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51.
Claudio Marchesi José María González-Jiménez Fernando Gervilla Carlos J. Garrido William L. Griffin Suzanne Y. O’Reilly Joaquín A. Proenza Norman J. Pearson 《Contributions to Mineralogy and Petrology》2011,161(6):977-990
Chromitite pods in the Mayarí-Cristal ophiolitic massif (eastern Cuba) were formed in the Late Cretaceous when island arc
tholeiites and MORB-like back-arc basin basalts reacted with residual mantle peridotites and generated chromite-rich bodies
enclosed in dunite envelopes. Platinum-group minerals (PGM) in the podiform chromitites exhibit important Os-isotope heterogeneities
at the kilometric, hand sample and thin section scales. 187Os/188Os calculated at the time of chromitite crystallization (~90 Ma) ranges between 0.1185 and 0.1295 (γOs = −7.1 to +1.6, relative
to enstatite chondrite), and all but one PGM have subchondritic 187Os/188Os. Grains in a single hand sample have initial 187Os/188Os that spans from 0.1185 to 0.1274, and in one thin section it varies between 0.1185 and 0.1232 in two PGM included in chromite
which are only several millimeters apart. As the Os budget of a single micrometric grain derives from a mantle region that
was at least several m3 in size, the variable Os isotopic composition of PGM in the Mayarí-Cristal chromitites probably reflects the heterogeneity
of their mantle sources on the 10–100 m scale. Our results show that this heterogeneity was not erased by pooling and mingling
of individual melt batches during chromitite crystallization but was transferred to the ore deposits on mineral scale. The
distribution of the Os model ages calculated for PGM shows four main peaks, at ~100, 500, 750 and 1,000 Ma. These variable
Os model ages reflect the presence of different depleted domains in the oceanic (Pacific-related) upper mantle of the Greater
Antilles paleo-subduction zone. The concordance between the age of crystallization of the Mayarí-Cristal chromitites and the
most recent peak of the Os model age distribution in PGM supports that Os in several grains was derived from fertile domains
of the upper mantle, whose bulk Os isotopic composition is best approximated by that of enstatite chondrites; on the other
hand, most PGM are crystallized by melts that tapped highly refractory mantle sources. 相似文献
52.
Groundwater optimization model for sustainable management of the Valley of Puebla aquifer, Mexico 总被引:1,自引:1,他引:0
Edith R. Salcedo-Sánchez Ma. Vicenta Esteller Sofía E. Garrido Hoyos Manuel Martínez-Morales 《Environmental Earth Sciences》2013,70(1):337-351
The Valley of Puebla aquifer (VPA), at the central region of Mexico, is subject to intensive exploitation to satisfy the urban and industrial demand in the region. As a result of this increased exploitation, a number of state and federal agencies in charge of water management are concerned about the problems associated with the aquifer (decline of groundwater table, deterioration in water quality, poor well productivity and increased pumping and water treatment costs). This study presents a groundwater management model that combines “MODFLOW” simulation with optimization tools “MODRSP”. This simulation–optimization model for groundwater evaluates a complex range of management options to identify the strategies that best fit the objectives for allocating resources in the VPA. Four hypothetical scenarios were defined to analyze the response of the hydrogeological system for future pumping schemes. Based on the simulation of flow with the MODFLOW program, promising results for the implementation of the optimization of water quantity were found in scenarios 3 and 4. However, upon comparison and analysis of the feasibility of recovery of the piezometric level (considering the policy of gradual reductions of pumping), scenario 4 was selected for optimization purposes. The response functions of scenario 4 were then obtained and optimized, establishing an extraction rate of 204.92 millions of m3/year (Mm3/year). The reduction in groundwater extraction will be possible by substituting the volume removed by 35 wells (that should be discontinued) by the same volume of water from another source. 相似文献
53.
Claudio D. Miranda Rodrigo Rojas Marcela Garrido Julieta Geisse Gerardo González 《Marine pollution bulletin》2013
The main aim of this study was to determine the occurrence of resistant bacteria in florfenicol-treated and untreated scallop larval cultures from a commercial hatchery and to characterize some selected florfenicol-resistant strains. Larval cultures from untreated and treated rearing tanks exhibited percentages of copiotrophic bacteria resistant to florfenicol ranging from 0.03% to 10.67% and 0.49–18.34%, respectively, whereas florfenicol resistance among oligotrophic bacteria varied from 1.44% to 35.50% and 3.62–95.71%, from untreated and treated larvae, respectively. Florfenicol resistant microbiota from reared scallop larvae mainly belonged to the Pseudomonas and Pseudoalteromonas genus and were mainly resistant to florfenicol, chloramphenicol, streptomycin and co-trimoxazole. This is the first study reporting antimicrobial resistant bacteria associated to a shellfish hatchery and the results suggest that a continuous surveillance of antimicrobial resistance even in absence of antibacterial therapy is urgently required to evaluate potential undesirable consequences on the surrounding environments. 相似文献
54.
