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61.
Liliane Janikian Renato Paes de Almeida Antonio Romalino Santos Fragoso-Cesar Veridiana Teixeira de Souza Martins Elton Luiz Dantas Eric Tohver Ian McReath Manoel Souza D'Agrella-Filho 《Gondwana Research》2012,21(2-3):466-482
During the Ediacaran, southern Brazil was the site of multiple episodes of volcanism and sedimentation, which are best preserved in the 3000 km2 Camaquã Basin. The interlayered sedimentary and volcanic rocks record tectonic events and paleoenvironmental changes in a more than 10 km-thick succession. In this contribution, we report new U–Pb and Sm–Nd geochronological constraints for the 605 to 580 Ma Bom Jardim Group, the 570 Ma Acampamento Velho Formation, and a newly-recognized 544 Ma volcanism. Depositional patterns of these units reveal the transition from a restricted, fault-bounded basin into a wide, shallow basin. The expansion of the basin and diminished subsidence rates are demonstrated by increasing areal distribution and compressed isopachs and increasing onlap of sediments onto the basement to the west. The Sm–Nd isotopic composition of the volcanic rocks indicates mixed sources, including crustal rocks from the adjacent basement. Both Neoproterozoic and Paleoproterozoic sources are indicated for the western part of the basin, whereas only the older Paleoproterozoic signature can be discerned in the eastern part of the basin. 相似文献
62.
By means of multi-temporal analysis of satellite images and statistical algorithms, the amount of pyroclastic material deposited
on Lascar volcano walls after the gravitational collapse of the eruptive column caused by the eruption that occurred on April
the 19th and the 20th in 1993 was determined and quantified. For this analysis, scenes corresponding to Landsat 4 TM in 1989
and Landsat 7 ETM+ in 2001 were used. By careful selection methods such as combination of bands, unsupervised classification,
and the Karhunen–Loève transform, detailed analysis of zones of change that correspond to pyroclastic deposits were made.
This analysis was complemented with in situ data in order to correct and calibrate the satellite images to identify zones
of 1993s eruption pyroclastic deposits. Using Kittler’s and other thresholding algorithms, a search was performed for a proper
threshold to binarize the images to determine the surface area covered by the eruptive process. Matlab™ software was used
both for general programming and for digital image processing. 相似文献
63.
Renato De Santis 《Monthly notices of the Royal Astronomical Society》2001,326(1):397-402
In this paper, by assuming the equilibrium temperatures of RRab Lyrae variables defined by Carney, Storm & Jones as correct we show that temperatures derived from ( B − V ) colour (mean colour over the pulsational cycle calculated on the magnitude scale) transformations by Bessel, Castelli & Plez are consistent with the Carney et al. equilibrium temperatures within a probable error of δ log T e =±0.003 . As a consequence, it is shown that the pulsational temperature scale temperature–period–blue amplitude [ T eff = f ( P , A B )] relation provided by De Santis, who studied the ( B − V ) colour of about 70 stars of Lub's sample, is a suitable relation, being reddening- and metallicity-free, to calculate equilibrium temperatures for RRab variables. This relation is independent of variable mass and luminosity within a large range of period-shift from the mean period–amplitude relation valid for Lub's sample of variables. On the contrary, it is also shown that a temperature–amplitude–metallicity relation is strictly dependent on the period–amplitude relation of the sample used for calibrating it: we prove that this means it is dependent on both the mass and luminosity variations of variables. 相似文献
64.
Marco Mazzotti Renato Baciocchi Michael J. Desmond Robert H. Socolow 《Climatic change》2013,118(1):119-135
Direct Air Capture (DAC) of CO2 with chemicals, recently assessed in a dedicated study by the American Physical Society (APS), is further investigated with the aim of optimizing the design of the front-end section of its benchmark two-loop hydroxide-carbonate system. Two new correlations are developed that relate mass transfer and pressure drop to the air and liquid flow velocities in the countercurrent packed absorption column. These relationships enable an optimization to be performed over the parameters of the air contactor, specifically the velocities of air and liquid sorbent and the fraction of CO2 captured. Three structured Sulzer packings are considered: Mellapak-250Y, Mellapak-500Y, and Mellapak-CC. These differ in cost and pressure drop per unit length; Mellapak-CC is new and specifically designed for CO2 capture. Scaling laws are developed to estimate the costs of the alternative DAC systems relative to the APS benchmark, for plants capturing 1 Mt of CO2 per year from ambient air at 500 ppm CO2 concentration. The optimized avoided cost hardly differs across the three packing materials, ranging from $518/tCO2 for M-CC to $568/tCO2 for M-250Y. The $610/tCO2 avoided cost for the APS-DAC design used M-250 Y but was not optimized; thus, optimization with the same packing lowered the avoided cost of the APS system by 7 % and improved packing lowered the avoided cost by a further 9 % The overall optimization exercise confirms that capture from air with the APS benchmark system or systems with comparable avoided costs is not a competitive mitigation strategy as long as the energy system contains high-carbon power, since implementation of Carbon Capture and Storage, substitution with low-carbon power and end-use efficiency will offer lower avoided-cost strategies. 相似文献
65.
