全文获取类型
收费全文 | 104篇 |
免费 | 6篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 2篇 |
地球物理 | 22篇 |
地质学 | 57篇 |
海洋学 | 3篇 |
天文学 | 15篇 |
综合类 | 1篇 |
自然地理 | 13篇 |
出版年
2021年 | 1篇 |
2017年 | 1篇 |
2014年 | 1篇 |
2013年 | 12篇 |
2012年 | 7篇 |
2011年 | 2篇 |
2010年 | 3篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2006年 | 1篇 |
2005年 | 4篇 |
2004年 | 6篇 |
2003年 | 5篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1998年 | 1篇 |
1997年 | 11篇 |
1996年 | 9篇 |
1995年 | 3篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1970年 | 1篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有114条查询结果,搜索用时 15 毫秒
101.
Mineral Chemistry and Crystallization Conditions of the Mboutou Layered Gabbro-Syenite-Granite Complex, North Cameroon 总被引:3,自引:0,他引:3
The Mboutou complex is one of a line of early Tertiary ringcomplexes which runs from Lake Chad to the Gulf of Guinea, noneof which has hitherto been described in detail. The main rocktypes are layered gabbros and gabbronorites, with minor bodiesof quartz-syenodiorite, quartz-syenite and hypersolvus granite.Feldspars form a continuum with exceptional compositional range,from An85Ab13Or2 to around An1Ab46Or55, and form an entirelyhypersolvus sequence with very strong zoning in the syenodiorites.Ca-rich clinopyroxenes (salite and calcic augite) and olivines(Fo7862) have restricted range. Orthopyroxene-bearingleucogabbros and syenodiorites contain minor orthopyroxene (En62Fs35Wo3)and quartz; olivine and orthopyroxene never coexist. In moreevolved rocks amphibole (magnesio-hornblende to ferroedenite)and minor biotite, showing progressive Fe-enrichment, are theonly mafic silicates.Major-element rock chemistry, minor elementsin clinopyroxenes and biotite chemistry show that, notwithstandingits thoroughly anorogenic setting, Mboutou was, at the outset,only very mildly alkaline. Its more evolved members embarkedon a line of evolution with some calc-alkaline characteristics,probably because of ingress of water into residual batches ofmagma, a possibility supported by stable isotope data. Thischange in behaviour corresponded with the sudden appearanceof quartz and orthopyroxene, which was not in equilibrium withclinopyroxene on the two-pyroxene surface. Amphibole then becamethe main mafic silicate with further increase in . The more evolved rocks are relatively highly altered,but Fe-Ti oxide pairs suggest that was maintained near to and above the QFM buffer and the rangeof biotite compositions further suggests crystallization undera regime of decreasing . Biotites maintain alkaline characteristics throughout the sequence. Zoningpatterns in the ternary feldspars in the syenodiorites, andthe hypersolvus character of the final granite, limit maximumvalues of to < 1 kb, and suggest minimum temperatures for the end of crystallizationin the syenodiorites of{small tilde} 850 ?C. 相似文献
102.
The problem of deriving an optimal set of thermodynamic propertiesof minerals from a diverse experimental data base is reviewedand a preferred methodology proposed. Mathematical pro-gramming(MAP)methods extend the linear programming (LIP) approach first presentedby Gordon (1973), and make it possible to account for the typeof information conveyed, and the uncertainties attending bothphase equilibrium data and direct measurements of phase properties.For phase equilibrium data which are (in most cases) characterizedby non-normal error distributions across experimental brackets,the midpoint of a bracket is no more probable than other points,and the data are best treated by considering the inequalityin the change in Gibbs free energy of reaction at each half-bracket.Direct measurements of phase properties can be assumed to haveapproximately normal error distributions, and the MAP techniqueoptimizes agreement with these values by using the principlesof least squares in the definition of an objective function.The structure of this problem, treatment of uncertainties invarious types of experimental data, and method of optimizingfinal solutions are discussed in some detail.The method is appliedto experimental data in the MgO-SiO2-H2O system, where inconsistenciesamong the data are resolved and an optimal set of thermodynamicproperties is presented. The derived standard state entropiesand volumes agree with all direct measurements (within theiruncertainties), as do enthalpies of formation from the elementsexcept for those of talc (+16 kJ mol1), anthophyllite(+ 14 kJ mol1), and brucite (1 kJ mol1).Stable phase relations in the system have the topology predictedby Greenwood (1963, 1971), with quartz- and forsterite-absentinvariant points at 683 ?C-6-4 kb and 797 ?C-12 kb respectively,repeating at 552 ?C-120 b and 550 ?C-55 b. The thermodynamicanalysis indicates little remaining flexibility in the phaserelations, which, when combined with suitable activity modelsfor solid solution, should allow for accurate determinationof the conditions of metamorphism of ultramafic rocks. 相似文献
103.