55.
Granada oscillation code (GraCo) is a software constructed to compute adiabatic and non-adiabatic oscillation eigenfunctions and eigenvalues. The adiabatic version gives the standard numerical resolution, and also the Richardson extrapolation, different sets of eigenfunctions, different outer mechanical boundary conditions or different integration variables. The non-adiabatic version can include the atmosphere-pulsation interaction. The code has been used for intensive studies of δ Scuti, γ Doradus, β Ceph., SdO and, SdB stars. The non adiabatic observables “phase-lag” (the phase between the effective temperature variations and the radial displacement) and ${\delta T_{\mathrm{eff}}\over T_{\mathrm{eff}}}$ (relative surface temperature variation) can help to the modal identification. These quantities together with the energy balance (“growth rate”) provide useful additional information to the adiabatic resolution (eigenfrequencies and eigenfunctions). 相似文献
56.
Francesca Rossi Celia Olabarria Mónica Incera Josefina Garrido 《Journal of Sea Research》2010,63(1):52-61
Native and exotic seaweeds frequently lie on the beach and sustain part of the benthic food web. However, the role of exotic seaweeds as food sources for beach consumers has been poorly studied. We studied the temporal and spatial variability in the trophic significance of the invasive brown seaweed Sargassum muticum on sandy beaches. We measured the stable isotopes (δ13C and δ15N) in the tissues of S. muticum and of invertebrate consumers and estimated the dietary biomass proportion of S. muticum during four sampling dates at two beaches and heights on the shore. Samples were collected from eight pitfall traps placed at a distance of 2 m from each other. Detrital macroalgae and seagrasses were also collected by hand within an area of 30 cm around each pitfall trap. We measured the spatial and temporal variability in the isotope composition of the beach consumers and of S. muticum using different models of analyses of variance. We then calculated the biomass proportion of S. muticum to the animal diet with a two-isotopic mixing model. The invasive alga S. muticum seemed to be one of the main food sources for the amphipod Talitrus saltator and, to a less extent, for the isopod Tylos europaeus. The importance of S. muticum was however temporally variable and decreased during spring (in March and May), probably due to the availability of native macrophytes. The supply of invasive wrack to beach food webs thus deserves more attention if we want to understand their role in influencing food web dynamics. 相似文献
57.
Garrido Mauricio Sepúlveda Exequiel Ortiz Julián Townley Brian 《Natural Resources Research》2020,29(6):3527-3545
Natural Resources Research - The access to real geometallurgical data is very limited in practice, making it difficult for practitioners, researchers and students to test methods, models and... 相似文献
58.
In this study, we used experimental manipulation of algal wrack to test hypotheses about influences on macrofaunal assemblages inhabiting the upper shore level of different sites along an exposed sandy beach. First, we hypothesized that decomposition of algal wrack depends on wrack patch size and site. With respect to macrofauna, we tested the hypotheses that (1) abundance of colonising individuals and species vary with wrack patch size, (2) succession (i.e. sequence of colonisation and species replacement) depends on time, and (3) as a result, macrofaunal assemblages associated with wrack patches vary with the patch size and time. We also predicted that responses could be different across sites because of their slightly different environmental conditions. The decomposition of wrack patches was similar in all sites and was dependent on wrack patch size. It was strongly influenced by time-specific environmental and/or biological factors. The pattern of colonisation, i.e. total number of species and individuals, varied among wrack patch sizes. Small patches had fewer species and individuals than medium and large patches. Nevertheless, pattern of colonisation varied among species, across sites and through time. Colonisation of wrack patches was rapid (i.e. within 3 days) for most species. There was some evidence to support the hypothesis that macrofaunal assemblages change in response to patch size and time. 相似文献
59.
