全文获取类型
收费全文 | 1986篇 |
免费 | 139篇 |
国内免费 | 196篇 |
专业分类
测绘学 | 811篇 |
大气科学 | 361篇 |
地球物理 | 121篇 |
地质学 | 188篇 |
海洋学 | 85篇 |
天文学 | 21篇 |
综合类 | 272篇 |
自然地理 | 462篇 |
出版年
2024年 | 8篇 |
2023年 | 28篇 |
2022年 | 82篇 |
2021年 | 109篇 |
2020年 | 94篇 |
2019年 | 119篇 |
2018年 | 53篇 |
2017年 | 124篇 |
2016年 | 117篇 |
2015年 | 139篇 |
2014年 | 139篇 |
2013年 | 119篇 |
2012年 | 183篇 |
2011年 | 180篇 |
2010年 | 131篇 |
2009年 | 98篇 |
2008年 | 93篇 |
2007年 | 96篇 |
2006年 | 108篇 |
2005年 | 61篇 |
2004年 | 57篇 |
2003年 | 39篇 |
2002年 | 39篇 |
2001年 | 18篇 |
2000年 | 19篇 |
1999年 | 9篇 |
1998年 | 10篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有2321条查询结果,搜索用时 15 毫秒
951.
在构建交通服务功能模型和旅游效率评价指标基础上,综合运用熵权TOPSIS法、Bootstrap-DEA模型、双变量LISA和空间面板杜宾模型,探究2000-2016年云南省交通服务功能与旅游效率的空间关联特征,解析交通服务功能对旅游效率影响的空间效应及机理。结果表明:1)2000-2016年云南省交通服务功能整体呈上升态势,呈现典型“核心—边缘”空间格局;旅游效率总体水平呈增长趋势,在空间上呈集聚分布格局。2)云南省交通服务功能与旅游效率总体呈现空间集聚和依赖特征,双变量局部Moran散点主体落点呈现“高—高”和“低—低”空间聚类模式,表明评价交通服务功能与旅游效率关系时不能忽略空间效应。3)云南省交通服务功能对旅游效率具有明显的正向直接效应和空间溢出效应,佐证了交通是区域旅游效率增长不可或缺的先决条件;本地交通服务功能每提升1%,将会带动本地和邻近地区旅游效率分别增长0.2752%和0.1456%。4)经济实力、信息化水平、产业结构高级化、市场规模和对外开放度对本地旅游效率具有显著正向直接效应,经济实力、信息化水平、产业结构高级化与对外开放度对邻近地区旅游效率具有空间溢出效应。 相似文献
952.
Seagrass meadows are natural carbon storage hotspots at risk from global change threats, and their loss can result in the remineralization of soil carbon stocks and CO2 emissions fueling climate change. Here we used expert elicitation and empirical evidence to assess the risk of CO2 emissions from seagrass soils caused by multiple human-induced, biological and climate change threats. Judgments from 41 experts were synthesized into a seagrass CO2 emission risk score based on vulnerability factors (i.e., spatial scale, frequency, magnitude, resistance and recovery) to seagrass soil organic carbon stocks. Experts perceived that climate change threats (e.g., gradual ocean warming and increased storminess) have the highest risk for CO2 emissions at global spatial scales, while direct threats (i.e., dredging and building of a marina or jetty) have the largest CO2 emission risks at local spatial scales. A review of existing peer-reviewed literature showed a scarcity of studies assessing CO2 emissions following seagrass disturbance, but the limited empirical evidence partly confirmed the opinion of experts. The literature review indicated that direct and long-term disturbances have the greatest negative impact on soil carbon stocks per unit area, highlighting that immediate management actions after disturbances to recover the seagrass canopy can significantly reduce soil CO2 emissions. We conclude that further empirical evidence assessing global change threats on the seagrass carbon sink capacity is required to aid broader uptake of seagrass into blue carbon policy frameworks. The preliminary findings from this study can be used to estimate the potential risk of CO2 emissions from seagrass habitats under threat and guide nature-based solutions for climate change mitigation. 相似文献
953.
Globalization,Economic Restructuring,and Locational Trajectories of Software Firms in Shanghai 总被引:3,自引:0,他引:3
Yehua Dennis Wei Xiujing Bi Mingfeng Wang Yuemin Ning 《The Professional geographer》2016,68(2):211-226
Producer services are traditionally considered as place-bound and clustered in city centers to benefit from agglomeration effects. Such a pattern has been reshaped, however, by the decentralization of the service industry and the development of information and communication technology (ICT), especially for the software industry. This study investigates locational trajectories and underlying factors of software firms from 1990 to 2011 in Shanghai to detect intraurban location trajectories and spatial dynamics. We find that location of the software industry has changed from a monocentric pattern concentrated in the central city area toward a polycentric pattern with a relative decline of the core area. Using a conditional logit model, the study has found that government policies, accessibility, environmental conditions, agglomeration economies, and site characteristics are important determinants of location choice for software firms. In addition, the firm-level survey and in-depth interviews in Pudong Software Park show that government policy and planning, especially rent and tax incentives, have played a vital role in attracting software firms to locate in development zones. 相似文献
954.
