全文获取类型
收费全文 | 3389篇 |
免费 | 192篇 |
国内免费 | 32篇 |
专业分类
测绘学 | 75篇 |
大气科学 | 271篇 |
地球物理 | 1020篇 |
地质学 | 1145篇 |
海洋学 | 405篇 |
天文学 | 477篇 |
综合类 | 19篇 |
自然地理 | 201篇 |
出版年
2023年 | 8篇 |
2022年 | 18篇 |
2021年 | 64篇 |
2020年 | 69篇 |
2019年 | 55篇 |
2018年 | 143篇 |
2017年 | 135篇 |
2016年 | 231篇 |
2015年 | 151篇 |
2014年 | 182篇 |
2013年 | 247篇 |
2012年 | 182篇 |
2011年 | 204篇 |
2010年 | 187篇 |
2009年 | 216篇 |
2008年 | 161篇 |
2007年 | 157篇 |
2006年 | 103篇 |
2005年 | 110篇 |
2004年 | 125篇 |
2003年 | 91篇 |
2002年 | 68篇 |
2001年 | 52篇 |
2000年 | 56篇 |
1999年 | 46篇 |
1998年 | 43篇 |
1997年 | 43篇 |
1996年 | 28篇 |
1995年 | 27篇 |
1994年 | 32篇 |
1993年 | 24篇 |
1992年 | 22篇 |
1991年 | 19篇 |
1990年 | 28篇 |
1989年 | 21篇 |
1988年 | 19篇 |
1987年 | 15篇 |
1986年 | 20篇 |
1985年 | 8篇 |
1984年 | 21篇 |
1983年 | 20篇 |
1982年 | 16篇 |
1979年 | 7篇 |
1978年 | 10篇 |
1975年 | 11篇 |
1974年 | 16篇 |
1973年 | 10篇 |
1972年 | 10篇 |
1971年 | 7篇 |
1970年 | 10篇 |
排序方式: 共有3613条查询结果,搜索用时 31 毫秒
1.
Dynamic modelling of retrogressive landslides with emphasis on the role of clay sensitivity 下载免费PDF全文
This paper presents a detailed numerical study of the retrogressive failure of landslides in sensitive clays. The dynamic modelling of the landslides is carried out using a novel continuum approach, the particle finite element method, complemented with an elastoviscoplastic constitutive model. The multiwedge failure mode in the collapse is captured successfully, and the multiple retrogressive failures that have been widely observed in landslides in sensitive clays are reproduced with the failure mechanism, the kinematics, and the deposition being discussed in detail. Special attention has been paid to the role of the clay sensitivity on each retrogressive failure as well as on the final retrogression distance and the final run‐out distance via parametric studies. Moreover, the effects of the viscosity of sensitive clays on the failure are also investigated for different clay sensitivities. 相似文献
2.
The Meseta de Somuncura forms the largest basaltic plateau (20 000 km2 ) of southern Argentina (extra-Andean domain). Most of these tholeiitic to alkaline rocks were extruded at ˜ 25 Ma (late Oligocene). The absence of rifting–thinning processes, plume activity, or slab-window phenomena leaves only one major possibility for the generation of Somuncura: asthenospheric ('OIB-like') corner flow leading to a transient thermal anomaly above the subducting plate. It is suggested herein that the intake of hot asthenosphere was forced into a favourable topography (concave-up) of the subducting plate, when a major plate reorganization event (Farallon to Nazca) was taking place in late Oligocene to early Miocene time. The fast and vigorous intake of asthenosphere would have been induced by slab roll-back, leading to decoupling of the subducting plate. The Somuncura volcanic episode can be regarded as a marker of the passage from the extremely oblique subduction of Farallon, to the birth of the Nazca plate and roughly perpendicular convergence between South America and Nazca. 相似文献
3.
4.
