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201.
The study intended to describe the alpine vegetation of a protected area of the northwestern Himalaya and identify the important
environmental variables responsible for species distribution. We placed random plots covering different habitats and altitude
to record species composition and environmental variables. Vegetation was classified using hierarchical cluster analysis and
vegetation-environment relationships were evaluated with Canonical Correspondence Analysis. Four communities, each in alpine
shrub and meadows were delineated and well justified in the ordination plots. Indicator species for the different communities
were identified. Maximum species richness and diversity were found in community IV among shrub communities and community II
among the meadows. Studied environmental variables explained 61.5% variation in shrub vegetation and 59.8% variation in meadows.
Soil variables explained higher variability (∼35%) than spatial variables (∼21%) in both shrubs and meadows. Altitude, among
the spatial variables and carbon/nitrogen ratio and nitrogen among the soil variables explained maximum variation. About 40%
variations left unexplained. Latitude and species diversity among the other variables had significant correlation with ordination
axes. Study showed that altitude and C/N ratio played a significant role in species composition. Extensive sampling efforts
and inclusion of other non-studied variables are also suggested for better understanding. 相似文献
202.
Long-Ming Li Min Sun Yuejun Wang Guangfu Xing Guochun Zhao Shoufa Lin Xiaoping Xia Lungsang Chan Feifei Zhang Jean Wong 《Gondwana Research》2011,19(1):191-201
Amphibolites occur in a number of localities in the Cathaysia Block, some of them have been migmatised and their protoliths represent basaltic magmas erupted in various tectonic settings. Four migmatised amphibolites were collected from Jiangxi and Fujian Provinces. Cathodo-luminescence images of zircons extracted from the representative amphibolites show unzoned or sector-zoned structure. LA-ICP-MS analysis indicates that most zircons have high Th/U ratios and yield U–Pb zircon ages of 446 ± 5, 435 ± 2, 434 ± 4 and 423 ± 2 Ma, respectively. Lu–Hf isotopic analysis on these zircons gives Hf model ages ranging from 900 to 1200 Ma. Based on lithological observations and previously published geochronological data, we interpret that these U–Pb ages record an important tectonothermal event that led to the migmatization. This early Paleozoic (Caledonian) tectonothermal event in the Southeastern China has a great tectonic implication for the evolutionary history of the Cathaysia Block. 相似文献
203.
204.
We present the results of measurements carried out with the help of the “Donnaya Stantsiya” complex of equipment in the coastal
zone of the Crimean shelf near Evpatoriya and near the southeast end of the Kosa Tuzla Island. For the same intensity of winds
in these regions, the intensities of waves and turbulence in the coastal zone near Evpatoriya are much higher and, hence,
the fluxes of suspended sediments are more intense. The accumulated data are intended for the correction of the kinetic model
used for the evaluation of the characteristics of the field of suspended sediments in the shallow-water areas. 相似文献
205.
206.
The viscoelastic deformation behavior of a sedimentary rock under different loading rates is numerically modeled and investigated by the numerical manifold method (NMM). By incorporating a modified 3-element viscoelastic constitutive mode in the NMM, crack initiation and propagation criteria, and crack identification and evolution techniques, the effects of the loading rates on the cracking behavior of a sedimentary rock, such as crack open displacement, crack sliding displacement, crack initiation, crack propagation and final failure mode, are successfully modeled. The numerical results reveal that under a high loading rate (>1,000 MPa/s), due to the viscoelastic property of the sedimentary rock, not only the structural behavior deviates from that of elastic model, but also different cracking processes and final failure modes are obtained. 相似文献
207.
雷达资料在云南一次强降水过程中的三维变分同化试验 总被引:2,自引:0,他引:2
鉴于云南观测信息相对不足、局地强降水突出的现状,利用WRF(Weather Research and Forecasting)模式及其变分同化系统进行雷达反射率因子和反演风场的三维变分同化试验。通过对2012年9月12日00:00—13日00:00发生在云南的一次强降水过程进行数值模拟和对比分析,结果表明,同时同化雷达反演风场和基本反射率因子,对区域模式同化系统中风矢量、相对湿度、位势高度几个基本分析量都有明显影响。雷达资料的同化,有利于区域模式初始场中强降水区域的上游中低层空气湿度增加、水汽输送增强和强降水发生区域的风场辐合加强,从而改善区域模式对强降水落区、强度的预报质量。对于切变线等天气尺度系统影响下的强降水过程,雷达资料的同化持续时间选取3 h、同化间隔为1 h较适宜。另外,雷达反演风场和基本反射率因子的同化均对降水预报改善有明显贡献,且多种资料的同化效果好于单一资料同化。 相似文献
208.
209.
郯庐断裂带新近纪以来的挤压构造与合肥盆地的反转 总被引:13,自引:0,他引:13
郯庐断裂带于新近纪以来呈现强烈的逆冲活动,使得先存的伸展性断层产生了一系列逆冲反转构造.该逆冲活动使合肥盆地东部边缘地层被明显掀斜并产生断弯褶皱.与此同时,合肥盆地也相应遭受了挤压而反转,在合肥盆地内形成了一系列NW向左行平移断层和NNE向的宽缓褶皱构造.这些构造对油气二次运移和圈闭有利.在太平洋板块向西俯冲产生的弧后扩张使中国东部大陆受到挤压的区域动力学背景下,郯庐断裂的逆冲活动和合肥盆地反转构造在近EW向挤压应力下形成. 相似文献
210.