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排序方式: 共有161条查询结果,搜索用时 171 毫秒
41.
C.B. Lopes A.I. Lilleb P. Pato J.M. Dias S.M. Rodrigues E. Pereira A.C. Duarte 《Estuarine, Coastal and Shelf Science》2008,79(4):751-757
Land/ocean boundaries constitute complex systems with active physical and biogeochemical processes that affect the global carbon cycle. An example of such a system is the mesotidal lagoon named Ria de Aveiro (Portugal, 40°38′N, 08°45′W), which is connected to the Atlantic Ocean by a single channel, 350 m wide. The objective of this study was to estimate the seasonal and inter-tidal variability of organic carbon fluxes between the coastal lagoon and the Ocean, and to assess the contribution of the organic carbon fractions (i.e. dissolved organic carbon (DOC) and particulate organic carbon (POC)) to the export of organic carbon to the Ria de Aveiro plume zone. The organic carbon fractions fluxes were estimated as the product of the appropriate fractional organic carbon concentrations and the water fluxes calculated by a two-dimensional vertically integrated hydrodynamic model (2DH). Results showed that the higher exchanges of DOC and POC fractions at the system cross-section occurred during spring tides but only resulted in a net export of organic carbon in winter, totalling 85 t per tidal cycle. Derived from the winter and summer campaigns, the annual carbon mass balance estimated corresponded to a net export of organic carbon (7957 = 6585 t yr−1 POC + 1372 t yr−1 DOC). On the basis of the spring tidal drainage area, it corresponds to an annual flux of 79 g m−2 of POC and 17 g m−2 of DOC out of the estuary. 相似文献
42.
M. A. Baptista J. M. Miranda Fernando C. Lopes Joaquim F. Luis 《Journal of Seismology》2007,11(4):371-380
The 27 December 1722 Algarve earthquake destroyed a large area in southern Portugal generating a local tsunami that inundated
the shallow areas of Tavira. It is unclear whether its source was located onshore or offshore and, in any case, what was the
tectonic source responsible for the event. We analyze available historical information concerning macroseismicity and the
tsunami to discuss the most probable location of the source. We also review available seismotectonic knowledge of the offshore
region close to the probable epicenter, selecting a set of four candidate sources. We simulate tsunamis produced by these
candidate sources assuming that the sea bottom displacement is caused by a compressive dislocation over a rectangular fault,
as given by the half-space homogeneous elastic approach, and we use numerical modeling to study wave propagation and run-up.
We conclude that the 27 December 1722 Tavira earthquake and tsunami was probably generated offshore, close to 37°01′N, 7°49′W. 相似文献
43.
Jaime A. Santos Pedro Chitas Isabel Lopes Carlos Sousa Oliveira Isabel Moitinho de Almeida João Carlos Nunes 《Soil Dynamics and Earthquake Engineering》2011
The Azores archipelago is located at the North America, Eurasia and Africa triple junction and shows seismicity and volcanism typical of an active plate boundary. Terceira Island has been affected by several damaging earthquakes being the 1980 January 1st event (M=7.2) the strongest in Azores during the last century. 相似文献
44.
David Lopes de Castro Nilo Costa Pedrosa Jr.Fernando Acácio Monteiro Santos 《Journal of Applied Geophysics》2011,75(3):431-443
A joint inversion of gravity and geoelectrical data has been performed along a 100 km long profile across the oil-bearing Potiguar rift basin in NE Brazil. The integrated approach is based on the connection between density and resistivity of a sedimentary sequence through the porosity. Seventy-one gravity stations and twenty-nine vertical electrical soundings were carried out across the central part of the Early Cretaceous basin in the Precambrian Borborema Province to apply the proposed joint inversion. Both the physical properties and geometry of the multilayer deep model were well constrained by a wide set of prior information obtained by surface mapping, geophysical logs and seismic sections. The results reveal a rift architecture formed by a 5000 m thick half-graben structure separated by an intervening basement high and an extensive adjacent platform with a sedimentary infill of about 300 m thick. The calculated model shows geometries for the sedimentary density/resistivity interfaces in agreement with the seismostratigraphic sequences revealed by seismic section, representing a substantial improvement in comparison with previously published gravity models. 相似文献
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In this paper, the behaviour of a real geogrids reinforced embankment will be analysed based on the results of numeric modelling
in seismic conditions. The reinforced slope is analysed using commercial software based on the finite differences method.
