全文获取类型
收费全文 | 2420篇 |
免费 | 56篇 |
国内免费 | 39篇 |
专业分类
测绘学 | 184篇 |
大气科学 | 41篇 |
地球物理 | 189篇 |
地质学 | 237篇 |
海洋学 | 28篇 |
天文学 | 4篇 |
综合类 | 43篇 |
自然地理 | 1789篇 |
出版年
2023年 | 14篇 |
2022年 | 85篇 |
2021年 | 64篇 |
2020年 | 88篇 |
2019年 | 90篇 |
2018年 | 98篇 |
2017年 | 101篇 |
2016年 | 96篇 |
2015年 | 75篇 |
2014年 | 79篇 |
2013年 | 242篇 |
2012年 | 198篇 |
2011年 | 83篇 |
2010年 | 52篇 |
2009年 | 84篇 |
2008年 | 82篇 |
2007年 | 112篇 |
2006年 | 97篇 |
2005年 | 90篇 |
2004年 | 81篇 |
2003年 | 72篇 |
2002年 | 72篇 |
2001年 | 37篇 |
2000年 | 52篇 |
1999年 | 61篇 |
1998年 | 55篇 |
1997年 | 29篇 |
1996年 | 33篇 |
1995年 | 27篇 |
1994年 | 24篇 |
1993年 | 16篇 |
1992年 | 21篇 |
1991年 | 14篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 18篇 |
1987年 | 12篇 |
1986年 | 16篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 10篇 |
1982年 | 4篇 |
排序方式: 共有2515条查询结果,搜索用时 62 毫秒
171.
Gertjan Dijkink 《GeoJournal》2000,51(1-2):65-71
The capital is the centre of the established order but it always had to accept a relatively uncontrollable world of individuals redefining urban space in their own way or pioneering new means of support. As their existence is both a political nuisance and a foreshadowing of institutional changes (sometimes revolutionary) of nation-wide importance, I call such ways of life political frontiers. One may wonder what will become of political frontiers in the information society (or postmodern society) that, apart from borderless, has been described as society without a centre as well. Actually information society is the prototype of a frontier society with self-responsible groups and individuals. However, capitals – even stripped of their governmental functions – may offer a symbolical environment (a condensation of space and time) that precisely satisfies the wants of those who wish to politicise a way of life. Niches for pioneering behaviour may get dispersed over a wider territory but new types of political activity will gravitate to the capital even if the capital's official political status has dwindled. 相似文献
172.
173.
174.
175.
Volcanic lightning, perhaps the most spectacular consequence of the electrification of volcanic plumes, has been implicated in the origin of life on Earth, and may also exist in other planetary atmospheres. Recent years have seen volcanic lightning detection used as part of a portfolio of developing techniques to monitor volcanic eruptions. Remote sensing measurement techniques have been used to monitor volcanic lightning, but surface observations of the atmospheric electric Potential Gradient (PG) and the charge carried on volcanic ash also show that many volcanic plumes, whilst not sufficiently electrified to produce lightning, have detectable electrification exceeding that of their surrounding environment. Electrification has only been observed associated with ash-rich explosive plumes, but there is little evidence that the composition of the ash is critical to its occurrence. Different conceptual theories for charge generation and separation in volcanic plumes have been developed to explain the disparate observations obtained, but the ash fragmentation mechanism appears to be a key parameter. It is unclear which mechanisms or combinations of electrification mechanisms dominate in different circumstances. Electrostatic forces play an important role in modulating the dry fall-out of ash from a volcanic plume. Beyond the local electrification of plumes, the higher stratospheric particle concentrations following a large explosive eruption may affect the global atmospheric electrical circuit. It is possible that this might present another, if minor, way by which large volcanic eruptions affect global climate. The direct hazard of volcanic lightning to communities is generally low compared to other aspects of volcanic activity. 相似文献
176.
177.
工程物探是各学科和地球物理学的交叉学科,是目前应用地球物理领域中的一个重要的分支,它以地球物理学的理论、方法和技术来研究和勘查各种地球物理场的变化,提取人类活动(工程)对地质体原有状态的影响,探测地下目的体,评价工程质量,为工程的选址、建设、施工质量及安全性做出评价。上海城市建设工程物探的应用和相应的方法技术及工作程序,可供非物探专业的工程技术人员参考和借鉴。 相似文献
178.
A Network Model for Dispersion of Communicable Diseases 总被引:3,自引:0,他引:3
The spread of communicable diseases through a population is an intrinsic spatial and temporal process. This paper presents an individual‐based analytical framework for modeling the spatial and temporal heterogeneity in the disease transmission. The framework specifies a network model structure and six associated parameters. These parameters describe the properties of nodes, the properties of links, and the topology of the network. Through this model structure and associated parameters, this framework allows the representation of discrete individuals, individualized interactions, and interaction patterns in a network of human contact. The explicit representation of the spatial distribution and mobility of individuals in particular facilitates the modeling of spatial heterogeneity in the disease transmission. 相似文献
179.
A multi-equation spatial econometric model,with application to EU manufacturing productivity growth 总被引:1,自引:0,他引:1
Bernard Fingleton 《Journal of Geographical Systems》2007,9(2):119-144
A multi-equation spatial econometric model is used to explain variations across EU regions in manufacturing productivity growth
based on recent theoretical developments in urban economics and economic geography. The paper shows that temporal and spatial
parameter homogeneity is an unrealistic assumption, contrary to what is typically assumed in the literature. Constraints are
imposed on parameters across time periods and between core and peripheral regions of the EU, with the significant loss of
fit providing overwhelming evidence of parameter heterogeneity, although the final model does highlight increasing returns
to scale, which is a central feature of contemporary theory.
相似文献
180.
高光谱影像数据预处理是构建高效的影像数据库以及实现地理目标成分信息反演与地理目标识别的基础。本文从反射率演算、光谱微分技术以及高光谱影像数据的降维处理等三个方面对高光谱影像数据预处理进行了研究。实现了基于高光谱影像的反射率反演算法,针对高光谱遥感数据影像分辨率比较低的现状,提出了直方图均衡化、色调平衡、对比度调整等影像处理算法,并给出了实验结果。 相似文献