全文获取类型
| 收费全文 | 59733篇 |
| 免费 | 8614篇 |
| 国内免费 | 12107篇 |
专业分类
| 测绘学 | 7634篇 |
| 大气科学 | 9224篇 |
| 地球物理 | 10675篇 |
| 地质学 | 25279篇 |
| 海洋学 | 6779篇 |
| 天文学 | 8650篇 |
| 综合类 | 3903篇 |
| 自然地理 | 8310篇 |
出版年
| 2024年 | 206篇 |
| 2023年 | 657篇 |
| 2022年 | 1692篇 |
| 2021年 | 2065篇 |
| 2020年 | 2234篇 |
| 2019年 | 2459篇 |
| 2018年 | 1955篇 |
| 2017年 | 2443篇 |
| 2016年 | 2405篇 |
| 2015年 | 2676篇 |
| 2014年 | 3388篇 |
| 2013年 | 3830篇 |
| 2012年 | 3656篇 |
| 2011年 | 3974篇 |
| 2010年 | 3384篇 |
| 2009年 | 4328篇 |
| 2008年 | 4154篇 |
| 2007年 | 4395篇 |
| 2006年 | 4267篇 |
| 2005年 | 3562篇 |
| 2004年 | 3293篇 |
| 2003年 | 2866篇 |
| 2002年 | 2404篇 |
| 2001年 | 2058篇 |
| 2000年 | 1930篇 |
| 1999年 | 1685篇 |
| 1998年 | 1590篇 |
| 1997年 | 1217篇 |
| 1996年 | 1017篇 |
| 1995年 | 875篇 |
| 1994年 | 809篇 |
| 1993年 | 682篇 |
| 1992年 | 499篇 |
| 1991年 | 374篇 |
| 1990年 | 298篇 |
| 1989年 | 259篇 |
| 1988年 | 188篇 |
| 1987年 | 118篇 |
| 1986年 | 97篇 |
| 1985年 | 89篇 |
| 1984年 | 60篇 |
| 1983年 | 35篇 |
| 1982年 | 48篇 |
| 1981年 | 33篇 |
| 1980年 | 37篇 |
| 1979年 | 17篇 |
| 1978年 | 20篇 |
| 1977年 | 35篇 |
| 1976年 | 25篇 |
| 1973年 | 17篇 |
排序方式： 共有10000条查询结果，搜索用时 15 毫秒
141.
142.
Radiation exposure and Mission Strategies
for Interplanetary Manned Missions (REMSIM) 总被引：1，自引：0，他引：1
C. Cougnet N. B. Crosby S. Eckersley C. Foullon V. Guarnieri S. Guatelli D. Heynderickx A. Holmes-Siedle C. Lobascio S. Masiello P. Nieminen G. Parisi P. Parodi M. A. Perino M. G. Pia R. Rampini P. Spillantini V. Tamburini E. Tracino 《Earth, Moon, and Planets》2004,94(3-4):279-285
Cosmic radiation is an important problem for human interplanetary missions. The “Radiation Exposure and Mission Strategies for Interplanetary Manned Missions–REMSIM” study is summarised here. They are related to current strategies and countermeasures to ensure the protection of astronauts from radiation during interplanetary missions, with specific reference to: radiation environment and its variability; radiation effects on the crew; transfer trajectories and associated fluences; vehicle and surface habitat concepts; passive and active shielding concepts; space weather monitoring and warning systems. 相似文献
143.
144.
The results of a photometric monitoring of the quasar 4C 38.41, performed at the optical R and B bands in 2002 February–March, are presented. With a 60/90 cm Schmidt telescope at the Xinglong station of the National Astronomical Observatories of China, we observed the source exhibiting amplitude variations of up to 0.78 mag in both bands during the whole campaign. Intraday and even intranight variations are detected as well. A typical variability time-scale of about 36 d is derived from our 2-month observations at the optical bands, which is identical to that found at a radio wavelength of 92 cm, suggesting a common origin for the variations in 4C 38.41 from optical to radio bands. 相似文献
145.
146.
147.
148.
A. S. Oliveira J. E. Steiner D. Cieslinski 《Monthly notices of the Royal Astronomical Society》2003,346(3):963-967
The star WR 7a, also known as SPH 2, has a spectrum that resembles that of V Sagittae stars although no O vi emission has been reported. The Temporal Variance Spectrum – TVS – analysis of our data shows weak but strongly variable emission of O vi lines which is below the noise level in the intensity spectrum.
Contrary to what is seen in V Sagittae stars, optical photometric monitoring shows very little, if any, flickering. We found evidence of periodic variability. The most likely photometric period is Pphot = 0.227(±14) d , while radial velocities suggest a period of P spec = 0.204(±13) d . One-day aliases of these periods can not be ruled out. We call attention to similarities with HD 45166 and DI Cru (= WR 46), where multiple periods are present. They may be associated to the binary motion or to non-radial oscillations.
In contrast to a previous conclusion by Pereira et al., we show that WR 7a contains hydrogen. The spectrum of the primary star seems to be detectable as the N v 4604 Å absorption line is visible. If so, it means that the wind is optically thin in the continuum and that it is likely to be a helium main sequence star.
Given the similarity to HD 45166, we suggests that WR 7a may be a qWR – quasi Wolf–Rayet – star. Its classification is WN4h/CE in the Smith, Shara & Moffat three-dimensional classification system. 相似文献
Contrary to what is seen in V Sagittae stars, optical photometric monitoring shows very little, if any, flickering. We found evidence of periodic variability. The most likely photometric period is P
In contrast to a previous conclusion by Pereira et al., we show that WR 7a contains hydrogen. The spectrum of the primary star seems to be detectable as the N v 4604 Å absorption line is visible. If so, it means that the wind is optically thin in the continuum and that it is likely to be a helium main sequence star.
Given the similarity to HD 45166, we suggests that WR 7a may be a qWR – quasi Wolf–Rayet – star. Its classification is WN4h/CE in the Smith, Shara & Moffat three-dimensional classification system. 相似文献
149.
150.