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81.
Serge Fourcade Laurent Trotignon Philippe Boulvais Isabelle Techer Marcel Elie Didier Vandamme Elias Salameh Hani Khoury 《Applied Geochemistry》2007
The Khushaym Matruk site in central Jordan may represent a natural analogue depicting the interaction of alkaline solutions with a clayey sedimentary formation or with clay-rich confining barriers at the interface with concrete structures in waste disposal sites. In this locality, past spontaneous combustion of organic matter in a clayey biomicritic formation produced a ca. 60 m-thick layer of cement-marble containing some of the high-temperature phases usually found in industrial cements (e.g., spurrite, brucite, and Ca-aluminate). A vertical cross-section of the underlying sediments was used in order to study the interaction between cement-marbles and neighbouring clayey limestones under weathering conditions. A thermodynamic approach of the alteration parageneses (calcite–jennite–afwillite–brucite and CSH phases) in the cement-marbles constrains the interacting solutions to have had pH-values between 10.5 and 12. Over 3 m, the sediments located beneath the metamorphic unit were compacted and underwent carbonation. They display large C and O isotopic variations with respect to “pristine” sediments from the bottom of the section. Low δ13C-values down to −31.4‰/PDB show the contribution of CO2 derived from the oxidization of organic matter and from the atmosphere to the intense carbonation process affecting that particular sedimentary level. The size of the C isotopic anomalies, their geometrical extent and their coincidence with the variations of other markers like the Zn content, the structure of organic matter, the mineralogical composition, all argue that the carbonation process was induced by the percolation of high pH solutions which derived from the alteration of cement-marbles. The temperature of the carbonation process remains conjectural and some post-formation O isotopic reequilibration likely affected the newly-formed carbonate. Carbonation induced a considerable porosity reduction, both in fractures and matrixes. The Khushaym Matruk site may have some bearing to the early life of a repository site, when water saturation of the geological formations hosting the concrete structures is incomplete, enabling simultaneous diffusion of alkaline waters and gaseous CO2 in the near field. 相似文献
82.
Marcel Elie Isabelle Techer Laurent Trotignon Hani Khoury Elias Salameh Didier Vandamme Philippe Boulvais Serge Fourcade 《Applied Geochemistry》2007
Spontaneous combustion, less than 1 Ma ago, affected a 60-m thick sediment pile of biomicrite at the Khushaym Matruck site (Jordan). The present study shows that three retrograde alteration stages occurred: weathering, thermal stress and oxidative alkaline perturbation. μ-FT-i.r. spectra of isolated kerogens and oxygen index of whole rocks indicate that oxidation of organic matter occurred down to ∼10 m beneath the metamorphosed zone at Khushaym Matruck. The occurrence of the oxidative weathering bacterially mediated, as suggested by the mass chromatograms of saturated hydrocarbons, can explain high Rock-Eval Tmax values and low petroliferous potential measured along the sedimentary pile. On the other hand, the thermal extent of combustion events was limited to the first 2 m from the contact. The mean reflectance of 0.20–0.24% and porosity of ca. 50% of the grey clayey biomicrites indicate that organic matter was very immature and sediments were unconsolidated at the time of the combustion event. Using mineralogy, microscopic analyses of vegetable debris and magnetic susceptibility, a suite of characteristic points corresponding to the thermal imprint can be assessed: (i) x = 0m, T ∼ 1000 °C, (ii) x = 1 m, T ∼ 350 °C, (iii) x = 2 m, T ∼ 150 °C and (iv) x > ∼ 8 m, T ∼ 30 °C. Paleocirculation of meteoric groundwater in the ‘cement-marbles’ generated high-pH fluids that have circulated via fractures and through the matrix porosity of the underlying biomicrites but have also induced alkaline hydrolysis and oxidative attack of the organic matter. The polysaccharide/lignin ratio derived from μ-FT-i.r. analyses shows that the delignification of vegetable debris and degradation of polysaccharides progressively decline in the indurated zone, which indicates a decrease in the pH of migrating solutions. The latter also severely oxidized organic matter at 2.10 and 3.05 m as revealed by the oxygen index and induced the generation of bitumen. The spatial correlation between the oxidation levels of organic matter and the metal contents (Fe, Ti and Cr) suggests that redox reactions were responsible for the immobilization of metals in the indurated biomicrites. The intensity of these reactions is attributed to changes in the fluid flow regime within the sedimentary column. 相似文献
83.
