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1.
Mark A. Shields David K. WoolfEric P.M. Grist Sandy A. KerrA.C. Jackson Robert E. HarrisMichael C. Bell Robert BeharieAndrew Want Emmanuel OsalusiStuart W. Gibb Jonathan Side 《Ocean & Coastal Management》2011,54(1):2-9
Many countries now recognise the need for mitigation of climate change induced by human activities and have incorporated renewable energy resources within their energy policy. There are extensive resources of renewable energy within the marine environment and increasing interest in extracting energy from locations with either large tidal range, rapid flow with and without wave interaction, or large wave resources. However, the ecological implications of altering the hydrodynamics of the marine environment are poorly understood. Ecological data for areas targeted for marine renewable developments are often limited, not least because of the considerable challenges to sampling in high energy environments. In order to predict the scale and nature of ecological implications there is a need for greater understanding of the distribution and extent of the renewable energy resource and in turn, of how marine renewable energy installations (MREIs) may alter energy in the environment. Regional ecological implications of a MREI need to be considered against the greater and global ecological threat of climate change. Finally, it is recommended that the identification of species and biotopes susceptible to the removal of hydrokinetic energy could be a suitable strategy for understanding how a MREI may alter flow conditions. 相似文献
2.
Virtually all of the economic Ni–Cu–(platinum group element (PGE)) mineralization in the central part of the Cape Smith Belt
of New Québec is hosted by thick olivine cumulate units in the Katinniq Member of the Raglan Formation at the base of the
1.9 Ga Chukotat Group. These units transgress underlying gabbros and pelitic metasediments, forming 50–200-m deep and 300–1,000-m
wide V-shaped embayments and have been interpreted on the basis of surface geology, deep diamond core drilling, and magnetic
inversion models to represent the remnants of one or more large, long (at least 20 km, possibly ≥50 km), sinuous, komatiitic
basalt lava channels that formed by thermomechanical erosion of their substrates. We have used a mathematical model to test
these hypotheses regarding komatiitic lava emplacement and erosion by lava. Our modeling predicts that an initially 10-m thick
komatiitic basalt flow should have flowed turbulently near the vent and should have thermomechanically eroded unconsolidated
pelitic sediment during emplacement to reach the observed degree of contamination of ≤10% at distances of ~30–60 km downstream
from the source. Furthermore, our models predict that, at these distances downstream, a fully inflated 100-m thick komatiitic
basalt flow would have had thermal erosion rates over consolidated gabbroic substrate of ~0.7–1.5 m/day, requiring ~70–140 days
to incise a 100-m deep channel, depending on the initial temperature of the lava, the paleoslope, and the initial temperature
and solidus temperature of the gabbro. These erosion rates would have been associated with volumetric flow rates of >105–106 m3/s and eruption volumes of >103–104 km3. Although these flow rates are orders of magnitude larger than those of most modern terrestrial basaltic flows, they are
of the same order as those estimated for the largest terrestrial flood basalt flows and with those inferred for some of the
largest extraterrestrial flows. Our predicted flow volumes are also of the same order as those of the largest terrestrial
flood basalt units, consistent with the great thickness and widespread distribution of the Chukotat Group. Our modeling of
thermomechanical erosion of gabbro by komatiitic basalt results in negligible contamination (<1%), and geochemical studies
show that the spatially and petrogenetically related Chukotat basalts are uncontaminated, suggesting that the observed enrichments
in U–Th–Light Rare Earth Elements (REE) > Middle REE–Heavy REE > Nb–Ta–Ti represent contamination by underlying Povungnituk
semipelites. This result is consistent with present models for the genesis of the Ni–Cu–(PGE) mineralization in the Raglan
Formation that involve thermomechanical erosion of unconsolidated, sulfidic semipelitic sediments, and decoupling of the miscible
silicate and immiscible sulfide components. 相似文献
3.
C.A. Mériaux J.A. Mansour L.N. Moresi R.C. Kerr D.A. May 《Physics of the Earth and Planetary Interiors》2011,184(1-2):63-79
The rise of an initially horizontal, buoyant cylinder of fluid through a denser fluid at low Reynolds number is used to look at the ascent of strongly tilted mantle plumes through the mantle. Such ascents are characterized by (1) the growth of instabilities and (2) the development of a thermal wake downstream. Three-dimensional numerical experiments were carried out to examine these features. An hybrid particle-in-cell finite element method was used to look at the rise of non-diffusing cylinders and, a standard finite element method was used to look at the diffusing case. First the experiments show that the timescale of the fastest growing instability vary with the Rayleigh number and the viscosity ratio. In particular the growth rate decreases as the Rayleigh number decreases, in agreement with our analysis of the laboratory experiments of Kerr et al. (2008). Second the experiments show that the length of the thermal wake increases with the Rayleigh number but the change in viscosity has almost no influence on the wake length. Applied to strongly tilted mantle plumes we conclude that such plumes cannot be unstable given the plume timescales. We also discuss the application of this conclusion to weakly tilted plumes. Besides, this study allows to predict that mantle plumes are unlikely to have developed a significant thermal wake by the time they reach the surface. Finally, the resolution that is required to allow for the growth of mantle plume tails by combined diffusion and thermal entrainment is shown to represent a challenge for the large scale mantle convection simulations. 相似文献
4.
