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151.
152.
地形指数ln(α/tanβ)是一些以物理概念为基础的水文模型的重要参数。TOPMODEL是以计算ln(α/tanβ)指数及其分布为基础的。对于栅格DEM,α为上坡区域通过单位等高线长汇集到单元网格内的面积,反映径流在流域中任一点的累积趋势,tanβ为单元网格的坡角,反映重力使径流顺坡移动的趋势。目前普遍使用的计算该地形指数的方法为多流向法。方法中计算α和tanβ用的均是与流出单元网格流向垂直的等高线长。另外计算下坡单元网格累积汇流面积时没有考虑欲计算ln(α/tanβ)值的单元网格的面积。这些是不合理的。计算α值应该用与流入单元网格流向垂直的等高线长,据此提出了改进后的ln(α/tanβ)的计算方法。方法中计算下坡单元累积汇流面积时包括了欲计算ln(α/tanβ)的单元网格的面积。分析了两种方法计算结果间的差值。 相似文献
153.
基于相干目标的干涉图叠加方法监测天津地区地面沉降 总被引:2,自引:0,他引:2
利用ENVISAT ASAR数据,采用基于相干目标的干涉图叠加方法,对天津地区的地面沉降现象进行了DInSAR监测试验.差分干涉处理采用"两轨法",使用校正了高程异常的SRTM DEM数据消除高程相位.以相干系数为标准选取了相干目标,解缠过程中运用了Delaunay三角剖分和权重最小费用流算法.本文获得的季度平均沉降速率图有效揭示了试验区地面沉降的空间展布及相对形变量,但其获得的绝对形变量尚需地面实测数据校验. 相似文献
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为从数字高程模型(DEM)中自动提取区域水流特征,分析了DEM中地形的形态特征,并进行洼地填充和平地抬升的预处理,应用坡面流模拟方法进行了水流方向的确定及水流方向数字阵列的生成,最后根据水流方向阵列和河流栅格网络图生成需要的水系,其结果与手工数字化的水系基本一致,证明该方法是有效的。 相似文献
157.
Shiwen LI Aihua WENG Jianping LI Xuanlong SHAN Jiangtao HAN Yu TANG Yanhui ZHANG Xueqiu WANG 《中国科学:地球科学(英文版)》2020,63(4):533-547
The three-dimensional(3-D)electrical structure of the upper-mantle was used to examine the deep origins of and relationship among the Cenozoic volcanoes located in Northeast China(NEC).High-quality,long-period magnetotelluric(LMT)full-impedance tensor data were collected in NEC and subjected to 3-D Gauss-Newton inversion in order to construct a resistivity model.The resulting model reveals the presence of multiple localized low-resistivity anomalies(LRAs)within the high resistivity lithosphere beneath NEC.These LRAs partially coincide with Cenozoic volcanoes on the surface.Three LRAs that form a larger,annular LRA were observed in the deep upper mantle beneath the Songliao Basin,whereas vein-like LRAs were found in the asthenosphere that connect the lithosphere and deep upper mantle.Petrophysical analyses suggest that the LRAs may have been caused by fluid-induced melting.Based on our electrical model,we propose that,following dehydration of the subducted Western Pacific slab into the mantle transition zone(MTZ)beneath NEC,the released water migrated upward and caused partial melting at the top of the MTZ beneath the Songliao Basin.Under the effect of buoyancy,the melted mantle formed a thermal upwelling that caused melting of asthenosphere before diapiring at the base of the dry lithosphere.The magma then penetrated structural boundaries(such as thinner,weaker,or activated suture zones)and finally reached the Earth's surface.This melting and upwelling of hot mantle materials may have resulted in large-scale volcanism in the region throughout the Cenozoic,including the eruption of Changbai Mountain and Halaha Volcanoes.Our results suggest that the Cenozoic NEC volcanoes may all share a similar mode of genesis,and probably originated from the annular LRA in the deep upper mantle. 相似文献
158.
Changcheng Liu Deva Prasad Ghosh Ahmed Mohamed Ahmed Salim Weng Sum Chow 《Geophysical Prospecting》2019,67(1):140-149
Amplitude interpretation for hydrocarbon prediction is an important task in the oil and gas industry. Seismic amplitude is dominated by porosity, the volume of clay, pore-filled fluid type and lithology. A few seismic attributes are proposed to predict the existence of hydrocarbon. This paper proposes a new fluid factor by adding a correct item based on the J attribute. The algorithm is verified through stochastic Monte Carlo modelling that contains various rock physical properties of sand and shale. Both gas and oil responses are separated by the new fluid factor. Furthermore, an approach based on the neural network model is trained using the deep learning method to predict the new fluid factor. The confusion matrix shows that this model performs well. This model allows the application of the new fluid factor in the seismic data. In this study, the Marmousi II data set is used to examine the performance of the new fluid factor, and the result is good. Most hydrocarbon reservoirs are identified in the shale–sandstone sequences. The combination of deep learning and the new fluid factor provides a more accurate way for hydrocarbon prediction. 相似文献
159.
Existing numerical investigations of dam-break flows rarely consider the effects of vegetation.This paper presents a depth-averaged two-dimensional model for dam-break flows over mobile and vegetated beds.In the model,both the consequences of reducing space for storing mass and momentum by the existence of vegetation and dragging the flow are considered:the former is considered by introducing a factor (1-c) to the flow depth,where c is the vegetation density;the later is considered by including an additional sink term in the momentum equations.The new governing equations are discretized by the finite volume method;and an existing second-order central-upwind scheme embedded with the hydrostatic reconstruction method for water depth,is used to estimate the fluxes;the source terms are estimated by either explicit or semi-explicit methods fulfilling the stability requirement.Laboratory experiments of dam-break flows or quasi-steady flows with/without vegetation effects/sediment transport are simulated.The good agreements between the measurements and the numerical simulations demonstrate a satisfactory performance of the model in reproducing the flow depth,velocity and bed deformation depth.Numerical case studies of six scenarios of dam-break flows over a mobile and vegetated bed are conducted.It is shown that when the area of the vegetation zone,the vegetation density,and the pattern of the vegetation distribution are varied,the resulted bed morphological change differs greatly,suggesting a great influence of vegetation on the dam-break flow evolution.Specifically,the vegetation may divert the direction of the main flow,hindering the flow and thus result in increased deposition upstream of the vegetation. 相似文献
160.
Mou Leong Tan Liew Juneng Fredolin T. Tangang Ngai Weng Chan Sheau Tieh Ngai 《水文科学杂志》2019,64(8):921-933
Water scarcity issues in the Johor River Basin (JRB) could affect the populations of Malaysia and Singapore. This study provides an overview of future hydro-meteorological droughts using climate projections from an ensemble of four Coordinated Regional Climate Downscaling Experiments – Southeast Asia (CORDEX-SEA) domain outputs under the Representative Concentration Pathway (RCP) 4.5 and 8.5 scenarios for the 2021–2050 and 2071–2100 periods. The climate projections were bias corrected using the quantile mapping approach before being incorporated into the Soil and Water Assessment Tool (SWAT) hydrological model. The Standardized Precipitation Index (SPI) and Standardized Streamflow Index (SSI) were used to examine the meteorological and hydrological droughts, respectively. Overall, future annual precipitation, streamflow, and maximum and minimum temperatures are projected to change by about ?44.2 to 24.3%, ?88.7 to 42.2%, 0.8 to 3.7ºC and 0.7 to 4.7ºC, respectively. The results show that the JRB is likely to receive more frequent meteorological droughts in the future. 相似文献