An Interdisciplinary Methodology for the Characterization and Visualization of the Heritage of Roadway Corridors 下载免费PDF全文
Mar Loren‐Méndez Rafael Mata‐Olmo Rita Ruiz Daniel Pinzón‐Ayala 《Geographical review》2016,106(4):489-515
Roads, particularly since the advent of motorized traffic, have hugely impacted contemporary landscapes. Although their significance was noted in the 1980s, specific roadway‐heritage studies are scarce. Research in different disciplines has identified certain features of roads, but an integrated approach to roadway heritage or a consensus on what this constitutes are lacking. This article proposes an interdisciplinary methodology to assess roadway heritage. Roadways are interpreted within the framework of semantic openness that currently characterizes heritage studies, territory being the basic element of interpretation. Rather than a fragmented approach to conservation, the research defines integrated heritage configurations where natural, cultural, and historical features combine to produce a cohesive form of heritage. GIS (Geographical information systems) technology is used with an online database to assess the complexity of roadway heritage. ICT (Information and communications technology) strategies to raise public awareness are outlined. The methodology is applied to assess the historical N‐340 Mediterranean roadway corridor in Spain. 相似文献
955.
Siobhán Rachel McPhee 《Urban geography》2016,37(3):396-415
The city has become the context for a dialectical relationship not only between the global and the local but also between migrants and the host society. Whilst there is considerable work on migrant integration, integration is rarely examined from the perspective of the workplace, or from a geographic perspective, which problematizes the spatiality of migrant workers’ experiences. This article studies migrant workers in low-skilled jobs, with a focus on Temporary Service Sector Providers in catering, cleaning, and security, in order to understand how they negotiate their position in the city and are active agents of this negotiation. The study, based upon a survey of 60 migrants complemented by 20 in-depth interviews, questions how integration should be understood: in particular it suggests that—in some respects—integration may be difficult for all low-wage precarious workers, whether migrants or not. The study also highlights how migrant workers retain agency—the capacity to act, to make decisions, and appropriate certain places—even in challenging circumstances. 相似文献
956.
基于服务空间视角的长春市城市功能空间扩展研究 总被引:4,自引:3,他引:1
中国快速城镇化背景下城市功能空间迅速扩展引起了广泛关注。以长春市用地现状图和统计资料为数据源,借助ArcGIS和SPSS软件平台,引用多种模型基于服务空间视角研究了1995年以来长春市城市功能空间扩展的特征、效应与驱动机制。研究发现:① 1995~2013年长春市城市空间扩展迅速,扩展模式整体上以圈层式近域扩张为主,城市与服务空间整体的偏离问题始终存在,城市开发建设过程中服务空间明显滞后于城市空间的扩张。② 城市空间快速扩展产生了城市蔓延、功能空间失衡和城市功能空间的优化升级等效应。③ 行政因素和社会经济因素是城市空间扩展的主要驱动因素,回归模型结果表明人口城市化和人居环境水平的提高是城市功能空间本质内涵扩展的社会经济核心因素。 相似文献
957.
系统梳理了农村社区选址布局的相关研究进展,重新建构社区选址布局的基本原则并予以数学抽象。在此基础上引入泰森多边形和引力模型,以村庄发展潜力、社区最大服务半径为基本控制条件,依托Map Basic平台设计相应算法,分别建立农村社区选址模型和社区服务范围模型,构建了由计算机辅助实现的农村社区选址布局模型系统,并以青岛西海岸地区为实证地区,将模型系统应用于该区域农村社区选址布局规划实践中。研究结果表明,构建的模型系统适应性较强,通过村庄发展潜力与社区空间约束相关联,可有效提高农村社区选址布局规划的科学性与合理性,为当前农村社区建设提供一定的指导和借鉴。 相似文献
958.
网络社区交流中距离的作用——以新浪微博为例 总被引:2,自引:0,他引:2
信息通信技术的快速发展丰富了人们的交流方式,也逐步影响人们的社交网络。本文通过分析新浪微博用户在网络社区中与本地人/外地人、熟人/陌生人的交流差异,探讨空间距离与社会距离在网络社会空间中的作用。在问卷调研中,结合新浪微博用户的网络“痕迹”,较为可靠的获取南京成年人微博用户与本地人/外地人、熟人/陌生人在网络社区中的交流差异。研究表明:①在网络社区中,相较于外地人与陌生人,受访者更倾向与本地人以及熟人交流,网络社区中空间距离与关系距离的作用仍然存在;②受访者在网络社区中与本地人/外地人、熟人/陌生人的交流差异受社会经济属性、居住环境、微博使用频繁程度影响;③虽然理论上网络社区使得用户能够克服距离阻力,延伸其关系网络,但空间距离与关系距离的存在使得实际生活中的社会关系网络仍然扎根于用户在网络社区中的交流。 相似文献
959.
960.