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171.
172.
ANTARCTIC SEA ICE AND THE POLAR VORTEX INDEX:TEMPORAL AND SPATIAL CHARACTERISTICS AND THEIR RELATIONSHIP 总被引:1,自引:0,他引:1
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The cluster analysis method has been used to divide the Antarctic sea ice variation field into 5 sectors.Then,foreach of these sectors,the corresponding indexes of vortex area and vortex intensity on the 500 hPa level have been calcu-lated.These data were used to analyse the temporal and spatial characteristics of both Antarctic sea ice and the vortexindex variations and their relationship.Our results show that substantial differences are presented in the climatic patternand interannual variations of the sea ice data and vortex index in different sectors.The maximum sea ice extent varia-tions appear in sector 1 and sector 4.Oscillation periods of 2—2.5 and 5—7 years exist in the variations of sea ice extentand vortex index in most sectors.A positive trend is only found in sector 1 sea ice extent while the other sectors shownegative trends.The average extent of the Antarctic sea ice as a whole has retreated at a rate of 1.6 latitudes per 100years.The vortex areas for all sectors have decreased.Nevertheless,the vortex intensities in 3 sectors have increased.Therelationship between sea ice and vortex characters in each sector is obvious,but a little complex.Sectors 1 and 5,whichare located in the Southeast Pacific and South Atlantic,are the most sensitive areas in terms of sea ice/atmosphereinteraction. 相似文献
173.
Scale Dependencies of Vegetation and Topography in a Mountainous Environment of Montana 总被引:2,自引:2,他引:2
This research examines the effects of spatial scale on estimating the relationship between vegetation biomass and topography within a portion of Glacier National Park, Montana. The Reflectance/Absorptance vegetation index, developed from processed Landsat Thematic Mapper digital data, is related to three topographic variables obtained through processed Digital Elevation Models: elevation, slope angle, and slope aspect. R2 values between the vegetation index and the topographic variables are obtained from regression analyses at a series of aggregated spatial scales. The effective range of spatial scales within which the two sets of variables are spatially dependent and the degree of the spatial dependencies are characterized through semivariance and fractal analyses. 相似文献
174.
175.
天津市东丽区第四系Ⅱ组深层淡水在长期较强开采状态下未发生水位持续下降及大面积深层淡水成化污染,十余年来地层沉降基本消失.该地多年来中更新统淡水及上更新统、全新统咸水水位具有同步不等幅的动态,证明它们之间联系密切,地层中渗透系数小于10-3m/d的历次海侵沉积层及压实的粘土层具有半透膜特性,咸水越流补给第Ⅱ承压含水组的是淡水.适量加大Ⅱ组淡水开采强度,使其产生越流系统,稳定后不会再加大地面沉降.最终使全新统地下水下入渗水位降低,夺取潜水蒸发的水量.在有咸水分布区,地表入渗水是尚没有引起足够重视的可持续利用地下淡水的补给来源. 相似文献
176.
Bian Yin-ju 《地震学报(英文版)》2005,18(4):441-450
We try to give a quantitative and global discrimination function by studying m
b/M
S data using Fisher method that is a kind of pattern recognition methods. The reliability of the function is also analyzed.
The results show that this criterion works well and has a global feature, which can be used as first-level filtering criterions
in event identification. The quantitative and linear discrimination function makes it possible to identify events automatically
and achieve the goal to react the events quickly and effectively.
Contribution No.05FE3018, Institute of Geophysics, China Earthquake Administrtion. 相似文献
177.
178.
The abnormal distribution of the molecular fossils in the pre-Cambrian and Cambrian: its biological significance 总被引:9,自引:0,他引:9
Dinosteranes and 4-methyl-24-ethylcholestanes are usually to be thought of as biomarkers for dinoflagellates, and 24-norcholestanes
and C28steranes for diatom. Therefore, the highest concentrations of these compounds are typically found in strata deposited since
the beginning of the Mesozoic. However these compounds appeared widely and abundantly in extracts from organic-rich sediments
in the Sinian and Cambrian of the Tarim Basin. This suggests that some of the planktonic algae such as dinoflagellates and
diatoms have an earlier origin than the Mesozoic. Some of the remarkable algal fossils observed in the Cambrian, in both well
He 4 and the outcrop section of Xiao-Er-Bulak, Tarim Basin, provide possible biological evidence for this kind of inference. 相似文献
179.
Preliminary study on the relationship between the crust-mantle structure and the formation of Laowangzhai superlarge gold deposit 总被引:2,自引:0,他引:2
The essential shallow-crust structural factors controlling the formation of Laowangzhai gold deposit include favorable tectonic
and regional structural site, the release site of a great deal of the earth energy, favorable orecontrolling structure system,
abundant and favorable source rocks for gold, ductile shearing, abundant minerogenetic materials source in extensive crust
and mantle. And the essential deep-seated crust-mantle structure factors dominating the formation of the ore deposit include
intracrustal low-velocity len, high-velocity bodies in the lower part of middle crust and lower crust, the steps on the slope
of Moho, connecting site of mantle rises, the crust-mantle transition layer, upwelling of asthenosphere and the low-velocity
plume. It is concluded that the fundamental reason that controls the formation of Laowangzhai superlarge gold deposit lies
in the coupling between deep and shallow crust-mantle structure factors controlling the formation of the deposit and their
coupling with the lithospheric evolution and geological event.
Project supported by the National Climbing Plan Programme A-30. 相似文献
180.
In this paper an alternative approach to spherical harmonic analysis is investigated which uses piecewise linear interpolations
(PLIs) to replace conventional block mean values (BMVs). Detailed formulations for using PLIs in spherical harmonic analysis
are systematically developed. Research shows that BMVs give rise to larger errors than PLIs. Error estimations for the two
approaches are given, convincingly showing that PLIs yield much better results than BMVs. Many numerical examples are illustrated
and numerically show that PLIs are more reliable and applicable than BMVs.
Received: 8 October 1996 / Accepted: 6 March 1998 相似文献