全文获取类型
收费全文 | 15690篇 |
免费 | 3876篇 |
国内免费 | 5789篇 |
专业分类
测绘学 | 2476篇 |
大气科学 | 2547篇 |
地球物理 | 3031篇 |
地质学 | 9823篇 |
海洋学 | 3667篇 |
天文学 | 326篇 |
综合类 | 1427篇 |
自然地理 | 2058篇 |
出版年
2024年 | 136篇 |
2023年 | 395篇 |
2022年 | 971篇 |
2021年 | 1206篇 |
2020年 | 1043篇 |
2019年 | 1218篇 |
2018年 | 1132篇 |
2017年 | 997篇 |
2016年 | 1023篇 |
2015年 | 1160篇 |
2014年 | 1122篇 |
2013年 | 1320篇 |
2012年 | 1462篇 |
2011年 | 1424篇 |
2010年 | 1378篇 |
2009年 | 1242篇 |
2008年 | 1280篇 |
2007年 | 1183篇 |
2006年 | 1052篇 |
2005年 | 869篇 |
2004年 | 671篇 |
2003年 | 414篇 |
2002年 | 474篇 |
2001年 | 446篇 |
2000年 | 399篇 |
1999年 | 281篇 |
1998年 | 171篇 |
1997年 | 129篇 |
1996年 | 144篇 |
1995年 | 96篇 |
1994年 | 71篇 |
1993年 | 80篇 |
1992年 | 74篇 |
1991年 | 61篇 |
1990年 | 46篇 |
1989年 | 19篇 |
1988年 | 28篇 |
1987年 | 22篇 |
1986年 | 17篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1979年 | 8篇 |
1957年 | 3篇 |
1954年 | 8篇 |
1933年 | 5篇 |
1925年 | 4篇 |
1923年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Peng Yue Fan Gao Boyi Shangguan Zheren Yan 《International journal of geographical information science》2020,34(11):2243-2274
ABSTRACT High performance computing is required for fast geoprocessing of geospatial big data. Using spatial domains to represent computational intensity (CIT) and domain decomposition for parallelism are prominent strategies when designing parallel geoprocessing applications. Traditional domain decomposition is limited in evaluating the computational intensity, which often results in load imbalance and poor parallel performance. From the data science perspective, machine learning from Artificial Intelligence (AI) shows promise for better CIT evaluation. This paper proposes a machine learning approach for predicting computational intensity, followed by an optimized domain decomposition, which divides the spatial domain into balanced subdivisions based on the predicted CIT to achieve better parallel performance. The approach provides a reference framework on how various machine learning methods including feature selection and model training can be used in predicting computational intensity and optimizing parallel geoprocessing against different cases. Some comparative experiments between the approach and traditional methods were performed using the two cases, DEM generation from point clouds and spatial intersection on vector data. The results not only demonstrate the advantage of the approach, but also provide hints on how traditional GIS computation can be improved by the AI machine learning. 相似文献
2.
ECOLOGICAL SERIES OF SOIL ANIMALS IN DARLIDAI MOUNTAIN 总被引:1,自引:0,他引:1
HOUWei-ling FANHong 《中国地理科学(英文版)》2002,12(4):378-382
The ecological series of soil animals under the broad-leaved and pine mixed forest in Darlidai Mountainwas studied. Seven sample plots were selected according to different altitude gradients, which belong to different vegeta-tion types. By investigating and analyzing soil animals in every sample plot it is found that there are 45 groups and 1956individuals, which axe involved in 3 phylums, 7 classes, 16 orders, respectively. The altitude is a key factor which af-fects ecological series of soil animals. Both the groups and individuals of soil animals increase with altitude increasingunder certain conditions, which contrastes with ordinary cases, resulting from special micro-climate in studied area. Thegroups and individuls of soil animals are the most under the broad-leaved and pine forest on the top of the mountain, andthe least under Picea-Abies forest in the foot of the mountain. 相似文献
3.
4.
隧道工程地质评价的内容和方法 总被引:2,自引:0,他引:2
结合工程隧道实际,首先阐述了隧道工程的基本地质环境和工程地质条件,然后针对隧道工程可能出现的不良地质现象和可采取的工程措施,从大气降水、围岩稳定、围岩压力、洞口稳定、隧道比选等角度探讨隧道工程地质评价的主要方法和一般内容,进行隧道工程地质评价,为隧道施工、支护提供了依据. 相似文献
5.
The Tamtsag Basin is located in the extreme eastern portion of the Mongolia. The Basin and its counterpart in China (the Hailar Basin) are united a whole basin on the structural setting. In recent years, the Tamtsag Basin attracts more and more attention with the important exploration discovered in the 19th block by SOCO and in Hailar Basin of China. This paper discusses the exploration potential of Tamtsag Basin from the viewpoint of petroleum geology. 相似文献
6.
7.
8.
The effect of ocean wave breaking as a non-Bragg mechanism on backscattering cross-section and modulation transfer functions (MTF) of radar was investigated based on Bragg resonance theory and parametric method. The result showed that the additional effect of wave breaking on backscattering cross-section is not more than 20% except for the small incident angle of VV polarized electromagnetic (e.m.) wave but is significant for HH polarized e.m. wave. Breaking waves lead to increase in the modulus of tilt modulation MTF and the larger the wind speed, the faster the increase. For large incident angle, the modulus of tilt modulation MTF with wave breaking decreases quickly with incident angle for HH polarization and approach to that without wave breaking for VV polarization. The hydrodynamic MTF increases 30%-60% when considering wave breaking and the increase is larger for HH polarization than for VV polarization. 相似文献
9.
10.
应用地壳波浪与镶嵌构造学说对富氏谱分析法提取地壳垂直形变信息的科学性做了地质学意义上的阐释 ,并提出了根据多期形变资料提取特定波段上构造策应力的数学模型 相似文献