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61.
George E Harlow Jeremy S Delaney C.E Nehru Martin Prinz 《Geochimica et cosmochimica acta》1982,46(3):339-348
The high modal abundances of merrillite [Ca3(PO4)2] and tridymite in most mesosiderites are not the result of igneous fractionation but are attributed to redox reactions between silicates and P-bearing Fe-Ni metal within a limited T-fO2 range at low pressure. The Emery mesosiderite is the most tridymite- and merrillite-rich mesosiderite so it is used as the model for this study. Examination of reactions in the system CaO-SiO2-MgSiO3-Fe-P-O indicate that essentially all of the present phosphorus in Emery should have been dissolved in the metallic portion (calculated to have contained 0.65 wt% P originally), and that it largely reacted to form phosphate. The thermodynamic calculations predict that the reactions would have occurred between 970°C, log fO2 = ?16.5 and 1030°C, log fO2 = ?15.0 for the range of phase compositions in Emery. A narrower range of conditions is expected for other mesosiderites. Phosphide (schreibersite) formed only later at temperatures < 600°C during slow cooling. The recalculated amounts of dissolved P and S in the metallic portion of Emery reduce the temperature of the metal liquidus to < 1350°C and the solidus to < 800°C. Thus mixing of liquid metal with cold silicates near the parent body's surface would not have resulted in substantial melting of the silicates but would have resulted in their metamorphism, which is consistent with the textural relationships observed in Emery. This scenario of redox reactions and redistributions of components between metal and silicates represents a new insight into the complexities of mesosiderite processing that helps unravel the mesosiderite history and recalculate their original components. 相似文献
62.
Electron microprobe analyses yielded mean values of for primary-textured phlogopites in coarse, depleted garnet-lherzolite xenoliths from kimberlites. Most secondary-textured phlogopites have too low Cl (0.01–0.08 wt.%) to be metamorphic precursors of primary-textured phlogopites. MARID-suite phlogopites and many megacrysts in kimberlites have low Cl (), and some but not necessarily all secondary micas may result from infiltration of kimberlite into peridotite xenoliths. A good correlation between P and F in some oceanic basalts and gabbros might suggest that these elements are derived mainly from F-rich apatite inthe mantle, and that whitlockite is not present in the source region. Mantle-derived mica and amphibole have such low Cl that it is necessary to attribute Cl in oceanic basalts and gabbros either to substantial Cl in the source apatite, or to Cl from invading solutions, or both: three apatites from the mantle contain 0.8–1.0 wt.% Cl, and others contain lower amounts. The halogen contents of kimberlitic magmas can be explained by incorporation of Cl-bearing mica and F-rich apatite during melting of peridotites, but compositional constraints are weak. 相似文献
63.
64.
G. G. C. Palumbo N. Mandolesi G. Morigi G. A. Baird T. Delaney W. P. S. Meikle R. W. P. Drever J. V. Jelley J. H. Fruin R. B. Partridge 《Astrophysics and Space Science》1978,54(2):355-363
Between 1972 and 1975 an international collaborative search was carried out for prompt 10 GHz emission at the onset of supernovae. The motivations and techniques involved in this effort are described, and the results of the three years' work are summarized. No pulses from supernovae were detected, the best upper limit being 4×1043 ergs in a 40 MHz band at 10 GHz for a pulse time-scale 0.5 s. Methods for improving this limit are briefly described. 相似文献
65.
David W. Muenow Diana G. Graham Norman W.K. Liu John R. Delaney 《Earth and Planetary Science Letters》1979,42(1):71-76
High-temperature mass spectrometric studies have been made to determine the distribution of volatiles within glassy rims of submarine pillow basalts dredged from the east rift zone of Kilauea volcano, Hawaii. The CO2/H2O mole ratio for glass-vapor inclusions within olivine phenocrysts in the glassy rims is greater than 30 : 1 compared to 0.06 for matrix glasses. Enclosing matrix glasses contain 0.53–0.74 wt.% H2O, 0.02–0.04 wt.% carbon, 0.08–0.12 wt.% sulfur, 0.012–0.028 wt.% chlorine and 0.012–0.077 wt.% fluorine. 相似文献
66.
J. B. Dawson J. S. Delaney J. V. SmitH 《Contributions to Mineralogy and Petrology》1978,67(2):189-193
Megacrysts of titanian pyrope, high-Ti bronzite, sub-calcic diopside to augite, and phlogopite in an alnöitic breccia, Malaita, Solomon Islands, have compositional features which distinguish them from silicates in kimberlites. Particularly important is the high content of Al2O3 in the Malaita silicates, which may reflect the higher Al2O3 content of alnöite than kimberlite. The phlogopite megacrysts fall into two populations, one richer in Mg and Cr, and lower in Ti, than the other. The pyroxenes may also fall into two groups characterized by high and low Mg, Cr and Ni. Two stages of crystallization may be responsible. 相似文献
67.
Margaret Lois Delaney Allan W.H.Bé Edward A. Boyle 《Geochimica et cosmochimica acta》1985,49(6):1327-1341
Constant-temperature laboratory culture experiments of the planktonic foraminiferal species Globigerinoides sacculifer (Brady) suggest that the ratios of Li and Sr to Ca in the shells are a function of these ratios in the culture solutions. and in the shells did not vary with changes of these ratios in the culture solution. These are the first direct determinations of the relationship between foraminiferal shell chemistry and solution composition.The possibility of temperature dependence for the minor elemental composition of foraminiferal shells was also investigated in the laboratory and by analysis of several planktonic and one benthic foraminiferal species from sediment trap and sediment core samples. The , , and ratios in the natural samples roughly correlate with calcification temperature, whereas differences in the Li/Ca ratios are small and not systematically related to temperature. However, laboratory culture experiments at 20°C and 30°C showed no variation in the , , , and ratios with calcification temperature for the planktonic foraminifera G. sacculifer and Orbulina universa. Therefore, observed differences in the , , and ratios for the sediment trap and core foraminiferal samples cannot be ascribed to direct effects of calcification temperature, but may be due to some other environmental factor which is correlated with temperature. 相似文献
68.
