全文获取类型
收费全文 | 411篇 |
免费 | 88篇 |
国内免费 | 88篇 |
专业分类
测绘学 | 37篇 |
大气科学 | 103篇 |
地球物理 | 91篇 |
地质学 | 187篇 |
海洋学 | 33篇 |
天文学 | 13篇 |
综合类 | 47篇 |
自然地理 | 76篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 25篇 |
2021年 | 29篇 |
2020年 | 22篇 |
2019年 | 27篇 |
2018年 | 40篇 |
2017年 | 32篇 |
2016年 | 28篇 |
2015年 | 23篇 |
2014年 | 31篇 |
2013年 | 16篇 |
2012年 | 22篇 |
2011年 | 15篇 |
2010年 | 21篇 |
2009年 | 27篇 |
2008年 | 26篇 |
2007年 | 10篇 |
2006年 | 22篇 |
2005年 | 9篇 |
2004年 | 12篇 |
2003年 | 9篇 |
2002年 | 8篇 |
2001年 | 14篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 15篇 |
1997年 | 11篇 |
1996年 | 9篇 |
1995年 | 13篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 16篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1958年 | 1篇 |
排序方式: 共有587条查询结果,搜索用时 31 毫秒
181.
182.
183.
FLAC程序在抚顺西露天矿边坡变形治理工程中的应用 总被引:13,自引:0,他引:13
采用FLAC程序对抚顺西露天矿北帮西区W200 ̄W600高陡边坡倾倒滑移变形机理进行数值模拟分析,并对采取的抗滑桩加固工程和疏干减压工程的治理效果进行评价,为边坡整治工程设计提供技术指导和依据。 相似文献
184.
185.
Development and validation of p‐y modeling approach for seismic response predictions of highway bridges 下载免费PDF全文
This study aims to realistically simulate the seismic responses of typical highway bridges in California with considerations of soil–structure interaction effects. The p‐y modeling approaches are developed and validated for embankments and pile foundations of bridges. The p‐y approach models the lateral and vertical foundation flexibility with distributed p‐y springs and associated t‐z and q‐z springs. Building upon the existing p‐y models for pile foundations, the study develops the nonlinear p‐y springs for embankments based on nonlinear 2D and 3D continuum finite element analysis under passive loading condition along both longitudinal and transverse directions. Closed‐form expressions are developed for two key parameters, the ultimate resistant force pult and the displacement y50, where 0.5pult is reached, of embankment p‐y models as functions of abutment geometry (wall width and height, embankment fill height, etc.) and soil material properties (wall‐soil friction angle, soil friction angle, and cohesion). In order to account for the kinematic and site responses, depth‐varying ground motions are derived and applied at the free‐end of p‐y springs, which reflects the amplified embankment crest motion. The modeling approach is applied to simulate the seismic responses of the Painter Street Bridge and validated through comparisons with the recorded responses during the 1992 Petrolia earthquake. It is demonstrated that the flexibility and motion amplification at end abutments are the most crucial modeling aspects. The developed p‐y models and the modeling approach can effectively predict the seismic responses of highway bridges. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
186.
本文通过对一幢中高层住宅在不同水准地震作用下进行的弹性计算和弹塑性动力时程分析,研究了钢筋混凝土异形柱框架-剪力墙结构的动力特性和抗震能力。结果显示该结构整体抗侧刚度大,抗震性能较好。进入塑性阶段后,塑性铰分布合理,满足了结构延性设计的要求。 相似文献
187.
本文对高宽比为2.5的普通钢框架隔震结构模型,采用多种不同的地震动进行了水平向和竖向双向地震输入的振动台试验研究,并利用时程分析法完成了模型结构地震反应的数值分析。试验结果表明,高宽比隔震结构在水平向和竖向双向输入情况下隔震层基本上不会进入拉伸应力状态,即使在9度大震E l Centro和Hach inohe波输入时,隔震层支座仍以受压为主。因此小高宽比隔震结构在场地好的情况下,结构不会出现倾覆,仅需考虑软弱土场地的受拉情况。试验发现竖向地震输入对小高宽比隔震结构水平反应的影响相当小;对小高宽比隔震结构进行水平向地震反应分析时,可以忽略竖向地震对结构的影响。 相似文献
188.
山东半岛2000~2014年蒸散发时空分异特征 总被引:1,自引:0,他引:1
蒸散发的时空格局分析对于合理利用水资源、水资源短缺问题的解决以及旱涝灾害预警和监测具有重要意义。基于山东半岛区域气象资料、MOD16遥感影像数据集及GIS背景信息,分析了山东半岛20002014年地表蒸散量的时空变化特征及趋势,并在年时间尺度上通过基于像元的相关分析法分析了蒸散量与降水和气温的相关性。研究结果表明:在研究时段内平均蒸散量年际波动较大,波动范围为397.9479.8mm,多年蒸散平均值为440.78mm;其中2003年和2008年蒸散量最大,分别超出平均值77.3mm和81.9mm。除水体、滨海湿地外,ET年平均值有明显的由东南向西北递减的特征,降水量和地表植被覆盖度的差异是其空间变异的主要因素。蒸散量与气象因素的相关分析表明,年平均降水量与蒸散量变化呈现明显的正相关关系(0.663),温度与蒸散量呈显著负相关关系(-0.143),NDVI与蒸散量相关性较弱(0.33)。 相似文献
189.
190.
Xueli Shi 《中国海洋大学学报(英文版)》2009,8(2):111-120
In this study, the effects of ‘initial’ soil moisture (SM) in arid and semi-arid Northwestern China on subsequent climate
were investigated with a regional climate model. Besides the control simulations (denoted as CTL), a series of sensitivity
experiments were conducted, including the DRY and WET experiments, in which the simulated ‘initial’ SM over the region 30–50°N,
75–105°E was only 5% and 50%, and up to 150% and 200% of the simulated value in the CTL, respectively. The results show that
SM change can modify the subsequent climate in not only the SM-change region proper but also the far downstream regions in
Eastern and even Northeastern China. The SM-change effects are generally more prominent in the WET than in the DRY experiments.
After the SM is initially increased, the SM in the SM-change region is always higher than that in the CTL, the latent (sensible)
heat flux there increases (decreases), and the surface air temperature decreases. Spatially, the most prominent changes in
the WET experiments are surface air temperature decrease, geopotential height decrease and corresponding abnormal changes
of cyclonic wind vectors at the mid-upper troposphere levels. Generally opposite effects exist in the DRY experiments but
with much weaker intensity. In addition, the differences between the results obtained from the two sets of sensitivity experiments
and those of the CTL are not always consistent with the variation of the initial SM. Being different from the variation of
temperature, the rainfall modifications caused by initial SM change are not so distinct and in fact they show some common
features in the WET and DRY experiments. This might imply that SM is only one of the factors that impact the subsequent climate,
and its effect is involved in complex processes within the atmosphere, which needs further investigation. 相似文献