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31.
32.
T. V. Berezhnykh O. Yu. Marchenko N. V. Abasov V. I. Mordvinov 《Geography and Natural Resources》2012,33(3):223-229
We examine the formation patterns of the low-water periods 1976?C1982 and 1996?C2011 for the Selenga river. One of the immediate reasons for the low-water periods under consideration is the attenuation of the circulation in the zone of convergence of monsoon flows and mid-latitude flows over Mongolia and North China. Unlike the low-water periods of the preceding decades, a decrease in precipitation amounts during the current low-water period is taking place concurrently with large-scale climatic changes. 相似文献
33.
Leningrad State University. Translated from Astrofizika, Vol. 30, No. 1, pp. 7–14, January–February, 1989. 相似文献
34.
Evolution of the Earth's principal axes and moments of inertia: the canonical form of solution 总被引:4,自引:0,他引:4
Harmonic coefficients of the 2nd degree are separated into the invariant quantitative (the 2nd-degree variance) and the qualitative
(the standardized harmonic coefficients) characteristics of the behavior of the potential V
2(t). On this basis the evolution of the Earth's dynamical figure is described as a solution of the time-dependent eigenvalues–eigenvectors
problem in the canonical form. Such a canonical quadratic form is defined only by temporal variations of the harmonic coefficients
and always remains finite, even within an infinite time interval. An additional condition for the correction or the determination
of temporal variations of the 2nd degree is obtained. Temporal variations of the fully normalized sectorial harmonic coefficients
are estimated in addition to ˙Cˉ
20, ˙Cˉ
21, and ˙Sˉ
21 of the EGM96 gravity model. In addition, a non-linear hyperbolic model for Cˉ
2m
(t), Sˉ
2m
(t) is constructed. The trigonometric form of the hyperbolic model leads to the consideration of the potential V
2(ψ) instead of V
2(t) within the closed interval −π/2≤ψ≤+π/2. Thus, it is possible to evaluate the global trend of V
2(t), the Earth's principal axes and the differences of the moments of inertia within the whole infinite time interval.
Received: 25 September 1998 / Accepted: 28 June 2000 相似文献
35.
In the northern Barents Sea Opening (BSO) the K1 tidal energy is predominant in the diurnal tidal frequency band, suggesting the generation of a topographic wave with the K1 tidal frequency. Tidal energy of the K1 component becomes strong where bottom topography undulates in the BSO and the scale of the undulation is close to the wavelength of the K1 wave. An analytical model is developed to investigate the energy enhancement mechanism of the tidally induced topographic wave due to a resonance between tidal current, a topographic wave and periodic topography. The wave excited by the resonance is identified as a resonant double Kelvin wave (DKW) and the significant K1 energy in the BSO could be due to the excitation of the resonant DKW. 相似文献
36.
The impact of tidal wave on a permeable shore consisting of porous material results in groundwater table lying above the average sea level. This effect, stemming from the nonlinearity of the process of seawater flow in the soil, is referred to as pumping effect. 相似文献
37.
The formation of fast ice in the costal zone of freezing seas (immobile ice) is considered on the basis of a specially developed
thermodynamic model that takes into account the energy exchange in the atmospheric boundary layer and the salinification of
the water layer under the ice. The conditions at which the wind forced onshore motion of the ice under the influence of the
wind stress at the ice’s surface is possible are studied using the example of the Baidaratskaya Guba in the Kara Sea. 相似文献
38.
Kazuyuki Saito Sergei Marchenko Vladimir Romanovsky Amy Hendricks Nancy Bigelow Kenji Yoshikawa John Walsh 《Boreas: An International Journal of Quaternary Research》2014,43(3):733-749
A high‐resolution map of potential frozen ground distribution in NE Asia (90–150°E, 25–60°N) at the period of the Last Permafrost Maximum (LPM, c. 21 000 years ago) was dually reconstructed by means of a statistical classification using air freezing and thawing indices and a topographical downscaling using a digital relief model (ETOPO1). Background LPM climate data were derived from global climate model simulations of the Paleoclimate Model Intercomparison Project, Phase II (PMIP2). The reconstructed LPM map shows the southward shift of the southern limit of climate‐driven permafrost by 400–1500 km, with the greatest advance in the western sector (90–110°E), encompassing an area from central Siberia to most of the Altai area. The advance of environmentally conditional permafrost and seasonally frozen ground was greatest in the eastern sector (110–150°E), with an average shift of about 450 km. The descent of the lower limit of LPM alpine permafrost was in the range of 400–800 m. A comparison of the reconstructed map with published literature shows that this method, simplistically constructed yet effectively recognizing seasonality, continentality and topography, captures local features better than more elaborate methods. The sensitivity examination of a constant atmospheric lapse rate shows that altitudes of 2000–5000 m a.s.l. were most sensitive, though with only a limited effect on overall LPM distribution. 相似文献
39.
The estimation of the Earth’s gravitational potential energy E was obtained for different density distributions and rests
on the expression E = − (Wmin + ΔW) derived from the conventional relationship for E. The first component Wmin expresses minimum amount of the work W and the second component ΔW represents a deviation from Wmin interpreted in terms of Dirichlet’s integral applied on the internal potential. Relationships between the internal potential
and E were developed for continuous and piecewise continuous density distributions. The global 3D density model inside an
ellipsoid of revolution was chosen as a combined solution of the 3D continuous distribution and the reference PREM radial
piecewise continuous profile. All the estimates of E were obtained for the spherical Earth since the estimated (from error
propagation rule) accuracy σE of the energy E is at least two orders greater than the ellipsoidal reduction and the contribution of lateral density inhomogeneities
of the 3D global density model. The energy E contained in the 2nd degree Stokes coefficients was determined. A good agreement
between E = EGauss derived from Gaussian distribution and other E, in particular for E = EPREM based on the PREM piecewise continuous density model and E-estimates derived from simplest Legendre-Laplace, Roche, Bullard
and Gauss models separated into core and mantle only, suggests the Gaussian distribution as a basic radial model when information
about density jumps is absent or incomplete. 相似文献
40.
Jef Vandenberghe Hugh M. French Aldar Gorbunov Sergei Marchenko Andrey A. Velichko Huijun Jin Zhijiu Cui Tingjun Zhang Xudong Wan 《Boreas: An International Journal of Quaternary Research》2014,43(3):652-666
This paper accompanies a map that shows the extent of permafrost in the Northern Hemisphere between 25 and 17 thousand years ago. The map is based upon existing archival data, common throughout the Northern Hemisphere, that include ice‐wedge pseudomorphs, sand wedges and large cryoturbations. Where possible, a distinction is made between areas with continuous permafrost and areas where permafrost is either spatially discontinuous or sporadic. The associated mean annual palaeo‐temperatures that are inferred on the basis of present‐day analogues increase understanding of the possible changes in permafrost extent that might accompany current global warming trends. Areas with relict permafrost and areas that were formerly exposed due to lower sea level (submarine permafrost) are also mapped. Mapping is mostly limited to lowland regions (areas approximately <1000 m a.s.l.). Striking features that appear from the map are (i) the narrow permafrost zone in North America, which contrasts with the broader LPM permafrost zone in Eurasia (that may be related to different snow thickness or vegetation cover), (ii) the zonal extent of former LPM permafrost (that may reflect sea‐ice distribution), which contrasts with the present‐day pattern of permafrost extent (especially in Eurasia) and (iii) the relatively narrow zones of LPM discontinuous permafrost (that may indicate strong temperature gradients). 相似文献