全文获取类型
收费全文 | 490篇 |
免费 | 5篇 |
国内免费 | 6篇 |
专业分类
测绘学 | 23篇 |
大气科学 | 23篇 |
地球物理 | 110篇 |
地质学 | 143篇 |
海洋学 | 30篇 |
天文学 | 107篇 |
综合类 | 7篇 |
自然地理 | 58篇 |
出版年
2021年 | 7篇 |
2019年 | 7篇 |
2018年 | 6篇 |
2017年 | 9篇 |
2016年 | 8篇 |
2015年 | 19篇 |
2014年 | 23篇 |
2013年 | 32篇 |
2012年 | 19篇 |
2011年 | 23篇 |
2010年 | 21篇 |
2009年 | 36篇 |
2008年 | 23篇 |
2007年 | 23篇 |
2006年 | 21篇 |
2005年 | 21篇 |
2004年 | 22篇 |
2003年 | 14篇 |
2002年 | 8篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1973年 | 7篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1969年 | 2篇 |
1968年 | 4篇 |
排序方式: 共有501条查询结果,搜索用时 15 毫秒
61.
Jay S. Fein 《地球物理与天体物理流体动力学》2013,107(1):213-248
AbstractThe effects of the upper boundary condition on the regime diagram and certain characteristics of the convection within a rotating, differentially heated cylindrical anulus of water were studied in the laboratory. It was found that the regime diagram was not substantially affected by the upper boundary condition. However, the thermal amplitude of the baroclinic waves, as a function of parameter space, and, as expected from previous work, the angular drift velocity of those waves were found to be strongly affected by the upper boundary condition. When the upper surface was free, the amplitude changes were explosive and highly non-linear (as discovered earlier by Kaiser, 1970). When the upper surface was rigid, they were smooth and quite linear. The baroclinic wave patterns drifted round the annulus at rates which were in direct response to the imposed “thermal wind”. However, (as previously observed by Koschmieder, 1972), when the upper surface was rigid they drifted approximately ten times more slowly than when it was free. 相似文献
62.
Diwakar Paudel Jay Krishna Thakur Sudhir Kumar Singh Prashant K. Srivastava 《国际地球制图》2015,30(2):218-241
Soil is a vital part of the natural environment and is always responding to changes in environmental factors, along with the influences of anthropogenic factors and land use changes. The long-term change in soil properties will result in change in soil health and fertility, and hence the soil productivity. Hence, the main aim of this paper focuses on the analysis of land use/land cover (LULC) change pattern in spatial and temporal perspective and to present its impact on soil properties in the Merawu catchment over the period of 18?years. Post classification change detection was performed to quantify the decadal changes in historical LULC over the periods of 1991, 2001 and 2009. The pixel to pixel comparison method was used to detect the LULC of the area. The key LULC types were selected for investigation of soil properties. Soil samples were analysed in situ to measure the physicochemical soil properties. The results of this study show remarkable changes in LULC in the period of 18?years. The effect of land cover change on soil properties, soil compaction and soil strength was found to be significant at a level of <0.05. 相似文献
63.
Guangyou Zhu Shuichang Zhang Barry Jay Katz Jin Su Xue Wang Zihui Feng Jie Cui Xingwang Liu 《Chemie der Erde / Geochemistry》2014
The Western Slope of the Songliao Basin is rich in heavy oil resources (>70 × 108 bbl), around which there are shallow gas reservoirs (∼1.0 × 1012 m3). The gas is dominated by methane with a dryness over 0.99, and the non-hydrocarbon component being overwelmingly nitrogen. Carbon isotope composition of methane and its homologs is depleted in 13C, with δ13C1 values being in the range of −55‰ to −75‰, δ13C2 being in the range of −40‰ to −53‰ and δ13C3 being in the range of −30‰ to −42‰, respectively. These values differ significantly from those solution gases source in the Daqing oilfield. This study concludes that heavy oils along the Western Slope were derived from mature source rocks in the Qijia-Gulong Depression, that were biodegraded. The low reservoir temperature (30–50 °C) and low salinity of formation water with neutral to alkaline pH (NaHCO3) appeared ideal for microbial activity and thus biodegradation. Natural gas along the Western Slope appears mainly to have originated from biodegradation and the formation of heavy oil. This origin is suggested by the heavy δ13C of CO2 (−18.78‰ to 0.95‰) which suggests that the methane was produced via fermentation as the terminal decomposition stage of the oil. 相似文献
64.
Two of the features in the Saturnian ring system recently observed by the Voyager 1 spacecraft are (a) the braiding of theF-ring and (b) the radial spokes that rotate across theB-ring. Both of these phenomena are explained by recognizing that the grains that constitute both theF-ring and the spokes are charged to high electrostatic potentials and are sufficiently small to be strongly affected by the magnetic field of the planet. Processes for the charging of the grains are also suggested. 相似文献
65.
We detected excess oscillatory power at 0.25–2.0 Hz in a coronal loop in the 1983 Indonesian total solar eclipse. In this second-generation experiment enlarging upon the work of Pasachoff and Landman (1984), we observed in two frequency channels, one coronal and one continuum, to monitor atmospheric and instrumental effects. We briefly discuss the effects of an oscillation near 1 Hz on the coronal heating problem.Visiting Colleague, Institute for Astronomy, University of Hawaii. 相似文献
66.
67.
68.
69.
70.