C.A. Mendoza-Briceño 《Astrophysics and Space Science》1997,256(1-2):387-392
The thermal evolution of structures is investigated for different values of the size of structure. A simplified cooling function and a constant heating mechanism are assumed. Analytical criteria for thermal instability are obtained. It is found that the response of the thermal structure not only depends on the amplitude of the disturbances, but also on whether the disturbance increases or decreases the initial steady temperature. Additionally, the evolution of the structure is examined numerically by using a time-dependent code under the assumption that the inertia terms are small. In particular, the analytical criteria obtained for thermal instability are verified. 相似文献
5.
6.
María Luisa García Vargas Angeles Díaz Roberto Terlevich Elena Terlevich 《Astrophysics and Space Science》1993,205(1):77-84
In the frame of the Starburst Model, we show that the evolution of a massive stellar cluster in a high metallicity environment can reproduce the observed emission-line spectrum and the UV-optical Spectral Energy Distribution of the Seyfert 2 galaxies and LINERs. We apply the results of our models to three objects: NGC 5506, NGC 5643 and Mk 348. 相似文献
7.
We investigate the metal enrichment of the intra-cluster medium by using a method that combines N-Body simulations and a semi-analytic
model (SAM) of galaxy formation. The cluster of galaxies is simulated in a flat, low density universe, with a numerical resolution
that allows the detection of substructures in the dark matter background of the cluster. The phenomenological approach used
to model the physical processes involved in the galaxy formation and metal production is applied to the substructures found
in the dark matter halos detected at different redshifts. Details of the chemical implementation in the SAM and first results
related to the mean properties of the baryonic matter components are presented.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
8.
Milan Burša 《Earth, Moon, and Planets》1992,56(1):57-60
The tidal long-term decrease in the angular velocity of the Earth's rotation has been estimated on the basis of the angular momentum tidal balance in the Earth-Moon-Sun system. The observed (LLR) tidal long-term decrease in the Moon's mean motion, the apparent secular acceleration in the mean longitude of the Sun and the long-term decrease in the 2nd degree zonal geopotential parameter were used.Presented at the XXth General Assembly of the I.A.G., Vienna, August 15, 1991. 相似文献
9.
O. J. Bennett A. S. Dickinson T. Leininger F. X. Gadéa 《Monthly notices of the Royal Astronomical Society》2003,341(1):361-368
The role in radiative association of narrow resonances arising from quasi-bound levels is examined. For the rate coefficient the contribution from such levels is readily calculated in terms of the Einstein A -coefficient from bound rovibrational levels generated using a suitable alternative boundary condition. By locating systematically all the quasi-bound levels, an enhancement by more than an order of magnitude of the rate coefficient for Li(2s) + H(1s) association above about 600 K is obtained. The effect on the LiH abundance in the early Universe is no more than an increase of a factor of 3 for limited ranges of values of the redshift. For the Li(2p) state the effect of narrow resonances appears to have been taken into account in previous calculations. 相似文献
10.
E. García L. De Haro C. O'Sullivan G. Cahill J. A. López Fernández F. Tercero B. Galocha J. L. Besada 《Experimental Astronomy》2003,15(3):173-193
A classical radioastronomy receiver is fed with a corrugated horn and an independent lens, both placed in a cryostat to lower
the noise temperature. The beam is focused and directed using a combination of elliptical and plane mirrors. This paper proposes
modifying the initial feeding system by placing the lens onto the horn aperture, thereby allowing a size reduction of the
horn and lens, and a simplification of their mechanical design. The profiled lens is shaped to correct the phase error on
the horn aperture. A quasi-optical model of the horn-plus-lens system has been developed using a Beam Mode Expansion (BME).
Results using both a hyperbolic-planar lens and a spherical-elliptical lens, as well as results obtained by using Geometrical
Optics (GO) with a Kirchoff–Huygens integration to get the far-field pattern, have been compared with measurements. As a direct
application, a full focusing system for the new 40-m radiotelescope at the “Centro Astronómico de Yebes” is presented for
the 22, 30 and 45 GHz bands. This paper has developed a QO model for a corrugated conical horn with a phase-correcting lens.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献