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221.
Lorenzo Casertano 《Pure and Applied Geophysics》1956,33(1):177-186
Riassunto Si analizzano andamenti sperimentali della luminosità del cielo nelle zone rossa e bleu dello spettro. Dal confronto con diversi
andamenti teorici si ottiene la spiegazione per la diversità di comportamento della luminosità nelle due zone considerate,
e si riconosce la possibilità che — sotto certe condizioni — è consentito tener conto della sola diffusione primaria. Considerando
anche la diffusione non molecolare si indica un metodo per calcolare, dalle misure di luminosità, il valore di un parametro
che rappresenta un indice del contenuto di polveri nell’atmosfera. Si discutono alcuni valori trovati in base a misure eseguite
all’Osservatorio Vesuviano.
Prof.Lorenzo Casertano, Osservatorio Vesuviano,Resina (Napoli) 相似文献
Summary Experimental outlines of sky brightness in the red and blue fields of spectrum are analized. From comparison with theoretical predictions one desumes the explanation about the different behaviour of brightness in the two considered fields and possibility — under certain conditions — of taking account only primary scattering. Considering also non-molecular scattering a method is shown to deduce, from the measurements of intensities of sky radiation, the value of a parameter representing the content of dust into atmosphere. Some experimental values found in measurements made at the ? Osservatorio Vesuviano ? are discussed.
Prof.Lorenzo Casertano, Osservatorio Vesuviano,Resina (Napoli) 相似文献
222.
223.
Phillip J. Clapham Simon Childerhouse Nicolas J. Gales Lorenzo Rojas-Bracho Michael F. Tillman Robert L. Brownell Jr. 《Marine Policy》2007
Morishita's “multiple analysis” of the whaling issue [Morishita J. Multiple analysis of the whaling issue: Understanding the dispute by a matrix. Marine Policy 2006;30:802–8] is essentially a restatement of the Government of Japan's whaling policy, which confuses the issue through selective use of data, unsubstantiated facts, and the vilification of opposing perspectives. Here, we deconstruct the major problems with Morishita's article and provide an alternative view of the whaling dispute. For many people in this debate, the issue is not that some whales are not abundant, but that the whaling industry cannot be trusted to regulate itself or to honestly assess the status of potentially exploitable populations. This suspicion has its origin in Japan's poor use of science, its often implausible stock assessments, its insistence that culling is an appropriate way to manage marine mammal populations, and its relatively recent falsification of whaling and fisheries catch data combined with a refusal to accept true transparency in catch and market monitoring. Japanese policy on whaling cannot be viewed in isolation, but is part of a larger framework involving a perceived right to secure unlimited access to global marine resources. Whaling is inextricably tied to the international fisheries agreements on which Japan is strongly dependent; thus, concessions made at the IWC would have potentially serious ramifications in other fora. 相似文献
224.
S. de Lorenzo 《Pure and Applied Geophysics》1998,153(2-4):419-438
—Among Q-estimation methods a simple linear technique consists of the evaluation of the increasing rise time of body waves with the increase of their travel time. This method, known as the rise time method, was theoretically justified for an impulsive source time function (Dirac delta function). Wu and Lees (1996), throughout finite difference calculations, showed that, when considering finite source time functions, characterized by a cut-off frequency around 20 Hz, the rise time method can be satisfactorily applied to invert earthquake data.¶In order to establish the applicability of the rise time method to an arbitrary earthquake source we analytically solved the problem of the propagation, throughout an anelastic medium, of a signal generated by a finite dimensions seismic source the shear dislocation fault of Brune (1970). Analyzing theoretical rise time vs. travel-time curves, we were able to distinguish two different corner frequency ranges in which the trend is different. When corner frequency is below 10 Hz the discrepancies with the rise time method increase with a decrease of the corner frequency. When corner frequency is above 10 Hz no meaningful differences are observed.¶The application of the model to a synthetic data set, based on the sources-receivers configuration of the 15 November 1995 Border Town, Nevada, earthquake sequence, shows that a significant bias affects Q estimates obtained with the rise time method, for seismic events characterized by a Brune corner frequency less than 5 Hz. 相似文献
225.
Michel Jébrak Pablo L. Higueras Éric Marcoux Saturnino Lorenzo 《Mineralium Deposita》2002,37(5):421-432
The Nuevo Entredicho deposit contains the richest concentration of mercury in the Almadén district, locally grading as much as 45% Hg. This ore deposit is hosted within an alkaline, conically shaped diatreme, about 150 m in diameter, which was subsequently filled with phreatomagmatic breccias. The diatreme cuts an Ordovician to Silurian clastic sedimentary rock sequence that is intercalated with basaltic sills. Structural analysis reveals a complex tectonic history with three main phases of Hercynian deformation. Mineralisation occurs as cinnabar replacements in volcanic tuffs and breccias and as recrystallised veins in tensions cracks associated with pyrophyllite and hydrothermal pyrite, which is strongly enriched in Cu, Pb and Hg. Lead isotopes in pyrite are characterised by high 207Pb/204Pb ratios (15.70-15.75), suggesting a contribution of ancient upper continental crust remobilised by Silurian-Devonian volcanism, with no mantle involvement. Sulphur isotopes of epigenetic cinnabar and pyrite range from +10.3 to +10.8 and from +10.6 to +11.9 respectively, suggesting a uniform sulphur source or a constant mixing ratio in the ore fluids. These isotopic compositions differ from those measured in the syngenetic deposits of the Almadén district; they suggest a higher temperature of ore formation of about 300 °C, and a genesis related to a distinct hydrothermal flow path at the Nuevo Entredicho deposit. Deposition of anomalously high-grade mercury ore at Nuevo Entredicho is related to a combination of (1) an abundance of black shale that provided sulphur and increasingly reducing conditions with high sulphide/sulphate ratios, (2) explosive Silurian-Devonian mafic magmatism that provided an initial source of mercury, (3) tectonic activity that lead to structurally favourable sites for ore deposition, and (4) replacement of secondary, carbonate-rich volcanic rocks. 相似文献
226.
