全文获取类型
收费全文 | 3378篇 |
免费 | 733篇 |
国内免费 | 436篇 |
专业分类
测绘学 | 370篇 |
大气科学 | 518篇 |
地球物理 | 2054篇 |
地质学 | 435篇 |
海洋学 | 469篇 |
天文学 | 270篇 |
综合类 | 208篇 |
自然地理 | 223篇 |
出版年
2024年 | 9篇 |
2023年 | 36篇 |
2022年 | 78篇 |
2021年 | 119篇 |
2020年 | 132篇 |
2019年 | 151篇 |
2018年 | 131篇 |
2017年 | 140篇 |
2016年 | 133篇 |
2015年 | 160篇 |
2014年 | 169篇 |
2013年 | 186篇 |
2012年 | 170篇 |
2011年 | 178篇 |
2010年 | 167篇 |
2009年 | 197篇 |
2008年 | 193篇 |
2007年 | 225篇 |
2006年 | 209篇 |
2005年 | 204篇 |
2004年 | 198篇 |
2003年 | 185篇 |
2002年 | 156篇 |
2001年 | 116篇 |
2000年 | 124篇 |
1999年 | 107篇 |
1998年 | 103篇 |
1997年 | 83篇 |
1996年 | 82篇 |
1995年 | 87篇 |
1994年 | 72篇 |
1993年 | 63篇 |
1992年 | 47篇 |
1991年 | 32篇 |
1990年 | 22篇 |
1989年 | 29篇 |
1988年 | 18篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1977年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有4547条查询结果,搜索用时 140 毫秒
991.
Wenyang Zhang Doriam Restrepo Jorge G.F. Crempien Bulent Erkmen Ricardo Taborda Asli Kurtulus Ertugrul Taciroglu 《地震工程与结构动力学》2021,50(1):177-196
Scenario‐based earthquake simulations at regional scales hold the promise in advancing the state‐of‐the‐art in seismic risk assessment studies. In this study, a computational workflow is presented that combines (i) a broadband Green's function‐based fault‐rupture and ground motion simulation—herein carried out using the “UCSB (University of California at Santa Barbara) method”, (ii) a three‐dimensional physics‐based regional‐scale wave propagation simulation that is resolved at Hz, and (iii) a local soil‐foundation‐structure finite element analysis model. These models are interfaced with each other using the domain reduction method. The innermost local model—implemented in ABAQUS—is additionally enveloped with perfectly matched layer boundaries that absorb outbound waves scattered by the structures contained within it. The intermediate wave propagation simulation is carried out using Hercules , which is an explicit time‐stepping finite element code that is developed and licensed by the CMU‐QUAKE group. The devised workflow is applied to a km region on the European side of Istanbul, which was modeled using detailed soil stratigraphy data and realistic fault rupture properties, which are available from prior microzonation surveys and earthquake scenario studies. The innermost local model comprises a chevron‐braced steel frame building supported by a shallow foundation slab, which, in turn, rests atop a three‐dimensional soil domain. To demonstrate the utility of the workflow, results obtained using various simplified soil‐structure interaction analysis techniques are compared with those from the detailed direct model. While the aforementioned demonstration has a limited scope, the devised workflow can be used in a multitude of ways, for example, to examine the effects of shallow‐layer soil nonlinearities and surface topography, to devise site‐ and structure‐specific seismic fragilities, and for calibrating regional loss models, to name a few. 相似文献
992.
993.
994.
995.
垂直低分辨率GCM模式大气平均经圈环流的诊断 总被引:9,自引:2,他引:9
王盘兴 《南京气象学院学报》1994,17(2):200-204
以IAP2-L GCM为例,给出垂直低分辨率GCM模式大气平均经圈环流质量流函数的一个计算方案,结果表明,模式大气的Hadley环流季节变化与实际大气相一致。El Nino年模式大气平均经圈环流中可分离出一个与El Nino型SST异常关系密切的异常经圈环流,它导致平均Hadley环流向北半球盛夏型转变的滞后。 相似文献
996.
本文利用大气边界层近地层中观测得的风和温度时间序列讨论计算了湍流的非线性动力学统计参量与其经典统计量的关系。初步结果表明:当层结稳定参数z/L处于-0.7相似文献
997.
本文根据谐谱展开的水平动量方程,在一定的假设下导出了集时间平均场的涡、散性质于一体的诊断关系式——大气振动频率的优势选择判据,并据此讨论了基本?场的水平不均匀对大气振动的影响。通过这个关系式,利用1982年ECM?WF资料对优势频率进行了计算,给出了对流层高、中、低各层的全球分布。?从而指出在实际大气中存在着基本场对某频率上的振动有选择放大作用。 相似文献
998.
EstimationofWindsatDifferentlsobaricLevelsBasedontheObserved Windsat850hPaLevelUsingDoubleFourierSeriesS.N.BavadekarandR.M.Kh?.. 相似文献
999.
Ma Kaiyu 《Acta Meteorologica Sinica》1994,8(4):461-467
In this paper,a design to estimate climate noise of annual mean temperature has been made by means of the minimum interannual variance and effectively independent observations in time series.By using it the climate noises of annual mean surface air temperatures have been estimated based on the data from 1960 to 1991 in this country.The low values of climate noises of annual mean temperatures are found in the southeastern Tibet Plateau,Yunnan,the Sichuan Basin and south of the middle and lower reaches of the Changjiang River Valley.The high values are seen in the northwestern and northeastern China and the rest of the Tibet Plateau.A relatively low value region is in the southern Xinjiang. 相似文献
1000.
Many of the numerical techniques used for seismic zonation studies treat one-dimensional structural models and/or the incidence of plane polarized body waves. These techniques are often not adequate for laterally heterogeneous structures and for sources that are not located beneath the site of interest. In such cases a more rigorous treatment of the combined effects of the source, the path and the site response is needed. This can be accomplished with a hybrid approach combining modal summation and the finite-difference technique. To demonstrate the differences between these techniques, the ground motion in the city of Benevento (Italy) is modelled. We first compare the results obtained with one-and two-dimensional structural models for vertical incidence of plane polarized body waves. These results are then compared with those obtained with the hybrid approach for two-dimensional structural models.The comparisons have allowed us to find important differences in the response obtained with the different modelling techniques. For the same site, these differences consist of strong variations in amplitude and in the shape of the spectral amplifications. For a seismic source which is not located beneath the site, vertical incidence of waves significantly overestimates the local hazard in a laterally homogeneous structure. For a laterally heterogeneous area, we can conclude that one-dimensional modelling fails to estimate the seismic hazard, whereas for a seismic source which is not located beneath the site of interest, two-dimensional modelling with vertical incidence of plane polarized body waves may not allow reliable estimates to be made of the frequency bands at which amplifications occur. The results obtained for two-dimensional structural models are used for a zonation of the city of Benevento. 相似文献