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141.
Michele Cantiello 《Astrophysics and Space Science》2012,341(1):187-194
The analysis of deep imaging data of bright elliptical galaxies is capable of providing fundamental information on the stellar content and the distance of the target, via the Surface Brightness Fluctuation method (SBF hereafter). Here, I present the study of the properties of two ellipticals in the Virgo cluster, NGC 4621 and NGC 4374, based on deep BVR imaging data obtained with the FORS2 camera at the VLT. 相似文献
142.
Roberto Armellin Pierluigi Di Lizia Michele Lavagna 《Celestial Mechanics and Dynamical Astronomy》2012,112(3):331-352
A method for high-order treatment of uncertainties in preliminary orbit determination is presented. The observations consist
in three couples of topocentric right ascensions and declinations at three observation epochs. The goal of preliminary orbit
determination is to compute a trajectory that fits with the observations in two-body dynamics. The uncertainties of the observations
are usually mapped to the phase space only when additional observations are available and a least squares fitting problem
is set up. A method based on Taylor differential algebra for the analytical treatment of observation uncertainties is implemented.
Taylor differential algebra allows for the efficient computation of the arbitrary order Taylor expansion of a sufficiently
continuous multivariate function. This enables the mapping of the uncertainties from the observation space to the phase space
as high-order multivariate Taylor polynomials. These maps can then be propagated forward in time to predict the observable
set at successive epochs. This method can be suitably used to recover newly discovered objects when a scarce number of measurements
is available. Simulated topocentric observations of asteroids on realistic orbits are used to assess the performances of the
method. 相似文献
143.
Growing environmental concern is promoting the necessity of additional ceramic tests. The use of unknown materials with potential
contamination conditions requires further studies to demonstrate that the piece encapsulates the pollutant and that during
its firing it does not produce the emission of harmful volatile elements. The objective of this work was to perform both tests
in a ceramic paste made with slip-casting wastes and electro-plating residues. The leaching methods for determining the encapsulation
of potential harmful elements were performed following the TCLP, EP-Tox norm. Having precise chemical analysis of both crude
and fired brick, the problem of emissions losses during the firing can be solved by the gain/loss techniques used in geological
studies. In particular, the Isocon method that permits a quick visualization of the lost elements is useful. Once the volatile
elements were determined, their amount was calculated considering a constant element and the chemical concentrations normalized
by the loss of ignition, or using the crude/fired brick ratio densities. The leaching tests indicate that the ceramic brick
does not produce harmful leachates according to Argentinean specifications. The leachates of B and Ca are high. Ca does not
seem to be a problem while the B content is beyond the permitted limits. During the firing, volatilized elements are Ag, Br,
Cl, F, Hg, S, Se, and H2O. The loss of Ag, Br, and Se are negligible. For F and Cl the potential emission rate is very low (100 mg/kg) while in the
case of S, the 2,600 mg/kg rate is high. However, extrapolated emission rates at the chimney assuming an air-to-brick ratio
of 2.5 N m3/kg, are approximately 1,040 mg/N m3 for S and 40 mg/N m3 for F and Cl, falling inside environmentally acceptable values. The geochemical procedures proved to be useful tools to assess
the element mobilization during firing of ceramic wares and in the analyzed case, the results indicate that the paste is environmentally
acceptable. 相似文献
144.
Simon?Delattre Etienne?BalanEmail author Michele?Lazzeri Marc?Blanchard Maxime?Guillaumet Olivier?Beyssac Eiken?Haussühl Bj?rn?Winkler Ekhard?K.?H.?Salje Georges?Calas 《Physics and Chemistry of Minerals》2012,39(2):93-102
Vibrational properties of diaspore, α-AlOOH, have been re-investigated using room-temperature single-crystal Raman spectroscopy
and low-temperature powder infrared (IR) transmission spectroscopy. First-principles harmonic calculations based on density
functional theory provide a convincing assignment of the major Raman peaks and infrared absorption bands. The large width
of the Raman band related to OH stretching modes is ascribed to mode–mode anharmonic coupling due to medium-strength H-bonding.
Additional broadening in the powder IR spectrum arises from depolarization effects in powder particles. The temperature dependence
of the IR spectrum provides a further insight into the anharmonic properties of diaspore. Based on their frequency and temperature
behavior, narrow absorption features at ~2,000 cm−1 and anti-resonance at ~2,966 cm−1 in the IR spectrum are interpreted as overtones of fundamental bending bands. 相似文献
145.