A portable erosion device (ERIS) was deployed in November 2000 and May 2001 to investigate the spatio-temporal variation of fine-grained sediment erosion over a transect on the intertidal mudflats of Marennes-Oléron Bay, western France. The objective was to relate changes in bed erodability over diurnal emersion periods to bioturbation, rapid changes in sediment characteristics, and microphytobenthos biomass. 相似文献
84.
Hugues?Cabane Didier?LaporteEmail author Ariel?Provost 《Contributions to Mineralogy and Petrology》2005,150(1):37-53
We carried out an experimental study to characterize the kinetics of Ostwald ripening in the forsterite-basalt system and
in the plagioclase (An65)-andesite system. Eight experiments were done in each system to monitor the evolution of mean grain size and crystal size
distribution (CSD) with time t; the experiments were performed in a 1-atmosphere quench furnace, at 1,250°C for plagioclase and 1,300°C for olivine. Very
contrasted coarsening kinetics were observed in the two series. In the plagioclase series, the mean grain size increased as
log(t), from ≈3 μm to only 8.7 μm in 336 h. The kinetic law in log(t) means that Ostwald ripening was rate-limited by surface nucleation at plagioclase-liquid interfaces. In the olivine series,
the mean grain size increased as t
1/3, from ≈3 μm to 23.2 μm in 496 h. A kinetic law in t
1/3 is expected when Ostwald ripening is rate-limited either by diffusion in the liquid or by grain growth/dissolution controlled
by a screw dislocation mechanism. The shape of olivine CSDs, in particular their positive skewness, indicates that grain coarsening
in the olivine experiments was controlled by a screw dislocation mechanism, not by diffusion. As the degrees of undercooling
ΔT (or supersaturation) involved in Ostwald ripening are essentially <1°C, the mechanisms of crystal growth identified in our
experiments are expected to be those prevailing during the slow crystallisation of large magma chambers. We extrapolated our
experimental data to geological time scales to estimate the effect of Ostwald ripening on the size of crystals in magmas.
In the case of plagioclase, Ostwald ripening is only efficient for mean grain sizes of a few microns to 20 μm, even for a
time scale of 105 years. It can, however, result in a significant decrease of the number of small crystals per unit volume, and contribute
to the development of convex upwards CSDs. For olivine, the mean grain size increases from 2–3 μm to ≈70 μm in 1 year and
700 μm in 103 years; a mean grain size of 3 mm is reached in 105 years. Accordingly, the rate of grain size-dependent processes, such as compaction of olivine-rich cumulates or melt extraction
from partially molten peridotites, may significantly be enhanced by textural coarsening. 相似文献
85.
Michel Paillard Marc Prevosto Stephen F. Barstow Carlos Guedes Soares 《Coastal Engineering》2000,40(4):906
The MAST II WAVEMOD Project aimed at improving stochastic modelling of ocean waves and currents in coastal waters. In order to supplement existing data, two measurement campaigns were carried out, one on the Atlantic coast of Portugal, and, secondly, on the northern coast of Crete in the Mediterranean. The Portuguese measurements covered 7 months during winter 1993–1994, while off Crete, measurements started early in February 1994 and continued for 10 months. In both sites, two directional Waveriders and one non-directional Waverider were deployed along a transect out from the coast in water depths between 10 and 100 m. In addition, the Mediterranean site also incorporated measurements of mean current velocities. Available satellite data were analysed to supplement the buoy data. In this paper, both measurement campaigns are described together with a presentation of some of the data collected. 相似文献
86.
87.
88.
