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581.
Hydrogeochemistry of Roccamonfina volcano (Southern Italy) 总被引:1,自引:1,他引:0
Emilio Cuoco Giuseppe Verrengia Stefano De Francesco Dario Tedesco 《Environmental Earth Sciences》2010,61(3):525-538
This is the first hydro-geochemical investigation carried out on the Roccamonfina Volcanic Complex groundwaters. The chemistry
of Roccamonfina waters is defined by water–rock and water–rock–gas interactions. In fact, interactions between rocks of the
first eruptive high-K formations and circulating groundwaters are recognized by high K concentrations. On the other hand,
inverse concentration of calcium versus alkali metals is related to two different rock interactions occurring in different
areas of the volcano: (a) within the caldera where groundwaters flow within latite and pyroclastic formations releasing calcium,
and (b) similarly at the base of the volcano where groundwaters flowing from surrounding carbonates got strongly enriched
in Ca. These geochemical processes are also associated with K (SE of caldera) and Mg/Ca (in sites located at the NE base of
the volcano) decrease. Completely different dynamics occurs at Riardo groundwaters (SE). Here waters are the result of a mix
between the Roccamonfina deep aquifer and the carbonate aquifer of the Riardo plain. Rich-CO2 emissions make these waters strongly mineralized. Minor elements show a similar geochemical behavior of major ions and are
crucial defining interactions processes. The evolution of Roccamonfina groundwaters is also evident along the simultaneous
enrichment of Ba, Sr, and Ca. Ba increase is the result of deep local carbonate alteration enhanced by CO2 emissions and, the lower Sr/Ca ratio, from 10 to 2 (ppb/ppm), is also due to the same process. In the light of our results
the Roccamonfina aquifer can be schematically divided into two main reservoirs: (a) a superficial aquifer which basically
follows the volcanic structure morphology and tectonics and (b) a deeper reservoir, originating within the oldest Roccamonfina
volcano ultra potassic lavas and then flowing into the carbonate aquifers of the neighboring plain. Eventually, the chemistry
of the Roccamonfina aquifer does not show any specific and visible pollution, contrary to what happens in the volcano surrounding
plains. In fact, only 14% of the samples we collected (206) show a NO3 content >30 mg/l. These sites are all located at the base of the volcano, near the plain. 相似文献
582.
583.
Costanza Di Stefano Alessio Nicosia Vincenzo Palmeri Vincenzo Pampalone Vito Ferro 《水文研究》2021,35(7):e14296
Recent research recognized that the slope of 18% can be used to distinguish between the ‘gentle slope’ case and that of ‘steep slope’ for the detected differences in hydraulic variables (flow depth, velocity, Reynolds number, Froude number) and those representatives of sediment transport (flow transport capacity, actual sediment load). In this paper, using previous measurements carried out in mobile bed rills and flume experiments characterized by steep slopes (i.e., slope greater than or equal to 18%), a theoretical rill flow resistance equation to estimate the Darcy-Weisbach friction factor is tested. The main aim is to deduce a relationship between the velocity profile parameter Γ, the channel slope, the Reynolds number, the Froude number and the textural classes using a data base characterized by a wide range of hydraulic conditions, plot or flume slope (18%–84%) and textural classes (clay ranging from 3% to 71%). The obtained relationship is also tested using 47 experimental runs carried out in the present investigation with mobile bed rills incised in a 18%—sloping plot with a clay loam soil and literature data. The analysis demonstrated that: (1) the soil texture affects the estimate of the Γ parameter and the theoretical flow resistance law (Equation 25), (2) the proposed Equation (25) fits well the independent measurements of the testing data base, (3) the estimate of the Darcy-Weisbach friction factor is affected by the soil particle detachability and transportability and (4) the Darcy-Weisbach friction factor is linearly related to the rill slope. 相似文献
584.
