全文获取类型
收费全文 | 10602篇 |
免费 | 1083篇 |
国内免费 | 1225篇 |
专业分类
测绘学 | 2295篇 |
大气科学 | 1073篇 |
地球物理 | 848篇 |
地质学 | 3238篇 |
海洋学 | 365篇 |
天文学 | 32篇 |
综合类 | 1092篇 |
自然地理 | 3967篇 |
出版年
2024年 | 38篇 |
2023年 | 124篇 |
2022年 | 337篇 |
2021年 | 422篇 |
2020年 | 450篇 |
2019年 | 482篇 |
2018年 | 349篇 |
2017年 | 508篇 |
2016年 | 556篇 |
2015年 | 555篇 |
2014年 | 678篇 |
2013年 | 799篇 |
2012年 | 726篇 |
2011年 | 756篇 |
2010年 | 623篇 |
2009年 | 583篇 |
2008年 | 544篇 |
2007年 | 555篇 |
2006年 | 563篇 |
2005年 | 476篇 |
2004年 | 471篇 |
2003年 | 388篇 |
2002年 | 343篇 |
2001年 | 318篇 |
2000年 | 240篇 |
1999年 | 203篇 |
1998年 | 175篇 |
1997年 | 150篇 |
1996年 | 99篇 |
1995年 | 93篇 |
1994年 | 69篇 |
1993年 | 59篇 |
1992年 | 44篇 |
1991年 | 24篇 |
1990年 | 31篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 11篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1954年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
基于特征价格模型的农村土地征收价格影响因素研究 总被引:3,自引:0,他引:3
在分析我国农村土地征收市场现状和农村土地征收价格影响因素的基础上,以天津市环城3个近郊区为例,收集市场案例256宗,选择影响因素13个,采用SPSS12.0进行多元回归,构建了两种形式的特征价格模型,重点分析了影响因素对价格的作用机制。 相似文献
72.
CHEN Luyao YUE Jianwei JIANG Weiguo LI Jing CHEN Yunhao 《地球空间信息科学学报》2007,10(4):299-302
The unceasing change problem of land information systems can be resolved through the refactoring and design pattern. To promote the implementation of design pattern and refactoring methods in developin... 相似文献
73.
Richard Lucas Katie MedcalfAlan Brown Peter BuntingJohanna Breyer Dan Clewley Steve KeyworthPhilippa Blackmore 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(1):81-102
The Phase 1 Survey is the most comprehensive and widely used national level map of semi-natural habitats in Wales. However, the survey was based largely on field survey and was conducted over several decades, before being completed in 1997. Given that resources for a repeat survey were limited, this study has used an object-orientated rule-based classification implemented within eCognition of multi-temporal satellite sensor data acquired between 2003 and 2006 to map semi-natural habitats and agricultural land across Wales, thereby allowing a progressive update of the Phase 1 Survey. The classification of objects to Phase 1 habitat classes was undertaken in two steps; firstly the landscape of Wales was divided into objects using orthorectified SPOT-5 High Resolution Geometric (HRG) reflectance data (10 m spatial resolution) and Land Parcel Information System (LPIS) boundaries. A rule-base was then developed to progressively discriminate and map the distribution of 105 sub-habitats across Wales based on time-series of SPOT HRG, Terra-1 Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Indian Remote Sensing Satellite (IRS) LISS-3 data, derived datasets (e.g., vegetation indices, fractional images) and ancillary information (e.g., topography). The rules coupled knowledge of ecology and the information content of these remote sensing data using a combination of thresholds, Boolean operations and fuzzy membership functions. A second rule-base was then developed to translate the more detailed sub-habitat classification to Phase 1 habitat classes. Indicative accuracies of the revised Phase 1 mapping, based on comparisons with the later Phase 2 survey (for selected habitats), were >80% overall and typically between 70% and 90% for many classes. Through this exercise, Wales has become the first country in Europe to produce a national map of habitats (as opposed to land cover) through object-orientated classification of satellite sensor data. Furthermore, the approach can be adapted to allow continual monitoring of the extent and condition of habitats and agricultural land. 相似文献
74.
Hani Abdallah Jean-Stéphane Bailly Nicolas Baghdadi Nicolas Lemarquand 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(6):833-844
Given that water resources are scarce and are strained by competing demands, it has become crucial to develop and improve techniques to observe the temporal and spatial variations in the inland water volume. Due to the lack of data and the heterogeneity of water level stations, remote sensing, and especially altimetry from space, appear as complementary techniques for water level monitoring. In addition to spatial resolution and sampling rates in space or time, one of the most relevant criteria for satellite altimetry on inland water is the accuracy of the elevation data. Here, the accuracy of ICESat LIDAR altimetry product is assessed over the Great Lakes in North America. The accuracy assessment method used in this paper emphasizes on autocorrelation in high temporal frequency ICESat measurements. It also considers uncertainties resulting from both in situ lake level reference data. A probabilistic upscaling process was developed. This process is based on several successive ICESat shots averaged in a spatial transect accounting for autocorrelation between successive shots. The method also applies pre-processing of the ICESat data with saturation correction of ICESat waveforms, spatial filtering to avoid measurement disturbance from the land–water transition effects on waveform saturation and data selection to avoid trends in water elevations across space. Initially this paper analyzes 237 collected ICESat transects, consistent with the available hydrometric ground stations for four of the Great Lakes. By adapting a geostatistical framework, a high frequency autocorrelation between successive shot elevation values was observed and then modeled for 45% of the 237 transects. The modeled autocorrelation was therefore used to estimate water elevations at the transect scale and the resulting uncertainty for the 117 transects without trend. This uncertainty was 8 times greater than the usual computed uncertainty, when no temporal correlation is taken into account. This temporal correlation, corresponding to approximately 11 consecutive ICESat shots, could be linked to low transmitted ICESat GLAS energy and to poor weather conditions. Assuming Gaussian uncertainties for both reference data and ICESat data upscaled at the transect scale, we derived GLAS deviations statistics by averaging the results at station and lake scales. An overall bias of −4.6 cm (underestimation) and an overall standard deviation of 11.6 cm were computed for all lakes. Results demonstrated the relevance of taking autocorrelation into account in satellite data uncertainty assesment. 相似文献
75.
使用数学形态学的"膨胀算子"对影像进行预处理,提出了一种改进的基于高斯拉普拉斯算子的面状特征提取和细化方法,并利用边界代数快速标注边界封闭的面状特征。在提取面状特征的基础上,利用奇异值分解算法,实现了基于面状质心的遥感影像匹配,进而完成精确配准。实验结果表明,与传统方法相比,此方法在速度与准确度上具有明显优势。 相似文献
76.
77.
78.
79.
土地整理规划设计是土地管理工作的重要组成部分,而测绘是土地整理规划设计的重要工作。利用GIS技术开发土地整理规划设计软件,提高土地整理规划设计自动化处理水平,提升测绘在国土资源服务中的保障能力。 相似文献
80.
融合区域分割和边缘信息的居民地提取方法 总被引:4,自引:0,他引:4
提出了一种集成边缘和区域分割信息的目标识别方法,其目的是在中小比例尺的航空影像中提取集团式居民地。在实际的航空影像上的实验表明,融合区域分割和边缘信息能够提高居民地提取的准确率。 相似文献