全文获取类型
收费全文 | 136篇 |
免费 | 6篇 |
专业分类
测绘学 | 4篇 |
大气科学 | 13篇 |
地球物理 | 35篇 |
地质学 | 36篇 |
海洋学 | 19篇 |
天文学 | 28篇 |
自然地理 | 7篇 |
出版年
2020年 | 5篇 |
2019年 | 1篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 6篇 |
2015年 | 6篇 |
2014年 | 6篇 |
2013年 | 13篇 |
2012年 | 5篇 |
2011年 | 14篇 |
2010年 | 8篇 |
2009年 | 6篇 |
2007年 | 7篇 |
2006年 | 5篇 |
2005年 | 4篇 |
2004年 | 6篇 |
2003年 | 8篇 |
2002年 | 1篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1967年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有142条查询结果,搜索用时 31 毫秒
131.
The effects of horizontal components of ground motion on the linear response of torsionally stiff and torsionally flexible systems, on soft and firm soil conditions, are examined. A one‐story, two‐way asymmetric structural system is used, subjected to uncorrelated ground motion components along their principal directions. Spectral densities for ground accelerations in firm and soft soils are modeled based on recorded data from large intensity Mexican earthquakes. It is shown that for firm soils, in general, these effects are important in the case of torsionally flexible systems that are stiff under translation, or for torsionally stiff systems that are flexible in translation. The percentage combination rules usually specified in seismic design codes are assessed against the dynamic response. Such combination rules can result in overly conservative design forces or underestimated design forces, particularly for torsionally flexible structures. Given the relative magnitude of the response to each ground motion component, it was found that using different percentage values in the combination rules has no significant effect on improving the estimation of the total response. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
132.
This article describes a methodology to monitor dynamic vertical sub-centimeter displacement, of a GPS antenna. The dynamic
movement of an antenna is determined by choosing the appropriate reference satellite for measurement differencing and by applying
a FFT filter on the double-difference phase residuals. The validity of the method depends on the time variations of the GPS
residuals and errors, such as, receiver noise, atmospheric contribution, multipath effects, and the antenna movement. This
research is under development and results for simulated motion are presented here. ? 2002 Wiley Periodicals, Inc. 相似文献
133.
Chlorine atom-initiated photooxidations of CH2FCF3 (HFC-134a) in O2-N2 diluent were carried out to identify the products formed from the \(CF_3 CHF\dot O\) radical reactions and to determine the product yields as a function of temperature, pressure and O2 concentration. CF3C(O)F and HC(O)F were the major ‘first-generation’ products observed, along with smaller yields of C(O)F2 and, as yet, undetermined yields of CF3OOOCF3 and CF3OOC(O)F. The relative importance of the two major \(CF_3 CHF\dot O\) reaction pathways, is expressed by the rate constant ratio $$k_{O_2 } /k_d = 3.2 \times 10^{ - 25} e^{(3510 \pm 470)/T} cm^3 molecule^{ - 1}$$ The decomposition reaction leading to HC(O)F and ?F3 radical products is predicted to be the dominant pathway at the Earth's surface while mainly CF3C(O)F formation will occur at the tropopause. 相似文献
134.
135.
Uncertainty quantification for geomechanical and reservoir predictions is in general a computationally intensive problem, especially if a direct Monte Carlo approach with large numbers of full-physics simulations is used. A common solution to this problem, well-known for the fluid flow simulations, is the adoption of surrogate modeling approximating the physical behavior with respect to variations in uncertain parameters. The objective of this work is the quantification of such uncertainty both within geomechanical predictions and fluid-flow predictions using a specific surrogate modeling technique, which is based on a functional approach. The methodology realizes an approximation of full-physics simulated outputs that are varying in time and space when uncertainty parameters are changed, particularly important for the prediction of uncertainty in vertical displacement resulting from geomechanical modeling. The developed methodology has been applied both to a subsidence uncertainty quantification example and to a real reservoir forecast risk assessment. The surrogate quality obtained with these applications confirms that the proposed method makes it possible to perform reliable time–space varying dependent risk assessment with a low computational cost, provided the uncertainty space is low-dimensional. 相似文献
136.
