全文获取类型
收费全文 | 4281篇 |
免费 | 840篇 |
国内免费 | 1229篇 |
专业分类
测绘学 | 577篇 |
大气科学 | 870篇 |
地球物理 | 851篇 |
地质学 | 2348篇 |
海洋学 | 826篇 |
天文学 | 118篇 |
综合类 | 313篇 |
自然地理 | 447篇 |
出版年
2024年 | 19篇 |
2023年 | 48篇 |
2022年 | 172篇 |
2021年 | 213篇 |
2020年 | 168篇 |
2019年 | 215篇 |
2018年 | 212篇 |
2017年 | 180篇 |
2016年 | 227篇 |
2015年 | 227篇 |
2014年 | 270篇 |
2013年 | 291篇 |
2012年 | 306篇 |
2011年 | 300篇 |
2010年 | 305篇 |
2009年 | 316篇 |
2008年 | 280篇 |
2007年 | 274篇 |
2006年 | 268篇 |
2005年 | 225篇 |
2004年 | 179篇 |
2003年 | 175篇 |
2002年 | 200篇 |
2001年 | 175篇 |
2000年 | 126篇 |
1999年 | 145篇 |
1998年 | 96篇 |
1997年 | 104篇 |
1996年 | 71篇 |
1995年 | 82篇 |
1994年 | 76篇 |
1993年 | 59篇 |
1992年 | 54篇 |
1991年 | 49篇 |
1990年 | 37篇 |
1989年 | 31篇 |
1988年 | 16篇 |
1987年 | 15篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 14篇 |
1981年 | 6篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1966年 | 6篇 |
1965年 | 16篇 |
1955年 | 4篇 |
1949年 | 5篇 |
1933年 | 7篇 |
排序方式: 共有6350条查询结果,搜索用时 46 毫秒
21.
Qiu Dahong Zang Jun Jia Ying
Academician of the Chinese Academy of Sciences Professor the State Key Laboratory of Coastal Offshore Engineering 《中国海洋工程》1996,(2)
Based on the 2nd order cnoidal wave theory, the characters of shallow water standing waves and their action on vertical walls are studied in this paper. The theoretical expressions of the wave surface elevation in front of and the wave pressure on the vertical wall are obtained. In order to verify the theoretical results, model tests were made in the State Key Laboratory of Coastal and Offshore Engineering at DUT. For the wave surface elevation in front of the wall and the wave forces on the wall at the moment when the wave surface at the wall surface goes down to the bottom of the wave trough, the calculated results coincide quite well with the experimental results. For the wave forces on the wall at the moment when the wave surface at the wall surface goes up to the top of the wave crest, the theoretical expressions are modified by the experimental results. For the convenience of practical use, calculations are made for the wave conditions which usually occur in enginering practice by use of the inves 相似文献
22.
Gao Yinli Yan Shuwang Wang Jinying
Graduate Student Tianjin University Tianjin
Professor Tianjin University Tianjin
Senior Engineer China Offshore Oil Engineering Co. 《中国海洋工程》1995,(1)
This paper introduces a stability design system of submarine pipelines. The system can provide a reasonable design procedure for users with reference to domestic and foreign methods and in the light of home engineering experience. 相似文献
23.
24.
Cao Guoao Shen Yilei
Dr.Professor Tongji University Shanghai
Shanghai College of Architectural Municipal Engineering Shanghai 《中国海洋工程》1991,(1)
In this paper, the responses of the interaction system of R.C. gravity single-leg platform to seismic excitation are mainly analysed. A set of nonlinear equations for the interaction system are established by using the wave, one is the soil-structure interaction and the other is the fluid-structure interaction. The seismic response of the interaction system is analysed for the influence of the asymmetric structure, fluid action, etc. with the input of seismic SH waves in any direction. The numerical results are given for a simple example. 相似文献
25.
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
26.
27.
摄食水平和性别对稀有鮈鲫生长和能量收支的影响 总被引:7,自引:0,他引:7
于1995年10月采集本所自繁有ju鲫(约1.03g/ind),在30℃水温下进行摄食-生长实验,研究了从饥饿到饱食5个摄食水平对不同性别稀有ju鲫的生长和能量收支的影响,结果表明,鱼体干物和能量含量不受摄食率和性别的影响,随着摄食率的增加,雌鱼的湿重,干重和能量特定生长率均呈双对数增加,雄鱼湿重特定生长率呈双对数增加,而干物质和能量特定生长率呈指增加,雄鱼生长速度及摄食率低于雌鱼,随着摄食率的增加,食物能损失于粪便中的比例均呈上升趋势,损失于排泄物中的比例变化不大,呈下降趋势,用于代谢的比例呈下降趋势,用于生长的比例呈上升趋势,除饥饿组外,在各个摄食水平,雌鱼食物能用于代谢的比例较雄鱼低,而用于生长的比例较雄鱼高。 相似文献
28.
In this paper, a new definition of structure system redundancy is proposed in view of the various measures for structure redundancy. By introducing the terms of structure system failure at the mechanism level and equivalent reliability index, the safety for existing offshore platforms can be evaluated by the semi-probabilistic method presented in this paper. Some numerical examples are given and satisfactory results have been obtained. 相似文献
29.
Nicholas Dodd 《中国海洋工程》1995,(2)
A nonlinear short-wave-averaged (surf beat) model is presented. The model is based on that of Roelvink (1993), but the numerical techniques used in the solution are based on the so-called weighted-averaged flux (WAF) method (eg Watson et al., 1992), with time-operator splitting used for the treatment of some of the source terms. This method allows a small number of computational points to be used, and is particularly efficient in modelling breaking long waves. The short-wave (or primary-wave) energy equation is solved using a more traditional Lax-Wendroff technique. Results of validation indicate that the model performs satisfactorily in most respects. 相似文献
30.
You Yage
YuZhi Associated Professor Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Guangzhou
. Professor Guangzhou Institute of Energy Conversion Chinese Academy of Sciences Guangzhou 《中国海洋工程》1995,(4)
In this paper, the extreme wave loads on an on-shore wave power device are investigated. First, boundary element method is applied to solve the three dimensional potential problem based on the small amplitude wave assumption. Then the motion of the Oscillating Water Column (OWC) inside the device and its laods on the device are calculated in time domain. Several protective techniques often applied are simulated by changing the constraint of the upper end of the chamber of the device. Numerical results are used to judge the effectiveness of these techniques. The investigation shows that damping can not effectively restrain the motion of OWC when the period of incident wave is long, which may cause dangerous loads on the structure. The shut chamber can effectively restrain the motion of OWC, but alternatively cause high pressure in the chamber. A Contracting opening with a Taper (CT) can exhaust a great amount of kinetic energy of OWC, and significantly decrease the loads. It is a promising protective tec 相似文献