全文获取类型
收费全文 | 213篇 |
免费 | 6篇 |
专业分类
测绘学 | 13篇 |
大气科学 | 11篇 |
地球物理 | 55篇 |
地质学 | 33篇 |
海洋学 | 11篇 |
天文学 | 76篇 |
自然地理 | 20篇 |
出版年
2022年 | 1篇 |
2020年 | 1篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2015年 | 5篇 |
2014年 | 5篇 |
2013年 | 5篇 |
2012年 | 11篇 |
2011年 | 5篇 |
2010年 | 8篇 |
2009年 | 12篇 |
2008年 | 12篇 |
2007年 | 8篇 |
2006年 | 9篇 |
2005年 | 3篇 |
2004年 | 10篇 |
2003年 | 10篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 7篇 |
1997年 | 2篇 |
1996年 | 6篇 |
1995年 | 10篇 |
1994年 | 3篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 6篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1969年 | 2篇 |
1961年 | 2篇 |
排序方式: 共有219条查询结果,搜索用时 0 毫秒
61.
62.
Brent B. Wolfe Thomas W. D. Edwards Ramon Aravena Steven L. Forman Barry G. Warner Andrei A. Velichko Glen M. MacDonald 《Quaternary Research》2000,53(3):319
Lake-water oxygen-isotope histories for three lakes in northern Russia, derived from the cellulose oxygen-isotope stratigraphies of sediment cores, provide the basis for preliminary reconstruction of Holocene paleohydrology in two regions along the boreal treeline. Deconvolution of shifting precipitation δ18O from secondary evaporative isotopic enrichment is aided by knowledge of the distribution of isotopes in modern precipitation, the isotopic composition of paleo-waters preserved in frozen peat deposits, as well as other supporting paleoclimatic information. These data indicate that during the early Holocene, when the boreal treeline advanced to the current arctic coastline, conditions in the lower Yenisey River region were moist compared to the present, whereas greater aridity prevailed to the east near the lower Lena River. This longitudinal moisture gradient is consistent with the suggestion that oceanic forcing (increased sea-surface temperatures in the Nordic Seas and reduced sea-ice cover) was a major contributor to the development of a more maritime climate in western Eurasia, in addition to increased summer insolation. East of the Taimyr Peninsula, large tracts of the continental shelf exposed by glacial sea-level drawdown may have suppressed maritime climatic influence in what are now coastal areas. In contrast, during the late Holocene the two regions have apparently experienced coherent shifts in effective moisture. The similarity of the records may primarily reflect reduced North Atlantic influence in the Nordic Seas and southward retreat of coastline in eastern Siberia, coupled with declining summer insolation. 相似文献
63.
J. R. Murray † B. Warner D. T. Wickramasinghe 《Monthly notices of the Royal Astronomical Society》2000,315(4):707-712
We investigate the role of the eccentric disc resonance in systems with mass ratios q ≳1/4, and demonstrate the effects that changes in the mass flux from the secondary star have upon the disc radius and structure. The addition of material with low specific angular momentum to the outer edge of a disc restricts that disc radially. Should the mass flux from the secondary be reduced, it is possible for the disc in a system with mass ratio as large as 1/3 to expand to the 3:1 eccentric inner Lindblad resonance and for superhumps to be excited. 相似文献
64.
J. S. Young J. E. Baldwin R. C. Boysen C. A. Haniff D. Pearson J. Rogers D. St-Jacques † P. J. Warner D. M. A. Wilson 《Monthly notices of the Royal Astronomical Society》2000,318(2):381-386
We report the direct detection of cyclic diameter variations in the Mira variable χ Cygni. Interferometric observations made between 1997 July and 1999 September, using the Cambridge Optical Aperture Synthesis Telescope (COAST) and the William Herschel Telescope (WHT), indicate periodic changes in the apparent angular diameter at a wavelength of 905 nm, with amplitude 45 per cent of the smallest value. The star appears largest at minimum light. Measurements made at a wavelength of 1.3 μm over the same period suggest much smaller size changes. This behaviour is consistent with a model in which most of the apparent diameter variation at 905 nm is caused by a large increase in the opacity of the outer atmospheric layers (which is mostly owing to titanium oxide) near minimum light, rather than by physical motions of the photosphere. The 1.3-μm waveband is relatively uncontaminated by TiO, and so much smaller size changes would be expected in this band. The latest non-linear pulsational models predict maximum physical size close to maximum light, and increases in opacity near minimum light that are too small to reproduce the diameter variation seen at 905 nm. This suggests either that the phase-dependence of the model pulsation is incorrect, or that the opacities in the models are underestimated. Future interferometric monitoring in uncontaminated near-infrared wavebands should resolve this question. 相似文献
65.