Xuebin Zhang John A. Church Skye M. Platten Didier Monselesan 《Climate Dynamics》2014,43(1-2):131-144
For all of the IPCC Special Report on Emission Scenarios (SRESs), sea level is projected to rise globally. However, sea level changes are not expected to be geographically uniform, with many regions departing significantly from the global average. Some of regional distributions of sea level changes can be explained by projected changes of ocean density and dynamics. In this study, with 11 available Coupled Model Intercomparison Project Phase 3 climate models under the SRES A1B, we identify an asymmetric feature (not recognised in previous studies) of projected subtropical gyre circulation changes and associated sea level changes between the North and South Pacific, through analysing projected changes of ocean dynamic height (with reference to 2,000 db), depth integrated steric height, Sverdrup stream function, surface wind stress and its curl. Poleward expansion of the subtropical gyres is projected in the upper ocean for both North and South Pacific. Contrastingly, the subtropical gyre circulation is projected to spin down by about 20 % in the subsurface North Pacific from the main thermocline around 400 m to at least 2,000 m, while the South Pacific subtropical gyre is projected to strengthen by about 25 % and expand poleward in the subsurface to at least 2,000 m. This asymmetrical distribution of the projected subtropical gyre circulation changes is directly related to differences in projected changes of temperature and salinity between the North and South Pacific, forced by surface heat and freshwater fluxes, and surface wind stress changes. 相似文献
89.
Stéphane Reboulet Peter F. Rawson Josep A. Moreno-Bedmar Maria B. Aguirre-Urreta Ricardo Barragán Yuri Bogomolov Miguel Company Celestina González-Arreola Vyara Idakieva Stoyanova Alexander Lukeneder Bertrand Matrion Vasily Mitta Hasina Randrianaly Zdenek Vaši?ek Evgenij J. Baraboshkin Didier Bert Stéphane Bersac Tamara N. Bogdanova Luc G. Bulot Jean-Louis Latil Irina A. Mikhailova Pierre Ropolo Ottilia Szives 《Cretaceous Research》2011,32(6):786-793
The 4th Kilian Group meeting (Dijon, France, 30th August 2010) focused on the Aptian and Albian Stages. For the Aptian, a two-fold division of the stage was adopted for the Mediterranean area with a boundary between the Dufrenoyia furcata and Epicheloniceras martini Zones. The main changes to the zonal scheme concern the Lower Aptian with: the introduction of a Deshayesites luppovi Subzone in the upper part of the Deshayesites oglanlensis Zone; the replacement of Deshayesites weissi by Deshayesites forbesi as new index-species of the second interval zone; the introduction of a Roloboceras hambrovi Subzone in the upper part of the D. forbesi Zone; and the subdivision of the D. furcata Zone into the D. furcata and Dufrenoyia dufrenoyi Subzones. For the Albian, the upper part of the Douvilleiceras mammillatum Zone (Lower Albian) is now characterized by a Lyelliceras pseudolyelli Subzone. The main amendments concern the Upper Albian. The base of this substage is defined by the base of the Dipoloceras cristatum Zone. Above it, the Upper Albian zonal scheme comprises in stratigraphic order the Mortoniceras pricei, Mortoniceras inflatum, Mortoniceras fallax, Mortoniceras rostratum, Mortoniceras perinflatum and Arrhaphoceras briacensis Zones. 相似文献
90.
Reservoir characterization needs the integration of various data through history matching, especially dynamic information
such as production or four-dimensional seismic data. To update geostatistical realizations, the local gradual deformation
method can be used. However, history matching is a complex inverse problem, and the computational effort in terms of the number
of reservoir simulations required in the optimization procedure increases with the number of matching parameters. History
matching large fields with a large number of parameters has been an ongoing challenge in reservoir simulation. This paper
presents a new technique to improve history matching with the local gradual deformation method using the gradient-based optimizations.
The new approach is based on the approximate derivative calculations using the partial separability of the objective function.
The objective function is first split into local components, and only the most influential parameters in each component are
used for the derivative computation. A perturbation design is then proposed to simultaneously compute all the derivatives
with only a few simulations. This new technique makes history matching using the local gradual deformation method with large
numbers of parameters tractable. 相似文献