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1.
Remote observations of the lunar radiowave emission are reexamined in the light of physical property data accumulated through the Apollo program. It is found that thermal and electrical properties determined for a number of different landing sites yield theoretical results in good agreement with remote observations for millimeter and short centimeter wavelengths. Theoretical models incorporating reflecting layers of rock and physical property data from the Apollo program are compared to the longer wavelength (5–500 cm) observational data to estimate a disk average steady state heat flow and a mean depth of the lunar regolith. It is found that a high heat flow, comparable to the heat flows measured at the Apollo 15 and 17 sites, is required to fit the available 5–20 cm wavelength remote data, and that a lunar surface layer relatively free of large boulders within the upper 10–30 m best fits the observations of a decreasing brightness temperature with wavelength for wavelengths greater than ~ 50 cm. 相似文献
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Marcus Schulz Jan Priegnitz Jörg Klasmeier Stefan Heller Stefan Meinecke Michael Feibicke 《水文研究》2012,26(2):272-280
In several empirical and modelling studies on river hydraulics, dispersion was negatively correlated to surface roughness. In this study, it was aimed to investigate the influence of surface roughness on longitudinal dispersion under controlled conditions. In artificial flow channels with a length of 104 m, tracer experiments with variations in channel bed material were performed. By use of measured tracer breakthrough curves, average flow velocity, mean longitudinal dispersion, and mean longitudinal dispersivity were calculated. Longitudinal dispersion coefficients ranged from 0·018 m2 s?1 in channels with smooth bed surface up to 0·209 m2 s?1 in channels with coarse gravel as bed material. Longitudinal dispersion was linearly related to mean flow velocity. Accordingly, longitudinal dispersivities ranged between 0·152 ± 0·017 m in channels with smooth bed surface and 0·584 ± 0·015 m in identical channels with a coarse gravel substrate. Grain size and surface roughness of the channel bed were found to correlate positively to longitudinal dispersion. This finding contradicts several existing relations between surface roughness and dispersion. Future studies should include further variation in surface roughness to derive a better‐founded empirical equation forecasting longitudinal dispersion from surface roughness. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
4.
James Marcus Bishop Weizhong Chen Adel Hasan Alsaffar Hussain Mahmoud Al-Foudari 《Estuaries and Coasts》2011,34(6):1246-1254
Discharge of the Shatt Al-Arab is believed to be a dominating component of the northern Arabian Gulf’s ecology and largely
responsible for productivity of Kuwait’s fisheries. With major construction of dams on the Tigris and Euphrates Rivers in
Turkey, river discharge has been substantially reduced, and flooding essentially eliminated. We attempted to relate river
flow and shrimp landings indirectly by correlating 19 years of salinity and temperature data from Kuwait’s waters with corresponding
annual shrimp landings. For green tiger prawns (Penaeus semisulcatus), the combination of October salinities and January temperatures provided the best correlation (r = 0.67) with landings in the following shrimping season. For the combined landings of jinga and kiddi shrimps (Metapenaeus affinis and Parapenaeopsis stylifera, respectively), December salinity during season and May temperature prior to season resulted in the best correlation (r = 0.87). Landings of these two species also correlated well with spring and summer temperatures. Under normal conditions,
late winter or early spring temperatures prior to fishing season influence recruitment of the green tiger prawn, whereas December
salinities during harvest season influence the abundance of jinga–kiddi shrimps. With further reductions in the Shatt Al-Arab
discharge and the elimination of flood events, Kuwait’s shrimp landings will most likely decrease over time. 相似文献
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Marcus M. Key Jr. Kamil Zágoršek William P. Patterson 《International Journal of Earth Sciences》2013,102(1):305-318
Stable carbon and oxygen isotope values from single bryozoan colonies were used to reconstruct the paleoenvironments of the Early to Middle Miocene (Ottnangian to Badenian) sediments of the Central Paratethys. This approach utilizes a locally abundant allochem while avoiding matrix and multiple allochem contamination from bulk rock samples. Bryozoan colonies (and a few foraminifera and rock matrix samples) from 14 localities yielded 399 carbon and oxygen isotope values. Data from six of the localities (15 % of the total number of samples) were interpreted as having been diagenetically altered and were rejected. The remaining data indicate a primarily localized upwelling signal with lesser variation caused by global climatic and regional tectonic forcing of sea level, salinity, and temperature. Paleotemperatures were calculated to range from 12 to 21 °C. Despite potential taxonomic and diagenetic problems, bryozoan colonies are a powerful, underutilized source of paleoenvironmental carbon and oxygen isotope data. 相似文献
