全文获取类型
收费全文 | 729篇 |
免费 | 165篇 |
国内免费 | 381篇 |
专业分类
测绘学 | 10篇 |
大气科学 | 545篇 |
地球物理 | 92篇 |
地质学 | 100篇 |
海洋学 | 446篇 |
天文学 | 1篇 |
综合类 | 26篇 |
自然地理 | 55篇 |
出版年
2024年 | 8篇 |
2023年 | 16篇 |
2022年 | 36篇 |
2021年 | 44篇 |
2020年 | 47篇 |
2019年 | 59篇 |
2018年 | 27篇 |
2017年 | 27篇 |
2016年 | 35篇 |
2015年 | 37篇 |
2014年 | 58篇 |
2013年 | 57篇 |
2012年 | 62篇 |
2011年 | 59篇 |
2010年 | 45篇 |
2009年 | 73篇 |
2008年 | 51篇 |
2007年 | 76篇 |
2006年 | 53篇 |
2005年 | 42篇 |
2004年 | 28篇 |
2003年 | 33篇 |
2002年 | 37篇 |
2001年 | 20篇 |
2000年 | 29篇 |
1999年 | 15篇 |
1998年 | 27篇 |
1997年 | 30篇 |
1996年 | 32篇 |
1995年 | 27篇 |
1994年 | 34篇 |
1993年 | 21篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1987年 | 3篇 |
1983年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有1275条查询结果,搜索用时 15 毫秒
91.
一次东亚寒潮爆发后冷涌发展的研究 总被引:10,自引:0,他引:10
分析了1981年1月21—28日一次东亚强寒潮爆发后南海和西太平洋地区冷涌的发展过程。冷涌的发展最先表现为低层强东北风沿东亚沿海地区和南海中北部的迅速建立。2—3d之后,又在菲律宾以东洋面激起第二次冷涌。与冷涌相伴随的低层温度场变化也十分明显,同样具有先后两次降温过程。冷涌期高空风场表现有明显的脉动,南海北部高空西风迅速减弱,而在南海近赤道地区出现了很强的高空东风区。冷涌的发展与寒潮冷高压的南下有密切关系,它的强度在很大程度上取决于中纬度冷高压的强度。另一方面,冷涌发展后,通过Hadley环流可影响中纬西风急流和热带东风急流的变化。 相似文献
92.
台风运动内在随机性的研究 总被引:4,自引:0,他引:4
本文用差分方法,对决定性的正压涡度方程实施了四组数值积分。根据模式输出量,求得了台风中心移速的一维序列和二维序列。计算了移速序列的关联维数和K熵。结果表明模式大气中台风中心的移动具有内在随机性。最后讨论了局域热源和基流对台风移动路径随机性和可预测性的影响。 相似文献
93.
94.
台风移动规律的研究 Ⅱ.小地形与边界层的动力作用 总被引:1,自引:1,他引:1
从支配台风中心移动的基本方程出发,着重分析了小地形(地形高度与台风系统的的垂直厚度相双为小量)的抬升作用和边界层的摩擦作用对台风移动影响的定性特征。结果表明,较高地势对台风有“吸收”作用;边界层摩擦辐合引起的艾克曼抽吸有利于台风产生沿局地流场引导速度方向的加速度。 相似文献
95.
台风影响期间珠江三角洲局地强风暴和大暴雨发生的环境条件 总被引:4,自引:0,他引:4
采用1976-1983年6-8月珠江三角洲地区受台风影响期间区内各站逐日的强风暴和降水资料以及广泛站的探空资料,用相关对比度分析方法,对台风环流中的珠江三角洲局地强风暴和大暴雨发生的环境条件进行统计诊断,得出台风影响珠江三角洲时这两种强天气发生的有利的环境条件,并发现二者在气压、风速、层结稳定度和中下层位势不稳定等方面显著不同。 相似文献
96.
从支配台风中心移动的基本方程出发,着重分析了小地形(地形高度与台风系统的垂直厚度相比为小量)的抬升作用和边界层的摩擦作用对台风移动影响的定性特征。结果表明,较高地势对台风有“吸引”作用;边界层摩擦辐合引起的艾克曼抽吸有利于台风产生沿局地流场引导速度方向的加速度。 相似文献
97.
