全文获取类型
收费全文 | 1902篇 |
免费 | 218篇 |
国内免费 | 120篇 |
专业分类
测绘学 | 1187篇 |
大气科学 | 184篇 |
地球物理 | 252篇 |
地质学 | 142篇 |
海洋学 | 208篇 |
天文学 | 39篇 |
综合类 | 192篇 |
自然地理 | 36篇 |
出版年
2024年 | 9篇 |
2023年 | 52篇 |
2022年 | 54篇 |
2021年 | 58篇 |
2020年 | 46篇 |
2019年 | 84篇 |
2018年 | 72篇 |
2017年 | 73篇 |
2016年 | 72篇 |
2015年 | 82篇 |
2014年 | 96篇 |
2013年 | 102篇 |
2012年 | 87篇 |
2011年 | 110篇 |
2010年 | 99篇 |
2009年 | 96篇 |
2008年 | 104篇 |
2007年 | 88篇 |
2006年 | 74篇 |
2005年 | 68篇 |
2004年 | 86篇 |
2003年 | 69篇 |
2002年 | 50篇 |
2001年 | 56篇 |
2000年 | 52篇 |
1999年 | 43篇 |
1998年 | 54篇 |
1997年 | 51篇 |
1996年 | 42篇 |
1995年 | 46篇 |
1994年 | 25篇 |
1993年 | 29篇 |
1992年 | 23篇 |
1991年 | 19篇 |
1990年 | 18篇 |
1989年 | 17篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1958年 | 1篇 |
1957年 | 5篇 |
1954年 | 1篇 |
排序方式: 共有2240条查询结果,搜索用时 31 毫秒
102.
103.
TOPEX/POSEIDON altimeter data from October 1992 to June 2002 are used to calculate the global barotropic M2 tidal currents using long-term tidal harmonic analysis. The tides calculated agree well with ADCP data obtained from the South China Sea (SCS). The maximum tide velocities along the semi-major axis and semi-minor axis can be computed from the tidal ellipse. The global distribution of M2 internal tide vertical energy flux from the sea bottom is calculated based on a linear internal wave generation model. The global vertical energy flux of M2 internal tide is 0.96 TW, with 0.36 TW in the Pacific, 0.31 TW in the Atlantic and 0.29 TW in the Indian Ocean, obtained in this study. The total horizontal energy flux of M2 internal tide radiating into the open ocean from the lateral boundaries is 0.13 TW, with 0.06 TW in the Pacific, 0.04TW in the Atlantic, and 0.03 TW in the Indian Ocean. The result shows that the principal lunar semi-diurnal tide M2 provides enough energy to maintain the large-scale thermohaline circulation of the ocean. 相似文献
104.
Improvement of Urban Impervious Surface Estimation in Shanghai Using Landsat7 ETM+ Data 总被引:2,自引:2,他引:0
Wenze Yue 《中国地理科学(英文版)》2009,19(3):283-290
This paper explores the potential to improve the impervious surface estimation accuracy using a multi-stage approach on the
basis of vegetation-impervious surface-soil (V-I-S) model. In the first stage of Spectral Mixture Analysis (SMA) process,
pixel purity index, a quantitative index for defining endmember quality, and a 3-dimensional endmember selection method were
applied to refining endmembers. In the second stage, instead of obtaining impervious surface fraction by adding high and low
albedo fractions directly, a linear regression model was built between impervious surface and high/low albedo using a random
sampling method. The urban impervious surface distribution in the urban central area of Shanghai was predicted by the linear
regression model. Estimation accuracy of spectral mixture analysis and impervious surface fraction were assessed using root
mean square (RMS) and color aerial photography respectively. In comparison with three different research methods, this improved
estimation method has a higher overall accuracy than traditional Linear Spectral Mixture Analysis (LSMA) method and the normalized
SMA model both in root mean square error (RMSE) and standard error (SE). However, the model has a tendency to overestimate
the impervious surface distribution.
Foundation item: Under the auspices of National Natural Science Foundation of China (No. 40701177) 相似文献
105.
Fuzzy comprehensive evaluation model for water resources carrying capacity in Tarim River Basin, Xinjiang, China 总被引:12,自引:0,他引:12
This paper explores the method of comprehensive evaluation of water resources carrying capacity and sets up an evaluation model applying the fuzzy comprehensive evaluation method. Based on the data of nature, society, economics and water resources of the Tarim River Basin in 2002, we evaluated the water resources carrying capacity of the basin by means of the model. The results show that the comprehensive grades are 0.438 and 0.454 for Aksu and Kashi prefectures respectively, where the current water resources exploitation and utilization has reached a relative high degree and there is only a very limited water carrying capacity, 0.620 for Kizilsu Kirgiz Autonomous Prefecture, where water resources carrying capacity is much higher, and in between for Hotan Prefecture and Bayingolin Mongolian Autonomous Prefecture. As a whole, the comprehensive grade of the Tarim River Basin is 0.508 and the current water resources exploitation and utilization has reached a relative high degree. Thus, we suggest that the integrated management of the water resources in the basin should be strengthened in order to utilize water resources scientifically and sustainably. 相似文献
106.
将地球沉积盖层作为统一的系统,对全球常规可采石油资源进行概率估计,并对21世纪末之前的全球石油产量进行预测。结果表明全球石油产量最有可能在2020—2030年间达到高峰,每年42~47亿吨。届时主要的产区将在波斯湾、西西伯利亚和东西伯利亚,上游部门的注意力将转向北极陆架。至少到2040年前,年产量将维持在42—45亿吨水平。 相似文献
107.
Brezinski等人给出了最小二乘问题近似解的一族误差估计。该误差估计含有1个实参数。本文的贡献有3个方面:其一是给出了1种参数选择策略;其二是对该族误差估计的性质做出进一步分析;其三是分析了应用于Tikhonov正则化时应注意的一些问题。 相似文献
108.
109.
110.