全文获取类型
| 收费全文 | 20234篇 |
| 免费 | 3975篇 |
| 国内免费 | 3807篇 |
专业分类
| 测绘学 | 892篇 |
| 大气科学 | 737篇 |
| 地球物理 | 2047篇 |
| 地质学 | 12643篇 |
| 海洋学 | 1741篇 |
| 天文学 | 7347篇 |
| 综合类 | 1031篇 |
| 自然地理 | 1578篇 |
出版年
| 2024年 | 84篇 |
| 2023年 | 188篇 |
| 2022年 | 564篇 |
| 2021年 | 704篇 |
| 2020年 | 707篇 |
| 2019年 | 844篇 |
| 2018年 | 695篇 |
| 2017年 | 702篇 |
| 2016年 | 784篇 |
| 2015年 | 810篇 |
| 2014年 | 1219篇 |
| 2013年 | 1270篇 |
| 2012年 | 1255篇 |
| 2011年 | 1393篇 |
| 2010年 | 1321篇 |
| 2009年 | 1812篇 |
| 2008年 | 1663篇 |
| 2007年 | 1590篇 |
| 2006年 | 1545篇 |
| 2005年 | 1335篇 |
| 2004年 | 1204篇 |
| 2003年 | 1013篇 |
| 2002年 | 864篇 |
| 2001年 | 789篇 |
| 2000年 | 698篇 |
| 1999年 | 662篇 |
| 1998年 | 529篇 |
| 1997年 | 276篇 |
| 1996年 | 232篇 |
| 1995年 | 195篇 |
| 1994年 | 185篇 |
| 1993年 | 165篇 |
| 1992年 | 125篇 |
| 1991年 | 84篇 |
| 1990年 | 90篇 |
| 1989年 | 85篇 |
| 1988年 | 61篇 |
| 1987年 | 35篇 |
| 1986年 | 39篇 |
| 1985年 | 50篇 |
| 1984年 | 44篇 |
| 1983年 | 23篇 |
| 1982年 | 18篇 |
| 1981年 | 9篇 |
| 1980年 | 11篇 |
| 1979年 | 4篇 |
| 1978年 | 6篇 |
| 1977年 | 19篇 |
| 1972年 | 3篇 |
| 1954年 | 2篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
161.
162.
Zhang Qing Wang Li-fan Hu Jing-yao P. A. Mazzali Wang Zhen-ru 《Chinese Astronomy and Astrophysics》1995,19(4):426-431
We present the modeling of the ultraviolet and optical spectra obtained simultaneously on 1993 April 15 with the HST and at Lick Observatory. A Monte Carlo code is employed in the modeling and a comparison is made between models reported by different groups. With an atmosphere similar to the Sun in chemical composition, the observed spectral lines are well reproduced by a power law density structure of index around 20 except the strong H and HeI λ5876 lines which have peculiar absorption profiles. The photospheric velocity is found to be 9500 km/s and the blackbody temperature of the spectrum is 7990 K. For H and HeI λ5876, we suggest a two-component density structure which has a smoother layer located immediately outside the steeply decreasing inner envelope. The power law indices are most probably 20 and 3, respectively, with the transition point at about 13 000 km/s. In addition, this outer smooth layer serves to flatten the far UV spectrum as observed. 相似文献
163.
164.
165.
166.
167.
168.
169.
P. G. Jonker M. van der Klis C. Kouveliotou M. Méndez W. H. G. Lewin T. Belloni 《Monthly notices of the Royal Astronomical Society》2003,346(2):684-688
We have observed the eclipsing low-mass X-ray binary MS 1603.6+2600 with Chandra for 7 ks. The X-ray spectrum is well fit with a single absorbed power law with an index of ∼2. We find a clear sinusoidal modulation in the X-ray light curve with a period of 1.7 ± 0.2 h , consistent with the period of 1.85 h found before. However, no (partial) eclipses were found. We argue that if the X-ray flare observed in earlier X-ray observations was a type I X-ray burst, then the source can only be an accretion disc corona source at a distance of ∼11–24 kpc (implying a height above the Galactic disc of ∼8–17 kpc). It has also been proposed in the literature that MS 1603.76+2600 is a dipper at ∼75 kpc. We argue that, in this dipper scenario, the observed optical properties of MS 1603.6+2600 are difficult to reconcile with the optical properties one would expect on the basis of comparisons with other high-inclination, low-mass X-ray binaries, unless the X-ray flare was not a type I X-ray burst. In that case, the source can be a nearby soft X-ray transient accreting at a quiescent rate, as was proposed by Hakala et al., or a high-inclination source at ∼15–20 kpc. 相似文献
170.