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排序方式: 共有57条查询结果,搜索用时 31 毫秒
1.
Management of summer-spawning herring off Iceland 总被引:1,自引:0,他引:1
2.
Anantha Chanumolu Sivarani Thirupathi Damien Jones Sunetra Giridhar Deon Grobler Robert Jakobsson 《Experimental Astronomy》2017,43(1):39-58
As a continuation to the published work on model based calibration technique with HESP(Hanle Echelle Spectrograph) as a case study, in this paper we present the performance results of the technique. We also describe how the open parameters were chosen in the model for optimization, the glass data accuracy and handling the discrepancies. It is observed through simulations that the discrepancies in glass data can be identified but not quantifiable. So having an accurate glass data is important which is possible to obtain from the glass manufacturers. The model’s performance in various aspects is presented using the ThAr calibration frames from HESP during its pre-shipment tests. Accuracy of model predictions and its wave length calibration comparison with conventional empirical fitting, the behaviour of open parameters in optimization, model’s ability to track instrumental drifts in the spectrum and the double fibres performance were discussed. It is observed that the optimized model is able to predict to a high accuracy the drifts in the spectrum from environmental fluctuations. It is also observed that the pattern in the spectral drifts across the 2D spectrum which vary from image to image is predictable with the optimized model. We will also discuss the possible science cases where the model can contribute. 相似文献
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The field relationships and petrographic features of the oceanites of the Reykjanes peninsula suggest that they might have originated as primary magmas. The principal phase relationships of primary liquids formed by the partial melting of lherzolites are defined. The phase relations obtained for oceanite RE78 between 0 and 30 kbar at dry conditions suggest that the oceanite originated as a primary magma at 25 kbar and 1580°C, and erupted at a temperature near 1300°C. 相似文献
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N. R. Tanvir A. J. Levan E. Rol R. L. C. Starling J. Gorosabel R. S. Priddey D. Malesani P. Jakobsson P. T. O'Brien A. O. Jaunsen J. Hjorth J. P. U. Fynbo A. Melandri A. Gomboc B. Milvang-Jensen A. S. Fruchter M. Jarvis C. A. C. Fernandes T. Wold 《Monthly notices of the Royal Astronomical Society》2008,388(4):1743-1750
Gamma-ray bursts (GRBs) are powerful probes of the early Universe, but locating and identifying very distant GRBs remain challenging. We report here the discovery of the K -band afterglow of Swift GRB 060923A, imaged within the first hour post-burst, and the faintest so far found. It was not detected in any bluer bands to deep limits, making it a candidate very high- z burst ( z ≳ 11) . However, our later-time optical imaging and spectroscopy reveal a faint galaxy coincident with the GRB position which, if it is the host, implies a more moderate redshift (most likely z ≲ 2.8 ) and therefore that dust is the likely cause of the very red-afterglow colour. This being the case, it is one of the few instances so far found of a GRB afterglow with high-dust extinction. 相似文献
8.
Bijoy Thompson Jonas Nycander Johan Nilsson Martin Jakobsson Kristofer Döös 《Ocean Dynamics》2014,64(6):797-807
A simple method for estimating ventilation time scales from overturning stream functions is proposed. The stream function may be computed using either geometric coordinates or a generalized vertical coordinate, such as potential density (salinity in our study). The method is tested with a three-dimensional circulation model describing an idealized semi-enclosed ocean basin ventilated through a narrow strait over a sill, and the result is compared to age estimates obtained from a passive numerical age tracer. The best result is obtained when using the stream function in salinity coordinates. In this case, the reservoir-averaged advection time obtained from the overturning stream function in salinity coordinates agrees rather well with the mean age of the age tracer, and the corresponding maximum ages agree very well. 相似文献
9.
Partial melting experiments on a San Carlos peridotite were done in a Walker type multi-anvil press at pressures from 5 to
12.5 GPa. Experiments were done in the presence of a COH-fluid and at oxygen fugacity controlled by the Fe–FeO buffer. Olivine,
clinopyroxene, garnet and orthopyroxene are stable in all but the highest temperature 10 GPa experiments where olivine and
garnet coexist, and the highest temperature 5 GPa experiments where olivine is the single crystalline phase. The solidus at
5 GPa was found to be at approximately 1,200°C and the liquidus was estimated to be at 1,325°C, which is ∼500°C lower than
has been reported for dry melting of peridotite. The aluminum concentration of the melts decreases with increasing melt fraction
and decreases also with increasing pressure. At 5 GPa the melts have a CaO/Al2O3-ratio of 0.85–1.0, which is similar to that of undepleted komatiites; major element concentrations are also identical to
those of undepleted komatiites such as the Munro komatiites. At 10 and 12.5 GPa the partial melts have CaO/Al2O3-ratios above 1.5 and major element composition almost identical to aluminum depleted komatiites such as the Barberton komatiites.
We therefore conclude that in the presence of a reducing COH-fluid both aluminum-depleted and -undepleted komatiites could
have formed at temperatures much lower than generally accepted. 相似文献
10.
Two different methods of estimating the water exchange through the Baltic coastal region of Laxemar have been used, consisting of particle trajectories and passive tracers. Water is traced from and to a small discharge region near the coast. The discharge material in this region is treated as zero-dimensional particles or tracers with neutral buoyancy. The real discharge material could be a leakage of radio-nuclides through the sea floor from an underground repository of nuclear waste.Water exchange rates between the discharge region and the model domain are estimated using both forward and backward trajectories as well as passive tracers. The Lagrangian trajectories can account for the time evolution of the water exchange while the tracers give one average age per model grid box. Water exchange times such as residence time, age and transient times have been calculated with trajectories but only the average age (AvA) for tracers. The trajectory calculations provide a more detailed time evolution than the tracers.On the other hand the tracers are integrated “on-line” simultaneously in the sea circulation model with the same time step while the Lagrangian trajectories are integrated “off-line” from the stored model velocities with its inherent temporal resolution, presently 1 h. The sub-grid turbulence is parameterised as the Laplacian diffusion for the passive tracers and with an extra stochastic velocity for trajectories. The importance of the parameterised sub-grid turbulence for the trajectories is estimated to give an extra diffusion of the same order as the Laplacian diffusion by comparing the Lagrangian dispersions with and without parameterisation. The results of the different methods are similar but depend on the chosen diffusivity coefficient with a slightly higher correlation between trajectories and tracers when integrated with a lower diffusivity coefficient. 相似文献