全文获取类型
收费全文 | 3598篇 |
免费 | 210篇 |
国内免费 | 238篇 |
专业分类
测绘学 | 1826篇 |
大气科学 | 78篇 |
地球物理 | 664篇 |
地质学 | 659篇 |
海洋学 | 188篇 |
天文学 | 37篇 |
综合类 | 307篇 |
自然地理 | 287篇 |
出版年
2024年 | 5篇 |
2023年 | 23篇 |
2022年 | 49篇 |
2021年 | 74篇 |
2020年 | 83篇 |
2019年 | 76篇 |
2018年 | 59篇 |
2017年 | 131篇 |
2016年 | 118篇 |
2015年 | 154篇 |
2014年 | 172篇 |
2013年 | 275篇 |
2012年 | 242篇 |
2011年 | 222篇 |
2010年 | 174篇 |
2009年 | 217篇 |
2008年 | 279篇 |
2007年 | 275篇 |
2006年 | 262篇 |
2005年 | 204篇 |
2004年 | 204篇 |
2003年 | 162篇 |
2002年 | 133篇 |
2001年 | 112篇 |
2000年 | 93篇 |
1999年 | 51篇 |
1998年 | 51篇 |
1997年 | 30篇 |
1996年 | 23篇 |
1995年 | 22篇 |
1994年 | 14篇 |
1993年 | 14篇 |
1992年 | 5篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1980年 | 1篇 |
排序方式: 共有4046条查询结果,搜索用时 0 毫秒
51.
52.
53.
54.
一种TIN生成算法及其三维显示 总被引:11,自引:1,他引:11
基于三角网的数字高程模型可以逼真地表现地表形态。在Visual C 6.0集成开发环境中构建基于等高线数据的三角网,提高构网的速度和精度,利用0penGL完成基于TIN的三维地貌显示。 相似文献
55.
56.
程恩 《海洋通报(英文版)》2001,3(2)
A new method of coding and decoding in the system of underwater image transmission is introduced, including the rapid digital frequency synthesizer in multiple frequency shift keying,image data generator, image grayscale decoder with intelligent fuzzy algorithm, image restoration and display on microcomputer. 相似文献
57.
D. C. Mason I. J. Davenport R. A. Flather C. Gurney G. J. Robinson J. A. Smith 《Estuarine, Coastal and Shelf Science》2001,53(6):759
A sensitivity analysis of the waterline method of constructing a Digital Elevation Model (DEM) of an intertidal zone using remote sensing and hydrodynamic modelling is described. Variation in vertical height accuracy as a function of beach slope is investigated using a set of nine ERS Synthetic Aperture Radar (SAR) images of the Humber/Wash area on the English east coast acquired between 1992 and 1994. Waterlines from these images are heighted using a hydrodynamic tide-surge model and interpolated using block kriging. On 1:500 slope beaches, an average block height estimation standard deviation of 18–22 cm is achieved. This rises to 27 cm on 1:100 slope beaches, and 32 cm on 1:30 slope beaches. The average heighting error at different slopes is decomposed into components due to waterline heighting error, inadequate sensor resolution and interpolation inaccuracy. It is shown that, at 1:500 slope, waterline heighting error and interpolation inaccuracy are the main error sources, whilst at 1:30 slope, errors due to inadequate sensor resolution become dominant. The ability of the technique to generate intertidal DEMs for almost the entire coastal zone in a complete ERS SAR scene covering 100×100 km is demonstrated. 相似文献
58.
利用漳州港海域无围堰填海造地前后的水深测量数据,结合海域地质钻探、表层和柱状沉积物资料,用数字地形模型方法计算了该区海底的冲淤量,分析了冲淤变化及其影响因素,结果显示:(1)淤积主要发生在近岸海域,其主要原因是近岸3-10m厚的海底淤泥层在回填土的挤压和推移下发生形变,产生淤浅假象;另一个原因是回填时部分泥沙流失入海,淤积在近岸海域,致使淤积强度增大。(2)由近岸往外,淤积强度逐渐减弱,并过渡为产中刷状态。 相似文献
59.
60.
Darío R. Minkoff Mauricio Escapa Flix E. Ferramola Silvio D. Maraschín Jorge O. Pierini Gerardo M.E. Perillo Claudio Delrieux 《Estuarine, Coastal and Shelf Science》2006,69(3-4):403
The Bahía Blanca Estuary (38° 50′ S, and 62° 30′ W) presents salt marshes where interactions between the local flora (Sarcocornia perennis) and fauna (Chasmagnathus granulatus) generate some kind of salt pans that alter the normal water circulation and condition its flow and course towards tidal creeks. The crab–vegetation dynamics in the salt marsh presents variations that cannot be quantified in a reasonable period of time. The interaction between S. perennis plant and C. granulatus crab is based on simple laws, but its result is a complex biological mechanism that causes an erosive process on the salt marsh and favors the formation of tidal creeks. To study it, a Cellular Automata model is proposed, based on the laws deduced from the observation of these phenomena in the field, and then verified with measurable data within macroscale time units. Therefore, the objective of this article is to model how the interaction between C. granulatus and S. perennis modifies the landscape of the salt marsh and influences the path of tidal creeks. The model copies the basic laws that rule the problem based on purely biological factors.The Cellular Automata model proved capable of reproducing the effects of the interaction between plants and crabs in the salt marsh. A study of the water drainage of the basins showed that this interaction does indeed modify the development of tidal creeks. Model dynamics would likewise follow different laws, which would provide a different formula for the probability of patch dilation. The patch shape can be obtained changing the pattern that dilates. 相似文献