After the program presentation, is described the methodology of analysis. In modelling, will be devoted special relevance
to the behaviour of the structures in terms of deformations, using comparative analyses with different damping ratio values
for soils and for reinforcements. Finally, will be drawn some conclusions concerning the behaviour of reinforced structures
and in particular, the role of the structural reinforcement’s damping. 相似文献
47.
Marta Lobo Lopes Patrícia Martins Fernando Ricardo Ana Maria Rodrigues Victor Quintino 《Estuarine, Coastal and Shelf Science》2011,92(4):497-580
The decomposition rates of Phragmites australis and Fucus vesiculosus were experimentally determined in an estuarine system using the leaf-bag technique. The study was conducted in fifteen sites arranged in five areas, extending from freshwater, outside the tidal range, to the marine environment, near the mouth of the estuary. The leaf-bags (5 mm mesh), were set up with 3.0 g of dried substrate, submerged in the experimental sites at day 0 and collected at days 3, 7, 15, 30 and 60, to follow biomass loss. The biomass loss through the leaching phase (day 3) was about 16% for Phragmites australis and 33% for Fucus vesiculosus and was independent of salinity for both substrates. The difference in the remaining biomass between the two species increased with time and the decomposition rates differed along the salinity gradient. For F. vesiculosus, the decomposition rate was highest near the mouth of the estuary, corresponding to the preferential distribution area of the algae, and decreased towards freshwater. For Phragmites australis, the fastest decay was observed in the mid estuary, where Phragmites australis occurs naturally, confirming previous studies. The decomposition rates measured at different time intervals (0–15, 0–30 and 0–60 days) were always higher for the algae and decreased with time for both species. These results indicate that the use of decomposition rates as a measure of ecosystem integrity or quality status in transitional waters will not be straightforward and must take into account, among others, the test species, the study area positioning along the estuarine gradient, and the time interval for the calculation of the decomposition rate. 相似文献
48.
Sin Chan Chou Andr de Arruda Lyra Jorge Lus Gomes Daniel Andrs Rodriguez Minella Alves Martins Nicole Costa Resende Priscila da Silva Tavares Claudine Pereira Dereczynski Isabel Lopes Pilotto Alessandro Marques Martins Lus Felipe Alves de Carvalho Jos Luiz Lima Onofre Idalcio Major Manuel Penhor Adrito Santana 《Climate Dynamics》2020,54(9):4021-4042
Sao Tome and Principe is a small insular African country extremely vulnerable to rising sea levels and impacts such as inundation, shore line change, and salt water intrusion into underground aquifers. Projections of climate change have considered coarse model resolutions. The objective of this work is to dynamically downscale the global model projections to 4-km resolution and to assess the climate change in the Sao Tome and Principe islands. The global climate projections are provided by the Canadian Earth System Model under two Representative Concentration Pathways greenhouse gas scenarios, RCP4.5 and RCP8.5. The downscaling is produced by the Eta regional climate model. The baseline period is taken between 1971 and 2000, and the future climate period is taken between 2041 and 2070. The 2-m temperature simulations show good agreement with station data. The model simulates temperature more accurately than precipitation. The precipitation simulations systematically show underestimation and delay of the rainy and the dry seasons by about 1 month, a feature inherited from the global climate model. In the middle of the 21st century, projections show the strongest warming in the elevated parts of the Sao Tome Island, especially in February under RCP8.5. Warmer nights and warmer days become more frequent in the islands when compared with those in the present. While under RCP4.5, precipitation increases in the islands; under RCP8.5, it decreases everywhere in both islands. Heavy precipitation rates should increase, especially in the south-southwestern parts of the Sao Tome islands. Detailed spatial variability of the temperature and precipitation changes in the islands can only be revealed at very high spatial model resolution. Implications for the potential energy production from two major river basins are assessed in this work. 相似文献
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