全文获取类型
收费全文 | 1156篇 |
免费 | 181篇 |
国内免费 | 128篇 |
专业分类
电工技术 | 33篇 |
综合类 | 145篇 |
化学工业 | 149篇 |
金属工艺 | 8篇 |
机械仪表 | 36篇 |
建筑科学 | 199篇 |
矿业工程 | 95篇 |
能源动力 | 31篇 |
轻工业 | 7篇 |
水利工程 | 208篇 |
石油天然气 | 11篇 |
武器工业 | 3篇 |
无线电 | 53篇 |
一般工业技术 | 175篇 |
冶金工业 | 24篇 |
原子能技术 | 4篇 |
自动化技术 | 284篇 |
出版年
2024年 | 23篇 |
2023年 | 36篇 |
2022年 | 52篇 |
2021年 | 53篇 |
2020年 | 61篇 |
2019年 | 50篇 |
2018年 | 37篇 |
2017年 | 60篇 |
2016年 | 45篇 |
2015年 | 62篇 |
2014年 | 74篇 |
2013年 | 60篇 |
2012年 | 69篇 |
2011年 | 107篇 |
2010年 | 91篇 |
2009年 | 96篇 |
2008年 | 95篇 |
2007年 | 100篇 |
2006年 | 71篇 |
2005年 | 56篇 |
2004年 | 51篇 |
2003年 | 45篇 |
2002年 | 25篇 |
2001年 | 14篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1986年 | 2篇 |
1979年 | 2篇 |
排序方式: 共有1465条查询结果,搜索用时 15 毫秒
91.
无控制DEM匹配与匹配优化技术 总被引:2,自引:0,他引:2
针对三维自由表面匹配问题,实现基于LZD算法进行无控制DEM匹配,克服了控制点布设的困难。通过分析转换参数相关性和地形特征对匹配能力的影响,提出了地形平滑处理的技术,改善了LZD算法的匹配性能,并通过相关试验进行了验证。该技术还可应用于计算机视觉、模式识别、工业产品质量检测、医学影像等应用领域。 相似文献
92.
The presented work is part of a larger research program dealing with developing tools for coupling biogeochemical models in contaminated landscapes. The specific objective of this article is to provide researchers with a data porting tool to build hexagonal raster using information from a rectangular raster data (e.g. GIS format). This tool involves a computational algorithm and an open source software (written in C). The method of extending the reticulated functions defined on 2D networks is an essential key of this algorithm and can also be used for other purposes than data porting. The algorithm allows one to build the hexagonal raster with a cell size independent from the geometry of the rectangular raster. The extended function is a bi-cubic spline which can exactly reconstruct polynomials up to degree three in each variable. We validate the method by analyzing errors in some theoretical case studies followed by other studies with real terrain elevation data. We also introduce and briefly present an iterative water routing method and use it for validation on a case with concrete terrain data. 相似文献
93.
地形高程数据一般用二维深度图(range image)表示,如果直接显示为灰度图形式不直观,可视性差。本文针对OpenGL三维图形库提出了一种二维数字地形图转换为三维地形数据并建立相应数字高程模型的算法,实现了基于OpenGL的地形高程数据三维显示,并对晴雾天候下的地形视觉模型进行了仿真。 相似文献
94.
95.
针对A*算法在数字高程模型(DEM)路径规划中的低效问题,提出一种基于距离与坡度的改进A*寻路算法。该算法面向规则网格DEM,以距离和坡度作为路径搜索评估指标,设计新的评价函数,并以地表障碍评判路径的可通行性。在寻路过程中,根据实际场景DEM数据计算相匹配的参数,使得改进算法能自适应不同场景下DEM数据分辨率的变化;采用动态权值调整完备性函数和启发性函数对评价结果的影响,优化路径选择。仿真测试结果表明,改进算法能够通过参数调整适应DEM分辨率的变化,搜索出优化的路径,降低搜索时间,提高搜索效率。 相似文献
96.
