全文获取类型
收费全文 | 3149篇 |
免费 | 144篇 |
国内免费 | 64篇 |
专业分类
测绘学 | 103篇 |
大气科学 | 247篇 |
地球物理 | 644篇 |
地质学 | 1151篇 |
海洋学 | 215篇 |
天文学 | 718篇 |
综合类 | 18篇 |
自然地理 | 261篇 |
出版年
2022年 | 32篇 |
2021年 | 62篇 |
2020年 | 61篇 |
2019年 | 62篇 |
2018年 | 99篇 |
2017年 | 99篇 |
2016年 | 94篇 |
2015年 | 87篇 |
2014年 | 97篇 |
2013年 | 164篇 |
2012年 | 108篇 |
2011年 | 144篇 |
2010年 | 154篇 |
2009年 | 191篇 |
2008年 | 154篇 |
2007年 | 165篇 |
2006年 | 149篇 |
2005年 | 98篇 |
2004年 | 132篇 |
2003年 | 95篇 |
2002年 | 114篇 |
2001年 | 77篇 |
2000年 | 75篇 |
1999年 | 57篇 |
1998年 | 64篇 |
1997年 | 40篇 |
1996年 | 29篇 |
1995年 | 42篇 |
1994年 | 28篇 |
1993年 | 20篇 |
1992年 | 38篇 |
1991年 | 20篇 |
1990年 | 16篇 |
1989年 | 20篇 |
1987年 | 34篇 |
1986年 | 23篇 |
1985年 | 27篇 |
1984年 | 37篇 |
1983年 | 33篇 |
1982年 | 41篇 |
1981年 | 32篇 |
1980年 | 31篇 |
1979年 | 24篇 |
1978年 | 13篇 |
1977年 | 20篇 |
1976年 | 19篇 |
1975年 | 13篇 |
1974年 | 20篇 |
1973年 | 13篇 |
1971年 | 11篇 |
排序方式: 共有3357条查询结果,搜索用时 31 毫秒
1.
2.
3.
Maarten A. Prins Hongbo Zheng Kay Beets Simon Troelstra Patrick Bacon Ilse Kamerling Wouter Wester Martin Konert Xiangtong Huang Wang Ke Jef Vandenberghe 《第四纪科学杂志》2009,24(1):75-84
The Mangshan Plateau is located on the south bank of the Huang He (Yellow River) just west of the city of Zhengzhou, well outside the Loess Plateau in central China. Mixing models of the grain‐size data indicate that the loess deposits are mixtures of three loess components. Comparison of the mixing model with existing models established for a series of loess–palaeosol sequences from the Loess Plateau indicates that the Mangshan loess has been supplied from a proximal dust source, the Huang He floodplain, during major dust outbreaks. The high accumulation rates, the composition of the loess components, and especially the high proportions of a sandy loess component support this. Owing to the exceptionally high accumulation rates, the Mangshan grain size, magnetic susceptibility and carbonate records provide a high‐resolution archive of environmental and climate change. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
4.
5.
6.
Sarah Church Peter Ade James Bock Melanie Bowden John Carlstrom Ken Ganga Walter Gear James Hinderks Wayne Hu Brian Keating John Kovac Andrew Lange Eric Leitch Olivier Mallie Simon Melhuish Anthony Murphy Ben Rusholme Creidhe OSullivan Lucio Piccirillo Clem Pryke Andy Taylor Keith Thompson 《New Astronomy Reviews》2003,47(11-12):1083
QUEST on DASI is a ground-based, high-sensitivity, high-resolution (ℓmax2500) experiment designed to map CMB polarization at 100 and 150 GHz and to measure the power spectra from E-modes, B-modes from lensing of the CMB, and B-modes from primordial gravitational waves. The experiment comprises a 2.6 m Cassegrain optical system, equipped with an array of 62 polarization-sensitive bolometers (PSBs), located at the South Pole. The instrument is designed to minimize systematic effects; features include differencing of pairs of orthogonal PSBs within a single feed, a rotatable achromatic waveplate, and axisymmetric rotatable optics. In addition the South Pole location allows both repeatable and highly controlled observations. QUEST on DASI will commence operation in early 2005. 相似文献
7.
We examine possible locations for the primordial disk of the Edgeworth-Kuiper Belt (EKB), using several subsets of the known objects as markers of the total mass distribution. Using a secular perturbation theory, we find that the primordial plane of the EKB could have remained thin enough to escape detection only if it is clustered very closely about the invariable plane of the Solar System. 相似文献
8.
Estela M. Reynoso † Simon Johnston Anne J. Green Bärbel S. Koribalski 《Monthly notices of the Royal Astronomical Society》2006,369(1):416-424
We have observed the supernova remnant (SNR) G290.1−0.8 in the 21-cm H i line and the 20-cm radio continuum using the Australia Telescope Compact Array (ATCA). The H i data were combined with data from the Southern Galactic Plane Survey to recover the shortest spatial frequencies. In contrast, H i absorption was analysed by filtering extended H i emission, with spatial frequencies shorter than 1.1 kλ. The low-resolution ATCA radio continuum image of the remnant shows considerable internal structure, resembling a network of filaments across its 13-arcmin diameter. A high-resolution ATCA radio continuum image was also constructed to study the small-scale structure in the SNR. It shows that there are no structures smaller than ∼17 arcsec, except perhaps for a bright knot to the south, which is probably an unrelated object. The H i absorption study shows that the gas distribution and kinematics in front of SNR G290.1−0.8 are complex. We estimate that the SNR probably lies in the Carina arm, at a distance 7 (±1) kpc. In addition, we have studied nearby sources in the observed field using archival multiwavelength data to determine their characteristics. 相似文献
9.
Piero F. Spinnato Michael Fellhauer Simon F. Portegies Zwart 《Monthly notices of the Royal Astronomical Society》2003,344(1):22-32
We study the efficiency at which a black hole or dense star cluster spirals in to the Galactic Centre. This process takes place on a dynamical friction time-scale, which depends on the value of the Coulomb logarithm (ln Λ). We determine the accurate value of this parameter using the direct N -body method, a tree algorithm and a particle-mesh technique with up to two million plus one particles. The three different techniques are in excellent agreement. Our measurement for the Coulomb logarithm appears to be independent of the number of particles. We conclude that ln Λ= 6.6 ± 0.6 for a massive point particle in the inner few parsec of the Galactic bulge. For an extended object, such as a dense star cluster, ln Λ is smaller, with a value of the logarithm argument Λ inversely proportional to the object size. 相似文献
10.
Viviane Pierrard Milan Maksimovic Joseph Lemaire 《Astrophysics and Space Science》2001,277(1-2):195-200
Electron velocity distribution functions (VDF) observed in the low speed solar wind flow are generally characterized by ‘core’
and ‘halo’ electrons. In the high speed solar wind, a third population of ‘strahl’ electrons is generally observed. New collisional
models based on the solution of the Fokker-Planck equation can be used to determine the importance of the different electron
populations as a function of the radial distance. Typical electron velocity distribution functions observed at 1 AU from the
Sun are used as boundary conditions for the high speed solar wind and for the low speed solar wind. Taking into account the
effects of external forces and Coulomb collisions with a background plasma, suprathermal tails are found to be present in
the electron VDF at low altitudes in the corona when they exist at large radial distances.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献