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Marcus Power 《Geoforum》2009,40(1):14-24
One important (though often neglected) part of the ‘development business’ committed to principles of partnership is the Commonwealth, a voluntary association of 54 independent countries, almost all of which were formerly under British rule. This paper focuses on the Commonwealth’s contemporary sense of ‘responsibility’ for shaping African development through ‘partnership’ and by promoting ‘good governance’ and examines the particular example of Mozambique, which joined the Commonwealth in 1995. In exploring exactly what membership of this post-colonial ‘family’ has meant for Mozambique the paper explores the neocolonial paternalism and sense of trusteeship that the Commonwealth has articulated in its often very apolitical vision of African development which seems to lock the continent into a permanent stage of tutelage and to repetitively reduce Africa to a set of core deficiencies for which externally generated ‘solutions’ must be devised. More generally, the paper also examines the wider context of the Commonwealth’s involvement in Africa by looking at the connections it has made to British industry, British charities and the British Department for International Development (DFID). The paper concludes with an assessment of the ‘showcase’ potential of Mozambique and its importance to Commonwealth and DFID narrations of an African ‘success’ story of peace, stability and growth since the end of the country’s devastating civil war in 1992. 相似文献
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Topographic data from the Shuttle Radar Topography Mission (SRTM) captures the permanent deformation of a prominent highstand
of Mono Lake, California USA. Deformation of the Dechambeau Ranch highstand shoreline was measured using the elevation of
the beach berm—shoreline bluff break-in-slope. Point source models and a boundary element dike model were used to approximate
the source of deformation underneath the northern end of the Mono Craters. The point source model could not adequately explain
the observed deformation. The dike model yielded the best results for a NW trending dike dipping 60° NE and inflated to widths
greater than 60 m. The results suggest that the geometry of the source is more complex than a simple vertical dike and that
the deformation is better explained with a dipping dike following a normal fault, or an elongated cryptodome. 相似文献
10.
Reinaldo L. Bozelli Adriano Caliman Rafael D. Guariento Luciana S. Carneiro Jayme M. Santangelo Marcos P. Figueiredo-Barros Joo J.F. Leal Adriana M. Rocha Letícia B. Quesado Paloma M. Lopes Vinicius F. Farjalla Claudio C. Marinho Fabio Roland Francisco A. Esteves 《Limnologica》2009,39(4):306-313
Human activities are exposing freshwater ecosystems to a wide range of stressors, whose direct and indirect effects can be alleviated or exacerbated through interactive effects with dynamic environmental drivers. This study used long-term data from two Neotropical lacustrine freshwater systems (Batata Lake, an Amazonian floodplain lake and Imboassica lagoon, an Atlantic coastal lagoon) subjected to different kinds of environmental fluctuations (i.e., flood pulse and sandbar opening) and anthropogenic impacts (i.e., siltation and eutrophication). Our objective was to determine whether the effects of human perturbations are contingent on modifications of important biotic and abiotic characteristics through environmental variability. For both ecosystems, environmental variability consistently interacted with anthropogenic perturbations to alter most of the variables analyzed, such as nutrient dynamics, chlorophyll-a concentration, zooplankton and benthic invertebrate species richness, and temporal community stability, which indicates that interactive effects between environmental variability and anthropogenic perturbations may impact a myriad of ecosystem properties. Furthermore, the nature of these interactive effects was highly dependent on the variable considered and on the ecosystem analyzed. For example, at Imboassica lagoon, sandbar openings interacted synergistically with trophic state to increase the phosphorus concentration in the water column. At Batata Lake, flooding generally alleviated the negative effects of siltation on species richness by both diluting inorganic suspended material concentration and by promoting local recruitment from the regional species pool. Such results indicate that our ability to understand and predict the outcome of anthropogenic impacts on inland aquatic systems can be hampered if we consider human stressors as “static” phenomena disconnected from dynamic interactions with major local environmental drivers. 相似文献