全文获取类型
收费全文 | 1594篇 |
免费 | 494篇 |
国内免费 | 730篇 |
专业分类
测绘学 | 142篇 |
大气科学 | 272篇 |
地球物理 | 598篇 |
地质学 | 1276篇 |
海洋学 | 254篇 |
天文学 | 30篇 |
综合类 | 129篇 |
自然地理 | 117篇 |
出版年
2024年 | 9篇 |
2023年 | 32篇 |
2022年 | 60篇 |
2021年 | 69篇 |
2020年 | 86篇 |
2019年 | 117篇 |
2018年 | 106篇 |
2017年 | 85篇 |
2016年 | 84篇 |
2015年 | 109篇 |
2014年 | 123篇 |
2013年 | 134篇 |
2012年 | 143篇 |
2011年 | 149篇 |
2010年 | 126篇 |
2009年 | 137篇 |
2008年 | 131篇 |
2007年 | 157篇 |
2006年 | 147篇 |
2005年 | 124篇 |
2004年 | 123篇 |
2003年 | 88篇 |
2002年 | 68篇 |
2001年 | 50篇 |
2000年 | 56篇 |
1999年 | 47篇 |
1998年 | 39篇 |
1997年 | 54篇 |
1996年 | 39篇 |
1995年 | 26篇 |
1994年 | 20篇 |
1993年 | 18篇 |
1992年 | 8篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 10篇 |
1986年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1979年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有2818条查询结果,搜索用时 109 毫秒
11.
12.
Chen Guoping Yu Kuang-ming Zhang Jiachang Assistant Engineer River Harbour Department Nanjing Hydraulic Research Institute Nanjing
Prof. Senior Engineer River Harbour Department Nanjing Hydraulic Research Institute Nanjing
Senior Engineer River Harbour Department Nanjing Hydraulic Research Institute Nanjing 《中国海洋工程》1991,(4)
This paper discusses the effect of berm width and elevation of composite slope on irregular wave run-up. Based on the data obtained from model tests, the formula and distribution of irregular wave run-up on composite slope are derived. The changing of wind speed, width and elevation of the berm are considered comprehensively. The wave run-up with various exceedance probability can be es-timated utilizing the distribution curves of irregular wave run-up. 相似文献
13.
Instability analysis of three-dimensional ocean shear waves 总被引:1,自引:0,他引:1
Qiao Fangli 《海洋学报(英文版)》1996,15(1):1-8
Instabilityanalysisofthree-dimensionaloceanshearwaves¥QiaoFangli(ReceivedNovember6,1995,acceptedNovember30.1995)Abstract:Base... 相似文献
14.
For convenience of dynamic analysis, some offshore structures such as fixed-type platforms are often modeled as the wedge beams supporting tip lumped masses. It is well-known that, due to the effect of the surrounding water, the natural frequencies of a beam in air (or dry beam) are different from those of the same beam immersed in water (or wet beam). However, if the natural frequencies and the associated mode shapes of a dry beam are calculated by taking account of the “added mass” for the immersed beam, then the last natural frequencies and mode shapes will be equal to the corresponding ones of the wet beam. Based on the last concept, the closed form solutions for natural frequencies and the associated mode shapes of the dry beam were determined first, then the partial differential equation of motion for the wet beam was transformed into a matrix equation by using the expansion theorem and the foregoing closed form solutions of free vibration responses for the dry beam. Solving the last matrix equation will give the required natural frequencies and the associated mode shapes of the wet beam. The formulation of this paper is available for the fully or partially immersed double tapered beams with either circular, square or rectangular cross-sections. The taper ratio for width and that for depth may be equal or unequal. The numerical results of this paper were compared with the existing results or the finite-element-method results and good agreement was achieved. 相似文献
15.
In order to accurately design a sand compaction pile (SCP) with low replacement area ratio, it is important to understand the mechanical interaction between the sand pile and clay ground and its mechanism during consolidation process in composite ground. In this article, therefore, a series of numerical analyses on composite ground improved by SCP with low replacement area ratio were carried out. The applicability of numerical analyses, in which an elasto-viscoplastic consolidation finite element method was applied, were confirmed by comparing the results obtained from a series of laboratory model tests with the composite ground improved by SCP. Through the results of the numerical analyses, mechanical behavior of the sand pile and clay in composite ground during consolidation is elucidated, together with a stress sharing mechanism between sand pile and clay. 相似文献
16.
埕岛油田海区海底地形变化及预防措施 总被引:2,自引:2,他引:2
综合在胜利石油管理局埕岛油田海区多年来工程测绘与地质勘察资料 ,对埕岛油田海区地形地貌特征及其变化与发育趋势进行了论述 ,同时讨论了埕岛油田海上工程中需要重视的问题以及有关的工程防护问题。 相似文献
17.
18.
19.
20.
作者引入 I(L)值完全下半连续映射 ,研究其性质。利用 I(L)值完全下半连续映射定义I(L)值完全诱导空间 ,给出 I(L)值完全诱导空间的拓扑基的表达形式 ,证得两个 I(L)值完全诱导空间的映射是连续映射的充分必要条件 ,并建立了乘积空间的 I(L)值完全诱导空间与 I(L)值完全诱导空间的乘积空间的联系 相似文献