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1.
COEN J. RITSEMA JANNES STOLTE KLAAS OOSTINDIE ERIK VAN DEN ELSEN PAUL M. VAN DIJK 《水文研究》1996,10(8):1081-1089
Surface runoff may be generated when the rainfall intensity exceeds the infiltration capacity, or when the soil profile is saturated with water. Indications exist that both types of overland flow may occur in hilly agricultural loess regions. Here, for a loessial hillslope under maize in the southern part of The Netherlands, it was shown, with pressure head and runoff measurements, that Hortonian overland flow occurs during typical summer rain events. Surface runoff was initiated after saturation of the top 5–10 cm of the soil. Deeper in the soil, unsaturated conditions prevailed while runoff took place. Peak runoff discharges at the outlet of the subcatchment occurred a few minutes after peak rainfall intensities were measured. It appeared that SWMS_2D, a two-dimensional water flow model, was capable in simulating observed pressure head changes and runoff. Simulated potential runoff for the transect studied was higher by a magnitude of three than the measured areal average. This indicates effects of surface ponding, and the probable location of this particular transect in a region with high runoff production. 相似文献
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The oribatid mite Maudheimia wilsoni Dalenius was found to be numerous on the underside of stones at Jutulsessen (72°S, 3'E) in Dronning Maud Land, Antarctica. Daily temperature fluctuations of the microhabitat from as high as 19°C and to as low as – 17°C were observed during the austral summer. Optimal activity of the mites occurred at 10°C. Even in January the mean supercooling point of adult mites was as low as -30.8±4.7°C. Haemolymph osmolality ranged from 500 to 800mOsmol and thermal hystersis freezing points from −4.7 to −6.1°C. Adult mites had a mean water content of 43.6% and a water loss rate of 0.12 μgh−1 at 15°C and 10% relative humidity. 相似文献
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ERIK LAGERLUND 《Boreas: An International Journal of Quaternary Research》1977,6(2):159-166
A mosaic distribution of Pre-Quatcrnary rocks in Skåne constitutes good conditions for using gravel analysis in till-stratigraphical work. Recently discovered neotcctonic movements and their effect on the composition, distribution, and correlation of tills are discussed. With examples from the Kullen arm, it is shown that compositional variability in a till bed, as cvidenl from gt-avel analysis, can be deciphered and is of great stratigraphical value. 相似文献
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Eemian and Weichselian stratigraphy in South Sweden 总被引:1,自引:0,他引:1
BJÖRN E. BERGLUND ERIK LAGERLUND 《Boreas: An International Journal of Quaternary Research》1981,10(4):323-362.
The stratigraphy of Pleistocene sequences within three main areas of the province of Skane, South Sweden, is discussed. The traditional stratigraphy is revised. New lithostratigraphic units are deficned and named according to international stratigraphic terminology. Lithostratigraphical correaltions are based on sedimentological development and palaeoenvironmental changes. Organic beds are correlated with the Eemain interglacial and some of the Early and Middle Weichselian interstadials. The chronostratigraphic key site, Stenberget, is described in greater detail. Stratrigraphy and palaeoenvironment are summarized in a scheme indicating that South Sweden was glaciated only during the period 21,000–13,000 B.P. 相似文献
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The amphipod Gammarus oceanicus can survive being frozen into solid sea ice at a temperature of –6 to 7C- The animals appear to be supercooled at this temperature. No thermal hysteresis agents were present the haemolymph, and the prevention of internal freezing in the animals thus requires a body surface with a low Permeability to water and ice. Gammarus oceanicus is a euryhaline species. Below 700 mOsm seawater, it displays a very efficient osmoregulation, whereas it is an osmoconformer at seawater osmolalities above this value. At +5°C the amphipods die whenever their body fluid osmolality exceeds about 1000 mOsm. When the animals are trapped in freezing seawater, the osmolality of the brine may exceed this value considerably. The tolerance of the animals to hyperosmotic stress thus seems to be higher at subzero temperatures than at +5°C. 相似文献
8.
Ice algae in the Barents Sea: types of assemblages, origin, fate and role in the ice-edge phytoplankton bloom 总被引:4,自引:0,他引:4
ERIK E. SYVERTSEN 《Polar research》1991,10(1):277-288
Ice algal accumulations were recognised by their vertical distribution in the ice, as surface, interior and bottom assemblages. The latter were quantitatively the most important in the Barents Sea and in particular the sub-ice assemblage floating towards, or attached to, the undcr-surface of the sea ice. Colonisation of the ice takes place by a "sieving" of the water between closely spaced platelets on the ice under-surface. Once associated with the ice, the assemblage undergoes a succession terminated by the dominance of ice specialists. In a horizontal S-N section through the ice, three distinct zones may be recognised: at the ice edge the recently colonised ice has a layer of algae up to a few millimeters in thickness consisting primarily of planktonic species. Further into older first year ice the algal layer becomes thicker and is typically dominated by the pennate diatom Nilzschia frigida Grunow. Below multi-year ice in the central polar basin decimetre-thick mats of algae are found, consisting almost exclusively of the centric diatom Melosira arclica (Ehrenberg) Dickie and a few associated, mostly epiphytic, species. The predominantly planktonic sub-ice assemblages at the ice edge can grow under stable conditions as soon as the light becomes adequate in the spring, and they are able to multiply actively for one to two months before planktonic growth is possible. The sub-ice plankton assemblage thus forms an inoculum released to the stabilising water when the ice starts melting. This may explain how a phytoplankton bloom can develop explosively at the ice edge as soon as the ice melting commences, at a time when the number of algal cells in the water column is still very low. 相似文献
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