全文获取类型
收费全文 | 216篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 22篇 |
地球物理 | 46篇 |
地质学 | 85篇 |
海洋学 | 23篇 |
天文学 | 38篇 |
综合类 | 2篇 |
自然地理 | 8篇 |
出版年
2024年 | 1篇 |
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 3篇 |
2019年 | 7篇 |
2018年 | 12篇 |
2017年 | 8篇 |
2016年 | 19篇 |
2015年 | 5篇 |
2014年 | 9篇 |
2013年 | 9篇 |
2012年 | 12篇 |
2011年 | 19篇 |
2010年 | 12篇 |
2009年 | 18篇 |
2008年 | 15篇 |
2007年 | 6篇 |
2006年 | 13篇 |
2005年 | 3篇 |
2004年 | 7篇 |
2003年 | 8篇 |
2002年 | 3篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有227条查询结果,搜索用时 15 毫秒
111.
Graham Vixie Jason W. Barnes Jacob Bow Stéphane Le Mouélic Sébastien Rodriguez Robert H. Brown Priscilla Cerroni Federico Tosi Bonnie Buratti Christophe Sotin Gianrico Filacchione Fabrizio Capaccioni Angioletta Coradini 《Planetary and Space Science》2012,60(1):52-61
Titan shows its surface through many methane windows in the 1–5 region. Windows at shorter wavelengths also exist, polluted by scattering off of atmospheric haze that reduces the surface contrast. At visible wavelengths, the surface of Titan has been observed by Voyager I, the Hubble Space Telescope, and ground-based telescopes. We present here global surface mapping of Titan using the visible wavelength channels from Cassini's Visual and Infrared Mapping Spectrometer (VIMS). We show global maps in each of the VIMS-V channels extending from 0.35 to 1.05 . We find methane windows at 0.637, 0.681, 0.754, 0.827, 0.937, and and apply an RGB color scheme to the 0.754, 0.827 and windows to search for surface albedo variations. Our results show that Titan appears gray at visible wavelengths; hence scattering albedo is a good approximation of the Bond albedo. Maps of this genre have already been made and published using the infrared channels of VIMS. Ours are the first global maps of Titan shortward of . We compare the older IR maps to the new VIMS-V maps to constrain surface composition. For instance Tui Regio and Hotei Regio, referred to as bright spots in previous papers, do not distinguish themselves at all visible wavelengths. The distinction between the dune areas and the bright albedo spots, however, such as the difference between Xanadu and Senkyo, is easily discernible. We employ an empirically derived algorithm to remove haze layers from Titan, revealing a better look at the surface contrast. 相似文献
112.
Kurt Friese Gerald Schmidt Jorge Carvalho de Lena Dieter W. Zachmann 《Limnologica》2010,40(2):114-125
The artificial reservoir Lagoa da Pampulha in central Brazil has been increasingly affected by sediment deposition and pollution from urban and industrial sources. This study investigates water chemistry and heavy metal concentrations and their fractionation in the lake sediment using ICP-OES, ICP-MS, and XRD analyses. Fractionation analysis was done by sequential extraction under inert gas as well as after oxidation. The lake exhibits a permanent stratification with an oxygen-free hypolimnion below 2 m depth. Nutrient concentrations are enriched for phosphorous components (SRP, PO4). In the sediment it was not possible to detect oxygen. Carbon, sulfur, and most of the analyzed heavy metals are enriched in the top sediment layer with a pronounced downward decrease, indicating the presence of an anthropogenic influence. Statistical analysis, including correlations and a Principal Component Analysis (PCA) of depth-related total concentration data, helps to distinguish presumably anthropogenic heavy metals from geogenic components. Some samples with high element concentrations in the sediment also show elevated concentrations in their pore water. Analyses of element distribution between sediment and pore water suggest a strong bonding of heavy metals to the anoxic sediment. The trend towards elevated solubility in the pore water of oxidized samples is clear for most of the analyzed elements. Fractionation analysis reveals characteristic associations of selected elements to specific mineral bonding forms. In addition, it indicates that the behavior of heavy metals in the sediment is strongly influenced by organic substances. These substances provide buffering against oxidation, acidification, and metal release. The high nutrient loading causes reducing conditions in the lake sediment. These conditions trigger the accumulation of sediments rich in S2−, which stabilizes the fixation of heavy elements. In the future, care must be taken to reduce the supply of contaminants and to prevent the release of heavy metals from sediments dredged for remediation purposes. 相似文献
113.
114.
