全文获取类型
收费全文 | 692篇 |
免费 | 26篇 |
国内免费 | 3篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 74篇 |
地球物理 | 162篇 |
地质学 | 216篇 |
海洋学 | 65篇 |
天文学 | 87篇 |
综合类 | 4篇 |
自然地理 | 109篇 |
出版年
2022年 | 7篇 |
2021年 | 7篇 |
2020年 | 11篇 |
2019年 | 16篇 |
2018年 | 10篇 |
2017年 | 12篇 |
2016年 | 23篇 |
2015年 | 24篇 |
2014年 | 21篇 |
2013年 | 40篇 |
2012年 | 32篇 |
2011年 | 30篇 |
2010年 | 26篇 |
2009年 | 39篇 |
2008年 | 23篇 |
2007年 | 34篇 |
2006年 | 21篇 |
2005年 | 29篇 |
2004年 | 20篇 |
2003年 | 26篇 |
2002年 | 26篇 |
2001年 | 25篇 |
2000年 | 18篇 |
1999年 | 15篇 |
1998年 | 20篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 8篇 |
1986年 | 9篇 |
1985年 | 4篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 11篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1973年 | 8篇 |
1969年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有721条查询结果,搜索用时 281 毫秒
621.
At present, Bangladesh has a flood forecasting lead time of only 3 days or so. There is demand for a forecasting lead time of a month to a season. The primary objectives of this paper are to study the variability and predictability of seasonal flooding in Bangladesh, as revealed by large‐scale predictors of the climate across the watersheds. To explore the source of predictability, accessible Bangladesh hydrological indicators are related to large‐scale oceanic variability and to large‐scale atmospheric circulation patterns predicted by general circulation models (GCMs). Correlation analyses between the flood‐affected area (FAA) for July–September and tropical sea‐surface temperature (SST) indicate connections to tropical Pacific and Indian Ocean SSTs, at a short lead time of a month or so. These are related to El Niño–southern oscillation (ENSO). Correlations between the SSTs of the preceding October–December and the July–September FAA are weaker but notable. Forecasts of the FAA using the leading principal components (PCs) of SST were made, which provided good skill with a lead time of a month or so. The streamflows and rainfall observed in Bangladesh have been added to these prediction models. Finally, the SST PCs were replaced with PCs of GCM prediction fields (precipitation). The prediction models at short lead time that were constructed for FAA were of generally similar levels of skill to that for SST. This is encouraging, as it suggests that linkages with SST can be successfully recovered in a physical model of the climate system in Bangladesh. This study concludes that seasonal flood prediction in Bangladesh is possible from the unusually warm or cold SST in parts of the tropics. This predictability can be enhanced with the information achievable from monitoring the downstream streamflows (which are generated mainly from upstream rainfall conditions) in advance of the flooding season. Finally, this study recommends formalizing a regional cooperation among the countries in the principal co‐basin areas of the Ganges–Brahmaputra–Meghna to achieve this goal. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
622.
John Krizmanic Brian Morgan Robert Streitmatter Neil Gehrels Keith Gendreau Zaven Arzoumanian Reza Ghodssi Gerry Skinner 《Experimental Astronomy》2005,20(1-3):299-306
Diffractive optics, such as Phase Fresnel Lenses (PFL's), offer the potential to achieve excellent imaging performance in the x-ray and gamma-ray photon regimes. In principle, the angular resolution obtained with these devices can be diffraction limited. Furthermore, improvements in signal sensitivity can be achieved as virtually the entire flux incident on a lens can be concentrated onto a small detector area. In order to verify experimentally the imaging performance, we have fabricated PFL's in silicon using gray-scale lithography to produce the required Fresnel profile. These devices are to be evaluated in the recently constructed 600-meter x-ray interferometry testbed at NASA/GSFC. Profile measurements of the Fresnel structures in fabricated PFL's have been performed and have been used to obtain initial characterization of the expected PFL imaging efficiencies. 相似文献
623.
624.
625.
626.
Simon Willcock Oliver L. Phillips Philip J. Platts Andrew Balmford Neil D. Burgess Jon C. Lovett Antje Ahrends Julian Bayliss Nike Doggart Kathryn Doody Eibleis Fanning Jonathan M. H. Green Jaclyn Hall Kim L. Howell Rob Marchant Andrew R. Marshall Boniface Mbilinyi Pantaleon K. T. Munishi Nisha Owen Ruth D. Swetnam Elmer J. Topp-Jorgensen Simon L. Lewis 《Carbon balance and management》2017,12(1):20
627.
628.
629.