全文获取类型
收费全文 | 4008篇 |
免费 | 1023篇 |
国内免费 | 1534篇 |
专业分类
测绘学 | 171篇 |
大气科学 | 2595篇 |
地球物理 | 754篇 |
地质学 | 607篇 |
海洋学 | 1234篇 |
天文学 | 263篇 |
综合类 | 179篇 |
自然地理 | 762篇 |
出版年
2024年 | 52篇 |
2023年 | 136篇 |
2022年 | 206篇 |
2021年 | 231篇 |
2020年 | 251篇 |
2019年 | 337篇 |
2018年 | 227篇 |
2017年 | 272篇 |
2016年 | 235篇 |
2015年 | 247篇 |
2014年 | 323篇 |
2013年 | 374篇 |
2012年 | 358篇 |
2011年 | 334篇 |
2010年 | 242篇 |
2009年 | 310篇 |
2008年 | 255篇 |
2007年 | 323篇 |
2006年 | 254篇 |
2005年 | 202篇 |
2004年 | 176篇 |
2003年 | 172篇 |
2002年 | 154篇 |
2001年 | 107篇 |
2000年 | 117篇 |
1999年 | 95篇 |
1998年 | 83篇 |
1997年 | 63篇 |
1996年 | 89篇 |
1995年 | 70篇 |
1994年 | 52篇 |
1993年 | 64篇 |
1992年 | 41篇 |
1991年 | 33篇 |
1990年 | 15篇 |
1989年 | 14篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1986年 | 4篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有6565条查询结果,搜索用时 296 毫秒
11.
12.
考虑到平台所在海区台风出现的频次及其诱发之风、浪、潮、流极端海况联合出现的概率特性,本文推导出Poisson—Logistic二元复合极值模式,并以平台甲板标高进行实例计算。新模式增加了概率模型的物理内涵,解决了Logistic模型阈值选取的任意性。对海洋工程极端海况荷载组合预测具有广泛的应用前景。 相似文献
13.
Weng Keqin
Associate Professor Hydraulic Hydro-Power Engineering Dept. Tsinghua University Beijing 《中国海洋工程》1995,(2)
This paper reveals that the long-period statistic distribution of the characteristic heights of deep-water waves assumes the lognormal distribution. Thereafter, the largest wave-height which may occur in the service life of coastal structures is derived in this paper. 相似文献
14.
本文探讨东海区近海强风预报模式,首先介绍建立预报模式的思路和步骤,及使用说明,为了验证强风预报模式和判别条件,用1986、1987上日本传真天气图进行试报,准确和基本准确度为91.1%,并给出了1989、1995年随船试验预报结果,准确和基本准确率为90%以上。 相似文献
15.
本文以南麂海洋站1983~1990年风、浪的实测资料为依据,建立了南麂海城春、夏、秋、冬季定常波风浪波高与风速的经验关系式。检验结果表明,曲线回归显著,计算值与实测值吻合良好。文中还对偏NNE向和偏SSW向计算波高随风速增大的快慢,同一方向在同一风速作用下计算波高的季节变化及其机理作了初浅的讨论。 相似文献
16.
17.
W.R. Geyer 《Estuarine, Coastal and Shelf Science》1997,44(6):713-722
Observations of two small estuaries in Cape Cod, U.S.A. indicate large variations in salinity structure that are forced by variations in along-estuary wind stress. During onshore winds, the estuarine circulation is reduced, and the along-estuary salinity gradient increases as freshwater accumulates. During offshore winds, the surface outflow is enhanced, freshwater is flushed out of the estuary, and the along-estuary salinity gradient becomes weak. Constrictions block the wind-induced flushing, resulting in strong salinity fronts across the constrictions. The residence time of one of the estuaries varies by more than a factor of three in response to variations in wind-induced flushing. The other estuary has little variation of flushing associated with winds, due to a constriction at the mouth that inhibits the wind-induced exchange. The strong influence of winds on the flushing of these estuaries is due in part to their shallow depths, which accentuates the influence of wind stress relative to the effects of the horizontal density gradient. In addition, the residence times of the estuaries are comparable to the time scale of wind forcing, allowing large changes in water properties during wind events. 相似文献
18.
渤海南部海域年极值波浪和设计波浪的特征研究 总被引:1,自引:0,他引:1
本文用统计计算和后报方法,获得了本海域不同海区多年年极值波高(H1/10)资料。用P-Ⅲ型和短期测波资料频率分析方法,估算了各海区的设计波高,并依据文献[3]计算出对应的平均周期。用Kolmogoroff适合度方法检验所得的结果表明,依P-Ⅲ型方法拟配的理论频率曲线与经验点十分吻合,从而确定了本海域不同海区最佳的设计波浪。分析本海域年极值波浪的基本特征表明,本海域除了渤海湾北部海区以外,主浪向一般为NNE向,渤海海峡区的年极值波高和设计波高均为最大,而向莱州湾及渤海湾沿岸海区逐渐减小;在沿岸海区,由龙口至黄河口一带的极值波高较大。 相似文献
19.
Oleg Zaytsev Rafael Cervantes-Duarte Orzo Montante Artemio Gallegos-Garcia 《Journal of Oceanography》2003,59(4):489-502
High primary productivity on the Pacific coast of the Baja California Peninsula is usually related to coastal upwelling activity
that injects nutrients into the euphotic zone in response to prevailing longshore winds (from the northwest to north). The
upwelling process has maximum intensity from April to June, with the coastal upwelling index varying from 50 to 300 m3/s per 100 m of coastline. Along the entire coast of the peninsula, the upwelling intensity changes in accordance with local
wind conditions and bottom topography. Spatial variability can also be modulated by the influence of mesoscale meanders of
the California Current. We have identified the seasonal and synoptic variability of upwelling signatures on the Baja California
shelf, using averaged monthly and weekly sea surface temperature (SST) distributions obtained from remote sensing imagery
from the Advanced Very High Resolution Radiometer in the period from 1996 to 2001. Analysis of SST distribution and direct
experimental data on temperature and nutrient concentration shows that the areas with the coldest SST anomalies were closely
related to the bottom slope, shelf width, and coastline orientation relating to wind direction. We also assume that the nutrient
transport into the coastal lagoons may be forced by the coupling of coastal upwelling and tidal pumping of surface waters
into the lagoon system.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
Decadal variability of subsurface temperature in the North Pacific has been investigated. Two dominant regions were found;
the central subarctic region (CSa) and the north-eastern subtropical region (NESt). In CSa, cooling (warming) of wintertime
subsurface temperature corresponds to the large (small) temperature gradient and southward (northward) shift of subsurface
temperature front, associated with the increase (decrease) of positive wind stress curl and the southward (northward) shift
of curl τ zero line with 2 years delay. It is suggested that the relocation of subtropical-subarctic boundary plays an important
role. In NESt, importance of heat flux through the sea surface and heat divergence in the Ekman layer is also discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献