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The Impact of Horizontal Resolution on the CNOP and on Its Identified Sensitive Areas for Tropical Cyclone Predictions 总被引:1,自引:0,他引:1
In this study,the impacts of horizontal resolution on the conditional nonlinear optimal perturbation (CNOP) and on its identified sensitive areas were investigated for tropical cyclone predictions.Three resolutions,30 km,60 km,and 120 km,were studied for three tropical cyclones,TC Mindulle (2004),TC Meari (2004),and TC Matsa (2005).Results show that CNOP may present different structures with different resolutions,and the major parts of CNOP become increasingly localized with increased horizontal resolution.CNOP produces spiral and baroclinic structures,which partially account for its rapid amplification.The differences in CNOP structures result in different sensitive areas,but there are common areas for the CNOP-identified sensitive areas at various resolutions,and the size of the common areas is different from case to case.Generally,the forecasts benefit more from the reduction of the initial errors in the sensitive areas identified using higher resolutions than those using lower resolutions.However,the largest improvement of the forecast can be obtained at the resolution that is not the highest for some cases.In addition,the sensitive areas identified at lower resolutions are also helpful for improving the forecast with a finer resolution,but the sensitive areas identified at the same resolution as the forecast would be the most beneficial. 相似文献
104.
The Roles of Spatial Locations and Patterns of Initial Errors in the Uncertainties of Tropical Cyclone Forecasts 总被引:1,自引:0,他引:1
In this study,a series of sensitivity experiments were performed for two tropical cyclones (TCs),TC Longwang (2005) and TC Sinlaku (2008),to explore the roles of locations and patterns of initial errors in uncertainties of TC forecasts.Specifically,three types of initial errors were generated and three types of sensitive areas were determined using conditional nonlinear optimal perturbation (CNOP),first singular vector (FSV),and composite singular vector (CSV) methods.Additionally,random initial errors in randomly selected areas were considered.Based on these four types of initial errors and areas,we designed and performed 16 experiments to investigate the impacts of locations and patterns of initial errors on the nonlinear developments of the errors,and to determine which type of initial errors and areas has the greatest impact on TC forecasts.Overall,results from the experiments indicate the following:(1) The impact of random errors introduced into the sensitive areas was greater than that of errors themselves fixed in the randomly selected areas.From the perspective of statistical analysis,and by comparison,the impact of random errors introduced into the CNOP target area was greatest.(2) The initial errors with CNOP,CSV,or FSV patterns were likely to grow faster than random errors.(3) The initial errors with CNOP patterns in the CNOP target areas had the greatest impacts on the final verification forecasts. 相似文献
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高原东侧突发性大暴雨过程中螺旋度的诊断分析 总被引:4,自引:1,他引:3
利用MM5模式模拟输出结果,对2002年6月8-9日发生在陕西省和四川北部的一次突发性大暴雨过程进行了螺旋度诊断分析.结果表明:暴雨区附近总存在一对紧邻的大小(低层)或正负(中层)螺旋度中心,低层螺旋度正值区强度远大于中高层螺旋度正负值区,对流层中层正负中心的轴线随高度呈逆时针旋转,相应的垂直结构是一对正负相伴的螺旋度柱.当暴雨区东侧正螺旋度突然向高层伸展,西侧伴有负螺旋度发展,且两中心间等值线变密集时,暴雨开始,大小(正负)螺旋度最强及其间等值线最紧密时,暴雨达到最强盛时期,而且暴雨就发生在两螺旋度之间偏大值中心的等值线密集区.进一步分析表明:螺旋度发生发展的主要贡献者是水平速度和水平速度的垂直切变. 相似文献
108.
This work analyzes the consequences of climate change in the distribution of the Mediterranean high-mountain vegetation. A study area was chosen at the Sierra de Guadarrama, in the center of the Iberian Peninsula (1,795 to 2,374 m asl). Climate change was analyzed from the record of 18 variables regarding temperature, rainfall and snowfall over the period 1951–2000. The permanence of snow cover (1996–2004), landforms stability and vegetation distribution in 5 years (1956, 1972, 1984, 1991 and 1998) were all analyzed. The Nival Correlation Level of the different vegetation classes was determined through their spatial and/or temporal relationship with several climatologic variables, snow cover duration and landforms. In order to quantify trends and major change processes, areas and percent changes were calculated, as well as Mean Annual Transformation Indices and Transition Matrices. The findings reveal that in the first part of the study period (up to the first half of the 1970s) the temperature rise in the mid-winter months caused the reduction of some classes of nival vegetation, while others expanded, favored by high rainfall, decrease in both maximum temperatures and summer aridity, and longer snow cover duration. The second part of the study period was characterized by the consolidation of the increase in all thermal variables, along with an important reduction in rainfall volume and snow cover duration. As a result, herbaceous plants, which are highly correlated with a long snow permanence and abundance of melting water, have been replaced by leguminous shrubs which grow away from the influence of snow, and which are steadily becoming denser. 相似文献
109.
The conditional nonlinear optimal perturbation (CNOP), which is a nonlinear generalization
of the linear singular vector (LSV), is applied in important problems of atmospheric and oceanic
sciences, including ENSO predictability, targeted observations, and ensemble forecast. In this study,
we investigate the computational cost of obtaining the CNOP by several methods. Differences and
similarities, in terms of the computational error and cost in obtaining the CNOP, are compared among
the sequential quadratic programming (SQP) algorithm, the limited memory Broyden-Fletcher-Goldfarb-Shanno
(L-BFGS) algorithm, and the spectral projected gradients (SPG2) algorithm. A theoretical grassland
ecosystem model and the classical Lorenz model are used as examples.
Numerical results demonstrate that the computational error is acceptable with all three algorithms.
The computational cost to obtain the CNOP is reduced by using the SQP algorithm. The experimental
results also reveal that the L-BFGS algorithm is the most effective algorithm among the three
optimization algorithms for obtaining the CNOP. The numerical results suggest a new approach and
algorithm for obtaining the CNOP for a large-scale optimization problem. 相似文献
110.