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471.
Climate change adaptation implications for drought risk mitigation: a perspective for India 总被引:1,自引:0,他引:1
There is a growing evidence that the climate change do has implications for drought vulnerable India with studies projecting
future possible reductions in monsoon related rainfall in the country. The existing drought risk mitigation and response mechanisms
were looked into and gaps were identified by drawing lessons from previous disasters and response mechanisms. In absence of
reliable climate predictions at the scales that make them useful for policy level planning, the emphasis was on identifying
no-regret adaptation options those would reduce current vulnerabilities while mainstreaming the adaptation in the long run.
The most notable climate change implications for the drought vulnerable India are the enhanced preparedness with due emphasis
to the community based preparedness planning, reviewing the existing monsoon and drought prediction methodologies, and establishing
drought monitoring and early warning systems in association with a matching preparedness at the input level. 相似文献
472.
Large-eddy Simulation of Turbulent Flow Across a Forest Edge. Part I: Flow Statistics 总被引:1,自引:1,他引:1
Bai Yang Michael R. Raupach Roger H. Shaw Kyaw Tha Paw U Andrew P. Morse 《Boundary-Layer Meteorology》2006,120(3):377-412
The statistics of turbulent flow across a forest edge have been examined using large-eddy simulation, and results compared with field and wind-tunnel observations. The moorland-to-forest transition is characterized by flow deceleration in the streamwise direction, upward distortion of the mean flow, formation of a high pressure zone immediately in front of the edge, suppression of the standard deviations and covariance of velocity components, and enhancement of velocity skewnesses. For the selected forest density, it is observed that the maximum distortion angle is about 8 degrees from the horizontal. Instead of approaching a downwind equilibrium state in a monotonic manner, turbulence (standard deviations and covariances of velocity components) and mean streamwise velocity undershoot in the transition zone behind the edge. Evolution of flow statistics clearly reveals the growth of an internal boundary layer, and the establishment of an equilibrium layer downwind of the edge. It is evident that lower-order moments generally adjust more quickly over the new rough surface than do higher-order moments. We also show that the streamwise velocity standard deviation at canopy height starts its recovery over the rough surface sooner than does the vertical velocity standard deviation, but completes full adjustment later than the latter. Despite the limited domain size upstream of the edge, large-eddy simulation has successfully reproduced turbulent statistics in good agreement with field and wind-tunnel measurements. 相似文献
473.
The Coldwell alkaline complex is a large (> 350 km2) gabbro and syenite intrusion on the north shore of Lake Superior. It was emplaced at 1108 Ma during early magmatic activity associated with the formation of the Mid-Continent Rift of North America. The eastern gabbro forms a partial ring dyke on the outer margin of the complex and consists of at least three discrete intrusions. The largest of these is the layered gabbro that comprises a 300 m thick fine- to medium-grained basal unit overlain by up to 1100 m of variably massive to layered gabbroic cumulates which vary from olivine gabbro to anorthosite. Several xenoliths of Archaean metamorphic rocks that range in size from 10's to 100's of meters are present in the central part of the intrusion. Within discrete horizons in the layered gabbro are many centimeter- to meter-scale, gabbroic xenoliths. The main cumulus minerals, in order of crystallization, are plagioclase, olivine and clinopyroxene ± Fe-Ti oxides. Biotite and Fe-Ti-oxide are the dominant intercumulus phases. Orthopyroxene occurs not as a cumulus phase but as peritectic overgrowths on cumulus olivine. A detailed petrographic and mineral chemical study of samples from two stratigraphically controlled traverses through the layered gabbro indicates that the stratigraphy cannot be correlated along the 33 km strike of the ring dyke. Mineral compositions show both normal and reversed fractionation trends. These patterns are interpreted to record at least three separate intrusions of magma into restricted dilatant zones within the ring dyke possibly associated with ongoing caldera collapse. Calculations of parental melt composition using mineral — melt equilibria show that even the most primitive gabbros crystallized from an evolved magma with mg# of 0.42-0.49. The presence of orthopyroxene overgrowths on cumulus olivine suggests rising silica activity in the melt during crystallization and implies a subalkaline parentage for the layered gabbro. 相似文献
474.
R. W. L. Shaw 《Geological Journal》1971,7(2):359-380
The rocks generally referred to the Kirkby Moor Flags have been mapped in the Kendal area, roughly bounded by Underbarrow, Sedbergh and Kirkby Lonsdale. The succession is divided into four units: the Lower Underbarrow Flags, the Upper Underbarrow Flags, the Kirkby Moor Flags and the Scout Hill Flags. These represent a redefined succession derived from what had been lumped together as ‘Kirkby Moor Flags’. These units correlate with the Upper Leintwardinian, the Whitcliffian and the Downtonian of the Welsh Borderland. Proof that rocks of Downtonian age occur is demonstrated in an unbroken succession of uniform lithology. Ostracodes form an invaluable part of the fauna in both subdivision and correlation of the succession. The fauna of the Kirkby Moor Flags and the Scout Hill Flags can be classified into assemblage groups which possibly represent communities of species. 相似文献
475.
The Aegean island of Thera (Santorini) was covered by tephra from its cataclysmic Late Bronze Age (ca. 3600 yr B.P.) eruption. Vertical exposures of the eruptive sequence show secondary, nonvolcanic, circular (in cross section) features composed of stratified sediment. Many are inaccessible from the floors of modern quarries and appear to be caves filled with younger sediment, but show no connection to the land surface. A filled cave was found in the wall of a modern gully outside the modern quarries, and a filled cave was found in a terrace scarp, well above the modern gully. Natural (and probably rapid) incision by gullies into the thick tephra deposit left many locations with lateral access to tephra. Inhabitants from post‐Minoan to recent times excavated tephra for materials and buildings, and caves were subsequently filled by sporadic (possibly seasonal) flood events that deposited sediment. These gullies may have provided access for modern tephra removal that isolated the filled caves high on the modern quarry walls. © 2003 Wiley Periodicals, Inc. 相似文献