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711.
Legislation to decarbonise energy systems within overall greenhouse gas reduction targets represents an immense and unprecedented energy policy challenge. However there is a dichotomy between this level of policy ambition and prior modelling studies that find such targets economically, technologically and socially feasible under idealised ?Dfirst-best policies. This paper makes a significant contribution to current analytical efforts to account for realistic ?Dsecond-best climate mitigation policy implementation. This is achieved via a technical classification of secondbest common mode issues at a detailed national level: both internal (behavioural change, infrastructure implementation) and external (new technologies, resource availability). Under a combinatory second-best scenario, meeting targets greater than a 70% reduction in CO2 by 2050 entail costs above a subjective barrier of 1% of GDP, while extreme mitigation scenarios (>90% CO2 reduction) are infeasible. These high costs are equally due to disappointing progress in behavioural and technological mitigation efforts. Expensive second-best mitigation scenarios can still rely on extreme assumptions including the full deployment of the UK??s offshore wind resource or the complete diffusion of energy efficiency measures in end-use sectors. By demonstrating the fragilities of a low carbon energy system pathway, policy makers can explore protective and proactive strategies to ensure targets can actually be met. Additionally, systematic analysis of failure in stringent long term decarbonisation scenarios teaches energy analysts about the trade-offs in model efficacy vs. confidence. 相似文献
712.
713.
Climate change impacts and adaptation of commercial marine fisheries in Australia: a review of the science 总被引:2,自引:0,他引:2
Commercial marine fishing contributes significantly to the Australian economy, and has great importance for coastal communities. However, climate change presents significant challenges for Australia’s fishing industries, now and into the future. With greater use of targeted information, the fishing industry will be better placed to minimise the negative impacts and take advantage of opportunities associated with the effects of climate change. The future of the fishing industry—specifically wild capture fisheries—will depend on its ability and capacity to apply appropriate adaptation strategies for its viability and sustainability in the long-term. Knowledge regarding expected long-term changes in species distributions, improved weather and seasonal climate forecasts and their influence on target species, and better understanding of species tolerances, can inform adaptation responses. This paper provides a review of recent advances in research addressing Australia’s priorities in relation to commercial marine fisheries’ responses to current and anticipated future climate change impacts, and considers barriers and adaptation options for fisheries management over the near-term planning horizon of 5–7 years. 相似文献
714.
Suspended sediment fluxes in a tidal wetland: Measurement, controlling factors, and error analysis 总被引:1,自引:0,他引:1
Suspended sediment fluxes to and from tidal wetlands are of increasing concern because of habitat restoration efforts, wetland
sustainability as sea level rises, and potential contaminant accumulation. We measured water and sediment fluxes through two
channels on Browns Island, at the landward end of San Francisco Bay, United States, to determine the factors that control
sediment fluxes on and off the island. In situ instrumentation was deployed between October 10 and November 13, 2003. Acoustic
Doppler current profilers and the index velocity method were employed to calculate water fluxes. Suspended sediment concentrations
(SSC) were determined with optical sensors and cross-sectional water sampling. All procedures were analyzed for their contribution
to total error in the flux measurement. The inability to close the water balance and determination of constituent concentration
were identified as the main sources of error; total error was 27% for net sediment flux. The water budget for the island was
computed, with an unaccounted input of 0.20 m3s−1 (22% of mean inflow), after considering channel flow, change in water storage, evapotranspiration, and precipitation. The
net imbalance may be a combination of groundwater seepage, overland flow, and flow through minor channels. Change of island
water storage, caused by local variations in water surface elevation, dominated the tidally averaged water flux. These variations
were mainly caused by wind and barometric pressure change, which alter regional water levels throughout the Sacramento-San
Joaquin River Delta. Peak instantaneous ebb flow was 35% greater than peak flood flow, indicating an ebbdominant system, though
dominance varied with the spring-neap cycle. SSC were controlled by wind-wave resuspension adjacent to the island and local
tidal currents that mobilized sediment from the channel bed. During neap tides sediment was imported onto the island but during
spring tides sediment was exported because the main channel became ebb dominant. Over the 34-d monitoring period 14,000 kg
of suspended sediment were imported through the two channels. The water imbalance may affect the sediment balance if the unmeasured
water transport pathways are capable of transporting large amounts of sediment. We estimate a maximum of 2,800 kg of sediment
may have been exported through unmeasured pathways, giving a minimum ent import of 11,200 kg. Sediment flux measurements provide
insight on tidal to fortnightly marsh sedimentation processes, especially in complex systems where sedimentation is spatially
and temporally variable. 相似文献
715.
Although fossil assemblages from the late Early Pleistocene are very rare in Britain, the site of Westbury Cave in Somerset, England, has the potential to address this gap. The mammal fossils recovered previously from the Siliceous Member in Westbury Cave, though few in number, have hinted at an age for the deposits that is as yet unparalleled in Britain. Here, we describe the first bona fide occurrence of Hippopotamus in the British Early Pleistocene, discovered during recent reinvestigation of the Siliceous Member. The hippo fossil indicates a refined biochronological age of ca. 1.5–1.07 Ma for the Siliceous Member and a palaeoclimate that was warm and humid, which accords well with previous palaeoenvironmental inferences. A synthesis of late Early Pleistocene hippo occurrences suggests that the Siliceous Member hippo may have been part of an early colonization of north-west Europe by these megaherbivores, possibly during MIS (Marine Oxygen Isotope Stage) 31. Alternatively, it evidences a currently cryptic northward migration during an even earlier temperate phase. In either case, the Siliceous Member is likely to represent a warm period that has not been recognized previously in the British Quaternary record. 相似文献
716.
Investigation of the Upper Carboniferous to Lower Permian sedimentary strata of central Spitsbergen shows that this highly cyclic rock succession is composed of four long-term transgressive–regressive cycles. These long-term cycles are themselves composed of stacked higher order cycles. Transgressive phases are characterized by increasing accommodation space, and include a basal transgressive part of marked retrogradation of facies belts and thickening-upward component cycles. Regressive phases are characterized by decreasing accommodation space, displayed by progradation of facies belts, overall shallowing and increased restriction of the depositional environment, influx of coarse terrigenous sediments and increasing evidence of exposure and/or non-deposition. The oldest transgressive–regressive sequence identified, Sequence 1, is of Serpukhovian to Bashkirian age and represents a syn-rift sequence. Also composed of syn-rift sediments is the transgressive–regressive Moscovian to mid-Gzhelian-aged Sequence 2. The late Gzhelian to late Asselian Sequence 3 is mainly a post-rift sequence. The youngest sequence, Sequence 4, is of Sakmarian to possible Artinskian age, and is also composed of post-rift sediments. The individual transgressive–regressive cycles are defined as second-order cycles, based on lithological signatures, lateral extent of bounding unconformities, and the actual time period the cycles span. Local tectonic activity is believed to control to some extent the development of short-term cycles in the syn-rift succession. However, cyclicity within the long-term cycles is mainly controlled by eustatic sea-level fluctuations, and therefore enables them to be correlated to other Circum-Arctic regions. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献