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41.
Enzo Boschi 《Pure and Applied Geophysics》1973,111(1):2147-2157
Summary An explicit expression is derived for the body force, body couple and heat source to be applied in the absence of a seismic dislocation, which produces a thermodynamical behaviour equivalent to that produced by the dislocation. 相似文献
42.
The experience acquired during 36 Woodhead drifter releases performed along the Tuscan coast is briefly reported. Without a costly apparatus, residual current patterns may be easily obtained with this method. Care should be taken, however, when sediment dispersal patterns are required, since weak currents which drag drifters slowly, displace only finer sediments. 相似文献
43.
Marco Pierleoni Enzo Branchini Matteo Viel 《Monthly notices of the Royal Astronomical Society》2008,388(1):282-292
We use high-resolution hydrodynamical simulations to investigate the spatial correlation between weak ( N H i < 1015 cm−2 ) Lyα absorbers and gas-rich galaxies in the local Universe. We confirm that Lyα absorbers are preferentially expected near gas-rich galaxies and that the degree of correlation increases with the column density of the absorber. The real-space galaxy auto-correlation is stronger than the cross-correlation (correlation lengths r 0,gg = 3.1 ± 0.1 Mpc h −1 and r 0,ag = 1.4 ± 0.1 Mpc h −1 , respectively), in contrast with the recent results of Ryan-Weber, and the auto-correlation of absorbers is very weak. These results are robust to the presence of strong galactic winds in the hydrodynamical simulations. In redshift space, a further mismatch arises since at small separations the distortion pattern of the simulated galaxy–absorber cross-correlation function is different from the one measured by Ryan-Weber. However, when sampling the intergalactic medium along a limited number of lines-of-sight, as in the real data, uncertainties in the cross-correlation estimates are large enough to account for these discrepancies. Our analysis suggests that the statistical significance of difference between the cross-correlation and auto-correlation signal in current data sets is ∼1σ only. 相似文献
44.
45.
Silvia Bonoli Federico Marulli Volker Springel Simon D. M. White Enzo Branchini Lauro Moscardini 《Monthly notices of the Royal Astronomical Society》2009,396(1):423-438
We use semi-analytic modelling on top of the Millennium simulation to study the joint formation of galaxies and their embedded supermassive black holes. Our goal is to test scenarios in which black hole accretion and quasar activity are triggered by galaxy mergers, and to constrain different models for the light curves associated with individual quasar events. In the present work, we focus on studying the spatial distribution of simulated quasars. At all luminosities, we find that the simulated quasar two-point correlation function is fit well by a single power law in the range 0.5 ≲ r ≲ 20 h −1 Mpc , but its normalization is a strong function of redshift. When we select only quasars with luminosities within the range typically accessible by today's quasar surveys, their clustering strength depends only weakly on luminosity, in agreement with observations. This holds independently of the assumed light-curve model, since bright quasars are black holes accreting close to the Eddington limit, and are hosted by dark matter haloes with a narrow mass range of a few 1012 h −1 M⊙ . Therefore, the clustering of bright quasars cannot be used to disentangle light-curve models, but such a discrimination would become possible if the observational samples can be pushed to significantly fainter limits. Overall, our clustering results for the simulated quasar population agree rather well with observations, lending support to the conjecture that galaxy mergers could be the main physical process responsible for triggering black hole accretion and quasar activity. 相似文献
46.
Enzo Cartapati 《地震工程与工程振动(英文版)》2012,11(2):289-290
This discussion will address two aspects found in the paper:lack of proper information and some mistakes.
Lack of proper information
In Section 2 of the paper,a short review of the seismic events suffered by the Basilica and of the interventions of reconstruction which have followcd is presented,but the main effects of these events are not sufficiently highlightcd.In what follows,additional information is provided to allow a better understanding of the most recent retrofit intervention and of the seismic behavior of the Basilica in 2009. 相似文献
47.
