全文获取类型
收费全文 | 530篇 |
免费 | 30篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 33篇 |
地球物理 | 145篇 |
地质学 | 164篇 |
海洋学 | 43篇 |
天文学 | 112篇 |
综合类 | 4篇 |
自然地理 | 56篇 |
出版年
2022年 | 2篇 |
2021年 | 9篇 |
2020年 | 5篇 |
2019年 | 11篇 |
2018年 | 17篇 |
2017年 | 7篇 |
2016年 | 19篇 |
2015年 | 11篇 |
2014年 | 10篇 |
2013年 | 48篇 |
2012年 | 28篇 |
2011年 | 32篇 |
2010年 | 21篇 |
2009年 | 25篇 |
2008年 | 20篇 |
2007年 | 18篇 |
2006年 | 29篇 |
2005年 | 32篇 |
2004年 | 26篇 |
2003年 | 21篇 |
2002年 | 27篇 |
2001年 | 12篇 |
2000年 | 13篇 |
1999年 | 9篇 |
1998年 | 4篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1991年 | 3篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1980年 | 4篇 |
1979年 | 8篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 5篇 |
1975年 | 1篇 |
1973年 | 2篇 |
1970年 | 1篇 |
1966年 | 1篇 |
1963年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有564条查询结果,搜索用时 31 毫秒
51.
Thermochronometric constraints on the tectonic evolution of the Serifos detachment, Aegean Sea, Greece 总被引:1,自引:0,他引:1
Stephanie Brichau Stuart Thomson Uwe Ring 《International Journal of Earth Sciences》2010,99(2):379-393
We constrain the timing and kinematics of the Serifos detachment in the southwestern Cyclades, Greece, using low-temperature
thermochronometry. Fission-track dating shows that the Serifos detachment was active between ~13 and 6 Ma and that the Serifos
granodiorite in its footwall intruded at or before ~12–11 Ma into the extensional shear zone and initially cooled very rapidly
at rates >180°C per million year. The mylonite zone at the top of the granodiorite and mylonitic structures in its country
rocks record a consistent top-SSW shear sense in the ductile crust. In the brittle regime top-NNE shear-sense indicators occur
as well. Conjugate top-SSW and top-NNE high-angle normal faults are the youngest deformational features and cut across the
detachment. Age–distance relationships for the fission-track data display a relatively flat pattern. We discuss a model advocating
initial top-SSW movement on the Serifos detachment before and during emplacement of the granodiorite. Updoming of the detachment
during exhumation and cooling caused subsequent bivergent extension in the brittle crust. 相似文献
52.
Stephanie Hänsel 《Theoretical and Applied Climatology》2014,118(1-2):223-235
Changes in the persistence of dry and wet periods are of particular interest for many sectors, as long-term deviations from normal precipitation strongly affect the water availability. Here, an indicator is introduced to explore variability and trends of long-lasting dry and wet periods by using decile based thresholds. The test of three different thresholds for ending those periods revealed only slight influences of the chosen threshold on the spatiotemporal pattern and trends. The methodology of the deciles indicator is illustrated and studied exemplarily for a spatially highly resolved data set for Saxony, Germany within 1901–2010. Within that region decile wet and dry periods, respectively, occur approximately four times within 10 years, last on average 11 months and cover on average more than 35 % of the stations. Several years to decades long periods with particularly frequent and/or long decile dry or wet periods were identified. The computed trends strongly depend upon the analysis period, as frequency, duration and spatial coverage of decile periods show strong variations up to multi-decadal time scales. Nonetheless, there is some indication that dry period coverage increased within the 20th century, while wet period coverage decreased. However, in the most recent decades the long-term trends reversed. 相似文献
53.
Manuela Magliocchetti Steve J. Maddox Ed Hawkins John A. Peacock Joss Bland-Hawthorn Terry Bridges Russell Cannon Shaun Cole Matthew Colless Chris Collins Warrick Couch Gavin Dalton Roberto de Propris Simon P. Driver George Efstathiou Richard S. Ellis Carlos S. Frenk Karl Glazebrook Carole A. Jackson Bryn Jones Ofer Lahav Ian Lewis Stuart Lumsden Peder Norberg Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2004,350(4):1485-1494
54.
