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51.
Suspended sediments in the Kharaa River catchment (Mongolia) and its impact on hyporheic zone functions 总被引:2,自引:2,他引:0
Melanie Hartwig Philipp Theuring Michael Rode Dietrich Borchardt 《Environmental Earth Sciences》2012,65(5):1535-1546
A previous study investigating the ecological status of the Kharaa River in Northern Mongolia reported fine-grained sediments
as being a major stress factor causing adverse impacts on the benthic ecology. However, the source of these sediments within
the catchment as well as the specific impact on hyporheic zone functions in the Kharaa River remained unclear. Therefore,
the objective of the current study was to investigate the underlying source–receptor system and implement an integrated monitoring
approach. Suspended sediment sources within the Kharaa catchment were identified by using extensive spatially distributed
sediment sampling and geochemical and isotope fingerprinting methods. On the receptor side, the ecological implications across
a gradient of fine-grained sediment influx were analyzed using a distinct hyporheic zone monitoring scheme at three representative
river reaches along the Kharaa River. Results of suspended sediment source monitoring show that during snowmelt runoff, riverbank
and gully erosion were the dominant sources. During the summer period, upland erosion contributed a substantial share of suspended
sediment. Fine-grained sediment influx proved to be the cause of habitat loss in the hyporheic zone and benthic oxygen production
limitation. This combined catchment and in-stream monitoring approach will allow for a better understanding and spatially
explicit analysis of the interactions of suspended sediment transport and hyporheic zone functioning. This information has
built the basis for a coupled modeling framework that will help to develop efficient management measures within the Kharaa
River basin with special emphasis on rapidly changing land-use and climatic conditions. 相似文献
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53.
ABSTRACTPhoto-sharing services provide a rich resource of crowdsourced spatial data consisting of georeferenced imagery and metadata. Shared photos can provide valuable information for a variety of applications and geospatial analysis tasks, such as identifying tourist hot spots or traveled routes. Understanding the spatiotemporal patterns of photo contributions will allow analysts to assess the suitability of these data for related analysis tasks. Using California as a study area, this paper analyzes various aspects of photo contribution patterns of Panoramio and Flickr. It identifies areas where annual photo contributions are still growing and areas that undergo a decline in annual contributions. Multiple regression is used to identify which environmental correlates are associated with an increase in photo-sharing activities. Furthermore, panel data of annual contributions between 2006 and 2013 for California subcounties will be used in a regression model to demonstrate that there is a positive feedback effect between Panoramio and Flickr photo contributions, but no neighborhood effect. The results of this paper provide insight into the data quality of crowdsourced image collections. These collections are commonly used for geospatial applications, including tourist information services and the computation of scenic routes. 相似文献
54.
Hartwig E. Frimmel 《Chemical Geology》2009,258(3-4):338-353
A first study of REE + Y distribution in a variety of Neoproterozoic (Cryogenian and Ediacaran) carbonates from different settings in the Saldania, Gariep, Damara and West Congo Belts in southwestern and central Africa revealed systematic differences that can be explained by varying palaeoenvironmental factors. The majority of samples display relatively unfractionated, flat shale-normalised REE + Y patterns that cannot be ascribed solely to shale contamination but are interpreted as resulting from the incorporation of near-shore colloids, possibly related to Fe-oxihydroxide scavenging. Only few carbonate units yielded trace element distributions that conform to a typical seawater composition. Those carbonates that were affected by stratiform, syn-sedimentary hydrothermal mineralisation are distinguished by Eu anomalies. Considering the similarity in residence time between REE and carbon, the strong influence of river-born particles on the REE + Y distribution in the analysed carbonates casts considerable doubt over the usefulness of these carbonates for stratigraphic correlation of Neoproterozoic sediment successions based on carbon isotopes. 相似文献
55.
56.
Michael Owor Tina Hartwig Andrew Muwanga Dieter Zachmann Walter Pohl 《Environmental Geology》2007,51(6):1065-1075
The abandoned Kilembe copper mine in western Uganda is a source of contaminants, mobilised from mine tailings into R. Rukoki
flowing through a belt of wetlands into Lake George. Water and sediments were investigated on the lakeshore and the lakebed.
Metal associations in the sediments reflect the Kilembe sulphide mineralisation. Enrichment of metals was compared between
lakebed sediments, both for wet and dry seasons. Total C in a lakebed core shows a general increment, while Cu and Co decrease
with depth. The contaminants are predominant (> 65%) in the ≤ 63 μm sediment size range with elevated Cu and Zn (> 28%), while
Ni, Pb and Co are low (< 18%) in all the fractions. Sequential extraction of Fe for lakeshore sediment samples reveals low
Fe mobility. Relatively higher mobility and biological availability is seen for Co, Cu and S. Heavy metal contents in lake
waters are not an immediate risk to the aquatic environment. 相似文献