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61.
One of the main concerns in regional climate modeling is to which extent limited-area regional climate models (RCM) reproduce
the large-scale atmospheric conditions of their driving general circulation model (GCM). In this work we investigate the ability
of a multi-model ensemble of regional climate simulations to reproduce the large-scale weather regimes of the driving conditions.
The ensemble consists of a set of 13 RCMs on a European domain, driven at their lateral boundaries by the ERA40 reanalysis
for the time period 1961–2000. Two sets of experiments have been completed with horizontal resolutions of 50 and 25 km, respectively.
The spectral nudging technique has been applied to one of the models within the ensemble. The RCMs reproduce the weather regimes
behavior in terms of composite pattern, mean frequency of occurrence and persistence reasonably well. The models also simulate
well the long-term trends and the inter-annual variability of the frequency of occurrence. However, there is a non-negligible
spread among the models which is stronger in summer than in winter. This spread is due to two reasons: (1) we are dealing
with different models and (2) each RCM produces an internal variability. As far as the day-to-day weather regime history is
concerned, the ensemble shows large discrepancies. At daily time scale, the model spread has also a seasonal dependence, being
stronger in summer than in winter. Results also show that the spectral nudging technique improves the model performance in
reproducing the large-scale of the driving field. In addition, the impact of increasing the number of grid points has been
addressed by comparing the 25 and 50 km experiments. We show that the horizontal resolution does not affect significantly
the model performance for large-scale circulation. 相似文献
62.
Jean-Pierre Raulin Fernando C.P. Bertoni Pierre Kaufmann Hernan R. Gavilán Emilia Correia Rubens Hadano Nelson J. Schuch 《Journal of Atmospheric and Solar》2011,73(11-12):1581-1586
The South America VLF Network (SAVNET) has been installed in April 2009, and is composed of eight tracking receivers spread over South America, in Brazil, Peru and Argentina, and the Antarctica Peninsula. SAVNET is monitoring the properties of subionospheric propagating waves that reveal changes of the electrical properties of the ionospheric diurnal D-region or nocturnal E-region. In this paper, we will show the ability of the diagnostic obtained by SAVNET to discuss the monitoring of the solar activity on short timescales related to ionization due to solar flares. The sensitivity of flare detection as a function of the solar activity level will be discussed. On longer timescales related to the solar cycle, SAVNET is also able to provide information on the solar Lyman-α radiation. Finally we show that the VLF technique is well suited to search for of seismic-electromagnetic effects, and to provide a genuine diagnostic of high-energy astrophysical phenomena. 相似文献
63.
64.
This study presents the evaluation of simulations from two new Canadian regional climate models (RCMs), CanRCM4 and CRCM5, with a focus on the models’ skill in simulating daily precipitation indices and the Standardized Precipitation Index (SPI). The evaluation was carried out over the past two decades using several sets of gridded observations that partially cover North America. The new Canadian RCMs were also compared with four reanalysis products and six other RCMs. The different configurations of the Canadian RCM simulations also permit evaluation of the impact of different spatial resolutions, atmospheric drivers, and nudging conditions. The results from the new Canadian models show some improvement in precipitation characteristics over the previous Canadian RCM (CRCM4), but these differ with the seasons. For winter, CanRCM4 and CRCM5 have better skill than most other models over all of North America. For the summer, CRCM5 0.44° performs best over the United States, while CRCM4 has the best skill over Canada. Good skill is exhibited by CanRCM4 and CRCM4 in simulating the 6-month SPI over the Prairies and the western US Corn Belt. In general, differences are small between runs with or without large-scale spectral nudging; differences are small when different boundary conditions are used. 相似文献
65.
The middle Silurian ‘big crisis’ refers to a graptolite extinction event and faunal turnover at the onset of a double‐peaked positive carbon isotope excursion. The crisis has been proposed to affect conodonts, giving rise to a sophisticated palaeoecological model of their stepwise extinction, known as the Mulde Event. However, the impact of the event on conodont faunas outside Gotland and the Silurian Baltic Basin remains unknown. Here, it is examined in the Widowo IG‐1 core (E Poland). The middle Silurian succession in this core represents foreshoal, shoal, and lagoonal settings on a tropical carbonate ramp on the shelf of the Eastern European Craton. Three positive δ13Ccarb excursions have been identified; the two upper excursions correlate with the Mulde isotope anomaly and with two global eustatic regressions. Conodont species proposed to be affected by the extinction event either were not observed or ranged through the extinction interval. Changes in their frequencies are best explained by the sequence stratigraphic architecture of the late Wenlock strata in the Widowo IG‐1 core. The little impact of the ‘big crisis’ may reflect facies homogeneity across the studied interval, supporting the hypothesis that the late Wenlock conodont turnover in epicontinental settings was primarily driven by eustatically controlled facies shifts. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
66.
