全文获取类型
收费全文 | 367篇 |
免费 | 1篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 15篇 |
地球物理 | 52篇 |
地质学 | 176篇 |
海洋学 | 38篇 |
天文学 | 68篇 |
综合类 | 1篇 |
自然地理 | 19篇 |
出版年
2024年 | 1篇 |
2022年 | 3篇 |
2021年 | 7篇 |
2020年 | 5篇 |
2019年 | 1篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 3篇 |
2013年 | 32篇 |
2012年 | 11篇 |
2011年 | 21篇 |
2010年 | 17篇 |
2009年 | 25篇 |
2008年 | 27篇 |
2007年 | 15篇 |
2006年 | 13篇 |
2005年 | 27篇 |
2004年 | 16篇 |
2003年 | 16篇 |
2002年 | 18篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 13篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1976年 | 3篇 |
1973年 | 2篇 |
1960年 | 1篇 |
排序方式: 共有373条查询结果,搜索用时 23 毫秒
141.
Jean-Pierre Lefebvre Sylvain Ouillon Vu Duy Vinh Robert Arfi Jean-Yves Panché Xavier Mari Chu Van Thuoc Jean-Pascal Torréton 《Geo-Marine Letters》2012,32(2):103-121
In the Bach Dang–Cam Estuary, northern Vietnam, mechanisms governing cohesive sediment aggregation were investigated in situ
in 2008–2009. As part of the Red River delta, this estuary exhibits a marked contrast in hydrological conditions between the
monsoon and dry seasons. The impact on flocculation processes was assessed by means of surveys of water discharge, suspended
particulate matter concentration and floc size distributions (FSDs) conducted during a tidal cycle at three selected sites
along the estuary. A method was developed for calculating the relative volume concentration for the modes of various size
classes from FSDs provided by the LISST 100X (Sequoia Scientific Inc.). It was found that all FSDs comprised four modes identified
as particles/flocculi, fine and coarse microflocs, and macroflocs. Under the influence of the instantaneous turbulent kinetic
energy, their proportions varied but without significant modification of their median diameters. In particular, when the turbulence
level corresponded to a Kolmogorov microscale of less than ∼235 μm, a major breakup of flocs resulted in the formation of
particles/flocculi and fine microflocs. Fluctuations in turbulence level were governed by seasonal variations in freshwater
discharge and by the tidal cycle. During the wet season, strong freshwater input induced a high turbulent energy level that
tended to generate sediment transfer from the coarser size classes (macroflocs, coarse microflocs) to finer ones (particles/flocculi
and fine microflocs), and to promote a transport of sediment seawards. During the dry season, the influence of tides predominated.
The turbulent energy level was then only episodically sufficiently high to generate transfer of sediment between floc size
classes. At low turbulent energy, modifications in the proportions of floc size classes were due to differential settling.
Tidal pumping produced a net upstream transport of sediment. Associated with the settling of sediment trapped in a near-bed
layer at low turbulent energy, this causes the silting up of the waterways leading to the harbour of Haiphong. 相似文献
142.
This work examines the links between tectonics and fluvial dynamics on the north-western margin of the French Central Massif. Geomorphological and sedimentological analyses of detrital deposits were carried out as the basis for correlating the different formations, and for reconstructing the palaeodrainage in the Creuse basin. Cross-sections of the valleys, longitudinal profiles of terraces and glacis indicate post-depositional deformation of about 50 m amplitude: uplift north and south of Guéret and in the Éguzon district. These deformations are related to the Central Massif uplift of 50 m above the Paris Basin since 1.1 Ma (OIS 32). The Creuse incision varies from 140 m in the Crozant anticline to 60 m in the Paris Basin. An Upper Pliocene palaeochannel located on the Sédelle–Ardentes–Issoudun lineament is evidenced by andalusite coming from the Fougères unit. The reactivation of the transverse faults between Le Pin and Le Menoux has distorted the middle terraces. The main knick points are mainly due to tectonics and have been persistent in the landscape since the Upper Pliocene. Their recession rate is controlled both by discharge and lithology. Tributary streams exhibit strong convexities, indicating that the erosional response to Pliocene uplift has not yet propagated into upland surfaces. 相似文献
143.
