全文获取类型
收费全文 | 731篇 |
免费 | 55篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 21篇 |
大气科学 | 51篇 |
地球物理 | 247篇 |
地质学 | 294篇 |
海洋学 | 34篇 |
天文学 | 96篇 |
综合类 | 9篇 |
自然地理 | 39篇 |
出版年
2022年 | 7篇 |
2021年 | 12篇 |
2020年 | 13篇 |
2019年 | 12篇 |
2018年 | 46篇 |
2017年 | 44篇 |
2016年 | 58篇 |
2015年 | 54篇 |
2014年 | 48篇 |
2013年 | 47篇 |
2012年 | 29篇 |
2011年 | 35篇 |
2010年 | 33篇 |
2009年 | 35篇 |
2008年 | 33篇 |
2007年 | 37篇 |
2006年 | 29篇 |
2005年 | 14篇 |
2004年 | 16篇 |
2003年 | 10篇 |
2002年 | 10篇 |
2001年 | 12篇 |
2000年 | 16篇 |
1999年 | 5篇 |
1998年 | 13篇 |
1997年 | 9篇 |
1996年 | 11篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 7篇 |
1971年 | 2篇 |
1969年 | 2篇 |
排序方式: 共有791条查询结果,搜索用时 984 毫秒
711.
Yu. N. Korenkov Carl W. Cable Vernon F. Cormier Vassily Levin Jacek A. Majorowicz Yehuda Bock Waclaw M. Zuberek Teng-fong Wong William L. Power Gary A. Robbins Piotr Raczka Krzysztof E. Haman Katarzyna Chałasinska-Macukow Ryszard Balcer Henryk Piwkowski 《Pure and Applied Geophysics》1991,137(3):309-336
712.
Sławomir Maj 《Physics and Chemistry of Minerals》1991,17(8):711-715
A relationship between the energy gap (E G) and the density (ρ) over mean atomic weight (〈A〉) ratio for Fe-poor oxide and silicate minerals is derived from simple properties of their free atom-components. Theoretical considerations are based on the Lorentz electron theory of solids. The eigenfrequency ν 0 of elementary electron oscillators, in energy units h ν 0, is identified with the energy gap of a solid. The numerical relation is of the form $$(\langle U_0 \rangle ^2 - E_G^2 )\frac{{\langle A\rangle }}{\rho } = \frac{4}{3}\pi \hbar ^2 \frac{{e^2 }}{m}N = 276.79 eV^2 cm^3 /mol$$ where 〈U 0〉 is the average first ionization potential (per free atom), ? is crossed Planck's constant, e is the electron charge, m is the electron rest mass, and N is Avogadro's number. For several geophysically interesting oxide and silicate minerals which are in general composed of four different elements (O, Si, Mg and Al), we obtain from laboratory data that the mean value of $$\left\langle {[\langle U_0 \rangle ^2 - (E_G^{lab} )^2 ]\frac{{\langle A\rangle }}{\rho }} \right\rangle \approx 248.2 \pm 20.9eV^2 cm^3 /mol.$$ . 相似文献
713.
Stanisław Kasperczuk 《Celestial Mechanics and Dynamical Astronomy》1995,63(3-4):245-253
The reduced Henon-Heiles system is investigated as a Hamiltonian dynamical system obtained by applying the normalization of the HamiltonianH=1/2(p
1
2
+p
2
2
+q
1
2
+q
2
2
)+1/3q
1
3
–q
1
q
2
2
to fourth-degree terms. The related equations of motion are bi-Hamiltonian and possess the Lie-Poisson structure. Each Lie-Poisson structure possesses an associated Casimir function. When reduced to level sets of these functions, the equations of motion take various symplectic forms. The various reductions give different coordinate representations of the solutions. These coordinate representations are used to seek the simplest representation of the solutions. 相似文献
714.
715.
Wavelet analysis for processing of ocean surface wave records 总被引:2,自引:0,他引:2
Stanis
aw R. Massel 《Ocean Engineering》2001,28(8):165
Wavelet analysis is a relatively new technique and in the recent years enormous interest in application of wavelets has been observed. This modern technique is particularly suitable for non-stationary processes as in contrast to the Fourier transform, (FT), the wavelet transform (WT) allows exceptional localization, both in time and frequency domains. The wavelet transform has been successfully implemented in signal and image processing, ordinary and partial differential equation theory, numerical analysis, communication theory and other fields. On the other hand, the application of the WT to ocean engineering and oceanography is rare. In this paper the WTs capability to give a full time–frequency representation of the wave signals is demonstrated. The processing of the time series of the non-stationary deep water waves, waves breaking at the tropical coral reefs and mechanically generated waves in the wave flume demonstrates the ability of the wavelet transform technique to detect a complex variability of these signals in the time–frequency domain. Various spectral representations resulting from the wavelet transform are discussed and their application for wave signals is shown. 相似文献
716.
