全文获取类型
收费全文 | 2404篇 |
免费 | 494篇 |
国内免费 | 785篇 |
专业分类
测绘学 | 258篇 |
大气科学 | 619篇 |
地球物理 | 657篇 |
地质学 | 1068篇 |
海洋学 | 620篇 |
天文学 | 9篇 |
综合类 | 263篇 |
自然地理 | 189篇 |
出版年
2024年 | 12篇 |
2023年 | 36篇 |
2022年 | 72篇 |
2021年 | 100篇 |
2020年 | 114篇 |
2019年 | 142篇 |
2018年 | 111篇 |
2017年 | 135篇 |
2016年 | 123篇 |
2015年 | 140篇 |
2014年 | 157篇 |
2013年 | 196篇 |
2012年 | 169篇 |
2011年 | 172篇 |
2010年 | 150篇 |
2009年 | 190篇 |
2008年 | 149篇 |
2007年 | 203篇 |
2006年 | 135篇 |
2005年 | 136篇 |
2004年 | 132篇 |
2003年 | 109篇 |
2002年 | 94篇 |
2001年 | 98篇 |
2000年 | 91篇 |
1999年 | 69篇 |
1998年 | 62篇 |
1997年 | 58篇 |
1996年 | 55篇 |
1995年 | 49篇 |
1994年 | 46篇 |
1993年 | 42篇 |
1992年 | 36篇 |
1991年 | 21篇 |
1990年 | 17篇 |
1989年 | 18篇 |
1988年 | 14篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有3683条查询结果,搜索用时 18 毫秒
31.
Li Yucheng Wang Fenglong Professor Dalian University of Technology Dalian Senior Engineer Dalian University of Technology Dalian 《中国海洋工程》1993,(1)
- The wave-current forces on vertical piles in side-by-side arrangement induced by irregular waves with opposing current are investigated experimentally in this paper. The characteristics in both time and frequency domain of in-line, lift and resultant forces are analyzed. The grouping effect coefficients of inline, lift and resultant forces on piles related to KC number and relative spacing parameters are given. These results are compared with those in the case of irregular waves combined with following currents. It is found that the results in these two cases are quite different. The range of KC number tested is 10- 60, the range of Reynolds number is (0.55-3.43) ×104. 相似文献
32.
Vertical variations of wave-induced radiation stress tensor 总被引:3,自引:0,他引:3
INTRODUcrIONThe concept of radiation stress was deve1oPed by tonguet--Higgins and Stewart (1964 ),who intreduced the definition of radiation stress as the excess mornentum due to the presence ofwaves, on the basis of time-averaged laws of Newtonian fluid mechanics and the assmption ofa unifOrm velocity distribution over depth. Subequently, the theory has been applied success-fully in the investigation of phenomena such as wave set-up and set--down (Bowen et al.,l968), longshore currents … 相似文献
33.
采用TOGA/COARE国际合作考察期间(1992年10月─1993年2月)获得的267次定点(2°S,155°E)定时高空大气探测资料,进行计算分析,发现1992年12月─1993年2月低空存在一支西风急流,有两次分别持续半月之久,而1992年11月的两次赤道西风急流,因无赤道高空急流配合,仅持续2d便消失。本文还指出:(1)赤道低空西风急流是各种海-气指数产生ENSO异常的重要信息;(2)赤道高空急流有滞后赤道低空急流2d左右的响应关系;(3)赤道低空急流是纬向水汽输送的狭窄通道。 相似文献
34.
本文对北部湾三维潮波进行了数值研究,并将所得结果与现有观测资料作了比较。通过比较发现两者相当一致。文中还绘制了M_2和K_1分潮的同潮图,并对其作了讨论。可以断定,北部湾的日潮优势是由日潮共振所引起的。M_2和K_1分潮流的水平分布表明,强流区位于它们各自的蜕化无潮点附近。还讨论了分潮流的铅直结构,可以看出这种结构十分接近实际分潮流场的特征。 相似文献
35.
36.
37.
Chen Tieyun Zhu Zhenghong
Professor Dept. of Naval Architecture Ocean Engineering Shanghai Jiao Tong University Shanghai Lecturer 《中国海洋工程》1991,(1)
The plastic node method is reformulated by the variational principle and is applied to elasto-plastic finite element analysis of tubular joints, eventually including the effect of internal and external gussets, stiffener rings, etc., if necessary. Four different joints are studied here in detail for the elasto-plastic behavior, the strain at the hot spot, the strain concentration factor around the intersection line, and the propagation of the plastic region with loading up to collapse in order to determine the ultimate strength, safety factor, and development of the plastic field. The present results are in good agreement with the experimental results. 相似文献
38.
Domenico Voltolina Leslie N. Brown Maurice G. Robinson 《Estuarine, Coastal and Shelf Science》1985,21(6):817-822
The results of eight sets of repeated observations on the vertical variations of the chlorophyll maximum layer in a shallow lagoon during a red tide show that these were more frequently hydrologically induced, rather than due to active vertical migrations of the red tide-forming organism. These results are discussed and compared to those existing in the literature, with special regard to the role of light and nitrogen in conditioning vertical migrations in red tide-forming dinoflagellates. 相似文献
39.
Zooplankton diel vertical migration is evident on the mixed isothermal side of the western Irish Sea frontal system but is often influenced by large tides and persistent geostrophic currents. On the stratified side of the front, temperature acts as a controlling factor with most of the zooplankton occurring above the thermocline and carrying out pronounced vertical migration when chlorophyll a levels are low and diffuse. At higher chlorophyll levels, when discrete chlorophyll a maxima form, zooplankton vertical movement may be greatly modified with a large number of species and stages concentrating within these maxima at all times of the diel light cycle. 相似文献
40.