Talitha L. F. Costa Michelle P. Araújo Bastiaan A. Knoppers Renato S. Carreira 《Aquatic Geochemistry》2011,17(1):1-19
In the present work, we evaluated the origin of organic matter in the tropical estuarine-lagoon system of Mundaú–Manguaba,
NE Brazil, by considering the bulk (organic carbon and chlorophyll-a) and lipidic (n-alcohols and sterols) composition of suspended particles. Water samples were collected in August 2006 from
24 stations covering the salinity gradient from the rivers down to the sea outlet. Chlorophyll-a (Chl-a) varied from 22.7 to 134.1 μg L−1 in the lagoons, indicating eutrophic to hypertrophic conditions at the time of sampling. The high correlation between Chl-a and phytol together with the molar C:N ratio indicated the presence of fresh and recently produced autochthonous particulate
organic matter throughout the system, except for the river samples. The elevated concentrations of short-chain n-alcohols
and phytosterols, mainly 24-methylcholesta-5,24(28)-dien-3β-ol, also corroborated the predominance of autochthonous organic
matter in the lagoons but were generated by distinct sources: cianobacteria in the freshwater Manguaba lagoon and diatoms
in the brackish Mundaú lagoon compartments. Input of terrestrial organic matter was only detected in the rivers themselves
or at the upper river–lagoon interfaces. Coprostanol indicated contamination by sewage in Mundaú lagoon and in some rivers,
but at lower levels when compared to other Brazilian coastal lagoons and estuaries. 相似文献
66.
3D-electrical resistivity tomography monitoring of salt transport in homogeneous and layered soil samples 总被引:1,自引:1,他引:0
Cesare Comina Renato Maria Cosentini Gabriele Della Vecchia Sebastiano Foti Guido Musso 《Acta Geotechnica》2011,6(4):195-203
Monitoring transport of dissolved substances in soil deposits is particularly relevant where safety is concerned, as in the
case of geo-environmental barriers. Geophysical methods are very appealing, since they cover a wide domain, localising possible
preferential flow paths and providing reliable links between geophysical quantities and hydrological variables. This paper
describes a 3D laboratory application of electrical resistivity tomography (ERT) used to monitor solute transport processes.
Dissolution and transport tests on both homogeneous and heterogeneous samples were conducted in an instrumented oedometer
cell. ERT was used to create maps of electrical conductivity of the monitored domain at different time intervals and to estimate
concentration variations within the interstitial fluid. Comparisons with finite element simulations of the transport processes
were performed to check the consistency of the results. Tests confirmed that the technique can monitor salt transport, infer
the hydro-chemical behaviour of heterogeneous geomaterials and evaluate the performances of clay barriers. 相似文献
67.
Marco Milazzo Angelo Palmeri Jesús M. Falcón Fabio Badalamenti Jose A. Garcìa‐Charton Mauro Sinopoli Renato Chemello Alberto Brito 《Marine Ecology》2011,32(4):521-531
Changes in the shore topography (e.g. slope) occur at a scale of hundreds of meters in several locations in the Lusitanian and the Mediterranean Sea provinces. We tested whether differences in the bottom inclination might affect the vertical distribution patterns of two sympatric coastal labrid fishes, the rainbow wrasse Coris julis and the ornate wrasse Thalassoma pavo. Visual censuses were used to determine the distribution and abundance of these labrid species in high (≥30°) and low (≤3°) slope rocky substrates covered by brown macroalgae and at two different depths (shallow, 4–7 m, and deep 14–20 m). Pectoral fin aspect ratio was used as an estimate of swimming performance to potentially explain the patterns observed. Despite the intrinsic biogeographical differences in the overall density of T. pavo and C. julis, on steep coasts the ornate wrasse dominated in shallow waters, whereas the two species coexisted both in shallow and deeper depths on gentle slope coasts. These distribution patterns were consistent across locations, and fin aspect ratio was not a good predictor of between‐habitat use for wrasses. We show that, under specific topographical conditions, the depth segregation pattern seems to be an interactive segregation (likely related to resource competition) rather than a result of selective segregation due to morphological differences in the pectoral fin. Significant ecological changes might occur in locations where the density of T. pavo has recently increased as a result of water warming. 相似文献
68.