G. Musacchio S. Falsaperla A. E. Bernhardsdóttir M. A. Ferreira M. L. Sousa A. Carvalho G. Zonno 《Bulletin of Earthquake Engineering》2016,14(7):2069-2086
To comply with the need to spread the culture of earthquake disaster reduction, we rely on strategies that involve education. Risk education is a long-term process that passes from knowledge, through understanding, to choices and actions thrusting preparedness and prevention, over recovery. We set up strategies for prevention that encompass child and adult education, as a bottom-up approach, from raising awareness to reducing potential effects of disruption of society. Analysis of compulsory school education in three European countries at high seismic risk, namely Portugal, Iceland and Italy, reveals that generally there are a few State-backed plans. The crucial aspects of risk education concerning natural hazards are starting age, incompleteness of textbooks, and lack of in-depth studies of the pupils upon completion of their compulsory education cycle. Hands-on tools, immersive environments, and learn-by-playing approaches are the most effective ways to raise interest in children, to provide memory imprint as a message towards a culture of safety. A video game, Treme–treme, was prepared to motivate, educate, train and communicate earthquake risk to players/pupils. The game focuses on do’s and don’ts for earthquake shaking, and allows children to think about what might be useful in the case of evacuation. Education of the general public was addressed using audio-visual products strongly linked to the social, historical and cultural background of each country. Five videos tackled rising of awareness of seismic hazards in Lisbon, the area surrounding Reykjavik, Naples, and Catania, four urban areas prone to earthquake disasters. 相似文献
115.
Mauricio da Rocha Fragoso Gabriel Vieira de Carvalho Felipe Lobo Mendes Soares Daiane Gracieli Faller Luiz Paulo de Freitas Assad Raquel Toste Lívia Maria Barbosa Sancho Elisa Nóbrega Passos Carina Stefoni Böck Bruna Reis Luiz Landau Hernan G. Arango Andrew M. Moore 《Ocean Dynamics》2016,66(3):419-434
116.
Underwater noise pollution has become a major concern in marine habitats. Guanabara Bay, southeastern Brazil, is an impacted area of economic importance with constant vessel traffic. One hundred acoustic recording sessions took place over ten locations. Sound sources operating within 1 km radius of each location were quantified during recordings. The highest mean sound pressure level near the surface was 111.56 ± 9.0 dB re 1 μPa at the frequency band of 187 Hz. Above 15 kHz, the highest mean sound pressure level was 76.21 ± 8.3 dB re 1 μPa at the frequency 15.89 kHz. Noise levels correlated with number of operating vessels and vessel traffic composition influenced noise profiles. Shipping locations had the highest noise levels, while small vessels locations had the lowest noise levels. Guanabara Bay showed noise pollution similar to that of other impacted coastal regions, which is related to shipping and vessel traffic. 相似文献
117.
P. A. A. Lopes R. R. de Carvalho J. L. Kohl-Moreira C. Jones 《Monthly notices of the Royal Astronomical Society》2009,392(1):135-152
We use Sloan Digital Sky Survey (SDSS) data to investigate galaxy cluster properties of the systems first detected within Digitized Second Palomar Observatory Sky Survey. With the high-quality photometry of SDSS, we derived new photometric redshifts and estimated richness and optical luminosity. For a subset of low-redshift ( z ≤ 0.1) clusters, we have used SDSS spectroscopic data to identify groups in redshift space in the region of each cluster, complemented with massive systems from the literature to assure the continuous mass sampling. A method to remove interlopers is applied, and a virial analysis is performed resulting in the estimates of velocity dispersion, mass and a physical radius for each low- z system. We discuss the choice of maximum radius and luminosity range in the dynamical analysis, showing that a spectroscopic survey must be complete to at least M *+ 1 if one wishes to obtain accurate and unbiased estimates of velocity dispersion and mass. We have measured X-ray luminosity for all clusters using archival data from ROSAT All Sky Survey. For a smaller subset (21 clusters), we selected temperature measures from the literature and estimated mass from the M − T X relation, finding that they show good agreement with the virial estimate. However, these two mass estimates tend to disagree with the caustic results. We measured the presence of substructure in all clusters of the sample and found that clusters with substructure have virial masses higher than those derived from T X . This trend is not seen when comparing the caustic and X-ray masses. That happens because the caustic mass is estimated directly from the mass profile, so it is less affected by substructure. 相似文献
118.
Radio frequency geophysical methods are known for being very versatile tools in ground- and groundwater investigation at shallow
depths. They are fast and easy to use and allow a high density of information over large surfaces, which makes them very suitable
for geological mapping sensu lato (faults, lithological contacts, groundwater-bearing structures, vulnerability maps, and
contaminant plumes) and for selecting borehole locations. Significant improvement concerning 2D and 3D modelling of the data
has occurred in recent decades. However, field surveys are very seldom performed in “ideal conditions”—the lack of necessary
transmitters, in the convenient direction, in order to catch the structures in E- and H-pol for modelling purposes, is not
an unusual situation. The present paper shows how the use of RMT and RF-EM is nevertheless of great help and suggests different
ways to explore qualitative data in different geological settings.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
119.
The effect of scour countermeasures on the mechanism of local scour around a cylinder requires clarification in order to develop design methodology for use in practice. Previous investigations on countermeasure performance, though useful, have not provided adequate measurements to support this understanding. In the present investigation, particle image velocimetry(PIV) measurements were acquired at several streamwise-vertical planes in the flow field surrounding a submerged circular cylinder wit... 相似文献
120.
Natural Hazards - There has been an increase in drownings over recent decades in Australia, particularly among rock fishers swept from the edge of rock platforms. Platform morphology is central to... 相似文献