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131.
Surging of the southwestern part of the Laurentide Ice Sheet 总被引:1,自引:0,他引:1
LEE CLAYTON JAMES T. TELLER JOHN W. ATTIG 《Boreas: An International Journal of Quaternary Research》1985,14(3):235-241
The southwestern part of the Laurentidc Ice Sheet, in central North America, repeatedly surged during the last part of the Wisconsin Glaciation. Evidence includes the extreme lobation of the ice margin, the gentle slopes of lateral moraines and other marginal features, a radiocarbon chronology indicating extremely rapid marginal advance and retreat, and the abundance of supraglacial flow till. Rapid ice movement was caused by subglacial water and was probably limited to areas of slowly permeable substrate, which slowed the escape of the water. 相似文献
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The Hwacheon granulite complex (HGC), occupying the northeasternmargin of the Gyeonggi massif, consists mainly of garnetiferousleucocratic gneiss and leucogranite together with minor kyanitegarnetgneiss, aluminous gneiss, mafic granulite and garnet amphibolite.Mineral assemblages and reaction textures in various rock typesof the HGC document five distinct metamorphic stages: pre- (M1)and peak (M2) granulite-facies metamorphism; lower temperature,high (M3) and low (M4) pressure upper amphibolite-facies metamorphism;and local retrogression (M5) producing andalusite-bearing assemblages.Each metamorphic stage can be integrated to give a compositePT path consisting of two distinct trajectories, characterizedby clockwise PT loops at relatively high and low temperatures,respectively. The first PT trajectory (M1M3) correspondsto a Palaeoproterozoic tectonometamorphic event responsiblefor the formation of the granulite complex at 相似文献
134.
JONATHAN R. LEE JAMES ROSE JAMES B. RIDING BRIAN S. P. MOORLOCK RICHARD J. O. HAMBLIN 《Boreas: An International Journal of Quaternary Research》2002,31(4):345-355
The provenance of the Happisburgh Till and Corton Till of the Corton Formation is investigated using erratic clast lithologies and allochthonous palynomorphs to test whether the long held assumption that they were deposited by ice that originated in Scandinavia is valid. The results show a wide range of lithologies including Carboniferous Limestone and Coal Measures, and Permian Magnesian Limestone that are not found in Scandinavia, and an absence of distinctive Scandinavian material such as rhomb porphyry and larvikite. Lithologies found indicate deposition by an ice sheet which flowed southwards into north-east East Anglia from central and southern Scotland eroding and transporting materials derived from outcrops in these areas and from eastern England and the western margins of the southern North Sea Basin. It is concluded that the long held assumption that the Happisburgh Till and Corton Till of the Corton Formation were deposited by a Scandinavian ice sheet is erroneous and that they were instead deposited by Scottish ice. 相似文献
135.
LEE Byung-SuDepartment of Earth Science Education Chonbuk National University Jeonju - Korea Zhu Xiling 《《地质学报》英文版》2002,76(2):155-165
This paper presents a conodont biostratigraphic study on the Upper Cambrian Sesong and Hwajeol Formations in the Sabuk area, Korea. Two samples near the base of the Sesong Slate at the Pukil section contain lower Upper Cambrian conodonts, comprising Furnishina furnishi, F. kranzae, F. pernical, F. triangulate, Hertzina elongata, Laiwugnathus doidyxus?, Phakelodus elongatus, Muellerodus? obliquus, Westergaardodina matsushitai and W. moessebergensis. This is the first conodont record of the Upper Cambrian formations recovered yet in the northern limb of the Paekunsan syncline. The faunal assemblage is correctable with the lower Upper Cambrian W. matsushitai Zone of North China. Four local biozones are recognized in the Hwajeol Formation, i.e. the Proconodontus, Eoconodontus notchpeakensis, Cambrooistodus minutus and Cordylodus proavus Zones in ascending order. This zonal scheme is essentially equivalent to that of the southern limb of the Paekunsan syncline and they are correlatable with zones in other pa 相似文献
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Kenichi HOSHINO Yuki YAMAMOTO Xiangping GU Su Young LEE Makoto WATANABE 《Resource Geology》2000,50(3):185-190
Abstract: Possible ore deposition by fluid mixing was preliminarily examined using MIX 99, a FORTRAN program developed for simulating water-rock interactions. We consider mixing of two fluids, the low fO2 and high temperature source fluid and the high fO2 and low temperature seawater. Oxygen fugacity of a mixed fluid formed by titration of seawater into the source fluid gradually decreases with decreasing temperature (model A). Sequential precipitation of ore-forming minerals was examined in this model. On the other hand, simultaneous precipitation of the minerals could be followed by simulation of instantaneous overall mixing of the two fluids (model B). Results of simulation of the both models revealed that a temporal sequence of mineralization observed in the Karuizawa mine, NE Japan, can be formed by model A, while model B is suitable for the mineralization of an active chimney found in the Rainbow hydrothermal area of the Mid-Atlantic Ridge. 相似文献
139.
研究大气折射率起伏对雷达波的散射时,得到的主要結果有以下两点: 1.在适当的大气条件下,折射率起伏构成的后向散射波能够超出一般雷达的灵敏度之上,它的量級正好和雷达观測到的气象“仙波”相同.根据这一結果和其他事实,作者认为起伏的后向散射可能是形成气象“仙波”的重要机制。 2.推导了表示雷达波在折射率有起伏的介貭中传播时,强度随距离变化的方程式,結果发現:一般情况下,散射效应不致引起波的强度的显著变化.但是,当大气折射率起伏的尺度长較小、輻度較大、并且雷达波瓣較窄时,散射效应会引起波瓣的加寬。 相似文献
140.
Incorporation of parameter uncertainty into spatial interpolation using Bayesian trans-Gaussian kriging 总被引:2,自引:0,他引:2
Quantitative precipitation estimation(QPE) plays an important role in meteorological and hydrological applications.Ground-based telemetered rain gauges are widely used to collect precipitation measurements. Spatial interpolation methods are commonly employed to estimate precipitation fields covering non-observed locations. Kriging is a simple and popular geostatistical interpolation method, but it has two known problems: uncertainty underestimation and violation of assumptions.This paper tackles these problems and seeks an optimal spatial interpolation for QPE in order to enhance spatial interpolation through appropriately assessing prediction uncertainty and fulfilling the required assumptions. To this end, several methods are tested: transformation, detrending, multiple spatial correlation functions, and Bayesian kriging. In particular, we focus on a short-term and time-specific rather than a long-term and event-specific analysis. This paper analyzes a stratiform rain event with an embedded convection linked to the passing monsoon front on the 23 August 2012. Data from a total of 100 automatic weather stations are used, and the rainfall intensities are calculated from the difference of 15 minute accumulated rainfall observed every 1 minute. The one-hour average rainfall intensity is then calculated to minimize the measurement random error. Cross-validation is carried out for evaluating the interpolation methods at regional and local levels. As a result,transformation is found to play an important role in improving spatial interpolation and uncertainty assessment, and Bayesian methods generally outperform traditional ones in terms of the criteria. 相似文献