全文获取类型
收费全文 | 124篇 |
免费 | 0篇 |
专业分类
测绘学 | 6篇 |
大气科学 | 23篇 |
地球物理 | 34篇 |
地质学 | 47篇 |
海洋学 | 6篇 |
天文学 | 5篇 |
自然地理 | 3篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 6篇 |
2016年 | 2篇 |
2015年 | 7篇 |
2014年 | 5篇 |
2013年 | 7篇 |
2012年 | 4篇 |
2011年 | 6篇 |
2010年 | 6篇 |
2009年 | 13篇 |
2008年 | 6篇 |
2007年 | 4篇 |
2006年 | 8篇 |
2005年 | 6篇 |
2004年 | 7篇 |
2003年 | 8篇 |
2002年 | 5篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1982年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
排序方式: 共有124条查询结果,搜索用时 15 毫秒
41.
42.
Sébastien Nomade Jean-François Pastre Alison Pereira Alexandra Courtin-Nomade Vincent Scao 《Comptes Rendus Geoscience》2017,349(2):71-80
Since the 1960s, an early explosive activity in the Mont-Dore Massif is associated with a major pyroclastic rhyolitic eruption (5–7 km3) known as the “Grande Nappe” (GN). This event, linked to the formation of a 6-km-diameter cryptic caldera named “Haute Dordogne”, was before our investigation dated by 40Ar/39Ar at 3.07 ± 0.04 Ma. Our new single-crystal laser fusion 40Ar/39Ar dates obtained on two outcrops of the GN (Rochefort-Montagne and Ludières) questioned several hypotheses made concerning this “landmark” event of the Mont-Dore Massif history. We demonstrate that: (1) the GN rhyolitic eruption has occurred much later than previously estimated (i.e. 2.77 ± 0.02–0.07 Ma full external uncertainties); (2) the correlation made between the Vendeix rhyolitic complexes (intra-caldera position) dated back to 2.74 ± 0.04 Ma and the GN is proposed; (3) xenocryst contamination could be very high (i.e. 70% for the Rochefort-Montagne GN outcrop) and explains the noticeable older age obtained previously; (4) a link between the GN eruption and the formation of a caldera is questionable; the hypothesis of a northward-oriented blast channeled eastward toward the paleo-Allier River is thus proposed. 相似文献
43.
Maksim Bano Olivier Loeffler Jean-François Girard 《Comptes Rendus Geoscience》2009,341(10-11):846-858
Ground penetrating radar (GPR) is a non-destructive method which, over the past 10 years, has been successfully used not only to estimate the water content of soil, but also to detect and monitor the infiltration of pollutants on sites contaminated by light non-aqueous phase liquids (LNAPL). We represented a model water table aquifer (72 cm depth) by injecting water into a sandbox that also contains several buried objects. The GPR measurements were carried out with shielded antennae of 900 and 1200 MHz, respectively, for common mid point (CMP) and constant offset (CO) profiles. We extended the work reported by Loeffler and Bano by injecting 100 L of diesel fuel (LNAPL) from the top of the sandbox. We used the same acquisition procedure and the same profile configuration as before fuel injection. The GPR data acquired on the polluted sand did not show any clear reflections from the plume pollution; nevertheless, travel times are very strongly affected by the presence of the fuel and the main changes are on the velocity anomalies. We can notice that the reflection from the bottom of the sandbox, which is recorded at a constant time when no fuel is present, is deformed by the pollution. The area close to the fuel injection point is characterized by a higher velocity than the area situated further away. The area farther away from the injection point shows a low velocity anomaly which indicates an increase in travel time. It seems that pore water has been replaced by fuel as a result of a lateral flow. We also use finite-difference time-domain (FDTD) numerical GPR modelling in combination with dielectric property mixing models to estimate the volume and the physical characteristics of the contaminated sand. 相似文献
44.