A unique, five-year long data set of ferry-mounted ADCP measurements in the Marsdiep inlet, the Netherlands, obtained between 1998 and 2003, is presented. A least-squares harmonic analysis was applied to the water transport, (depth-averaged) currents, and water level to study the contribution of the tides. With 144 tidal constituents, maximally 98% of the variance in the water transport and streamwise currents is explained by the tides, whereas for the stream-normal currents this is maximally 50%. The most important constituent is the semi-diurnal M2 constituent, which is modulated by the second-largest S2 constituent (about 27% of M2). Compound and overtides, such as 2MS2, 2MN2, M4, and M6, are important in the inlet. Due to interaction of M2 with its quarter-diurnal overtide M4, the tidal asymmetry in the southern two thirds of the inlet is flood dominant. The amplitudes of all non-astronomic constituents are largest during spring tides, strongly distorting the water level and velocity curves. The M2 water transport is 40° ahead in phase compared to the M2 water level, reflecting the progressive character of the tidal wave in the inlet. The currents are strongly rectilinear and they are sheared vertically and horizontally, with the highest currents at the surface above the deepest part of the inlet. During spring tides, near-surface currents can be as large as 1.8 m s− 1. Due to the relative importance of inertia compared to friction, the M2 currents near the centre (surface) lag maximal 20° (3°) in phase with the currents near the sides (bottom). The tidal-mean currents are directed into the basin in the shallower channel to the south and out of the basin in the deeper channel to the north. 相似文献
717.
An examination of the effect of assumptions in the interpretation of the Venera wind data is made as a rebuttal to the suggestion by A.T. Young that the 140 m/sec Venera 8 horizontal wind at 45 km may be either spurious or anomalous. The Venera measurements of wind speed along with the Mariner measurements of a lower region of strong turbulence are evidence for a wide band of variable high-speed retrograde horizontal winds which girdle Venus at the equator. In the prevalent interpretation of the Mariner 10 uv photographs, the region of the top of the visible cloud is characterized by variable high-speed retrograde horizontal winds which orbit Venus with an average period of 4 Earth days, and by many features indicating vertical convection. This interpretation, together with the possibility of atmospheric corotation due to frictional coupling, suggests that the Venera-Mariner band of winds at 45 km extends well beyond the top of the visible cloud, and that the upper region of strong turbulence detected by the Mariners may result in part from vertical convection currents carried along by high-speed horizontal winds. In an alternate interpretation of the Mariner 10 uv photographs Young suggests that the predominant motions may be traveling wavelike disturbances with a 4-day period rather than bulk motion of the atmosphere. For this case the upper region of strong turbulence is interpreted as due mostly to vertical wind shear resulting from a rapid decrease in wind speed within a relatively short distance above the Venera-Mariner band of high-speed winds. 相似文献
718.
Witold Szczuciński Przemysław Niedzielski Lidia Kozak Marcin Frankowski Anetta Zioła Stanisław Lorenc 《Environmental Geology》2007,53(2):253-264
Study on contamination of tsunami sediments deposited on 26 December 2004 conducted shortly after the tsunami in coastal zone
of Thailand revealed elevated contents of salts in water-soluble and some heavy metals and arsenic in bioavailable fractions
(Szczuciński et al. in Env Geol 49:321–331, 2005). Few months later rainy season started and effected in total rainfall of over 3,300 mm. This paper presents results of survey
repeated 1 year after the tsunami. To assess the effects of rainy season on mobilization of previously determined potential
contaminants, the same locations were sampled again and analysed with the same methods. The tsunami deposit layer was well
preserved but in many locations the sediments were coarser than just after tsunami due to washing out of finer fractions.
The water-soluble salts contents were strongly reduced after the rainy season. However, the concentrations of acid leachable
heavy metals and metalloids were still elevated in comparison to reference sample from an area not impacted by tsunami. It
is possible that the metals and metalloids are successively moved to more bioavailable fraction from forms which were more
resistant to mobilization. 相似文献
719.
Artur Poręba Wacław M. Zuberek Jolanta Nogaj-Chachaj Andrzej Kotyrba Sławomir Siwek 《Acta Geophysica》2007,55(4):640-651
The aim of the research was to examine subsurface soil layers with the use of the Ground Penetrating Radar (GPR) method. Neolithic
archaeological post in Karmanowice was examined. On the basis of earlier geophysical researches and archaeological premises,
eight measurement profiles had been chosen. Ground Penetrating Radar system with antenna of 500 MHz frequency was applied.
The measurements were made with 30 and 60 ns time windows. The results were shown as the GPR sections. The analysis of the
obtained results allowed us to outline anomalies connected with the appearance of archaeological objects in subsurface soil
layers. The border between the anthropogenically changed upper layer and undisturbed loess was established, and the sections
of slope wash layers were designated. Anomalies were confirmed by digging and test drillings. Additionally, 2D resistivity
imaging method was used for verification of specific anthropogenic anomalies. 相似文献
720.
The authors present a method for estimation of interval velocities using the downward continuation of the wavefield to perform
layer-stripping migration velocity analysis. The generalized, phase-shift migration MG(F-K) in wavenumber-frequency domain
was used for fulltime downward extrapolation of the wavefield. Such downward depth extrapolation accounts for strong changes
of velocity in lateral and vertical directions and helps in correct positioning of the wavefield image in complex structures.
Determination of velocity is the recursive process which means that the wavefield on depth level z
n−1 (n = 0, 1, ...) is an input data-set for determination of velocity on level z
n
. The velocity ν [x, z
n
− z
n−1] can be thus treated as interval velocity in Δz
n
= z
n
− z
n−1 step. This method was tested on synthetic Marmousi data-set and showed satisfactory results for complex, inhomogeneous media. 相似文献