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91.
92.
Jia Xia 《Engineering Geology》2005,78(3-4):209-214
The ancient gravel stratum near Nanjing, China, is a major stratum of Cenozoic age along the middle–lower reaches of the Yangtze River. This paper first presents a typical geological profile and material composition of the ancient gravel stratum, and then discusses its geologic origin, soil–rock-forming processes, engineering mechanical properties, and their relations. These analyses are useful for city planning, geotechnical engineering, construction, and characterization of the geological environment in the Nanjing area.  相似文献   
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A set of Pennsylvanian coals from the North American coal basins, ranging in vitrinite reflectance from 0.65% to 1.75%, was examined, with special emphasis on the optical properties of pseudovitrinite. The results suggest that pseudovitrinite originates from the same material as telocollinite. Slits in the pseudovitrinite seem to have originated in situ due to low-temperature oxidation of woody material; their opening might have been facilitated by devolatilization during coalification. The dominant orientation of the slits is perpendicular to bedding. The intensity and orientation of the slits in pseudovitrinite could be important factors in predicting coalbed gas extraction from coal.  相似文献   
96.
地统计学方法在土壤学中的应用   总被引:24,自引:1,他引:24  
地统计学目前在土壤科学中得到广泛的应用和发展,成为认识土壤特征的一个重要工具.地统计学的空间变异函数和克里格插值等方法是土壤性状分析的主要手段,空间变异函数主要用于描述土壤理化性状空间变异特性,不同的插值方法可优化田间试验设计和田间采样方案,克里格插值方法则特别适用于未测量点土壤属性值的估测等.近年插值方法又被广泛应用于确定区域土壤环境容量和土壤质量标准,随机模拟则用于对土壤特性进行不确定性估计等.因而,地统计学方法对我国大量土壤学资料的整合与分析具有极大的应用前景.  相似文献   
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Wildfires change the infiltration properties of soil, reduce the amount of interception and result in increased runoff. A wildfire at Northeast Attica, Central Greece, in August 2009, destroyed approximately one third of a study area consisting of a mixture of shrublands, pastures and pines. The present study simultaneously models multiple semi‐arid, shrubland‐dominated Mediterranean catchments and assesses the hydrological response (mean annual and monthly runoff and runoff coefficients) during the first few years following wildfires. A physically based, hydrological model (MIKE SHE) was chosen. Calibration and validation results of mean monthly discharge presented very good agreement with the observed data for the pre‐wildfire and post‐wildfire period for two subcatchments (Nash–Sutcliffe Efficiency coefficient of 79.7%). The model was then used to assess the pre‐wildfire and post‐wildfire runoff responses for each of seven catchments in the study area. Mean annual surface runoff increased for the first year and after the second year following the wildfires increased by 112% and 166%, respectively. These values are within the range observed in similar cases of monitored sites. This modelling approach may provide a way of prioritizing catchment selection with respect to post‐fire remediation activities. Additionally, this modelling assessment methodology would be valuable to other semi‐arid areas because it provides an important means for comprehensively assessing post‐wildfire response over large regions and therefore attempts to address some of the scaled issues in the specific literature field of research. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
98.
Identifying the role of the two main driving factors—climate change and human interventions—in influencing runoff processes is essential for sustainable water resources management. For this purpose, runoff regime change detection methods were used to divide the available hydroclimatic variables into a baseline and a disturbed period. We applied hydrological modelling and the climate elasticity of runoff method to determine the contribution of climate change and human interventions to changes in runoff. The hydrological model, SWAT, was calibrated during the baseline period and used to simulate the naturalized runoff pattern for the disturbed period. Significant changes in runoff in the study watershed were detected from 1982, suggesting that human interventions play a dominant role in influencing runoff. The combined effects of climate change and human interventions resulted in a 41.3 mm (23.9%) decrease in runoff during the disturbed period, contributing about 40% and 60% to the total runoff change, respectively. Furthermore, analysis of changes in land cover dynamics in the watershed over the past four decades supported these changes in runoff. Contrary to other decades, the discrepancy between naturalized and observed runoff was small in the 2010s, likely due to increased baseflow as a result of storage and/or release of excess water during the dry season. This study contributes to our understanding of how climate change and human interventions affect hydrological responses of watersheds, which is important for future sustainable water management and drought adaptation.  相似文献   
99.
General circulation model outputs are rarely used directly for quantifying climate change impacts on hydrology, due to their coarse resolution and inherent bias. Bias correction methods are usually applied to correct the statistical deviations of climate model outputs from the observed data. However, the use of bias correction methods for impact studies is often disputable, due to the lack of physical basis and the bias nonstationarity of climate model outputs. With the improvement in model resolution and reliability, it is now possible to investigate the direct use of regional climate model (RCM) outputs for impact studies. This study proposes an approach to use RCM simulations directly for quantifying the hydrological impacts of climate change over North America. With this method, a hydrological model (HSAMI) is specifically calibrated using the RCM simulations at the recent past period. The change in hydrological regimes for a future period (2041–2065) over the reference (1971–1995), simulated using bias‐corrected and nonbias‐corrected simulations, is compared using mean flow, spring high flow, and summer–autumn low flow as indicators. Three RCMs driven by three different general circulation models are used to investigate the uncertainty of hydrological simulations associated with the choice of a bias‐corrected or nonbias‐corrected RCM simulation. The results indicate that the uncertainty envelope is generally watershed and indicator dependent. It is difficult to draw a firm conclusion about whether one method is better than the other. In other words, the bias correction method could bring further uncertainty to future hydrological simulations, in addition to uncertainty related to the choice of a bias correction method. This implies that the nonbias‐corrected results should be provided to end users along with the bias‐corrected ones, along with a detailed explanation of the bias correction procedure. This information would be especially helpful to assist end users in making the most informed decisions.  相似文献   
100.
Spatial information on soil properties is an important input to hydrological models. In current hydrological modelling practices, soil property information is often derived from soil category maps by the linking method in which a representative soil property value is linked to each soil polygon. Limited by the area‐class nature of soil category maps, the derived soil property variation is discontinuous and less detailed than high resolution digital terrain or remote sensing data. This research proposed dmSoil, a data‐mining‐based approach to derive continuous and spatially detailed soil property information from soil category maps. First, the soil–environment relationships are extracted through data mining of a soil map. The similarity of the soil at each location to different soil types in the soil map is then estimated using the mined relationships. Prediction of soil property values at each location is made by combining the similarities of the soil at that location to different soil types and the representative soil property values of these soil types. The new approach was applied in the Raffelson Watershed and Pleasant Valley in the Driftless Area of Wisconsin, United States to map soil A horizon texture (in both areas) and depth to soil C horizon (in Pleasant Valley). The property maps from the dmSoil approach capture the spatial gradation and details of soil properties better than those from the linking method. The new approach also shows consistent accuracy improvement at validation points. In addition to the improved performances, the inputs for the dmSoil approach are easy to prepare, and the approach itself is simple to deploy. It provides an effective way to derive better soil property information from soil category maps for hydrological modelling. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
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