全文获取类型
收费全文 | 3450篇 |
免费 | 642篇 |
国内免费 | 942篇 |
专业分类
测绘学 | 281篇 |
大气科学 | 696篇 |
地球物理 | 784篇 |
地质学 | 1699篇 |
海洋学 | 544篇 |
天文学 | 117篇 |
综合类 | 440篇 |
自然地理 | 473篇 |
出版年
2024年 | 20篇 |
2023年 | 67篇 |
2022年 | 176篇 |
2021年 | 204篇 |
2020年 | 189篇 |
2019年 | 190篇 |
2018年 | 218篇 |
2017年 | 197篇 |
2016年 | 225篇 |
2015年 | 201篇 |
2014年 | 255篇 |
2013年 | 209篇 |
2012年 | 193篇 |
2011年 | 203篇 |
2010年 | 221篇 |
2009年 | 205篇 |
2008年 | 169篇 |
2007年 | 157篇 |
2006年 | 152篇 |
2005年 | 118篇 |
2004年 | 103篇 |
2003年 | 142篇 |
2002年 | 204篇 |
2001年 | 142篇 |
2000年 | 112篇 |
1999年 | 108篇 |
1998年 | 98篇 |
1997年 | 112篇 |
1996年 | 79篇 |
1995年 | 66篇 |
1994年 | 64篇 |
1993年 | 53篇 |
1992年 | 39篇 |
1991年 | 24篇 |
1990年 | 22篇 |
1989年 | 15篇 |
1988年 | 20篇 |
1987年 | 11篇 |
1986年 | 9篇 |
1985年 | 11篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1958年 | 4篇 |
1957年 | 1篇 |
排序方式: 共有5034条查询结果,搜索用时 62 毫秒
1.
Dynamic modelling of retrogressive landslides with emphasis on the role of clay sensitivity
下载免费PDF全文
![点击此处可从《国际地质力学数值与分析法杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This paper presents a detailed numerical study of the retrogressive failure of landslides in sensitive clays. The dynamic modelling of the landslides is carried out using a novel continuum approach, the particle finite element method, complemented with an elastoviscoplastic constitutive model. The multiwedge failure mode in the collapse is captured successfully, and the multiple retrogressive failures that have been widely observed in landslides in sensitive clays are reproduced with the failure mechanism, the kinematics, and the deposition being discussed in detail. Special attention has been paid to the role of the clay sensitivity on each retrogressive failure as well as on the final retrogression distance and the final run‐out distance via parametric studies. Moreover, the effects of the viscosity of sensitive clays on the failure are also investigated for different clay sensitivities. 相似文献
2.
1 IntroductionAccordingtogeologicalstructure ,theGansu Ningxia Qinghaiareabelongstothenortheastmar ginofQinghai Tibetblock .Thisareahasbeenpaidmuchattentionby geo specialistsinChinaandabroadbecauseofitssignificanttectonicmovement,itsintensiveseismicity ,anditsimportanceinearth quakehazardmitigation .IntheDevelopmentPro gramonNationalKeyBasicResearchesundertheProject“MechanismandPredictionofContinentalStrongEarthquakes”,themechanismsofcontinen talstrongearthquakesarestudied ,usinghypo… 相似文献
3.
CHANGE OF NUTRIENT IMPORT AND EXPORT IN PROCESS OF RAINFALL IN AILAO MOUNTAIN OF YUNNAN PROVINCEGanJianmin(甘健民);XueJingyi(薛敬意... 相似文献
4.
广西海洋资源丰富 ,品种繁多 ,为了更好开发 ,建议从法制、宣传教育、普及海洋资源有关知识 ,提高人们整体素质做起 ,进一步抓住机遇 ,合理开发 ,才能取得良好效益 ,达到预定目标 相似文献
5.
薛建康 《成都信息工程学院学报》1990,(1)
本文针对冬半年高原低涡几个不同源地的低涡生成背景,着重分析500hpa环流场,指出:地形对低涡生成是非常重要的条件,但一定范围内有利的环境流场也是低涡生成不可缺少的外部条件。并给出了不同涡源区有利于低涡发生,发展的500hpa环流形势。 相似文献
6.
青藏块体东北缘断层形变与中强地震 总被引:7,自引:4,他引:3
对祁连山-海原断裂带近期断层形变特征进行了初步研究,发现多场地,大范围的断层活动异常是中等强度地震发生的显著背景,并且往往与大陆地震活动的阶段性总体状况相呼应;区域形变存在明显的特征量,包括特征形态和特征时间,同一场地在不同地震前的异常特征具有重复性,但会受到背景差异显著的不同地震的影响,目前形变状况表明研究区仍具有发生中强地震的地壳运动背景。 相似文献
7.
8.
Hong-Guang Wang Guo-Jun Qiao Ren-Xin XuDepartment of Astronomy Peking University Beijing 《中国天文和天体物理学报》2003,3(5):443-452
The inner vacuum gap model has become the foundation stone of most theories on pulsar radio emission. The fundamental picture of this model is the sparking, which was conjectured to be induced by magnetic absorption of background gamma photons. However, a question is, can the sparking be triggered in the millisecond pulsars (MSPs) with magnetic fields (B) only about 108 G? We investigate this problem by including the pair production above the inner gap. Under the assumption that the magnetic field is dipolar, our results show the background gamma-ray emission can not be the key factor that triggers the sparking, at least not in MSPs with B - 108 G, if the temperature in the polar cap region is only so high as is observed (< 4 × 106 K). Some other mechanisms are required. 相似文献
9.
Tidal effects on temperature front in the Yellow Sea 总被引:5,自引:0,他引:5
Temperature front (TF) is one of the important features in the Yellow Sea, which forms in spring, thrives in summer, and fades
in autumn as thermocline declines. TF intensity ⋎S
T
⋎ is defined to describe the distribution of TF. Based on the MASNUM wave-tide-circulation coupled model, temperature distribution
in the Yellow Sea was simulated with and without tidal effects. Along 36°N, distribution of TF from the simulated results
are compared with the observations, and a quantitative analysis is introduced to evaluate the tidal effects on the forming
and maintaining processes of the TF. Tidal mixing and the circulation structure adapting to it are the main causes of the
TF.
Supported by the National Basic Research Program of China (No. G1999043809) and the National Science Foundation of China (No.
49736190). 相似文献
10.
ASCA observations of the two Type Ⅱ AGNs,NGC7314 and NGC 7582,show clear variations in the broad X-ray band(0.4-10keV)on short timescales-10^4s.Spectral analysis indicates that they bot have an absorbed hard X-ray component and an unabsorbed soft“excess” component.To clarify the origin of the latter,we made a cross-correlation analysis of the two components.The results show that,for NGC7314,the soft X-ray variability is proportional to that of the hard X-ray component.This indicates that the active nucleus of NGC 7314 must be partially covered and so the soft emission is a “leaking” of the variable hard component.For NGC 7582,there is no detectable variability in the soft component, although there is a definite one in the hard component.This indicates that the variable nucleus of NGC 7582 must be fully blocked by absorbing matter,and the soft emission is most likely the scattered component predicted by the AGN unified model. 相似文献