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51.
52.
Maria V. Triantaphyllou Assimina Antonarakou Margarita Dimiza Christos Anagnostou 《Geo-Marine Letters》2010,30(1):1-13
In core ADE3-23 collected in the Libyan Sea, the nannofossil species Coccolithus pelagicus, Coronosphaera spp., Helicosphaera spp., Syracosphaera spp., Calcidiscus spp., small Gephyrocapsa spp., and the planktonic foraminifers Globigerina bulloides, Neogloboquadrina pachyderma, Globorotalia scitula, Turborotalita quinqueloba and Neogloboquadrina dutertrei prevail in sapropel S6 (midpoint at 172 ka b.p.), indicative of cold and highly productive surface conditions. Warm and highly stratified water-column conditions are recorded
by the characteristic assemblage of Globigerinoides ruber, Globoturborotalita rubescens, Florisphaera profunda, Rhabdosphaera spp. during the sapropel S5 depositional interval (midpoint at 124 ka b.p.). Compared with S5, Globigerinita glutinata, Globorotalia inflata, Globigerinella siphonifera, Globorotalia truncatulinoides and the calcareous nannofossil Emiliania huxleyi characterise less stratified conditions within sapropel S1 (midpoint at 8.5 ka b.p.). Multivariate statistical analyses of calcareous nannofossil and planktonic foraminifers in core ADE3-23 identify planktonic
assemblages which typify sapropels S6, S5 and S1 in the Libyan Sea. A warmer interval is recognised in the middle part of
the cold S6, and can be associated with an influx of less saline waters and the occurrence of a faint, temporary deep chlorophyll
maximum. Evidence for enhanced surface productivity and breakdown of stratification is observed in the middle–upper part of
the warm S5, associated with climatic deterioration. Moreover, an increase in surface productivity in the upper S1 implies
weak stratification. Our combined calcareous nannofossil and planktonic foraminiferal data add to the evidence that climate
variability was more pronounced than commonly considered to date for all the three studied Eastern Mediterranean sapropel
depositional intervals. 相似文献
53.
Preliminary flood risk assessment: the case of Athens 总被引:3,自引:2,他引:1
Flood mapping, especially in urban areas, is a demanding task requiring substantial (and usually unavailable) data. However,
with the recent introduction of the EU Floods Directive (2007/60/EC), the need for reliable, but cost effective, risk mapping
at the regional scale is rising in the policy agenda. Methods are therefore required to allow for efficiently undertaking
what the Directive terms “preliminary flood risk assessment,” in other words a screening of areas that could potentially be
at risk of flooding and that consequently merit more detailed attention and analysis. Such methods cannot rely on modeling,
as this would require more data and effort that is reasonable for this high-level, screening phase. This is especially true
in urban areas, where modeling requires knowledge of the detailed urban terrain, the drainage networks, and their interactions.
A GIS-based multicriteria flood risk assessment methodology was therefore developed and applied for the mapping of flood risk
in urban areas. This approach quantifies the spatial distribution of flood risk and is able to deal with uncertainties in
criteria values and to examine their influence on the overall flood risk assessment. It can further assess the spatially variable
reliability of the resulting maps on the basis of the choice of method used to develop the maps. The approach is applied to
the Greater Athens area and validated for its central and most urban part. A GIS database of economic, social, and environmental
criteria contributing to flood risk was created. Three different multicriteria decision rules (Analytical Hierarchy Process,
Weighted Linear Combination and Ordered Weighting Averaging) were applied, to produce the overall flood risk map of the area.
To implement this methodology, the IDRISI Andes GIS software was customized and used. It is concluded that the results of
the analysis are a reasonable representation of actual flood risk, on the basis of their comparison with historical flood
events. 相似文献
54.
Christos Kanellopoulos 《Central European Journal of Geosciences》2012,4(4):545-560
In the northwestern part of Euboea Island and the neighbouring part of the mainland in eastern central Greece, many hot springs exist. We collected and analysed the newly formed material around the hot springs. The samples were studied at the lab with X-Ray Diffraction, Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). In all cases the studied materials were thermogenic travertine presenting many different lithotypes. The studied travertine deposits consist mainly of aragonite and calcite, but in some cases, as the main mineral phase, an amorphous hydrous ferric oxyhydroxide, probably ferrihydrite (creating a laminated iron-rich travertine deposit), was identified. The lithotypes that were identified were of great variety (spicular, shrubs, etc). Some of them (pisoliths, rafts and foam rock types) are quite rare and one of them (framework type) is described for the first time. Morphological data and field observations suggest possible inorganic and organic controls on carbonate precipitation. Similar lithotypes have been recorded at Mammoth hot springs, Yellowstone National Park in USA and at Rapolano Terme, Italy. 相似文献
55.
