全文获取类型
收费全文 | 54篇 |
免费 | 4篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 5篇 |
地球物理 | 10篇 |
地质学 | 28篇 |
海洋学 | 1篇 |
天文学 | 11篇 |
自然地理 | 2篇 |
出版年
2020年 | 1篇 |
2018年 | 1篇 |
2017年 | 4篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2012年 | 4篇 |
2011年 | 2篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 2篇 |
2007年 | 3篇 |
2006年 | 6篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有58条查询结果,搜索用时 796 毫秒
11.
M. Obri . Ivezi P. N. Best R. H. Lupton C. Tremonti J. Brinchmann M. A. Agüeros G. R. Knapp J. E. Gunn C. M. Rockosi D. Schlegel D. Finkbeiner M. Gaea V. Smoli S. F. Anderson W. Voges M. Juri R. J. Siverd W. Steinhardt A. S. Jagoda M. R. Blanton D. P. Schneider 《Monthly notices of the Royal Astronomical Society》2006,370(4):1677-1698
12.
13.
Devi Devapal S. S. Kumar Christy Jojy 《Journal of the Indian Society of Remote Sensing》2017,45(3):443-450
Synthetic aperture radar (SAR) is a day and night, all weather satellite imaging technology. Inherent property of SAR image is speckle noise which produces granular patterns in the image. Speckle noise occurs due to the interference of backscattered echo from earth’s rough surface. There are various speckle reduction techniques in spatial domain and transform domain. Non local means filtering (NLMF) is the technique used for denoising which uses Gaussian weights. In NLMF algorithm, the filtering is performed by taking the weighted mean of all the pixels in a selected search area. The weight given to the pixel is based on the similarity measure calculated as the weighted Euclidean distance over the two windows. Non local means filtering smoothes out homogeneous areas but edges are not preserved. So a discontinuity adaptive weight is used in order to preserve heterogeneous areas like edges. This technique is called as discontinuity adaptive non local means filtering and is well-adapted and robust in the case of Additive White Gaussian Noise (AWGN) model. But speckle is a multiplicative random noise and hence Euclidean distance is not a good choice. This paper presents evaluation results of using different distance measures for improving the accuracy of the Non local means filtering technique. The results are verified using real and synthetic images and from the results it can be concluded that the usage of Manhattan distance improves the accuracy of NLMF technique. Non local approach is used as a preprocessing or post processing technique for many denoising algorithms. So improving NLMF technique would help improving many of the existing denoising techniques. 相似文献
14.
Christy B. Till Timothy L. Grove Anthony C. Withers 《Contributions to Mineralogy and Petrology》2012,164(6):1083-1085
The comment of Green et al. debates the interpretation of the temperature of the H2O-saturated peridotite solidus and presence of silicate melt in the experiments of Till et al. (Contrib Mineral Petrol 163:669–688, 2012) at <1,000?°C. The criticisms presented in their comment do not invalidate any of the most compelling observations of Till et al. (Contrib Mineral Petrol 163:669–688, 2012) as discussed in the following response, including the changing minor element and Mg# composition of the solid phases with increasing temperature in our experiments with 14.5?wt% H2O at 3.2?GPa, as well as the results of our chlorite peridotite melting experiments with 0.7?wt% H2O. The point remains that Till et al. (Contrib Mineral Petrol 163:669–688, 2012) present data that call into question the H2O-saturated peridotite solidus temperature preferred by Green (Tectonophysics 13(1–4):47–71, 1972; Earth Planet Sci Lett 19(1):37–53, 1973; Can Miner 14:255–268, 1976); Millhollen et al. (J Geol 82(5):575–587, 1974); Mengel and Green (Stability of amphibole and phlogopite in metasomatized peridotite under water-saturated and water-undersaturated conditions, Geological Society of Australia Special Publication, Blackwell, pp 571-581, 1989); Wallace and Green (Mineral Petrol 44:1–19, 1991) and Green et al. (Nature 467(7314):448–451, 2010). 相似文献
15.
The direct-push permeameter (DPP) is a promising approach for obtaining high-resolution information about vertical variations in hydraulic conductivity (K) in shallow unconsolidated settings. This small-diameter tool, which consists of a short screened section with a pair of transducers inset in the tool near the screen, is pushed into the subsurface to a depth at which a K estimate is desired. A short hydraulic test is then performed by injecting water through the screen at a constant rate (less than 4 L/min) while pressure changes are monitored at the transducer locations. Hydraulic conductivity is calculated using the injection rate and the pressure changes in simple expressions based on Darcy's Law. In units of moderate or higher hydraulic conductivity (more than 1 m/d), testing at a single level can be completed within 10 to 15 min. Two major advantages of the method are its speed and the insensitivity of the K estimates to the zone of compaction created by tool advancement. The potential of the approach has been assessed at two extensively studied sites in the United States and Germany over a K range commonly faced in practical field investigations (0.02 to 500 m/d). The results of this assessment demonstrate that the DPP can provide high-resolution K estimates that are in good agreement with estimates obtained through other means. 相似文献
16.