Assessment of the impact of climate change on the olive flowering in Calabria (southern Italy) 总被引:1,自引:1,他引:0
Elenio Avolio Fabio Orlandi Carlo Bellecci Marco Fornaciari Stefano Federico 《Theoretical and Applied Climatology》2012,107(3-4):531-540
In phenological studies, plant development and its relationship with meteorological conditions are considered in order to investigate the influence of climatic changes on the characteristics of many crop species. In this work, the impact of climate change on the flowering of the olive tree (Olea europaea L.) in Calabria, southern Italy, has been studied. Olive is one of the most important plant species in the Mediterranean area and, at the same time, Calabria is one of the most representative regions of this area, both geographically and climatically. The work is divided into two main research activities. First, the behaviour of olive tree in Calabria and the influence of temperature on phenological phases of this crop are investigated. An aerobiological method is used to determine the olive flowering dates through the analysis of pollen data collected in three experimental fields for an 11-year study period (1999–2009). Second, the study of climate change in Calabria at high spatial and temporal resolution is performed. A dynamical downscaling procedure is applied for the regionalization of large-scale climate analysis derived from general circulation models for two representative climatic periods (1981–2000 and 2081–2100); the A2 IPCC scenario is used for future climate projections. The final part of this work is the integration of the results of the two research activities to predict the olive flowering variation for the future climatic conditions. In agreement with our previous works, we found a significant correlation between the phenological phases and temperature. For the twenty-first century, an advance of pollen season in Calabria of about 9?days, on average, is expected for each degree of temperature rise. From phenological model results, on the basis of future climate predictions over Calabria, an anticipation of maximum olive flowering between 10 and 34?days is expected, depending on the area. The results of this work are useful for adaptation and mitigation strategies, and for making concrete assessments about biological and environmental changes. 相似文献
585.
Precision spacecraft navigation using a low-cost GPS receiver 总被引:1,自引:1,他引:0
Oliver Montenbruck Paul Swatschina Markus Markgraf Stefano Santandrea Joris Naudet Etienne Tilmans 《GPS Solutions》2012,16(4):519-529
Within the PROBA-2 microsatellite mission, a miniaturized single-frequency GPS receiver based on commercial-off-the-shelf (COTS) technology is employed for onboard navigation and timing. A rapid electronic fuse protects against destructive single-event latch-ups (SEL) and enables a quasi-continuous receiver operation despite the inherent sensitivity to space radiation. While limited to single-frequency C/A-code tracking with a narrow-band frontend, the receiver is able to provide precision navigation services through processing of raw GPS measurements on ground as well as a built-in real-time navigation system. In both cases, ionospheric path delays are eliminated through a combination of L1 pseudorange and carrier phase measurements, which also offers a factor-of-two noise reduction relative to code-only processing. By comparison with satellite laser ranging (SLR) measurements, a 0.3-m (3D rms) accuracy is demonstrated for the PROBA-2 reduced dynamic orbit determinations using post-processed GPS orbit and clock products. Furthermore, the experimental onboard navigation system is shown to provide real-time position information with a 3D rms accuracy of about 1?m, which notably outperforms the specification of the Standard Positioning Service (SPS). In view of their lower hardware complexity, mass budget and power requirements as well as the reduced interference susceptibility, legacy C/A-code receivers can thus provide an attractive alternative to dual-frequency receivers even for demanding navigation applications in low Earth orbit. 相似文献
586.
在标准的伽玛暴余辉模型中,电子通过费米一级加速后形成单幂律能谱分布dn/dγe∝γe-p(p≈2.3),但在某些伽玛暴事件中观测到了平缓的电子能谱分布(即p<2).在单幂律谱和分段幂律谱两种情况下,分别给出了具有平缓电子能谱的伽玛暴余辉的解析光变曲线,并以GRB 060908为例进行了讨论.同时提出了伽玛暴低能谱危机的... 相似文献
587.
The impact of spatially non-uniform emissions on the turbulence dispersion of passive tracers in the convective boundary layer
is studied by means of large-eddy simulation. We explicitly calculated the different terms of the budget equations for the
concentrations, fluxes and variances, and used sub-domain averaging where each sub-domain is the typical size of a large-scale
model grid cell. We found that the concentration profiles in the sub-domain where the emission takes place are lightly affected
by the size of the emission release. This effect becomes more relevant in the downwind sub-domain. Although sub-domain averaged
fluxes are not affected by the emission source size, concentration variances are dramatically increased when the emission
shrinks. This increase originates from the mixing of highly concentrated air parcels with those of low concentrations. We
also found that the concentration variance at the surface is driven neither by the position of the emission source nor the
strength of the shear forcing but solely by the emission variance. 相似文献
588.
