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11.
F. A. Lopes G. Michard M. Poulin A. Roué F. Prévot D. Jézéquel E. Viollier 《Aquatic Geochemistry》2010,16(4):587-610
A reactive transport model was developed to describe seasonal variations of biogeochemical and physical processes in Lake
Aydat. The model includes physical processes such as vertical mixing, sedimentation and advection related to inflows into
the lake and biogeochemical conversion processes in the water column and in the sediment surface layer. The reactions described
in the model include primary redox reactions such as primary production, aerobic and anaerobic respiration, methanogenesis
and secondary reactions established between oxidants and reducers produced by the primary reactions. After adjusting various
kinetic constants, the model reasonably reproduced the main features of seasonal variations of dissolved oxygen and nitrate
depth profiles and pH. The reactive transport model was also used to quantify the relative importance of different biogeochemical
pathways. For instance, ferrous denitrification seems to play an important role when stratification is increasing. 相似文献
12.
Impacts of tectonic and orbital forcing on East African climate: a comparison based on global climate model simulations 总被引:1,自引:1,他引:0
Frank Kaspar Kerstin Prömmel Ulrich Cubasch 《International Journal of Earth Sciences》2010,99(7):1677-1686
A global atmosphere–ocean model has been forced with topographic and orbital scenarios in order to evaluate the relative role
of both factors for the past climate of East Africa. Forcing the model with a significantly reduced topography in Eastern
and Southern Africa leads to a distinct increase in moisture transport from the Indian Ocean into the eastern part of the
continent and increased precipitation in Eastern Africa. Simulations with step-wise reduced height show that this climate
change occurs continuously with the change in topography, i.e., an abrupt change of local climatic features with a critical
height is not found. Simulations of the last interglacial (at 125,000 years before present, i.e., the Eemian interglacial)
and the last glacial inception (at 115,000 years before present) are used as examples for the role of orbital-induced changes
in insolation. Here, changes in meridional temperature gradients lead to modifications in moisture transport of similar order
of magnitude, but with different spatial and seasonal structure. For the Eemian interglacial, a distinct increase in summer
moisture transport from the Atlantic deep into the continent at around 20°N is simulated. 相似文献
13.
Extreme waves caused by tsunamis and storm surges can lead to soil failures in the near‐shore region, which may have severe impact on coastal environments and communities. Multiphase flows in deformable porous media involve several coupled processes and multiple time scales, which are challenging for numerical simulations. The objective of this study is to investigate the roles of the various processes and their interactions in multiphase flows in unsaturated soils under external wave loading, via theoretical time‐scale analysis and numerical simulations. A coupled geomechanics–multiphase flow model based on conservation laws is used. Theoretical analysis based on coupled and decoupled models demonstrates that transient and steady‐state responses are governed by pore pressure diffusion and saturation front propagation, respectively, and that the two processes are essentially decoupled. Numerical simulations suggest that the compressibility of the pore fluids and the deformation of the soil skeleton are important when the transient responses of the media are of concern, while the steady‐state responses are not sensitive to these factors. The responses obtained from the fully coupled numerical simulations are explained by a simplified time‐scale analysis based on coupled and decoupled models. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
14.
Arnaud M. Aubourg E. Bareyre P. Br';ehin S. Caridroit R. de Kat J. Dispau G. Djidi K. Gros M. Lachièze-Rey M. Laigneau Y. Laurent B. Lesquoy E. Lavocat Ph. Magneville C. Mazeau B. Milsztajn A. Moscoso L. Pasquaud J. Paul B. Perrin P. Petibon J. Piret Y. Queinnec F. Rich J. Spiro M. de Trogoff J. Vigroux L. Zylberajch S. Ansari R. Cavalier F. Moniez M. Beaulieu J. P. Ferlet R. Grison Ph. Vidal-Madjar A. Adrianzyk G. Berger J. P. Burnage R. Delclite J. C. Kohler D. Magnan R. Richaud A. Guibert J. Moreau O. Tajahmady F. Baranne A. Maurice E. Prévôt L. Gry C. 《Experimental Astronomy》1994,4(3-4):279-296
Conclusion To summarize, the readout and the control system of the CCD mosaic camera are running since December 1991 at the La Silla Observatory (ESO). The overall performance of the camera has been good. About 12000 pictures (data and flat-fields) have been successfully registered up to now. We will report in the near future preliminary scientific results of the EROS experiment. 相似文献
15.
We present Strömgrenuvby photometric observations and a series of radial velocities obtained with the Coravel scanner for the 11th magnitude star catalogued in the Guide Star Catalogue as GSC 0114401023. This star was serendipitously identified on UV frames taken with the Very-Wide-Field-Camera aboard Spacelab-1. Radial velocities show the star to be binary and we have determined accurate orbital elements. Photometric data and orbital elements are consistent with the system being a previously-unrecognized eclipsing binary, with period = 33.8766 days and eccentricity = 0.262.Based on observations collected at the Observatoire de Haute Provence (OHP), CNRS, Saint-Michel l'Observatoire, France, and at the European Southern Observatory (ESO), La Silla, Chile. 相似文献
16.
