全文获取类型
收费全文 | 303篇 |
免费 | 129篇 |
国内免费 | 6篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 2篇 |
地球物理 | 376篇 |
地质学 | 29篇 |
综合类 | 13篇 |
自然地理 | 17篇 |
出版年
2023年 | 3篇 |
2022年 | 11篇 |
2021年 | 10篇 |
2020年 | 21篇 |
2019年 | 22篇 |
2018年 | 18篇 |
2017年 | 21篇 |
2016年 | 14篇 |
2015年 | 33篇 |
2014年 | 16篇 |
2013年 | 24篇 |
2012年 | 22篇 |
2011年 | 16篇 |
2010年 | 16篇 |
2009年 | 22篇 |
2008年 | 23篇 |
2007年 | 14篇 |
2006年 | 16篇 |
2005年 | 10篇 |
2004年 | 11篇 |
2003年 | 15篇 |
2002年 | 12篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
排序方式: 共有438条查询结果,搜索用时 31 毫秒
1.
Substantial damage to water supply systems, including water delivery pipelines, water treatment plants, reservoirs, and water
storage tanks, was reported after the 1999 Chi–Chi Taiwan Earthquake. This paper first summarizes the damage survey and then
presents the results of seismic fragility analysis for underground pipelines. Construction blueprints of the water delivery
pipelines and repair work orders of 11 townships and cities in the disastrous area were digitized into a Geographical Information
System (GIS) for analysis and assessment. With the aid of the GIS system, we found that PVC pipes made up 86% of water delivery
pipelines while steel, cast iron, ductile iron, PE and others took the rest. Therefore, this paper focuses on the fragility
analysis of PVC pipes. Three different methods were applied to derive the fragility relations between the PVC water pipes
having nominal diameters (approximately inner diameters) greater than or equal to 65 mm and earthquake intensity parameters
such as peak ground acceleration and peak ground velocity. The results were then examined with those of other countries. The
discrepancy between our results and the empirical equation used by HAZUS, an earthquake loss estimation software developed
by the Federal Emergency Management Agency was not significant. 相似文献
2.
3.
4.
八宝喀斯特山区生态环境问题与治理措施 总被引:3,自引:1,他引:3
喀斯特峰丛山区生态系统特征有:结构简单,稳定性差,恢复困难等。其生态系统脆弱性表现为:(1)裸露型喀斯特山地坡度陡峻,土壤贫脊,耕地少而分散,水土保持能力差;(2)地下水文网发育导致地表水大量漏失,地下水位埋藏深,难以开采利用;(3)植被树种单一,生长缓慢,资源开发过程中易产生耕作粗放,水土流失,石漠化等环境问题,对其治理和恢复过程应是渐进式的:水-土-林,即首先要科学开发利用各种水资源,同时合理规划利用土地资源,其次要加速生态系统重建,使其形成良性循环发展方式。 相似文献
5.
Motivated by the development of performance‐based design guidelines with emphasis on both structural and non‐structural systems, this paper focuses on seismic vulnerability assessment of block‐type unrestrained non‐structural components under sliding response on the basis of seismic inputs specified by current seismic codes. Two sliding‐related failure modes are considered: excessive relative displacement and excessive absolute acceleration. It is shown that an upper bound for the absolute acceleration response can be assessed deterministically, for which a simple yet completely general equation is proposed. In contrast, fragility curves are proposed as an appropriate tool to evaluate the excessive relative displacement failure mode. Sample fragility curves developed through Monte‐Carlo simulations show that fragility estimates obtained without taking into account vertical base accelerations can be significantly unconservative, especially for relatively large values of the coefficient of friction. It is also found that reasonable estimates of relative displacement response at stories other than the ground in multistorey buildings cannot in general be obtained by simply scaling the ground acceleration to the peak acceleration at the corresponding storey. Failure modes considered in this study are found to be essentially independent of each other, a property that greatly simplifies assessment of conditional limit states. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
6.
唐山地震的超晚期强余震估计 总被引:1,自引:0,他引:1
根据华北历史地震的重复性和免疫性,认为在唐山周围85km,200年内,对6级地震具有一定的免疫性;在研究了唐山地震序列自身的衰减规律后,认为在今后几十几强余震的最大活动水平为5级,发生6级以上土地震的可能性很小。 相似文献
7.
Zhou Cuiying Wang Hongwei Wang Mei and Zhang YuxiaSeismological Bureau of Shandong Province Jinan China Center for Analysis Prediction SSB Beijing China 《中国地震研究》1997,(4)
In order to solve the problem of early estimation of moderately strong aftershock duration time in an earthquake sequence,this study has been conducted.First,the definition of the strong aftershock has been given.It is pointed out that there is a difference in the strong aftershock duration time between the main shock type sequence and the strong earthquake swarm sequence.After dividing the three cases,i.e.,a strong aftershock duration time larger than 1 day,smaller than 1 day,and no strong aftershock occurred in a main shock type sequence by using the pattern recognition method,we gave the rough correlation relation between strong aftershock duration time and first large shock magnitude for two types of sequences.Finally,the judgment index and method of estimating strong aftershock duration times for different sequence types have been given. 相似文献
8.
强余震持续时间的早期估计 总被引:2,自引:0,他引:2
本研究旨在解决地震序列中强余震持续时间的早期估计问题。文中首先给出了强余震的震级定义,指出:主震型与强震群型序列的强作震持续时间存在差异。使用模式识别方法对主震型序列中强余震持续时间大于1天,小于1天及无强余震等3种情况进行划分之后,给出了两类序列的强余震持续时间与序列和第一震震级的粗略相关关系。 相似文献
9.
IntroductionSeismologistsbeganaftershocksequenceinvestigationasearlyasendofthe19thcentury.Theaftershockoccurrencefrequencyhasdifferentmodels,whichincludepowerfunctiondecaymodel(Omori,1894),hyperboladecaymodel(Utsu,1961).Mogi(1962)presentedthattheafter-shockoccurrencefrequencydecayedwithdifferentprinciplesduringdifferenttimephasesaftermainshocks.Henceforthseismologistshavestudiedalargenumberofaftershocksequencesbasedonthesemodels.Chineseseismologistsstudiedthetemporal-spatialcharacteristicsof… 相似文献
10.
IntroductionWhenpropagatingthroughananisotropicmedium,ashearwavesplitsintotwo(quasi)shearwaveswithdifferentpropagationspeedsandpolarizedorthogonally.Owingtotherecentdevel-opmentofseismicobservationsystem,detectionofshearwavessplittingwithverysmalldelaytimesbetweenfasterandslowershearwavesbecameavailableandprovidedpowerfulapproachfordetectionofcrustalanisotropy.Crampin(1978)emphasizedtheroleofalignedmicrocracksasacauseofcrustalanisotropyandpointedoutthatforverticallyalignedmicrocracksthedirecti… 相似文献