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211.
212.
B. V. Belyatsky N. V. Rodionov A. V. Antonov S. A. Sergeev 《Doklady Earth Sciences》2011,438(2):770-774
This study presents new results on zircons from the enderbite-charnockite rocks of Enderby Land, East Antarctica. U-Pb age
of 3981 ± 8 Ma (SIMS SHRIMP II), which was first obtained for a protolith of massive enderbites from Aker Peaks, eastern Napier
Mts, suggests that the existence of sialic crust in the study area at 4 Ga. Although there was only one magmatic zircon (of
150 grains analyzed) in the study area known with the oldest age, its significance cannot be overestimated, since it may indirectly
evidence the existence of an Early Archean crustal block with a minimum age of 4 Ga, which extends for over 300 km across
Enderby Land from its western to eastern part. Based on the U-Pb systematics, REE and trace element distributions in zircons
from charnockite and enderbite gneisses, high-aluminous gneisses, and basic granulites, we first revealed that an early high-temperature
metamorphic event accompanied by the emplacement of granodiorite intrusions occurred in the vicinity of Aker Peaks at 3620–3630
Ma. Although the 2850–3050 metamorphic overprints are clearly observed in some other areas of Enderby Land and are widely
considered to be of critical importance on a regional scale, their metamorphic signatures are apparently absent from the U-Pb
systematics of the studied zircon, thus suggesting the presence of similar old zircons in the study area. At the same time,
all samples in this study record a 2480–2550 Ma granulite-amphibolite facies overprint represented as new zircon growths or
recrystallization of earlier phases. 相似文献
213.
A. E. Vol’vach L. N. Vol’vach A. M. Kut’kin M. G. Larionov M. Villata K. M. Panteri A. Lahteenmaki M. Tornikoski P. Savolainen G. Tammi A. F. Aller H. D. Aller S. G. Sergeev V. T. Doroshenko Yu. S. Efimov S. A. Klimanov S. V. Nazarov G. V. Borman A. B. Pushkarev V. I. Zhdanov E. V. Fedorova I. B. Vavilova N. G. Chesnok 《Astronomy Reports》2011,55(7):608-615
Long-term monitoring data at five radio frequencies from 4.8 to 37 GHz obtained at the Crimean Astrophysical Observatory, Metsahovi Radio Observatory of Aalto University, and the University of Michigan Radio Astronomy Observatory are used to analyze variations of the flux of the Active Galactic Nucleus (AGN) 3C 454.3. The dynamical characteristics of the three latest powerful flares from 2004 to 2010 are analyzed in detail. Observations in the gamma-ray (0.1–300 GeV), X-ray (2–10 kev, 15–50 keV), and optical are also used. Delays in the development of flares at different frequencies are derived. An empirical frequency dependence for the delays of flares from the gamma-ray to the radio is determined, which can be fit using a logarithmic low and remains the same from flare to flare. The physical characteristics of the central region of the AGN 3C 454.3 are used to estimate the size of its Strömgren sphere, taking into account the relevant mechanisms for heating and cooling the medium, as well as the adopted laws for the variation of the density and temperature with distance from the source of ionization. A model for the location of the radiation regions in the jet at various frequency ranges during the development of flares is proposed. 相似文献
214.
Dmitry A. Ruban 《Gondwana Research》2011,20(4):739-744
Global sea-level rise and consequent regional transgressions are hypothesized at the beginning of the Devonian. A brief review of lithostratigraphical data available from three regions of the “Tethyan” margin of Gondwana, namely Northern Africa, Arabia, and the Tethys Himalaya, suggests that all of them were characterized by a regressive setting in the Lochkovian. In contrast, data from some terranes of the Greater Galatian Superterrane provide evidence of early Lochkovian transgression. The regressive setting documented on the 'Tethyan' margin of Gondwana differs from the transgressive–regressive cycles of Euramerica and the norm of global sea-level rise followed by a highstand. Only regional tectonic processes including those linked with dynamic topography could explain these differences. These processes may have been associated with syn-rift uplift preceding the opening of the Palaeo-Tethys Ocean, mantle uplift at the supercontinent margin, or the Eo-Variscan orogenic phase. 相似文献
215.
