全文获取类型
收费全文 | 125篇 |
免费 | 27篇 |
国内免费 | 23篇 |
专业分类
测绘学 | 6篇 |
大气科学 | 22篇 |
地球物理 | 39篇 |
地质学 | 59篇 |
海洋学 | 12篇 |
天文学 | 19篇 |
综合类 | 5篇 |
自然地理 | 13篇 |
出版年
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 3篇 |
2014年 | 12篇 |
2013年 | 8篇 |
2012年 | 7篇 |
2011年 | 12篇 |
2010年 | 8篇 |
2009年 | 10篇 |
2008年 | 5篇 |
2007年 | 8篇 |
2006年 | 15篇 |
2005年 | 6篇 |
2004年 | 6篇 |
2003年 | 6篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有175条查询结果,搜索用时 15 毫秒
71.
全球海洋模式对CFC-11分布的初步模拟研究 总被引:5,自引:2,他引:3
使用中国科学院大气物理研究所(IAP)三十层全球海洋模式(L30T63)研究了CFC-11在全球海洋中的吸收和分布,初步讨论了决定其分布特征的可能因素.该模式采用自由表面结构和Gent-McWilliams中尺度示踪物参数化方案.通过对控制试验得到的CFC-11模拟结果分析可知,CFC-11海表浓度受温度影响显著,其分布形状大致与温度相似,但梯度相反.通量的分布受温度影响很大,且表现出很明显的季节变化特征,如不饱和区一般出现在冬季海区的中层水形成处或者强对流混合存在的区域.另外,对CFC-11的模拟结果与三个大洋的五个断面航测资料做了对比,发现模拟结果与观测资料吻合较好,能比较清楚地反映CFC-11输送与等密度面垂直分布以及环流场的密切关系,如在南大洋50°S以北至35°S以南等密度面的向下加深区是CFC-11的主要贮存区等.与大多数前人的工作相比,该模拟结果较好地反映了CFC-11在南大洋的分布特征.从这些反映出该模式对于大洋十年尺度物质交换与海洋内部输送的模拟是比较准确的. 相似文献
72.
In this paper we use a Von Mises transformation to study brine transport in porous media. The model involves mass balance
equations for fluid and salt, Darcy's law and an equation of state, relating the salt mass fraction to the fluid density.
Application of the Von Mises transformation recasts the model equations into a single nonlinear diffusion equation. A further
reduction is possible if the problem admits similarity. This yields a formulation in terms of a boundary value problem for
an ordinary differential equation which can be treated by semi‐analytical means. Three specific similarity problems are considered
in detail: (i) one‐dimensional, stable displacement of fresh water and brine in a porous column, (ii) flow of fresh water
along the surface of a salt rock, (iii) mixing of parallel layers of brine and fresh water.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
73.
利用24个第五次耦合模式比较计划(Coupled Model Intercomparison Project Phase 5,CMIP5)历史试验资料,本文评估了在太阳年代际尺度准11 a周期变化下能否激发出热带太平洋显著的类拉尼娜型海表温度异常的模拟能力。再分析资料分析结果表明,“自下而上”机制解释了在太阳强迫偏强的年份,热带太平洋更容易呈现出显著的类拉尼娜型海温异常。CMIP5模式的评估结果显示,有2/5的模式可以基本再现再分析资料中太阳强迫影响下的热带东太平洋海温负异常,这些模式分为类拉尼娜组;而另有3/5的模式模拟出了相反的信号,分为类厄尔尼诺组。为了进一步探讨CMIP5模式模拟能力不同的原因,本文分析了“自下而上”机制在模式中的表现。“自下而上”机制可分为蒸发过程和海洋恒温(thermostat)过程。结果表明,模式能否模拟出类拉尼娜型海温响应取决于thermostat过程的强弱,其中类拉尼娜组的thermostat过程更强;而蒸发过程没有起到关键作用。 相似文献
74.
Nufar Avni 《Urban geography》2019,40(4):488-505
In the last decade, justice has been revived as a primary criterion for the analysis and evaluation of planning policies. This paper continues this line of research by examining a proposed redevelopment project in Washington, D.C. that sets equitable development as its goal . The proposed 11th Street Bridge Park would be a top-notch elevated park, physically and symbolically connecting D.C’s wealthy west with the disadvantaged east. The project is managed by a nonprofit organization and seemingly stands out in its progressive vision: An Equitable Development Plan has been developed in an attempt to secure the future of the local residents in light of the neighborhood's anticipated gentrification. However, preliminary findings show that despite explicit commitment to equity, the planning of the park also resurfaces racial and class tensions . The analysis of procedural and substantive aspects of justice in this case suggests that issues of recognition, power and representation are instrumental to fully understand urban (in)justices. 相似文献
75.
76.
77.
Taner Akgün Bennett Link Ira Wasserman 《Monthly notices of the Royal Astronomical Society》2006,365(2):653-672
Stairs, Lyne & Shemar have found that the arrival-time residuals from PSR B1828−11 vary periodically with a period ≈500 d. This behaviour can be accounted for by precession of the radio pulsar, an interpretation that is reinforced by the detection of variations in its pulse profile on the same time-scale. Here, we model the period residuals from PSR B1828−11 in terms of precession of a triaxial rigid body. We include two contributions to the residuals: (i) the geometric effect, which arises because the times at which the pulsar emission beam points towards the observer varies with precession phase; and (ii) the spin-down contribution, which arises from any dependence of the spin-down torque acting on the pulsar on the angle between its spin and magnetic axes. We use the data to probe numerous properties of the pulsar, most notably its shape, and the dependence of its spin-down torque on , for which we assume the sum of a spin-aligned component (with a weight 1 − a ) and a dipolar component perpendicular to the magnetic beam axis (weight a ), rather than the vacuum dipole torque ( a = 1) . We find that a variety of shapes are consistent with the residuals, with a slight statistical preference for a prolate star. Moreover, a range of torque possibilities fit the data equally well, with no strong preference for the vacuum model. In the case of a prolate star, we find evidence for an angle-dependent spin-down torque. Our results show that the combination of geometrical and spin-down effects associated with precession can account for the principal features of the timing behaviour of PSR B1828−11, without fine tuning of the parameters. 相似文献
78.
Vortex unpinning in precessing neutron stars 总被引:1,自引:0,他引:1
79.
80.