全文获取类型
收费全文 | 189篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 7篇 |
地球物理 | 43篇 |
地质学 | 83篇 |
海洋学 | 16篇 |
天文学 | 15篇 |
综合类 | 2篇 |
自然地理 | 21篇 |
出版年
2021年 | 1篇 |
2019年 | 3篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 11篇 |
2012年 | 6篇 |
2011年 | 7篇 |
2010年 | 6篇 |
2009年 | 10篇 |
2008年 | 9篇 |
2007年 | 8篇 |
2006年 | 11篇 |
2005年 | 14篇 |
2004年 | 17篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 5篇 |
1998年 | 6篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1978年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有191条查询结果,搜索用时 437 毫秒
181.
182.
183.
Field observations of an evolving rip current on a meso-macrotidal well-developed inner bar and rip morphology 总被引:1,自引:0,他引:1
Nicolas Bruneau Bruno Castelle Philippe Bonneton Rodrigo Pedreros Rafael Almar Natalie Bonneton Patrice Bretel Jean-Paul Parisot Nadia Snchal 《Continental Shelf Research》2009,29(14):1650-1662
The Aquitanian Coast (France) is a high-energy meso-macrotidal environment exhibiting a highly variable double sandbar system. The inner and the outer bar generally exhibit a bar and rip morphology and persistent crescentic patterns, respectively. In June 2007, an intense five-day field experiment was carried out at Biscarrosse Beach. A large array of sensors was deployed on a well-developed southward-oriented bar and rip morphology. Daily topographic surveys were carried out together with video imaging to investigate beach morphodynamic evolution. During the experiment, offshore significant wave height ranged from 0.5 to 3 m, with a persistent shore-normal angle. This paper identifies two types of behavior of an observed rip current: (1) for low-energy waves, the rip current is active only between low and mid tide with maximum mean rip current velocity reaching 0.8 m/s for an offshore significant wave height (Hs) lower than 1 m; (2) for high-energy waves (Hs≈ 2.5–3 m), the rip current was active over the whole tide cycle with the presence of persistent intense offshore-directed flows between mid and high tide. For both low and high-energy waves, very low-frequency pulsations (15–30 min) of the mean currents are observed on both feeder and rip channels.A persistent slow shoreward migration of the sandbar was observed during the experiment while no significant alongshore migration of the system was measured. Onshore migration during the high-energy waves can be explained by different sediment transport processes such as flow velocity skewness, wave asymmetry or bed ventilation. High-frequency local measurements of the bed evolution show the presence of significant (in the order of 10 cm) fluctuations (in the order of 1 h). These fluctuations, observed for both low- and high-energy waves, are thought to be ripples and megaripples, respectively and may play an important but still poorly understood role in the larger scale morphodynamics. The present dataset improves the knowledge of rip dynamics as well as the morphological response of strongly alongshore non-uniform meso-macrotidal beaches. 相似文献
184.
Catherine Pierre Marie-Madeleine Blanc-Valleron Jér?me Demange Omar Boudouma Jean-Paul Foucher Thomas Pape Tobias Himmler Noemi Fekete Volkhard Spiess 《Geo-Marine Letters》2012,32(5-6):501-513
The southwest African continental margin is well known for occurrences of active methane-rich fluid seeps associated with seafloor pockmarks at water depths ranging broadly from the shelf to the deep basins, as well as with high gas flares in the water column, gas hydrate accumulations, diagenetic carbonate crusts and highly diverse benthic faunal communities. During the M76/3a expedition of R/V METEOR in 2008, gravity cores recovered abundant authigenic carbonate concretions from three known pockmark sites—Hydrate Hole, Worm Hole, the Regab pockmark—and two sites newly discovered during that cruise, the so-called Deep Hole and Baboon Cluster. The carbonate concretions were commonly associated with seep-benthic macrofauna and occurred within sediments bearing shallow gas hydrates. This study presents selected results from a comprehensive analysis of the mineralogy and isotope geochemistry of diagenetic carbonates sampled at these five pockmark sites. The oxygen isotope stratigraphy obtained from three cores of 2–5?m length indicates a maximum age of about 60,000–80,000?years for these sediments. The authigenic carbonates comprise mostly magnesian calcite and aragonite, associated occasionally with dolomite. Their very low carbon isotopic compositions (–61.0?<?δ13C ‰ V-PDB?<?–40.1) suggest anaerobic oxidation of methane (AOM) as the main process controlling carbonate precipitation. The oxygen isotopic signatures (+2.4?<?δ18O ‰ V-PDB?<?+6.2) lie within the range in equilibrium under present-day/interglacial to glacial conditions of bottom seawater; alternatively, the most positive δ18O values might reflect the contribution of 18O-rich water from gas hydrate decomposition. The frequent occurrence of diagenetic gypsum crystals suggests that reduced sulphur (hydrogen sulphide, pyrite) from sub-seafloor sediments has been oxidized by oxygenated bottom water. The acidity released during this process can potentially induce the dissolution of carbonate, thereby providing enough Ca2+ ions for pore solutions to reach gypsum saturation; this is thought to be promoted by the bio-irrigation and burrowing activity of benthic fauna. The δ18O–δ13C patterns identified in the authigenic carbonates are interpreted to reflect variations in the rate of AOM during the last glacial–interglacial cycle, in turn controlled by variably strong methane fluxes through the pockmarks. These results complement the conclusions of Kasten et al. in this special issue, based on authigenic barite trends at the Hydrate Hole and Worm Hole pockmarks which were interpreted to reflect spatiotemporal variations in AOM related to subsurface gas hydrate formation–decomposition. 相似文献
185.
