全文获取类型
收费全文 | 2875篇 |
免费 | 727篇 |
国内免费 | 1378篇 |
专业分类
测绘学 | 147篇 |
大气科学 | 31篇 |
地球物理 | 938篇 |
地质学 | 3120篇 |
海洋学 | 422篇 |
天文学 | 32篇 |
综合类 | 125篇 |
自然地理 | 165篇 |
出版年
2024年 | 5篇 |
2023年 | 32篇 |
2022年 | 74篇 |
2021年 | 83篇 |
2020年 | 121篇 |
2019年 | 153篇 |
2018年 | 146篇 |
2017年 | 97篇 |
2016年 | 175篇 |
2015年 | 190篇 |
2014年 | 220篇 |
2013年 | 210篇 |
2012年 | 228篇 |
2011年 | 274篇 |
2010年 | 252篇 |
2009年 | 281篇 |
2008年 | 232篇 |
2007年 | 254篇 |
2006年 | 300篇 |
2005年 | 245篇 |
2004年 | 235篇 |
2003年 | 179篇 |
2002年 | 157篇 |
2001年 | 114篇 |
2000年 | 145篇 |
1999年 | 117篇 |
1998年 | 91篇 |
1997年 | 82篇 |
1996年 | 61篇 |
1995年 | 39篇 |
1994年 | 58篇 |
1993年 | 29篇 |
1992年 | 16篇 |
1991年 | 22篇 |
1990年 | 14篇 |
1989年 | 19篇 |
1988年 | 10篇 |
1987年 | 13篇 |
1986年 | 6篇 |
1954年 | 1篇 |
排序方式: 共有4980条查询结果,搜索用时 148 毫秒
21.
Behavior of Pile Groups under Lateral Load 总被引:2,自引:0,他引:2
Yang Keji Li Qixin Wang Fuyuan
Associate Proferssor Hehai University Nanjing Engineer Hehai University Nanjing 《中国海洋工程》1991,(2)
Based on investigation and model tests, and in combination with the research work on group effect for pile groups under lateral loads relating to the code of fixed offshore platforms, a series of studies have been performed on the behavior and failure mechanism of laterally loaded pile groups, critical pile spacing inducing group effect, lateral bearing capacity of pile groups and its main influence factors, the stress-strain relationship for single piles and pile groups and so on. Some new laws about non-uniformity of load distribution in the longitudinal direction of pile groups and load-deflection (p - y) curves for pile groups have been discovered, and an empirical formula is presented in order to remedy the defect of current calculating methods at home and abroad. These results can be used for reference in the design of pile foundation under lateral loads. 相似文献
22.
海上平台桶形基础模型压力压贯与负压沉贯试验研究 总被引:1,自引:0,他引:1
介绍了海上平台桶形基础模型(模型桶)压力压贯和负压沉贯的试验概况,对比分析了两者贯入力的巨大差异和产生的原因,给出了模型桶压力压贯中贯入深度与压力的关系,负压没贯负压与贯入深度,抽吸泵流量,基土渗流量,桶内土塞隆起之间的关系,试验结果表明,负压沉贯可以大大降低以砂质粉土为基土的土抗力,为在胜利油田类似基土海域海上平台应用桶形基础提供了试验依据,为海上现场导管架桶形基础平台的安装就位施工和控制提供了 相似文献
23.
不同软基处理方法适用性比较 总被引:8,自引:0,他引:8
总结分析了国内外现有的软土地基处理的各种方法。通过对采用不同方法进行软基处理的工程实例处理效果的定量对比,发现不同软基处理方法的适用性差异很大,多数工程中仅用一种方法很难达到设计要求,而两种或多种方法联合则可望取得更好的效果。 相似文献
24.
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
25.
26.
1 IntroductionKnowledge of suspended particle size and distri-bution is the key elements for better understandingthe sediment transport processes ( Wang et al.,2004), primary production (Ning et al., 2004),water quality controlling and pollution predictio… 相似文献
27.
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
28.
分析了新建水坝及社会经济发展因素对坝下游水流及泥沙的影响,用一个简易河床模型来说明新建大坝后下游河床的演变规律,通过坝下游河床一般演变分析来阐述局部冲刷对已建水工建筑物基础的影响及对已建水工建筑基础的防护措施。 相似文献
29.
30.
Based on the dynamic theories of water waves and Mindlin plates,the analytic solution of interaction between surface waves and two-dimensional floating elastic plates with edge-restraint is constructed by use of the Wiener-Hopf technique.Firstly,without regard for elastic edge restraint,the wave-induced responses of elastic floating plate analyzed by the present method are in good agreement with the results from literature and experimental results.Therefore,it can be shown that the present method is valid.Secondly,three end-restraint cases(i.e.,the left-end elastic restraints,the both-end elastic restraints,and the right-end elastic restraints)are proposed to reduce the vibration of floating plates,in which the spring is used to connect the sea bottom and the floating plate's left(or right)edge.The relations between the spring stiffness and the parameters of wave-induced responses of floating plates are discussed.Moreover,the effective method to reduce the vibration of floating elastic plates can be obtained through comparison. 相似文献