Origin and stratigraphy of phreatomagmatic deposits at the Pleistocene Sinker Butte Volcano, Western Snake River Plain, Idaho 总被引:1,自引:3,他引:1
Brittany D. Brand Craig M. White 《Journal of Volcanology and Geothermal Research》2007,160(3-4):319-339
Sinker Butte is the erosional remnant of a very large basaltic tuff cone of middle Pleistocene age located at the southern edge of the western Snake River Plain. Phreatomagmatic tephras are exposed in complete sections up to 100 m thick in the walls of the Snake River Canyon, creating an unusual opportunity to study the deposits produced by this volcano through its entire sequence of explosive eruptions. The main objectives of the study were to determine the overall evolution of the Sinker Butte volcano while focusing particularly on the tephras produced by its phreatomagmatic eruptions. Toward this end, twenty-three detailed stratigraphic sections ranging from 20 to 100 m thick were examined and measured in canyon walls exposing tephras deposited around 180° of the circumference of the volcano.Three main rock units are recognized in canyon walls at Sinker Butte: a lower sequence composed of numerous thin basaltic lava flows, an intermediate sequence of phreatomagmatic tephras, and a capping sequence of welded basaltic spatter and more lava flows. We subdivide the phreatomagmatic deposits into two main parts, a series of reworked, mostly subaqueously deposited tephras and a more voluminous sequence of overlying subaerial surge and fall deposits. Most of the reworked deposits are gray in color and exhibit features such as channel scour and fill, planar-stratification, high and low angle cross-stratification, trough cross-stratification, and Bouma-turbidite sequences consistent with their being deposited in shallow standing water or in braided streams. The overlying subaerial deposits are commonly brown or orange in color due to palagonitization. They display a wide variety of bedding types and sedimentary structures consistent with deposition by base surges, wet to dry pyroclastic fall events, and water saturated debris flows.Proximal sections through the subaerial tephras exhibit large regressive cross-strata, planar bedding, and bomb sags suggesting deposition by wet base surges and tephra fallout. Medial and distal deposits consist of a thick sequence of well-bedded tephras; however, the cross-stratified base-surge deposits are thinner and interbedded within the fallout deposits. The average wavelength and amplitude of the cross strata continue to decrease with distance from the vent. These bedded surge and fall deposits grade upward into dominantly fall deposits containing 75–95% juvenile vesiculated clasts and localized layers of welded spatter, indicating a greatly reduced water-melt ratio. Overlying these “dryer” deposits are massive tuff breccias that were probably deposited as water saturated debris flows (lahars). The first appearance of rounded river gravels in these massive tuff breccias indicates downward coring of the diatreme and entrainment of country rock from lower in the stratigraphic section. The “wetter” nature of these deposits suggests a renewed source of external water. The massive deposits grade upward into wet fallout tephras and the phreatomagmatic sequence ends with a dry scoria fall deposit overlain by welded spatter and lava flows.Field observations and two new 40Ar–39Ar incremental heating dates suggest the succession of lavas and tephra deposits exposed in this part of the Snake River canyon may all have been erupted from a closely related complex of vents at Sinker Butte. We propose that initial eruptions of lava flows built a small shield edifice that dammed or disrupted the flow of the ancestral Snake River. The shift from effusive to explosive eruptions occurred when the surface water or rising ground water gained access to the vent. As the river cut a new channel around the lava dam, water levels dropped and the volcano returned to an effusive style of eruption. 相似文献
98.
海温变化对台风路径的影响 总被引:8,自引:2,他引:8
在台风模式中采用周平均海温和多年的月平均海温,对一些台风个例进行了比较,分析了数值模式中影响台风路径的海温因子变化对台风移动路径的影响。 相似文献
99.
应用NCEP/NCAR再分析资料,分析了9408号台风异常路径形成的可能原因。结果表明,环境引导流、准均匀流和偶极子流的共同作用对移向突变和移速突变有着重要影响。 相似文献
100.