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111.
THOMAS PERMUTT Department of Epidemiology Preventive Medicine University of Marylan W.Baltimore St Baltimore MD U.S.A.STEVEN D.EDLAND Biostatistics Department University of Washington Seattle WA U.S.A.MITHRA MOEZZI Department of Statistics University of Californi Berkeley CA U.S.A.STELLA C.GROSSER Division of Biostatistics University of Californi Los Angeles CA U.S.A. 《地理学报(英文版)》1991,(3)
Techniques for testing for and estimating relative bias between two laboratories are developed andapplied to a survey of the chemistry of streams in the United States.The design of the quality assuranceprogram allows estimation of linear corrections for bias as well as testing of the hypothesis of linearity,Designs of this type are useful,but improvements are suggested. 相似文献
112.
Towards a National Landslide Information Base for New Zealand 总被引:6,自引:0,他引:6
Landslides constitute a problem as a natural hazard, as a factor in land development decisions, and as a major process in the depletion of New Zealand's soil resource. There are compelling social, economic, and legislative reasons for obtaining and accessing information on landslide activity. As a way of improving a currently weak information base, recommendations are given for establishing an information system appropriate to specific management functions. 相似文献
113.
Dacite Genesis via both Slab Melting and Differentiation: Petrogenesis of La Yeguada Volcanic Complex, Panama 总被引:20,自引:2,他引:20
DEFANT MARC J.; RICHERSON PHIL M.; DE BOER JELLE Z.; STEWART ROBERT H.; MAURY REN? C.; BELLON HERV?; DRUMMOND MARK S.; FEIGENSON MARK D.; JACKSON THOMAS E. 《Journal of Petrology》1991,32(6):1101-1142
La Yeguada volcanioc complex (LYVC) is one of many major volcanoesthat represent the extension of the Central American arc inwestern Panama and that have resulted from current oblique subductionsouth of Panama. There are two major phases of calc-alkalinevolcanic activity at LYVC based on mapping and K-Ar radiometricdates. The first phase began at {small tilde} 13 Ma and ceasedat {small tilde} 7?5 Ma. This sequence, termed the old group,consists of basalts to rhyolites with typical arc mineralogies(OL, CPX, PL, MGT, and OPX). The samples have similar radiogenicSr and Nd values and appear to be related by fractional crystallizationwith assimilation and/or magma mixing involved in the differentiation.The parental basalts were probably derived from the metasomatizedmantle wedge via melting induced by fluids released from thesubducted lithosphere. There was an apparent period of minor volcanic activity from75 to 25 Ma (only one documented sample from thisperiod). The second phase (<2?5 Ma), termed the young group,consists only of dacites but with very different mineralogies(PL, MGT, AM, BI, with no PX) and geochemistries (e.g., highSr and low Y and HREE) compared with the old-group dacites (andandesites and rhyolites). The dacites cannot be related to theold group by various petrogenetic modeling techniques. Thesehigh-Al dacites have the characteristics of magmas derived fromthe partial melting of the subducted oceanic lithosphere witha hornblende eclogite residuum. This has been substantiatedby geochemical modeling. Samples similar to the young-group dacites in other arcs havebeen termed adakites and arc associated with the subductionof young hot crust which may explain why the slab melts. ThePanama basin has extremely high heat flow values, comparablewith those of the Galapagos ridge system. The change from normalarc volcanism to adakites suggests that the subducted oceaniccrust became hotter as time progressed. The subduction of anoceanic ridge or new ridge development along the Sandra Riftin the Panama basin can explain the change in volcanism withtime but more geophysical data are needed. 相似文献
114.
Data collected in a dipole-dipole sounding along a crooked line can be transformed to form an approximately equivalent Schlumberger sounding, using a simple matrix inversion technique. The equivalent curve can be interpreted using rapid interpretation methods. 相似文献
115.
The Pleistocene to Holocene Honolulu Volcanic Series was eruptedfrom about 37 vents scattered over the older Koolau tholeiiteshield. The rocks of this series are compositionally zoned withrespect to the shield; near the Koolau caldera the predominantrocks are melilitenepheline basalts, but these give way outwardto nepheline basalts, and ultimately, at the apron of the shield,to alkalic olivine basalts. The xenoliths in these are likewisezoned: most of those in the caldera area consist of dunite,most of those at intermediate distances of lherzolite, and someof those in the apron of the shield consist of garnet pyroxeniteand peridotite. The zoning of the xenoliths, however, does notcoincide with that of the enclosing rocks. We believe that copiouseruption of Koolau tholeiite produced a lateral and verticalheterogeneity in the mantle beneath Oahu, and that the zoningin both Honolulu lavas and their xenoliths is caused by thatheterogeneity. The textures of the xenoliths indicate that thebasalts were mainly produced by fractional melting rather thanfractional crystallization. There is some evidence that thedunite xenoliths are mantle residua produced during the generationof the tholeiite, and that the Honolulu magmas were generatedat greater depths than the Koolau magmas, probably as a resultof elastic unloading. 相似文献
116.
During the last few years a substantial improvement has been made in the development of the thermal infra-red scanner so that 1.5 milli-radian resolution is now commonly obtained. Direct transfer of information on 70 mm film through fiber glass transcoder allows immediate and refined interpretation. Although the collected data represent the image of thermal anomalies within a pellicular section of the earth's crust, it is proved that because of “per ascensum” phenomena, deep buried sources induce surface thermal changes. The difficulty lies in showing an absolute relationship between these deep phenomena and thermal surface occurrences. A careful examination of several cases related to hydrology, karstic geology, civil engineering, pollution, hot springs should help the geophysicist by providing him a new tool for shallow investigations. Thermographics with interpretation are shown to support this statement. 相似文献
117.
In general terms the form of the Bride Moraine, its internal structure, and part of its stratigraphy result from a minor ice-sheet readvance during a late stage of the Devensian deglaciation of the Irish Sea basin. Four major structural styles are identified and are related to four structural zones that run parallel to the crest of the ice-thrust ridge. The structures result from the development of differential permafrost in a sequence of highly contrasting lithologies and the consequent generation of high pore-water pressures during ice-marginal loading. This caused mobilisation of water-saturated clays in the sequence and the development of large-scale diapiric structure in the core of the moraine and low-angles overthrust faulting on the flanks. 相似文献
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