An investigation undertaken recently by the Division of Regional Geoecology and Marine Geology of the Karpinsky All-Russian
Research Geological Institute in the coastal zones of the Eastern Gulf of Finland allowed finding some specific relief forms
of both near-shore bottom topography and shoreline shape. First of all, among the most interesting objects, the sand ridges
on the surface of submarine terrace (between Repino locality and Cape Lautaranta) should be mentioned. These ridges are elongated
at an angle to the shoreline and are located beyond the limits of wave action. The other interesting morphological type is
represented by longshore sand waves up to some hundreds of meters long and some tens of meters wide near the Bol’shaya Izhora
locality. Longshore sand waves move along the southern coast of the gulf, this causing alteration of erosion and accretion
zones and leading to formation and degradation of the sand spits. Shore-face-connected ridges are believed to develop under
the action of drift currents generated during the passage of deep west cyclones. It is shown that the ridge turned toward
the current gives rise to a convergence of the cross-shore flows over the crest and provokes a shift of the maximum velocity
toward the front side of the structure. Associated changes in sediment discharges result in accumulation and growth of the
ridge. The origin of wavelike features in the shoreline contour (longshore sand waves) is due to a very oblique wave approach
caused by predominance of the west winds blowing along the axis of the gulf. Under these conditions a small perturbation of
the shoreline contour is shown to manifest a trend to increase with time. 相似文献
216.
V. V. Bakhanov N. A. Bogatov S. N. Vlasov V. I. Kazakov E. V. Koposova D. A. Sergeev 《Oceanology》2011,51(4):543-553
This paper presents the results of laboratory measurements of surface currents over a sphere moving in the fluid column based
on the particle tracing velocimetry. A theoretical model of the fluid flowing around the sphere is presented. The experimental
data are compared with the results of theoretical calculations. It is shown that, at low tow speeds of the sphere, the experimentally
measured current velocities exceed the velocities calculated from the theoretical model. At greater tow velocities when generation
of surface waves by the sphere was observed in the experiment, the experimental data agree well with the results of the theoretical
calculations. 相似文献
217.
We consider a conventional stellar α2 ω -dynamo with dynamo generators localized in two spherical shells separated by a passive layer. The signs of the α-effect as well as rotational shear in the dynamo active layers can be chosen to give dynamo waves that propagate in opposite directions (poleward and equatorward) if the layers are considered separately in the framework of the Parker migratory dynamo. In a sequence of numerical experiments we show that the variety of dynamo-generated magnetic configurations in the system under discussion is quite rich. We identify the possibility of almost independent dynamo waves existing in the two layers as well as enslavement of one layer by the other, and of activity waves generated by a joint action of the two layers. We suggest some qualitative explanations of the behaviour and discuss also the limited nature of these explanations. This variety of phenomena suggests previously underexploited freedoms to understand how predictions of dynamo theory may accommodate the observed solar and stellar activity phenomenology. 相似文献
218.
V. T. Doroshenko S. G. Sergeev N. I. Merkulova E. A. Sergeeva Yu V. Golubinsky V. I. Pronik N. N. Okhmat 《Astrophysics》2005,48(2):156-178
Results are presented from CCD BVRI observations of comparison stars in the neighborhoods of 22 galaxies with active nuclei having right ascensions ranging from 0 to 12 hours, of which 19 are Seyfert galaxies. The observed stars have magnitudes ranging from V=11 to V=17. For stars brighter than V=14 the typical photometic error is 0.01m. The B, V, Rc, and Ic magnitudes of most of these stars were not known previously. 14′×14′ finding charts are included. These results can be used for differential photometry of the AGNs in the B, V, Rc, and Ic bands.__________Translated from Astrofizika, Vol. 48, No. 2, pp. 191–211 (May 2005). 相似文献
219.
Dmitry Volobuev 《Solar physics》2004,224(1-2):387-392
Each of the available solar activity (SA) proxy data (historical notes, radio nuclides 14C and 10Be production) are contaminated by their specific noise factors. So, any additional proxy with its independent noise factors
will essentially increase the accuracy of composite SA restorations. It is proposed here that archaeomagnetic measurements
95% confidence interval (α95) may serve as new proxy for the SA estimation in the past. This proxy is compared with other available proxies during the
years 1500–2000. 相似文献
220.
Ocean Dynamics - A Correction to this paper has been published: https://doi.org/ https://doi.org/10.1007/s10236-021-01450-3 相似文献