Narjess El Euch-El Koundi Serge Ferry Jean-Pierre Suc Georges Clauzon Mihaela Carmen Melinte-Dobrinescu Christian Gorini Anissa Safra Fouad Zargouni 《地学学报》2009,21(1):41-48
Outcrops, offshore wells, electric logs and seismic profiles from northern Tunisia provide an opportunity to decipher the Messinian Salinity Crisis in the Strait of Sicily. Messinian deposits (including gypsum beds) near the Tellian Range reveal two successive subaerial erosional surfaces overlain by breccias and marine Zanclean clays, respectively. In the Gulf of Tunis, Messinian thick evaporites (mostly halite) are strongly eroded by a fluvial canyon infilled with Zanclean clays. The first erosional phase is referred to the intra-Messinian tectonic phase and is analogous to that found in Sicily. The second phase corresponds to the Messinian Erosional Surface that postdates the marginal evaporites, to which the entire Sicilian evaporitic series must refer. The Western and Eastern Mediterranean basins were separated during deposition of the central evaporites. 相似文献
144.
Jean-Pierre Lorand Olivier Alard Ambre Luguet 《Earth and Planetary Science Letters》2010,289(1-2):298-310
Highly siderophile elements (Platinum-group elements, Au and Re) are currently assumed to reside inside base metal sulfides (BMS) in the convecting upper mantle. However, fertile lherzolites sampled by Pyrenean orogenic peridotite massifs are unexpectedly rich in 0.5–3 µm large micronuggets of platinum-group minerals (PGM). Among those, sulfides from the laurite-erlichmanite series (Ru, Os(Ir)S(As)2), Pt–Ir–Os alloys and Pt–Pd–Te–Bi phases (moncheite–merenskyite) are predominant. Not only the BMS phases but also the PGM micronuggets must be taken into account in calculation of the PGE budget of orogenic fertile lherzolites. Laurite is a good candidate for equilibrating the whole-rock budget of Os, Ir and Ru while accounting for supra-chondritic Ru/IrN. Textural relationships between PGMs and BMS highlight heterogeneous mixing between refractory PGMs (laurite/Pt–Ir–Os alloys) inherited from ancient refractory lithospheric mantle and late-magmatic metasomatic sulfides precipitated from tholeiitic melts. “Low-temperature” PGMs, especially Pt–Pd bismuthotellurides should be added to the list of mineral indicators of lithosphere refertilization process. Now disseminated within fertile lherzolites, “lithospheric“ PGMs likely account for local preservation of ancient Os model ages (up to 2 Ga) detected in BMS by in-situ isotopic analyses. These PGMs also question the reliability of orogenic lherzolites for estimating the PGE signature of the Primitive Silicate Earth. 相似文献
145.
de Mora S Tolosa I Fowler SW Villeneuve JP Cassi R Cattini C 《Marine pollution bulletin》2010,60(12):2323-2349
The composition and spatial distribution of various petroleum hydrocarbons (PHs), comprising both aliphatic and polycyclic aromatic hydrocarbons (PAHs), and selected chlorinated pesticides and PCBs were measured in biota and coastal sediments from seven countries in the Persian Gulf and the Gulf of Oman (Bahrain, Iran, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates). Evidence of extensive marine contamination with respect to organochlorinated compounds and PHs was not observed. Only one site, namely the BAPCO oil refinery in Bahrain, was considered to be chronically contaminated. Comparison of the results from this survey for Σ DDTs and Σ PCBs in rock oysters from the Gulf of Oman with similar measurements made at the same locations over the past two decades indicates a temporal trend of overall decreasing Σ PCB concentrations in oysters, whereas Σ DDTs levels have little changed during that period. 相似文献
146.
147.
Schweizerisches Komitee für Stratigraphie Thierry Adatte Jean-Pierre Berger Hansruedi Bläsi Reto Burkhalter Stephan DallAgnolo Danielle Decrouez Hanspeter Funk Heinz Furrer Yves Gouffon Hansruedi Graf Werner Heckendorn Wilfried Winkler 《Swiss Journal of Geoscience》2009,102(2):363-364
In September 2007 Föllmi and coauthors requested the approval of four lithostratigraphic terms of the Swiss Committee of Stratigraphy (SCS). These terms were to be used in their publication on the Cretaceous in the Helvetic realm (Föllmi et al. 2007). At its meeting on October 18, 2007, the SCS decided the following: The Tierwis Formation (replacing the Drusberg Formation) was accepted, with the reserve that a section at Tierwis should be published in the near future. For the former “Lower Orbitolina Beds” the term Rawil Member was accepted, but here too a better type section than the one at Rawil Pass should be published. The term Rohrbachstein bed should not be used as a formal unit because it describes only a minor lithologic variation within the Grünten Member. The term Plaine Morte bed for a thin condensed horizon can not be accepted due to the fact that its definition is based mainly on biostratigraphy. Furthermore, the duplication a locality term which is in use for a previously established lithostratigraphic unit should be avoided. 相似文献
148.
