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71.
72.
Manuela Rossi Marcella Dell’Aglio Alessandro De Giacomo Rosalba Gaudiuso Giorgio Saverio Senesi Olga De Pascale Francesco Capitelli Fabrizio Nestola Maria Rosaria Ghiara 《Physics and Chemistry of Minerals》2014,41(2):127-140
Gem-quality alexandrite, hiddenite and kunzite, elbaite and topaz minerals were characterized through a multi-methodological investigation based on EMPA-WDS, LA-ICP-MS, and laser-induced breakdown spectroscopy (LIBS). With respect to the others, the latter technique enables a simultaneous multi-elemental composition without any sample preparation and the detection of light elements, such as Li, Be and B. The criteria for the choice of minerals were: (a) the presence of chromophore elements in minor contents and/or as traces; (b) the presence of light lithophile elements (Li, Be and B); (c) different crystal chemistry complexity. The results show that LIBS can be employed in mineralogical studies for the identification and characterization of minerals, and as a fast screening method to determine the chemical composition, including the chromophore and light lithophile elements. 相似文献
73.
Eleonora Ammannito M. Cristina De Sanctis Fabrizio Capaccioni M. Teresa Capria F. Carraro Jean‐Philippe Combe Sergio Fonte Alessandro Frigeri Steven P. Joy Andrea Longobardo Gianfranco Magni Simone Marchi Thomas B. McCord Lucy A. McFadden Harry Y. McSween Ernesto Palomba Carle M. Pieters Carol A. Polanskey Carol A. Raymond Jessica M. Sunshine Federico Tosi Francesca Zambon Christopher T. Russell 《Meteoritics & planetary science》2013,48(11):2185-2198
We present global lithological maps of the Vestan surface based on Dawn mission's Visible InfraRed (VIR) Spectrometer acquisitions with a spatial sampling of 200 m. The maps confirm the results obtained with the data set acquired by VIR with a spatial sampling of 700 m, that the reflectance spectra of Vesta's surface are dominated by pyroxene absorptions that can be interpreted within the context of the distribution of howardites, eucrites, and diogenites (HEDs). The maps also partially agree with the ground and Hubble Space Telescope observations: they confirm the background surface being an assemblage of howardite or polymict eucrite, as well as the location of a diogenitic‐rich spot; however, there is no evidence of extended olivine‐rich regions in the equatorial latitudes. Diogenite is revealed on the Rheasilvia basin floor, indicating that material of the lower crust/mantle was exposed. VIR also detected diogenites along the scarp of Matronalia Rupes, and the rims of Severina and a nearby, unnamed crater, and as ejecta of Antonia crater. The diogenite distribution is fully consistent with petrological constraints; although the mapped distribution does not provide unambiguous constraints, it favors the hypothesis of a magma ocean. 相似文献
74.
Francesco?PandolfoEmail author Fabrizio?Nestola Fernando?Cámara M.?Chiara?Domeneghetti 《Physics and Chemistry of Minerals》2012,39(4):295-304
The compressibility at room temperature and the thermal expansion at room pressure of two disordered crystals (space group
C2/c) obtained by annealing a natural omphacite sample (space group P2/n) of composition close to Jd56Di44 and Jd55Di45, respectively, have been studied by single-crystal X-ray diffraction. Using a Birch–Murnaghan equation of state truncated
at the third order [BM3-EoS], we have obtained the following coefficients: V
0 = 421.04(7) Å3, K
T0 = 119(2) GPa, K′ = 5.7(6). A parameterized form of the BM3 EoS was used to determine the axial moduli of a, b and c. The anisotropy scheme is β
c
≤ β
a
≤ β
b
, with an anisotropy ratio 1.05:1.00:1.07. A fitting of the lattice variation as a function of temperature, allowing for linear
dependency of the thermal expansion coefficient on the temperature, yielded αV(1bar,303K) = 2.64(2) × 10−5 K−1 and an axial thermal expansion anisotropy of α
b
≫ α
a
> α
c
. Comparison of our results with available data on compressibility and thermal expansion shows that while a reasonable ideal
behaviour can be proposed for the compressibility of clinopyroxenes in the jadeite–diopside binary join [K
T0 as a function of Jd molar %: K
T0 = 106(1) GPa + 0.28(2) × Jd(mol%)], the available data have not sufficient quality to extract the behaviour of thermal expansion for the same binary join in
terms of composition. 相似文献
75.
76.
