全文获取类型
收费全文 | 2063篇 |
免费 | 716篇 |
国内免费 | 1468篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 2308篇 |
地球物理 | 323篇 |
地质学 | 586篇 |
海洋学 | 653篇 |
天文学 | 25篇 |
综合类 | 123篇 |
自然地理 | 218篇 |
出版年
2024年 | 33篇 |
2023年 | 55篇 |
2022年 | 78篇 |
2021年 | 106篇 |
2020年 | 119篇 |
2019年 | 132篇 |
2018年 | 118篇 |
2017年 | 140篇 |
2016年 | 138篇 |
2015年 | 148篇 |
2014年 | 170篇 |
2013年 | 223篇 |
2012年 | 176篇 |
2011年 | 166篇 |
2010年 | 142篇 |
2009年 | 206篇 |
2008年 | 196篇 |
2007年 | 205篇 |
2006年 | 174篇 |
2005年 | 188篇 |
2004年 | 168篇 |
2003年 | 138篇 |
2002年 | 139篇 |
2001年 | 119篇 |
2000年 | 110篇 |
1999年 | 83篇 |
1998年 | 96篇 |
1997年 | 93篇 |
1996年 | 72篇 |
1995年 | 61篇 |
1994年 | 63篇 |
1993年 | 45篇 |
1992年 | 31篇 |
1991年 | 35篇 |
1990年 | 9篇 |
1989年 | 12篇 |
1988年 | 9篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 11篇 |
1980年 | 2篇 |
1977年 | 5篇 |
排序方式: 共有4247条查询结果,搜索用时 15 毫秒
181.
Analysis of two continuous, high‐resolution palaeo‐flood records from southern Norway reveals that the frequency of extreme flood events has changed significantly during the Holocene. During the early and middle Holocene, flood frequency was low; by contrast, it was high over the last 2300 years when the mean flood frequency was about 2.5–3.0 per century. The present regional discharge regime is dominated by spring/summer snowmelt, and our results indicate that the changing flood frequency cannot be explained by local conditions associated with the respective catchments of the two lakes, but rather long‐term variations of solid winter precipitation and related snowmelt. Applying available instrumental winter precipitation data and associated sea‐level pressure re‐analysis data as a modern analogue, we document that atmospheric circulation anomalies, significantly different from the North Atlantic Oscillation (NAO), have some potential in explaining the variability of the two different palaeo‐flood records. Centennial‐scale patterns in shifting flood frequency might be indicative of shifts in atmospheric circulation and shed light on palaeo‐pressure variations in the North Atlantic region, in areas not influenced by the NAO. Major shifts are found at about 2300, 1200 and 200 years ago (cal. a BP). Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
182.
HF radar stations (utilizing the spaced-antenna partial-reflection technique) located at Adelaide (35°S, 138°E) and Mawson Station (67°S, 63°E) have observed horizontal mesospheric winds continuously since mid-1984. Observations in the period 1984–87 are compared with the Northern Hemisphere [latitude conjugate] stations of Kyoto (35°N, 136°E) and Poker Flat (65°N, 147°W), and with satellite-derived circulation models. Particular reference is made to the equinoctial changeovers in zonal flow and to the temporal and altitude variations in the planetary wave activity at Mawson and Adelaide. 相似文献
183.
Timothy J. Dunkerton 《Pure and Applied Geophysics》1989,130(2-3):243-262
The body force circulation problem of Eliassen is extended to spherical geometry and a quasi-compressible atmosphere using the zonally symmetric tidal theory. The concept of body force circulation is generalized to include the effects of mechanical friction and Newtonian cooling. This viewpoint is conceptually advantageous when the circulation is driven by body forces against radiative relaxation. The resulting linear theory is qualitatively useful in middle atmosphere applications, including the equatorial momentum source for which an analytic solution has not been given previously. Further generalizations of the theory are possible by including dynamical and photochemical feedback effects. 相似文献
184.
应用对应分析等方法分析了江淮流域汛期(5月~9月)降水的时空分布特征,在此基础上按降水旬际变化特征将论域初划为4个区域,最后讨论了各降水区降水异常的500hPa低阶流场背景. 相似文献
185.
186.
NumericalModellingoftheEffectsofOzoneontheSummerAtmosphericCirculationWangQianqian(王谦谦);WangYinhui(汪迎辉);SongYu(宋煜)(Naminginst... 相似文献
187.
MODULATION OF ATMOSPHERIC THERMAL AND MECHANICAL FORCINGS AND NUMERICAL MODELING OF MEAN MERIDIONAL CIRCULATION 下载免费PDF全文
Upon investigating the relative locations of internal and external forcing and the resultant mean meridional circulation,it was found that thermal forcing and mechanical forcing for the formation of atmospheric mean meridional circulation are modulated by a certain ratio.This ratio is determined by the inherent baroclinity,static stability and absolute vorticity of the atmosphere.By employing a parameterization scheme for radiative heating and condensation heating,together with the analysisdata of the European Center for Medium-range Weather Forecasts,the mean meridional circulation for January wassimulated numerically.It was found that latent heat release in the tropics may result in the formation of double-layeredHadley circulation,so do the eddy momentum transfer processes.On the other hand,mean meridional circulations in extra-tropics are mainly determined by external momentum forcing and atmospheric properties of eddy momentum andheat transfer. 相似文献
188.
189.
在合适的实验参数下(热力Rossby数R_(OT)=0.1,Taylor数T_a=2.2 ×10~7),在旋转斜压流中,大尺度地形强迫造成低频振荡以及大气环流中的“阻塞”流型。这是由于地形强迫造成的准静止波与行进波的相互作用及共振引起的。地形把波数单一的流动变成多波数的流动。地形强迫使波数减少。 相似文献
190.