全文获取类型
收费全文 | 44924篇 |
免费 | 353篇 |
国内免费 | 278篇 |
专业分类
测绘学 | 939篇 |
大气科学 | 2317篇 |
地球物理 | 8535篇 |
地质学 | 17398篇 |
海洋学 | 4285篇 |
天文学 | 10459篇 |
综合类 | 142篇 |
自然地理 | 1480篇 |
出版年
2022年 | 531篇 |
2021年 | 791篇 |
2020年 | 826篇 |
2019年 | 914篇 |
2018年 | 1928篇 |
2017年 | 1745篇 |
2016年 | 1879篇 |
2015年 | 741篇 |
2014年 | 1651篇 |
2013年 | 2437篇 |
2012年 | 1866篇 |
2011年 | 2243篇 |
2010年 | 2077篇 |
2009年 | 2391篇 |
2008年 | 2106篇 |
2007年 | 2320篇 |
2006年 | 2008篇 |
2005年 | 1146篇 |
2004年 | 1067篇 |
2003年 | 1029篇 |
2002年 | 964篇 |
2001年 | 939篇 |
2000年 | 831篇 |
1999年 | 561篇 |
1998年 | 595篇 |
1997年 | 619篇 |
1996年 | 438篇 |
1995年 | 468篇 |
1994年 | 436篇 |
1993年 | 366篇 |
1992年 | 342篇 |
1991年 | 368篇 |
1990年 | 415篇 |
1989年 | 335篇 |
1988年 | 323篇 |
1987年 | 352篇 |
1986年 | 266篇 |
1985年 | 395篇 |
1984年 | 389篇 |
1983年 | 391篇 |
1982年 | 354篇 |
1981年 | 325篇 |
1980年 | 350篇 |
1979年 | 283篇 |
1978年 | 314篇 |
1977年 | 270篇 |
1976年 | 227篇 |
1975年 | 242篇 |
1974年 | 233篇 |
1973年 | 264篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
291.
292.
293.
The seasonal variation of the nocturnal average intensity, and the typical variation of the sodium airglow intensity during the night have been deduced, using a data set that has been accumulated over a period of 5 years. The maximum intensity, which occurs at the equinoxes, is about 2–3 times as large as the intensity during winter, when the intensity of the D2 line is about 30 R. The nocturnal variation is symmetrical about midnight, where the intensity is some 30% less than just after (before) dusk (dawn) values. 相似文献
294.
295.
The relationship between the RMS amplitudes of the wind wave spectral components and the wind speed has been studied at ten frequencies in the band of 0.65–23 Hz. To measure the parameters of the high-frequenci waves, a resistance elevation wave gauge was operated, which was deployed in the Black See on an oceanographic platform near Katsively. The correlation between the wave amplitudes and the wind velocity at high frequencies of 5–23 Hz, corresponding to gravitation-capillary ripples, was found to reach a value of 0.8. At lower frequencies of 0.65–4.3 Hz, corresponding to short gravity waves, it dropped to 0.5–0.7. The response of spectral components to the wind speed variations in the gravity-capillary range is higher than in the range of short gravity waves. The results obtained differ from Phillips' idea about a saturated range for the frequency form of the spectrum of high-frequency gravity waves, since a linear dependence of the spectral amplitudes on the wind speed is established at a wind of force 1–8.Translated by Mikhail M. Trufanov. 相似文献
296.
297.
V. I. Krasovskii 《Planetary and Space Science》1961,8(3-4):125-136
A general review is given of the results of the airglow and auroral investigations during I.G.Y and I.G.C. in the Institute for Atmospheric Physics of the Academy of Sciences of the U.S.S.R. A strong helium emission at 10830 Å has been discovered in sunlit aurorae and in the ordinary twilight airglow. It is now observed regularly. A detailed theory of this fluorescent emission has been developed. Extensive observations on the hydroxyl bands between 5000 and 12,000 Å have been carried out at a number of stations. Marked seasonal and geographical variations have been found in them. During intense aurorae the line-width of the 6300 Å emission from great altitudes increases. The effect has been studied using Fabry-Perot interferometers. Contributions have been made to knowledge on auroral morphology. The interpretation of some of the results which are described in the review are discussed. 相似文献
298.
299.
300.