The current study focuses on understanding key factors controlling geochemical export in eight diverse coastal watersheds at seasonal and annual time scales. Geochemical, atmospheric and hydrologic data across a range of hydro‐climatic regimes and varying land uses were investigated and relationships analysed. A hyperbolic dilution model was fitted for each watershed system to evaluate discharge–concentration relationships. Nitrate concentration effects were observed in watersheds exposed to high atmospheric deposition rates as well as agricultural watersheds, whereas urban watersheds showed nitrate dilution effects. Dilution patterns were observed for calcium, magnesium and sulfate for almost all watersheds. Seasonal loads for almost all constituents were noted to be mainly driven by hydrologic seasonality, but are also dependent on inputs (atmospheric deposition and land use sources). Understanding the primary controls on hydro‐chemical interactions is critical for developing and refining predictive water quality models, especially in coastal watersheds where sensitive downstream ecosystems act as receiving waters for upstream pollutant loads. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
55.
Monostatic reverberation measurements were collected in shallow water, over a coarse gravel and cobble bottom, 100 m deep, off the coast of Nova Scotia. Data were collected at frequencies of 21, 28, and 36 kHz using linear FM pulses of 2-kHz bandwidth and 0.160-s duration. An anchored, high-frequency active sonar array deployed at a depth of 42 m was used to collect the data. The reverberation measurements were compared with estimates computed with the NUWC generic sonar model (GSM). The data were reasonably well modeled for times greater than 0.2 s after pulse transmission by neglecting surface reverberation and using Lambert's rule for bottom backscattering with a scattering coefficient of -27 dB, independent of frequency. At all three frequencies, the data and model show a peak approximately 0.9 s after pulse transmission. This peak results from a focusing effect that the downward-refracting sound-speed profile has on the interaction of the rays with the bottom 相似文献
56.
The 2dF Galaxy Redshift Survey: the bJ -band galaxy luminosity function and survey selection function
Peder Norberg Shaun Cole Carlton M. Baugh Carlos S. Frenk Ivan Baldry Joss Bland-Hawthorn Terry Bridges Russell Cannon Matthew Colless Chris Collins Warrick Couch Nicholas J. G. Cross Gavin Dalton Roberto De Propris Simon P. Driver George Efstathiou Richard S. Ellis Karl Glazebrook Carole Jackson Ofer Lahav Ian Lewis Stuart Lumsden Steve Maddox Darren Madgwick John A. Peacock Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,336(3):907-931
57.
Peder Norberg Carlton M. Baugh Ed Hawkins Steve Maddox John A. Peacock Shaun Cole Carlos S. Frenk Joss Bland-Hawthorn Terry Bridges Russell Cannon Matthew Colless Chris Collins Warrick Couch Gavin Dalton Roberto De Propris Simon P. Driver George Efstathiou Richard S. Ellis Karl Glazebrook Carole Jackson Ofer Lahav Ian Lewis Stuart Lumsden Darren Madgwick Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2001,328(1):64-70
We investigate the dependence of the strength of galaxy clustering on intrinsic luminosity using the Anglo-Australian two degree field galaxy redshift survey (2dFGRS). The 2dFGRS is over an order of magnitude larger than previous redshift surveys used to address this issue. We measure the projected two-point correlation function of galaxies in a series of volume-limited samples. The projected correlation function is free from any distortion of the clustering pattern induced by peculiar motions and is well described by a power law in pair separation over the range . The clustering of galaxies in real space is well-fitted by a correlation length and power-law slope . The clustering amplitude increases slowly with absolute magnitude for galaxies fainter than M *, but rises more strongly at higher luminosities. At low luminosities, our results agree with measurements from the Southern Sky Redshift Survey 2 by Benoist et al. However, we find a weaker dependence of clustering strength on luminosity at the highest luminosities. The correlation function amplitude increases by a factor of 4.0 between and −22.5, and the most luminous galaxies are 3.0 times more strongly clustered than L * galaxies. The power-law slope of the correlation function shows remarkably little variation for samples spanning a factor of 20 in luminosity. Our measurements are in very good agreement with the predictions of the hierarchical galaxy formation models of Benson et al. 相似文献
58.