Manuel Falconi Ernesto A. Lacomba Jaume Llibre 《Celestial Mechanics and Dynamical Astronomy》2000,77(4):325-326
Volume Contents
Volume contents 相似文献137.
The Upper Cretaceous and Paleocene Gottero Sandstone was deposited as a small deep-sea fan on ophiolitic crust in a trench-slope
basin. It was thrust northeastward as an allochthonous sheet in Early and Middle Cenozoic time. The Gottero, as thick as 1500
m, was probably derived from erosion of Hercynian granites and associated metamorphic rocks in northern Corsica. Outcrops
of inner-fan channel, middle-fan channel and interchannel, outer-fan lobe, fan-fringe, and basin-plain facies associations
indicate that the depositional model of Mutti and Ricci Lucchi for mixed-sediment deep-sea fans can be used. The original
fan had a radius of 30 to 50 km.
Margin setting represents fan and/or source area 相似文献
138.
José F. Cariñena Luis A. Ibort Ernesto A. Lacomba 《Celestial Mechanics and Dynamical Astronomy》1987,42(1-4):201-213
We show that time scaling transformations for Hamiltonian systems are infinitesimal canonical transformations in a suitable extended phase space constructed from geometrical considerations. We compute its infinitesimal generating function in some examples: regularization and blow up in celestial mechanics, classical mechanical systems with homogeneous potentials and Scheifele theory of satellite motion.Research partially supported by CONACYT (México), Grant PCCBBNA 022553 and CICYT (Spain). 相似文献
139.
Joydeep Bhattacharya Ernesto Pereda Rangaiah Kariyappa Partha Pratim Kanjilal 《Solar physics》2001,199(2):267-290
We have applied several nonlinear techniques to the intensity oscillations of the chromospheric bright points observed at the Vacuum Tower Telescope (VTT) of the Sacramento Peak Observatory. A 35-min time sequence obtained in the Caii H line over a quiet region at the center of the solar disk under high spatial, spectral, and temporal resolution has been used. A relatively new approach is used to detect the hidden periodicity and to extract the associated periodic component(s) from an apparently irregular time series. The unique feature of this approach is that the constituent component(s) can be non-sinusoidal in nature. The periodicity analysis shows that time series of intensity oscillations of most of the bright points can be composed of two non-sinusoidal periodic components with periodicity varying between 2.4 min and 5.8 min. With the help of a multivariate embedding technique, globally significant spatial nonlinear correlation is found. The identification of the nonlinear interaction between bright points is performed by using the methods of dynamical phase synchronization and the similarity index. The analysis indicates that bright points are interconnected in the sense that some bright points are more active and can influence the other relatively passive bright points. 相似文献
140.
Gabriela Ferracutti Ernesto Bjerg Aberra Mogessie 《International Journal of Earth Sciences》2013,102(3):701-720
The layered mafic–ultramafic rocks in the Sierras de San Luis, Argentina (Las Águilas, Las Higueras and Virorco), constitute a 3–5-km-wide belt that extends over 100 km from NE to SW. They carry a sulphide mineralization consisting of pyrrhotite, pentlandite and chalcopyrite, in veins and as disseminated to massive ore. Disseminated spinels are frequently associated with the sulphide minerals as well as platinum group minerals. A strong correlation between S, Ni, Co, Cu, Cr, Pt and Pd indicates the presence of one to three levels of mineralization within the ultramafic units. The maximum concentration of these elements coincides with the units containing platinum group minerals (PGM) and spinel group minerals. This clear relationship constitutes a good prospecting guide in the search for layers with high-grade ore, probably associated with deeper stratigraphic levels where ultramafic rocks are dominant. The bulk rock chemistry and concentrations of metals and platinum group elements as well as textural evidence suggest that the parental magma was mafic with tholeiitic affinities and MgO rich. The Las Águilas layered mafic–ultramafic body and the remaining bodies in the area bear similar characteristics to well-known stratified complexes developed in extensional tectonic regimes, as it is the case of Jinchuan (China), Kabanga (Tanzania) and Fiambala (Argentina). 相似文献