全文获取类型
收费全文 | 1034篇 |
免费 | 88篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 30篇 |
大气科学 | 88篇 |
地球物理 | 368篇 |
地质学 | 405篇 |
海洋学 | 68篇 |
天文学 | 104篇 |
综合类 | 20篇 |
自然地理 | 43篇 |
出版年
2024年 | 3篇 |
2022年 | 13篇 |
2021年 | 34篇 |
2020年 | 27篇 |
2019年 | 14篇 |
2018年 | 66篇 |
2017年 | 55篇 |
2016年 | 94篇 |
2015年 | 69篇 |
2014年 | 67篇 |
2013年 | 93篇 |
2012年 | 88篇 |
2011年 | 86篇 |
2010年 | 57篇 |
2009年 | 53篇 |
2008年 | 48篇 |
2007年 | 35篇 |
2006年 | 30篇 |
2005年 | 19篇 |
2004年 | 19篇 |
2003年 | 23篇 |
2002年 | 21篇 |
2001年 | 13篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 10篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 9篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1979年 | 2篇 |
1975年 | 3篇 |
1973年 | 1篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1964年 | 1篇 |
1958年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1126条查询结果,搜索用时 18 毫秒
991.
992.
Carmen Morales José F. Gómez Joaquín Trapero Stuart Bowyer Jerry Edelstein Eric Korpela 《Astrophysics and Space Science》1998,263(1-4):393-396
EURD (Espectrógrafo Ultravioleta extremo de Radiación Difusa), one of the instruments onboard the Spanish satellite MINISAT-01,
is a spectrograph specially designed to detect diffuse radiation, covering the wavelength range of 350-1100 Å, with a spectral
resolution of 6-8 Å. Its main scientific objectives are the detection of the emission line spectrum from the hot phase of
the interstellar medium and the spectrum of the upper atmospheric airglow. In order to reduce geocoronal noise, EURD always
observes in the anti-sun direction and only when the satellite is in orbital eclipse. After more than one year of observation
we have obtained the best spectrum of the upper atmospheric nightglow in this wavelength range, the spectrum of 15 OB stars
and the spectrum of the full Moon throughout the year.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
993.
Holocene explosive activity of Hudson Volcano, southern Andes 总被引:3,自引:1,他引:2
Fallout deposits in the vicinity of the southern Andean Hudson Volcano record at least 12 explosive Holocene eruptions, including
that of August 1991 which produced ≥4 km3 of pyroclastic material. Medial isopachs of compacted fallout deposits for two of the prehistoric Hudson eruptions, dated
at approximately 3600 and 6700 BP, enclose areas at least twice that of equivalent isopachs for both the 1991 Hudson and the
1932 Quizapu eruptions, the two largest in the Andes this century. However, lack of information for either the proximal or
distal tephra deposits from these two prehistoric eruptions of Hudson precludes accurate volume estimates. Andesitic pyroclastic
material produced by the 6700-BP event, including a 1 10-cm-thick layer of compacted tephra that constitutes a secondary
thickness maximum over 900 km to the south in Tierra del Fuego, was dispersed in a more southerly direction than that of the
1991 Hudson eruption. The products of the 6700-BP event consist of a large proportion of fine pumiceous ash and accretionary
lapilli, indicating a violent phreatomagmatic eruption. This eruption, which is considered to be the largest for Hudson and
possibly for any volcano in the southern Andes during the Holocene, may have created Hudson's 10-km-diameter summit caldera,
but the age of the caldera has not been dated independently.
Received: 31 January 1997 / Accepted: 29 October 1997 相似文献
994.
995.
996.
Unequivocal identification of irrigation return water through routine chemical analyses does not appear possible in tropical
volcanic islands. Several constituents, nevertheless, will suggest an agricultural source if they are present in large concentrations.
Nitrate is the most useful indicator; background concentrations are generally less than 2 ppm but return irrigation water
will commonly have concentrations of between 5 and 50 ppm. Sulfate appears to be the next most useful indicator. Calcium,
silica, and bicarbonate have also been reported to be significant. Where detailed studies have been made of agricultural water
balances, regional ground-water flow directions, and deep-well hydraulics, hydrochemistry can provide critical supporting
data for the identification of return irrigation water which could be a potential ground-water pollutant. 相似文献
997.
A periodic signal of high nominal significance (99.95%) is found in the light curve of OJ 287 in observations taken with the Prime Focus Camera Unit on the 2.5 m Isaac Newton Telescope on two nights in March–April 1987. No such periodicity is seen in the light curve of the simultaneously observed reference star. A null test involving observations taken with an identical method on the same telescope in January 1989 suggests strongly that alternative explanations such as instrumental stability or observational effects are not the cause. On the first night periodicity of different amplitudes is seen inB, V, R, andI. On the second night of monitoring the periodicity was still present in Gunn-Z but, had disappeared inB. This provides strong evidence that such periodicities are ephemeral phenomena.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献
998.
A two-zone model for the analysis of nuclear shell burning on accreting degenerate dwarfs is developed. The model consists of two thin shells in a plane-parallel approximation: an accreted hydrogen zone on the top and a pure helium zone on the bottom, generated by hydrogen burning. The core of the star is isothermal and does not evolve with time. The physical properties (density, temperature, and pressure) of the shells are obtained and an analysis of some correlations between them and the mass accretion rate, the chemical composition of the accreted mass, and the heat flux from core is done. The interaction between both shells is also analyzed.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献
999.
José M. Solanes Manuel Sanromà Eduard Salvador-Solé 《Astrophysics and Space Science》1990,171(1-2):9-12
We present preliminary results of the application to real data of a new method for studying the structure of groups and clusters of galaxies. The new method is able to produce reliable results for structures with a small number of galaxies. The 6 clusters whose number density and velocity dispersion profiles are determined, could have hardly been studied with classical methods. These new results are particularly significant, especially in what concerns the velocity dispersion profile, since little is known so far on its characteristics.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain. 相似文献
1000.
Natural Resources Research - A method for predictive lithological mapping is proposed, which combines geostatistical simulation of geochemical concentrations with coregionalization analysis and... 相似文献