This study first explores the role of spatial heterogeneity, in both the saturated hydraulic conductivity Ks and rainfall intensity r, on the integrated hydrological response of a natural slope. On this basis, a mathematical model for estimating the expected areal‐average infiltration is then formulated. Both Ks and r are considered as random variables with assessed probability density functions. The model relies upon a semi‐analytical component, which describes the directly infiltrated rainfall, and an empirical component, which accounts further for the infiltration of surface water running downslope into pervious soils (the run‐on effect). Monte Carlo simulations over a clay loam soil and a sandy loam soil were performed for constructing the ensemble averages of field‐scale infiltration used for model validation. The model produced very accurate estimates of the expected field‐scale infiltration rate, as well as of the outflow generated by significant rainfall events. Furthermore, the two model components were found to interact appropriately for different weights of the two infiltration mechanisms involved. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
69.
Summary Occurrence of (Fe, Mg)-carpholite-bearing parageneses in metapelites from Giglio and Gorgona islands (Tuscan Archipelago,
Northern Tyrrhenian Sea) attests a continuity of blueschist metamorphism from Alpine Corsica to the Tuscan region. Numerous
fluid inclusions have been trapped in quartz crystals associated with (Fe, Mg)-carpholite fibers from the two blueschist metamorphic
cores. Textures of fluid inclusions (annular, semi-annular, negative crystal shaped), microthermometry (constancy of values)
and SEM investigations (presence of primary Fe-rich fluid/s) confirm that re-equilibration occurred during a nearly isothermal
(T not in excess of 300 °C) exhumation path.
Received February 22, 2000; revised version accepted July 17, 2000 相似文献
Zusammenfassung. Reequilibrierungstexturen von Flüssigkeitseinschlüssen in exhumierten Hochdruckgesteinen: Ein Beispiel aus dem toskanischen Archipel (Nordthyrrhenisches Meer) Das Auftreten von (Fe-Mg)-Karpholith-führenden Paragensen in Metapeliten auf den Inseln Giglio und Gorgona (toskanischer Archipel, Nordthyrrhenisches Meer) best?tigt die Kontinuit?t einer blauschieferfaziellen Metamorphose vom alpinen Korsika bis in die Toskana. Zahlreiche Flüssigkeitseinschlüsse wurden in Quarz eingeschlossen, der gemeinsam mit (Fe-Mg)-Karpholithfasern in diesen beiden blauschieferfaziellen metamorphen Kernen vorkommt. Die Textur der Einschlüsse (annular, semi-annular, negative Kristallgestalt), die Mikrothermometrie (Konstanz der Werte) und die SEM Untersuchungen (Vorhandensein prim?rer Fe-reicher Fluide) best?tigen, dass die Reequilibrierung entlang eines beinahe isothermen Exhumationspfades (T nicht über 300 °C) erfolgte.
Received February 22, 2000; revised version accepted July 17, 2000 相似文献
70.
Cleber Gonzales de Oliveira Waldir Renato Paradella Arnaldo de Queiroz da Silva 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(1):67-72
The Brazilian Amazon is a vast territory with an enormous need for mapping and monitoring of renewable and non-renewable resources. Due to the adverse environmental condition (rain, cloud, dense vegetation) and difficult access, topographic information is still poor, and when available needs to be updated or re-mapped. In this paper, the feasibility of using Digital Surface Models (DSMs) extracted from TerraSAR-X Stripmap stereo-pair images for detailed topographic mapping was investigated for a mountainous area in the Carajás Mineral Province, located on the easternmost border of the Brazilian Amazon. The quality of the radargrammetric DSMs was evaluated regarding field altimetric measurements. Precise topographic field information acquired from a Global Positioning System (GPS) was used as Ground Control Points (GCPs) for the modeling of the stereoscopic DSMs and as Independent Check Points (ICPs) for the calculation of elevation accuracies. The analysis was performed following two ways: (1) the use of Root Mean Square Error (RMSE) and (2) calculations of systematic error (bias) and precision. The test for significant systematic error was based on the Student’s-t distribution and the test of precision was based on the Chi-squared distribution. The investigation has shown that the accuracy of the TerraSAR-X Stripmap DSMs met the requirements for 1:50,000 map (Class A) as requested by the Brazilian Standard for Cartographic Accuracy. Thus, the use of TerraSAR-X Stripmap images can be considered a promising alternative for detailed topographic mapping in similar environments of the Amazon region, where available topographic information is rare or presents low quality. 相似文献