全文获取类型
收费全文 | 316篇 |
免费 | 19篇 |
国内免费 | 24篇 |
专业分类
测绘学 | 38篇 |
大气科学 | 17篇 |
地球物理 | 41篇 |
地质学 | 49篇 |
海洋学 | 26篇 |
天文学 | 33篇 |
综合类 | 30篇 |
自然地理 | 125篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 20篇 |
2021年 | 14篇 |
2020年 | 20篇 |
2019年 | 20篇 |
2018年 | 13篇 |
2017年 | 14篇 |
2016年 | 12篇 |
2015年 | 14篇 |
2014年 | 16篇 |
2013年 | 18篇 |
2012年 | 10篇 |
2011年 | 18篇 |
2010年 | 15篇 |
2009年 | 14篇 |
2008年 | 11篇 |
2007年 | 13篇 |
2006年 | 22篇 |
2005年 | 21篇 |
2004年 | 11篇 |
2003年 | 9篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 9篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
排序方式: 共有359条查询结果,搜索用时 31 毫秒
231.
Ahmadi Nejad Masouleh Fatemeh 《GeoJournal》2005,64(3):153-162
Rural urban migration can often result in decreased agricultural output in countries with scarce land resources. It also can
hasten the socio-economic problems associated with the overcrowded cities of the developing world. As only 10% of Iran is
arable it is particularly vulnerable to threats to food security and self-sufficiency. This paper examines the daily flow
of villagers to a major city near the vital staple crop producing rural district of Lakan, where out-migration is already
occurring. Although most discussions of daily travel to cities is typically relegated to commuting, this paper aims to analyze
travel for the purpose of access to a variety of facilities and services that villages in the rural district of Lakan lack
including secondary schools, post offices, banks, and even telephones and newspaper stands. The paper emphasizes that daily
journeys make permanent moves to the city more likely because of the major inconvenience that results from the scarcity of
basic facilities within Lakan villages. Travel to a distant city for staple foods at grocery stores or for access to secondary
schools, for example, could intensify future out-migration because the heavy inconvenience of constant travel might eventually
outweigh the benefits of maintaining residency in villages. The paper utilizes information about daily travel to Rasht to
recommend various government construction projects and initiatives to improve the quality of life for villagers and avert
future rural–urban migration and the reduction in staple crop production that might result. 相似文献
232.
233.
中国危险废物处理处置技术现状和结构分析 总被引:3,自引:0,他引:3
在介绍危险性废物的概念,种类等基础上,对我国危险性危险性废物的处理处置现状进行了分析,并对废物的产生,处置结构和废物流等进行了评价,提出了未来我国危险性废物处理处置的规划方案。 相似文献
234.
Edward R. Valstar Rob G. H. H. Nelissen Johan H. C. Reiber Piet M. Rozing 《ISPRS Journal of Photogrammetry and Remote Sensing》2002,56(5-6)
Roentgen stereophotogrammetry is the most accurate Roentgen technique for three-dimensional assessment of micromotion of orthopaedic implants. The reported accuracy of Roentgen Stereophotogrammetric Analysis (RSA) ranges between 0.05 and 0.5 mm for translations and between 0.15° and 1.15° for rotations. Because of the high accuracy of RSA, small patient groups are in general sufficient to study the effect on prosthetic fixation due to changes in implant design, addition of coatings, or new bone cements. By assessing micromotion of a prosthesis in a short-term (i.e. 2 years) clinical RSA study, a prediction can be made on the chance of long-term (i.e. 10 years) loosening of the prosthesis. Therefore, RSA is an important measurement tool to screen new developments in prosthetic design, and to prevent large groups of patients from being exposed to potentially inferior designs.In this article, the basics of the RSA technique are explained, and the importance of clinical RSA studies is illustrated with two examples of clinical RSA studies which RSA delivered very valuable information. Thereafter, two recent developments in RSA that have been implemented at Leiden University Medical Center are presented: digital automated measurements in RSA radiographs and model-based RSA. 相似文献
235.
