全文获取类型
收费全文 | 24203篇 |
免费 | 3207篇 |
国内免费 | 4866篇 |
专业分类
测绘学 | 1683篇 |
大气科学 | 3999篇 |
地球物理 | 4850篇 |
地质学 | 11646篇 |
海洋学 | 3626篇 |
天文学 | 2246篇 |
综合类 | 1698篇 |
自然地理 | 2528篇 |
出版年
2024年 | 119篇 |
2023年 | 319篇 |
2022年 | 1017篇 |
2021年 | 1267篇 |
2020年 | 1170篇 |
2019年 | 1240篇 |
2018年 | 1477篇 |
2017年 | 1350篇 |
2016年 | 1405篇 |
2015年 | 1152篇 |
2014年 | 1398篇 |
2013年 | 1554篇 |
2012年 | 1515篇 |
2011年 | 1631篇 |
2010年 | 1450篇 |
2009年 | 1399篇 |
2008年 | 1304篇 |
2007年 | 1328篇 |
2006年 | 1173篇 |
2005年 | 768篇 |
2004年 | 632篇 |
2003年 | 623篇 |
2002年 | 701篇 |
2001年 | 684篇 |
2000年 | 565篇 |
1999年 | 623篇 |
1998年 | 502篇 |
1997年 | 518篇 |
1996年 | 457篇 |
1995年 | 431篇 |
1994年 | 395篇 |
1993年 | 321篇 |
1992年 | 298篇 |
1991年 | 222篇 |
1990年 | 175篇 |
1989年 | 187篇 |
1988年 | 141篇 |
1987年 | 113篇 |
1986年 | 87篇 |
1985年 | 66篇 |
1984年 | 63篇 |
1983年 | 57篇 |
1982年 | 67篇 |
1981年 | 38篇 |
1980年 | 30篇 |
1979年 | 36篇 |
1977年 | 22篇 |
1976年 | 24篇 |
1975年 | 25篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
241.
D. S. Drozdov F. M. Rivkin V. Rachold G. V. Ananjeva-Malkova N. V. Ivanova I. V. Chehina M. M. Koreisha Yu. V. Korostelev E. S. Melnikov 《Geo-Marine Letters》2005,25(2-3):81-88
A set of digital maps including geology, Quaternary sediments, landscapes, engineering-geological, vegetation, geocryological and the series of regional sources have been selected to characterize the Russian Arctic coast. Based on this data, new maps of engineering geocryological zoning and zoning of the coast with respect to the intensity of exogenous geological processes and risk of technogenic impacts have been generated at the scales of 1:4,000,000–1:8,000,000. These maps are a tool to assess the impact of industry on the Arctic coast of the country. 相似文献
242.
243.
In this study, the dynamic stresses within the seabed induced by non-linear progressive waves were explored through a series of hydraulic model tests on a movable bed within a wave flume. By comparing Stokes’ 2nd-order wave theory with the theory of wave-induced dynamic stresses within the seabed as proposed by Yamamoto et al. [1978. On the response of a poro-elastic bed to water waves. Journal of Fluid Mechanics 87 (1), 193–206.] and Hsu and Jeng [1994. Wane-induced soil response in an unsaturated anisotropic seabed of finite thickness. International Journal for Numerical and Analytical Methods in Geomechanics 18, 785–807], the experimental results show that the pressure on the seabed surface, the pore water pressure within the seabed as well as the vertical and the horizontal stresses are all smaller than their theoretical values. If we were to obtain the characteristics of seabed soil, the analytical solution of Hsu and Jeng [1994. Wane-induced soil response in an unsaturated anisotropic seabed of finite thickness. International Journal for Numerical and Analytical Methods in Geomechanics 18, 785–807] might agree to the simulation of the wave-induced effective stresses and shear stress in the sandy seabed. A different phase shift exists among all the three soil stresses. Their influences on the three dynamic stresses within seabed soil are important for seabed stability, and can be used in the verification of numerical models. In the whole, the non-linear progressive waves and the naturally deposited seabed are found to have a strong interaction, and the behavior of the induced dynamic stresses within the seabed is very complicated, and should be investigated integrally. 相似文献
244.
Wave-induced seabed instability, either momentary liquefaction or shear failure, is an important topic in ocean and coastal engineering. Many factors, such as seabed properties and wave parameters, affect the seabed instability. A non-dimensional parameter is proposed in this paper to evaluate the occurrence of momentary liquefaction. This parameter includes the properties of the soil and the wave. The determination of the wave-induced liquefaction depth is also suggested based on this non-dimensional parameter. As an example, a two-dimensional seabed with finite thickness is numerically treated with the EFGM meshless method developed early for wave-induced seabed responses. Parametric study is carried out to investigate the effect of wavelength, compressibility of pore fluid, permeability and stiffness of porous media, and variable stiffness with depth on the seabed response with three criteria for liquefaction. It is found that this non-dimensional parameter is a good index for identifying the momentary liquefaction qualitatively, and the criterion of liquefaction with seepage force can be used to predict the deepest liquefaction depth. 相似文献
245.
E. A. Agafonov N. A. Sorokina Yu. A. Prokhorenko E. E. Pavlova 《Physical Oceanography》1995,6(5):395-397
This paper discussesin situ observational data on the directed light attenuation index in the near-surface layer, collected in September 1987. The absolute light attenuation index has been evaluated for a near-shore strip of water 10–15 miles in width. When multidisciplinary research is conducted in the open sea, this part of the sea surface remains unstudied, as the observational grid for it is made larger than the spatial-temporal parameters of the biophysical processes producing optical inhomogeneities.Translated by Vladimir A. Puchkin. 相似文献
246.
247.
248.
The finite-elements technique is applied to study the effect of a basin’s geometry (bays, harbours) and location of the characteristics
of seiche oscillations in the basin and in the gulf proper. An increase of the length of the bay is shown to contribute to
the periods of natural oscillations and to cause their restructuring.
Translated by Vladimir A. Puchkin. 相似文献
249.
应用^57Fe穆斯堡尔谱学的方法研究了四个不同生长期合浦珠母贝铁的化学状态和Fe^2 /Fe^3 的值,它们的Fe^2 和Fe^3 的相对含量分别为4.1%~29.4%和76.6%~95.9%,Fe^2 /Fe^3 值的变化为0.043~0.42。3个月龄的Fe^2 /Fe^3 值大于10个月龄,从10个月龄到22个月龄的Fe^2 /Fe^3 值呈增加的趋势,这可能反映了不同生长期合浦珠母贝对不同价态的铁的需求。 相似文献
250.
9012号热带气旋维持的卫星云图和垂直结构特征分析 总被引:2,自引:0,他引:2
本文根据卫星云图的演变和常规天气分析相结合,对9012号热带气旋登陆后维持水消的成因进行了分析。指出该热带气旋经久不消的重要原因为其西南侧对流云团和东北侧高空槽前对流云带与热带气旋云系相衔接在中低层东北气流引导下卷入,热带气旋内部的两条云带的维持,以及利有的环流条件。 相似文献