全文获取类型
收费全文 | 155篇 |
免费 | 36篇 |
国内免费 | 9篇 |
专业分类
测绘学 | 58篇 |
大气科学 | 14篇 |
地球物理 | 51篇 |
地质学 | 22篇 |
海洋学 | 18篇 |
天文学 | 3篇 |
综合类 | 20篇 |
自然地理 | 14篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 7篇 |
2015年 | 6篇 |
2014年 | 11篇 |
2013年 | 6篇 |
2012年 | 11篇 |
2011年 | 4篇 |
2010年 | 5篇 |
2009年 | 10篇 |
2008年 | 15篇 |
2007年 | 12篇 |
2006年 | 14篇 |
2005年 | 10篇 |
2004年 | 9篇 |
2003年 | 4篇 |
2002年 | 7篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 2篇 |
排序方式: 共有200条查询结果,搜索用时 234 毫秒
101.
针对岩石力学试验中传统的声发射定位算法存在局限性,将灰狼算法(GWO)引入声发射定位研究中,该算法模仿了狼群的领导阶层与狩猎机制,用α、β、δ和ω 4种灰狼来模拟头狼领导,通过搜寻猎物、包围猎物和攻击猎物3个步骤实现目标的发现到捕获的全过程。在原始灰狼算法的基础上,针对其局部搜索能力欠佳的缺陷,修改收敛因子递减方式和淘汰最劣个体,提出基于种群记忆淘汰制的改进灰狼算法(BGWO)。基于预制裂隙岩石试件单轴压缩声发射试验结果,对比分析BGWO、GWO、引力搜索法(GSA)、Geiger算法、最小二乘法(LS)算法等5种定位算法的性能,发现改进后的BGWO算法在声发射定位搜索效率、搜索精度、稳定性和试验结果模拟方面效果优于其他算法。 相似文献
102.
准确获取气溶胶光学厚度对于气候变化研究和大气环境监测具有重要意义。通过波长插值和时空匹配方法,利用气溶胶自动观测站网(AERONET)观测的气溶胶光学厚度(AOD)对风云3A/中分辨率光谱成像仪(FY-3A/MERSI)、Terra(Aqua)/MODIS的C5.1(Collections 5.1)和C6(Collections 6)气溶胶光学厚度产品在中国区域的反演精度进行验证分析。结合一次发生在中国境内的沙尘天气与一次严重雾霾天气个例,分析上述卫星气溶胶光学厚度的分布特征。研究结果表明,(1)FY-3A/MERSI AOD的反演精度较高(R=0.887,RMSE=0.234),其值低于AERONET的观测值(Bias=-0.293)。(2)在不同的下垫面下,各种卫星暗像元算法AOD产品反演精度有差异,植被覆盖情况越好,反演精度越高,而植被很少的地区,即亮地表甚至没有反演值。(3)MODIS C5.1深蓝算法产品能在亮地表地区反演AOD,但效果不佳。MODIS C6中的深蓝算法产品在不同下垫面的反演精度都很高(RMSE为0.096-0.127)。(4)在不同季节的对比中,各种卫星AOD产品在夏季的反演精度最差,而反演最好的季节各有不同。(5)在一次沙尘天气污染与一次严重雾霾天气个例中,中国西部与北部区域,MODIS C6深蓝算法AOD的监测效果优于其他算法AOD;MERSI AOD产品在此区域的分布不连续。总体而言,MODIS C6 AOD分布比MODIS C5.1产品连续,MODIS 3 km产品在相同区域的AOD值高于其他产品。以上结论可为卫星AOD产品在中国区域的使用提供参考。 相似文献
103.
Based on the tropical cyclone (TC) observations in the western North Pacific from 2000 to 2008, this paper adopts the particle swarm optimization (PSO) algorithm of evolutionary computation to optimize one comprehensive classification rule, and apply the optimized classification rule to the forecasting of TC intensity change. In the process of the optimization, the strategy of hierarchical pruning has been adopted in the PSO algorithm to narrow the search area, and thus to enhance the local search ability, i.e. hierarchical PSO algorithm. The TC intensity classification rule involves core attributes including 12-HMWS, MPI, and Rainrate which play vital roles in TC intensity change. The testing accuracy using the new mined rule by hierarchical PSO algorithm reaches 89.6%. The current study shows that the novel classification method for TC intensity change analysis based on hierarchic PSO algorithm is not only easy to explain the source of rule core attributes, but also has great potential to improve the forecasting of TC intensity change. 相似文献
104.
105.
This research develops a clustering‐based location‐allocation method to the Capacitated Facility Location Problem (CFLP), which provides an approximate optimal solution to determine the location and coverage of a set of facilities to serve the demands of a large number of locations. The allocation is constrained by facility capacities – different facilities may have different capacities and the overall capacity may be inadequate to satisfy the total demands. This research transforms this special location‐allocation problem into a clustering model. The proposed approach has two parts: (1) the allocation of demands to facilities considering capacity constraints while minimizing the cost; and (2) the iterative optimization of facility locations using an adapted K‐means clustering method. The quality of a location‐allocation solution is measured using an objective function, which is the demand‐weighted distance from demand locations to their assigned facilities. The clustering‐based method is evaluated against an adapted Genetic Algorithm (GA) alternative, which integrates the allocation component as described above but uses GA operations to search for ‘optimal’ facility locations. Experiments and evaluations are carried out with various data sets (including both synthetic and real data). 相似文献
106.
107.
The details of a general multiblock partial least squares(PLS)algorithm based on one originallypresented by Wold et al.have been developed and are completely presented.The algorithm can handlemost types of relationships between the blocks and constitutes a significant advancement in the modelingof complex chemical systems.The algorithm has been programmed in FORTRAN and has been testedon two simulated multiblock problems,a three-block and a five-block problem.The algorithm combinesthe score vectors for all blocks predicting a particular block into a new block.This new block is used topredict the predicted block in a manner analogous to the two-block PLS.In a similar manner if one blockpredicts more than one other block,the score vectors of all predicted blocks are combined to form a newblock,which is then predicted by the predictor block as in the two-block PLS.Blocks that both predictand are predicted are treated in such a way that both of these roles can be taken into account whencalculating interblock relationships.The results of numerical simulations indicate that the computerprogram is operating properly and that the multiblock PLS produces meaningful and consistent results. 相似文献
108.
张钟澍 《成都信息工程学院学报》1992,(3)
Fuzzy聚类分析,是近年来在气象预报等很多科学领域中广泛应用的一种客观分析技术。本文根图的可迁闭包性质,探讨从模糊相似矩阵R中节点的可达性问题着手,生成相应的深度优先生成树(DFT)来完成聚类,从而得到一个时间复杂性为O(n~2)的快速Fuzzy聚类算法。 相似文献
109.
110.