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51.
We found a hydrodynamic pulsation model of yellow supergiants under subharmonic resonance. It is confirmed that the feature of pulsation by the resonance is long-lived in the model by performing the hydrodynamical simulation for a long time. 相似文献
52.
Otto Mellis 《Mineralogy and Petrology》1954,4(1-4):138-144
Ohne ZusammenfassungMit 3 Textabbildungen. 相似文献
53.
Otto Wittmann 《International Journal of Earth Sciences》1941,32(3):337-367
Ohne Zusammenfassung 相似文献
54.
55.
Earlier analyses of the Pioneer 8 and 9 experimental meteoroid data have shown that the detectors on these two spacecraft are intercepting meteoroids with hyperbolic orbital parameters. It is shown in this paper that these results are entirely consistent with and, indeed, to be expected from other observations of the interplanetary meteoroid complex. Collisional breakup of meteoroids and post-collision radiation pressure modification of their orbits is found to be a sufficient cause for the observed results. Details of the calculations as well as of the results are presented. 相似文献
56.
Effect of land management on ecosystem carbon fluxes at a subalpine grassland site in the Swiss Alps 总被引:1,自引:0,他引:1
N. Rogiers W. Eugster M. Furger R. Siegwolf 《Theoretical and Applied Climatology》2005,80(2-4):187-203
Summary The influence of agricultural management on the CO2 budget of a typical subalpine grassland was investigated at the Swiss CARBOMONT site at Rigi-Seebodenalp (1025m a.s.l.) in Central Switzerland. Eddy covariance flux measurements obtained during the first growing season from the mid of spring until the first snow fall (17 Mai to 25 September 2002) are reported. With respect to the 10-year average 1992–2001, we found that this growing season had started 10 days earlier than normal, but was close to average temperature with above-normal precipitation (100–255% depending on month). Using a footprint model we found that a simple approach using wind direction sectors was adequate to classify our CO2 fluxes as being controlled by either meadow or pasture. Two significantly different light response curves could be determined: one for periods with external interventions (grass cutting, cattle grazing) and the other for periods without external interventions. Other than this, meadow and pasture were similar, with a net carbon gain of –128±17g Cm–2 on the undisturbed meadow, and a net carbon loss of 79±17g Cm–2 on the managed meadow, and 270±24g Cm–2 on the pasture during 131 days of the growing season, respectively. The grass cut in June reduced the gross CO2 uptake of the meadow by 50±2% until regrowth of the vegetation. Cattle grazing reduced gross uptake over the whole vegetation period (37±2%), but left respiration at a similar level as observed in the meadow. 相似文献
57.
The influence of an internal boundary layer and a roughness sublayer on flux–profile relationships for momentum and sensible heat have been investigated for a closed beech forest canopy with limited fetch conditions. The influence was quantified by derivation of local scaling functions for sensible heat flux and momentum (h and m) and analysed as a function of atmospheric stability and fetch. For heat, the influences of the roughness sublayer and the internal boundary layer were in agreement with previous studies. For momentum, the strong vertical gradient of the flow just above the canopy top for some wind sectors led to an increase in m, a feature that has not previously been observed. For a fetch of 500 m over the beech forest during neutral atmospheric conditions, there is no height range at the site where profiles can be expected to be logarithmic with respect to the local surface. The different influence of the roughness sublayer on h and m is reflected in the aerodynamic resistance for the site. The aerodynamic resistance for sensible heat is considerably smaller than the corresponding value for momentum. 相似文献
58.
The first results of a comprehensive computer analysis of over 300 front film and grid coincidence events is presented using statistical tests on the observed data. The short term time dependence of the observed flux is entirely commensurate with a random Poisson distribution and any possible contributions from discrete “cometary showers” must certainly be of relatively minor significance compared to the sporadic background for mass > 10?13 g. Periodic seasonal variations of ~ 20 per cent of the average rate are observed common to Pioneers 8 and 9. These variations could reflect on the cometary nature of the source or alternatively indicate the presence of an interstellar component. The mass spectrum of the flux in the range 10?11?10?13 g indicates an increasing flux of particles to the lowest limits of mass detected, with a derived flux of Φ = 1·4 × 10?12m?0·68 (g) m?2 sec?1(2π ster.)?1. 相似文献
59.
Edwin GNOS Silvio LORENZETTI Otto EUGSTER A. J. Timothy JULL Beda A. HOFMANN Ali Al‐KATHIRI Manuel EGGIMANN 《Meteoritics & planetary science》2009,44(3):375-387
Abstract— The recently discovered Jiddat al Harasis (JaH) 073 strewn field is the largest found so far in the Sultanate of Oman, covering an area of 19 × 6 km. The 3463 single stones collected range in weight from 52.2 kg down to <1 g (total weight 600.8 kg) and show a pronounced mass sorting. The strewn field shape can be approximated by a NW‐SE‐oriented ellipsoid, indicating an atmospheric entry from SE at a low angle relative to the surface. The meteorite belongs to the L6 ordinary chondrite group and shows S4 average shock grade. Smaller stones generally show a higher weathering grade resulting in a spread from W2 and W4. Enhanced weathering of the stones causing fragmentation after the fall is observed in sandy depressions. Five 14C measurements on stones of variable size and weathering grade yielded 14C from 3.8 to 49.9 dpm/kg. Three samples give a 14C/ 10Be age consistent with about 14.4 ka. For two samples the cosmogenic, trapped, and radiogenic noble gases were measured. The ratio of the 4He and 40Ar gas retention ages of 0.29 ± 0.10 and that of the 3He and 21Ne cosmic ray exposure ages of 0.36 ± 0.08 Ma indicate that JaH 073 experienced a complex exposure history and lost 4He and 40Ar due to a major collision. Fragmentation statistics indicate a single major atmospheric disruption and an originally relatively spherical shape of the object. Assuming the material collected represents the majority of fallen mass, and 90–99% of the original weight was lost by ablation, the pre‐atmospheric minimum radius of the meteoroid with density 3.4 g cm?3would have been at least 75 cm. 相似文献
60.
Zusammenfassung Es muss unterschieden werden zwischen den (scheinbaren) Minimalhöhen der F2-Schicht und jenen Höhen, in denen sich das Miximum der Elektronenkonzentration befindt. Es wird gezeist, dass sich für Statinen in Aequatornähe diese beiden Gebiete der F2-Schicht ganz verschieden verhalten; aus der Tatsache, dass die untere Begrenzung mit zunehmender Sonnentätigkeit abwts sinkt, während gleichzeitig die Höhe für die maximale Elektronenkonzentration anwächst, wird auf eine Veränderung der Schichtdicke geschlossen, die von der wechselnden Sonnenaktivität étroite avec l'activité solaire.
Résumé La distinction entre la hauteur virtuelle minimum de la couche F2 et la hauteur vituelle où se trouve le maximum de la concentration 'eléctronique est nécessaire. On Montre que ces deux régions sont tré différentes pour les stations situées près de l'équateur. Etant donné que la base de la couche F2 s'abaisse pendant la période de croissance du cycle solaire, tandis que la hauteur de la concentraion éléctronique du maximmum augmente, on en conclu que l'épaisseur est soumis à des variations en relation étroite avec l'activité solaire.相似文献