A.R. BROWN R.M. WRIGHT K.D. BURKART W.L. ABRIEL R.G. McBEATH 《Geophysical Prospecting》1986,34(5):623-647
Synergism of 3-D seismic data, wavelet processing, colour display and interactive interpretation has been exploited in the study of a Gulf of Mexico gas reservoir. Seismic amplitude has been used as a measure of the proportion of a sand/shale reservoir capable of producing gas. This has led to the mapping of net producible thickness of gas sand. The tuning phenomena resulting from geometric effects alone were studied in detail, and tuning curves of various levels of sophistication were used as the basis for amplitude editing. Statistical tuning curves were derived by interactive cross-plotting and deterministic curves by wavelet extraction. Multiple wavelet side lobes cause multiple maxima in the tuning curve. Depositional effects and intrareservoir communication have also been studied by interactive cross-plotting. 相似文献
104.
MORAES R.; BROWN M.; FUCK R. A.; CAMARGO M. A.; LIMA T. M. 《Journal of Petrology》2002,43(9):1673-1705
Sapphirinequartz occurs in orthopyroxenegarnetgranulites in two areas 相似文献
105.
A correlation between the crossite component (NaM4) in Ca-amphiboleand pressure of metamorphism has long been recognized (Shido& Miyashiro, 1959), but only recently has the reaction beenidentified which buffers this aspect of amphibole composition(Brown, 1974): Ca-amphibole+iron oxide+albite+chloriteI+H2O (±stilp,qtz) = crossite+epidote (±muscovite, qtz). The exact stoichiometry of the reaction depends on compositionalvariables in the minerals, especially Fe2+/Mg and Fe3+/Al. Ca-amphiboleshould have fixed NaM4, at any given T and P, where it coexistswith iron oxide, albite, and chlorite. Comparison of Ca-amphibole composition with mineral assemblage,in rocks from Otago, N.Z., and elsewhere, supports this hypothesis.In any terrane NaM4 is nearly constant at a particular metamorphicgrade where amphibole exists in the buffering assemblage, butvaries widely outside of this assemblage. Variations in Fe2+/Mgand Fe3+/Al in the amphibole have relatively little effect onNaM4, but in high pressure amphiboles NaM4 varies inverselywith Aliv. Ca-amphiboles from high pressure areas have substantially moreNaM4 (Otago, 0.6 of 2.0) than those from lower pressure areas(Sierra contact aureoles, 0.1). These relations suggest thatin the buffering assemblage, the NaM4 content of Ca-amphiboleshould be a useful relative barometer for low to medium grademetamorphic rocks. 相似文献
106.
ANNE HORMES NAKI AKÇAR PETER W. KUBIK 《Boreas: An International Journal of Quaternary Research》2011,40(4):636-649
Hormes, A., Akçar, N. & Kubik, P. W. 2011: Cosmogenic radionuclide dating indicates ice‐sheet configuration during MIS 2 on Nordaustlandet, Svalbard. Boreas, 10.1111/j.1502‐3885.2011.00215.x. ISSN 0300‐9483.0300‐9843 Glacial geological field surveys, aerial image interpretation and cosmogenic radionuclide (CRN) dating allowed us to reconstruct the ice‐sheet configuration on Nordaustlandet, the northernmost island of the European sector on the margin of the Arctic Ocean. The timing of deglaciation was investigated by determining the 26Al and 10Be ages of glacially scoured bedrock, weathered periglacial blockfields and glacial erratic boulders. Only 10Be ages were useful for our interpretations, because of unresolved analytical problems with 26Al. Fjords and lowlands on Nordaustlandet yielded Late Weichselian 10Be ages, indicating that actively erosive ice streams scoured the coastal fjord bathymetry during marine isotope stage (MIS) 2. In Murchisonfjorden, ground‐truthed air‐photograph interpretation and 10Be ages of boulders indicated a cold‐based glacier ice cover during MIS 2 on higher plateaus. 10Be ages and lithological studies of erratic boulders on higher and interior plateaus of Prins Oscars Land (>200–230 m a.s.l.) suggest that the Mid‐Weichselian glaciation (MIS 4) might have been more extensive than that during MIS 2. 相似文献
107.
