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991.
Late-Stage Mafic Injection and Thermal Rejuvenation of the Vinalhaven Granite, Coastal Maine 总被引:11,自引:0,他引:11
WIEBE R. A.; MANON M. R.; HAWKINS D. P.; McDONOUGH W. F. 《Journal of Petrology》2004,45(11):2133-2153
The Vinalhaven intrusive complex consists mainly of coarse-grainedgranite, inward-dipping gabbrodiorite sheets, and a fine-grainedgranite core. Small bodies of porphyry occur throughout thecoarse-grained granite. The largest porphyry body (roughly 0·5km by 2·5 km) occurs with coeval gabbro, hybrid rocks,and minor fine-grained granite in the Vinal Cove complex, whichformed during the waning stages of solidification of the coarse-grainedVinalhaven granite. Porphyry contacts with surrounding coarse-grainedgranite are irregular and gradational. Compositions of wholerocks and minerals in the porphyry and the coarse-grained graniteare nearly identical. Neighboring phenocrysts in the porphyryvary greatly in degree of corrosion and reaction, indicatingthat the porphyry was well stirred. Thermal rejuvenation ofa silicic crystal mush by a basaltic influx can explain thecomposition and texture of the porphyry. Comparable rejuvenationevents have been recognized in recent studies of erupted rocks.Weakly corroded biotite phenocrysts in the porphyry requirethat hydrous interstitial melt existed in the granite duringremelting. Field relations, along with thermal calculations,suggest that cooling and crystallization of coeval mafic magmacould have generated the porphyry by thermal rejuvenation ofgranite crystal-mush containing about 20% melt. Field relationsalso suggest that some of the porphyry matrix may representnew felsic magma that was emplaced during remelting. KEY WORDS: granite; magma chamber; mafic replenishment; rejuvenation 相似文献
992.
Denis M. Shaw 《Geochimica et cosmochimica acta》1974,38(10):1607-1613
R-mode factor analysis on 11 specimens of 9 enstatite chondrites, analysed for Ga, Se, Te, Zn, Cd, Bi, Tl, In, Sb, As, Co, showed three factors (rotated) to account for 92 per cent of the elemental variations (variance).Factor 1 dominates the first 8 elements listed, all volatile and mostly chalcophile: factors 2 and 3 express Sb and As variations, respectively, probably dependent on siderophile and less volatile behaviour; factors 1 and 2 contribute to Co.Factor-scores for individual meteorites indicate compositional differences (for these elements) between the E4 as against E5 and E6 stones (which are indistinguishable).Factor analysis of a second suite of 10 specimens analysed for Zn, Cd, Bi, Tl, In, Ag, Rb, Cs showed one factor to account for 93 per cent of the elemental variance. This expresses the association of Ag, Rb, Cs with the volatile-chalcophile factor. 相似文献
993.
Detailed geological and petrological-geochemical study of rocks of the lava complex of Young Shiveluch volcano made it possible
to evaluate the lava volumes, the relative sequence in which the volcanic edifice was formed, and the minimum age of the onset
of eruptive activity. The lavas of Young Shiveluch are predominantly magnesian andesites and basaltic andesites of a mildly
potassic calc-alkaline series (SiO2 = 55.0–63.5 wt %, Mg# = 55.5–68.9). Geologic relations and data on the mineralogy and geochemistry of rocks composing the
lava complex led us to conclude that the magnesian andesites of Young Shiveluch volcano are of hybrid genesis and are a mixture
of silicic derivatives and a highly magnesian magma that was periodically replenished in the shallow-depth magmatic chamber.
The fractional crystallization of plagioclase and hornblende at the incomplete segregation of plagioclase crystals from the
fractionating magmas resulted in adakitic geochemical parameters (Sr/Y = 50–71, Y < 18 ppm) of the most evolved rock varieties.
Our results explain the genesis of the rock series of Young Shiveluch volcano without invoking a model of the melting of the
subducting Pacific slab at its edge. 相似文献
994.
M.F. BENEDETTI A.M. DE KERSABIEC J. BOULEGUE 《Geostandards and Geoanalytical Research》1987,11(1):127-129
After acid digestion, gold is extracted with MIBK and determinated by flameless atomic absorption spectrometry. The results for six USGS reference samples and fourteen French geochemical standards are presented and discussed. The agreement with working values for these standards is in the range of pm 5%. 相似文献
995.
Systematic research over years on datable horizons of lower Miocene age has led to an election of nine glauconite samples suitable for dating work. The chosen glauconites come from various regions of the tethys. Following careful sedimentological as well as stratigraphical studies the K-Ar ages of these glauconites were measured. The interpretation of the apparent ages found takes into consideration sedimentation, mineralogical quality and present knowledge of the genesis of the green glauconite pellets. The presented data allow to fix the basis of the Miocene at about 21–22 m. y. and the boundary of Aquitanian-Burdigalian at 18 m. y. The K-Ar data on glauconites presented here are in good agreement with newer measurements of other authors on high temperature minerals of the same age span. 相似文献
996.
