全文获取类型
收费全文 | 166篇 |
免费 | 11篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 8篇 |
地球物理 | 42篇 |
地质学 | 61篇 |
海洋学 | 7篇 |
天文学 | 54篇 |
综合类 | 2篇 |
自然地理 | 3篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 4篇 |
2016年 | 10篇 |
2015年 | 8篇 |
2014年 | 9篇 |
2013年 | 5篇 |
2012年 | 8篇 |
2011年 | 8篇 |
2010年 | 12篇 |
2009年 | 10篇 |
2008年 | 6篇 |
2007年 | 8篇 |
2006年 | 13篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 10篇 |
2002年 | 11篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1993年 | 1篇 |
1991年 | 3篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1977年 | 1篇 |
1975年 | 3篇 |
1974年 | 1篇 |
1970年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有179条查询结果,搜索用时 15 毫秒
131.
This investigation deals with the measured seismic response of a six‐storey asymmetric structural model with frictional dampers. Its main objective is to experimentally prove the concept of weak torsional balance for mass‐ and stiffness‐eccentric model configurations. The goal is to control the torsional response of these asymmetric structures and to achieve, if possible, a weak form of torsional balance by placing the so‐called empirical centre of balance (ECB) of the structure at equal distance from the edges of the building plan. The control of the dynamic response of asymmetric structures is investigated herein by using steel–teflon frictional dampers. As expected from theory, experimental results show that the mean‐square and peak displacement demand at the flexible and stiff edges of the plan may be similar in magnitude if the dampers are optimally placed. Frictional dampers have proven equally effective in controlling lateral‐torsional coupling of torsionally flexible as well as stiff structures. On the other hand, it is shown that impulsive ground motions require larger frictional capacities to achieve weak torsional balance. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
132.
133.
Ignacio J. Diaz-Bobillo Pedro E. Zadunaisky 《Celestial Mechanics and Dynamical Astronomy》1987,42(1-4):385-403
In this paper we study the time evolution of the non-gravitational forces (NGF) along with the observational bias, during the 1986 return of comet Halley. First, evidence is presented which shows that a NGF model with constant coefficients along the radial and transverse directions (A1 andA2), and a constant coefficient radial-only observation bias model fails to represent the observations within the conservative optical measurement noise of one second of arc. Second, we present a stochastic approach to the problem, where coefficients for the radial, transverse and normal components of both the NGF and the observation bias, are allowed to vary in time as three statistically independent Gauss-Markov processes. Finally, an orbit is estimated with this model, to fit observations made during the last apparition, employing a stochastic optimal smoother.Results are given in terms of time histories of the coefficient estimates along with their smoother computed uncertainties. A plot of the observation residuals is also included, showing a uniform and unbiased behavior. The analysis of the results confirms some of the assumptions often made when modelling cometary motion, but questions others. In particular, the normal bias coefficient shows an unexpected pre-perihelion peak (–1200±250 km) which proves that a radial-only observation bias model may lead to biased orbital estimates and unrealistic computed uncertainties. 相似文献
134.
Summary Over 85% of the harmonic components of the tide along the west coast of Mexico have amplitudes smaller than 2 cm. Yet they are fully resolvable from the noise back-ground so that cotidal charts could be drawn for minor components such asQ
1
andT
2
. A cotidal chart forS
1
ist also presented; the presence of this component is attributed not to the tidal forces but to some irregularity in the shape of the Earth or in the distribution of its mass. Third order effects of a magnitude of 1 to 9 mm are evident in the semidiurnal band; they actually exceed the second order input at some stations. The presence of compound harmonics of nonlinear origin, such as2MK
2
,MOK
2 andNK
3
is also detectable.
Über einige sehr kleine harmonische Konstanten, die in den Gezeiten des Pazifiks vorkommen
Zusammenfassung Über 85% der harmonischen Komponenten entlang der Westküste von Mexiko haben Amplituden kleiner als 2 cm. Dennoch sind sie vollständig aus dem Hintergrundrauschen herauszufiltern, so daß für kleinere Komponenten wieQ 1 undT 2 Karten der Linien gleicher Amplitude und Phase gezeichnet werden können. FürS 1 wird ebenfalls eine solche Karte dargestellt. Das Vorhandensein dieser Komponente ist nicht auf die Gezeitenkräfte zurückzuführen, sondern auf Unregelmäßigkeiten in der Gestalt der Erde oder in der Verteilung ihrer Masse. Effekte dritter Ordnung in einer Größe von 1 bis 9 mm sind offensichtlich in halbtägigen Gezeiten enthalten. Sie übersteigen sogar die der zweiten Ordnung an einigen Stationen. Das Vorhandensein von Verbundtiden nichtlinearen Ursprungs wie2MK 2 ,MOK 2 undNK 3 ist ebenfalls erkennbar.