WARREN G. A. KEENAN F. P. GREER C. J. PHILLIPS K. J. H. BRUNER M. E. BROWN W. A. McKENZIE D. L. 《Solar physics》1997,171(1):93-102
We have calculated intensity ratios for emission lines of Fexviii in the 13–94 Å wavelength range at electron temperatures characteristic of the solar corona, T
e = 2–10 x 106 K. Our model ion includes data for transitions among the 2s
22p
5 , 2s2p
6, 2s
22p
43l, and 2s2p
53l (l = s, p, and d) states. Test calculations which omit the 2s2p
53l levels show that cascades from these are important. We compare our results with observed ratios determined from four solar X-ray instruments, a rocket-borne spectrograph, and spectrometers on the P78–1, OV1–17 and Solar Maximum Mission (SMM) satellites. In addition, we have generated synthetic spectra which we compare directly with flare observations from SMM. Agreement between theory and observation is generally quite good, with differences that are mostly less than 30%, providing limited support for the accuracy of the atomic physics data used in our calculations. However, large discrepancies are found for ratios involving the 2s
22p
5
2P3/2- 2s2p
6
2S line at 93.84 Å, which currently remain unexplained. Our analysis indicates that the FeXVIII feature at 15.83 Å is the 2s
22p
5
2P3/2 - 2s
22p
4(3P)3s 4P3/2 transition, rather than 2s
22p
5
2P3/2 - 2s
22p
4(3P)3s 2P3/2, as suggested by some authors. 相似文献
108.
109.
110.
R. DAVID DALLMEYER MICHAEL BROWN RICHARD S. D'LEMOS ROBIN A. STRACHAN 《Journal of Metamorphic Geology》1993,11(1):137-154
Abstract The St Malo region in north-west France contains migmatites and anatectic granites derived by partial melting of metasedimentary protoliths during Cadomian orogenesis at c. 540 Ma. Previously reported Rb–Sr model ages for muscovite and biotite range from c. 550 to c. 300 Ma, and suggest variable resetting of mineral isotopic systems. These rocks display microscopic evidence for variably intense Cadomian intracrystalline plastic strain but record no obvious evidence of penetrative Palaeozoic regional deformation. 40Ar/39Ar mineral ages have been determined to evaluate better the extent, timing and significance of Palaeozoic overprinting. Eleven muscovite concentrates and one whole-rock phyllite have been prepared from various units exposed in the St Malo and adjacent Mancellian regions. In the Mancellian region, muscovite from two facies of the Bonnemain Granite Complex record 40Ar/39Ar plateau ages of c. 527 and 521 Ma. An internally discordant 40Ar/39Ar release spectrum characterizes muscovite from protomylonitic granite within the Cadomian Alexain-Deux Evailles-Izé Granite Complex, and probably records the effects of Variscan displacement along the North Armorican Shear Zone. Muscovite concentrates from anatectic granite and from Cadomian mylonites along ductile shear zones within the north-western sector of the St Malo region exhibit internally discordant 40Ar/39Ar release spectra which suggest variable and partial late Palaeozoic rejuvenation. By contrast, muscovite concentrates from samples of variably mylonitic Brioverian metasedimentary rocks exposed within the south-eastern sector of the St Malo region display internally concordant apparent age spectra which define plateaux of 326–320 Ma. A whole-rock phyllite sample from Brioverian metasedimentary rocks exposed along the eastern boundary of the St Malo region displays an internally discordant argon release pattern which is interpreted to reflect the effects of a partial late Palaeozoic thermal overprint. Muscovite from the Plélan granite, part of the Variscan Plélan-Bobital Granite Complex, yields a 40Ar/39Ar plateau age of c. 307 Ma. The 40Ar/39Ar results indicate that Cadomian rocks of the St Malo region have undergone a widespread and variable Palaeozoic (Carboniferous) rejuvenation of intracrystalline argon systems which apparently did not affect the Mancellian region. This rejuvenation was not accompanied by penetrative regional deformation, and was probably of a static thermal–hydrothermal origin. The heat source for rejuvenation was probably either the result of heating during Variscan extension or advection from Variscan granites which are argued to underlie the St Malo region. 相似文献