全文获取类型
收费全文 | 333篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 13篇 |
地球物理 | 213篇 |
地质学 | 50篇 |
海洋学 | 2篇 |
天文学 | 55篇 |
自然地理 | 8篇 |
出版年
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 10篇 |
2017年 | 6篇 |
2016年 | 4篇 |
2015年 | 9篇 |
2014年 | 6篇 |
2013年 | 11篇 |
2012年 | 8篇 |
2011年 | 7篇 |
2010年 | 4篇 |
2009年 | 6篇 |
2007年 | 7篇 |
2006年 | 8篇 |
2004年 | 7篇 |
2003年 | 8篇 |
2002年 | 5篇 |
2001年 | 5篇 |
2000年 | 16篇 |
1999年 | 9篇 |
1998年 | 4篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1974年 | 7篇 |
1973年 | 5篇 |
1972年 | 5篇 |
1971年 | 7篇 |
1970年 | 7篇 |
1967年 | 3篇 |
1965年 | 5篇 |
1963年 | 3篇 |
1962年 | 3篇 |
1961年 | 3篇 |
1959年 | 3篇 |
排序方式: 共有345条查询结果,搜索用时 156 毫秒
101.
Detection and extraction of quasi-oscillatory dynamical modes from instrumental records of geophysical data became a useful tool in analyzing variability of observed phenomena reflected in complex, multivariate geophysical signals. Using the extension of the Monte Carlo singular system analysis (MC SSA), based on evaluating and testing regularity of dynamics of the SSA modes against the colored noise null hypothesis, we demonstrate detection of oscillatory modes with period of about 96 months in the long-term records of aa index as well as in the records of surface air temperature from several mid-latitude European locations and in the North Atlantic Oscillation index. 相似文献
102.
Dayside convection and auroral morphology during an interval of northward interplanetary magnetic field 总被引:1,自引:0,他引:1
We investigate the dayside auroral dynamics and ionospheric convection during an interval when the interplanetary magnetic field (IMF) had predominantly a positive Bz component (northward IMF) but varying By. Polar UVI observations of the Northern Hemisphere auroral emission indicate the existence of a region of luminosity near local noon at latitudes poleward of the dayside auroral oval, which we interpret as the ionospheric footprint of a high-latitude reconnection site. The large field-of-view afforded by the satellite-borne imager allows an unprecedented determination of the dynamics of this region, which has not previously been possible with ground-based observations. The location of the emission in latitude and magnetic local time varies in response to changes in the orientation of the IMF; the cusp MLT and the IMF By component are especially well correlated, the emission being located in the pre- or post-noon sectors for By < 0 nT or By > 0 nT, respectively. Simultaneous ground-based observations of the ionospheric plasma drift are provided by the CUTLASS Finland HF coherent radar. For an interval of IMF By 0 nT, these convection flow measurements suggest the presence of a clockwise-rotating lobe cell contained within the pre-noon dayside polar cap, with a flow reversal closely co-located with the high-latitude luminosity region. This pattern is largely consistent with recent theoretical predictions of the convection flow during northward IMF. We believe that this represents the first direct measurement of the convection flow at the imaged location of the footprint of the high-latitude reconnection site. 相似文献
103.
Milan M. irkovi Kenneth M. Lanzetta 《Monthly notices of the Royal Astronomical Society》2000,315(3):473-478
Recent measurements of the autocorrelation function of the Ly α clouds are analysed from the point of view of a simple model with strong clustering on the small scales. It is shown that this toy model reproduces fairly well the important linear relation between amplitude of the absorber autocorrelation function and neutral hydrogen column density. In addition, it predicts a correct evolutionary trend of correlation amplitudes. Some possible ramifications of these results are discussed. 相似文献
104.
Relationships between correlation lengths and integral scales for covariance models with more than two parameters 总被引:2,自引:2,他引:0
Dionissios T. Hristopulos Milan ?ukovi? 《Stochastic Environmental Research and Risk Assessment (SERRA)》2011,25(1):11-19
In geostatistical applications, the terms correlation length and range are often used interchangeably and refer to a characteristic
covariance length ξ that normalizes the lag distance in the variogram or the covariance model. We present equations that strictly
define the correlation length (r
c
) and integral range (ℓ
c
). We derive analytical expressions for r
c
and ℓ
c
of the Whittle–Matérn, fluctuation gradient curvature and rational quadratic covariances. For these covariances, we show
that the correlation length and integral range for a given model are not fully determined by ξ. We define non-trivial covariance
functions, and we formulate an ergodicity index based on ℓ
c
. We propose using the ergodicity index to compare coarse-grained measures corresponding to non-trivial covariance functions
with different parameters. Finally, we discuss potential applications of the proposed covariance models in stochastic subsurface
hydrology. 相似文献
105.
