全文获取类型
收费全文 | 293篇 |
免费 | 17篇 |
国内免费 | 2篇 |
专业分类
大气科学 | 33篇 |
地球物理 | 67篇 |
地质学 | 88篇 |
海洋学 | 34篇 |
天文学 | 71篇 |
自然地理 | 19篇 |
出版年
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 11篇 |
2016年 | 10篇 |
2015年 | 15篇 |
2014年 | 7篇 |
2013年 | 7篇 |
2012年 | 15篇 |
2011年 | 11篇 |
2010年 | 11篇 |
2009年 | 22篇 |
2008年 | 23篇 |
2007年 | 19篇 |
2006年 | 29篇 |
2005年 | 16篇 |
2004年 | 8篇 |
2003年 | 10篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 10篇 |
1998年 | 14篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 8篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1973年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有312条查询结果,搜索用时 147 毫秒
311.
Andrea Muñoz-Ibáñez Jordi Delgado-Martín Elisa Grande-García 《Geophysical Prospecting》2019,67(4):761-783
Granular materials submitted to uniaxial compression undergo pore space reduction due to mechanisms such as particle rearrangement and grain crushing. These changes in the internal structure of the material release energy in the form of elastic waves that can be detected by sensors sensitive to acoustic emission. In this study, Acoustic emission monitoring with a wavelet-based signal processing technique is used to identify the various mechanisms occurring during high-pressure sand compaction. Particle movement, grain failure, friction between grains and the surface of the compression cell and intergranular friction are studied. Acoustic emission data recorded during these simplified tests are used to characterize each phenomenon. Wavelet transform analyses allow the identification of useful features, making possible frequency discrimination among sliding, rolling, friction and grain fragmentation processes. For instance, we observe that at low stress, grain flow is characterized by the lowest centroid and peak frequencies, while at greater stresses, intergranular friction and grain fragmentation have the higher values. In the tests performed, the stress–strain evolution and final condition of the tested sand are broadly consistent, irrespective of the condition employed: continuous, stepwise or even variable loading rate or temperature. However, Acoustic emission data manifest much more complex behaviour (including thermal, load-rate dependency and delayed fragmentation phenomena) than that suggested by stress–strain relationships. At low stress levels, grain flow (sliding/rolling) is a relevant strain-accommodation mechanism, but so is crushing due to the effect of concentrated forces at the grain contact level. At high stresses, when crushing is generalized, intergranular friction is also a relevant phenomenon due to the increase in the coordination number produced by previous fragmentation. 相似文献
312.
Diaz John Carnevale Shannon Millett Cheryl Abd-Elrahman Amr Britt Katie 《Natural Hazards》2020,103(2):1905-1916
Natural Hazards - Natural ecosystems are characterized as dynamic systems that evolve through natural patterns of disturbance. Land managers can work within this system of natural disturbance by... 相似文献