全文获取类型
收费全文 | 349篇 |
免费 | 19篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 10篇 |
大气科学 | 40篇 |
地球物理 | 94篇 |
地质学 | 123篇 |
海洋学 | 23篇 |
天文学 | 58篇 |
自然地理 | 23篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 12篇 |
2018年 | 13篇 |
2017年 | 15篇 |
2016年 | 13篇 |
2015年 | 14篇 |
2014年 | 16篇 |
2013年 | 26篇 |
2012年 | 16篇 |
2011年 | 41篇 |
2010年 | 17篇 |
2009年 | 32篇 |
2008年 | 22篇 |
2007年 | 19篇 |
2006年 | 12篇 |
2005年 | 10篇 |
2004年 | 15篇 |
2003年 | 11篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1965年 | 1篇 |
1960年 | 1篇 |
1958年 | 1篇 |
1956年 | 1篇 |
1949年 | 1篇 |
1939年 | 1篇 |
1937年 | 1篇 |
排序方式: 共有371条查询结果,搜索用时 93 毫秒
91.
A multi-model ensemble approach for assessment of climate change impact on surface winds in France 总被引:2,自引:1,他引:1
Statistical downscaling of 14 coupled atmosphere-ocean general circulation models (AOGCM) is presented to assess potential
changes of the 10 m wind speeds in France. First, a statistical downscaling method is introduced to estimate daily mean 10 m
wind speed at specific sites using general circulation model output. Daily 850 hPa wind field has been selected as the large
scale circulation predictor. The method is based on a classification of the daily wind fields into a few synoptic weather
types and multiple linear regressions. Years are divided into an extended winter season from October to March and an extended
summer season from April to September, and the procedure is conducted separately for each season. ERA40 reanalysis and observed
station data have been used to build and validate the downscaling algorithm over France for the period 1974–2002. The method
is then applied to 14 AOGCMs of the coupled model intercomparison project phase 3 (CMIP3) multi-model dataset. Three time
periods are focused on: a historical period (1971–2000) from the climate of the twentieth century experiment and two climate
projection periods (2046–2065 and 2081–2100) from the IPCC SRES A1B experiment. Evolution of the 10 m wind speed in France
and associated uncertainties are discussed. Significant changes are depicted, in particular a decrease of the wind speed in
the Mediterranean area. Sources of those changes are investigated by quantifying the effects of changes in the weather type
occurrences, and modifications of the distribution of the days within the weather types. 相似文献
92.
We report in-situ produced 10 Be data from the Gorge du Diable (French Western Alps) to date and quantify bedrock gorge incision into a glacial hanging valley. We sampled gorge sidewalls and the active channel bed to derive both long-term and present-day incision rates. 10 Be ages of sidewall profiles reveal rapid incision through the late Holocene (ca 5 ka) at rates ranging from 6.5 to 13 mm yr−1 . Present-day incision rates are significantly lower and vary from 0.5 to 3 mm yr−1 within the gorge. Our data imply either delayed initiation of gorge incision after final ice retreat from internal Alpine valleys at ca 12 ka, or post-glacial surface reburial of the gorge. Our results suggest that fluvial incision rates >1 cm yr−1 into crystalline bedrock may be encountered in transient landscape features induced by glacial-interglacial transitions. 相似文献
93.
We present experiments of upraising and relaxing topographies showing that peneplanation can occur above the ultimate base level (sea level). After active uplift, the erosion of a topography bounded by a piedmont generates a final smooth and highly elevated topography. Smoothing at high elevation is even possible during active uplift if the evolution of topography is disrupted by the deposition of the products of erosion on its piedmont which is the case at the transition from underfilled to overfilled conditions in foreland basins. 相似文献
94.
