全文获取类型
收费全文 | 283篇 |
免费 | 39篇 |
国内免费 | 67篇 |
专业分类
测绘学 | 24篇 |
大气科学 | 108篇 |
地球物理 | 42篇 |
地质学 | 131篇 |
海洋学 | 48篇 |
天文学 | 1篇 |
综合类 | 13篇 |
自然地理 | 22篇 |
出版年
2023年 | 5篇 |
2022年 | 8篇 |
2021年 | 9篇 |
2020年 | 7篇 |
2019年 | 9篇 |
2018年 | 8篇 |
2017年 | 9篇 |
2016年 | 7篇 |
2015年 | 10篇 |
2014年 | 13篇 |
2013年 | 13篇 |
2012年 | 16篇 |
2011年 | 11篇 |
2010年 | 10篇 |
2009年 | 9篇 |
2008年 | 14篇 |
2007年 | 12篇 |
2006年 | 8篇 |
2005年 | 8篇 |
2004年 | 3篇 |
2003年 | 12篇 |
2002年 | 8篇 |
2001年 | 10篇 |
2000年 | 18篇 |
1999年 | 9篇 |
1998年 | 12篇 |
1997年 | 15篇 |
1996年 | 14篇 |
1995年 | 16篇 |
1994年 | 13篇 |
1993年 | 10篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 12篇 |
1988年 | 6篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 7篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
排序方式: 共有389条查询结果,搜索用时 15 毫秒
101.
农业起源的研究具有很大有实现意义。通过对大量资源的研究分析,指出并论述了稻作起源地应具备的四个必要条件(即野生稻的古地理分布、适合的生态环境、对植物栽培性能及生态条件和农时物候的兴趣与了解、长期的人类存在和活动)和四个参考条件(包括稻作遗存、生产工具、语言学证据、民族学证据等),认为南岭地区具有这些条件,因而是我国稻作起源地一部分。 相似文献
102.
Investigated are effects of the total cloudiness and other factors on earth-atmosphere net radiation(EANR) and analyzed is its relation to other components and ground surface net radiation in the context of ERBE and ISCCP.Evidence suggests that planetary scale albedo and earth-atmosphere short wave absorption radiation have maximum effect on the net radiation under study,with the influence of cloud and latitude displayed predominantly through the two factors;OLR has relatively weak effect;the earth-atmosphere net radiation is well correlated with surface net radiation.Analysis is also performed of the geographic distribution of the earth-atmosphere net radiation throughout China,and the annual curve of the net radiation on a local basis is marked by high(low) value in summer(winter) with the impact of factors.including total cloudiness responsible largely for the shift of the months with maximum. 相似文献
103.
104.
105.
Urban heat island monitoring and analysis using a non-parametric model: A case study of Indianapolis 总被引:1,自引:0,他引:1
Umamaheshwaran Rajasekar Qihao Weng 《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(1):86-96
A procedure for the monitoring an urban heat island (UHI) was developed and tested over a selected location in the Midwestern United States. Nine counties in central Indiana were selected and their UHI patterns were modeled. Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) images taken in 2005 were used for the research. The images were sorted based on cloud cover over the study area. The resulting 94 day and night images were used for the modeling. The technique of process convolution was then applied to the images in order to characterize the UHIs. This process helped to characterize the LST data into a continuous surface and the UHI data into a series of Gaussian functions. The diurnal temperature profiles and UHI intensity attributes (minimum, maximum and magnitude) of the characterized images were analyzed for variations. Skin temperatures within any given image varied between 2–15 °C and 2–8 °C for the day and night images, respectively. The magnitude of the UHI varied from 1–5 °C and 1–3 °C over the daytime and nighttime images, respectively. Three dimensional (3-D) models of the day and night images were generated and visually explored for patterns through animation. A strong and clearly evident UHI was identified extending north of Marion County well into Hamilton County. This information coincides with the development and expansion of northern Marion County during the past few years in contrast to the southern part. To further explore these results, an Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) 2004 land use land cover (LULC) dataset was analyzed with respect to the characterized UHI. The areas with maximum heat signatures were found to have a strong correlation with impervious surfaces. The entire process of information extraction was automated in order to facilitate the mining of UHI patterns at a global scale. This research has proved to be promising approach for the modeling and mining of UHIs from large amount of remote sensing images. Furthermore, this research also aids in 3-D diachronic analysis. 相似文献
106.
Peter A. Taylor P-Y. Li Diane V. Michelangeli Jagruti Pathak Wensong Weng 《Boundary-Layer Meteorology》2007,125(2):305-328
A time and height dependent eddy diffusion model is used to investigate possible scenarios for the size distribution of dust
in the lower atmosphere of Mars. The dust is assumed to either have been advected from a distant source or to have originated
locally. In the former case, the atmosphere is assumed to initially contain dust particles with sizes following a modified
gamma distribution. Larger particles are deposited relatively rapidly while small particles are well mixed up to the maximum
height of the afternoon boundary layer and are deposited more slowly. In other cases, a parameterization of the dust source
at the surface is proposed. Model results show that smaller particles are rapidly mixed within the Martian boundary layer,
while larger particles (r > 10 μm) are concentrated near the ground with a stronger diurnal cycle. In all simulations we assume
that the initial concentration or surface source depend on a modified gamma function distribution. For small particles (cross-
sectional area weighted mean radius, reff = 1.6 μm) distributions retain essentially the same form, though with variations in the mean and variance of the area-weighted
radius, and the gamma function can be used to represent the particle size distribution reasonably well at most heights within
the boundary layer. In the case of a surface source of larger particles (mean radius 50 μm) the modified gamma function does
not fit the resulting particle size distribution. All results are normalised by a scaling factor that can be adjusted to correspond
to an optical depth for assumed particle optical scattering properties. 相似文献
107.
利用2003年10月北京地区PM10浓度流动观测资料和同期MODIS AOD(Aerosol Optical Depth)高分辨率遥感资料,采用卫星遥感地面观测变分订正处理方法,综合分析了北京地区PM10浓度的空间分布特征以及机动车排放的影响效应。动态观测试验结果表明:北京城区大部分为轻污染区, 北京近郊区PM10浓度高值区沿环路呈环状分布,其中北京西南部、南部和东北部污染较严重,北京城郊街区PM10的空间分布受机动车排放的影响较大。MODIS卫星遥感资料分析表明:北京城区及近郊区AOD值较远郊区高得多,AOD空间分布场中存在虚假高值区,AOD非均匀分布特征不明显。采取点面结合综合观测研究思路,运用卫星遥感地面观测综合变分分析方法,可以取得客观订正的显著效果。经地面实测PM10浓度变分订正后的AOD变分场可以较高分辨率信息描述北京地区AOD的非均匀分布特征,弥补地面PM10浓度观测的缺陷。 相似文献
108.
109.
110.
应用TOVS资料变分分析技术增加青藏高原地区摸式初始场信息 总被引:12,自引:1,他引:11
首次在测站稀少的高原地区引入经变分技术处理的 TOVS卫星资料 ,通过动力诊断探讨了解决高原地区测站少、数值预报模式初始场信息误差大的技术关键问题 ,提出了采用TOVS反演资料在高原地区增加模式初始场信息的构思 ,并应用变分法处理 TOVS反演资料 ,显著地提高了高原初始场信息的可靠性 ;并从动力诊断分析角度 ,进一步证实了 TOVS反演资料的应用有利于提高高原动力系统特征的描述能力 ,并显著改善水汽输送通道分布及其层结稳定度等有关初始场信息的客观性 相似文献