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171.
Heiles (1984) has identified a large angular diameter (30°), anomalous velocity H I structure in the anti-center region of the Galaxy. The distance to this structure is the key to understanding of the energetics and, hence, the origin. Distance estimates based on indirect arguments have ranged from less than 100 pc to a few kiloparsecs. We report the absence of any anomalous velocity Ca K absorption features in high sensitivity echelle spectra towards 17 stars located within the boundaries of this structure. We conclude that the structure is definitely beyond 500 pc and barring unusually low Ca II abundance is more distant than 2.5 kpc. This results supports the hypothesis that the anti-center structure is the result of collision of high-velocity clouds with the galactic H I disk.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. 相似文献
172.
Mathieu Duttine Gérard Villeneuve Françoise Bechtel Gérard Demazeau 《Comptes Rendus Geoscience》2002,334(13):949-955
Natural quartz crystals coming from Madagascar, Angola, Brazil, and Spain were studied by EPR after β irradiation in order to characterise the paramagnetic centres due to impurities, and examine in which way their relative proportion could constitute a useful criterion for origin researches. In all our samples, EPR experiments revealed germanium centres [GeO4/M+]° with M = Li or Na, aluminium ones [AlO4/h]° and two titanium centres ([TiO4/H+]° and [TiO4/M+]°) also appeared, except for samples coming from Spain. The comparison of the relative concentrations of paramagnetic species led us on to draw diagrams that allowed distinguishing the origins of the studied samples using only EPR spectra. To cite this article: M. Duttine et al., C. R. Geoscience 334 (2002) 949–955. 相似文献
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Records from South America show that modern ENSO (El Nino-Southern Oscillation) did not exist 7000 cal yr B.P. and has developed progressively since then. There has been little information available on oceanic conditions in the eastern equatorial Pacific (EEP) to constrain explanations for ENSO onset. We report quantitative observations on thermocline and mixed-layer conditions in the EEP during ENSO start up. We found important changes in both the thermocline and the mixed layer, indicating increased upwelling of cooler waters since 7000 cal yr B.P. This resulted from change in the source and/or properties of waters supplying the Equatorial Undercurrent, which feeds upwelling along the equator and the Peru margin. Modeling shows that ENSO is sensitive to subsurface conditions in the eastern equatorial Pacific and that the changes in the thermocline we observed were driven by extratropical processes, giving these a role in conditioning the development of ENSO. This is in contrast to models that call for control of equatorial Pacific oceanography by tropical processes only. These infer stronger upwelling and cooler surface waters for the EEP during the mid-Holocene, which is not supported by our results. 相似文献
177.
The structure of the upper ocean and surface atmospheric conditions are described during a ship cruise across the central Indian Ocean from December 1995 to January 1996. In situ data on currents, temperature, salinity and surface heat fluxes are described and compared with expected climatological values. Thermocline uplift in the 6-7°S latitude band is linked to the cyclonic shear of near-surface currents. A comparison of quiescent and windy periods demonstrates that evaporative fluxes become amplified near cyclonic vortices fed by southerly meridional winds. The ocean density structure is influenced by salinity gradients, driven by the precipitation-evaporation balance. Near the inter-tropical convergence zone (ITCZ), freshwater fluxes create a stable surface layer and helps to maintain the eastward equatorial counter-current. An analysis of the atmospheric boundary layer from NCEP re-analysis data seeks to place the in situ results into the context of weather conditions at the time of the cruise. Further studies of this kind will improve our understanding of relationships between the Indian Ocean monsoon and surrounding climates. 相似文献
178.
Franois Anctil Renaud Mathieu Lon-tienne Parent Alain A. Viau Mathali Sbih Masoud Hessami 《Journal of Hydrology》2002,260(1-4):30-37
The aim of this study was to characterise fine scale patterns of organic soil moisture content in the top 5 cm by means of semi-variogram modelling. Soil moisture content was observed along a transect on 2 occasions, early in the 1999 growing season to avoid any influences originating from vegetation and cultural practices. Soil moisture values were found to be normally distributed and were not significantly correlated with the soil organic matter content. Many similarities were depicted between the exponential semi-variograms characteristics of this study and another one in mineral soils, reported in the literature, except for the much higher sills associated with organic soils. Of particular interest were similar correlation lengths, indicating that a correlation range of the order of 100 m should be expected for mineral soils and for the level of moisture and organic matter contents found in this study. 相似文献
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