227.
Sonia Scarselli Guy D. H. Simpson Philip A. Allen Giorgio Minelli Lorenzo Gaudenzi 《地学学报》2007,19(1):74-81
The Marche Apennines (Italy) offer an excellent opportunity to constrain the temporal and spatial relationships between drainage network formation and tectonic activity. Using a combination of field data, seismic lines and boreholes we show that the main deformation phase took place during the Messinian when the area, affected by the Messinian sea level drop, emerged and evolved from marine to continental conditions. The results highlight that during the Messinian emersion a drainage network developed contemporaneously with an increase in tectonic activity that could be related to sea level fall and river erosion. The present‐day river system, which is dominated by transverse rivers that cut straight across the tectonic grain, is located in older Messinian palaeovalleys, even though the region was subsequently covered by water until the late Pliocene–early Pleistocene. 相似文献
228.
Gaussian beam depth migration overcomes the single‐wavefront limitation of most implementations of Kirchhoff migration and provides a cost‐effective alternative to full‐wavefield imaging methods such as reverse‐time migration. Common‐offset beam migration was originally derived to exploit symmetries available in marine towed‐streamer acquisition. However, sparse acquisition geometries, such as cross‐spread and ocean bottom, do not easily accommodate requirements for common‐offset, common‐azimuth (or common‐offset‐vector) migration. Seismic data interpolation or regularization can be used to mitigate this problem by forming well‐populated common‐offset‐vector volumes. This procedure is computationally intensive and can, in the case of converted‐wave imaging with sparse receivers, compromise the final image resolution. As an alternative, we introduce a common‐shot (or common‐receiver) beam migration implementation, which allows migration of datasets rich in azimuth, without any regularization pre‐processing required. Using analytic, synthetic, and field data examples, we demonstrate that converted‐wave imaging of ocean‐bottom‐node data benefits from this formulation, particularly in the shallow subsurface where regularization for common‐offset‐vector migration is both necessary and difficult. 相似文献
229.
Lorenzo Iorio 《Astrophysics and Space Science》2008,318(1-2):51-55
The fast spinning B-star Regulus has recently been found to be orbited by a fainter companion in a close circular path with orbital period P b=40.11(2) d. Being its equatorial radius R e 32% larger than the polar one R p, Regulus possesses a remarkable quadrupole mass moment Q. We investigate the effects of Q on the orbital period P b of its companion in order to see if they are measurable, given the present-day level of accuracy in measuring P b. Conversely, we will look for deviations from the third Kepler law, attributed to the quadrupole mass moment Q of Regulus, to constrain the ratio γ=m/M of the system’s masses. The impact of Q on the orbital period is analytically worked out with a straightforward perturbative approach. The resulting correction P Q is compared to other competing dynamical effects. P Q and the Keplerian period P Kep are expressed in terms of the phenomenologically determined system’s parameters; γ is treated as an unknown. P Q is compared to the observational accuracy in measuring the orbital period δ P b=0.02 d and to the systematic uncertainty δ(P Kep) due to the errors in the system’s parameters entering it. The discrepancy ΔP=|P b?P Kep| is examined in order to see for which values of γ it becomes statistically significant. The physical meaning of the obtained range of values for γ is discussed in terms of Q. P Q is larger than δ P b but still smaller than the systematic uncertainty in P Kep by two orders of magnitude. The major sources of bias are the velocity semiamplitude K of the motion of the primary and its mass M. Assuming edge-on configuration, i.e. i=90 deg, if γ?0.096 Q would be positive, i.e. Regulus would be prolate, contrary to the observations. If γ?0.078 Q would be negative, but its magnitude would be one-two orders of magnitude larger than the approximate estimate Q≈M(R p 2 ?R e 2 )=?2.4±0.5×1049 kg?m2. Regulus is the first extrasolar binary system in which the orbital effects of the asphericity of the primary are larger than the observational sensitivity; moreover, no other competing aliasing orbital effects are present. Thus, it is desirable that it will become the object of future intensive observational campaigns in order to reduce the systematic uncertainty due to the system’s parameters below the measurability threshold. 相似文献
230.
In this paper we determine the tidal distortion parameter km of the secondary partner (mass loser) of the semi-detached eclipsing binary system V621 Cen by comparing the phenomenologically determined orbital period Pb=3.683549(11) d to the Keplerian one PKep computed with the values of the relevant system’s parameters determined independently of the third Kepler law itself. Our result is km=-1.5±0.6. Using the periastron precession, as traditionally done with other eclipsing binaries in eccentric orbits, would have not been possible because of the circularity of the V621 Cen path. 相似文献