全文获取类型
收费全文 | 232篇 |
免费 | 34篇 |
国内免费 | 31篇 |
专业分类
测绘学 | 47篇 |
大气科学 | 76篇 |
地球物理 | 58篇 |
地质学 | 29篇 |
海洋学 | 55篇 |
天文学 | 5篇 |
综合类 | 8篇 |
自然地理 | 19篇 |
出版年
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2017年 | 5篇 |
2016年 | 5篇 |
2015年 | 5篇 |
2014年 | 8篇 |
2013年 | 33篇 |
2012年 | 8篇 |
2011年 | 11篇 |
2010年 | 8篇 |
2009年 | 19篇 |
2008年 | 12篇 |
2007年 | 14篇 |
2006年 | 14篇 |
2005年 | 6篇 |
2004年 | 8篇 |
2003年 | 13篇 |
2002年 | 12篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 10篇 |
1998年 | 11篇 |
1997年 | 6篇 |
1996年 | 11篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1985年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有297条查询结果,搜索用时 187 毫秒
71.
本文简要介绍了应用门限自回归方法处理浑沌时间序列,建立了浑沌时间序列自回归预报模型,并用其进行外推预报的基本方法及步骤。作者运用该方法建立了云南及滇西、滇东和滇西南等三个片区的半年最大震级序列的震级预报模型。由此预测了1991年上半年模型相应地区可能发生的最大地震震级。 相似文献
72.
73.
The paper describes a method for the prediction of extreme response statistics of floating offshore structures subjected to random seas by Monte Carlo simulation. The particular case of the horizontal surge motions of a tension leg platform is considered, taking into account both the first order, wave frequency and the second order, slow-drift motions. The advantage of the Monte Carlo method is its simplicity and versatility, which allows us to account for the effect of time-variant wave-drift damping, as well as nonlinear mooring characteristics without noticeable increase in the computational complexity. It is demonstrated in this paper that the commonly assumed obstacle against using the Monte Carlo method for estimating extreme responses, i.e. excessive CPU time, can be circumvented, bringing the computation time down to quite acceptable levels. 相似文献
74.
The constant and harmonic parts of the global ocean tide are modeled by up to nine major tidal constituents, namely, S2, M2,
N2, K1, P1, O1, Mf, Mm, and Ssa. Our computations start with the Fourier sine and cosine series expansion for the tidal constituents,
including the constant Mean Sea Level (MSL). Although the frequencies of the tidal constituents are considered known, the
coefficients of the sine and cosine functions are assumed to be unknown. Subsequently, the coefficients of the sine and cosine
functions, as well as the constant part of the Fourier expansion, were expanded into spherical harmonics up to degree and
order n, where n corresponds to the number of linearly independent spherical harmonic base functions needed to model the tidal constituents,
determined via independent columns of the Gram matrix. The unknown coefficients of the spherical harmonic expansions are computed
using sea level observations within cycles #1–#350 of the TOPEX/Poseidon satellite altimetry over 11 years of its mission.
A set of orthonormal base functions was generated for the marine areas covered by TOPEX/Poseidon observations from the spherical
harmonics using a Gram-Schmidt orthogonalization process. These were used for modeling the dominant tidal constituents. The
computed models based on orthonormal base functions for the nine tidal constituents and the constant part of the Fourier expansion,
were tested numerically for their validity and accuracy, proving centimeter accuracy. 相似文献
75.
The paper describes a novel approach to the problem of estimating the extreme response statistics of a drag-dominated offshore structure exhibiting a pronounced dynamic behaviour when subjected to harsh weather conditions. It is shown that the key quantity for extreme response prediction is the mean upcrossing rate function, which can be simply extracted from simulated response time histories. A commonly adopted practice for obtaining adequate extremes for design purposes requires the execution of 20 or more 3-h time domain analyses for several extreme sea states. For early phase considerations, it would be convenient if extremes of a reasonable accuracy could be obtained based on shorter and fewer simulations. The aim of the work reported in the present paper has therefore been to develop specific methods which make it possible to extract the necessary information about the extreme response from relatively short time histories.The method proposed in this paper opens up the possibility to predict simply and efficiently both short-term and long-term extreme response statistics. The results presented are based on extensive simulation results for the Kvitebjørn jacket structure, in operation on the Norwegian Continental Shelf. Specifically, deck response time histories for different sea states simulated from an MDOF model were used as the basis for our analyses. 相似文献
76.
The post-Newtonian mean anomaly advance as further post-Keplerian parameter in pulsar binary systems
Lorenzo Iorio 《Astrophysics and Space Science》2007,312(3-4):331-335
The post-Newtonian gravitoelectric secular rate of the mean anomaly ℳ is worked out for a two-body system in the framework
of the General Theory of Relativity. The possibility of using such an effect, which is different from the well known decrease
of the orbital period due to gravitational wave emission, as a further post-Keplerian parameter in binary systems including
at least one pulsar is examined. The resulting effect is almost three times larger than the periastron advance
. E.g., for the recently discovered double pulsar system PSR J0737-3039 A+B it would amount to −47.79 deg yr−1. This implies that it could be extracted from the linear part of a quadratic fit of the orbital phase because the uncertainties
both in the linear drift due to the mean motion and in the quadratic shift due to the gravitational wave are smaller. The
availability of such additional post-Keplerian parameter would be helpful in further constraining the General Theory of Relativity,
especially for such systems in which some of the other post-Keplerian parameters can be measured with limited accuracy. Moreover,
also certain pulsar-white dwarf binary systems, characterized by circular orbits like PSR B1855+09 and a limited number of
measured post-Keplerian parameters, could be used for constraining competing theories of gravity. 相似文献
77.
能源消费是碳排放的主要来源。根据IPCC碳排放计算指南缺省值计算出广东省1990―2010年的碳排放量,并对广东省近20年来碳排放进行阶段划分,采用对数平均迪氏指数法(Logarithmic Mean Divisia Index),对碳排放量进行因素分解,分析能源结构、能源效率和经济发展对碳排放的影响及作用程度。结果表明:1)1990―2010年,广东省能源消费的CO2排放总量和人均CO2排放量不断上升,万元GDP碳排放量、三次产业碳排放强度均呈下降趋势,原煤的消费是碳排放的主要来源,第二产业的CO2排放量比重最大,但呈缓慢下降趋势;2)经济发展效应对广东省能源消费碳排放的贡献率最大,其次是能源强度效应、人口规模效应,能源结构效应的贡献率最小;经济增长是碳排放量增加的主要推动因素;能源消费强度影响碳排放量的增速,能源消费强度又进一步受到产业结构和各产业能耗强度的影响,其中,第二产业能耗强度和第二产业产值比重是影响能源消费强度最主要的影响因素。 相似文献
78.
“黄蜂”边界层风速分析——
台风平均风速的时距选取与强度估计 总被引:1,自引:0,他引:1
通过对热带风暴(TC)"黄蜂"登陆的一次边界层观测所得到风速资料的分析计算,取得不同时距下平均风速序列.比较不同时距选取时登陆TC的平均风速、风向和台风强度,发现1 min平均比10 min平均水平最大风速大25.30%,风向变化不大,TC强度指数1 min与10 min相差2%~4%.时距选取较小时,TC平均风速和强度变大,所测得风速区域也变大,而风向与时距的选取没有明显关系.只是在阵风变化比较大的情况下选取小的时距可以更好的表示这种特征.所以时距选取需要对所研究问题的需要进行分析,对不同的问题选取不同的时距以得到更好的结果. 相似文献
79.
80.