全文获取类型
| 收费全文 | 922篇 |
| 免费 | 161篇 |
| 国内免费 | 267篇 |
专业分类
| 测绘学 | 343篇 |
| 大气科学 | 304篇 |
| 地球物理 | 118篇 |
| 地质学 | 275篇 |
| 海洋学 | 118篇 |
| 天文学 | 9篇 |
| 综合类 | 99篇 |
| 自然地理 | 84篇 |
出版年
| 2024年 | 1篇 |
| 2023年 | 13篇 |
| 2022年 | 29篇 |
| 2021年 | 46篇 |
| 2020年 | 43篇 |
| 2019年 | 38篇 |
| 2018年 | 39篇 |
| 2017年 | 60篇 |
| 2016年 | 50篇 |
| 2015年 | 49篇 |
| 2014年 | 68篇 |
| 2013年 | 74篇 |
| 2012年 | 83篇 |
| 2011年 | 77篇 |
| 2010年 | 61篇 |
| 2009年 | 65篇 |
| 2008年 | 63篇 |
| 2007年 | 73篇 |
| 2006年 | 86篇 |
| 2005年 | 64篇 |
| 2004年 | 56篇 |
| 2003年 | 34篇 |
| 2002年 | 30篇 |
| 2001年 | 30篇 |
| 2000年 | 21篇 |
| 1999年 | 19篇 |
| 1998年 | 16篇 |
| 1997年 | 17篇 |
| 1996年 | 13篇 |
| 1995年 | 7篇 |
| 1994年 | 8篇 |
| 1993年 | 4篇 |
| 1992年 | 5篇 |
| 1991年 | 2篇 |
| 1989年 | 1篇 |
| 1988年 | 2篇 |
| 1987年 | 2篇 |
| 1986年 | 1篇 |
排序方式： 共有1350条查询结果，搜索用时 15 毫秒
1.
New Earth observation missions and technologies are delivering large amounts of data. Processing this data requires developing and evaluating novel dimensionality reduction approaches to identify the most informative features for classification and regression tasks. Here we present an exhaustive evaluation of Guided Regularized Random Forest (GRRF), a feature selection method based on Random Forest. GRRF does not require fixing a priori the number of features to be selected or setting a threshold of the feature importance. Moreover, the use of regularization ensures that features selected by GRRF are non-redundant and representative. Our experiments based on various kinds of remote sensing images, show that GRRF selected features provides similar results to those obtained when using all the available features. However, the comparison between GRRF and standard random forest features shows substantial differences: in classification, the mean overall accuracy increases by almost 6% and, in regression, the decrease in RMSE almost reaches 2%. These results demonstrate the potential of GRRF for remote sensing image classification and regression. Especially in the context of increasingly large geodatabases that challenge the application of traditional methods. 相似文献
2.
从胶东所处的板块构造位置和区域控热构造入手,根据地热传导理论,对胶东温泉的地热属性进行分析研究,认为胶东半岛温泉地热属性为毗邻板块边缘高温地热带的板内中低温地热系统,它以偏高的大地热流值为地热背景,以局部控热构造聚敛的大地热流为热源,以地形高差影响和相应的水力压差作用为动力,入渗的大气降水被岩石中的热量加热,并沿断裂出露形成温泉地热水。根据山东半岛温泉地热属性的特点和地热水开发中所面临的问题,提出保持胶东温泉可持续开发的相关对策。 相似文献
3.
MAO Duan-qian ZHANG Jie BAO Hao-sheng 《中国地理科学(英文版)》2005,15(3):275-280
1IN T R O D U C T IO NAn image isa setofbelief,s ideasand impressionsthatapersonholdsaboutan object(KOTLER,1991).Similar-lydefinitionistheimage of a destinationas thesum ofbelief,sideasand impressionsthatpeoplehave ofa placeor destination(CROMPTON,1979;KO… 相似文献
4.
5.
6.
利用图像分形编码中定义域块和最小均方误差一一对应的特点，提出了1种基于分形编码的多姿态、表情的人脸图像检索方法。该方法将待检索图像分割为相同大小的值域块，然后将每一值域块按给定的定义域块进行分形编码，得到最小均方误差，计算该最小均方误差与图像库中最小均方误差的欧氏距离。将待检索图像所有值域块的欧氏距离求平均，此平均欧氏距离较小的几幅图像即为检索出的图像。实验证明该方法能够准确地检索出图像库中存储的同一人的不同姿态、表情的图像。 相似文献
7.
Lectotype optimization of offshore platforms is of particular importance in the concept design process. Lectotype optimization involves multiple objectives with uncertainty and so is a problem of multiple attribute decision making. To date, there have been few published works on this topic in the context of offshore engineering. This paper develops a framework and methodology for evaluation of offshore platform alternatives, where a fuzzy optimum model is proposed to integrate the influence of each objective in the criteria set, and a new weight-assessing method is developed to mimic the decision maker’s experience and preference based on complementary pairwise comparisons. A case study shows that the new framework and methodology is scientific, reasonable and easy to use in practice. 相似文献
8.
In this paper we review levels of net loss, what happens to the gear once it has been lost, and the resulting levels of ‘ghost catches’ made in passive net fisheries in the EU. We also consider ghost catches resulting from lost gear in other types of fisheries, and the extent to which the value of ghost catches has been quantified. We consider why fishing gear is lost, and profile common management responses. We present a cost benefit model to assess the relative cost effectiveness of different management measures, and suggest that gear retrieval programmes may provide less value for money than other management responses. 相似文献
9.
10.