全文获取类型
收费全文 | 360篇 |
免费 | 14篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 17篇 |
大气科学 | 37篇 |
地球物理 | 74篇 |
地质学 | 148篇 |
海洋学 | 15篇 |
天文学 | 56篇 |
综合类 | 3篇 |
自然地理 | 26篇 |
出版年
2022年 | 3篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 8篇 |
2016年 | 7篇 |
2015年 | 6篇 |
2014年 | 12篇 |
2013年 | 16篇 |
2012年 | 12篇 |
2011年 | 15篇 |
2010年 | 21篇 |
2009年 | 14篇 |
2008年 | 11篇 |
2007年 | 9篇 |
2006年 | 12篇 |
2005年 | 7篇 |
2004年 | 13篇 |
2003年 | 13篇 |
2002年 | 8篇 |
2001年 | 9篇 |
2000年 | 3篇 |
1999年 | 9篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1975年 | 9篇 |
1974年 | 3篇 |
1972年 | 4篇 |
1968年 | 5篇 |
1967年 | 2篇 |
1966年 | 3篇 |
1964年 | 2篇 |
1937年 | 2篇 |
排序方式: 共有376条查询结果,搜索用时 0 毫秒
371.
372.
Steffen Wolters Manfred Zeiler Friederike Bungenstock 《International Journal of Earth Sciences》2010,99(8):1707-1719
A vibrocore from the sea floor of the southern North Sea provides a ~1,500-year record of early Holocene vegetation history
and mire development in a landscape now 33 m below sea-level. Pollen, plant macrofossil and geochemical analyses of an AMS
14C dated sand–peat–marine mud sequence document the paludification on Pleistocene sands ~10,700 cal BP, the subsequent development
of eutraphentic carr vegetation and the gradual inundation by the transgressing sea ~9,350 cal BP. Pinus–Corylus woodland prevailed on terrestrial grounds after hazel had immigrated ~10,700 cal BP. Salix dominated the carr vegetation throughout 1,300 years of peat formation, because Alnus did not spread in the Borkum Riffgrund area until 9,300 BP. Brackish reed vegetation with Phragmites established after inundation and siliciclastic marine sediments were being deposited. This article also examines the detection
and suitability of key horizons indicative of marine influence. XRF-Scanning provides the most detailed results in the briefest
possible time to pinpoint spectra best suitable for AMS 14C dating of classical key horizons such as start of peat formation and transgressive contact. The combined application of
botanical and geochemical methods allows determining new key horizons indicative of marine influence, namely the earliest
marine inundation and the onset of sea-level influence on coastal ground water level. 相似文献
373.
Lutz Nasdala Dieter Grambole Manfred Wildner Alexander M. Gigler Thomas Hainschwang Alexander M. Zaitsev Jeffrey W. Harris Judith Milledge Daniel J. Schulze Wolfgang Hofmeister Walter A. Balmer 《Contributions to Mineralogy and Petrology》2013,165(5):843-861
We have undertaken a study of the common green or orange-brown spots at the surface of rough diamond specimens, which are caused by alpha particles emanating from radioactive sources outside the diamond. Richly coloured haloes represent elevated levels of structural damage, indicated by strong broadening of the main Raman band of diamond, intense strain birefringence, and up-doming of spots due to their extensive volume expansion. Green radio-colouration was analogously generated through the irradiation of diamond with 8.8 MeV helium ions. The generation of readily visible radio-colouration was observed after irradiating diamond with ≥1015 He ions per cm2. The accumulation of such a high number of alpha particles requires irradiation of the diamond from a radioactive source over long periods of time, presumably hundreds of millions of years in many cases. In the samples irradiated with He ions, amorphisation was observed in volume areas where the defect density exceeded 5 × 10?3 Å?3 (or 0.03 dpa; displacements per target atom). In contrast, graphitisation as a direct result of the ion irradiation was not observed. The green colouration transformed to brown at moderate annealing temperatures (here 450 °C). The colour transformation is associated with only partial recovery of the radiation damage. The colour change is mainly due to the destruction of the GR1 centre, explained by trapping of vacancies at A defects to form the H3 centre. An activation energy of ~2.4 ± 0.2 eV was determined for the GR1 reduction. The H3 centre, in turn, causes intense yellowish-green photoluminescence under ultraviolet illumination. Radio-colouration and associated H3 photoluminescence are due to point defects created by the ions irradiated, whereas lattice ionisation is of minor importance. This is concluded from the depth distribution of the colouration and the photoluminescence intensity (which corresponds to the defect density but not the ionisation distribution pattern). The effect of the implanted He ions themselves on the colour and photoluminescence seems to be negligible, as radio-colouration and H3 emission were analogously produced through irradiation of diamond with C ions. The photoluminescence emission becomes observable at extremely low defect densities on the order of 10?6 Å?3 (or 0.000006 dpa) and is suppressed at moderate defect densities of ~5 × 10?4 Å?3 (or ~0.003 dpa). Intensely brown-coloured diamond hence does not show the H3 emission anymore. Anneals up to 1,600 °C has reduced considerably irradiation damage and radio-colouration, but the structural reconstitution of the diamond (and its de-colouration) was still incomplete. 相似文献
374.
