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61.
G��raldine Guerri Jean-Baptiste Daban Sylvie Robbe-Dubois Richard Douet Lyu Abe Jacques Baudrand Marcel Carbillet Anthony Boccaletti Philippe Bendjoya Carole Gouvret Farrokh Vakili 《Experimental Astronomy》2011,30(1):59-81
SPHERE (which stands for Spectro-Polarimetric High-contrast Exoplanet REsearch) is a second-generation Very Large Telescope (VLT) instrument dedicated to high-contrast direct imaging of exoplanets whose first-light is scheduled for 2011. Within this complex instrument one of the central components is the apodized Lyot coronagraph (ALC). The principal aim of this paper is to report the first laboratory experiment of the ALC designed for the SPHERE instrument. The performance and sensitivity of the optical configuration was first numerically studied with an end-to-end approach (see the results in paper I subtitled ??Detailed numerical study??). Made confident by the results, we then tested a prototype on an infrared coronagraphic bench. We measured the transmission profiles of the apodizer prototype and the coronagraphic performance of the apodized Lyot coronagraph in Y, J, and H bands. The coronagraph sensitivity to lateral and longitudinal misalignments of its three main components (apodizer, coronagraphic mask and Lyot stop) was finally studied in H band. We can conclude that the prototype meets the SPHERE technical requirements for coronagraphy. 相似文献
62.
63.
Darren M. O'Brien Paulo J.V. Garcia Jonathan Ferreira Sylvie Cabrit Luc Binette 《Astrophysics and Space Science》2004,292(1-4):609-617
The effects of phenomenological heating functions on the flow thermodynamics of cold T-Tauri disk winds are examined. Turbulent dissipation (mechanical) heating and a warm disk corona are invoked to heat the wind. The temperature and ionization evolution are solved for along the flow. The results allow the construction of synthetic observations; emission maps, forbidden line ratios, line fluxes and line profiles; and successfully reproduce a number of observed trends. Mechanical heating produces line ratios and fluxes that fit very well with observations. Invoking a warm disk corona successfully reproduces forbidden line profile low velocity components. 相似文献
64.
We analyze the process of resonance trapping due to Poynting–Robertson drag and Stokes drag in the frame of the restricted 3-body problem and in the case of external mean motion resonances. The numerical simulations presented are computed by using the 3-dimensional extended Schubart averaging (ESA) integrator developed by Moons (1994) for all mean motion resonances. We complete it by adding the contributions of the dissipative forces. To follow the philosophy of the initial integrator, we average the drag terms, but we do not make any expansion in series of eccentricity or inclination. We show our results, especially capture around asymmetric equilibria, and compare them to those found by Beaué and Ferraz-Mello (1993, 1994) and Liou et al. (1979). 相似文献
65.
Our research combines mean motion resonances and dissipative forces in the averaged elliptic spatial restricted three-body problem. The models presented can be applied in many contexts mixing resonances and dissipations,e.g., asteroid belt, transneptunian region, exoplanets, systems of planetary rings, etc. We propose a semi-numerical model that simulates the behaviour of test particles under the effect of generic forces, functions of powers of the position and/or of the velocity. This model is valid for any orbital eccentricities or inclinations, even at high values. Captures around symmetric and asymmetric equilibria are reproduced and the apparitions of a plateau of inclination for long periods of time are dectected. 相似文献
66.
Raluca Ciuraru Michael Ward Maxence Mendez Sylvie Gosselin Nicolas Visez Denis Petitprez 《Journal of Atmospheric Chemistry》2013,70(4):341-355
The present study focuses on the heterogeneous reaction between gaseous atomic chlorine and solid palmitic acid films, used as a proxy of the fatty acids detected in atmospheric airborne particles. This reaction is investigated in a coated wall flow tube reactor coupled to a molecular beam mass spectrometer. The reactive surfaces were prepared by coating the inner surface of the reactor. The initial Cl˙ and Cl2 uptake coefficient measured for these heterogeneous reactions is found to be fast: γo Cl?=?0.07. The rapid formation of hydrogen chloride corresponding with the disappearance of atomic chlorine is highlighted. Furthermore, the formation of new chlorinated species on the solid substrate has been detected by TOF SIMS analysis leading to an ageing process of the surface. A heterogeneous recombination of Cl atoms to Cl2 molecules was observed for aged surfaces. 相似文献
67.
