全文获取类型
收费全文 | 14843篇 |
免费 | 3170篇 |
国内免费 | 4360篇 |
专业分类
测绘学 | 1875篇 |
大气科学 | 2330篇 |
地球物理 | 3226篇 |
地质学 | 8780篇 |
海洋学 | 2225篇 |
天文学 | 382篇 |
综合类 | 1580篇 |
自然地理 | 1975篇 |
出版年
2024年 | 103篇 |
2023年 | 319篇 |
2022年 | 864篇 |
2021年 | 1003篇 |
2020年 | 815篇 |
2019年 | 928篇 |
2018年 | 1060篇 |
2017年 | 869篇 |
2016年 | 959篇 |
2015年 | 1051篇 |
2014年 | 1087篇 |
2013年 | 1169篇 |
2012年 | 1259篇 |
2011年 | 1262篇 |
2010年 | 1231篇 |
2009年 | 1071篇 |
2008年 | 960篇 |
2007年 | 861篇 |
2006年 | 735篇 |
2005年 | 609篇 |
2004年 | 446篇 |
2003年 | 386篇 |
2002年 | 381篇 |
2001年 | 371篇 |
2000年 | 329篇 |
1999年 | 358篇 |
1998年 | 259篇 |
1997年 | 253篇 |
1996年 | 220篇 |
1995年 | 174篇 |
1994年 | 198篇 |
1993年 | 146篇 |
1992年 | 116篇 |
1991年 | 100篇 |
1990年 | 66篇 |
1989年 | 48篇 |
1988年 | 48篇 |
1987年 | 34篇 |
1986年 | 17篇 |
1985年 | 24篇 |
1983年 | 15篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 7篇 |
1979年 | 13篇 |
1965年 | 16篇 |
1958年 | 10篇 |
1957年 | 7篇 |
1954年 | 8篇 |
1933年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
61.
62.
Application of LICOM to the numerical study of the water exchangebetween the South China Sea and its adjacent oceans 总被引:8,自引:1,他引:8
1 IntroductionThe South China Sea (SCS) is the largestmarginal sea in the western Pacific (see Fig. 1). It con-nects with the SCS through the Taiwan Strait, with thePacific through the Luzon Strait, with the Sulu Seathrough the Mindoro and Balabac Straits and with theJava Sea and Andaman Sea through the Sunda Shelf(For convenience, here we refer to the section at 1.5°N,Fig. 2). It is shown that the seasonal SCS circulation ismostly affected by the summer/winter monsoon, andthe no… 相似文献
63.
Weng Keqin
Associate Professor Hydraulic Hydro-Power Engineering Dept. Tsinghua University Beijing 《中国海洋工程》1995,(2)
This paper reveals that the long-period statistic distribution of the characteristic heights of deep-water waves assumes the lognormal distribution. Thereafter, the largest wave-height which may occur in the service life of coastal structures is derived in this paper. 相似文献
64.
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
65.
以1,4—苯二酚和不同的短链脂肪酸为基本原料,经溴代、加成、形成酰卤和酰化等反应,合成了六种新的溴化脂肪酸—2,3,5,6—四溴—1,4—苯二酯。通过对产物的碳、氢、溴等元素的定量分析,以及红外吸收光谱和氢核磁共振谱的研究,验证了化合物的结构。 相似文献
66.
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
67.
中国沿海星虫动物门名录 总被引:2,自引:0,他引:2
取1980~1989年间在我国沿海进行星虫动物区系调查的标本和有关资料做了整理、鉴定,共39种,分隶于2纲,4目,6科,12属。其中1种在我国为首次记录。 相似文献
68.
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
69.
A nutrient dynamic model coupled with a 3D physical model has been developed to study the annual cycle of phytoplankton production in the Yellow Sea. The biological model involves interactions between inorganic nitrogen (nitrate and ammonium), phosphate and phytoplankton biomass. The model successfully reproduces the main features of phytoplankton-nutrient variation and dynamics of production. 1. The well-mixed coastal water is characterized by high primary production, as well as high new production. 2. In summer, the convergence of tidal front is an important hydrodynamic process, which contributes to high biomass at frontal areas. 3. The evolution of phytoplankton blooms and thermocline in the central region demonstrate that mixing is a dominant factor to the production in the Yellow Sea. In this simulation, nitrate- and ammonium-based productions are estimated regionally and temporally. The northern Yellow Sea is one of the highly ranked regions in the Yellow Sea for the capability of fixing carbon and nitrogen. The annual averaged f-ratio of 0.37 indicates that regenerated production prevails over the Yellow Sea. The result also shows that phosphate is the major nutrient, limiting phytoplankton growth throughout the year and it can be an indicator to predict the bloom magnitude. Finally, the relative roles of external nutrient sources have been evaluated, and benthic fluxes might play a significant role in compensating 54.6% of new nitrogen for new production consumption. 相似文献
70.
海洋环流模式中不同近似假设下的海表高度 总被引:1,自引:1,他引:1
Boussinesq近似是现代海洋环流模式中经常采用的假设,但随着海洋模式的不断发展完善以及气候研究应用的需要,有必要估算Boussinesq近似造成的模式误差。分别利用一个非Boussinesq近似的海洋模式与另一个结构相同且采用Boussinesq近似的模式计算海表高度,并同时利用模式预报的温度、盐度资料计算了比容异常高度。分析结果显示,这3种不同定义的海表高度无论空间结构,还是时间演变,都基本类似,尤其在热带海区最接近,差值≤1cm。Boussinesq近似意味着在模式中以体积守恒代替质量守恒,通常的做法是对其进行简单的质量补偿来保持质量守恒。比较说明,以质量补偿方法进行的高度订正对减小Boussinesq近似带来的误差没有本质的意义。 相似文献