全文获取类型
收费全文 | 171篇 |
免费 | 49篇 |
国内免费 | 31篇 |
专业分类
测绘学 | 15篇 |
大气科学 | 67篇 |
地球物理 | 89篇 |
地质学 | 33篇 |
海洋学 | 9篇 |
天文学 | 11篇 |
综合类 | 8篇 |
自然地理 | 19篇 |
出版年
2021年 | 1篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 8篇 |
2016年 | 4篇 |
2015年 | 14篇 |
2014年 | 17篇 |
2013年 | 12篇 |
2012年 | 13篇 |
2011年 | 11篇 |
2010年 | 9篇 |
2009年 | 16篇 |
2008年 | 13篇 |
2007年 | 20篇 |
2006年 | 20篇 |
2005年 | 12篇 |
2004年 | 11篇 |
2003年 | 3篇 |
2002年 | 8篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有251条查询结果,搜索用时 15 毫秒
101.
G. A. Athanasopoulos P. C. Pelekis E. A. Leonidou 《Soil Dynamics and Earthquake Engineering》1999,18(2):5559
The Greek coastal town of Egion on 15 June 1995 was shaken by a strong, small epicentral distance, earthquake that caused heavy damages to buildings and loss of life. The damages were concentrated in the central elevated part of the town whereas the flat coastal region remained almost intact. This non-uniform distribution of damage is studied in this article in terms of surface topography effects by conducting seismic response analyses of a simplified 2-D profile of the town. A dynamic finite element code implementing the equivalent-linear soil behavior (FLUSHPLUS) was used for the analyses and it was found that the step-like topography amplified greatly the intensity of motion without affecting its frequency content. The analyses showed that the motion recorded by an accelerograph installed at the center of the town is in agreement with the computed values; they also indicated a particularly intense amplification close to the crest of the steep slope, where a multi-story RC residential building partially collapsed. In contrast, the level of motion was found to be low at the flat coastal zone of the town where the earthquake damages were insignificant. It is concluded that the characteristic surface topography of the town played an important role in modifying the intensity of base motion. 相似文献
102.
An important research area in oceanographic surveying and mapping is to obtain submarine topography by remote sensing technique, especially by SAR imagery. In this article, problems related to SAR imagery are analyzed to provide references for the further research. 相似文献
103.
格莱尼改正是重力改正的一种,是对球面半径约166.7 km以外地形和均衡造成的重力综合效应的改正,改正后所得格莱尼异常可对应研究区范围内地壳结构特征,具有重要的研究意义.但近年来国内的重力研究中,对格莱尼改正的认识和重要性还不是十分透彻,特别是在大区域研究中,忽略这一远区重力效应可能会对研究结果的解释造成误导.针对这一问题,本文介绍了格莱尼改正的含义、由来与研究历史,指出了在大区域研究中需要考虑格莱尼效应的重要性,以“扇形球壳块”法为例给出了格莱尼改正的计算原理,列举了格莱尼异常在地球物理中的常见应用,并通过重力改正与莫霍面深度反演实例,通过对反演结果的控制点检测与精度评价,指出格莱尼异常反演所得莫霍面埋深更接近地震方法结果,从而表明了格莱尼改正在地球物理研究中的不可忽视性,并指出完全布格改正与格莱尼改正在计算方法上可实现统一. 相似文献
104.
The distribution of soil 137Cs in relation to selected soil and landform properties was studied across a 16 ha hillslope hollow in the Hunter valley, New South Wales, Australia. The hillslope was used as grazing for cattle. Caesium-137 was not significantly related to the amount of sand, silt, or clay, the bulk density, the organic matter content, the slope angle or the relative distance downslope. However, 137Cs was significantly related to the thickness of the soil A horizon. Spatial variations in 137Cs were compared with topographic units and a six-element hillslope model, but there was little correspondence. It was thought that the effects of microtopography could have masked potential interrelationships between 137Cs and broader scale landform parameters. 相似文献
105.
International compilations of marine gravity, such as the International Gravity Bureau (BGI) contain tens of millions of point
data. Lemoine et al. (The Development of the Joint NASA GSFC and the National Imagery and Mapping Agency (NIMA) Geopotential
Model EGM96, NASA/TP-1998-206861) chose not to include any marine gravity in the construction of the global gravity model
EGM96. Instead they used synthetic anomalies derived from altimetry, so that no independent information about Mean Dynamic
Topography (MDT) can be deduced. Software has been developed not only to identify and correct those aspects of marine gravity
data that are unreliable, but to do so in a way that can be applied to very large, ocean-wide data sets. First, we select
only straight-line parts of ship-tracks and fit each one with a high-degree series of Chebyshev polynomials, whose misfit
standard deviation is σ
line and measures the random error associated with point gravity data. Then, network adjustment determines how the gravity datum is offset for each survey.
