全文获取类型
| 收费全文 | 682篇 |
| 免费 | 47篇 |
| 国内免费 | 43篇 |
专业分类
| 测绘学 | 33篇 |
| 大气科学 | 35篇 |
| 地球物理 | 39篇 |
| 地质学 | 346篇 |
| 海洋学 | 112篇 |
| 综合类 | 82篇 |
| 自然地理 | 125篇 |
出版年
| 2024年 | 3篇 |
| 2023年 | 3篇 |
| 2022年 | 6篇 |
| 2021年 | 6篇 |
| 2020年 | 1篇 |
| 2019年 | 6篇 |
| 2018年 | 3篇 |
| 2017年 | 7篇 |
| 2016年 | 5篇 |
| 2015年 | 5篇 |
| 2014年 | 20篇 |
| 2013年 | 15篇 |
| 2012年 | 27篇 |
| 2011年 | 26篇 |
| 2010年 | 19篇 |
| 2009年 | 29篇 |
| 2008年 | 28篇 |
| 2007年 | 31篇 |
| 2006年 | 91篇 |
| 2005年 | 43篇 |
| 2004年 | 37篇 |
| 2003年 | 46篇 |
| 2002年 | 23篇 |
| 2001年 | 28篇 |
| 2000年 | 20篇 |
| 1999年 | 27篇 |
| 1998年 | 28篇 |
| 1997年 | 38篇 |
| 1996年 | 39篇 |
| 1995年 | 30篇 |
| 1994年 | 19篇 |
| 1993年 | 17篇 |
| 1992年 | 9篇 |
| 1991年 | 16篇 |
| 1990年 | 6篇 |
| 1989年 | 7篇 |
| 1984年 | 3篇 |
| 1983年 | 1篇 |
| 1982年 | 1篇 |
| 1973年 | 1篇 |
| 1972年 | 2篇 |
排序方式： 共有772条查询结果，搜索用时 15 毫秒
721.
722.
城市化进程与城市可持续发展 总被引：2，自引：0，他引：2
全球城市化在带动经济发展的同时也带来了一系列的问题,即所谓的“城市病”,实现城市可持续发展是解决这些问题的必由之路,在分析城市化现象带来的问题之后,讨论了实施城市可持续发展的可行性和必要性,并就如何实施我国城市可持续发展提出了一些建议。 相似文献
723.
724.
用卫星高光谱数据提取江西德兴铜矿矿山废水的pH值污染指标 总被引：3，自引：0，他引：3
在对德兴铜矿矿山废水的光谱特征深入分析研究的基础上,总结了不同类型水体(酸性水、碱性水以及河流水)的特征光谱,并利用地物谱特征开展矿山废水pH值污染指标提取研究。针对水体光谱反射率低、特征光谱不明显的特点,采用矿区卫星Hyperion高光谱数据,应用ISA算法和掩膜技术识别出水体分布并进一步与MNF变换有效结合,根据波段散点图进行不同pH值水体的有效分割。为矿山废水污染的诊断和监测提供了新技术和理论支撑。 相似文献
725.
727.
728.
In natural systems heavy metals are present in very low concentrations (less than micro-molar) , so precise measurement of the free metal ions is difficult. Recently, a new method has been developed called the Donnan membrane technique (DMT). Several heavy metals could be measured simultaneously using this method. Furthermore, all the metals did not interfere with each other, and the balance between the measured system and the surrounding condition could not be disturbed. Improvements were made according to the internal condition. The free heavy metal ion concentrations were measured in different systems using the improved method, and satisfied results have been obtained. 相似文献
729.
730.
Szegvi J sef Prokisch Per Marth Ba Kov s Zolt Gyi 《中国地球化学学报》2006,25(B08):195-195
The Soil Information and Monitoring System （TIM） is an independent subsystem of the integrated Environmental Information and Monitoring System in Hungary. Based on physiographical-soil-ecological units 1202 representative observation points were selected and exactly defined by geographical coordinates using GPS. The first sampling was done in 1992. Some soil parameters are measured every year, some others every 3 years or every 6 years depending on their changeability （stability）. Toxic element, heavy metal and rare earth element contents in soil samples were determined after hot and strong acid digestion by ICP-OES equipment. The rare earth elements were measured in TIM soil samples and some of them can be found in a relatively high amount, e.g. cerium and neodymium concentration are 3-4 times higher than the very often-measured copper concentration. Close correlation was found among some of the rare earth element concentrations. The Y-Yb correlation is the strongest, its r-value is higher than 0.95. The reason of difference among the yttrium concentrations of samples is not the deviation of ICP-OES measurement that is much smaller than the difference among the individual soil samples. Similar, close correlation was obtained between the soil yttrium and chromium concentration. The amount of chromium contamination can be calculated as the distance from the Y-Cr trend line. We call this method yttrium normalization. The principle of this method is described as follows： such elements than chromium and yttrium insist in the soil in a strongly bonded form. Therefore, in a non-contaminated area there is a close correlation between the yttrium and chromium concentrations. If the measured chromium concentration in a sample is not on the Cr-Y trend line than the distance it indicates the amount of antropogenic chromium. Contamination can be detected in that case of course if the contaminant does not contain yttrium. 相似文献