Melted snow volume control in the snowmelt runoff model using a snow water equivalent statistically based model 总被引:1,自引:0,他引:1
Snowmelt is an important component of the river discharge in mountain environments. In the past 40 years, the snowmelt dynamics has been mostly evaluated using degree‐day‐based models like the snowmelt runoff model (SRM). This model has no control on the volume of the melting snow, even if SRM includes as data input the snow‐covered area. This lack explains why the application of SRM may lead to inaccurate snowmelt volume estimations, even if the discharge volumes are accurately reproduced. Here we introduce in SRM the control on the melted snow volume and consider it in the determination of SRM parameters. The total snow volume, accumulated at the end of winter season, is evaluated by a snow water equivalent statistically based model, SWE‐SEM, and used as an estimate of the melting snow during the summer season. The benefit derived from the introduction of the control on the melting snow volume was investigated in the Mallero basin (northern Italy) for the 2003 and 2004 snow melting seasons. The analysis compares the model's results adopting different parameter sets, both considering and ignoring the control on the melting snow volume. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
146.
Sediment load plays a major role in the morphological evolution of rivers.Therefore,the analysis of the sediment load interaction with hydraulic structures is of main importance in order to enhance the preservation of fish habitats and river morphological characteristics.The present study analyzes the scour mechanisms downstream of a block ramp in live bed conditions,when the sediment supplied by the approaching flow is balanced by the sediment transported out of the scour hole.Experiments were performed in a model flume and the effect of the approaching sediment concentration on the scour geometry was analyzed.It was observed that the scour features depend deeply on the approaching sediment concentration and four main profile configurations were distinguished.The experimental data were analyzed and empirical relationships were developed in order to evaluate the depth and length of a scour hole,the dune height and the distance of the transversal section of maximum dune height from the ramp toe for different hydraulic and geometric conditions.It was also proved that the dynamic equilibrium shape of a scour hole does not depend on the sediment load time history. 相似文献
147.
A two-phase model for fast geomorphic shallow flows 总被引:1,自引:0,他引:1
The paper introduces a 2D shallow water model based on a two-phase formulation for the analysis of fast geomorphic transients occurring in the context of river morphodynamics.Mass and momentum conservation principles are separately imposed for both phases.The model naturally accounts for non-equilibrium solid transport,since neither instantaneous adaptation hypothesis nor any lag equation is employed to represent sediment dynamics.The hyperbolic character of the proposed model is shown to be preserved independently on the flow conditions.Results from numerical simulations of both 1D and 2D test-cases are compared with literature experimental data and with available numerical solutions. 相似文献
148.
In the present paper, an analytical expression of the Green’s function of linearized Saint-Venant equations (LSVEs) for shallow
water waves is provided and applied to analyse the propagation of a perturbation superposed to a uniform flow. Independently
of the kinematic character of the base flow, i.e., subcritical or supercritical uniform flow, the effects of a non-uniform vertical velocity profile and a non-constant resistance
coefficient are accounted for. The use of the Darcy-Weisbach friction law allows a unified treatment of both laminar and turbulent
conditions. The influence on the wave evolution of the wall roughness and the fluid viscosity are finally discussed, showing
that in turbulent regime the assumption of constant friction coefficient may lead to an underestimation of both amplification
and damping factors on the wave fronts, especially at low Reynolds numbers. This conclusion has to be accounted for, particularly
in describing hyper-concentrated suspensions or other kinds of Newtonian mixtures, for which the high values of the kinematic
viscosity may lead to relatively low Reynolds numbers. 相似文献
149.
150.
Schaffelke B Carleton J Skuza M Zagorskis I Furnas MJ 《Marine pollution bulletin》2012,65(4-9):249-260
Coastal and inshore areas of the Great Barrier Reef lagoon receive substantial amounts of material from adjacent developed catchments, which can affect the ecological integrity of coral reefs and other inshore ecosystems. A 5-year water quality monitoring dataset provides a 'base range' of water quality conditions for the inshore GBR lagoon and illustrates the considerable temporal and spatial variability in this system. Typical at many sites were high turbidity levels and elevated chlorophyll a and phosphorus concentrations, especially close to river mouths. Water quality variability was mainly driven by seasonal processes such as river floods and sporadic wind-driven resuspension as well as by regional differences such as land use. Extreme events, such as floods, caused large and sustained increases in water quality variables. Given the highly variable climate in the GBR region, long-term monitoring of marine water quality will be essential to detect future changes due to improved catchment management. 相似文献