全文获取类型
收费全文 | 400篇 |
免费 | 20篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 8篇 |
大气科学 | 16篇 |
地球物理 | 110篇 |
地质学 | 153篇 |
海洋学 | 28篇 |
天文学 | 92篇 |
自然地理 | 18篇 |
出版年
2023年 | 3篇 |
2022年 | 10篇 |
2021年 | 3篇 |
2020年 | 16篇 |
2019年 | 17篇 |
2018年 | 15篇 |
2017年 | 16篇 |
2016年 | 25篇 |
2015年 | 15篇 |
2014年 | 14篇 |
2013年 | 16篇 |
2012年 | 25篇 |
2011年 | 29篇 |
2010年 | 18篇 |
2009年 | 27篇 |
2008年 | 20篇 |
2007年 | 33篇 |
2006年 | 18篇 |
2005年 | 21篇 |
2004年 | 16篇 |
2003年 | 12篇 |
2002年 | 13篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 6篇 |
1998年 | 2篇 |
1997年 | 5篇 |
1996年 | 1篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有425条查询结果,搜索用时 31 毫秒
241.
Tourmaline nodules from Capo Bianco aplite (Elba Island,Italy): an example of diffusion limited aggregation growth in a magmatic system 总被引:1,自引:0,他引:1
The morphology of tourmaline nodules occurring in the Capo Bianco aplite (Elba Island, Italy) is studied. Outcrop features
indicate that tourmaline nodules are the product of magmatic crystallization, as they are aligned along flow fields developed
within the magmatic hosting mass. Mesoscopic observations indicate that nodule morphologies are very variable, from rounded
to dendritic. Morphometric analyses show that tourmaline nodules are fractals and that fractal dimension quantifies their
degree of irregularity. Numerical simulations of nodule growth are performed by using a Diffusion-Limited Aggregation process.
The presence in natural samples of nodules with different morphologies is explained by considering a chaotic magmatic system
characterized by a complex interplay between growth rate in different dynamical regions, latent heat of crystallization, and
local convection dynamics. It is suggested that higher growth rates correspond to growth of tourmaline nodules in dynamical
regions where the transfer of nutrients is very efficient. In such conditions, the latent heat released by the growing nodule
is high, inducing strong local convection dynamics, destabilizing the nodule interface, and promoting the formation of dendritic
morphologies. On the contrary, the growth of nodules in dynamical regions characterized by weak transfer of nutrients is inhibited
leading to weak local convection dynamics and, consequently, to the formation of rounded morphologies. 相似文献
242.
243.
244.
245.
Asten Michael W. Yong Alan Foti Sebastiano Hayashi Koichi Martin Antony J. Stephenson William J. Cassidy John F. Coleman Jacie Nigbor Robert Castellaro Silvia Chimoto Kosuke Cornou Cécile Cho Ikuo Hayashida Takumi Hobiger Manuel Kuo Chun-Hsiang Macau Albert Mercerat E. Diego Molnar Sheri Pananont Passakorn Pilz Marco Poovarodom Nakhorn Sáez Esteban Wathelet Marc Yamanaka Hiroaki Yokoi Toshiaki Zhao Don 《Journal of Seismology》2022,26(4):757-780
Journal of Seismology - Site response is a critical consideration when assessing earthquake hazards. Site characterization is key to understanding site effects as influenced by seismic site... 相似文献
246.
Diego?F.?NarvaezEmail authorView authors OrcID profile Estelle?F.?Rose-Koga Pablo?Samaniego Kenneth?T.?Koga Silvana?Hidalgo 《Contributions to Mineralogy and Petrology》2018,173(10):80
Constraining arc magma sources at continental arc settings is a delicate task, because chemical signatures from crustal processes obscure the slab and mantle signatures. Here, we present major, trace, and volatile element compositions of olivine-hosted melt inclusions (Fo82–89) selected from the most primitive lavas (Mg# >?60) from two Ecuadorian volcanoes (Puñalica and Sangay) situated at the southern termination of the Andean Northern Volcanic Zone. Melt inclusions (MI) from Puñalica are nepheline normative and have basaltic-to-basaltic-andesite compositions (45–56 wt% SiO2) similar to peridotite-derived melts. Sangay MI is also nepheline normative, with high CaO (up to 16 wt% and CaO/Al2O3?<?1) and low silica contents (41.9–44.5 wt%) pointing out an amphibole-bearing clinopyroxenite source. Both volcanoes display volatile-rich compositions (up to 6100 ppm Cl, 2200 ppm F, and 6700 ppm S). These MI cannot be related to their host lavas by fractional crystallization, implying that they represent true primitive liquids. The source of Puñalica MI was metasomatized by slab-derived melts that imprints its low Ba/Th, Sr/Th, and high Th/La (average values of 66, 129, and 0.22, respectively). On the contrary, the slab component added to the source of Sangay MI has a higher Ba/Th, Sr/Th, and low Th/La (average values of 261, 517, and 0.11, respectively) which could suggest a relative contribution of aqueous fluids. This dichotomy is related to the presence of the Grijalva Fracture Zone that separates a younger and hotter oceanic crust to the north (below Puñalica) from a colder and older oceanic crust to the south (below Sangay). 相似文献
247.
248.
249.
Cerón Wilmar Loaiza Molina-Carpio Jorge Ayes Rivera Irma Andreoli Rita Valeria Kayano Mary Toshie Canchala Teresita 《Natural Hazards》2020,103(1):767-783
Natural Hazards - This article assesses the consistency of the satellite precipitation estimate CHIRPS v.2 to describe the spatiotemporal rainfall variability in the La Plata Basin (LPB), the... 相似文献
250.
Diego Tonolla Mark S. Lorang Kurt Heutschi Klement Tockner 《Aquatic Sciences - Research Across Boundaries》2009,71(4):449-462
The hydrogeomorphology and ecology of rivers and streams has been subject of intensive research for many decades. However,
hydraulically-generated acoustics have been mostly neglected, even though this physical attribute is a robust signal in fluvial
ecosystems. Physical generated underwater sound can be used to quantify hydro-geomorphic processes, to differentiate among
aquatic habitat types, and it has implications on the behavior of organisms. In this study, acoustic signals were quantified
in a flume by varying hydro-geomorphic drivers and the related turbulence and bubble formation. The acoustic signals were
recorded using two hydrophones and analyzed using a signal processing software, over 31 third-octave bands (20 Hz–20 kHz),
and then combined in 10 octave bands. The analytical method allowed for a major improvement of the signal-to-noise ratio,
therefore greatly reducing the uncertainty in our analyses. Water velocity, relative submergence, and flow obstructions were
manipulated in the flume and the resultant acoustic signals recorded. Increasing relative submergence ratio and water velocity
were important for reaching a turbulence threshold above which distinct sound levels were generated. Increases in water velocity
resulted in increased sound levels over a wide range of frequencies. The increases in sound levels due to relative submergence
of obstacles were most pronounced in midrange frequencies (125 Hz–2 kHz). Flow obstructions in running waters created turbulence
and air bubble formation, which again produced specific sound signatures. 相似文献