Diana Prado Garzón Christiano G.M. Brum Ezequiel Echer Néstor Aponte Michael P. Sulzer Sixto A. González Robert B. Kerr Lara Waldrop 《Journal of Atmospheric and Solar》2011,73(11-12):1568-1574
We analyze the data obtained using the Arecibo incoherent scatter radar to examine the response of the topside ionosphere to a moderate geomagnetic storm that occurred during the period March 7–11, 2008. During this time period a magnetic storm with a non-monotonic main phase decrease in the Dst index occurred. The recovery phase also exhibited a secondary Dst decrease. During the initial phase of the storm, Te and Ti increased coincident with the arrival of the solar wind. The main phase registered an increase in proton concentration proportional to Ne while temperatures reached the lowest values. Variations in O+ concentration were not significant but a reduction in helium fraction was observed. Soon after the peak of the storm, the transition height between the topside ionosphere and the protonosphere, where H+ ions dominate composition, was lower than would be expected during quiet conditions and this behavior lasted for approximately 12 h. 相似文献
5.
6.
7.
We evaluated the prevalence of partial migration, coexisting resident and migratory life history types, within six white perch
(Morone americana) populations in sub-estuaries (Upper Bay, and Potomac, Choptank, Nanticoke, James, and York Rivers) of the Chesapeake Bay.
Otolith stable isotope (δ18O) values were used to resolve fish habitat use along an estuarine salinity gradient and define resident or migratory behavior.
The majority of adults within Upper Bay and Potomac River populations were resident, whereas individuals from the Choptank,
Nanticoke, James, and York Rivers were predominantly migratory. Beyond population differences, large interannual variability
in life history types was observed, likely due to differences in estuarine conditions that influence growth rate of individuals
(e.g., temperature, zooplankton density). Because we observed partial migration in all study populations, we suggest that
this trait is characteristic of this species, permitting plastic responses to variation in the estuarine environment. 相似文献
8.
Douglas S. Hall Gregory W. Henry Dietmar Böhme Peter A. Brooks Sandy Chang Ales Dolzan George L. Fortier Robert E. Fried Russell M. Genet Bruce S. Grim James Hannon Darrel B. Hoff Kevin Krisciunas Howard J. Landis Howard P. Louth Larry P. Lovell Paul Nielsen Bobby E. Powell Harry D. Powell Don Pray Thomas R. Renner Charles W. Rogers Stephen Shervais Douglas M. Slauson Samuel Slote Harold J. Stelzer Arthur J. Stokes Jack C. Troeger Louis C. Turner Norman F. Wasson Kenneth W. Zeigler 《Journal of Astrophysics and Astronomy》1991,12(4):281-287
We present photoelectric photometry of λ And never before published, obtained between February 1982 and December 1990 at 29
different observatories. Then we combine it with all other photometry available to us (previously published, contained in
the I.A.U. Commission 27 Archives, and obtained with the Vanderbilt 16-inch automatic telescope but not yet published), to
yield a 14.8-year data base. Analysis reveals a long-term cycle in mean brightness, with a full range of 0m.15 and a period of 11.4 ± 0.4 years. Because most of our new photometry was concentrated in the 1983-84 observing season,
we analyze that one well-defined light curve with a two-spot model. Spot A keeps a 0m.04 amplitude throughout four rotation cycles whereas the amplitude of spot B diminishes from 0m.09 down almost to 0m.03. The spot rotation periods were 55d.9 ± 0d.6 and 520d.8 ± 1d.0, respectively. 相似文献
9.
10.
F. M. Kerr A. Gouveia R. W. Lee P. K. Patel O. Renner S. J. Rose H. A. Scott J. S. Wark 《Astrophysics and Space Science》2005,298(1-2):171-176
An astrophysically relevant experiment is compared to the output of a multidimensional radiation transfer code in which populations
and radiation are self-consistently treated. Experimental Al Ly α spectra obtained with a very high-resolution spectrometer
are presented as quantitative evidence of dot plasma non-planar expansion. Analysis of these spectra using the code is performed,
in particular examining the effects of velocity gradients in directions other than that of the primary expansion. These calculations
are found to be in good agreement with the experimental results. Usage of the Ly α doublet as a planarity diagnostic is discussed. 相似文献