The trace element compositions of S-type granites: evidence for disequilibrium melting and accessory phase entrainment in the source 总被引:4,自引:2,他引:2
Arnaud Villaros Gary Stevens Jean-François Moyen Ian S. Buick 《Contributions to Mineralogy and Petrology》2009,158(4):543-561
Within individual plutons, the trace element concentrations in S-type granites generally increase with maficity (total iron
and magnesium content and expressed as atomic Fe + Mg in this study); the degree of variability in trace element concentration
also expands markedly with the same parameter. The strongly peraluminous, high-level S-type granites of the Peninsular Pluton
(Cape Granite Suite, South Africa) are the product of biotite incongruent melting of a metasedimentary source near the base
of the crust. Leucogranites within the suite represent close to pure melts from the anatectic source and more mafic varieties
represent mixtures of melt and peritectic garnet and ilmenite. Trace elements such as Rb, Ba, Sr and Eu, that are concentrated
in reactant minerals in the melting process, show considerable scatter within the granites. This is interpreted to reflect
compositional variation in the source. In contrast, elements such as LREE, Zr and Hf, which are concentrated within refractory
accessory phases (zircon and monazite), show well-defined negative correlations with increasing SiO2 and increase linearly with increasing maficity. This is interpreted to reflect coupled co-entrainment of accessory minerals
and peritectic phases to the melt: leucocratic rocks cannot have evolved from the more mafic compositions in the suite by
a process of fractional crystallisation because in this case they would have inherited the zircon-saturated character of this
hypothetical earlier magma. Trace element behaviour of granites from the Peninsular Pluton has been modelled via both equilibrium
and disequilibrium trace element melting. In the disequilibrium case, melts are modelled as leaving the source with variable
proportions of entrained peritectic phases and accessory minerals, but before the melt has dissolved any accessory minerals.
Thus, the trace element signature of the melt is largely inherited from the reactants in the melting reaction, with no contribution
from zircon and monazite dissolution. In the equilibrium case, melt leaves the source with entrained crystals, after reaching
zircon and monazite saturation. A significant proportion of the rocks of the Peninsular Pluton have trace element concentrations
below those predicted by zircon and monazite saturation. In the case of the most leucocratic rocks all compositions are zircon
undersaturated; whilst the majority of the most mafic compositions are zircon oversaturated. However, in both cases, zircon
is commonly xenocrystic. Thus, the leucocratic rocks represent close to pure melts, which escaped their sources rapidly enough
that some very closely match the trace element disequilibrium melting model applied in this study. Zircon dissolution rates
allow the residency time for the melt in the source to be conservatively estimated at less than 500 years. 相似文献
45.
46.
Jean-François Lestrade Dayton L. Jones Robert A. Preston Robert B. Phillips 《Astrophysics and Space Science》1994,212(1-2):251-260
The displacement of a radio-emitting star around the barycenter of a possible planetary system can be measured by astrometric very long baseline interferometry (VLBI) observations. We have observed the radio-emitting star
2 CrB at 8 epochs over 5 years by VLBI and fitted its 5 astrometric parameters to the observed coordinates. The post-fit coordinate residuals have an rms scatter of 0.22 milliarcseconds and show no systematic behavior. We use this result to set a limit on the presence of planets around
2 CrB and conclude that our present VLBI astrometric precision corresponds to the threshold to detect a Jupiter-like planet around this star. We also discuss the astrometric monitoring program of 11 radio-emitting stars that we are conducting for the Hipparcos space mission and its possible contribution to a long-term planet search program.Paper presented at the Conference onPlanetary Systems: Formation, Evolution, and Detection held 7–10 December, 1992 at CalTech, Pasadena, California, U.S.A. 相似文献
47.
Etienne Balan Marc Blanchard Jean-François Hochepied Michele Lazzeri 《Physics and Chemistry of Minerals》2008,35(5):279-285
The theoretical infrared (IR) and Raman spectra of bayerite (β-Al(OH)3) are computed in the density functional theory framework, using the linear response theory. The results are consistent with
the occurrence of six non-equivalent OH groups in a bayerite structure with space group P21/n. Similar to gibbsite, the transmission powder IR spectrum of bayerite in the region of the OH stretching bands is found to
depend on the shape of particles. In particular, the broadening of the strong band observed at about 3,460 cm−1 in the spectrum of Al hydroxides is related to the electrostatic charges occurring at the surface of the polarized dielectric
particles. The experimental correlation observed between the shape of this band and morphological parameters has therefore
a physical, instead of chemical, origin. 相似文献
48.
Wind in Ireland: long memory or seasonal effect? 总被引:1,自引:1,他引:0
Jean-Christophe Bouette Jean-François Chassagneux David Sibai Rémi Terron Arthur Charpentier 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(3):141-151
Since Haslett and Raftery’s paper Space-Time Modelling with Long-Memory Dependence: Assessing Ireland’s Wind Power Resource (1989), modelling meteorological time series with long memory processes, in particular the ARFIMA model has become very common. Haslett and Raftery fitted an ARFIMA model on Irish daily wind speeds. In this paper, we try to reproduce Haslett and Raftery’s results (focusing on the dynamic
of the wind process, and not on cross-correlation and space dependencies), and show that an ARFIMA model does not properly capture the behaviour of the series (in Modelling daily windspeed in Ireland section). Indeed, the
series show a periodic behaviour, that is not taken into account by the ARFIMA model. Removing this periodic behaviour yields no results either, we therefore try to fit a GARMA model that takes into account both seasonality and long memory (in Seasonality and long memory using GARMA models section). If a GARMA process can be fitted to the data to model Irish daily data, we will show that these models could also be used to model Dutch hourly data.
