全文获取类型
收费全文 | 2714篇 |
免费 | 487篇 |
国内免费 | 794篇 |
专业分类
测绘学 | 192篇 |
大气科学 | 381篇 |
地球物理 | 656篇 |
地质学 | 1653篇 |
海洋学 | 467篇 |
天文学 | 82篇 |
综合类 | 242篇 |
自然地理 | 322篇 |
出版年
2024年 | 14篇 |
2023年 | 54篇 |
2022年 | 125篇 |
2021年 | 139篇 |
2020年 | 119篇 |
2019年 | 139篇 |
2018年 | 192篇 |
2017年 | 146篇 |
2016年 | 141篇 |
2015年 | 157篇 |
2014年 | 155篇 |
2013年 | 172篇 |
2012年 | 159篇 |
2011年 | 185篇 |
2010年 | 158篇 |
2009年 | 150篇 |
2008年 | 163篇 |
2007年 | 130篇 |
2006年 | 125篇 |
2005年 | 110篇 |
2004年 | 111篇 |
2003年 | 111篇 |
2002年 | 116篇 |
2001年 | 89篇 |
2000年 | 121篇 |
1999年 | 124篇 |
1998年 | 94篇 |
1997年 | 91篇 |
1996年 | 74篇 |
1995年 | 70篇 |
1994年 | 67篇 |
1993年 | 35篇 |
1992年 | 34篇 |
1991年 | 23篇 |
1990年 | 16篇 |
1989年 | 16篇 |
1988年 | 14篇 |
1987年 | 22篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1958年 | 3篇 |
排序方式: 共有3995条查询结果,搜索用时 31 毫秒
11.
12.
基于EOF分析对南海西北海域水体光谱特性的研究 总被引:1,自引:0,他引:1
This study presents an analysis of the spectral characteristics of remote sensing reflectance(R_(rs)) in northwestern South China Sea based on the in situ optical and water quality data for August 2018.R_(rs)was initially divided into four classes,classes A to D,using the max-classification algorithm,and the spectral properties of whole R_(rs) were characterized using the empirical orthogonal function(EOF) analysis.Subsequently,the dominant factors in each EOF mode were determined.The results indicated that more than 95% of the variances of R_(rs) are partly driven by the back-scattering characteristics of the suspended matter.The initial two EOF modes were well correlated with the total suspended matter and back-scattering coefficient.Furthermore,the first EOF modes of the four classes of R_(rs)(A-D R_(rs)-EOF_1) significantly contributed to the total variances of each R_(rs) class.In addition,the correlation coefficients between the amplitude factors of class A-D R_(rs)-EOF_1 and the variances of the relevant water quality and optical parameters were better than those of the unclassified ones.The spectral shape of class AR_(rs)-EOF_1 was governed by the absorption characteristic of chlorophyll a and colored dissolved organic matter(CDOM).The spectral shape of class B R_(rs)-EOF_1 was governed by the absorption characteristic of CDOM since it exhibited a high correlation with the absorption coefficient of CDOM(a_g(λ)),whereas the spectral shape of class C R_(rs)-EOF_1 was governed by the back-scattering characteristics but not affected by the suspended matter.The spectral shape of class D R_(rs)-EOF_1 exhibited a relatively good correlation with all the water quality parameters,which played a significant role in deciding its spectral shape. 相似文献
13.
14.
15.
A one-dimentional three-layer model for the thermal structure in the Huanghai Sea is presented in this study, me model consists of the upper mixed layer caused by heating and wind mixing, the lower mixed layer driven by tidal mixing, and the thermocline with certain thickness. The entrainment velocities of the upper and lower layers are obtained respectively. The results show that the model is capable of describing the development and decline processes of the seasonal thermocline in the Huanghai Sea, simulating successfully the Huanghai Sea Cold Water Mass, the nearshore front and surface cold water off North Jiangsu and explaining reasonably their formation mechanisms as well as the strong thermocline off Qingdao. It is suggested that the tidal mixing plays key role in the formation of the nearshore front off North Jiangsu and the strong thermocline off Qingdao. The wind mixing and the tidal mixing make the lower layer water with high nutrients go up to the upper layer. This physical process may be sig 相似文献
16.
Based on the recent research results on dry and wet deposition of nutrient elements and sulphate,we estimate the atmospheric flux of nutrient elements and sulphate to the southern Yellow Sea and the East China Sea in each season.The results suggest that the concentrations of nutrient elements and sulphate in aerosol and precipitation show an apparent seasonal cycle with the maximum values in winter and the minimum values in summer.Depositions of nitrate and sulphate are dominated by wet deposition,while the deposition for phosphate is mainly dry deposition.Moreover,compared with the riverine inputs,the atmospheric deposition may be the main source of dissolved inorganic nutrients in the southern Yellow Sea and the East China Sea. 相似文献
17.
平台在海上受风、浪、流、冰等水平载荷作用产生倾斜 ,而土壤粘接力、摩擦力和土抗力是平台的抗拔和抗倾力 ,桶基平台应满足抗拔、抗倾稳定的要求 ,以保证平台的整体稳定性。讨论了桶基平台受水平力作用时 ,桶形基础的破坏模式及其计算方法 ,阐述了抗倾稳定计算方法 相似文献
18.
用三峡及邻区(东经108°~113°,北纬29°~33°)地质资料,地震资料,现 场地应力测量资料论证三峡及邻区晚第三纪以来构造应力场稳定性及其分区特 征。 相似文献
19.
为研究大尺度海洋环流和一些大尺度海洋物理过程,我们建立了一个无海底地形的三层斜压海洋环流数值模式。模式方程采用了静力近似和Boussinesq近似,在上边界采用了钢盖近似。同时,还做了两个数值试验:第一个模拟试验,海洋从静止状态开始,以4个季节的气候平均风应力和海表大气季节平均温度为强迫条件,积分区城选择45℃以北的太平洋,数值积分了5个模式年,这时海洋的上层环流和温度的年变化趋于平稳。计算结果再现了太平洋气候平均状态的海温分布和主要海流的大尺度特征以及它们的年变化特征。如西部强化流、赤道潜流等。第二个数值试验,在第一个数值模拟的基础上给定赤道西太平洋一个风应力异常区,数值积分了几个月。从计算结果中可看到类似E1 Ni■o的现象,并且初步地分析了赤道波动在E1 Ni■o形成过程中的作用。 相似文献
20.