Milan S. Dimitrijević Zoran Simić Andjelka Kovačević Aleksandar Valjarević Sylvie Sahal-Bréchot 《Journal of Astrophysics and Astronomy》2015,36(4)
We will consider Stark broadening of non hydrogenic spectral lines in the impact approximation in compact stars: pre-white dwarf and white dwarf atmospheres. In order to show an example, Stark broadening parameters have been calculated, using the impact semiclassical perturbation approach for four Xe VI spectral lines. Obtained results have been used to demonstrate the influence of Stark broadening in DA and DB white dwarf atmospheres. 相似文献
68.
Emilie Perraud Fleur Couvreux Sylvie Malardel Christine Lac Valéry Masson Odile Thouron 《Boundary-Layer Meteorology》2011,140(2):263-294
In numerical weather prediction and climate models, planetary boundary-layer (PBL) clouds are linked to subgrid-scale processes
such as shallow convection. A comprehensive statistical analysis of large-eddy simulations (LES), obtained for warm PBL cloud
cases, is carried out in order to characterize the distributions of the horizontal subgrid cloud variability. The production
of subgrid clouds is mainly associated with the variability of the total water content. Nevertheless, in the case of PBL clouds,
the temperature variability cannot be completely discarded and the saturation deficit, which summarizes both temperature and
total water fluctuations, provides a better representation of the cloud variability than the total water content. The probability
density functions (PDFs) of LES saturation deficit generally have the shape of a main asymmetric bell-shaped curve with a
more or less distinct secondary maximum specific to each type of PBL clouds. Unimodal theoretical PDFs, even those with a
flexible skewness, are not sufficient to correctly fit the LES distributions, especially the long tail that appears for cumulus
clouds. They do not provide a unified approach for all cloud types. The cloud fraction and the mean cloud water content, diagnosed
from these unimodal PDFs, are largely underestimated. The use of a double Gaussian distribution allows correction of these
errors on cloud fields and provides a better estimation of the cloud-base and cloud-top heights. Eventually, insights for
the design of a subgrid statistical cloud scheme are provided, in particular a new formulation for the weight of the two Gaussian
distributions and for the standard deviation of the convective distribution. 相似文献
69.
Criteria for the identification of ventifacts in the geological record: A review and new insights 总被引:1,自引:0,他引:1
Ventifacts (wind-worn stones) are typical of terrestrial environments remained very long without any vegetation, under hot or cold climates. Therefore, within the sedimentary record, they can allow recognizing desert conditions, even where no aeolian dune deposits are preserved. There seems that, in the recent literature, pebbles and cobbles from various palaeoenvironments were mistaken for ventifacts. This may partly be explained by the scatter and relative scarcity of illustrations to which refer. The aim of this paper is to help recognizing ventifacts in the sedimentary record, based on a critical review of the diagnostic properties generally used, and on new studies permitting to suggest additional criteria. After an evaluation of the sedimentary contexts favourable to preserving ventifacts, the distinctive characters that could be seen on each one are treated in order of increasing alteration of the original appearance: surface features, medium-scale features (new types of pit especially), and general shape. Finally, the problem of distinguishing between ventifacts and aquafacts is approached. 相似文献
70.
A 70 Ma record of suprasolidus conditions in the large,hot, long‐duration Grenville Orogen 下载免费PDF全文
François Turlin Clara Deruy Aurélien Eglinger Olivier Vanderhaeghe Anne‐Sylvie André‐Mayer Marc Poujol Abdelali Moukhsil Fabien Solgadi 《地学学报》2018,30(3):233-243
Petrochronology of magmatic monazite and apatite from a single paragneiss leucosome derived by in situ partial melting documents the thermal evolution of the Allochthonous Belt of the central Grenville Province. Monazite records suprasolidus metamorphism from ca. 1080 to 1020 Ma under high temperature up to 850°C. Apatite from the same leucosome yields an age of 960 Ma, consistent with cooling of this crustal segment down to subsolidus conditions of ca. 450°C. A pegmatitic granite dyke, with lobate contacts, previously dated at ca. 1005 Ma (Turlin et al., 2017 ) is interpreted to intrude the paragneisses at a temperature of ca. 650°C close to the wet‐solidus. These data document slow cooling at a rate of 2–6°C/Ma for the middle crust of this part of the Grenville hinterland marked by protracted suprasolidus conditions for at least 70 Ma. It supports the definition of the Grenville Orogen as a large, hot, long‐duration orogen. 相似文献