The July 2007 rock and ice avalanches at Mount Steele, St. Elias Mountains, Yukon, Canada 总被引:1,自引:0,他引:1
Panya S. Lipovsky Stephen G. Evans John J. Clague Chris Hopkinson Réjean Couture Peter Bobrowsky Göran Ekström Michael N. Demuth Keith B. Delaney Nicholas J. Roberts Garry Clarke Andrew Schaeffer 《Landslides》2008,5(4):445-455
A large rock and ice avalanche occurred on the north face of Mount Steele, southwest Yukon Territory, Canada, on July 24,
2007. In the days and weeks preceding the landslide, several smaller avalanches initiated from the same slope. The ice and
rock debris traveled a maximum horizontal distance 5.76 km with a maximum vertical descent of 2,160 m, leaving a deposit 3.66 km2 in area on Steele Glacier. The seismic magnitude estimated from long-period surface waves (M
s) is 5.2. Modeling of the waveforms suggests an estimated duration of approximately 100 s and an average velocity of between
35 and 65 m/s. This landslide is one of 18 large rock avalanches known to have occurred since 1899 on slopes adjacent to glaciers
in western Canada. We describe the setting, reconstruct the event chronology and present a preliminary characterization of
the Mount Steele ice and rock avalanches based on field reconnaissance, analysis of seismic records and an airborne LiDAR
survey. We also present the results of a successful dynamic simulation for the July 24 event. 相似文献
69.
O. Eugster Ch. Thalmann A. Albrecht G. F. Herzog J. S. Delaney J. Klein R. Middleton 《Meteoritics & planetary science》1996,31(2):299-304
Abstract— Glass-rich separates were prepared from a sample of the basaltic lunar meteorite EET87521 rich in dark glass. Noble gas isotopic abundances and 26Al and 10Be activities were measured to find out whether shock effects associated with lunar launch helped to assemble these phases. Similar 10Be and 26Al activities indicate that all materials in EET87521 had a common exposure history in the last few million years before launch. However, the glass contains much higher concentrations of trapped gases and records a much longer cosmic-ray exposure, 100 Ma–150 Ma, in the lunar regolith than does the bulk sample. The different histories show that the glass existed long before the ejection of EET87521. The trapped 40Ar/36Ar ratio of 1.6 ± 0.1 implies that the lunar exposure that produced most of the stable cosmogenic noble gases began 500 Ma ago. Cosmogenic and trapped noble gas components correlate strongly in various temperature-release fractions and phases of EET87521, which is probably because the glass contains most of the gas. The trapped solar ratios, 20Ne/22Ne = 12.68 ± 0.20 and 36Ar/38Ar = 5.24 ± 0.05 can be understood as resulting from a mixture consisting of ~60% solar wind and 40% solar energetic particles (SEP). All EET87521 phases show a 40K-40Ar gas retention age of ~3300 Ma, which is in the range of typical lunar mare basalts. 相似文献
70.
Brent D. Turrin Fara Lindsay Jeremy S. Delaney Jisun Park Gregory F. Herzog Carl Swisher Jr Cyrena A. Goodrich 《Meteoritics & planetary science》2023,58(3):304-327
The Almahata Sitta (AhS) meteorite consists of disaggregated clasts from the impact of the polymict asteroid 2008 TC3, including ureilitic (70%–80%) and diverse non-ureilitic materials. We determined the 40Ar/39Ar release patterns for 16 AhS samples (3–1500 μg) taken from three chondritic clasts, AhS 100 (L4), AhS 25 (H5), and MS-D (EL6), as well as a clast of ureilitic trachyandesite MS-MU-011, also known as ALM-A, which is probably a sample of the crust of the ureilite parent body (UPB). Based on our analyses, best estimates of the 40Ar/39Ar ages (Ma) of the chondritic clasts are 4535 ± 10 (L4), 4537–4555 with a younger age preferred (H5), and 4513 ± 17 (EL6). The ages for the L4 and the H5 clasts are older than the most published 40Ar/39Ar ages for L4 and H5 meteorites, respectively. The age for the EL6 clast is typical of older EL6 chondrites. These ages indicate times of argon closure ranging up to 50 Ma after the main constituents of the host breccia, that is, the ureilitic components of AhS, reached the >800°C blocking temperatures of pyroxene and olivine thermometers. We suggest that these ages record the times at which the clasts cooled to the Ar closure temperatures on their respective parent bodies. This interpretation is consistent with the recent proposal that the majority of xenolithic materials in polymict ureilites were implanted into regolith 40–60 Ma after calcium–aluminum-rich inclusion and is consistent with the interpretation that 2008 TC3 was a polymict ureilite. With allowance for its 10-Ma uncertainty, the 4549-Ma 40Ar/39Ar age of ALM-A is consistent with closure within a few Ma of the time recorded by its Pb/Pb age either on the UPB or as part of a rapidly cooling fragment. Plots of age versus cumulative 39Ar release for 10 of 15 samples with ≥5 heating steps indicate minor losses of 40Ar over the last 4.5 Ga. The other five such samples lost some 40Ar at estimated times no earlier than 3800–4500 Ma bp . Clustering of ages in the low-temperature data for these five samples suggests that an impact caused localized heating of the AhS progenitor ~2.7 Ga ago. In agreement with the published work, 10 estimates of cosmic-ray exposure ages based on 38Ar concentrations average 17 ± 5 Ma but may include some early irradiation. 相似文献