A comparison of seismic risk maps for Italy 总被引:5,自引:3,他引:2
Helen Crowley Miriam Colombi Barbara Borzi Marta Faravelli Mauro Onida Manuel Lopez Diego Polli Fabrizio Meroni Rui Pinho 《Bulletin of Earthquake Engineering》2009,7(1):149-180
National seismic risk maps are an important risk mitigation tool as they can be used for the prioritization of regions within
a country where retrofitting of the building stock or other risk mitigation measures should take place. The production of
a seismic risk map involves the convolution of seismic hazard data, vulnerability predictions for the building stock and exposure
data. The seismic risk maps produced in Italy over the past 10 years are compared in this paper with recent proposals for
seismic risk maps based on state-of-the-art seismic hazard data and mechanics-based vulnerability assessment procedures. The
aim of the paper is to open the discussion for the way in which future seismic risk maps could be produced, making use of
the most up-to-date information in the fields of seismic hazard evaluation and vulnerability assessment. 相似文献
77.
Fabrizio Frontalini Carla Buosi Rodolfo Coccioni Carla Bucci 《Marine pollution bulletin》2009,58(6):858-877
In order to assess the response of benthic foraminifera to trace element pollution, a study of benthic foraminiferal assemblages was carried out into sediment samples collected from the Santa Gilla lagoon (Sardinia, Italy). The lagoon has been contaminated by industrial waste, mainly trace elements, as well as by agricultural and domestic effluent. The analysis of surficial sediment shows enrichment in trace elements, including Cr, Cu, Hg, Ni, Pb and Zn. Biotic and abiotic data, analyzed with multivariate techniques of statistical analysis, reveal a distinct separation of both the highly polluted and less polluted sampling sites. The innermost part of the lagoon, comprising the industrial complex at Macchiareddu, is exposed to a high load of trace elements which are probably enhanced by their accumulation in the finer sediment fraction. This area reveals lower diversity and higher percentages of abnormalities when compared to the outermost part of the lagoon. 相似文献
78.
79.
Drying and dying of a subducted slab: Coupled Li and B isotope variations in Western Anatolia Cenozoic Volcanism 总被引:1,自引:0,他引:1
Samuele Agostini Jeffrey G. Ryan Sonia Tonarini Fabrizio Innocenti 《Earth and Planetary Science Letters》2008,272(1-2):139-147
In lavas spanning ~ 10Ma of subduction-related volcanism in Western Anatolia, we observe remarkably similar patterns of δ7Li and δ11B variation. In this setting, magmatism records a transition from calc–alkaline to ultrapotassic character, consistent with overall lower mean extents of melting, and a changing mantle source that reflects a fractionating, higher temperature slab input consistent with the gradual cessation of subduction. Subsequent rift-related intraplate magmatism record δ7Li signatures within the range observed for MORBs and OIBs, indicating an abrupt transition to a mantle source unmodified by subduction. 相似文献
80.
Marco Patacci Mattia Marini Fabrizio Felletti Andrea Di Giulio Massimo Setti William McCaffrey 《Sedimentology》2020,67(5):2625-2644
The partitioning of different grain-size classes in gravity flow deposits is one of the key characteristics used to infer depositional processes. Turbidites have relatively clean sandstones with most of their clay deposited as part of a mudstone cap or as a distal mudstone layer, whereas sand-bearing debrites commonly comprise mixtures of sand grains and interstitial clay; hybrid event beds develop alternations of clean and dirty (clay-rich) sandstones in varying proportions. Analysis of co-genetic mudstone caps in terms of thickness and composition is a novel approach that can provide new insight into gravity flow depositional processes. Bed thickness data from the ponded Castagnola system show that turbidites contain more clay overall than do hybrid event beds. The Castagnola system is characterized by deposits of two very different petrographic types. Thanks to this duality, analyses of sandstone and mudstone composition allow inference of which proportion of the clay in each of the deposit types was acquired en route. In combination with standard sedimentological observations the new data allow insight into the likely characteristics of their parent flows. Clean turbidites were deposited by lower concentration, long duration, erosive, muddy turbidity currents which were more efficient at fractionating clay particles away from their basal layer. Hybrid event beds were deposited by shorter duration, higher-concentration, less-erosive sandier flows which were less efficient at clay fractionation. The results are consistent with data from other turbidite systems (for example, Marnoso-arenacea). The approach represents a new method to infer the controls on the degree of clay partitioning in gravity flow deposits. 相似文献