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981.
单木参数对当前的森林资源管理、生态研究以及生物多样性保护等具有重要意义。无人机立体影像数据与单木识别算法为单木参数的低成本、自动化获取提供了基础。现有研究表明,常用的基于局部最大值搜索的单木识别算法面对密集林分时存在严重的漏识别问题,影响了参数提取的精度,因此本文提出了顾及单木三维形态的无人机立体影像单木识别新算法。算法首先综合利用无人机立体影像的高程与RGB光谱信息,通过随机森林分类进行林冠区的提取;然后利用形态学的多层腐蚀、膨胀与连通区标记进行树冠相连单木的分离与树冠中心点的提取,从而实现单木自动化识别。本文选取内蒙古大兴安岭林区和四川王朗林区的4块样地进行验证,以目视解译数据为参考,分别与基于高程值的局部最大值搜索算法(算法A)、基于RGB光谱亮度值的局部最大值搜索算法(算法B)进行比较。结果显示:本文提出的算法在4个样地的平均F1-score为94.17%,与算法A和算法B相比分别提高了15.85%和9.37%;而对于密集样地,本文提出的算法在查全率上相比算法A和算法B分别提高51.79%和35.64%。结果表明本文提出的算法在不同林区均能够实现较好的单木识别效果,特别是能够有效避免密集林分下的漏识别问题,为基于无人机立体影像的单木识别研究提供了一种新的思路。 相似文献
982.
983.
2.5维数字地图既具有三维数字地图良好的表现效果,又具备数据量小、网上传输速度快的优点,满足了在现有的网络环境下对三维地图的快速浏览访问,在传统二维地图和真三维地图之间起到了很好的承上启下的作用。本文针对阜新市二维矢量数据和属性数据,利用3ds Max软件对研究区域建模并渲染成图,然后,在PhotoShop软件中进行图幅拼接,最后制作成瓦片地图与矢量图叠加发布,以便实现在Web端对2.5维电子地图的浏览、查询和空间分析等功能,并重点研究了基于OGC的WMTS标准和瓦片金字塔技术的标准化切图制作、发布、调用方法。 相似文献
984.
在地形可视性分析中,R3视域算法和参考面算法是两种重要的算法。在对两种算法的计算结果进行对比后,可以发现参考面算法的计算结果总要比R3算法的结果偏高。本文在此对比的基础上继续深入分析造成这种结果差异的本质原因,进一步解释了这种差异多表现在山体和沟壑等地形起伏较大的区域原因,并得出结论:这种结果差异不能作为两种算法精度相互评价的依据。 相似文献
985.
Compaction rates of sediments or volcaniclastic material are needed to reconstruct original thickness of a bed,which in turn is required to reconstruct subsidence rates,sea-level rise,or in the case of volcaniclastic,the location or direction of the eruption site.The knowledge of compaction rates can also aid in the reconstruction of deformed fossils.The known shape of deformed fossils can allow the determination of the compaction they experienced.Here we report the compaction rate in an early Permian volcanic tuff from Wuda,Inner Mongolia,determined from the deformation of standing tree fern stems of known anatomy.The compaction rate has been found to be 0.56 in this case,indicating that 44% of original thickness remains. 相似文献
986.
987.
The purpose of this study was to compare a number of state-of-the-art methods in airborne laser scanning (ALS) remote sensing with regards to their capacity to describe tree size inequality and other indicators related to forest structure. The indicators chosen were based on the analysis of the Lorenz curve: Gini coefficient (GC), Lorenz asymmetry (LA), the proportions of basal area (BALM) and stem density (NSLM) stocked above the mean quadratic diameter. Each method belonged to one of these estimation strategies: (A) estimating indicators directly; (B) estimating the whole Lorenz curve; or (C) estimating a complete tree list. Across these strategies, the most popular statistical methods for area-based approach (ABA) were used: regression, random forest (RF), and nearest neighbour imputation. The latter included distance metrics based on either RF (NN–RF) or most similar neighbour (MSN). In the case of tree list estimation, methods based on individual tree detection (ITD) and semi-ITD, both combined with MSN imputation, were also studied. The most accurate method was direct estimation by best subset regression, which obtained the lowest cross-validated coefficients of variation of their root mean squared error CV(RMSE) for most indicators: GC (16.80%), LA (8.76%), BALM (8.80%) and NSLM (14.60%). Similar figures [CV(RMSE) 16.09%, 10.49%, 10.93% and 14.07%, respectively] were obtained by MSN imputation of tree lists by ABA, a method that also showed a number of additional advantages, such as better distributing the residual variance along the predictive range. In light of our results, ITD approaches may be clearly inferior to ABA with regards to describing the structural properties related to tree size inequality in forested areas. 相似文献
988.
This study presents a hybrid framework for single tree detection from airborne laser scanning (ALS) data by integrating low-level image processing techniques into a high-level probabilistic framework. The proposed approach modeled tree crowns in a forest plot as a configuration of circular objects. We took advantage of low-level image processing techniques to generate candidate configurations from the canopy height model (CHM): the treetop positions were sampled within the over-extracted local maxima via local maxima filtering, and the crown sizes were derived from marker-controlled watershed segmentation using corresponding treetops as markers. The configuration containing the best possible set of detected tree objects was estimated by a global optimization solver. To achieve this, we introduced a Gibbs energy, which contains a data term that judges the fitness of the objects with respect to the data, and a prior term that prevents severe overlapping between tree crowns on the configuration space. The energy was then embedded into a Markov Chain Monte Carlo (MCMC) dynamics coupled with a simulated annealing to find its global minimum. In this research, we also proposed a Monte Carlo-based sampling method for parameter estimation. We tested the method on a temperate mature coniferous forest in Ontario, Canada and also on simulated coniferous forest plots with different degrees of crown overlap. The experimental results showed the effectiveness of our proposed method, which was capable of reducing the commission errors produced by local maxima filtering, thus increasing the overall detection accuracy by approximately 10% on all of the datasets. 相似文献
989.
比较CASS2008,R2V,EPS三种不同软件矢量化的优缺点 总被引:1,自引:0,他引:1
王晶 《测绘与空间地理信息》2013,36(7):194-195
简述了利用三种矢量化常用软件作业的简单操作和过程,并就各自优缺点做了比较。 相似文献
990.