Witold Prószyński 《Journal of Geodesy》2013,87(1):89-99
The paper presents an approach to internal reliability analysis of observation systems known as Errors-in-Variables (EIV) models with parameters estimated by the method of least squares. Such problems are routinely treated by total least squares adjustment, or orthogonal regression. To create a suitable environment for derivations in the analysis, a general nonlinear form of such EIV models is assumed, based on a traditional adjustment method of condition equations with unknowns, also known as the Gauss–Helmert model. However, in order to apply the method of reliability analysis based on the approach to response assessment in systems with correlated observations, presented in the earlier work of this author, it was necessary to confine the considerations to a quasi-linear form of the Gauss–Helmert model, representing quasi-linear EIV models. This made it possible to obtain a linear disturbance/response relationship needed in that approach. Several specific cases of quasi-linear EIV models are discussed. The derived formulas are consistent with those already functioning for standard least squares adjustment problems. The analysis shows that, as could be expected, the average level of response-based reliability for such EIV models under investigation is lower than that for the corresponding standard linear models. For EIV models with homoscedastic and uncorrelated observations, the relationship between the average reliability indices for the independent and the dependent variables is formulated for multiple regression and coordinate transformations. Numerical examples for these two applications are provided to illustrate this analysis. 相似文献
17.
Michel G. Houlé Sonia Préfontaine Anthony D. Fowler Harold L. Gibson 《Bulletin of Volcanology》2009,71(8):881-901
Spinifex-textured sills (i.e., veins) characterized by komatiitic magmas that have intruded their own volcanic-piles have
long been recognized. For instance, in the early 1970s, Pyke and coworkers, in their classic work at Pyke Hill in Munro Township,
noted that not all spinifex-bearing ultramafic rocks formed as lava flows, rather some were clearly emplaced as small dikes
and sills. Several hypotheses have been proposed to explain spinifex-textured sills: intrusion into a cold host, filter pressing,
or drainage of residual liquid. However, these do not satisfactorily explain the phenomenon. Field and petrographic observations
at Pyke Hill and Serpentine Mountain demonstrate that spinifex-bearing komatiite sills and dikes were emplaced during channel
inflation processes when new magma was intruded into a cooler, semi-consolidated but permeable cumulate material. Komatiitic
liquids were intruded into the olivine cumulate rocks near the boundary between the spinifex and the cumulate zones of well-organized
to organized komatiite flows. Spinifex-textured sills are generally tabular in morphology, stacked one above another, with
curviplanar contacts sub-parallel to stratigraphy. Some sills exhibit complex digitated apophyses. Thinner sills typically
have a random olivine spinifex texture similar, though generally composed of coarser crystals, to that of komatiite lava flows.
Thicker sills exhibit more complex organization of their constituent crystals characterized by zones of random olivine spinifex,
overlying zones of organized coarse spinifex crystals similar to those found in lava flows. They have striking coarse dendritic
spinifex zones composed of very large olivine crystals, up to several centimetres long and up to 1 cm wide that are not observed
in lava flows. Typically, at the sill margins, the cumulate material of the host flow is composed of euhedral to subhedral
olivine crystals that are larger than those distal to the contact. Many of these margin-crystals have either concentric overgrowth
shells or dendritic olivine overgrowths that grew from the cumulate-sill contact toward the sill interior. The dendrites grew
on pre-existing olivine cumulate at the contact in response to a sharp temperature gradient imposed by the intrusion of hot
material, whereas the concentric overgrowths formed as new melt percolated into the unconsolidated groundmass of the host-flow
cumulate material. Spinifex-textured sills and dikes occur in well-organized to organized flows that are interpreted to have
formed by “breakouts” above and peripheral to lava pathways (channels/conduits) as a result of inflation that accompanied
voluminous komatiitic eruptions responsible for the construction and channelization of komatiitic flow fields. The spinifex-textured
dikes and sills represent komatiitic lava that was originally emplaced into the channel roof during periods of episodic inflation
that resulted in lava breakouts and was subsequently trapped in the “roof rocks” during periods of channel deflation. Accordingly,
the occurrence of spinifex-textured sills and dikes may indicate proximity to, and aid in the identification and delineation
of lava channel-ways that could potentially host Ni–Cu–(PGE) mineralization within komatiitic lava flow-fields. 相似文献
18.
19.
This study investigates the statistical correlation between the power input into the magnetosphere due to reconnection and the subsequent dissipation of this energy in the magnetosphere as measured by the UT parameter (Perreault and Akasofu, 1978). It is found that of the three expressions for this energy input PW, PK (Gonzalez and Gonzalez, 1984) and ε (Perreault and Akasofu, 1975; Kan et al.,1980), PW yields the highest correlation with the energy consumption of the magnetosphere. 相似文献
20.
Summary In this paper an attempt for predicting smoke concentration levels in Athens for spring and autumn is presented. The regression models are based on equations relating wind speed and smoke values. It is found that both of them become more effective if corrections related to wind speed categories are applied to the equations. In this way good prediction is achieved for the next 24 hours.With 4 Figures 相似文献