Jan Valenta Milan Brož Jiří Málek Bedřich Mlčoch Vladislav Rapprich Zuzana Skácelová the Doupov Working Group 《Acta Geophysica》2011,59(3):597-617
The Doupovské Hory Volcanic Complex (DHVC) is the best-preserved large volcanic suite of the Cenozoic intraplate volcanism
in the Bohemian Massif. However, many uncertainties remain in the geological setting of its basement. In summer 2008, two
seismic refraction profiles ran across this area to reveal the depth of the volcanic rocks and the underlying geological structure. 相似文献
106.
Martin Danišík Jaroslav Kadlec Christoph Glotzbach Anett Weisheit István Dunkl Milan Kohút Noreen J. Evans Monika Orvošová Brad J. McDonald 《Swiss Journal of Geoscience》2011,104(2):285-298
A combination of four thermochronometers [zircon fission track (ZFT), zircon (U–Th)/He (ZHe), apatite fission track (AFT)
and apatite (U–Th–[Sm])/He (AHe) dating methods] applied to a valley to ridge transect is used to resolve the issues of metamorphic,
exhumation and topographic evolution of the Nízke Tatry Mts. in the Western Carpathians. The ZFT ages of 132.1 ± 8.3, 155.1 ± 12.9,
146.8 ± 8.6 and 144.9 ± 11.0 Ma show that Variscan crystalline basement of the Nízke Tatry Mts. was heated to temperatures
>210°C during the Mesozoic and experienced a low-grade Alpine metamorphic overprint. ZHe and AFT ages, clustering at ~55–40
and ~45–40 Ma, respectively, revealed a rapid Eocene cooling event, documenting erosional and/or tectonic exhumation related
to the collapse of the Carpathian orogenic wedge. This is the first evidence that exhumation of crystalline cores in the Western
Carpathians took place in the Eocene and not in the Cretaceous as traditionally believed. Bimodal AFT length distributions,
Early Miocene AHe ages and thermal modelling results suggest that the samples were heated to temperatures of ~55–90°C during
Oligocene–Miocene times. This thermal event may be related either to the Oligocene/Miocene sedimentary burial, or Miocene
magmatic activity and increased heat flow. This finding supports the concept of thermal instability of the Carpathian crystalline
bodies during the post-Eocene period. 相似文献
107.
Aleksandar Sekuli Milan Kilibarda Dragutin Proti Melita Perec Tadi Branislav Bajat 《Theoretical and Applied Climatology》2020,140(1):101-114
High resolution gridded mean daily temperature datasets are valuable for research and applications in agronomy, meteorology, hydrology, ecology, and many other disciplines depending on weather or climate. The gridded datasets and the models used for their estimation are being constantly improved as there is always a need for more accurate datasets as well as for datasets with a higher spatial and temporal resolution. We developed a spatio-temporal regression kriging model for Croatia at 1 km spatial resolution by adapting the spatio-temporal regression kriging model developed for global land areas. A geometrical temperature trend, digital elevation model, and topographic wetness index were used as covariates together with measurements from the Croatian national meteorological network for the year 2008. This model performed better than the global model and previously developed models for Croatia, based on MODIS land surface temperature images. The R2 was 97.8% and RMSE was 1.2 °C for leave-one-out and 5-fold cross-validation. The proposed national model still has a high level of uncertainty at higher altitudes leaving it suitable for agricultural areas that are dominant in lower and medium altitudes. 相似文献
108.
109.
110.
Motivated by recent developments impacting our view of Fermi’s Paradox (the absence of extraterrestrials and their manifestations from our past light cone), we suggest a reassessment of the problem itself, as well as of strategies employed by the various SETI projects so far. The need for such reassessment is fueled not only by the failure of SETI thus far, but also by great advances recently made in astrophysics, astrobiology, computer science and future studies. As a result, we consider the effects of the observed metallicity and temperature gradients in the Milky Way galaxy on the spatial distribution of hypothetical advanced extraterrestrial intelligent communities. While properties of such communities and their sociological and technological preferences are, obviously, unknown at present, we assume that (1) they operate in agreement with the known laws of physics and (2) at some point in their history they typically become motivated by a meta-principle embodying the central role of information-processing; a prototype of the latter is the recently suggested Intelligence Principle of Steven J. Dick. There are specific conclusions of practical interest to astrobiological and SETI endeavors to be drawn from the coupling of these reasonable assumptions with the astrophysical and astrochemical structure of the spiral disk of our galaxy. In particular, we suggest that the outer regions of the Galactic disk are the most likely locations for advanced SETI targets, and that sophisticated intelligent communities will tend to migrate outward through the Galaxy as their capacities of information-processing increase, for both thermodynamical and astrochemical reasons. However, the outward movement is limited by the decrease in matter density in the outer Milky Way. This can also be regarded as a possible generalization of the galactic habitable zone (GHZ), concept currently being investigated in astrobiology. 相似文献