全文获取类型
收费全文 | 16481篇 |
免费 | 2361篇 |
国内免费 | 3283篇 |
专业分类
测绘学 | 3377篇 |
大气科学 | 3171篇 |
地球物理 | 2619篇 |
地质学 | 6681篇 |
海洋学 | 1910篇 |
天文学 | 541篇 |
综合类 | 1347篇 |
自然地理 | 2479篇 |
出版年
2024年 | 69篇 |
2023年 | 228篇 |
2022年 | 404篇 |
2021年 | 517篇 |
2020年 | 555篇 |
2019年 | 667篇 |
2018年 | 458篇 |
2017年 | 621篇 |
2016年 | 597篇 |
2015年 | 716篇 |
2014年 | 869篇 |
2013年 | 910篇 |
2012年 | 976篇 |
2011年 | 1097篇 |
2010年 | 880篇 |
2009年 | 962篇 |
2008年 | 988篇 |
2007年 | 1184篇 |
2006年 | 1104篇 |
2005年 | 1082篇 |
2004年 | 973篇 |
2003年 | 843篇 |
2002年 | 840篇 |
2001年 | 655篇 |
2000年 | 634篇 |
1999年 | 520篇 |
1998年 | 515篇 |
1997年 | 422篇 |
1996年 | 371篇 |
1995年 | 314篇 |
1994年 | 302篇 |
1993年 | 218篇 |
1992年 | 162篇 |
1991年 | 124篇 |
1990年 | 90篇 |
1989年 | 92篇 |
1988年 | 59篇 |
1987年 | 45篇 |
1986年 | 26篇 |
1985年 | 14篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1954年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
The responses of a spar constrained by slack mooring lines to steep ocean waves and tensions in the mooring lines are simulated using two different numerical schemes: a quasi-static approach (SMACOS) and a coupled dynamic approach (COUPLE). The two approaches are the same in computing wave loads on the structure. Their difference is in modeling dynamic forces of mooring lines; that is the dynamic forces are included in the computation of COUPLE but neglected in SMACOS. The numerical simulation is examined against the laboratory measurements of the JIP Spar in a water depth of 318 m. The dynamic coupling effects between the JIP Spar and its mooring lines in different water depths (318, 618 and 1018 m) are investigated by the comparison of numerical simulations obtained using the quasi-static and coupled dynamic approaches. It is found that the damping of mooring lines reduces the slow-drift surge and pitch of the Spar, especially in deep water. The reduction in the amplitude of slow-drift surge can reach about 10% in a water depth of 1018 m. The tension in mooring lines may greatly increase in the wave frequency range when dynamic forces in mooring lines are considered. The mooring-line tension in the wave frequency range predicted by the coupled dynamic approach can be eight times as great as the corresponding prediction by the quasi-static approach in a water depth of 1018 m. This finding may have important implications for the estimation of the fatigue strength and life span of the mooring lines deployed in deep water oceans. 相似文献
73.
海底勘查技术的最新发展 总被引:4,自引:0,他引:4
本文将介绍用于探测海底三维地质特征的海底勘查的最新发展。它主要包括海底地形测绘技术,海底形貌观测技术、海底地层声学探测技术等。 相似文献
74.
75.
76.
浮体间距对多浮体系统水动力系数的影响 总被引:2,自引:1,他引:2
根据三维线性势流理论,采用格林函数法,对多浮体系统的水动力系数进行了数值分析。数值算例中给出了在固定波频下水动力系数与浮体间相对位置关系曲线。水动力系数的变化幅度随着浮体间距离增大而变小。随着浮体间距的变化,水动力系数极值的出现具有明显的规律,相邻的极大值(或极小值)的间距为半个波长或一个波长。 相似文献
77.
78.
采集设备采集数据发送到值班PC机,在无人干预的情况下接收处理软件自动对数据进行回放和进一步处理,为用户提供数据产品和服务,并提供一个界面,使用户能够了解系统的运行状况,获得相关数据和状态参数。 相似文献
79.
Roberto Montes-Iturrizaga Ernesto Heredia-Zavoni Francisco Silva-Gonzlez 《Applied Ocean Research》2007,29(4):239-241
The main aim of this work is to derive a correct formulation for the characteristic resistance of a mooring line segment with lognormally distributed component resistances and substitute an equation proposed by Vazquez-Hernandez et al. [Vazquez-Hernandez AO, Ellwanger GB, Sagrilo LVS. Reliability-based comparative study for mooring lines design criteria. Appl Ocean Res 2006; 28(6):398–406] in a paper published in this journal, which is not correct. The mooring line is considered as a series system and the resistances of individual components of a line segment are statistically independent and identically distributed; furthermore, the case of normally distributed component resistances is also discussed. A comparison with the corresponding equation proposed by DNV-OS-E301 is given. Results show that the formula proposed by Vazquez-Hernandez et al. [Vazquez-Hernandez AO, Ellwanger GB, Sagrilo LVS. Reliability-based comparative study for mooring lines design criteria. Appl Ocean Res 2006; 28(6):398–406] overestimates quite significantly the characteristic resistance of a mooring line segment. 相似文献
80.
In this paper, we focus on the status and trends of the current Korean fisheries management regime. Specifically, this paper briefly introduces the Korean conventional fisheries management regime (KCFMR) and discusses its problems and limitations. In describing policy evolution, this paper finds reasons why the Korean government has chosen a TAC system, an output control approach, besides input control approaches in force for almost a century. This paper also describes the evolution of the Korean TAC system, which is carrying out a pivotal role in Korean fisheries development, and analyzes problems of the Korean TAC system. Finally, this paper gives a perspective on expanding the Korean TAC system toward Output Control Systems (OCSs) such as Individual Quotas (IQs), Individual Vessel Quotas (IVQs), Individual Transferable Traps (ITTs), Community Quotas (CQs), and Individual Transferable Quotas (ITQs). 相似文献