相似文献
Arthur CharpentierEmail: |
49.
Global and regional evolution of short-lived radiatively-active gases and aerosols in the Representative Concentration Pathways 总被引:3,自引:0,他引:3
Jean-Fran?ois Lamarque G. Page Kyle Malte Meinshausen Keywan Riahi Steven J. Smith Detlef P. van Vuuren Andrew J. Conley Francis Vitt 《Climatic change》2011,109(1-2):191-212
In this paper, we discuss the results of 2000?C2100 simulations following the emissions associated with the Representative Concentration Pathways (RCPs) with a chemistry-climate model, focusing on the changes in 1) atmospheric composition (troposphere and stratosphere) and 2) associated environmental parameters (such as nitrogen deposition). In particular, we find that tropospheric ozone is projected to decrease (RCP2.6, RCP4.5 and RCP6) or increase (RCP8.5) between 2000 and 2100, with variations in methane a strong contributor to this spread. The associated tropospheric ozone global radiative forcing is shown to be in agreement with the estimate used in the RCPs, except for RCP8.5. Surface ozone in 2100 is projected to change little compared from its 2000 distribution, a much-reduced impact from previous projections based on the A2 high-emission scenario. In addition, globally-averaged stratospheric ozone is projected to recover at or beyond pre-1980 levels. Anthropogenic aerosols are projected to strongly decrease in the 21st century, a reflection of their projected decrease in emissions. Consequently, sulfate deposition is projected to strongly decrease. However, nitrogen deposition is projected to increase over certain regions because of the projected increase in NH3 emissions. 相似文献
50.
Jean-François Ghienne Julien Moreau Lionel Degermann Jean-Loup Rubino 《International Journal of Earth Sciences》2013,102(2):455-482
The stratigraphic record of the eastern Murzuq Basin has been importantly influenced by deformation resulting in angular and/or deeply erosional unconformities, though the overall context is intracratonic. Major transgressive events and the Ordovician glaciation are nevertheless documented, allowing the delineation of tectonic-, eustasy- or climate-driven unconformities. Lower Palaeozoic key events and related unconformities that characterize the North Gondwana platform have therefore a signature in the eastern Murzuq Basin. The basement/cover unconformity, also known as the infra-Tassilian surface, truncates all the deformed and metamorphosed Lower Cambrian and older rocks. Above is a ?Middle Cambrian to Lower Ordovician megasequence (Murizidié and Hasawnah Fms.), which is in turn truncated by an intra-Ordovician, angular unconformity. This megasequence is unconformably overlain by a Middle Ordovician (Hawaz Fm.) to Silurian (Tanzzuft and Akakus Fms) megasequence, which includes the Upper Ordovician glaciogenic unit (Mamuniyat Fm.), bounded at the base by a polygenic glacial erosion surface showing corrugated glacial lineations, tillites, and glaciotectonic structures. The Middle Ordovician to Silurian megasequence is finally truncated by a base-Devonian, angular unconformity overlain by fluvial sandstones. Regarding the possibility that those fluvial deposits may be as younger as Late Devonian in the eastern Murzuq Basin based on palaeoflora, the so-called Caledonian unconformity might be here a much younger (mid-Eifelian?) surface, and the occurrence of the Lower Devonian “Tadrart Fm.” is questioned. The Upper Ordovician glacial erosion surface, which is sometimes referred to as the Taconic unconformity, usually truncates Middle Ordovician strata in the Murzuq Basin but reaches significantly deeper stratigraphic levels in places that have been previously involved in the intra-Ordovician deformation event. In the Murizidié (southeastern Murzuq Basin), the infra-Tassilian surface, the intra-Ordovician unconformity, and the Upper Ordovician glacial erosion surface amalgamate together. Here, an estimate of the glacial erosion depth cannot be derived from the stratigraphic hiatus beneath the glacial incision, the main part of which relate to the intra-Ordovician tectonic event. The Upper Ordovician climate-related glacial erosion surface is not a valid unconformity for a sequence hierarchy framework of the Lower Palaeozoic, although it presents most of the physical attributes of tectonic-driven unconformities. 相似文献