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The Statistical Prediction Of Offshore Winds From Land-Based Data For Wind-Energy Applications 总被引:3,自引:0,他引:3
John L. Walmsley Rebecca J. Barthelmie William R. Burrows 《Boundary-Layer Meteorology》2001,101(3):409-433
Land-based meteorological measurements at two locations on the Danish coast are used to predict offshore wind speeds. Offshore wind-speed data are used only for developing the statistical prediction algorithms and forverification. As a first step, the two datasets were separated into ninepercentile-based bins, with a minimum of 30 data records in each bin. Next, the records were randomly selected with approximately 70% of the data in each bin being used as a training set for development of the prediction algorithms, and the remaining 30% being reserved as a test set for evaluation purposes. The binning procedure ensured that both training and test sets fairly represented the overall data distribution.To base the conclusions on firmer ground, five permutations of these training and test sets were created. Thus, all calculations were based on five cases, each one representing a different random selection from the same data, but maintaining the (approximate) 70-30 split in each bin. This procedure served to ensure that conclusions were not based on a single randomly-selected case. Two statistical methods are employed:multiple linear regression (MLR), and Classification and Regression Trees(CART). MLR produces excellent results using only land-based predictors.The CART results are similar to those from MLR, and tend to be slightly better.Retired 相似文献
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在研究盾构法隧道施工对地层扰动影响的课题中,采用了静力触探仪进行原位测试,测定了盾构动态推进引起周围土体的比贯入阻力Ps值的变化。针对测试时间、范围、数量有限的特点,利用最优分段法对试验数据进行了聚类处理,分析结果表明该方法在地层受盾构施工扰动的一般规律认识上具有参考意义。 相似文献
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We define a distance between sedimentary successions to compare their dissimilarity formally. Distance definition is based on attributed syntactic representation. One-dimensional successions can be represented by a string of lithofacies symbols sequentially or vertically. Each symbol can also have a vector of attributes that can provide other information on lithofacies such as thickness. The distance of any two successions is then defined consisting of its syntactic and attribute subdistances. Syntactic distance measures difference of vertical lithofacies change between two successions and attribute distance measures difference of thickness of corresponding lithofacies. Clustering is used to test validity of distance definition and its potential application to analysis of cycle-dominated sedimentary successions. Example is from the Namurian-A succession in Kincardine basin, central Scotland. There are 56 cycles in intervals of about 300 m each in two boreholes. Recognition of intermediate cycles depends on correctly determining of types of these short cycles and their vertical stacking pattern. Intermediate cycles have better potential in high-resolution stratal correlation regionally. Syntactic clustering results show that 56 short cycles can be classified into four groups with distinctive geological interpretation, which further helps reveal hierarchical cyclic architecture of the whole succession. 相似文献
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Recent investigations of aeolian transport have focused on increasingly short time scales because of growing recognition that wind unsteadiness is a major factor in the dynamics of sediment transport. However, the statistical reliability of shear velocity (u*) estimates becomes increasingly uncertain as averaging interval is decreased. This study provides an empirical assessment of the influence of averaging interval on the reliability of u* estimates. The data consist of 15-min wind-speed profiles (1 Hz sampling) collected at four coastal sites. Each profile was subdivided into progressively shorter fixed-length time intervals, and estimates of u* and the 95% confidence interval for u* were determined for each time-block using standard statistical techniques.The logarithmic model accurately represents the measured wind-speed profiles, even with relatively brief averaging intervals. Mean r2 values remain robust down to block lengths as short as 10–20 s, typically retaining better than 98% of the r2 value found for the full-length data sets. Fewer than 2% of the individual 10-s blocks had r2 values less than 0.9. However, mean confidence intervals typically expanded by 70–80% of the full-record value as block length decreased from 900 to 10 s. For highly log-linear profiles, this amounted to an absolute increase from about ±8% to only ±14% of u*, so that the additional information gained through the use of shorter averaging intervals may outweigh the increase in statistical uncertainty. Nevertheless, given that rates of aeolian transport are generally modeled as a function of u*3, this increase in uncertainty may be significant for transport modeling. Thus, very short averaging intervals should be used with caution when predicting aeolian sediment flux. It is proposed that transport modeling should incorporate the shear velocity confidence interval as an indicator of the potential error associated with this source of uncertainty. 相似文献
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目前对强震迁移的研究多是集中在发现迁移现象方面,一些总结迁移规律的尝试则较为主观。本文认为,强震迁移如果具有规律性则其迁移指标应具有某种统计意义,并且对整体数据集的统计分析可避免传统迁移分析方法中的问题。通过对华北地区强震迁移的3个指标(迁移方位、迁移距离、迁移时间)的统计分析,表明研究地区存在较明显的优势迁移方向(西偏南—东偏北方向)、优势迁移距离(100km内以及300~700km范围)和优势迁移时间间隔(1年内以及3~4年内),不同震级范围以及不同活跃期内的迁移特征略有区别。 相似文献