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排序方式: 共有2348条查询结果,搜索用时 15 毫秒
981.
为满足当前利用车载DGPS创建或更新道路信息的实际需求,研制了道路线形参数的计算方法。在此,鉴于车辆行驶线与道路中线之间存在着偏离,从理论上导出了不同道路线形下GPS数据的误差方程式以及连接各种线形的条件方程式。针对误差方程式中未知参数互不独立的情况,采取联合直线段与曲线段一并平差解算法。据此即可求出各段的线形参数并进行精度评定,最后通过算例验证了此方法的有效性与实用性。  相似文献   
982.
Delaunay三角网在大规模CORS基准站组网中的应用和研究   总被引:1,自引:0,他引:1  
连续运行参考系统(CORS)的核心技术——GPS网络实时动态定位(RTK)技术已经成为GPS高精度定位中一种重要技术,其定位精度与站间距离密切相关。在构建了站间距离和网络分布适中的Delaunay三角网后,探讨了基准站点删除与插入等网络局部更新以及参考站最优选择问题,提出了构网和确定流动站所在三角形的优化算法,实验证明该算法高效快捷、简便可靠。  相似文献   
983.
针对道路网综合时须保持道路网眼空间分布特征这一基本要求,在讨论道路网眼拓扑形式化描述的基础上提出了一种基于拓扑相似性的道路网综合模型。该模型通过制定道路网拓扑相似性评价指标来进行道路网综合方案选择,同时针对拓扑相似性相同的不同道路删除方案,进一步提出了利用道路形状加以评价的方法。结果表明,该模型原理正确,无论对于保持道路网眼空间分布还是形状特征都具有很好的效果。  相似文献   
984.
Geo-tagged travel photos on social networks often contain location data such as points of interest (POIs), and also users’ travel preferences. In this paper, we propose a hybrid ensemble learning method, BAyes-Knn, that predicts personalized tourist routes for travelers by mining their geographical preferences from these location-tagged data. Our method trains two types of base classifiers to jointly predict the next travel destination: (1) The K-nearest neighbor (KNN) classifier quantifies users’ location history, weather condition, temperature and seasonality and uses a feature-weighted distance model to predict a user’s personalized interests in an unvisited location. (2) A Bayes classifier introduces a smooth kernel function to estimate a-priori probabilities of features and then combines these probabilities to predict a user’s latent interests in a location. All the outcomes from these subclassifiers are merged into one final prediction result by using the Borda count voting method. We evaluated our method on geo-tagged Flickr photos and Beijing weather data collected from 1 January 2005 to 1 July 2016. The results demonstrated that our ensemble approach outperformed 12 other baseline models. In addition, the results showed that our framework has better prediction accuracy than do context-aware significant travel-sequence-patterns recommendations and frequent travel-sequence patterns.  相似文献   
985.
Spatial differentiation in forest transition was measured in terms of space transition and function transition using the exploratory spatial data analysis method (ESDA) and data from 2004—2014 for Zunyi city, Guizhou province, China. The validity of factors affecting forest transition was analyzed by constructing radial basis function neural networks (RBFNN) based on the data processing system (DPS). Our results will provide references for scientific understanding of the potential mechanism underlying forest transition in mountainous areas. We found that Global Moran’s I of space transition and function transition of forest land was 0.0336 and 0.2323, respectively. This suggests a significant positive correlation in spatial distribution of space transition and function transition of forest land, and significant spatial aggregation. The Global Moran’s I of function transition was higher than that of space transition, and the spatial aggregation characteristics of function transition were more significant than for space transition. The Global Moran’s I at each time period tended to increase, and the spatial aggregation degree of the function transition and space transition was further enhanced. Hot and cold spots of space transition of forest land stably evolved, suggesting a minor spatial difference in forest land among different administrative units at the county level. The number of hot spots at the county level in function transition increased. Hot spots were intensively distributed at the western edge and continuously distributed in the northeast. The space transition and function transition of forest land were both greatly influenced by urbanization rate and second and third industries. The development of urbanization and industrialization was the main factor driving forest transition, suggesting a positive role of economic growth on forest transition in mountainous areas. The development of urbanization and industrialization is an effective approach to forest transition in mountainous areas.  相似文献   
986.
