全文获取类型
| 收费全文 | 11038篇 |
| 免费 | 951篇 |
| 国内免费 | 1864篇 |
专业分类
| 测绘学 | 290篇 |
| 大气科学 | 271篇 |
| 地球物理 | 879篇 |
| 地质学 | 3954篇 |
| 海洋学 | 1918篇 |
| 天文学 | 5131篇 |
| 综合类 | 483篇 |
| 自然地理 | 927篇 |
出版年
| 2024年 | 33篇 |
| 2023年 | 94篇 |
| 2022年 | 253篇 |
| 2021年 | 254篇 |
| 2020年 | 287篇 |
| 2019年 | 334篇 |
| 2018年 | 282篇 |
| 2017年 | 261篇 |
| 2016年 | 321篇 |
| 2015年 | 329篇 |
| 2014年 | 596篇 |
| 2013年 | 654篇 |
| 2012年 | 650篇 |
| 2011年 | 774篇 |
| 2010年 | 807篇 |
| 2009年 | 1069篇 |
| 2008年 | 1007篇 |
| 2007年 | 898篇 |
| 2006年 | 845篇 |
| 2005年 | 736篇 |
| 2004年 | 606篇 |
| 2003年 | 508篇 |
| 2002年 | 414篇 |
| 2001年 | 362篇 |
| 2000年 | 318篇 |
| 1999年 | 290篇 |
| 1998年 | 192篇 |
| 1997年 | 80篇 |
| 1996年 | 84篇 |
| 1995年 | 61篇 |
| 1994年 | 68篇 |
| 1993年 | 84篇 |
| 1992年 | 33篇 |
| 1991年 | 27篇 |
| 1990年 | 28篇 |
| 1989年 | 21篇 |
| 1988年 | 22篇 |
| 1987年 | 9篇 |
| 1986年 | 17篇 |
| 1985年 | 28篇 |
| 1984年 | 25篇 |
| 1983年 | 18篇 |
| 1982年 | 20篇 |
| 1981年 | 13篇 |
| 1980年 | 12篇 |
| 1979年 | 2篇 |
| 1978年 | 7篇 |
| 1977年 | 15篇 |
| 1877年 | 1篇 |
| 1875年 | 1篇 |
排序方式： 共有10000条查询结果，搜索用时 281 毫秒
81.
We present a new Very Large Array (VLA) image of Saturn, made from data taken in October 1998 at a wavelength of λ3.6 cm. The moderate ring opening angle (B≈15°) allows us to explore direct transmission of microwave photons through the A and C rings. We find a strong asymmetry of photons transmitted through the A ring, but not in the C ring, a new diagnostic of wake structure in the ring particles. We also find a weak asymmetry between east and west for the far side of the ansae. To facilitate quantitative comparison between dynamic models of the A ring and radio observations, we extend our Monte Carlo radiative transfer code (described in Dunn et al., 2002, Icarus 160, 132-160) to include idealized wakes. We show the idealized model can reproduce the properties of dynamic simulations in directly transmitted light. We examine the model behavior in directly transmitted and scattered light over a range of physical and geometric wake parameters. Finally, we present a wake model with a plausible set of physical parameters that quantitatively reproduces the observed intensity and asymmetry of the A ring both across the planet and in the ansae. 相似文献
82.
83.
84.
85.
We report on a year's study of spatial and seasonal patterns of zooplankton abundance in Port Phillip and Westernport Bays, July 1982 to August 1983. These two bays, closely adjacent on the southern coast of Victoria, Australia, differ in several respects: Port Phillip is a nearly landlocked bay with a broad basin, while Westernport is an open tidal embayment with extensive mud and seagrass banks. Both bays have a resident zooplankton fauna distinct from that of Bass Strait. Although these resident communities have many species in common, patterns of abundance and dominance are quite different. We found that the holoplankton of Port Phillip was about half copepods, mostly Paracalanus indicus, with 23% Caldocera and 21% larvaceans. Westernport Bay zooplankton was dominated by Acartia tranteri, with no resident cladoceran fauna. Bass Strait species were more often found in Westernport than in Port Phillip Bay, but the resident community of Port Phillip Bay was more similar to that of Bass Strait than to that of Westernport.Although this study was undertaken in an exceptionally dry year, the available historical data show that the overall patterns found in 1982–1983 are typical for these bays. The differences in community composition probably relate to differences in depth profile, predator abundance, and suspended matter between the bays. 相似文献
86.
R. F. Griffin 《Journal of Astrophysics and Astronomy》1990,11(4):533-540
Photoelectric radial-velocity measurements show that HD 118670 is a double-lined spectroscopic binary in an orbit which is
not quite circular and whose period is about 48 days. Spectral types of K0 V and K7 V would satisfy the photometry and the
mass ratio; the mass function would then suggest the possibility of eclipses. However, actual spectral classification indicates
a luminosity somewhat above the main sequence 相似文献
87.
88.
89.
90.