Almudena Fontán Manuel González Neil Wells Michael Collins Julien Mader Luis Ferrer Ganix Esnaola Adolfo Uriarte 《Continental Shelf Research》2009,29(8):998-1007
The Basque coastal area, in the southeastern Bay of Biscay, can be characterised as being more influenced by land climate and inputs, than other typically ‘open sea’ areas. The influence of coastal processes, together with the presence of irregular and steep topography, complicate greatly the water circulation patterns. Water movement along the Basque coastal area is not well understood; observations are scarce and long-term current records are lacking. The knowledge available is confined to the surface currents: the surface water circulation is controlled mainly by wind forcing, with tidal and density currents being weak. However, there is a lack of knowledge available on currents within the lower levels of the water column; likewise, on the main time-scales involved in the water circulation. This study quantifies the contribution of the tidal and wind-induced currents, to the overall water circulation; it identifies the main time-scales involved within the tidal and wind-induced flows, investigating difference in such currents, throughout the water column, within Pasaia Bay (Basque coast). Within this context, extensive oceanographic and meteorological data have been obtained, in order to describe the circulation. The present investigation reveals that the circulation, within the surface and the sub-surface waters, is controlled mainly by wind forcing fluctuations, over a wide range of meteorological frequencies: third-diurnal, semidiurnal and diurnal land–sea breezes; synoptic variability; frequencies, near fortnightly periods; and seasonal. At the lower levels of the water column, the main contribution to the water circulation arises from residual currents, followed by wind-induced currents on synoptic time-scales. In contrast, tidal currents contribute minimally to the overall circulation throughout the water column. 相似文献
95.
The applicability of explicit time integration in structural dynamics is often limited by a restrictively small solution time increment. This paper presents a mass penalty technique whereby the highest natural frequencies of a dynamic system can be preferentially lowered with only a minimal effect on the structural modes. Because the critical time increment is inversely proportional to the highest natural frequency, a dramatic increase in the solution time increment may be achieved. An expression is developed for the frequency shift and a number of useful properties of this technique are derived analytically for linear systems. Its utility in non-linear analyses is demonstrated with several examples. 相似文献
96.
97.
98.
Bally G Mesnage V Deloffre J Clarisse O Lafite R Dupont JP 《Marine pollution bulletin》2004,49(3):163-173
A seasonal field study was carried out in the Seine estuary to determine the chemistry of sediment porewaters using the 'peeper' technique and changes in the elevation of the mudflats using the 'Altus' technique. This approach allowed us to evaluate the release of nutrients and to link these releases to the sediment hydrodynamics. Our results show that nutrient and organic matter cycling in a Seine estuary mudflat exhibits a seasonal behaviour, which is mainly influenced by variations in hydrodynamics. Sediments, rich organic matter, were input during floods and they were mineralized during summer and autumn, releasing nutrients and dissolved organic carbon into the sediment porewaters. The nutrient release, including ammonium, is mainly linked to the mineralization of organic matter, while the release of phosphate is delayed. The delay could be the result of phosphate association with organic matter and/or its co-precipitation with calcium and iron. 相似文献
99.
Julien Vaudan Aurèle Parriaux Laurent Tacher Gianni della Valle 《Eclogae Geologicae Helvetiae》2005,98(3):371-383
The alpine valley of the Haute-Sarine is on several accounts representative of the alluvial aquifers of mountain by its very
environment and its hydrogeologic characteristics. The investigations and the analysis carried out within the framework of
this study enabled us to improve knowledge on the Quaternary filling of the valley and to highlight the preferential supplies
of the aquifer by infiltration of the river and precipitations and also by the underground contributions of evaporitic karsts.
We also could note the opulence of groundwater resources of the Haute-Sarine both from the qualitative and the quantitative
points of view. The knowledge of these typical characteristics of alluvial aquifers of high altitude allowed finally the development
of a concept of management and protection of groundwater resources that falls under a sustainable development policy of the
groundwater storage in the alpine areas.
Manuscrit re?u le 4 février 2003 Révision acceptée le 30 mars 2005 相似文献
100.
Souad Boubekraoui Michel Courteaud Maurice Aubert Yves Albouy Jean Coudray 《Journal of Applied Geophysics》1998,40(4):165-177
In order to investigate aquifers, several geophysical surveys have been carried out in the Baril area of the southern flank of Piton de la Fournaise volcano on Reunion in the Indian Ocean using audiomagnetotelluric (AMT), very-low-frequency (VLF) and self-potential (SP) methods. We present the results with emphasis on a comparison between SP data and the findings of geoelectric surveys. AMT soundings have indicated, from the surface downward, three layers: (i) resistive volcanic rocks, (ii) an intermediate resistivity layer, and (iii) a conductive basement attributed to a seawater-bearing aquifer. VLF measurements allow the mapping of the first layer apparent resistivity, and therefore its bottom, when the true resistivity is supposed to be isotropic and homogenous. When this assumption does not hold, only the SP method permits the mapping of this bottom. Because of the good agreement between the SP and electromagnetic results, we propose the SP method as the first tool that should be used in studying shallow hydrogeological structures in volcanic areas. 相似文献