Zr-in-rutile thermometry in HP/UHP eclogites from Western China 总被引:5,自引:0,他引:5
Guibin Zhang David J. Ellis Andrew G. Christy Lifei Zhang Shuguang Song 《Contributions to Mineralogy and Petrology》2010,160(3):427-439
Four Zr-in-rutile thermometry calibrations are applied to eclogites from Western China. Here, we show that if rutile grows
in equilibrium with Qtz and Zrn, and is isolated inside garnet, it preserves its Zr composition and does not undergo compositional
change due to cation exchange with the host garnet. It thus preserves the composition for the P–T conditions of its formation and the growth zoning of the host garnet. For the HP/UHP metamorphic temperature, the Tomkins
et al. (J Metamorph Geol 25:703–713, 2007) calibration yields temperatures that agree well with previous studies, whereas the other three calibrations (Zack et al.
in Contrib Mineral Petrol 148:471–488, 2004; Watson et al. in Contrib Mineral Petrol 151:413–433, 2006; Ferry and Watson in Contrib Mineral Petrol in 154:429–437, 2007), which do not include a pressure correction, give systematically lower temperatures. Zr contents of rutile inclusions within
garnet show systematic decrease from garnet core to rim. The rutile inclusions in garnet rims contain the lowest Zr content,
similar to that in the matrix. Analyses confirm that the pressure plays a significant role in modifying the primary temperature
dependence of the Zr content of rutile. Rutiles trapped in garnets are unable to re-equilibrate easily during retrogression,
but those in the matrix can do so, providing retrograde P–T path information. 相似文献
17.
18.
D. J. Large A. G. Christy A. E. Fallick 《Contributions to Mineralogy and Petrology》1994,116(1-2):108-116
Poorly crystalline carbonaceous matter was observed in chlorite to sillimanite grade metasediments from the Trois Seigneurs Massif, in contrast to other studies of carbon crystallinity which observed well crystallised graphite under upper greenschist facies conditions. Using transmission electron microscopy four types of carbon particle were identified; globular carbon, composite flakes, homogeneous flakes and crystalline graphite. Globular carbon and composite flakes are poorly crystalline microporous carbon. Homogeneous flakes decompose in the electron beam and are probably composed of heavy volatile hydrocarbons. Graphite is confined to samples from retrograde shear zones and often occurs with globular carbon. The lack of graphitisation in metasediments is probably a consequence of the microporous structure of the carbonaceous matter combined with low f
O
2. The preservation of carbonaceous matter in the Trois Seigneurs metasediments is not compatible with the metasediments having been externally buffered by a high X
H2O fluid syn-metamorphism. An alternative hypothesis of internal buffering is preferred to explain the carbonaceous matter in the Trois Seigneurs metasediments. 相似文献
19.
We examine to what degree we can expect to obtain accurate temperature trends for the last two decades near the surface and
in the lower troposphere. We compare temperatures obtained from surface observations and radiosondes as well as satellite-based
measurements from the Microwave Soundings Units (MSU), which have been adjusted for orbital decay and non-linear instrument-body
effects, and reanalyses from the European Centre for Medium-Range Weather Forecasts (ERA) and the National Centre for Environmental
Prediction (NCEP). In regions with abundant conventional data coverage, where the MSU has no major influence on the reanalysis,
temperature anomalies obtained from microwave sounders, radiosondes and from both reanalyses agree reasonably. Where coverage
is insufficient, in particular over the tropical oceans, large differences are found between the MSU and either reanalysis.
These differences apparently relate to changes in the satellite data availability and to differing satellite retrieval methodologies,
to which both reanalyses are quite sensitive over the oceans. For NCEP, this results from the use of raw radiances directly
incorporated into the analysis, which make the reanalysis sensitive to changes in the underlying algorithms, e.g. those introduced
in August 1992. For ERA, the bias-correction of the one-dimensional variational analysis may introduce an error when the satellite
relative to which the correction is calculated is biased itself or when radiances change on a time scale longer than a couple
of months, e.g. due to orbit decay. ERA inhomogeneities are apparent in April 1985, October/November 1986 and April 1989.
These dates can be identified with the replacements of satellites. It is possible that a negative bias in the sea surface
temperatures (SSTs) used in the reanalyses may have been introduced over the period of the satellite record. This could have
resulted from a decrease in the number of ship measurements, a concomitant increase in the importance of satellite-derived
SSTs, and a likely cold bias in the latter. Alternately, a warm bias in SSTs could have been caused by an increase in the
percentage of buoy measurements (relative to deeper ship intake measurements) in the tropical Pacific. No indications for
uncorrected inhomogeneities of land surface temperatures could be found. Near-surface temperatures have biases in the boundary
layer in both reanalyses, presumably due to the incorrect treatment of snow cover. The increase of near-surface compared to
lower tropospheric temperatures in the last two decades may be due to a combination of several factors, including high-latitude
near-surface winter warming due to an enhanced NAO and upper-tropospheric cooling due to stratospheric ozone decrease.
Received: 5 May 1999 / Accepted: 15 December 1999 相似文献
20.