375.
Green clinopyroxenes and associated phases in a potassium-rich lava from the Leucite Hills,Wyoming 总被引:1,自引:0,他引:1
Green, salitic pyroxenes occur as megacrysts and as cores in diopsidic pyroxene phenocrysts and microphenocrysts in a wyomingite lava from Hatcher Mesa, Leucite Hills, Wyoming. Al-rich phlogopite (16–21% Al2O3), apatite, Fe-Ti-oxide, Mg-rich olivine (Fo93) and orthopyroxene (En61) also occur as megacrysts or as inclusions in diopside phenocrysts. All of these phases are found in ultramafic xenoliths in the host lava, and petrographic and chemical evidence is presented that the megacrysts originate by the disaggregation of the xenoliths. It is concluded that the latter are accidental fragments of the wall rocks traversed by the wyomingite magma and it is suggested that the clinopyroxene-rich xenoliths, from which the green pyroxenes are derived, formed in the upper mantle as a result of local metasomatism or by crystallization from magmas of unknown composition during an earlier igneous event. The precise role of the clinopyroxene-rich xenoliths (which also contain apatite, Fe-Ti-oxide and amphibole) in the genesis of the Leucite Hills magmas cannot be elucidated on the basis of the available data, but it is unlikely that they represent the source material from which these magmas are derived. 相似文献
376.
Gert Finger Frank Eisenhauer Reinhard Genzel Christopher Mandla Ian Baker Domingo Alvarez Antonio Amorim Wolfgang Brandner Christophe Dupuy Casey Deen Derek Ives Leander Mehrgan Manfred Meyer Karin Perraut Guy Perrin Jörg Stegmeier Christian Straubmeier Harald J. Weller Vincent Isgar 《Astronomische Nachrichten》2023,344(8-9):e20230069
Near-infrared adaptive optics as well as fringe tracking for coherent beam combination in optical interferometry require the development of high-speed sensors. Because of the high speed, a large analog bandwidth is required. The short exposure times result in small signal levels which require noiseless detection. Both requirements cannot be met by state-of-the-art conventional CMOS technology of near-infrared arrays as has been attempted previously. A total of five near-infrared SAPHIRA 320 × 256 pixel HgCdTe e−APD arrays have been deployed in the wavefront sensors and in the fringe tracker of the VLTI instrument GRAVITY. The current limiting magnitude for coherent exposures with GRAVITY is mk = 19, which is made possible with ADP technology. New avalanche photo-diode array (APD) developments since GRAVITY include the extension of the spectral sensitivity to the wavelength range from 0.8 to 2.5 μm. After GRAVITY a larger format array with 512 × 512 pixels has been developed for both AO applications at the ELT and for long integration times. Since dark currents of <10−3 e−/s have been demonstrated with 1Kx1K e−APD arrays and 2Kx2K e−APD arrays have already been developed, the possibilities and adaptations of e−APD technology to provide noiseless large-format science-grade arrays for long integration times are also discussed. 相似文献