Goro Komatsu Gaetano Di Achille Ciprian Popa Stefano Di Lorenzo Jose Alexis Palmero Rodriguez 《Icarus》2009,201(2):474-491
The plains of Aurorae and Ophir in the equatorial region of Mars display geomorphic evidence indicative of extensive but generally short-lived paleohydrological processes. Elaver Vallis in Aurorae Planum south of Ganges Chasma is an outflow channel system >180 km long, and here inferred to have formed by cataclysmic spillover flooding from a paleolake(s) contained in the Morella crater basin. Ganges Cavus is an enormous 5-km-deep depression of probable collapse origin located in the Morella basin. The fluid responsible for the infilling of the Morella basin likely emerged at least partially through Ganges Cavus or its incipient depression, and it may have been supplied also from small-scale springs in the basin. Similar paleohydrological processes are inferred also in Ophir Planum. It is reasonable to assume that water, sometimes sediment-laden and/or mixed with gases, was the responsible fluid for these phenomena although some of the observed features could be explained by non-aqueous processes such as volcanism. Water emergence may have occurred as consequences of ground ice melting or breaching of cryosphere to release water from the underlying hydrosphere. Dike intrusion is considered to be an important cause of formation for the cavi and smaller depressions in Aurorae and Ophir Plana, explaining also melting of ground ice or breaching of cryosphere. Alternatively, the depressions and crater basins may have been filled by regional groundwater table rising during the period(s) when cryosphere was absent or considerably thin. The large quantities of water necessary for explaining the paleohydrological processes in Aurorae and Ophir Plana could have been derived through crustal migration from the crust of higher plains in western Ophir Planum where water existed in confined aquifers or was produced by melting of ground ice due to magmatic heating or climatic shift, or from a paleolake in Candor Chasma further west. 相似文献
589.
Stefano Zibetti Daniele Pierini Gabriel W. Pratt 《Monthly notices of the Royal Astronomical Society》2009,392(2):525-536
We study six groups and clusters of galaxies suggested in the literature to be 'fossil' systems (i.e. to have luminous diffuse X-ray emission and a magnitude gap of at least 2 mag R between the first and the second ranked member within half of the virial radius), each having good quality X-ray data and Sloan Digital Sky Survey (SDSS) spectroscopic or photometric coverage out to the virial radius. The poor cluster AWM 4 is clearly established as a fossil system, and we confirm the fossil nature of four other systems (RX J1331.5+1108, RX J1340.6+4018, RX J1256.0+2556 and RX J1416.4+2315), while the cluster RX J1552.2+2013 is disqualified as fossil system. For all systems, we present the luminosity functions within 0.5 and 1 virial radius that are consistent, within the uncertainties, with the universal luminosity function of clusters. For the five bona fide fossil systems, having a mass range 2 × 1013 –3 × 1014 M⊙ , we compute accurate cumulative substructure distribution functions (CSDFs) and compare them with the CSDFs of observed and simulated groups/clusters available in the literature. We demonstrate that the CSDFs of fossil systems are consistent with those of normal observed clusters and do not lack any substructure with respect to simulated galaxy systems in the cosmological Λ cold dark matter (ΛCDM) framework. In particular, this holds for the archetype fossil group RX J1340.6+4018 as well, contrary to earlier claims. 相似文献
590.
Evan S. Gawlik Jerrold E. Marsden Philip C. Du Toit Stefano Campagnola 《Celestial Mechanics and Dynamical Astronomy》2009,103(3):227-249
This study investigates Lagrangian coherent structures (LCS) in the planar elliptic restricted three-body problem (ER3BP),
a generalization of the circular restricted three-body problem (CR3BP) that asks for the motion of a test particle in the
presence of two elliptically orbiting point masses. Previous studies demonstrate that an understanding of transport phenomena
in the CR3BP, an autonomous dynamical system (when viewed in a rotating frame), can be obtained through analysis of the stable
and unstable manifolds of certain periodic solutions to the CR3BP equations of motion. These invariant manifolds form cylindrical
tubes within surfaces of constant energy that act as separatrices between orbits with qualitatively different behaviors. The
computation of LCS, a technique typically applied to fluid flows to identify transport barriers in the domains of time-dependent
velocity fields, provides a convenient means of determining the time-dependent analogues of these invariant manifolds for
the ER3BP, whose equations of motion contain an explicit dependency on the independent variable. As a direct application,
this study uncovers the contribution of the planet Mercury to the Interplanetary Transport Network, a network of tubes through
the solar system that can be exploited for the construction of low-fuel spacecraft mission trajectories.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献