66.
Brian Warner 《Astrophysics and Space Science》1995,228(1-2):283-297
Suggestions and examples are given for photometric and spectrographic programs with 0.5 - 1.0m telescopes, both at poor and at good sites. The importance is stressed of coordination between observers at sites spread over a region or around the world. As an example of the latter, the Whole Earth Telescope group and their successful observing programs are described. 相似文献
67.
68.
Brian Warner 《Astrophysics and Space Science》1986,118(1-2):271-277
Rapid coherent and quasi-periodic oscillations in the optical and X-ray fluxes of cataclysmic variable stars are described.Invited paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. 相似文献
69.
Short time-scale photometric properties of eight faint cataclysmic variable (CV) stars are presented. Nova Carinae 1895 (RS Car) has a photometric modulation at 1.977 h that could be either an orbital or a superhump period. Nova Carinae 1948 (V365 Car) shows flickering, but any orbital modulation has a period in excess of 6 h. The nova-like variable and X-ray source V436 Car has an orbital modulation at P orb = 4.207 h , no detectable period near 2.67 h (which had previously given it a possible intermediate polar classification), and dwarf nova oscillations (DNOs) at ∼40 s. Nova Crucis 1936 (AP Cru) has a double-humped ellipsoidal modulation at P orb = 5.12 h and a stable modulation at 1837 s characteristic of an intermediate polar. Nova Chamaeleontis 1953 (RR Cha) is an eclipsing system with P orb = 3.362 h , but at times shows negative superhumps at 3.271 h and positive superhumps at 3.466 h. In addition it has a stable period at 1950 s, characteristic of an intermediate polar. BI Ori is a dwarf nova that we observed at quiescence and outburst without detecting any orbital modulation. CM Phe is a nova-like variable for which we confirm the value of P orb = 6.454 h found by Hoard, Wachter & Kim-Quijano . We have identified the remnant of Nova Sagittarii 1931 (V522 Sgr) with a flickering source ∼2.2 mag fainter than the previously proposed candidate (which we find to be non-variable). 相似文献
70.
Description of a very dense meteorite collection area in western Atacama: Insight into the long‐term composition of the meteorite flux to Earth 下载免费PDF全文
Aurore Hutzler Jérôme Gattacceca Pierre Rochette Régis Braucher Bertrand Carro Eric J. Christensen Cécile Cournede Matthieu Gounelle Nejia Laridhi Ouazaa Rodrigo Martinez Millarca Valenzuela Michael Warner Didier Bourles 《Meteoritics & planetary science》2016,51(3):468-482
We describe the geological, morphological, and climatic settings of two new meteorite collections from Atacama (Chile). The “El Médano collection” was recovered by systematic on‐foot search in El Médano and Caleta el Cobre dense collection areas and is composed of 213 meteorites before pairing, 142 after pairing. The “private collection” has been recovered by car by three private hunters and consists of 213 meteorites. Similar to other hot desert finds, and contrary to the falls and Antarctica finds, both collections show an overabundance of H chondrites. A recovery density can be calculated only for the El Médano collection and gives 251 and 168 meteorites larger than 10 g km?2, before and after pairing, respectively. It is by far the densest collection area described in hot deserts. The Atacama Desert is known to have been hyperarid for a long period of time and, based on cosmic‐ray exposure ages on the order of 1–10 Ma, to have been stable over a period of time of several million years. Such a high meteorite concentration might be explained invoking either a yet unclear concentration mechanism (possibly related to downslope creeping) or a previously underestimated meteorite flux in previous studies or an average terrestrial age over 2 Myr. This last hypothesis is supported by the high weathering grade of meteorites and by the common terrestrial fragmentation (with fragments scattered over a few meters) of recovered meteorites. 相似文献