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81.
82.
A new process-based approach is introduced for a more efficient computation of the overflow-induced growth of an erosional channel in a non-cohesive homogeneous narrow landmass such as the breach growth in a sand-dike. The approach is easy to incorporate in a 1D/2DV morphodynamic model to compute the channel growth both vertically and laterally. 相似文献
83.
Dr. Andreas Henk 《International Journal of Earth Sciences》1992,81(2):323-331
Zusammenfassung Eine umfassende Analyse und Modellierung der Entwicklungsgeschichte des Saar-Nahe-Beckens in SW-Deutschland wird bislang dadurch erschwert, daß erhebliche Teile der ursprünglichen permokarbonen Beckenfüllung bereits erodiert sind. Zur Quantifizierung der maximalen Überlagerung des heutigen Aufschlußniveaus wurde der Kompaktionsgrad von Tonsteinen mit Hilfe geophysikalischer Bohrlochmessungen untersucht. Es kann eine maximale Überlagerung bestimmt werden, die im SW des Saar-Nahe-Beckens 1950 m und im NE 2400 m beträgt (bezogen auf heutiges Meeresspiegelniveau). Aufgrund paläogeographischer Argumente lassen sich diese Überlagerungswerte nur durch eine Sedimentabfolge mit permokarbonem bzw. permischem Alter erklären. Eine maximale Versenkung im Mesozoikum oder Tertiär kann ausgeschlossen werden. Durch die Quantifizierung und zeitliche Einstufung der maximalen Versenkungstiefe kann die Subsidenz- und Hebungsgeschichte des Saar-Nahe-Bekkens seit dem Karbon lückenlos rekonstruiert werden.
Any detailed analysis and quantitative modelling of the formation of the Saar-Nahe-Becken in SW-Germany is hampered by a number of erosive events which removed major parts of the initial Permo-Carboniferous basin fill. The maximum overburden of the present outcrop level was reconstructed using shale-compaction data derived from sonic logs. The amount of erosion is estimated at 1950 m in the southwestern part of the Saar-Nahe-Basin, and 2400 m in the NE (relative to present sealevel). By comparison with paleogeographic and isopach data these values can only be explained by Permo-Carboniferous and Permian strata. A maximum burial during the Mesocoic or Tertiary can be ruled out. Knowing the amount and age of the maximum overburden, a continuous reconstruction of the burial history of the Saar-Nahe-Basin since the Carboniferous is possible.
Résumé Une analyse approfondie et une modélisation de l'histoire de la formation du bassin de la Sarre et de la Nahe (Allemagne du sud-ouest) ont été rendues difficiles jusqu'ici par le fait qu'une part considérable du remplissage permocarbonifére primitif du bassin a déjà été érodée. L'épaisseur maximale de la charge qui a surmonté le niveau actuellement en affleurement a été déduite du degré de compaction des argilites, analysé à l'aide de la diagraphie géophysique. Ces estimations ont fourni des valeurs maximales de 1.950 m dans le sud-ouest du bassin et de 2.400 m dans sa partie nord-est (relativement au niveau de la mer). Pour des raisons paléogéographiques il n'est possible de voir dans cette surcharge que des sédiments d'âge permo-carbonifère et permien: on peut montrer, en effet, que la subsidence maximale n'a pas eu lieu au Mésozoïque ou au Tertiaire. Connaissant ainsi l'importancce et l'âge de la surcharge actuellement disparue par érosion, on peut reconstituer l'histoire complète des mouvrements verticaux du bassin de la Sarre et de la Nahe depuis le Carbonifère.
, - -, - , , . , . , - 1950 , - 2400 . , - . , . .相似文献
84.
85.
Data from three annual surveys, covering inshore and offshore waters of the southeastern North Sea, were analysed to study recruitment variability in dab (Limanda limanda) over the period 1978–1997. Geometric mean abundance of 0- to 5-group dab was estimated using general linear models. Juvenile dab (0- and 1-group) were found over the entire area, from inside the estuaries to 50 m depth offshore. Environmental conditions (water temperature, wind stress, turbidity) affected the catch rates. The potential errors in the estimates of year-class strength, caused by differences in catchability, are discussed. The inter-annual pattern of year-class strength appeared to be established between ages 1 and 2, suggesting that factors determining recruitment are not restricted to the pelagic early life phase only, but also operate during the demersal juvenile phase. Recruitment variability at age 2 was in the order of 50–60% and appears to be equal to, or lower than, recruitment variability in plaice and sole. These results contradict expectations based on the concentration hypothesis, which states that the degree of variation in recruitment is inversely related to the degree of concentration during early life phases. 相似文献
86.