Assessment of the sensitivity of the southern coast of the Gulf of Corinth (Peloponnese, Greece) to sea-level rise 总被引:1,自引:0,他引:1
Efthimios Karymbalis Christos Chalkias George Chalkias Eleni Grigoropoulou George Manthos Maria Ferentinou 《Central European Journal of Geosciences》2012,4(4):561-577
The eustatic sea-level rise due to global warming is predicted to reach approximately 18?C59 cm by the year 2100, which necessitates the identification and protection of sensitive sections of coastline. In this study, the classification of the southern coast of the Gulf of Corinth according to the sensitivity to the anticipated future sealevel rise is attempted by applying the Coastal Sensitivity Index (CSI), with variable ranges specifically modified for the coastal environment of Greece, utilizing GIS technology. The studied coastline has a length of 148 km and is oriented along the WNW-ESE direction. CSI calculation involves the relation of the following physical variables, associated with the sensitivity to long-term sea-level rise, in a quantifiable manner: geomorphology, coastal slope, relative sea-level rise rate, shoreline erosion or accretion rate, mean tidal range and mean wave height. For each variable, a relative risk value is assigned according to the potential magnitude of its contribution to physical changes on the coast as the sea-level rises. Every section of the coastline is assigned a risk ranking based on each variable, and the CSI is calculated as the square root of the product of the ranked variables divided by the total number of variables. Subsequently, a CSI map is produced for the studied coastline. This map showed that an extensive length of the coast (57.0 km, corresponding to 38.7% of the entire coastline) is characterized as highly and very highly sensitive primarily due to the low topography, the presence of erosionsusceptible geological formations and landforms and fast relative sea-level rise rates. Areas of high and very high CSI values host socio-economically important land uses and activities. 相似文献
56.
In order to determine the properties of lean Roller compacted concrete mixture of Filiatrinos Dam, a number of trial mixtures were prepared and a trial section was constructed. The results of the above tests were supplemented with laboratory measurements and in situ tests that were performed during the quality control of the dam construction. Additionally, results of trial mixtures using flysch excavation material from the dam area and limestone aggregates with clay lumps from a nearby quarry were used. This paper examines the impact of the quality of aggregates and the cementitious materials’ content on compressive strength and also the influence of other factors, such as the percentage of compaction. Certain mathematical relations are suggested that can be used in the design phase of hardfill Dams as well as in the quality control during construction. Moreover, the influence of the cement content on the compressive strength and the percentage of the replacement of cement with flying ash are studied. 相似文献
57.
Christos G. Karydas Ioannis L. Sarakiotis George C. Zalidis 《Earth Science Informatics》2014,7(1):47-58
In the streams of the Mediterranean island of Crete (Greece), olive mill wastewater (OMW) has been reported to reduce biodiversity up to 85 %. Mere conduction of impact assessment based on pollutant concentrations, however, cannot reveal how impacted areas may be connected to the pollution sources. In this study, we developed a new methodology which allows for a dynamic cause-effect linking of pollution sources and impacted areas through the pathways of OMW. Risk is hierarchically assessed and mapped at three different scales and more specifically, at the source scale (targeting olive mill units and their waste tanks), at the receptor scale (targeting potential impacted sites in the streams) and at the watershed scale (which is the scale of overall water management). The approach is based mainly on remote sensing data without taking account of groundwater regimes or field measurements. Involvement of local experts for recognizing spatial features of interest and selecting appropriate risk parameters was proved necessary and efficient in order to model the stream pollution risk realistically. Potential impacted sites in the stream network were occasionally verified by a field survey. The results comprise a set of risk maps at the three different scales. The constructed digital geo-database can be updated or modified and thus is considered to be a dynamic tool for future environmental management in the service of the local community. 相似文献
58.
Helen Mavromichalaki George Souvatzoglou Christos Sarlanis George Mariatos Athanasios Papaioannou Anatoly Belov Eugenia Eroshenko Victor Yanke 《New Astronomy》2010,15(8):744-748
The European Commission is supporting the real-time database for high-resolution neutron monitor measurements (NMDB) as an e-Infrastructures project in the Seventh Framework Programme in the Capacities section. The realization of the NMDB will provide the opportunity for several applications most of which will be implemented in real-time. An important application will be the establishment of an Alert signal when dangerous solar particle events are heading to the Earth, resulting into a ground level enhancement (GLE) registered by neutron monitors (NMs). The cosmic ray community has been occupied with the question of establishing such an Alert for many years and recently several groups succeeded in creating a proper algorithm capable of detecting space weather threats in an off-line mode. A lot of original work has been done to this direction and every group working in this field performed routine runs for all GLE cases, resulting into statistical analyses of GLE events. The next step was to make this algorithm as accurate as possible and most importantly, working in real-time. This was achieved when, during the last GLE observed so far, a real-time GLE Alert signal was produced. In this work, the steps of this procedure as well as the functionality of this algorithm for both the scientific community and users are being discussed. Nevertheless, the transition of the Alert algorithm to the NMDB is also being discussed. 相似文献
59.
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