Migration and accumulation of ultra-depleted subduction-related melts in the Massif du Sud ophiolite (New Caledonia) 总被引:1,自引:0,他引:1
Claudio Marchesi Carlos J. Garrido Marguerite Godard France Belley Eric Ferr 《Chemical Geology》2009,266(3-4):180-195
The Massif du Sud is a large ophiolitic complex that crops out in the southern region of New Caledonia (SW Pacific). It is dominated by harzburgite tectonite that locally shows a transitional gradation to massive dunite up section. Clinopyroxene, orthopyroxene and plagioclase progressively appear in dunite up to the transition to layered wehrlite and orthopyroxene–gabbro. The dunite–wehrlite and wehrlite–gabbro contacts are parallel and the latter defines the paleo-Moho.Highly depleted modal, mineral and bulk rock compositions indicate that harzburgites are residues after high degrees (20–30%) of partial melting mainly in the spinel-stability field. Their relative enrichment in HFSE, LREE and MREE is due to re-equilibration of melting residues with percolating melts. Dunite formed in the Moho transition zone by reaction between residual mantle harzburgite and olivine-saturated melts that led to pyroxene dissolution and olivine precipitation. Rare clinopyroxene and plagioclase crystallized in interstitial melt pores of dunite from primitive, low-TiO2, ultra-depleted liquids with a geochemical signature transitional between those of island arc tholeiites and boninites.Ascending batches of relatively high-SiO2, ultra-depleted melts migrated through the Moho transition zone and generated wehrlite by olivine dissolution and crystallization of clinopyroxene, orthopyroxene and plagioclase in variable amounts. These liquids were more evolved and were produced by higher degrees of melting or from a more depleted source compared with melts that locally crystallized clinopyroxene in dunite. Ultra-depleted magmas, non-cogenetic with those that formed the Moho transition zone, ascended to the lower crust and generated gabbroic cumulates with subduction-related affinity. Thus, the ultramafic and mafic rocks in the Moho transition zone and lower crust of the Massif du Sud ophiolite are not products of fractional crystallization from a single magma-type but are the result of migration and accumulation of different melts in a multi-stage evolution.The record of high partial melting in the mantle section, and migration and accumulation of ultra-depleted subduction-related melts in the Moho transition zone and lower crust support that the Massif du Sud ophiolite is a portion of forearc lithosphere generated in an extensional regime during the early phases of the subduction zone evolution. Our results show the existence of different types of ultra-depleted melt compositions arriving at the Moho transition zone and lower crust of an infant intraoceanic paleo-arc. Ultra-depleted melts may thus be a significant component of the melt budget generated in oceanic spreading forearcs prior to aggregation and mixing of a large range of melt compositions in the crust. 相似文献
60.
An experimental investigation of antigorite dehydration in natural silica-enriched serpentinite 总被引:1,自引:0,他引:1
José Alberto Padrón-Navarta Jörg Hermann Carlos J. Garrido Vicente López Sánchez-Vizcaíno María Teresa Gómez-Pugnaire 《Contributions to Mineralogy and Petrology》2010,159(1):25-42
Piston cylinder experiments were performed to constrain the pressure and temperature conditions for two high-pressure antigorite
dehydration reactions found in silica-enriched serpentinites from Cerro del Almirez (Nevado–Filábride Complex, Betic Cordillera,
southern Spain). At 630–660°C and pressures greater than 1.6 GPa, antigorite first reacts with talc to form orthopyroxene ± chlorite + fluid.
We show that orthopyroxene + antigorite is restricted to high-pressure metamorphism of silica-enriched serpentinite. This
uncommon assemblage is helpful in constraining metamorphic conditions in cold subduction environments, where antigorite serpentinites
have no diagnostic assemblages over a large pressure and temperature range. The second dehydration reaction leads to the breakdown
of antigorite to olivine + orthopyroxene + chlorite + fluid. The maximum stability of antigorite is found at 680°C at 1.9 GPa,
which also corresponds to the maximum pressure limit for tremolite coexisting with olivine + orthopyroxene. The high aluminium
(3.70 wt% Al2O3) and chromium contents (0.59 wt% Cr2O3) of antigorite in the investigated starting material is responsible for the expansion of the serpentinite stability to 60–70°C
higher temperatures at 1.8 GPa than the antigorite stability calculated in the Al-free system. The antigorite from our study
has the highest Al–Cr contents among all experimental studies and therefore likely constraints the maximum stability of antigorite
in natural systems. Comparison of experimental results with olivine–orthopyroxene–chlorite–tremolite assemblages outcropping
in Cerro del Almirez indicates that peak metamorphic conditions were 680–710°C and 1.6–1.9 GPa. 相似文献