全文获取类型
收费全文 | 304篇 |
免费 | 23篇 |
国内免费 | 30篇 |
专业分类
测绘学 | 87篇 |
大气科学 | 14篇 |
地球物理 | 30篇 |
地质学 | 114篇 |
海洋学 | 33篇 |
天文学 | 1篇 |
综合类 | 33篇 |
自然地理 | 45篇 |
出版年
2024年 | 2篇 |
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 7篇 |
2020年 | 15篇 |
2019年 | 18篇 |
2018年 | 10篇 |
2017年 | 18篇 |
2016年 | 14篇 |
2015年 | 10篇 |
2014年 | 15篇 |
2013年 | 24篇 |
2012年 | 11篇 |
2011年 | 22篇 |
2010年 | 18篇 |
2009年 | 18篇 |
2008年 | 29篇 |
2007年 | 29篇 |
2006年 | 15篇 |
2005年 | 20篇 |
2004年 | 12篇 |
2003年 | 8篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 6篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1991年 | 1篇 |
1988年 | 1篇 |
1983年 | 1篇 |
排序方式: 共有357条查询结果,搜索用时 15 毫秒
21.
22.
A fuzzy dynamic flood routing model (FDFRM) for natural channels is presented, wherein the flood wave can be approximated to a monoclinal wave. This study is based on modification of an earlier published work by the same authors, where the nature of the wave was of gravity type. Momentum equation of the dynamic wave model is replaced by a fuzzy rule based model, while retaining the continuity equation in its complete form. Hence, the FDFRM gets rid of the assumptions associated with the momentum equation. Also, it overcomes the necessity of calculating friction slope (Sf) in flood routing and hence the associated uncertainties are eliminated. The fuzzy rule based model is developed on an equation for wave velocity, which is obtained in terms of discontinuities in the gradient of flow parameters. The channel reach is divided into a number of approximately uniform sub‐reaches. Training set required for development of the fuzzy rule based model for each sub‐reach is obtained from discharge‐area relationship at its mean section. For highly heterogeneous sub‐reaches, optimized fuzzy rule based models are obtained by means of a neuro‐fuzzy algorithm. For demonstration, the FDFRM is applied to flood routing problems in a fictitious channel with single uniform reach, in a fictitious channel with two uniform sub‐reaches and also in a natural channel with a number of approximately uniform sub‐reaches. It is observed that in cases of the fictitious channels, the FDFRM outputs match well with those of an implicit numerical model (INM), which solves the dynamic wave equations using an implicit numerical scheme. For the natural channel, the FDFRM outputs are comparable to those of the HEC‐RAS model. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
23.
李留霖 《广东海洋大学学报》2004,24(2):28-32
行政赔偿因果关系的认定,直接关系到国家赔偿法效能的发挥.现实中,行政赔偿之所以陷入困境,其中一个重要原因是行政赔偿因果关系的认定缺乏标准.应从行政管理的规律出发,把握行政法律关系的特征,着眼于行政法未来的发展趋势,从充分发挥行政赔偿的内在功能入手,兼顾国家现实的赔偿能力及当前的法制人文环境,从理论上建立可供司法实践操作的行政赔偿因果关系认定规则. 相似文献
24.
25.
26.
提高自动气象站设备运行能力和观测数据的质量状况成为影响气象预测预报服务的准确性和气象事业发展的关键。然而中国现在业务运行的自动气象站设备并没有内置的故障检测装置,也没有完善的自检系统。但是气象要素(温湿压风雨)的变化往往是相互关联的,为了提高自动气象站数据质量,及时有效地判断设备故障。从大量观测数据试验结果进行研究,提出一种基于关联规则的故障综合诊断方法。通过使用Apriori挖掘算法,得到各气象要素及其变化量之间的强关联规则,通过实际观测数据验证2012年7月26日08时江西南昌站湿度传感器发生故障。 相似文献
27.
正1 Introduction The main production of Yabulai salt lake was original salt and recycled salt many years ago.After decade’s production,the sale lake resource is more and more deficient.Glauber's salt and magnesium salt are concentrated in brine now.It could affect the quality of the salt.In recent years,research had done much work to 相似文献
28.
有许多原则严格限制西方报章记者的表达自由。这些原则禁止记者在报道新闻时加上自己的评论、判断、解释或推论,以确保新闻的客观性、可靠性的公正性。客观的新闻工作者懂得新闻的概念,遵循严格的中立原则,避免经济、宗教、政治或民族偏见。尽管如此,报章的编辑、经营者和老板却能左右新闻。他们可以决定是否发表,发表多少以及在哪儿发表某条新闻,这一情形及其他因素对新闻的客观性构成威胁。 相似文献
29.
30.
Min Deng Jincai Huang Huimin Liu Luliang Tang Jianbo Tang 《International journal of geographical information science》2018,32(12):2337-2361
Detailed real-time road data are an important prerequisite for navigation and intelligent transportation systems. As accident-prone areas, road intersections play a critical role in route guidance and traffic management. Ubiquitous trajectory data have led to a recent surge in road map reconstruction. However, it is still challenging to automatically generate detailed structural models for road intersections, especially from low-frequency trajectory data. We propose a novel three-step approach to extract the structural and semantic information of road intersections from low-frequency trajectories. The spatial coverage of road intersections is first detected based on hotspot analysis and triangulation-based point clustering. Next, an improved hierarchical trajectory clustering algorithm is designed to adaptively extract the turning modes and traffic rules of road intersections. Finally, structural models are generated via K-segment fitting and common subsequence merging. Experimental results demonstrate that the proposed method can efficiently handle low-frequency, unstable trajectory data and accurately extract the structural and semantic features of road intersections. Therefore, the proposed method provides a promising solution for enriching and updating routable road data. 相似文献