全文获取类型
收费全文 | 986篇 |
免费 | 164篇 |
国内免费 | 123篇 |
专业分类
测绘学 | 167篇 |
大气科学 | 110篇 |
地球物理 | 363篇 |
地质学 | 236篇 |
海洋学 | 253篇 |
天文学 | 41篇 |
综合类 | 66篇 |
自然地理 | 37篇 |
出版年
2024年 | 2篇 |
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 16篇 |
2020年 | 25篇 |
2019年 | 19篇 |
2018年 | 16篇 |
2017年 | 35篇 |
2016年 | 46篇 |
2015年 | 26篇 |
2014年 | 51篇 |
2013年 | 58篇 |
2012年 | 64篇 |
2011年 | 56篇 |
2010年 | 63篇 |
2009年 | 73篇 |
2008年 | 75篇 |
2007年 | 78篇 |
2006年 | 65篇 |
2005年 | 51篇 |
2004年 | 46篇 |
2003年 | 52篇 |
2002年 | 34篇 |
2001年 | 24篇 |
2000年 | 28篇 |
1999年 | 31篇 |
1998年 | 35篇 |
1997年 | 22篇 |
1996年 | 12篇 |
1995年 | 18篇 |
1994年 | 25篇 |
1993年 | 24篇 |
1992年 | 16篇 |
1991年 | 7篇 |
1990年 | 11篇 |
1989年 | 19篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1973年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有1273条查询结果,搜索用时 8 毫秒
41.
关于波浪Boussinesq方程的研究 总被引:2,自引:0,他引:2
对有关波浪 Boussinesq方程的研究成果进行了系统的归纳总结和评述 ,以期对本学科的发展起到一定的引导和促进作用 相似文献
42.
In this paper, the characteristics of different forms of mild slope equations for non-linear wave are analyzed, and new non-linear theoretic models for wave propagation are presented, with non-linear terms added to the mild slope equations for non-stationary linear waves and dissipative effects considered. Numerical simulation models are developed of non-linear wave propagation for waters of mildly varying topography with complicated boundary, and the effects are studied of different non-linear corrections on calculation results of extended mild slope equations. Systematical numerical simulation tests show that the present models can effectively reflect non-linear effects. 相似文献
43.
44.
45.
Numerical analyses for the Bragg resonant reflection of carrier waves associated long waves due to sinusoidally varying seabeds are performed by using a set of coupled ordinary differential equations derived from the Boussinesq equations. The Boussinesq equations are firstly approximated with the Fourier decomposition. The coupled governing equations are then derived and used to simulate evolution of both short and long wave components. It is also found that wave groups are generated by two carrier waves with slightly different frequencies. The wave energy of the initial wave components is transferred to other harmonic components during propagation over a long distance. Evolution and reflection of both short and long waves were largely affected by nonlinearity. 相似文献
46.
47.
48.
Leo R. M. Maas 《Surveys in Geophysics》2004,25(3-4):249-279
The dynamics of a stratified fluid contained in a rotating rectangular box is described in terms of the evolution of the lowest moments of its density and momentum fields. The first moment of the density field also gives the position of the fluids centre-of-mass. The resulting low-order model allows for fast assessment both of adopted parameterisations, as well as of particular values of parameters. In the ideal fluid limit (neglect of viscous and diffusive effects), in the absence of wind, the equations have a Hamiltonian structure that is integrable (non-integrable) in the absence (presence) of differential heating. In a non-rotating convective regime, dynamically rich behaviour and strong dependence on the single (lumped) parameter are established. For small values of this parameter, in a self-similar regime, further reduction to an explicit map is discussed in an Appendix. Introducing rotation in a nearly geostrophic regime leads through a Hopf bifurcation to a limit cycle, and under the influence of wind and salt to multiple equilibria and chaos, respectively. 相似文献
49.
The purpose of this paper is to propose an efficient numerical method for solving Lane-Emden type equations arising in astrophysics using Bernstein polynomials. First Bernstein operational matrix of differentiation is derived using Bernstein polynomials and then applied to solve the linear and nonlinear differential equations of Lane-Emden type. Some illustrative examples are given to demonstrate the efficiency and validity of the proposed algorithm. 相似文献
50.
利用2008年4月至2012年12月菏泽市紫外线观测资料以及地面常规气象观测资料和空气质量资料,分析了该地区太阳紫外线辐射的变化特征及其与各因子的相关关系,并建立逐月预报方程。结果表明:菏泽紫外线辐射年总量达到187.98 W/m2,春夏两季明显高于秋冬两季,5月达到全年的最大值,1月为全年的最小值;3~9月紫外线辐射极大值均可达到5级,其他月份均可达到4级。不同天气条件下紫外线辐射强度存在明显差异,其中晴天紫外线辐射强且稳定,呈抛物线变化;多云天紫外线辐射波动较大,时强时弱;阴天紫外线辐射相对较弱。紫外线辐射强度与风速、能见度、气温呈正相关,与总云量、低云量、相对湿度呈负相关,与SO2、PM10、NO2、PM2.5多呈负相关。基于多元线性回归分析向后剔除变量方法得出的逐月预报方程,经检验总体预报效果较好,对当地紫外线等级预报工作具有参考意义。 相似文献