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本文将随机振动的虚拟激励法与拱坝-地基动力相互作用FE-BE-IBE时域模型结合,发展了一个可以考虑多维随机地震动作用下的拱坝动力响应计算模型,并用Monte Garlo方法对模型进行了验证,计算结果表明,地震动分量的相关性对结构的动力响应存在一定影响,合理考虑地震动各方向分量的相关性可以更好地计算实际地震作用下的拱坝动力响应。 相似文献
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反射光谱技术:研究南极企鹅古生态演化的一种新方法 总被引:2,自引:0,他引:2
为探求快速、廉价、无损和同步的光谱技术在南极生态环境研究中的可能性,本文利用南极阿德雷岛的四根企鹅粪土沉积柱样品的反射光谱,通过逐步多元线性回归和主成分回归两种数学运算方法,建立了反射光谱数据与企鹅粪九种标型元素浓度之间的关系,并探讨了南极企鹅粪土沉积物光谱数据的古生态意义。结果表明:南极粪土沉积样品反射率光谱与企鹅粪九种标型元素(P、Ca、Cu、F、Ba、S、Zn、Sr、Se)含量之间存在良好的相关性,预测值与实测值之间的相关系数R都达到了0.9以上,在深度剖面上预测浓度与实测浓度具有非常一致的变化趋势;南极粪土沉积物光谱数据包含有明确的古生态变化信息,可利用主成分分析快速恢复历史时期企鹅数量演化过程。本研究结果为在偏远的南极地区开展古生态环境研究提供了一种新的快捷方法和技术途径。 相似文献
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Bridge fragility curves, which express the probability of a bridge reaching a certain damage state for a given ground motion parameter, play an important role in the overall seismic risk assessment of a transportation network. Current analytical methodologies for generating bridge fragility curves do not adequately account for all major contributing bridge components. Studies have shown that for some bridge types, neglecting to account for all of these components can lead to a misrepresentation of the bridges' overall fragilities. In this study, an expanded methodology for the generation of analytical fragility curves for highway bridges is presented. This methodology considers the contribution of the major components of the bridge, such as the columns, bearings and abutments, to its overall bridge system fragility. In particular, this methodology utilizes probability tools to directly estimate the bridge system fragility from the individual component fragilities. This is illustrated using a bridge whose construction and configuration are typical to the Central and Southeastern United States and the results are presented and discussed herein. This study shows that the bridge as a system is more fragile than any one of the individual components. Assuming that the columns represent the entire bridge system can result in errors as large as 50% at higher damage states. This provides support to the assertion that multiple bridge components should be considered in the development of bridge fragility curves. The findings also show that estimation of the bridge fragilities by their first‐order bounds could result in errors of up to 40%. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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A statistical analysis of the peak acceleration demands for nonstructural components (NSCs) supported on a variety of stiff and flexible inelastic regular moment‐resisting frame structures with periods from 0.3 to 3.0 s exposed to 40 far‐field ground motions is presented. Peak component acceleration (PCA) demands were quantified based on the floor response spectrum (FRS) method without considering dynamic interaction effects. This study evaluated the main factors that influence the amplification or decrease of FRS values caused by inelasticity in the primary structure in three distinct spectral regions namely long‐period, fundamental‐period, and short‐period region. The amplification or decrease of peak elastic acceleration demands depends on the location of the NSC in the supporting structure, periods of the component and building, damping ratio of the component, and level of inelasticity of the supporting structure. While FRS values at the initial modal periods of the supporting structure are reduced due to inelastic action in the primary structure, the region between the modal periods experiences an increase in PCA demands. A parameter denoted as acceleration response modification factor (Racc) was proposed to quantify this reduction/increase in PCA demands. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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The spatial organization of decadal and bidecadal components (fluctuations) of annual rainfall is identified in this research for two regions: (1) southern South America, and (2) southern North America (conterminous USA, southeastern Canada and northern and central Mexico). Findings indicate that these decadal and bidecadal components have highly coherent wave-like spatial organization. Two types of organization of decadal and bidecadal components of annual rainfall were identified: a train of propagating fluctuations and quasi-standing fluctuations. For decadal components, such patterns alternate in time. A widespread change in the spatial organization of decadal component of annual rainfall took place simultaneously in both continents in 1932. The bidecadal component is organized as standing fluctuations in southern North America and as travelling fluctuations in southern South America, The spatial pattern of decadal fluctuations of annual rainfall has 12- and 13-year cycles, and the spatial pattern of bidecadal fluctuations has predominantly 21- and 22-year cycles. 相似文献
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地震面波产生的地震动转动分量研究 总被引:7,自引:0,他引:7
本文利用弹性波动理论对地面转动分量,即瑞利(Rayleigh)波和乐夫(Love)波产生的转动分量进行了研究,给出了相应的计算公式和计算方法,特别注意到面波的散射效应对转动分量的影响,并将这一特性引入到转动分量的求取中,使问题的解决更切合于实际,最后选取实际地震记录,利用得到的公式计算出地震面波产生的转动分量。 相似文献