186.
Jean-Paul?SimjouwEmail author Margaret?R.?Mulholland Elizabeth?C.?Minor 《Estuaries and Coasts》2004,27(6):986-998
Aureococcus anophagefferens, the pelagophyte responsible for brown tide blooms, occurs in coastal bays along the northeast coast of the United States.
This species was identified in Chincoteague Bay, Maryland, in 1997 and has bloomed there since at least 1998. Time series
of dissolved organic matter (DOM) concentrations and characteristics are presented for two sites in Chincoteague Bay: one
that experienced a brown tide bloom in 2002 and one that did not. Characteristics of the bulk DOM pool were obtained using
dissolved organic carbon (DOC) and ultraviolet-visible (UV-Vis) measurements (spectral slope and specific UV absorbance).
High molecular weight DOM (HMW-DOM) was characterized in terms of DOC concentration, carbon: nitrogen (C:N) ratio, isotopic
signature, and molecular-level characteristics as determined by direct temperature resolved mass spectrometry (DT-MS). Compositional
changes in the DOM pool are associated with brown tide blooms, although a direct relationship between DOM characteristics
and bloom development could not be confirmed. DOC measurements suggest that during the brown tide bloom, HMW-DOM was released
into the surface water. UV-Vis analysis on the bulk DOM and molecular-level characterization of the HMW-DOM using DT-MS show
that this material was optically active and more aromatic in nature. Based upon C:N ratio and HMW-DOC measurements, it appears
that this HMW-DOM was more nitrogen enriched. Whether this material was released as exudates or was due to lysis ofA. anophagefferens could not be determined. 相似文献
187.
188.
The main argument for assigning a glacial origin to the basal conglomeratic levels of the west-Congolan geosyncline has been the presence of polyhedral striated pebbles.New observations have enabled us to show that this striation was due to the internal structure of the pebbles which resulted from the breaking up of the underlying quartzitic layers of the Mayombian axis (the Moussouva series).These conglomeratic formations are marine deposits laid down in a geosyncline which had unstable margins, especially on the western side where the Mayombian Belt was being uplifted.This again calls into question the existence of a Precambrian ice-sheet in Central Africa. 相似文献
189.
Bénédicte Fruneau Benoît Deffontaines Jean-Paul Rudant Anne-Marie Le Parmentier 《Comptes Rendus Geoscience》2005,337(13):1173-1183
The Saint-Lazare area in Paris (France) has undergone important water pumping for the construction of the underground Haussmann–Saint-Lazare station for the EOLE subway line. This paper presents the monitoring of the small surface displacements related to this pumping activity, by classical SAR interferometry. Piezometric measurements provided on 87 piezometers by SNCF and IGC as well as precise levelling data acquired on 626 points by SNCF are also examined. Their comparison with interferometric results shows their good agreement and complementarity, as well as the potential ‘operationality’ of SAR interferometric approach in such a study. To cite this article: B. Fruneau et al., C. R. Geoscience 337 (2005). 相似文献
190.
Benoît Laignel Emmanuel Dupuis Alain Durand Jean-Paul Dupont Emmanuel Hauchard Nicolas Massei 《Comptes Rendus Geoscience》2006,338(8):556-564
An accurate quantification of erosion, based on high-frequency monitoring of river discharge and suspended sediment fluxes is proposed for two watersheds in the western Paris Basin, a sensitive area with respect to erosion phenomena. This continuous monitoring makes it possible to include flood events of short duration, but significant erosion potential. The obtained erosion rate (16 and 21 t?km?2?yr?1) is among the weakest of the planet (3.5 to 18?000 t?km?2?yr?1). However, this annual balance does not reflect the behaviour of these rivers which can be torrential in certain cases. To cite this article: B. Laignel et al., C. R. Geoscience 338 (2006). 相似文献