全文获取类型
| 收费全文 | 330篇 |
| 免费 | 76篇 |
| 国内免费 | 39篇 |
专业分类
| 测绘学 | 41篇 |
| 大气科学 | 72篇 |
| 地球物理 | 162篇 |
| 地质学 | 104篇 |
| 海洋学 | 29篇 |
| 天文学 | 2篇 |
| 综合类 | 17篇 |
| 自然地理 | 18篇 |
出版年
| 2022年 | 4篇 |
| 2021年 | 6篇 |
| 2020年 | 9篇 |
| 2019年 | 7篇 |
| 2018年 | 17篇 |
| 2017年 | 12篇 |
| 2016年 | 8篇 |
| 2015年 | 10篇 |
| 2014年 | 24篇 |
| 2013年 | 24篇 |
| 2012年 | 19篇 |
| 2011年 | 26篇 |
| 2010年 | 17篇 |
| 2009年 | 18篇 |
| 2008年 | 33篇 |
| 2007年 | 25篇 |
| 2006年 | 24篇 |
| 2005年 | 22篇 |
| 2004年 | 17篇 |
| 2003年 | 11篇 |
| 2002年 | 14篇 |
| 2001年 | 18篇 |
| 2000年 | 21篇 |
| 1999年 | 9篇 |
| 1998年 | 11篇 |
| 1997年 | 6篇 |
| 1996年 | 8篇 |
| 1995年 | 6篇 |
| 1994年 | 2篇 |
| 1993年 | 3篇 |
| 1992年 | 4篇 |
| 1991年 | 2篇 |
| 1990年 | 2篇 |
| 1989年 | 2篇 |
| 1988年 | 1篇 |
| 1983年 | 1篇 |
| 1954年 | 2篇 |
排序方式： 共有445条查询结果，搜索用时 15 毫秒
1.
An analysis of the kinetic energy budget during a case of interaction between middle latitude and extratropical cyclones has been made in this work. Horizontal flux convergence constitutes a major energy sink. Generation of kinetic energy via cross-contour flow is a persistent source throughout the growth and decay periods. Dissipation of kinetic energy from subgrid to grid scales is an important source during the pre-storm period; it acts as a sink during the growth and decay periods. The major contribution to kinetic energy comes from a persistent upper tropospheric jet stream activity throughout the period of the cyclone development. The characteristics of moisture-flux components (divergent and rotational) along with precipitable water content for different tropospheric layers throughout the life cycle of our cyclone are also studied in this work. It is found that most of required humidity for our cyclone are initiated from Arabian Sea and then to some extent are reinforced over Gulf of Aden and east of central Africa and then by passing over Red sea enter to the south and south east of Mediterranean Sea. The rotational component of the moisture transport brings moisture from two regions; the first which is considered the main region is the Indian Ocean, Arabian Sea, Gulf of Aden and north east of Sudan. The second source region is the Atlantic and Mediterranean Sea. In the middle troposphere, the primary moisture source is found over central Africa, which in turn is traced to the Atlantic Ocean, the Indian Ocean, and the Arabian Sea. The upper-level moisture fluxes are weak and play a minor role over the area of interaction between two cyclones. 相似文献
2.
3.
本人在借鉴前人成果并结合施工经验的基础上,系统总结了砂卵石地层与非开挖钻进施工的适应性,对非开挖钻进施工中出现的问题进行了归纳和分类,并对其原因进行了分析和探讨。同时,为了解决非开挖导向钻进在复杂地层特别是砂卵石层中的施工难题,考虑采用注浆预加固技术对砂卵石层进行预先加固,以提高其强度,保证非开挖导向钻进的顺利进行。更进一步地,对水平孔中注浆预加固的三种方法（垂直注浆法、导管注浆法、随钻注浆法）在导向钻进工程中的概念、适用范围、优缺点以及实施控制要点等进行了对比和研究。 相似文献
4.
5.
6.
7.
8.
9.
Wave interaction with a perforated wall breakwater with a submerged horizontal porous plate 总被引：1，自引：0，他引：1
This study examines the hydrodynamic performance of a new perforated-wall breakwater. The breakwater consists of a perforated front wall, a solid back wall and a submerged horizontal porous plate installed between them. The horizontal porous plate enhances the stability and wave-absorbing capacity of the structure. An analytical solution based on linear potential theory is developed for the interaction of water waves with the new proposed breakwater. According to the division of the structure, the whole fluid domain is divided into three sub-domains, and the velocity potential in each domain is obtained using the matched eigenfunction method. Then the reflection coefficient and the wave forces and moments on the perforated front wall and the submerged horizontal porous plate are calculated. The numerical results obtained for limiting cases are exactly the same as previous predictions for a perforated-wall breakwater with a submerged horizontal solid plate [Yip, T.L., Chwang, A.T., 2000. Perforated wall breakwater with internal horiontal plate. Journal of Engineering Mechanics ASCE 126 (5), 533–538] and a vertical wall with a submerged horizontal porous plate [Wu, J.H., Wan, Z.P., Fang, Y., 1998. Wave reflection by a vertical wall with a horizontal submerged porous plate. Ocean Engineering 25 (9), 767–779]. Numerical results show that with suitable geometric porosity of the front wall and horizontal plate, the reflection coefficient will be always rather small if the relative wave absorbing chamber width (distance between the front and back walls versus incident wavelength) exceeds a certain small value. In addition, the wave force and moment on the horizontal plate decrease significantly with the increase of the plate porosity. 相似文献
10.
Peng-fei Xie Lin Yang Qian-yong Liang Xu-hui Zhang Liang-hua Zhang Bin Zhang Xiao-bing Lu Hui-ce He Xue-min Wu Yi-fei Dong 《China Geology》2022,5(2):300-309
Natural gas hydrates (NGHs) are a new type of clean energy with great development potential. However, it is urgent to achieve safe and economical NGHs development and utilization. This study established a physical model of the study area using the FLAC3D software based on the key parameters of the NGHs production test area in the South China Sea, including the depressurization method, and mechanical parameters of strata, NGHs occurrence characteristics, and the technological characteristics of horizontal wells. Moreover, this study explored the law of influences of the NGHs dissociation range on the stability of the overburden strata and the casing structure of a horizontal well. The results are as follows. With the dissociation of NGHs, the overburden strata of the NGHs dissociation zone subsided and formed funnel-shaped zones and then gradually stabilized. However, the upper interface of the NGHs dissociation zone showed significant redistribution and discontinuity of stress. Specifically, distinct stress concentration and corresponding large deformation occurred in the build-up section of the horizontal well, which was thus prone to suffering shear failure. Moreover, apparent end effects occurred at the end of the horizontal well section and might cause the deformation and failure of the casing structure. Therefore, it is necessary to take measures in the build-up section and at the end of the horizontal section of the horizontal well to prevent damage and ensure the wellbore safety in the long-term NGHs exploitation.©2022 China Geology Editorial Office. 相似文献