Long-term trends in ten non-target North Sea fish species 总被引:1,自引:1,他引:1
87.
88.
Martijn Woltering Pia Atahan Kliti Grice Henk Heijnis Kathryn Taffs John Dodson 《Quaternary Research》2014
Branched glycerol dialkyl glycerol tetraether (GDGT) distributions observed in a sediment core from Lake McKenzie were utilized to quantitatively reconstruct the pattern of mean annual air temperature (MAAT) from coastal subtropical eastern Australia between 37 and 18.3 cal ka BP and 14.0 cal ka BP to present. Both the reconstructed trend and amplitude of MAAT changes from the top of the sediment core were nearly identical to a local instrumental MAAT record from Fraser Island, providing confidence that in this sediment core branched GDGTs could be used to produce a quantitative record of past MAAT. The reconstructed trend of MAAT during 37 to 18.3 cal ka BP and timing of the Last Glacial Maximum (LGM) in the Lake McKenzie record were in agreement with previously published nearby marine climate records. The amplitude of lower-than-present MAAT during the LGM potentially provides information on the latitude of separation of the Tasman Front from the East Australian current in the subtropical western Pacific. The Lake McKenzie record shows an earlier onset of near modern day warm temperatures in the early Holocene compared to marine records and the presence of a warmer than present day period during the mid-Holocene. 相似文献
89.
Friederike Bungenstock Henk J. T. Weerts 《International Journal of Earth Sciences》2010,99(8):1687-1706
A few years ago, a new relative sea-level curve for northwest Germany was constructed for the entire German North Sea coast.
It is characterised by several suspected sea-level fluctuations. To test this curve for local effects, it was broken down
into five relative sea-level curves representative for five coastal sections. The relative sea-level curves were corrected
for tidal effects and also, a rough first correction for compaction was applied. The five curves all differ from the original
curve and from each other. Most of the suspected sea-level fluctuations in the original curve cannot be supported and are
discussed as data-artefacts or local effects. Around AD 800–1000 all curves show stagnation or drop of sea-level. Thus, this
signal is discussed as of over-regional stratigraphic meaning. This study is a first step (1) to show that several curves
are needed to demonstrate the Holocene sea-level history of such a big area as the entire German North Sea coast and (2) to
establish reliable relative sea-level curves for the German North Sea coast. Further research is necessary to apply detailed
corrections especially with respect to compaction-prone data and to improve the individual curves. 相似文献
90.
Craig R. Sloss Brian G. Jones Brendan P. Brooke Henk Heijnis Colin V. Murray-Wallace 《Journal of Paleolimnology》2011,46(4):561-577
Sedimentation rates over the last 100 years within two lagoons on the southeast coast of Australia, Lake Illawarra and St
Georges Basin, have been quantified to determine the effects of catchment land use change and native vegetation clearance
on infill rates, and spatial variations in the rate at which the estuaries have filled. Both catchments have similar lake
and catchment area but have experience different degrees of modification due to land clearing for agriculture practices, urbanisation
and industrialisation. Results indicate that in the heavily modified catchment of Lake Illawarra sedimentation rates close
to fluvial deltas can be in excess of 16 mm/year, and between 2 and 4 mm/year in the adjacent central basin. This is approximately
an order of magnitude greater than the pre-European rates. In contrast, at St Georges Basin, where the catchment has experienced
much less modification, sedimentation rates in the central basin appear to have remained close to those prior to European
settlement. However, sedimentation rates in the urbanized margin of St Georges Basin are relatively high (up to 4.4 mm/year).
This rapid modern sedimentation in the margin of the estuarine embayments has been detected in several other estuaries in
the region. However the degree of sedimentation within the bay-head deltas, and more significantly in the central basin appears
proportional to the degree clearance of native vegetation (forest) in the catchment, urban expansion and development of heavy
industry in the respective catchment areas. 相似文献