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91.
92.
J. M. Oliveira R. D. Jeffries J. Th. van Loon M. T. Rushton 《Monthly notices of the Royal Astronomical Society》2006,369(1):272-280
We present new K - and L '-band imaging observations for members of the young (3–5 Myr) σ Orionis cluster, obtained at the United Kingdom Infrared Telescope (UKIRT) with the UKIRT 1–5 micron Imager Spectrometer (UIST). We determine ( K − L ') colour excesses with respect to the photospheres, finding evidence for warm circumstellar dust around 27 out of 83 cluster members that have masses between 0.04 and 1.0 M⊙ . This indicates a circumstellar disc frequency of at least (33 ± 6) per cent for this cluster, consistent with previous determinations from smaller samples and also consistent with the 3-Myr disc half-life suggested by Haisch et al. There is marginal evidence that the disc frequency declines towards lower masses, but the data are also consistent with no mass dependence at all. There is no evidence for spatial segregation of objects with and without circumstellar discs. 相似文献
93.
Results of the DEKORP 1 (BELCORP-DEKORP) deep seismic reflection studies in the western part of the Rhenish Massif 总被引:1,自引:0,他引:1
DEKORP Research GroupH.-J. Anderle R. Bittner R. Bortfeld J. Bouckaert G. Büchel G. Dohr H.-J. Dürbaum H. Durst W. Fielitz E. Flüh T. Gundlach L. Hance A. Henk F. Jordan D. Kläschen M. Klöckner R. Meissner W. Meyer O. Oncken C. Reichert K.-H. Ribbert P. Sadowiak H.-U. Schmincke J. Schmoll R. Walter K. Weber U. Weihrauch Th. Wever 《Geophysical Journal International》1991,106(1):203-227
94.
M. den Heijer G. I. G. Jzsa J. Kerp P. Serra Th. van der Hulst G. Kauffmann J. Wang F. Bigiel J. Brinchmann D. Carton D. Cormier M.‐L. Huang 《Astronomische Nachrichten》2015,336(3):284-311
We examine the H I kinematics of the “Bluedisk” ensemble of 48 galaxies selected from the Sloan Digital Sky Survey and observed in H I with the Westerbork Synthesis Radio Telescope. The sample consists of 25 galaxies with a high H I mass fraction and a comparatively large control sample comprising 23 galaxies of comparable stellar mass, stellar mass surface density, redshift, and inclination. By studying the H I velocity fields of these galaxies, we investigate whether there are signatures of ongoing gas accretion: i.e. global asymmetries and indications for warping and kinematical lopsidedness. We find no enhanced kinematical asymmetries between the H I‐rich sample and the control sample galaxies, indicating no significant difference in kinematical signatures such as warping and lopsidedness. Furthermore, we find no difference in position angle and systemic velocity offset with respect to the optical between both sub‐samples. We therefore do not find compelling evidence for enhanced global asymmetry of the H I‐excess galaxies ensemble properties in comparison to the control sample galaxies. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
95.
U. Ott S. Merchel S. Herrmann S. Pavetich G. Rugel T. Faestermann L. Fimiani J. M. Gomez‐Guzman K. Hain G. Korschinek P. Ludwig M. D'Orazio L. Folco 《Meteoritics & planetary science》2014,49(8):1365-1374
Cosmogenic He, Ne, and Ar as well as the radionuclides 10Be, 26Al, 36Cl, 41Ca, 53Mn, and 60Fe have been determined on samples from the Gebel Kamil ungrouped Ni‐rich iron meteorite by noble gas mass spectrometry and accelerator mass spectrometry (AMS), respectively. The meteorite is associated with the Kamil crater in southern Egypt, which is about 45 m in diameter. Samples originate from an individual large fragment (“Individual”) as well as from shrapnel. Concentrations of all cosmogenic nuclides—stable and radioactive—are lower by a factor 3–4 in the shrapnel samples than in the Individual. Assuming negligible 36Cl decay during terrestrial residence (indicated by the young crater age <5000 years; Folco et al. 2011 ), data are consistent with a simple exposure history and a 36Cl‐36Ar cosmic ray exposure age (CRE) of approximately (366 ± 18) Ma (systematic errors not included). Both noble gases and radionuclides point to a pre‐atmospheric radius >85 cm, i.e., a pre‐atmospheric mass >20 tons, with a preferred radius of 115–120 cm (50–60 tons). The analyzed samples came from a depth of approximately 20 cm (Individual) and approximately 50–80 cm (shrapnel). The size of the Gebel Kamil meteoroid determined in this work is close to estimates based on impact cratering models combined with expectations for ablation during passage through the atmosphere (Folco et al. 2010 , 2011 ). 相似文献
96.
Summary. The first DEKORP profile, DEKORP 2-S, a 250 km long line perpendicular to the Variscan strike direction, has provided evidence of major crustal shortening during the Variscan orogeny. Sporadic dipping events in a generally transparent upper crust are interpreted as thrust faults, while the highly reflective lower crust fits into the general picture of Palaeozoic provinces. Correlations are established between certain reflectivity patterns and rheology. Moho depths and reflecting lamellae are considered to be post-Variscan. 相似文献
97.
98.
The formation of a weak shock at the interaction of the solar wind with the cometary neutral gas is confirmed in a non-stationary gasdynamic model. No shocks will be detectable along the ICE path and if the VEGA/GIOTTO spacecraft enter the cometary atmosphere. A shock can only be expected at an exit from the Halley atmosphere. 相似文献
99.
100.