Surface-structure-controlled sectoral zoning of the rare earth elements in fluorite from Long Lake, New York, and Bingham, New Mexico, USA 总被引:1,自引:0,他引:1
Stephanie BoszeJohn Rakovan 《Geochimica et cosmochimica acta》2002,66(6):997-1009
The concentration and distribution of rare earth elements (REE) in sectorally zoned fluorite crystals from Long Lake, New York, and the Hansonburg Mining District, Bingham, New Mexico, have been studied using cathodoluminescence and synchrotron X-ray fluorescence microanalysis (SXRFMA). In cubo-octahedral samples from Long Lake, New York, Ce, Nd, Gd, Dy, Ho, Er, and Tm are preferentially partitioned into the |111| sector relative to the |100| sector. Partition coefficients (Kd = concentration in |111| sector/concentration in |100| sector) range between 3.5 for Ce, to 1.4 for Tm, with a general decrease in Kd as elements deviated from the ionic radius of Ca2+, for which REE substitute in fluorite. Diffusion of the REE has occurred, as evidenced by gradual changes in composition over distances of 0.2 to 0.3 mm at sector boundaries.In Bingham samples, three different partition coefficients were determined for Dy: Kd|100|/|111| = 2.83, Kd |100|/|110| = 1.77, and Kd |110|/|111| = 1.60. These are mean Kd values for a 95% confidence interval. In another sample from the same deposit, Dy, Er, and Gd were found to be preferentially incorporated into the |100| sector relative to the |210| sector with average Kd |100|/|210| of 3.1, 2.4, and 2.9, respectively. In a third sample, Nd was found to be preferentially incorporated into the |110| sector relative to the |321| sector with an average Kd |110|/|321| value of 2.3.Compositional heterogeneities in a given sector (concentric zoning) have been resolved using SXRFMA but are significantly less than the concentration difference across sector boundaries. Often fluorite exists in a wide variety of morphologies, as is the case in the Hansonburg Mining District of Bingham. We suggest caution when using the REE as petrogenetic indicators because fluorite trace element chemistry can vary greatly among crystals within a deposit depending on the internal morphology of a particular crystal. 相似文献
59.
It has been argued by Jacobson, Liberati and Mattingly that synchrotron radiation from the Crab Nebula imposes a stringent constraint on any modification of the dispersion relations of the electron that might be induced by quantum gravity. We supplement their analysis by deriving the spectrum of synchrotron radiation from the coupling of an electrically charged particle to an external magnetic fields in the presence of quantum-gravity effects of the general form (E/MQG). We find that the synchrotron constraint from the Crab Nebula practically excludes 1.74 for MQGmP=1.2×1019 GeV. On the other hand, this analysis does not constrain any modification of the dispersion relation of the photon that might be induced by quantum gravity. We point out that such quantum-gravity effects need not obey the equivalence principle, a point exemplified by the Liouville-string D-particle model of space–time foam. This model suggests a linear modification of the dispersion relation for the photon, but not for the electron, and hence is compatible with known constraints from the Crab Nebula and elsewhere. 相似文献
60.
Ian Lewis Michael Balogh Roberto De Propris Warrick Couch Richard Bower Alison Offer Joss Bland-Hawthorn Ivan K. Baldry Carlton Baugh Terry Bridges Russell Cannon Shaun Cole Matthew Colless Chris Collins Nicholas Cross Gavin Dalton Simon P. Driver George Efstathiou Richard S. Ellis Carlos S. Frenk Karl Glazebrook Edward Hawkins Carole Jackson Ofer Lahav Stuart Lumsden Steve Maddox Darren Madgwick Peder Norberg John A. Peacock Will Percival Bruce A. Peterson Will Sutherland Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,334(3):673-683