Luca Maltagliati Dmitry V. Titov Thérèse Encrenaz Francois Forget Horst U. Keller Jean-Pierre Bibring 《Icarus》2008,194(1):53-64
The OMEGA imaging spectrometer onboard the Mars Express spacecraft is particularly well suited to study in detail specific regions of Mars, thanks to its high spatial resolution and its high signal-to-noise ratio. We investigate the behavior of atmospheric water vapor over the four big volcanoes located on the Tharsis plateau (Olympus, Ascraeus, Pavonis and Arsia Mons) using the 2.6 μm band, which is the strongest and most sensitive H2O band in the OMEGA spectral range. Our data sample covers the end of MY26 and the whole MY27, with gaps only in the late northern spring and in northern autumn. The most striking result of our retrievals is the increase of water vapor mixing ratio from the valley to the summit of volcanoes. Corresponding column density is often almost constant, despite a factor of ∼5 decrease in air mass from the bottom to the top. This peculiar water enrichment on the volcanoes is present in 75% of the orbits in our sample. The seasonal distribution of such enrichment hints at a seasonal dependence, with a minimum during the northern summer and a maximum around the northern spring equinox. The enrichment possibly also has a diurnal trend, being the orbits with a high degree of enrichment concentrated in the early morning. However, the season and the solar time of the observations, due to the motion of the spacecraft, are correlated, then the two dependences cannot be clearly disentangled. Several orbits exhibit also spatially localized enrichment structures, usually ring- or crescent-shaped. We retrieve also the height of the saturation level over the volcanoes. The results show a strong minimum around the aphelion season, due to the low temperatures, while it raises quickly before and after this period. The enrichment is possibly generated by the local circulation characteristic of the volcano region, which can transport upslope significant quantities of water vapor. The low altitude of the saturation level during the early summer can then hinder the transport of water during this season. The influence of the coupling between atmosphere and surface, due mainly to the action of the regoliths, can also contribute partially to the observed phenomenon. 相似文献
149.
Elastic wave propagation in an irregularly layered medium 总被引:1,自引:0,他引:1
Rossana Vai Jos Manuel Castillo-Covarrubias Francisco J. Snchez-Sesma Dimitri Komatitsch Jean-Pierre Vilotte 《Soil Dynamics and Earthquake Engineering》1999,18(1):385
The indirect boundary element method (IBEM) is used to simulate wave propagation in two-dimensional irregularly layered elastic media for internal line sources. The method is based on the integral representation for scattered elastic waves using single layer boundary sources. Fulfillment of the boundary conditions leads to a system of integral equations. Results are obtained in the frequency domain and seismograins are computed through Fourier synthesis. In order to test and validate the method we present various comparisons between our results and the time series obtained analytically for a buried line source in a half-space and by using the recently developed spectral element method (SEM). 相似文献
150.
Jean-Claude Bader Gilles Belaud Jean-Pierre Lamagat Thibaud Ferret Philippe Vauchel 《水文科学杂志》2017,62(3):447-466
In the Senegal River valley and Niger Inner Delta, the annual floods inundate a wide floodplain consisting of a complex network of lakes and channels, where topographic information needed by standard hydraulic models is difficult to obtain. To represent the flood propagation between mainstream and floodplain, we use a model designed for flood propagation in river mainstreams with flat bed and large overflow and without topographic data. Depending on the water level in the riverbed, the model calibrated on the levels observed at two stations gives the level in the floodplains and propagation time between stations. Several cases are tested for various types of hydraulic connections between mainstream and floodplain. The model could correctly reproduce the flood rise and fall in the floodplain, even for a lake connected by a single channel to the riverbed or in the case of a strong attenuation of the flood between very distant stations. 相似文献