Propos sur les très petites constantes harmoniques perceptibles dans les marées du Pacifique
Résumé Plus de 85% des composantes de la marée, le long de la côte occidentale du Mexique, ont une amplitude qui n'excède pas 2 cm. Néanmoins, elles émergent clairement du bruit de fond, ce qui permet même d'en tracer des cartes cotidales, soient celles deQ 1 ouT 2 par exemple. Nous présentons aussi une telle carte pourS 1 : nous attribuons son existence non à la force de marée, mais plutôt à quelque déformité dans la géoide ou dans la distribution de sa masse. Des effets de troisième ordre, de 1 à 9 mm d'envergure, sont manifestes dans la bande semidiurne; en fait ils dépassent la contribution du deuxième ordre en certains endroits. Des composantes d'origine non linéaire, comme2MK 2 ,MOK 2 etNK 3 , se descernent aussi.相似文献
135.
136.
Jaume Dinarès-Turell Juan Ignacio Baceta Xabier Orue-Etxebarria Stefano Lorito 《Earth and Planetary Science Letters》2003,216(4):483-500
The magnetostratigraphy of a 54-m-long section above the Cretaceous-Tertiary boundary at the sea-cliff section of Zumaia in the Basque basin (northern Spain) has been established. The section encompasses the entire Danian and the lower part of the Selandian stages as indicated by calcareous plankton biostratigraphy. The studied interval consists of (hemi)pelagic limestone-marl alternations in the form of couplets and bundles, which range from centimetre/decimetre to metre scale respectively and a few thin-bedded calcareous turbidites. The magnetostratigraphy, based on samples from about 200 stratigraphic levels, allows the identification of six reversal boundaries from chron C29r to C26r at a bed level. The spatial (or temporal) evolution of periodicities from a lithologically coded series is studied with the continuous wavelet transform technique. A preliminary age model based on the standard CK95 GPTS indicates that the basic lithologic carbonate-marl couplet corresponds to the 19-23-kyr precession cycle (21-31-cm cycle in the depth domain) and that a bundle cycle (usually groups of four to six basic couplets) with global periodicity centred at 1.22 m corresponds to the ∼110-kyr eccentricity cycle. We have tuned the bundle cycles to the Va03_R7 eccentricity orbital solution [Astrophys. J. 592 (2003) 620-630] following an initial match of a node of the ∼2.4-Ma eccentricity modulatory cycle in the target time series to particularly carbonate-rich bundles from the upper part of the Zumaia section that displays significant power of a 4.4-m-period cycle corresponding to the ∼404-kyr eccentricity cycle. Consistency between lithologic patterns and characteristics in the eccentricity target is reasonably met although the ∼404-kyr eccentricity cycle is not persistent throughout. The tuning, however, appears robust as it brings the age of the K/T boundary at ∼65.8 Ma. It is argued that a sea-level signal (tectonically driven?) is superimposed on the climatic forcing at the Milankovitch band masking the full expression of the low-frequency astronomical periods. We provide a cycle-tuned duration for all intervening Early Palaeocene polarity chrons and estimate relative ages for bioevents. The cycle-tuned chronology indicates that the CK95 GPTS overestimates the duration of chrons C28 and C27 by 20 and 26% respectively. Our data may prove useful to better constrain Early Palaeocene biostratigraphy of calcareous plankton and in the redefinition of the boundary between the Danian and Selandian stages. 相似文献
137.
Acta Geotechnica - A data-driven framework was used to predict the macroscopic mechanical behavior of dense packings of polydisperse granular materials. The discrete element method, DEM, was used... 相似文献
138.
Ladislav Slavík Jos Ignacio Valenzuela‐Ríos Jindich Hladil Peter Carls 《Geological Journal》2007,42(5):499-512
Occurrences and distribution of extremely scarce eognathodontids do not facilitate reliable correlation across the European regions. The correlation of the traditional early Pragian of the Prague Synform (a part of the classical Barrandian area) and the Spanish Central Pyrenees (section Segre 1) is based on conodont taxa of the Icriodus steinachensis and the Pelekysgnathus serratus stocks. This correlation has the potential to be extended to other peri‐Gondwanan regions where this scarcity of eognathodontid faunas exists as well. Application of the morphotype subdivision in I. steinachensis enables approximation of the beginning of the Pragian in the Pyrenees. It is based on the entry of I. steinachensis beta morphotype; it enters together with early eognathodontid taxa in the Barrandian sections. These correlations show that routine application of certain zonal concepts can lead to misleading conclusions. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
139.
140.
Sharif Joorabian Shooshtari Mehdi Gholamalifard Mahmood Azari Roberto Serrano-Notivoli Juan Ignacio López-Moreno 《水文科学杂志》2017,62(16):2655-2673
We evaluated the potential impacts of future land cover change and climate variability on hydrological processes in the Neka River basin, northern Iran. This catchment is the main source of water for the intensively cultivated area of Neka County. Hydrological simulations were conducted using the Soil and Water Assessment Tool. An ensemble of 17 CMIP5 climate models was applied to assess changes in temperature and precipitation under the moderate and high emissions scenarios. To generate the business-as-usual scenario map for year 2050 we used the Land Change Modeler. With a combined change in land cover and climate, discharge is expected to decline in all seasons except the end of autumn and winter, based on the inter-model average and various climate models, which illustrated a high degree of uncertainty in discharge projections. Land cover change had a minor influence on discharge relative to that resulting from climate change. 相似文献