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671.
Abstract While beginning to establish a German Civil GPS Information and Observation Service in 1990, the actual and (near) future GPS market in Germany was analyzed. In addition, the feasibility of using GPS for water authority tasks has been studied during past years. Typical capabilities in this area are real‐time positioning for hydrographic surveying (kinematic application) and precise transfer of levels to tide gauges and verification at offshore positions. The article describes the user interests, the requirements, some of the test campaigns, and the derived concepts for future applications. 相似文献
672.
David van Acken Harry Becker William F. McDonough Richard D. Ash 《Geochimica et cosmochimica acta》2010,74(2):661-6182
Pyroxenitic layers are a minor constituent of ultramafic mantle massifs, but are considered important for basalt generation and mantle refertilization. Mafic spinel websterite and garnet-spinel clinopyroxenite layers within Jurassic ocean floor peridotites from the Totalp ultramafic massif (eastern Swiss Alps) were analyzed for their highly siderophile element (HSE) and Os isotope composition.Aluminum-poor pyroxenites (websterites) display chondritic to suprachondritic initial γOs (160 Ma) of −2 to +27. Osmium, Ir and Ru abundances are depleted in websterites relative to the associated peridotites and to mantle lherzolites worldwide, but relative abundances (Os/Ir, Ru/Ir) are similar. Conversely, Pt/Ir, Pd/Ir and Re/Ir are elevated.Aluminum-rich pyroxenites (clinopyroxenites) are characterized by highly radiogenic 187Os/188Os with initial γOs (160 Ma) between +20 and +1700. Their HSE composition is similar to that of basalts, as they are more depleted in Os, Ir and Ru compared to Totalp websterites, along with even higher Pt/Ir, Pd/Ir and Re/Ir. The data are most consistent with multiple episodes of reaction of mafic pyroxenite precursor melts with surrounding peridotites, with the highest degree of interaction recorded in the websterites, which typically occur in direct contact to peridotites. Clinopyroxenites, in contrast, represent melt-dominated systems, which retained the precursor melt characteristics to a large extent. The melts may have been derived from a sublithospheric mantle source with high Pd/Ir, Pt/Ir and Re/Os, coupled with highly radiogenic 187Os/188Os compositions. Modeling indicates that partial melting of subducted, old oceanic crust in the asthenosphere could be a possible source for such melts.Pentlandite and godlevskite are identified in both types of pyroxenites as the predominant sulfide minerals and HSE carriers. Heterogeneous HSE abundances within these sulfide grains likely reflect subsolidus processes. In contrast, large grain-to-grain variations, and correlated variations of HSE ratios, indicate chemical disequilibrium under high-temperature conditions. This likely reflects multiple events of melt-rock interaction and sulfide precipitation. Notably, sulfides from the same thick section for the pyroxenites may display both residual-peridotite and melt-like HSE signatures. Because Totalp pyroxenites are enriched in Pt and Re, and depleted in Os, they will develop excess radiogenic 187Os and 186Os, compared to ambient mantle. These enrichments, however, do not possess the requisite Pt-Re-Os composition to account for the coupled suprachondritic 186Os-187Os signatures observed in some Hawaiian picrites, Gorgona komatiites, or the Siberian plume. 相似文献
673.
Christopher I. Massey Vernon Manville Graham H. Hancox Harry J. Keys Colin Lawrence Mauri McSaveney 《Landslides》2010,7(3):303-315
The summit crater of Mt Ruapehu volcano normally hosts a 15.4-ha warm lake, whose water has been repeatedly wholly or partly
ejected by explosive and extrusive eruptions. Some of the larger eruptions have modified the lake outlet by burying it under
unconsolidated tephra (volcanic ash and blocks), creating a dam-break flood hazard independently of the occurrence of an eruption.
Eruptions in 1995 and 1996 followed this sequence; a break-out flood was anticipated and a warning system was installed to
mitigate the risk from this event and subsequent lahars in the same catchment. The 11-year filling time allowed much planning
and rehearsal. The warning system involved manual inspections of dam integrity, and seepage and lake-level monitoring to constrain
the likely failure window, and telemetered instruments including a tripwire and geophones to detect breaching of the dam and
propagation of the outbreak flood. The dam-collapse sequence, captured by a time-lapse camera, involved a series of retrogressing
landslides initiated and accelerated by seepage forces and toe scour when the lake was 1.1 m below overtopping. The barrier
failed in two phases on 18th March, 2007, beginning at 09:55 (NZST), with rapid retreat of one of the erosion scarps on the
downstream slope of the eastern barrier, initiated by internal erosion. Headward retrogression of the scarp into the barrier
formed an initial breach in the dam, after which increasing outflow led to erosion and undercutting of the wider downstream
toe of the western barrier. A final, larger dam breach occurred between 11:21 and 11:22 as slope instability caused retrogressive
failure of the remaining barrier. Five-hundred meters downstream of the dam, a large landslide was reactivated by toe scour
during the flood, contributing about a million cubic meters of solid material to the volumetric bulking of the outflow, which
reached the coast, 215 km away, 17 h later. The success of the planning and warning system allowed the whole event to occur
with little damage to infrastructure and without causing injury. 相似文献