全文获取类型
收费全文 | 113206篇 |
免费 | 1538篇 |
国内免费 | 782篇 |
专业分类
测绘学 | 2582篇 |
大气科学 | 7476篇 |
地球物理 | 22142篇 |
地质学 | 40428篇 |
海洋学 | 10120篇 |
天文学 | 26166篇 |
综合类 | 299篇 |
自然地理 | 6313篇 |
出版年
2022年 | 721篇 |
2021年 | 1235篇 |
2020年 | 1336篇 |
2019年 | 1455篇 |
2018年 | 3091篇 |
2017年 | 2852篇 |
2016年 | 3359篇 |
2015年 | 1775篇 |
2014年 | 3286篇 |
2013年 | 5892篇 |
2012年 | 3573篇 |
2011年 | 4700篇 |
2010年 | 4219篇 |
2009年 | 5457篇 |
2008年 | 4724篇 |
2007年 | 4842篇 |
2006年 | 4480篇 |
2005年 | 3287篇 |
2004年 | 3225篇 |
2003年 | 3024篇 |
2002年 | 2991篇 |
2001年 | 2590篇 |
2000年 | 2526篇 |
1999年 | 2049篇 |
1998年 | 2146篇 |
1997年 | 1982篇 |
1996年 | 1722篇 |
1995年 | 1726篇 |
1994年 | 1477篇 |
1993年 | 1381篇 |
1992年 | 1293篇 |
1991年 | 1330篇 |
1990年 | 1339篇 |
1989年 | 1185篇 |
1988年 | 1088篇 |
1987年 | 1295篇 |
1986年 | 1120篇 |
1985年 | 1398篇 |
1984年 | 1591篇 |
1983年 | 1517篇 |
1982年 | 1382篇 |
1981年 | 1336篇 |
1980年 | 1176篇 |
1979年 | 1102篇 |
1978年 | 1085篇 |
1977年 | 953篇 |
1976年 | 951篇 |
1975年 | 927篇 |
1974年 | 896篇 |
1973年 | 991篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
962.
963.
G. M. Karataeva V. A. Yakovleva V. A. Hagen-Thorn O. V. Mikolaichuk 《Astronomy Letters》2001,27(2):74-80
We analyze our BVR c photometry for UGC 5600, a candidate polar ring galaxy, obtained with the 6-m telescope. We have confirmed the existence of an inner polar ring and show that the outer ring-shaped structure represents spiral arms; i.e., UGC 5600 belongs to the rare class of gas-rich spiral galaxies with inner polar rings. 相似文献
964.
We present the characteristics, operations history, performance, and calibration of the Grazing Incidence Spectrometer (GIS)
of the Coronal Diagnostic Spectrometer onboard SOHO. The GIS sensitivity has been monitored in a direct manner by examining
the quiet Sun count rates during 1996 – 2006, nearly a whole solar cycle of observations. Overall, the instrument, with its
grazing-incidence optics and microchannel plates, has performed exceptionally well. For most spectral regions, changes in
the instrument sensitivity have been very small over a 10-year period. The trends in sensitivities support the use of the
radiometric calibration of Del Zanna et al. (Astron. Astrophys.
379, 708, 2001) throughout the mission. The verification of the detector performance over such a long period allows us to point out the
spectral lines that can reliably be used for scientific analysis. 相似文献
965.
T.A. McMahon R.E. Murphy M.C. Peel J.F. Costelloe F.H.S. Chiew 《Journal of Arid Environments》2008,72(10):1853-1868
This is the first of two papers that describe the surface hydrology of the Lake Eyre Basin (LEB) (1,140,000 km2) in central Australia and compares some key characteristics with those observed from arid regions globally. This paper concentrates on annual rainfall, whereas the second paper is devoted to streamflow. The first part describes the LEB's climate (arid to semi-arid), which is dominated by a subtropical high pressure ridge stretching latitudinally across central Australia. Then follow major analyses that include the characteristics of rainfall, wet and dry spell lengths and cumulative surpluses and deficiencies, rainfall trends and intra- and inter-decadal fluctuations, and the relationship between rainfall and El Niño-Southern Oscillation (ENSO). The paper concludes with six conclusions, the key ones being: the variability of the annual rainfall (based on the coefficient of variation) in the LEB is approximately 60% greater than that found for stations located in arid regions in the rest of the world; there is a bias towards longer lengths of dry years than observed in the rest of Australia; and, there is a significant lag correlation between rainfall and ENSO, particularly in the east and in the latter part of a year. 相似文献
966.
967.
968.
969.
According to observations, drops freely falling in the air under the action of gravity are deformed and oscillate in a wide range of frequencies and scales. A technique for calculating surface axisymmetric oscillations of a deformed droplet in the linear approximation under the assumption that the amplitude and wavelength are small when compared to the droplet diameter is proposed. The basic form of an axisymmetric droplet is chosen from observations. The calculation results for surface oscillations agree with recorded data on the varying shape of water droplets falling in the air. 相似文献
970.