全文获取类型
收费全文 | 981篇 |
免费 | 62篇 |
国内免费 | 56篇 |
专业分类
测绘学 | 30篇 |
大气科学 | 124篇 |
地球物理 | 185篇 |
地质学 | 435篇 |
海洋学 | 106篇 |
天文学 | 112篇 |
综合类 | 15篇 |
自然地理 | 92篇 |
出版年
2023年 | 11篇 |
2022年 | 10篇 |
2021年 | 27篇 |
2020年 | 23篇 |
2019年 | 26篇 |
2018年 | 39篇 |
2017年 | 52篇 |
2016年 | 37篇 |
2015年 | 42篇 |
2014年 | 56篇 |
2013年 | 75篇 |
2012年 | 47篇 |
2011年 | 60篇 |
2010年 | 49篇 |
2009年 | 65篇 |
2008年 | 42篇 |
2007年 | 39篇 |
2006年 | 41篇 |
2005年 | 38篇 |
2004年 | 37篇 |
2003年 | 26篇 |
2002年 | 38篇 |
2001年 | 21篇 |
2000年 | 26篇 |
1999年 | 14篇 |
1998年 | 16篇 |
1997年 | 8篇 |
1996年 | 5篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1976年 | 7篇 |
1975年 | 3篇 |
1973年 | 5篇 |
1968年 | 2篇 |
1947年 | 2篇 |
排序方式: 共有1099条查询结果,搜索用时 15 毫秒
121.
M. Jurado Vargas P. Merchán Benítez F. Sánchez Bajo A. Astillero Vivas 《Astrophysics and Space Science》2002,279(3):261-269
In order to determine the atmospheric extinction at Physics Department Astronomical Observatory of the University of Extremadura, located at Badajoz (Spain), several stars were observed during some clear nights of atmospheric stability in the period 1998–2000, at optical wavelengths corresponding to the filters of the Kron-Cousins and Strömgren photometric systems. The determination of the extinction coefficients was made by assuming the Bouguer's law, which was shown to be a good approximation for this study. The results exhibited temporal variations and can be considered to be associated with clean atmospheres at locations of low altitude. 相似文献
122.
123.
124.
125.
We present radio observations made with the Australia Telescope Compact Array to study the jets and lobes of three Fanaroff–Riley class I (FR I) radio galaxies: PKS B1234−723, 1452−517 and B2148−555. The total intensity and polarization radio images of the FR I jets are used to determine jet brightness and width variations, magnetic field structure and fractional polarization. The equipartition pressure is determined as a function of distance from the galaxies to probe the intergalactic medium. 相似文献
126.
Conventional ablation theory assumes that a meteoroid undergoes intensive heating during atmospheric flight and surface atoms
are liberated through thermal processes. Our research has indicated that physical sputtering could play a significant role
in meteoroid mass loss. Using a 4th order Runge-Kutta numerical integration technique, we tabulated the mass loss due to the
two ablation mechanisms and computed the fraction of total mass lost due to sputtering. We modeled cometary structure meteoroids
with masses ranging from 10−13 to 10−3 kg and velocities ranging from 11.2 to 71 km s−1. Our results indicate that a significant fraction of the mass loss for small, fast meteors is due to sputtering, particularly
in the early portion of the light curve. In the past 6 years evidence has emerged for meteor luminosity at heights greater
than can be explained by conventional ablation theory. We have applied our sputtering model and find excellent agreement with
these observations, and therefore suggest that sputtered material accounts for the new type of radiation found at great heights. 相似文献
127.
It is shown that even very slightly ionized clouds of matter and anti-matter can interpenetrate only a little on collision. Initial interpenetration produces fast electrons and positrons from annihilation. These, in turn, produce strong magneto-hydrodynamic shocks which give the small ionized component enough energy to ionize the neutral fraction and produce a Leidenfrost layer in about ten years after which interpenetration stops. 相似文献
128.
JohnJ.W.Rogers 《《幕》》2004,27(2):149-149
The editors of this volume assembled a remarkable group of contributors to discuss both the geology of East Gondwana and also many related issues. The 19 papers in this book provide a wealth of information on East Gondwana, the assembly of Gondwana as a supercontinent, the configuration of Rodinia,and general problems of the origin of continental crust and movement of continental plates. They also illustrate some of the controversies, with most papers having at least some points of difference in both fact and interpretation from other oaoers in the book. 相似文献
129.
Robert A. Watson Pedro Carreira Kieran Cleary Rod D. Davies Richard J. Davis Clive Dickinson Keith Grainge † Carlos M. Gutiérrez Michael P. Hobson Michael E. Jones Rüdiger Kneissl Anthony Lasenby Klaus Maisinger Guy G. Pooley Rafael Rebolo José Alberto Rubiño-Martin ‡ Ben Rusholme § Richard D. E. Saunders Richard Savage Paul F. Scott Ane Slosar Pedro J. Sosa Molina Angela C. Taylor David Titterington Elizabeth Waldram Althea Wilkinson 《Monthly notices of the Royal Astronomical Society》2003,341(4):1057-1065
130.
Udy J Gall M Longstaff B Moore K Roelfsema C Spooner DR Albert S 《Marine pollution bulletin》2005,51(1-4):224-238
For the managers of a region as large as the Great Barrier Reef, it is a challenge to develop a cost effective monitoring program, with appropriate temporal and spatial resolution to detect changes in water quality. The current study compares water quality data (phytoplankton abundance and water clarity) from remote sensing with field sampling (continuous underway profiles of water quality and fixed site sampling) at different spatial scales in the Great Barrier Reef north of Mackay (20 degrees S). Five transects (20-30 km long) were conducted from clean oceanic water to the turbid waters adjacent to the mainland. The different data sources demonstrated high correlations when compared on a similar spatial scale (18 fixed sites). However, each data source also contributed unique information that could not be obtained by the other techniques. A combination of remote sensing, underway sampling and fixed stations will deliver the best spatial and temporal monitoring of water quality in the Great Barrier Reef. 相似文献