全文获取类型
收费全文 | 1133篇 |
免费 | 274篇 |
国内免费 | 351篇 |
专业分类
测绘学 | 161篇 |
大气科学 | 252篇 |
地球物理 | 307篇 |
地质学 | 675篇 |
海洋学 | 190篇 |
天文学 | 11篇 |
综合类 | 51篇 |
自然地理 | 111篇 |
出版年
2024年 | 8篇 |
2023年 | 49篇 |
2022年 | 45篇 |
2021年 | 50篇 |
2020年 | 39篇 |
2019年 | 71篇 |
2018年 | 46篇 |
2017年 | 33篇 |
2016年 | 43篇 |
2015年 | 47篇 |
2014年 | 56篇 |
2013年 | 53篇 |
2012年 | 56篇 |
2011年 | 67篇 |
2010年 | 63篇 |
2009年 | 64篇 |
2008年 | 68篇 |
2007年 | 71篇 |
2006年 | 75篇 |
2005年 | 67篇 |
2004年 | 62篇 |
2003年 | 44篇 |
2002年 | 37篇 |
2001年 | 32篇 |
2000年 | 41篇 |
1999年 | 37篇 |
1998年 | 37篇 |
1997年 | 43篇 |
1996年 | 46篇 |
1995年 | 42篇 |
1994年 | 35篇 |
1993年 | 32篇 |
1992年 | 34篇 |
1991年 | 32篇 |
1990年 | 21篇 |
1989年 | 18篇 |
1988年 | 7篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1963年 | 2篇 |
1960年 | 4篇 |
1959年 | 5篇 |
1958年 | 1篇 |
1956年 | 1篇 |
1955年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有1758条查询结果,搜索用时 265 毫秒
81.
This paper comprehensively analyzes the characteristics and cause of the inshore intensification of super typhoon "Hato", the 13 th super typhoon in 2017. The aspects of typhoon structure, evolution of large-scale circulation and physical quantity field are analyzed using observation data from the Guangdong Automatic Station, Shenzhen Doppler Radar data, NCEP 1°×1° reanalysis data, NCEP 0.25°×0.25° sea surface temperature(SST) data, etc.Additionally, in order to investigate the influence of SST change on the intensity of "Hato", the WRF model and ECMWF 0.125°×0.125° reanalysis data are combined to conduct 3 sensitivity tests on"Hato". The results show that the favorable conditions for inshore intensification of "Hato"included the strengthening and westward extension of the subtropical high, continuous increase of low level moisture transport, an anomalous warm SST area north of 20°N in the South China Sea, an extreme divergence value in the northern South China Sea exceeding 6 ×10-5 s-1, and vertical environmental wind shear between 1.1 m/s-4.8 m/s. The intensity of"Hato"was very sensitive to changes in SST. When the SST rose or dropped by 2℃, the minimum central pressure of the typhoon changed by about 13 hPa or 11 hPa,respectively. SST indirectly influenced the intensity of the typhoon through affecting latent heat transport and sensible heat transport. 相似文献
82.
An ensemble Kalman filter based on the Weather Research and Forecasting Model (WRF-EnKF) is used to explore the effectiveness of the assimilation of surface observation data in an extreme local rainstorm over the Pearl River Delta region on 7 May 2017. Before the occurrence of rainstorm, the signals of weather forecasts in this case are too weak to be predicted by numerical weather model, but the surface temperature over the urban area are high. The results of this study show that the wind field, temperature, and water vapor are obviously adjusted by assimilating surface data of 10-m wind, 2-m temperature, and 2-m water vapor mixing ratio at 2300 BST 6 May, especially below the height of 2 km. The southerly wind over the Pearl River Delta region is enhanced, and the convergence of wind over the northern Guangzhou city is also enhanced. Additionally, temperature, water vapor mixing ratio and pseudoequivalent potential temperature are obviously increased over the urban region, providing favorable conditions for the occurrence of heavy precipitation. After assimilation, the predictions of 12-h rainfall amount, temperature, and relative humidity are significantly improved, and the rainfall intensity and distribution in this case can be successfully reproduced. Moreover, sensitivity tests suggest that the assimilation of 2-m temperature is the key to predict this extreme rainfall and just assimilating data of surface wind or water vapor is not workable, implying that urban heat island effect may be an important factor in this extreme rainstorm. 相似文献
83.
84.
85.
对徐海—石头岗花岗闪长岩体围岩中黑云母及有机质变质程度的研究发现:距岩体580m范围内的接触带岩石皆具有角岩化现象。黑云母含量受原岩成分影响,其鳞片粒径与岩体距离密切有关。围岩中镜质组反射率,(R_(mas))值与岩体距离之间有十分明显的规律。 相似文献
86.
87.
88.
89.
90.
颗粒运动及其数理简析 总被引:6,自引:7,他引:6
根据大量的野外观测和沙(雪)颗粒运动动态摄影的资料,分析地球表面上气流带动的各种固体颗粒的主要运动形式——振动、滚动、滑移、跃移和悬移的物理图象中力的作用,给出其主要运动参数的表达式,建立各自简单的数学模型。特别对跃移运动还给出模拟轨迹方程。该模型与实际拍摄的轨迹相对比表明,较之以前风沙物理研究者模拟的跃移轨迹要好。文中首次提出的滑移概念,即振动、滚动和滑移三种颗粒运动形式代替以往分类的蠕移、跃移和悬移运动形式更准确和清晰。文中还明确回答了第一颗砂粒是怎样起跳的这一关键问题。 相似文献