全文获取类型
收费全文 | 1179篇 |
免费 | 467篇 |
国内免费 | 1048篇 |
专业分类
测绘学 | 24篇 |
大气科学 | 1793篇 |
地球物理 | 107篇 |
地质学 | 89篇 |
海洋学 | 544篇 |
天文学 | 6篇 |
综合类 | 63篇 |
自然地理 | 68篇 |
出版年
2024年 | 16篇 |
2023年 | 48篇 |
2022年 | 97篇 |
2021年 | 94篇 |
2020年 | 118篇 |
2019年 | 147篇 |
2018年 | 82篇 |
2017年 | 90篇 |
2016年 | 60篇 |
2015年 | 105篇 |
2014年 | 139篇 |
2013年 | 137篇 |
2012年 | 140篇 |
2011年 | 143篇 |
2010年 | 105篇 |
2009年 | 137篇 |
2008年 | 118篇 |
2007年 | 148篇 |
2006年 | 117篇 |
2005年 | 90篇 |
2004年 | 79篇 |
2003年 | 65篇 |
2002年 | 57篇 |
2001年 | 52篇 |
2000年 | 25篇 |
1999年 | 28篇 |
1998年 | 38篇 |
1997年 | 38篇 |
1996年 | 33篇 |
1995年 | 47篇 |
1994年 | 35篇 |
1993年 | 15篇 |
1992年 | 18篇 |
1991年 | 14篇 |
1990年 | 3篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 2篇 |
排序方式: 共有2694条查询结果,搜索用时 31 毫秒
41.
42.
大气对流边界层中的涡漩结构 总被引:4,自引:1,他引:4
大气边界层中存在尺度从几百米到几十公里的大涡漩运动。它们在边界层中动量、热量、水汽等垂直输送中起重要作用。作者从边界层中对流和上部稳定层中波动相互作用的观点,发展得出大涡结构的对流波动理论。根据此理论,大涡的波谱构成主要由上、下层大气中风向、风速、层结以及两层之间的温度跃变等因素决定。本文根据卫星云图和天气资料分析了一次冷空气爆发流经暖洋面上形成云街、对流单体以及它们之间的相互演化的过程,并用对流波动理论,依据各阶段的大气条件计算出它们的波数构成,并得出了垂直速度、辐合带、界面扰动的分布,解释了云街、对流单体的形成、结构及相互转化的原因 相似文献
43.
44.
45.
46.
47.
Two semi-asymmetric flow patterns of typhoons are chosen to qualitatively determine the effect of exchange of horizontal momentum between inflow and outflow layers and the environment on the motion of typhoons. The results show that only the asymmetric flow component (residual after azimuthal mean flow has been removed) could cause a net momentum input into or output from a typhoon and therefore contribute to the changes in speed and direction of the typhoon movement. A typhoon with major inflow and/or outflow channels on its right (left) side would tend to accelerate and turn left (decelerate and turn right); On the other hand, a typhoon with major inflow and/or outflow channels in the rear (front) semicircle would tend to accelerate and turn right (decelerate and turn left). 相似文献
48.
This paper designs three quasi-geostrophic barotropic models with a radial/horizontal grid length being 2 kin,one in the polar coordinates,one on a stationary typhoon circulation condition and another on a non-stationary typhoon circulation condition in the Cartesian coordinates,to investigate the effects of azimuthal and radial linear advections,and nonlinear advection on the inward propagation of mesoscale vorticity and the changes of typhoon intensity.Results show that the azimuthal linear advection may result in the formation of spiral vorticity bands;the radial linear advection in a certain parameter set is able to transfer vorticity inwards,leading to a slight enhancement of typhoon;the nonlinear advection of perturbation vorticity on a stationary typhoon circulation condition may transfer more vorticities inwards,thus resulting in a distinct enhancement of typhoon;and the nonlinear advection on a non-stationary typhoon circulation condition possesses duality,i.e.on the one hand,the advection increases the vorticity of inward propagation,thus favorable to the intensification of typhoon,and on the other hand,in the inward propagation process of vorticity the originally concentric and axisymmetric structure of typhoon basic flow is damaged,and a complex flow pattern forms,which in turn tends to weaken the circulation of typhoon.At last the paper discusses the possible applications of those results in typhoon intensity prediction. 相似文献
49.
As a result of the left-lateral strike-slipping of the Altyn Tagh fault in Neotectonic period, a contra-rotational structure, namely the Zhaobishan vortex structure, has developed at the juncture of the main Altyn Tagh fault and the northern fringe fault of the Qilian Mountains.Preliminary analysis on the deformation and evolution of the Zhaobishan vortex structure. In combination with the previous data, suggests that the tectonic transform between the Altyn Tagh fault and the northern fringe fault of the Qilian Mountains attributes to the deformation of the rotational structure. The existence of a series of rotational structures along the Altyn Tagh fault and on the northeastern edge of the Qinghai-Xizang(Tibet) plateau indicate that as the substance in the northern Qinghal-Xizang (Tibet) plateau moves clockwise around the eastern tectonic knot of the Himalayas, rotational structures become the principal mode on the northern marginal zone of the Plateau of transforming and absorbing tectonic deformation. 相似文献
50.
一次强风暴的垂直环境特征数值模拟分析 总被引:4,自引:2,他引:4
应用MM 5模式对东北冷涡诱发的 2 0 0 2年 7月 1 2日强风暴进行了数值模拟 ,较成功地模拟出中尺度强对流风暴。发现冷涡后部中层干冷空气绝热下沉是东北冷涡 70 0hPa附近干暖盖形成和维持的重要机制 ,而低层暖湿气流爬升及干暖盖的抑制作用是东北冷涡强对流不稳定能量积累的重要机制。风暴发生前持续的低层西南风到中层西北风的风垂直切变产生的差动平流 ,加剧了层结不稳定 ,而风暴临近风垂直切变方向的快速逆转使热成风不平衡 ,必须通过激发垂直环流以适应其变化 ,对风暴发展有重要作用。 相似文献