近年来,暴雨内涝频繁发生,常引发严重的城市交通拥堵问题。本文利用自主开发的宏观交通模拟工具,模拟了上海市中心城区50年一遇和100年一遇暴雨强度情景下每条路段的小时交通量,通过计算道路饱和度,研究了不同强度暴雨内涝对中心城区高架出入口和重要道路拥挤程度的影响。结果表明:①100年一遇暴雨内涝对上海市中心城区道路交通服务能力影响显著,可导致7个高架道路出入口关闭,部分出入口严重拥堵;②暴雨内涝对道路拥堵状况影响的差异性明显,变拥挤路段占道路总里程的13.35%,其中一级道路的拥挤程度变化最为明显,如:大连路、武宁路,周家嘴路和长寿路等主要路段服务水平下降。  相似文献   
987.
Toponym matching, i.e. pairing strings that represent the same real-world location, is a fundamental problemfor several practical applications. The current state-of-the-art relies on string similarity metrics, either specifically developed for matching place names or integrated within methods that combine multiple metrics. However, these methods all rely on common sub-strings in order to establish similarity, and they do not effectively capture the character replacements involved in toponym changes due to transliterations or to changes in language and culture over time. In this article, we present a novel matching approach, leveraging a deep neural network to classify pairs of toponyms as either matching or nonmatching. The proposed network architecture uses recurrent nodes to build representations from the sequences of bytes that correspond to the strings that are to be matched. These representations are then combined and passed to feed-forward nodes, finally leading to a classification decision. We present the results of a wide-ranging evaluation on the performance of the proposed method, using a large dataset collected from the GeoNames gazetteer. These results show that the proposed method can significantly outperform individual similarity metrics from previous studies, as well as previous methods based on supervised machine learning for combining multiple metrics.  相似文献   
988.
Numerous rockfalls released during the 2010–2011 Canterbury earthquake sequence affected vital road sections for local commuters. We quantified rockfall fatality risk on two main routes by adapting a risk approach for roads originally developed for snow avalanche risk. We present results of the collective and individual fatality risks for traffic flow and waiting traffic. Waiting traffic scenarios particularly address the critical spatial‐temporal dynamics of risk, which should be acknowledged in operational risk management. Comparing our results with other risks commonly experienced in New Zealand indicates that local rockfall risk is close to tolerability thresholds and likely exceeds acceptable risk.  相似文献   
989.
王玥 《地理研究》2018,37(7):1435-1446
在过去的10年中,快速的零售业全球化进程已经在经济地理学研究中引起了强烈的关注。依托全球生产网络分析框架,通过阐述权利与价值在两个食品供应链(鲜奶和食用油)中发生的迁移与更迭,揭示出跨国零售企业进入中国市场前后,本土供应链发生的转型与升级。同时,就供应链转型所具有的五个普适性特征,包括集中化采购、专业批发商的涌现、物流与信息系统升级、执行企业标准和发展自有品牌,在选取的案例产品中进行分析与比较,以此来解释供应链重组过程中的影响因素。结果表明:应采用动态的视角来研究零售供应链中的权利与价值,以此才能更好地揭示新兴市场中供应链网络转型升级的复杂性和不均衡性。  相似文献   
990.
植被等效水厚度对路域生态环境的监测评估具有重要意义。本研究以湖南醴潭高速一段为研究对象,以地面实测光谱和等效水厚度以及PRO4SAIL模拟光谱和模拟等效水厚度为数据源,利用PRO4SAIL冠层模型模拟光谱与地面实测光谱建立12种常用水分指数,引入随机森林算法对水分指数与等效水厚度进行重要性分析,得到12种水分指数的重要性排序;利用调整R 2确定建立等效水厚度估算模型中输入水分指数的最佳个数;在优选水分指数基础上,以PRO4SAIL模拟光谱计算得到水分指数和等效水厚度为训练集,分别构建随机森林耦合偏最小二乘(RF-PLS)、随机森林耦合支持向量机(RF-SVM)和随机森林耦合遗传算法优化支持向量机(RF-GA-SVM)等效水估算模型,并用地面实测等效水厚度对估算模型进行精度验证与分析。结果表明:RF-SVM估算模型中输入重要性前9的水分指数(NDWI、NMDI、SRWI、SR、NDII、WI、DWI、MSI、SAVI)时,调整R 2最高,验证集决定系数为0.8877;RF-PLS和RF-GA-SVM估算模型中输入重要性前4的水分指数(NDWI、NMDI、SRWI、SR)时,调整R 2最高,验证集决定系数分别为0.8053、0.8952,其中RF-GA-SVM模型估算等效水厚度效果最佳,其精度满足路域植被等效水厚度监测要求。本文研究成果为等效水厚度估算提供一种有效且精确的方法,同时为发展基于高光谱遥感的路域环境监测提供重要支撑。  相似文献   
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