This work focuses on developing multidisciplinary research on weathering profiles of granitoid rocks related to the tectonic and landscape evolution of the Capo Vaticano area, Calabria, southern Italy. During the Pleistocene, the Mediterranean climate plays, on the already decomposed plutonic rocks, important processes of alteration, on both the highest and inland areas and the coastal areas of the Calabrian region, such as the studied area. Field observations coupled to chemical, minero‐petrographical features and geochemical modelling are used to characterize the weathering processes affecting the granitoid complex. The granitoid cut slopes show a generally simple weathering profile characterized by a progressive increase in weathering towards the top of the slopes. The completely weathered rocks (class V) and residual soil (class VI) contain a high percentage of altered minerals, microfractures, and voids. The main mineralogical changes are the partial transformation of biotite and the partial destruction of feldspars (mainly plagioclase) that are associated with the neoformation of secondary clay minerals and ferruginous products during the most advanced stage of weathering. These transformations produce a substitution of the original rock fabric. Geochemical modelling showing the precipitation of kaolinite, illite, vermiculite, ferrihydrite and calcite. These secondary solid phases are similar to those found in this natural system. Thus, the final results of the weathering process is a soil‐like material mainly characterized by mostly a sand to gravel grain‐size fractions related to microfabric changes and mineralogical and chemical variations. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
67.
Manzini Carlo Filippo Ottonelli Daria Degli Abbati Stefania Marano Corrado Cordasco Emilia Angela 《Bulletin of Earthquake Engineering》2022,20(4):2045-2084
Bulletin of Earthquake Engineering - The paper presents the comparison of the results of non-linear static analyses performed with different software based on the equivalent frame (EF) modelling... 相似文献
68.
69.
Marc Macias Laia Andreu Oriol Bosch J. Julio Camarero Emilia Gutiérrez 《Climatic change》2006,79(3-4):289-313
Tree populations located at the geographical distribution limit of the species may provide valuable information about the
response of tree growth to climate warming across climatic gradients. Dendroclimatic information was extracted from a network
of 10 silver-fir (Abies alba) populations in the south-western distribution limit of the species (Pyrenees, NE Iberian Peninsula). Ring-width chronologies
were built for five stands sampled in mesic sites from the Main Range in the Pyrenees, and for five forests located in the
southern Peripheral Ranges where summer drought is more pronounced. The radial growth of silver-fir in this region is constrained
by water stress during the summer previous to growth, as suggested by the negative relationship with previous September temperature
and, to a lesser degree, by a positive relationship with previous end of summer precipitation. Climatic data showed a warming
trend since the 1970s across the Pyrenees, with more severe summer droughts. The recent warming changed the climate-growth
relationships, causing higher growth synchrony among sites, and a higher year-to-year growth variation, especially in the
southernmost forests. Moving-interval response functions suggested an increasing water-stress effect on radial growth during
the last half of the 20th century. The growth period under water stress has extended from summer up to early autumn. Forests
located in the southern Peripheral Ranges experienced a more intense water stress, as seen in a shift of their response to
precipitation and temperature. The Main-Range sites mainly showed a response to warming. The intensification of water-stress
during the late 20th century might affect the future growth performance of the highly-fragmented A. alba populations in the southwestern distribution limit of the species. 相似文献
70.
Geophysical and geological studies of an Ethiopian maar, Haro Maja, demonstrate that its eruptive history is more complex than surface geology alone suggests. The crater is 750 m by 1000 m in diameter and varies in depth from 70 m to 110 m. A strong magnetic anomaly is caused by a central basaltic mound, but a broader crater-wide anomaly is best modelled by a 50 m thick frozen lava lake, 30 m below the crater floor. The central mound was not erupted directly onto the lava lake, but was extruded onto top of the sedimentary infill after a quiescent depositional interval. Electrical resistivity measurements further indicate that other basaltic intrusions failed to reach the surface during that eruptive period. 相似文献