全文获取类型
收费全文 | 13911篇 |
免费 | 2612篇 |
国内免费 | 2743篇 |
专业分类
测绘学 | 626篇 |
大气科学 | 1009篇 |
地球物理 | 4056篇 |
地质学 | 6696篇 |
海洋学 | 1959篇 |
天文学 | 2018篇 |
综合类 | 692篇 |
自然地理 | 2210篇 |
出版年
2024年 | 74篇 |
2023年 | 251篇 |
2022年 | 475篇 |
2021年 | 488篇 |
2020年 | 528篇 |
2019年 | 603篇 |
2018年 | 497篇 |
2017年 | 518篇 |
2016年 | 553篇 |
2015年 | 590篇 |
2014年 | 693篇 |
2013年 | 634篇 |
2012年 | 753篇 |
2011年 | 797篇 |
2010年 | 654篇 |
2009年 | 956篇 |
2008年 | 877篇 |
2007年 | 943篇 |
2006年 | 931篇 |
2005年 | 806篇 |
2004年 | 806篇 |
2003年 | 809篇 |
2002年 | 648篇 |
2001年 | 601篇 |
2000年 | 576篇 |
1999年 | 499篇 |
1998年 | 557篇 |
1997年 | 329篇 |
1996年 | 312篇 |
1995年 | 291篇 |
1994年 | 258篇 |
1993年 | 227篇 |
1992年 | 191篇 |
1991年 | 117篇 |
1990年 | 79篇 |
1989年 | 92篇 |
1988年 | 59篇 |
1987年 | 65篇 |
1986年 | 39篇 |
1985年 | 20篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1954年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
利用广西北部湾经济区2004-2008年的土地利用变更数据,采用改进的TOPSIS方法对广西北部湾经济区的土地利用结构合理性、土地利用动态,以及土地利用类型相关性进行了分析. 相似文献
113.
In this paper,the structure of systematic and random errors in marine survey net are discussed in detail and the adjustment method for observations of marine survey net is studied,in which the rank-defect haracteristic is discovered first up to now.On the basis of the survey-line systematic error model,the formulae of the rank-defect adjustment model are deduced according to modern adjustment theory.An examle of calculations with really observed data is carried out to demonstrate the efficiency of this adjustment model.Moreover,it is proved that the semi-systematic error correction method used at present in marine gravimetry in China is a special case of the adjustment model presented in this paper. 相似文献
114.
115.
基于数字摄影的钢结构变形监测系统研究 总被引:3,自引:0,他引:3
讨论了基于数字摄影的钢结构变形监测系统研究所解决的主要问题,提出了相应的解决方法,并论述了整个系统的流程。 相似文献
116.
The crustal structure of Xiachayu-Gonghe geophysical profile in eastern Tibetan plateau is simulated with Bouguer anomaly corrected for sediments and lithosphere. The forward simulation shows that the thickness of upper crust in eastern Tibetan plateau is about 20 km, and the density is 2.78×103kg/m3. The bottom interface of middle crust changes from 30 km to 40 km, the density of middle crust is 2.89×103kg/m3. The materials with low density of 2.78 ×103kg/m3 exist in middle crust, and those with high density of 3.33 ×103kg/m3 exist at the bottom of middle crust between Wenquan and Tanggemu. The density is 3.10 ×103kg/m3 in lower crust. The shallowest depth of Moho interface is about 56 km, and the deepest one is about 74 km, the undulation of interface is large, the deep Moho is located in Xiachayu, Chayu, Nujiang, and Wenquan. The crustal density of eastern Tibetan plateau is larger than that of central section; the low velocity layers are located in middle crust and bottom in eastern Tibetan plateau and at the bottom of the upper crust in the central plateau. 相似文献
117.
An application of line simplification considering spatial knowledge is described. A method for identifying potential conflict regions, in order to avoid the self-intersection of generalized, lines, is also discussed. Further-more, a new progressive line simplification algorithm is presented. From the view point of spatial cognition, a spatial hierarchical structure is proposed, and its application to construction of spatial knowledge related to a line is explained. 相似文献
118.
In this paper, the structure of systematic and random errors in marine survey net are discussed in detail and the adjustment method for observations of marine survey net is studied, in which the rank-defect characteristic is discovered first up to now. On the basis of the survey-line systematic error model, the formulae of the rank-defect adjustment model are deduced according to modern adjustment theory. An example of calculations with really observed data is carried out to demonstrate the efficiency of this adjustment model. Moreover, it is proved that the semi-systematic error correction method used at present in marine gravimetry in China is a special case of the adjustment model presented in this paper. 相似文献
119.
Optimization of land use structure consists of economic and social and ecological optimization. Applying the minds of system engineering and principles of ecology, this paper presents such thoughts: the optimal forest-coverage rate calculated according to the reality of a district is set as main standard of ecological rationality in the district; through considering the value of ecosystem services of the land with GREEN equivalent (mainly cultivated land and grassland) and based on the rule, GREEN equivalent, this paper introduces the area conversion between woodland and cultivated land, also between woodland and grassland; this paper establishes a multi-dimension controlling model of optimization of land use structure. In addition, a multi-objective linear programming model for optimization of land use structure is designed. In the end, this paper tests and verifies this theory of ecological optimization, taking Qionghai city in Hainan Province as an example. 相似文献
120.
This paper presents the basic concepts and principles, data structure and high efficient spatial index for multi-resolution image database. The database is characterized by arrangement of multi-resource image data and seamless mosaic, distribution-based storage and management, integration with other spatial database software such as GeoStar and GeoGrid developed by Wuhan Technical University of Surveying and Mapping. 相似文献