R. Calow G. Gademann G. Krell R. Mecke B. Michaelis N. Riefenstahl M. Walke 《ISPRS Journal of Photogrammetry and Remote Sensing》2002,56(5-6)
The correct positioning of the patient is an important demand in radiotherapy. Optical measurements seem appropriate, but special requirements of speed and accuracy must be met. A new photogrammetric system that captures patient surface data in real-time is introduced. It allows reproducible patient set-up, and monitors the patient's position during irradiation even when the patient is moving. It consists of two cameras and one projector and is based on the photogrammetric evaluation of stereo image pairs by projecting white light fringes onto the patient's body.The raw data of the 3D measurement is a sequence of point clouds. It can be evaluated together with other data modes common in radiotherapy for diagnosis and treatment planning. The system can be used as an additional verification tool for the correct positioning of the patient, and completely new applications emerge. 相似文献
236.
Christina R. Ergler Sarah Lovell Alison Watkins Christine Milligan Lee Thompson Daniel J. Exeter Robin Kearns 《New Zealand geographer》2017,73(3):205-217
Health geography in Aotearoa New Zealand (NZ) has had a major impact on international sub‐disciplinary debates. It is timely to celebrate our domestic health geography achievements and alert ourselves to the challenges ahead. This reflection article provides a brief overview of Aotearoa NZ's maturing health geography community and includes the reflections of a panel discussion held during the bi‐annual NZ Geographical Society conference in 2016. We argue that the eclectism of health geography in NZ and beyond is both the sub‐discipline's major strength and challenge. 相似文献
237.
研究了闽东南麦饭石特征及功能特性,探讨了闽东南麦饭石在味精废水,养鳗池水水质净化处理方面的应用前景。 相似文献
238.
对近年来包括本校海洋药物与食品研究所在内的研究机构在医疗材料上的研究提出综述报导。内容分4部分:高分子材料,生物材料,高分子材料和生物材料的复合物以及中草药。 相似文献
239.
目前如何根据用户需求以及时空制约条件合理安排就医出行,在海量的医疗机构中实现就医地点的合理推荐是人们的迫切需求。区别于常见的个性化医疗信息推荐方法,本文综合考虑医疗机构的实时资源规模、医疗用户的个性化需求以及前往机构的时空制约,提出一种面向就医地点推荐的个人时空可达性分析方法,并将方法运用于居民的就医出行场景中,实现就医地点的有效推荐。以济南市为研究区域,借助从高德地图API以及医疗健康网站中获取的地理信息数据与医疗机构资源数据,在不同用户、时间和地理位置的情境下,设置2处高校图书馆、2处居民点以及2处大型交通站共6个场景检验方法的有效性。实验表明,本文提出的个人时空可达性方法,能够有效度量医疗用户个体至就医地点间的可达程度,可解决不同时空情境下的就医地点推荐问题,同时也为相关智慧医疗技术的功能建设提供方法支撑,具有良好的应用前景。 相似文献
240.
长春市公共服务设施空间与居住空间格局特征 总被引:1,自引:1,他引:0
基于长春市790个居住小区、178所小学、301家社区医院、1681个公交站点等空间数据,引用核密度估计、Riley's K函数、同位区位商等分析方法,对公共服务设施空间与居住空间的形态格局、集聚特性、“临近性”关系等进行了定量分析。研究发现:首先,公共服务设施空间与居住空间分布的形态格局差异显著,同时也表现出较高的相关性,“核心—外围”网点数量的分布特征趋同性与分异性并存;其次,公共服务设施空间与居住空间均呈现出显著的集聚特征,但集聚的规模与强度差异明显,二者空间分布的协调性程度仍需提高;第三,从分布的空间关系来看,居住小区具有较为明显的“临近”公共服务设施布局的倾向,但反之不明显,整体呈现出空间格局的“非对称性”特征。 相似文献