全文获取类型
收费全文 | 20544篇 |
免费 | 532篇 |
国内免费 | 200篇 |
专业分类
测绘学 | 446篇 |
大气科学 | 202篇 |
地球物理 | 536篇 |
地质学 | 1857篇 |
海洋学 | 256篇 |
天文学 | 17363篇 |
综合类 | 95篇 |
自然地理 | 521篇 |
出版年
2024年 | 44篇 |
2023年 | 76篇 |
2022年 | 157篇 |
2021年 | 96篇 |
2020年 | 95篇 |
2019年 | 163篇 |
2018年 | 58篇 |
2017年 | 44篇 |
2016年 | 74篇 |
2015年 | 175篇 |
2014年 | 161篇 |
2013年 | 156篇 |
2012年 | 242篇 |
2011年 | 235篇 |
2010年 | 299篇 |
2009年 | 1614篇 |
2008年 | 1560篇 |
2007年 | 1842篇 |
2006年 | 1840篇 |
2005年 | 1690篇 |
2004年 | 1787篇 |
2003年 | 1539篇 |
2002年 | 1344篇 |
2001年 | 1162篇 |
2000年 | 947篇 |
1999年 | 891篇 |
1998年 | 1059篇 |
1997年 | 240篇 |
1996年 | 108篇 |
1995年 | 295篇 |
1994年 | 306篇 |
1993年 | 129篇 |
1992年 | 77篇 |
1991年 | 93篇 |
1990年 | 91篇 |
1989年 | 146篇 |
1988年 | 97篇 |
1987年 | 96篇 |
1986年 | 79篇 |
1985年 | 45篇 |
1984年 | 30篇 |
1983年 | 28篇 |
1982年 | 13篇 |
1981年 | 9篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1977年 | 6篇 |
1905年 | 3篇 |
1900年 | 3篇 |
1897年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
411.
412.
Fabio Fontanot Pierluigi Monaco Stefano Borgani 《Monthly notices of the Royal Astronomical Society》2003,341(2):692-706
We apply the ztrace algorithm to the optical NOG and infrared PSC z galaxy catalogues to reconstruct the pattern of primordial fluctuations that have generated our local Universe. We check that the density fields traced by the two catalogues are well correlated, and consistent with a linear relation [either in δ or in log (1 +δ) ] with relative bias (of NOG with respect to PSC z ) b rel = 1.1 ± 0.1 . The relative bias relation is used to fill the optical zone of avoidance at | b | < 20° using the PSC z galaxy density field.
We perform extensive testing on simulated galaxy catalogues to optimize the reconstruction. The quality of the reconstruction is predicted to be good at large scales, up to a limiting wavenumber klim ≃ 0.4 h Mpc−1 beyond which all information is lost. We find that the improvement arising from the denser sampling of the optical catalogue is compensated by the uncertainties connected to the larger zone of avoidance.
The initial conditions reconstructed from the NOG catalogue are found (analogously to those from the PSC z ) to be consistent with a Gaussian paradigm. We use the reconstructions to produce sets of initial conditions ready to be used for constrained simulations of our local Universe. 相似文献
We perform extensive testing on simulated galaxy catalogues to optimize the reconstruction. The quality of the reconstruction is predicted to be good at large scales, up to a limiting wavenumber k
The initial conditions reconstructed from the NOG catalogue are found (analogously to those from the PSC z ) to be consistent with a Gaussian paradigm. We use the reconstructions to produce sets of initial conditions ready to be used for constrained simulations of our local Universe. 相似文献
413.
I.A. Crawford 《Astrophysics and Space Science》2003,285(3-4):661-675
I review the recent discoveries of variable interstellar absorption lines, widely taken to imply the existence of very small
scale(10–100 AU) structure in the interstellar medium. Possible origins of this structure are discussed, and attention is
drawn to the fact that most known examples seem to be associated with interstellar shells and bubbles of various kinds. On
the other hand, in at least one case (κ Velorum),the variation appears to occur in the supposedly quiescent cold neutral medium,
consistent with earlier studies of small scale structure in atomic hydrogen probed at radio wavelengths. Further work is urgently
required to determine the prevalence, mode of formation, and the physical and chemical state of these enigmatic structures.
Only then will their implications for our wider understanding of the interstellar medium become apparent.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
414.
415.
416.
S. Baes-Fischlmair W.W. Zeilinger J.-C. Vega-Beltran J.E. Beckman 《Astrophysics and Space Science》2003,284(2):735-738
It is assumed that the two-fold disc-wide symmetry of spirals is caused by density waves, but also the potential of a bar
component may have a significant influence on structural properties. The strength of the bar component appears to be anti-correlated
with the degree of symmetry of star-forming regions in the spiral arms (Rozas et al., 1998). We present new results of R and
Hα surface photometry of a sample of bright barred spirals. A photometric decompositon of the galaxy components is carried
out in order to make a more accurate measurement of the strength of the bar and its interrelation to gas and stars in the
disc.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
417.
418.
Juan Zhao Yan-Ben Han Zhi-An LiDepartment of Astronomy Beijing Normal University Beijing zj@bnu.edu.cnNational Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2004,4(2):189-197
Using continuous wavelet transform, we examine the relationship between solar activity and the annual precipitation in the Beijing area. The results indicate that the annual precipitation is closely related to the variation of sunspot numbers, and that solar activity probably plays an important role in influencing the precipitation on land. 相似文献
419.
420.
P. G. Jonker G. Nelemans Z. Wang A. K. H. Kong D. Chakrabarty M. Garcia P. J. Groot M. van der Klis T. Kerr B. Mobasher M. Sullivan T. Augusteijn B. W. Stappers P. Challis R. P. Kirshner J. Hjorth A. Delsanti 《Monthly notices of the Royal Astronomical Society》2003,344(1):201-206
We have obtained optical and near-infrared images of the field of the accreting millisecond X-ray pulsar XTE J1751−305. There are no stars in the 0.7-arcsec error circle (0.7 arcsec is the overall uncertainty arising from tying the optical and X-ray images and from the intrinsic uncertainty in the Chandra X-ray astrometric solution). We derive limiting magnitudes for the counterpart of R > 23.1, I > 21.6, Z > 20.6, J > 19.6 and K > 19.2 . We compare these upper limits with the magnitudes one would expect for simple models for the possible donor stars and the accretion disc subject to the reddening observed in X-rays for XTE J1751−305 and when put at the distance of the Galactic Centre (8.5 kpc). We conclude that our non-detection does not constrain any of the models for the accretion disc or possible donor stars. Deep, near-infrared images obtained during quiescence will, however, constrain possible models for the donor stars in this ultracompact system. 相似文献