Lakes in the Qinghai-Tibet Plateau are numerous and widely distributed, accounting for 41% and 57% of the total number and area of lakes in China, which are very important for the study of lakes in the whole country and even in the whole world. Remote sensing has been used to monitor the lake distribution for a long time, but optical remote sensing images are often obscured by clouds, from which it’s impossible to automatically extract complete lake boundaries. An automatic interpolation algorithm for lake boundary generation based on cloudy Landsat TM/OLI image and Shuttle Radar Topography Mission (SRTM) 30 m resolution Digital Elevation Model (DEM) is proposed. Firstly, supported by the platform of Google Earth Engine, the tier1 data of Landsat TM/OLI images are used to eliminate the effects of cloud, cloud shadow, snow and mountain area, based on the Pixel Quality Assessment (pixel_qa) attribute and SRTM 30 m DEM. Then, the Modified Normalized Difference Water Index (MNDWI) is calculated, and the Canny edge detection algorithm are used to obtain the known part of the lake boundary (L) in cloud-free areas. The possible lake areas are obtained by range filtering of DEM locally. At the same time, DEM is used to generate contours with an isometric interval of 1 m, and a series of contours surrounding the possible lake area are automatically screened out. The tree structure is established according to the inclusion relationship between contours. The leaf nodes are the innermost contours, which are recorded as inner contours (C1). Because the acquisition time of Landsat and DEM is different, with the lake expanding or shrinking, the lake water surface will rise or fall relative to the inner contour. Different methods of determining the outer contour (C2) are adopted. Subsequently, the slope-aspect relationship between the inner contour C1 and the outer contour C2 and the known part of the lake boundary L is established, and the unknown lake boundary points are interpolated. Finally, the nearest neighbor method is used to connect the known lake boundary points with the interpolated Lake boundary points to form a complete lake boundary. The extracted lake boundaries were validated by visual digitized lake boundaries from ZiYuan-3 image or cloud-free Landsat image on the near date. It is found that they are basically coincided, and the percentage of differences in length and area are -6.81%~9.4% and -2.11%~2.7% respectively. It shows that this method is very effective for automatic extraction of Lake boundary from cloudy Landsat TM/OLI images, and provides a new method for automatic extraction of long time series Lake boundary and its temporal and spatial variation analysis in the Qinghai-Tibet Plateau on GEE and other big data platforms. 相似文献
97.
从鞍部点的形态特征出发,利用移动窗口法预提取出符合地形结构的鞍部特征点,对DEM(Digital Elevation Model,数字高程模型)数据进行等高距分层以模拟出等高线地图的地貌特性,从而考查特征点与周围区域的拓扑关系,剔除未处于鞍部地区的伪特征点。实验结果表明,算法快速简便,所获取的鞍部点符合地貌认知。 相似文献
98.
99.
Non-stationary variogram models for geostatistical sampling optimisation: An empirical investigation using elevation data 总被引:1,自引:0,他引:1
A problem with use of the geostatistical Kriging error for optimal sampling design is that the design does not adapt locally to the character of spatial variation. This is because a stationary variogram or covariance function is a parameter of the geostatistical model. The objective of this paper was to investigate the utility of non-stationary geostatistics for optimal sampling design. First, a contour data set of Wiltshire was split into 25 equal sub-regions and a local variogram was predicted for each. These variograms were fitted with models and the coefficients used in Kriging to select optimal sample spacings for each sub-region. Large differences existed between the designs for the whole region (based on the global variogram) and for the sub-regions (based on the local variograms). Second, a segmentation approach was used to divide a digital terrain model into separate segments. Segment-based variograms were predicted and fitted with models. Optimal sample spacings were then determined for the whole region and for the sub-regions. It was demonstrated that the global design was inadequate, grossly over-sampling some segments while under-sampling others. 相似文献
100.
将小波多尺度分解和ROI应用于数字高程模型(DEM)的表面建模中,首先用非均匀B样条曲面进行数字高程模型地形表面建模,然后用小波多尺度的特征将地表曲面进行压缩和光顺处理.对复杂地表曲面,可能只对某些局部区域感兴趣,因此在小波多尺度分解过程中要结合感兴趣区域(ROI)的方法.本文阐述了地表曲面小波分解和ROI多分辨率表示的原理,给出了具体曲面的小波分解算法和实现结果,有效减少了曲面存储所需的空间并提高了曲面的光顺程度. 相似文献