A. Iu. Iurchenko N. Takahata K. Tanaka Y. Sano N. S. Balushkina G. A. Kalmykov 《Moscow University Geology Bulletin》2016,71(6):466-471
Dispersed and concretionary pyrite in chert–clay–carbonate and carbonate rocks of the Abalak Formation (Salym oil field) have been studied. The study was conducted using Scanning Electron Microscopy (SEM), Electron Probe Microanalysis (EPMA), and high spatial resolution Secondary Ion Mass Spectrometry (Nano-SIMS). As a result, three morphological groups of pyrite have been distinguished: large cubic crystals, framboidal pyrite, and fine-crystal aggregates that replace organic remnants. The sulphur isotope ratio allows one to distinguish two genetic types of pyrite. The source of the sulphur for the first genetic group was H2S produced by bacterial sulphate reduction, while the second group pyrite was formed with sulphur as a product of thermochemical sulphate reduction. 相似文献
997.
G. Samudro B. Eng. M. Eng. S. Mangkoedihardjo B. Eng. M.Sc. E.S. Ph.D. 《International Journal of Environmental Science and Technology》2006,3(3):261-267
This paper proposed a simple method and rapid to carry out for organizing city phytostructure. Carbon dioxide sequestration was addressed and referred to population number instead of city area. The unit storage of carbon dioxide, which was nothing less than greenspace area, was determined using equivalent method of determining unit storage of water. For various population number (P) of city area in Indonesia, the greenspace unit (GU) was 29P?0.3 ? 3.2, and the greenspace area (GA) was 29P07–3.2P. Greenspace distribution was preferably on wetlands, river lines, top ground level, and north south direction. 相似文献
998.
999.
N. N. Eremin R. A. Talis A. E. Grechanovskii V. S. Urusov 《Moscow University Geology Bulletin》2013,68(2):72-78
An original methodology for the atomistic computer modeling of solid solutions was applied for the study of the mixing properties and local structure of the grossular-uvarovite, i.e., Ca3Al2[SiO4]3 Ca3Cr2][SiO4]3, garnet series. The parameters of the interatomic potentials for end members of this series were optimized using experimental data on their structural, elastic, and thermodynamic characteristics. The optimized model of the potentials allowed us to describe the elastic, structural, and thermodynamic characteristics of grossular and uvarovite and estimate the energy of point defects in these crystal structures. Calculations of the mixing properties and local structure for seven different compositions of the solid solution were carried out on a “Chebyshev” supercomputer (Moscow State University) in a 2 × 2 × 4 supercell of the garnet-type structure containing 2560 atoms. Mixing properties, such as the enthalpy of mixing, parameters of interaction, excess mixing volume, deviation of bulk modulus from additivity, and the vibrational and configuration contribution to the entropy of mixing, were determined. This allowed us to estimate the stability field for the grossular-uvarovite solid solution. Histograms of the interatomic distances M-O (M = Ca, Al, Cr, Si) and O-O in supercells were plotted and the parameters of relaxation and changes of the CrO6 and AlO6 octahedron volumes were estimated. The data of the simulation are quite consistent with the experimental data on this system and supplement it significantly. 相似文献
1000.
The pressure dependence of the zirconium-in-rutile thermometer 总被引:19,自引:1,他引:19
The solubility of ZrO2 in rutile is strongly temperature-dependent and has been identified as a potentially powerful thermometer when the rutile coexists with an appropriate buffer assemblage, e.g. zircon + quartz. In combination with experimental data at 10 kbar, previous consideration of data on natural rutile has not identified a pressure dependence for the thermometer. However, the expected volume change as a result of substitution of the larger Zr4+ cation for Ti4+ suggests that the Zr content of rutile should decrease with increasing pressure. To investigate the pressure dependence of the thermometer, piston cylinder (at 10, 20 & 30 kbar) and 1 atm furnace experiments were performed in the system ZrO2 -TiO2 -SiO2 . The solubility of ZrO2 in rutile, in the presence of zircon and quartz was reversed at each pressure value. From these experiments, the thermodynamics of the end-member reaction ZrSiO4 = SiO2 + ZrO2 (in rutile) have been determined. There is a secondary pressure effect accompanying the primary temperature dependence of the Zr content of rutile. New thermometer equations are, in the α -quartz field: in the β -quartz field and in the coesite field in which φ is ppm Zr, P is in kbar and R is the gas constant, 0.0083144 kJ K−1 . Thermometric results using these equations are shown for a range of geological settings. 相似文献