文献
46.
Yola Georgiadou Gianluca Miscione Kate Lance Walter de Vries 《Earth Science Informatics》2009,2(4):271-282
While commercial virtual globes (e.g. Google Earth) and global scientific cyber-infrastructures (e.g. Digital Earth) are revolutionizing
the way we use and produce geo-information, we still lack a rich conceptual understanding of how genuine human actors use
geo-information and associated technologies in real work settings. In this paper, we conceptualize the use of geo-information
as encompassing people’s actual use practices, the values to which people aspire through geo-information use, and the rules that either legally prescribe or just encourage optimal use. Values, practices and rules can be illuminated from two perspectives
(or lenses), the market and the polis, resulting in radically different insights on the use of geo-information as a social phenomenon. We argue that with a polis
lens we stand a chance to explain how authentic human actors, groups and communities with different values, interests and
motivations use geo-information, and how societal benefits materialize or not as a result. Seen from a polis lens, values
are not easily measurable standards of goodness, dominant public management ideas can be the source of technical-organizational
change in government while policies can be fruitfully examined as persuasive arguments to target audiences. With a polis lens,
we are more likely to understand the emergence of new practices, value contests and global rules underpinning commercial virtual
globes and scientific cyber-infrastructures. 相似文献
47.
Gianluca Vignaroli Claudio Faccenna Federico Rossetti 《International Journal of Earth Sciences》2009,98(5):1077-1093
Geological mapping coupled with structural investigations carried out in the Voltri Massif (eastern Ligurian Alps, Italy)
provide new data for the interpretation of the tectonic context controlling main fabric development during exhumation of its
high-pressure core. The Voltri Massif is here interpreted as a c. 30 km-long eclogite-bearing, asymmetric dome formed by the
progressive verticalisation of the regional, second-phase mylonitic foliation developed during retrogressive greenschist metamorphic
conditions. In this light, the exhumation history is driven by a ductile-to-brittle extensional process, operating through
low-angle, top-to-the-W multiple detachment systems. A Late Eocene–Early Oligocene age for this extensional episode is proposed
on the basis of structural correlations, stratigraphic and radiometric constraints. In this scenario, the Voltri Massif is
interpreted as an extensional domain developed to accommodate the Late Eocene–Early Oligocene arching of the Western Alps–Northern
Apennines orogenic system. 相似文献
48.
Bilal Sarı 《Cretaceous Research》2009,30(5):1103-1132
Planktonic foraminifer distributions in seventeen stratigraphic sections of Upper Cretaceous hemipelagic and pelagic sequences of northern Bey Da?lar? Autochthon (western Taurides) yield six biozones such as, Dicarinella concavata Interval Zone, Dicarinella asymetrica Range Zone, Radotruncana calcarata Range Zone, Globotruncana falsostuarti Partial Range Zone, Gansserina gansseri Interval Zone, and Abathomphalus mayaroensis Concurrent Range Zone. Two of the zones, Dicarinella concavata Zone and Dicarinella asymetrica Zone, are identified in the massive hemipelagic limestones of the Bey Da?lar? Formation, of Coniacian-Santonian age. They are characterized by scarce planktonic foraminifera and abundant calcisphaerulids. The other four biozones are determined from the cherty pelagic limestones of the Akda? Formation and indicate a late Campanian-late Maastrichtian time interval. The planktonic foraminifera observed in these four biozones are diverse, complex morphotypes (K-selection), suggesting open oceans. The assemblage of the Abathomphalus mayaroensis Zone shows that the latest Maastrichtian record is absent throughout the northern part of the autochthon. Two main sedimentary hiatuses are recognized within the Upper Cretaceous pelagic sequence. Early to middle Campanian and latest Maastrichtian-middle Paleocene planktonic foraminifera are absent in all measured stratigraphic sections. Hiatus durations differ between sections as a result of diachronism of onset of the hemipelagic and pelagic deposition and the post-Santonian and post-Maastrichtian erosional phases. Drowning event and the early-middle Campanian and latest Maastrichtian-middle Paleocene hiatuses in the pelagic sequence are attributed to regional tectonics during the Late Cretaceous. 相似文献
49.
Mara Monica Tiberti Stefano Lorito Roberto Basili Vanja Kastelic Alessio Piatanesi Gianluca Valensise 《Pure and Applied Geophysics》2008,165(11-12):2117-2142
We calculated the expected impact on the Italian coast of the Adriatic Sea of a large set of tsunamis resulting from potential earthquakes generated by major fault zones. Our approach merges updated knowledge on the regional tectonics and scenario-like calculations of expected tsunami impact. We selected six elongated potential source zones. For each of them we determined a Maximum Credible Earthquake and the associated Typical Fault, described by its size, geometry and kinematics. We then let the Typical Fault float along strike of its parent source zone and simulated all tsunamis it could generate. Simulations are based on the solution of the nonlinear shallow water equations through a finite-difference technique. For each run we calculated the wavefields at specified simulation times and the maximum water height field (above mean sea level), then generated travel-time maps and maximum water height profiles along the target coastline. Maxima were also classified in a three-level code of expected tsunami threat. We found that the southern portion of Apulia facing Albania and the Gargano promontory are especially prone to the tsunami threat. We also found that some bathymetric features are crucial in determining the focalization-defocalization of tsunami energy. We suggest that our results be taken into account in the design of early-warning strategies. 相似文献
50.
A parallel computing thin‐sheet inversion algorithm for airborne time‐domain data utilising a variable overburden
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Tue Boesen Esben Auken Anders Vest Christiansen Gianluca Fiandaca Cyril Schamper 《Geophysical Prospecting》2018,66(7):1402-1414
Accurate modelling of the conductivity structure of mineralisations can often be difficult. In order to remedy this, a parametric approach is often used. We have developed a parametric thin‐sheet code, with a variable overburden. The code is capable of performing inversions of time‐domain airborne electromagnetic data, and it has been tested successfully on both synthetic data and field data. The code implements an integral solution containing one or more conductive sheets, buried in a half‐space with a laterally varying conductive overburden. This implementation increases the area of applicability compared to, for example, codes operating in free space, but it comes with a significant increase in computational cost. To minimise the cost, the code is parallelised using OpenMP and heavily optimised, which means that inversions of field data can be performed in hours on multiprocessor desktop computers. The code models the full system transfer function of the electromagnetic system, including variable flight height. The code is demonstrated with a synthetic example imitating a mineralisation buried underneath a conductive meadow. As a field example, the Valen mineral deposit, which is a graphite mineral deposit located in a variable overburden, is successfully inverted. Our results match well with previous models of the deposit; however, our predicted sheet remains inconclusive. These examples collectively demonstrate the effectiveness of our thin‐sheet code. 相似文献