A free least squares adjustment minimises the gravity anomaly mismatch at line-crossing points, using σ
line to weight the estimate for each line. For a long, well crossed survey, the instrumental drift rate is also adjusted. For
some 42,000 cross-over points in the northern Atlantic Ocean, network adjustment reduces the unweighted standard deviation
of the cross-over errors from 4.03 to 1.58 mGal; when quality weighted, the statistic reduces from 1.32 to 0.39 mGal. The
geodetic MDT is calculated combining the adjusted gravity anomalies and satellite altimetry, and a priori global ocean model
through a new algorithm called the Iterative Combination Method. This paper reports a first demonstration that geodetic oceanography
can characterise the details of basin wide ocean circulation with a resolution better than global ocean circulation models.
The result matches regional models of ocean circulation from hydrography measurements (Geophys Res Lett 29:1896, 2002; J Geophys
Res 108:3251, 2003). 相似文献
106.
Jürgen Oberst Stephan Elgner F. Scott Turner Mark E. Perry Robert W. Gaskell Maria T. Zuber Mark S. Robinson Sean C. Solomon 《Planetary and Space Science》2011,59(15):1918-1924
Analysis of images obtained by the MESSENGER spacecraft during its three flybys of Mercury yields a new estimate for the planet's mean radius of 2439.25±0.69 km, in agreement with results from Mariner 10 and Earth-based observations, as well as with MESSENGER altimeter and occultation data. The mean equatorial radius and polar radius are identical to within error, suggesting that rotational oblateness is negligible when compared with other sources of topography. This result is consistent with the small gravitational oblateness of the planet. Minor differences in radius obtained at different locations reflect regional variations in topography. Residual topography along three limb profiles has a dynamic range of 7.4 km and a root-mean-square roughness of 0.8 km over hemispherical scales. Following MESSENGER's entry into orbit about Mercury in March 2011, we expect considerable additional improvements to our knowledge of Mercury's size and shape. 相似文献
107.
108.
109.
Maria Rosaria Santovito Leonardo Tommasi Andrea Romoli Eamonn Murphy 《Planetary and Space Science》2006,54(7):645-660
This paper presents a definition study of a laser altimeter for the topographic exploration of Mercury. The reference scenario is the BepiColombo mission, a cornerstone mission of European Space Agency (ESA) planned for 2012. BepiColombo will offer the chance to make a remarkable new contribution to our knowledge of the Solar System, by venturing into the hot region near the Sun and exploring Mercury, the most enigmatic of the earth's sisters among the terrestrial planets. First images of Mercury surface were acquired by Mariner 10 in 1974 and 1975 offering a coverage and resolution comparable to Earth-based telescopic coverage of the Moon before spaceflight. BepiColombo mission can be very beneficial by using an optical rangefinder for Mercury exploration. In fact starting from the first missions in 1970s until today, laser altimeters have been demonstrating to be particularly appropriate as part of the scientific payload whenever the topography of earth, lunar and planetary surface is the scientific objective of a space mission.Our system design is compliant to Mercury Polar Orbiter (MPO) of the mission. System performance analysis is carried out simulating main hermean topographic features and the potential targets on the planet by means of analytical models and computer codes and several plot are presented to analyse the performance of the instrument. 相似文献
110.
Stereo images obtained during the DS1 flyby were analyzed to derive a topographic model for the nucleus of Comet 19P/Borrelly for morphologic and photometric studies. The elongated nucleus has an overall concave shape, resembling a peanut, with the lower end tilted towards the camera. The bimodal character of surface-slopes and curvatures support the idea that the nucleus is a gravitational aggregate, consisting of two fragments in contact. Our photometric modeling suggests that topographic shading effects on Borrelly's surface are very minor (<10%) at the given resolution of the terrain model. Instead, albedo effects are thought to dominate Borrelly's large variations in surface brightness. With 90% of the visible surface having single scattering albedos between 0.008 and 0.024, Borrelly is confirmed to be among the darkest of the known Solar System objects. Photometrically corrected images emphasize that the nucleus has distinct, contiguous terrains covered with either bright or dark, smooth or mottled materials. Also, mapping of the changes in surface brightness with phase angle suggests that terrain roughness at subpixel scale is not uniform over the nucleus. High surface roughness is noted in particular near the transition between the upper and lower end of the nucleus, as well as near the presumed source region of Borrelly's main jets. Borrelly's surface is complex and characterized by distinct types of materials that have different compositional and/or physical properties. 相似文献