全文获取类型
收费全文 | 150篇 |
免费 | 14篇 |
国内免费 | 27篇 |
专业分类
测绘学 | 13篇 |
大气科学 | 12篇 |
地球物理 | 31篇 |
地质学 | 51篇 |
海洋学 | 28篇 |
天文学 | 43篇 |
综合类 | 9篇 |
自然地理 | 4篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 4篇 |
2013年 | 12篇 |
2012年 | 4篇 |
2011年 | 2篇 |
2010年 | 24篇 |
2009年 | 9篇 |
2008年 | 7篇 |
2007年 | 5篇 |
2006年 | 11篇 |
2005年 | 4篇 |
2004年 | 8篇 |
2003年 | 7篇 |
2002年 | 9篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 8篇 |
1993年 | 12篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有191条查询结果,搜索用时 15 毫秒
161.
Spatial Structure of Regular and Chaotic Orbits in Self-Consistent Models of Galactic Satellites 总被引:2,自引:2,他引:0
In several previous papers we had investigated the orbits of the stars that make up galactic satellites, finding that many
of them were chaotic. Most of the models studied in those works were not self-consistent, the single exception being the Heggie
and Ramamani (1995) models; nevertheless, these ones are built from a distribution function that depends on the energy (actually,
the Jacobi integral) only, what makes them rather special. Here we built up two self-consistent models of galactic satellites,
freezed theirs potential in order to have smooth and stationary fields, and investigated the spatial structure of orbits whose
initial positions and velocities were those of the bodies in the self-consistent models. We distinguished between partially chaotic (only one non-zero Lyapunov exponent) and fully chaotic (two non-zero Lyapunov exponents) orbits and showed that, as could be expected from the fact that the former obey an additional
local isolating integral, besides the global Jacobi integral, they have different spatial distributions. Moreover, since Lyapunov
exponents are computed over finite time intervals, their values reflect the properties of the part of the chaotic sea they
are navigating during those intervals and, as a result, when the chaotic orbits are separated in groups of low- and high-valued
exponents, significant differences can also be recognized between their spatial distributions. The structure of the satellites
can, therefore, be understood as a superposition of several separate subsystems, with different degrees of concentration and
trixiality, that can be recognized from the analysis of the Lyapunov exponents of their orbits. 相似文献
162.
Nonlinear dynamics and recurrence analysis of extreme precipitation for observed and general circulation model generated climates 下载免费PDF全文
A statistical framework based on nonlinear dynamics theory and recurrence quantification analysis of dynamical systems is proposed to quantitatively identify the temporal characteristics of extreme (maximum) daily precipitation series. The methodology focuses on both observed and general circulation model (GCM) generated climates for present (1961–2000) and future (2061–2100) periods which correspond to 1xCO2 and 2xCO2 simulations. The daily precipitation has been modelled as a stochastic process coupled with atmospheric circulation. An automated and objective classification of daily circulation patterns (CPs) based on optimized fuzzy rules was used to classify both observed CPs and ECHAM4 GCM‐generated CPs for 1xCO2 and 2xCO2 climate simulations (scenarios). The coupled model ‘CP‐precipitation’ was suitable for precipitation downscaling. The overall methodology was applied to the medium‐sized mountainous Mesochora catchment in Central‐Western Greece. Results reveal substantial differences between the observed maximum daily precipitation statistical patterns and those produced by the two climate scenarios. A variable nonlinear deterministic behaviour characterizes all climate scenarios examined. Transitions’ patterns differ in terms of duration and intensity. The 2xCO2 scenario contains the strongest transitions highlighting an unusual shift between floods and droughts. The implications of the results to the predictability of the phenomenon are also discussed. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
163.
一个自动切换混沌系统的设计与FPGA实现 总被引:2,自引:0,他引:2
为产生复杂的混沌吸引子,在现有混沌系统的基础上,利用混沌反控制法构造了1个新的混沌系统,它与原系统组成一个开关混沌系统。通过开关选择器,开关混沌系统能够在2个子系统之间自动切换。利用EDA技术在FPGA平台上实现了这个开关混沌系统,实验结果与仿真结果一致。 相似文献
164.
165.
对一种混沌图像密码的选择明文攻击 总被引:2,自引:0,他引:2
对基于广义猫映射和加法模运算的混沌密码进行了安全性分析,指出了该密码设计上的几处瑕疵。在选择明文攻击下,该密码系统在1轮加密时不够安全,仅选择3幅明文图像就可破译。讨论了该密码在多轮加密时待解决的问题以及可能采取的改进措施。 相似文献
166.
This paper studies the chaotic behaviours of a relative rotation nonlinear dynamical system under parametric excitation and its control. The dynamical equation of relative rotation nonlinear dynamical system under parametric excitation is deduced by using the dissipation Lagrange equation. The criterion of existence of chaos under parametric excitation is given by using the Melnikov theory. The chaotic behaviours are detected by numerical simulations including bifurcation diagrams, Poincaré map and maximal Lyapunov exponent. Furthermore, it implements chaotic control using non-feedback method. It obtains the parameter condition of chaotic control by the Melnikov theory. Numerical simulation results show the consistence with the theoretical analysis. The chaotic motions can be controlled to period-motions by adding an excitation term. 相似文献
167.
利用Karman关于板的大挠度理论,考虑涡电流在板中引起的Lorentz力,导出了在横向磁场和横向载荷共同作用下薄板的非线性运动方程.借助Bubnov-Galerkin法将非线性偏微分方程转化为含三次非线性项的常微分方程.在定性分析的基础上,利用次谐轨道的Melnikov函数给出了发生Smale马蹄型混沌运动的阈值条件,进而数值计算了系统的分岔图、相应的相图、Poincaré映射和时程曲线,给出了混沌运动的数字特征.分析结果表明:磁感应强度和外载荷都会影响系统的振动特性. 相似文献
168.
研究了一个新的简易混沌振荡电路系统的稳定性和混沌特性,从理论上推导了该混沌振荡电路系统的稳定和混沌的条件,并对该系统进行了精确反馈线性化控制.最后,通过电路仿真实验和硬件实验验证了理论分析的准确性. 相似文献
169.
170.
We present a comprehensive analysis of the dynamics of Veritas family members located in a chaotic strip centeredat 3.174
AU. A total of 600 chaotic members of the family and their clones were integrated for 100 Myr, and the variation of the distance
with respect to the barycenter of the family have been computed forall of them. A simple classification of the prevailing
behaviors hasbeen introduced to help identify typical dynamical patterns and states that could affect an estimate of the upper
bound to the age of the family. We pointed out the importance of the temporary captures in thequasi-stable states, which occur
often enough to affect the statistical analysis of the exits. The results are compatible with the young age (<100 Myr) for
the family of Veritas, but we cannot say precisely how young it really is.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献