Andrea Marzoli Paul R. Renne Enzo M. Piccirillo Castorina Francesca Giuliano Bellieni Adolpho J. Melfi Jean B. Nyobe Jean N'ni 《Contributions to Mineralogy and Petrology》1999,135(2-3):133-150
The intraplate Cameroon Volcanic Line (CVL) straddles the African-South Atlantic continent-ocean boundary and is composed
mainly of alkaline basic volcanic rocks. Voluminous silicic volcanics characterize the continental sector of the CVL. We present
here new geochemical, isotopic (Sr-Nd-O) and 40Ar/39Ar geochronological data on the main silicic volcanic centres of the Western (Mt. Oku, Sabga and Mt. Bambouto) and Eastern
(Ngaoundere plateau) Cameroon Highlands. The silicic volcanism of Mt. Oku, Sabga and Mt. Bambouto occurred between 25 and
15 Ma and is represented by voluminous quartz-normative trachytes and minor rhyolitic ignimbrites. At Mt. Bambouto central
volcano about 700 m of silicic volcanics erupted in less than 2.7 million years. These silicic volcanics are associated with
slightly to moderately alkaline basalts and minor basanites. In general, onset of the silicic volcanism migrated from NE (Oku:
25 Ma) to SW (Sabga: 23 Ma; Bambouto: 18 Ma; and Mt. Manengouba: 12 Ma). The silicic volcanism of the Ngaoundere plateau (eastern
branch of the CVL) is instead dominated by nepheline-normative trachytes which are associated with strongly alkaline basalts
and basanitic rocks. These Ne-trachytes are younger (11-9 Ma) than the Q-trachytes of the Western Highlands. The least differentiated
silicic volcanics are isotopically similar (87Sr/86Sr < 0.70380; 143Nd/144Nd > 0.51278) to the associated alkaline basalts suggesting differentiation processes without appreciable interaction with
crustal materials. Such interactions may, however, have played some role in the genesis of the most evolved silicic volcanics
which have 87Sr/86Sr as high as 0.705–0.714. Fractional crystallization is the preferred mechanism for genesis of the silicic melts of both
Western and Eastern Highlands, as shown by modeling major and trace element variations. The genesis of the least evolved Q-trachytes
from the Western Highlands, starting from slightly to moderately alkaline basalts, is compatible with fractionation of dominantly
plagioclase, clinopyroxene and magnetite. Crystal fractionation may have occurred at low pressure and at QFM buffer f
O2conditions. Parental magmas of the Ngaoundere Ne-trachytes are likely instead to have been strongly alkaline basalts which
evolved through crystal fractionation at higher P (6-2 kbar) and f
O2 (QFM + 2). The migration (25 to 12 Ma) of the silicic volcanism from NE to SW in the continental sector of the CVL is reminiscent
of that (31-5 Ma) of the onset of the basic volcanism in the oceanic sector (Principe to Pagalu islands) of the CVL. These
ages, and that (11-9 Ma) of the silicic volcanism of the Ngaoundere plateau, indicate that the Cameroon Volcanic Line as a
whole may not be easily interpreted as the surface expression of hot-spot magmatism.
Received: 24 February 1998 / Accepted: 22 September 1998 相似文献
48.
Michele Dragoni Maurizio Bonafede Enzo Boschi 《Journal of Volcanology and Geothermal Research》1986,30(3-4)
It is widely recognized that lavas behave as Bingham liquids, which are characterized by a yield stress σ and a plastic viscosity η. We consider two models describing downslope flows of a Bingham liquid with different aspect ratios A (= flow height/flow width): model 1 with A 1 and model 2 with A ≈ 1. Sufficiently uphill with respect to the front, such flows can be considered as laminar and locally isothermal. For both models, we obtain analytically the steady-state solution of the Navier-Stokes equations and the constitutive equation for a Bingham liquid. We study the flow height and velocity as functions of flow rate, rheological parameters and ground slope. It is found that such flows remain in the Newtonian regime at low yield stresses (σ 103dyne/cm2), but the transition to the Bingham regime also depends on flow rate and occurs at higher values of σ for higher flow rates: for instance, a high aspect ratio flow (model 2) is still very close to the Newtonian regime at σ = 104 dyne/cm2, if the flow rate is greater than 105 g/s. In the Bingham regime, flow heights are generally greater and flow velocities are smaller than in the Newtonian regime; moreover, flow heights are independent of flow rate, so that a change in flow rate results exclusively in a velocity change. After assuming a specific temperature dependence of σ and η between the solidus and the liquidus temperatures of an ideal Bingham liquid (1000°C and 1200 °C respectively), flow heights and velocities are examined as functions of temperature along the flow. Several effects observed in lava flows are predicted by these models and allow a more quantitative insight into the behaviour of lava flows. 相似文献
49.
The Chirripó hydrological research site (CHRS) is located within the Chirripó National Park, Costa Rica (between 3100 and 3820 m asl) whereby ~100 km2 are covered by Páramo, a high-elevation tropical grassland ecosystem. A lake district with approximately 30 lakes of glacial origin is also protected in this area. The CHRS has been monitored since April 2015 with the aim of establishing the first water isotope baseline for the Central American Páramo. At a regional scale, the water isotope ratios (δ2H and δ18O) in precipitation and surface water at CHRS are useful for describing the governing moisture transport from the Caribbean Sea and Pacific Ocean and the complex rainfall producing systems across the N–S mountain range of Central America. These data are also providing unique information about the evaporation and water balance conditions of tropical glacial lakes and the formation of orographic and convective precipitation in high-elevation tropical ecosystems. Current data sets from CHRS include continuous lake water temperature and meteorological conditions (i.e., precipitation amount, air temperature and relative humidity), as well as water stable isotopes in precipitation, stream water, and lake water (daily to biweekly sampling frequency). Stream water is collected at several locations across the topographic gradient whereas lake water is sampled in the three main lake systems of CHRS. CHRS serves as a reference site for conducting pilot isotopic research in high-elevation ecosystems to advance the atmospheric, hydrogeological and ecohydrological studies in these understudied biomes. All data from April 2015 to November 2020 are publicly available. 相似文献
50.