全文获取类型
收费全文 | 8562篇 |
免费 | 336篇 |
国内免费 | 128篇 |
专业分类
测绘学 | 165篇 |
大气科学 | 712篇 |
地球物理 | 2013篇 |
地质学 | 3028篇 |
海洋学 | 800篇 |
天文学 | 1237篇 |
综合类 | 37篇 |
自然地理 | 1034篇 |
出版年
2022年 | 32篇 |
2021年 | 114篇 |
2020年 | 154篇 |
2019年 | 158篇 |
2018年 | 205篇 |
2017年 | 195篇 |
2016年 | 240篇 |
2015年 | 201篇 |
2014年 | 261篇 |
2013年 | 473篇 |
2012年 | 285篇 |
2011年 | 411篇 |
2010年 | 375篇 |
2009年 | 477篇 |
2008年 | 398篇 |
2007年 | 407篇 |
2006年 | 345篇 |
2005年 | 293篇 |
2004年 | 283篇 |
2003年 | 300篇 |
2002年 | 241篇 |
2001年 | 202篇 |
2000年 | 220篇 |
1999年 | 164篇 |
1998年 | 149篇 |
1997年 | 132篇 |
1996年 | 144篇 |
1995年 | 133篇 |
1994年 | 125篇 |
1993年 | 101篇 |
1992年 | 101篇 |
1991年 | 68篇 |
1990年 | 97篇 |
1989年 | 78篇 |
1988年 | 84篇 |
1987年 | 94篇 |
1986年 | 84篇 |
1985年 | 110篇 |
1984年 | 132篇 |
1983年 | 123篇 |
1982年 | 105篇 |
1981年 | 78篇 |
1980年 | 57篇 |
1979年 | 72篇 |
1978年 | 67篇 |
1977年 | 61篇 |
1976年 | 61篇 |
1975年 | 69篇 |
1974年 | 56篇 |
1973年 | 68篇 |
排序方式: 共有9026条查询结果,搜索用时 937 毫秒
851.
852.
David Alexander 《Astrophysics and Space Science》2007,307(1-3):197-202
The solar atmosphere displays a wide variety of dynamic phenomena driven by the interaction of magnetic fields and plasma.
In particular, plasma jets in the solar chromosphere and corona, coronal heating, solar flares and coronal mass ejections
all point to the presence of magnetic phenomena such as reconnection, flux cancellation, the formation of magnetic islands,
and plasmoids. While we can observe the signatures and gross features of such phenomena we cannot probe the essential physics
driving them, given the spatial resolution of current instrumentation. Flexible and well-controlled laboratory experiments,
scaled to solar parameters, open unique opportunities to reproduce the relevant unsteady phenomena under various simulated
solar conditions. The ability to carefully control these parameters in the laboratory allows one to diagnose the dynamical
processes which occur and to apply the knowledge gained to the understanding of similar processes on the Sun, in addition
directing future solar observations and models. This talk introduces the solar phenomena and reviews the contributions made
by laboratory experimentation. 相似文献
853.
854.
855.
ZHAO Xiaoxia Michael G FOX David C. LASENBY Alexis C. ARMIT Dolly N. KOTHAWALA 《中国海洋湖沼学报》2007,25(2):215-220
The abundance and size composition of stream isopods Lirceus fontinalis were investigated from April 2001 to August 2002 in 3 streams in southern Ontario, Canada. Effects of current speed was released from the analysis by choosing slow flowing water. The effects of substrate, season and water depth on the abundance, distribution and size composition of the isopods were analyzed. It was found that substrate and season influence isopods the most. The rocky substrate with attached filamentous macro-algae contains an isopod abundance 7.05 times that of bare rock substrate and 14.6 times that of fine-sand and mud substrate. There was a large variation with respect to seasonality in both abundance and size composition of the isopods, with the highest abundance occurring in summer and the lowest in winter and spring; individual isopods also tend to be larger in the winter and spring. In all substrates, shallow areas tend to support higher densities of isopods than deeper areas. 相似文献
856.
Eric Huff A.E. Schulz Martin White David J. Schlegel Michael S. Warren 《Astroparticle Physics》2007,26(6):351-366
The coupling of photons and baryons by Thomson scattering in the early universe imprints features in both the cosmic microwave background (CMB) and matter power spectra. The former have been used to constrain a host of cosmological parameters, the latter have the potential to strongly constrain the expansion history of the universe and dark energy. Key to this program is the means to localize the primordial features in observations of galaxy spectra which necessarily involve galaxy bias, non-linear evolution and redshift space distortions. We present calculations, based on mock catalogs produced from high-resolution N-body simulations, which show the range of behaviors we might expect of galaxies in the real universe. We investigate physically motivated fitting forms which include the effects of non-linearity, galaxy bias and redshift space distortions and discuss methods for analysis of upcoming data. In agreement with earlier work, we find that a survey of several Gpc3 would constrain the sound horizon at z 1 to about 1%. 相似文献
857.
858.
859.
Elaine M. Sadler Russell D. Cannon Tom Mauch Paul J. Hancock David A. Wake Nic Ross Scott M. Croom Michael J. Drinkwater Alastair C. Edge Daniel Eisenstein rew M. Hopkins Helen M. Johnston Robert Nichol Kevin A. Pimbblet Roberto De Propris Isaac G. Roseboom Donald P. Schneider Tom Shanks 《Monthly notices of the Royal Astronomical Society》2007,381(1):211-227
860.
The Niagara fault is believed to represent the suture between a magmatic arc terrane and a passive margin assemblage which were tectonically juxtaposed about 1.85 Ga ago during the Penokean orogeny. Accretion-related deformation is concentrated within an ~12 km wide belt that straddles the suture. A distinctive structural feature of this belt is the rotation of early fold axes toward parallelism with the direction of bulk extension, resulting in a great-circle stereonet distribution of fold axes within a vertical axial plane. Rocks of both arc and passive margin assemblages crop out in this more highly-strained belt, but there has been no material transfer between them across the fault. Structural style and metamorphic assemblages demonstrate deep-level (beneath the brittle—ductile transition) erosion of the terrane accretion boundary in the southern Lake Superior region. There is some evidence for pure shear during the accretion event, but we are unable to evaluate the amount or sense of simple shear. 相似文献