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排序方式: 共有101条查询结果,搜索用时 46 毫秒
31.
Gianfranco Bertone Günter Sigl Joseph Silk 《Monthly notices of the Royal Astronomical Society》2002,337(1):98-102
We study annihilation radiation of neutralinos in the Galactic Centre, assuming the existence of a 'spike' in the dark matter density profile, caused by adiabatic accretion on to the massive black hole lying at the Galactic Centre. Under this assumption we find that it is possible to reproduce the observed SgrA* emission at radio and gamma-ray frequencies in a consistent scenario with a magnetic field close to the equipartition strength and with values of γ (the density profile power-law index) around 0.1. 相似文献
32.
Bulletin of Earthquake Engineering - A correction to this paper has been published: https://doi.org/10.1007/s10518-021-01105-0 相似文献
33.
Mirko Carlini Alessandro Chelli Roberto Francese Serena Giacomelli Massimo Giorgi Andrea Quagliarini Andrea Carpena Claudio Tellini 《Landslides》2018,15(2):283-296
This paper investigates the role played by geomorphological and tectonic processes affecting a portion of an active mountain belt in causing the occurrence of different types of landslides developed in flysch bedrock. The adopted multidisciplinary approach (geomorphology, geology and geophysics) allowed to recognize in a portion of the Northern Apennines of Italy different types of landslides that developed in response to slope dynamics, in turn dependent on broader regional-scale tectonic processes. Sedimentary bed attitude, local tectonic discontinuities and lithology only partially influenced the type of landslides, which have been deeply affected by the activity of regional-scale antiform that controlled the hillslope geomorphic evolution in different ways. The growth of this structure and the tilting of its forelimb produced gently dipping slopes that approached the threshold angle that can cause the occurrence of (mainly) translational rockslides. Conversely, high-angle normal faulting parallel to the antiform axis (related to a later stage of activity of the antiform itself) strongly controlled the stream network evolution and caused the watercourses to deeply incise portions of their valleys. This incision produced younger steep valley slopes and caused the development of complex landslides (roto-translational slides-earth/debris flow). The results of the integrated study presented in this paper allowed to distinguish two main types of landslides whose development reflects the events that led to the geomorphological and geological evolution of the area. In this perspective, within the study area, landslides can be regarded and used as indicators of broader-scale recent tectonic processes. 相似文献
34.
Temperature, salinity, meltwater percentage, water column stability, dissolved oxygen and nutrients were measured in seawater samples collected at three fixed depths (0, 20, 100 m) in 104 stations located in three different areas of the Ross Sea (Antarctica), during four Italian Antarctic surveys carried out between 1998 and 2006. Nutrient data were used to quantify the nutrient removal, which appears particularly high in 2006, especially in polynya area. The N:P and Si:N disappearance ratios were studied to estimate the dominant phytoplanktonic community. No significant differences in the nutrient drawdown ratio were observed, in fact the N:P ratio was always below the Redfield standard ratio. 相似文献
35.
Bruno Cataletto Enrico Feoli Serena Fonda Umani Marina Monti Irene Pecchiar 《Marine Ecology》1996,17(1-3):291-307
Abstract. Multivariate techniques (cluster analysis and Principal Component Analysis) applied on phytoplankton data collected in June, July, August, and September 1990, 1991, 1992, and 1993 in the Gulf of Trieste (Northern Adriatic Sea) highlighted a clear temporal pattern from 1990 to 1993. In the summer of 1991, phytoplankton communities showed a dramatic increase in the dinoflagellatddiatom ratio. In particular, during June and July 1991 only few specimens of diatoms ( Cylindrorhecu closreriurn. Probosciu alata, Nirzschio longissimu , and Nitzschiu spp.) were collected; this confirmed the diatom scarcity in the phytoplankton communities before and during the appearance of large mucous aggregates (mucilage) in July 1991 in the Gulf of Trieste. The differences observed between the structure of the phytoplankton communities inside the aggregates and in the ambient waters suggested two hypotheses: 1) the aggregates were not produced in the gulf, but were carried ints the gulf by the eastern bordering current; 2) the aggregates were produced by a few, scarce species with a high exudate production that are capable of quickly reaching a high reproductive rate within the aggregates. 相似文献
36.
This paper deals with five-dimensional black hole solutions in (a) Einstein-Maxwell-Gauss-Bonnet theory with a cosmological
constant and (b) Einstein-Yang-Mills-Gauss-Bonnet theory for spherically symmetric space time. In both the cases the possibility
of phase transition is examined and it is analyzed whether the phase transition is a Hawking-Page type phase transition or
not. 相似文献
37.
The GALEX General Data Release 4/5 includes 174 spectroscopic tiles, obtained from slitless grism observations, for a total of more
than 60 000 ultraviolet spectra. We have determined statistical properties of the sample of GALEX stars. We have defined a suitable system of spectroscopic indices, which measure the main mid-UV features at the GALEX low spectral resolution and we have employed it to determine the atmospheric parameters of stars in the range 4500≲T
eff≲9000 K. Our preliminary results indicate that the majority of the sample is formed by main sequence F- and G-type stars,
with metallicity [M/H]≳−1 dex. 相似文献
38.
39.
40.
Dr Serena Viti PhD Thomas W. Hartquist Philip C. Myers 《Astrophysics and Space Science》2006,302(1-4):109-115
We present models for the chemistry in gas moving towards the ionization front of an HII region. When it is far from the ionization
front, the gas is highly depleted of elements more massive than helium. However, as it approaches the ionization front, ices
are destroyed and species formed on the grain surfaces are injected into the gas phase. Photodissociation removes gas phase
molecular species as the gas flows towards the ionization front. We identify models for which the OH column densities are
comparable to those measured in observations undertaken to study the magnetic fields in star forming regions and give results
for the column densities of other species that should be abundant if the observed OH arises through a combination of the liberation
of H2O from surfaces and photodissociation. They include CH3OH, H2CO, and H2S. Observations of these other species may help establish the nature of the OH spatial distribution in the clouds, which is
important for the interpretation of the magnetic field results. 相似文献