全文获取类型
收费全文 | 113篇 |
免费 | 43篇 |
国内免费 | 28篇 |
专业分类
测绘学 | 19篇 |
大气科学 | 36篇 |
地球物理 | 21篇 |
地质学 | 61篇 |
海洋学 | 13篇 |
综合类 | 14篇 |
自然地理 | 20篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 11篇 |
2021年 | 12篇 |
2020年 | 3篇 |
2019年 | 9篇 |
2018年 | 9篇 |
2017年 | 8篇 |
2016年 | 6篇 |
2015年 | 10篇 |
2014年 | 7篇 |
2013年 | 8篇 |
2012年 | 6篇 |
2011年 | 16篇 |
2010年 | 12篇 |
2009年 | 11篇 |
2008年 | 5篇 |
2007年 | 7篇 |
2006年 | 2篇 |
2005年 | 3篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1987年 | 1篇 |
排序方式: 共有184条查询结果,搜索用时 15 毫秒
81.
海湾是海洋和陆地相互作用和人类活动最强烈的区域,沉积物中重金属的含量和分布都受到人类活动的影响。为了探究钦州湾沉积物中重金属的含量水平、污染程度和可能来源,本研究分析了钦州湾表层沉积物中Cu、Pb、Zn、Cd、Cr、Hg和As的含量及空间分布,采用地质累计指数(Igeo)和潜在生态风险指数(PERI)定量分析了重金属的污染程度和生态风险,并利用自组织映射(SOM)和正定矩阵因子分解法(PMF)模型评估了重金属的可能来源。结果表明:钦州湾表层沉积物重金属中Zn的平均含量最高,Hg平均含量最低;除个别站位的Pb含量符合海洋沉积物质量第二类标准外,其他重金属含量均符合海洋沉积物质量第一类标准;Igeo结果表明钦州湾表层沉积物主要的污染元素为Pb、Hg和Cu;PERI结果表明Hg是钦州湾表层沉积物主要的生态风险元素。SOM和PMF模型结果表明钦州湾表层沉积物重金属主要受自然来源、农业活动、工业生产活动的共同影响,各来源的相对贡献率分别为39.65%、29.15%和31.20%。 相似文献
82.
应用地球化学元素、地球化学淋溶系数及环境温度指标,研究了北极阿拉斯加巴罗热融湖Ikroavik钻孔岩芯AB-32连续的高分辨环境记录。结合210Pb测年数据,指出巴罗地区气候、环境变化的历史状况是:1600~1735年为寒冷、干燥时期;1750~1830年,气候变暖、变湿;1830年出现明显的地球化学转折界限,1830~1994年,气候较湿润温暖。1969~1970年前后,巴罗地区有一变冷阶段。AB-32钻孔岩芯1830年左右表现的古地球化学特征与现代Ikroavik湖泊环境地球化学特征相吻合,并且和Elson泻湖AB-67沉积岩芯反映的气候环境变化基本一致。 相似文献
83.
快速城镇化背景下乡村旅游地文化日益受到冲击,并表现出衰落的现象已是客观不争的事实。紧跟新时期乡村振兴战略和文旅融合发展趋势,综合运用质性研究和空间计量方法,以苏州东山镇为例,探索了乡村旅游地文化胁迫类型、格局与机理,结果表明:① 乡村旅游地文化胁迫量表包含23个题项、5个维度,即“自然景观文化胁迫”“聚落景观文化胁迫”“生产生活文化胁迫”“人际交往文化胁迫”“精神仪式文化胁迫”;② 乡村文化胁迫空间多呈沿街、邻水分布,各维乡村文化胁迫空间分布差异较大。乡村文化胁迫空间总体上呈显著集聚,其中生产生活文化最易受到旅游开发胁迫而表现出空间受胁症状;③ 乡村文化胁迫空间具有多集核分级分布的核心-外围分布模式,且随着旅游开发程度的提高其空间集聚程度显著提升,各维乡村文化胁迫空间集聚特征差异较大,其中聚落景观文化胁迫具有“大聚集、小分散”的空间特征,且与总体最为类似;④ 乡村旅游地文化胁迫产生的原因可以归纳为个体和整体两个层面,个体层面的社会属性和观念认知差异,以及整体层面的基础条件、社会发展和政策宣传共同作用着乡村旅游地文化胁迫的产生和发展。 相似文献
84.
Effects of antecedent soil moisture on losses of rare earth elements and phosphorus in runoff 总被引:1,自引:1,他引:0
Lingqing Wang Tao Liang Weili Wang Chaosheng Zhang 《Environmental Earth Sciences》2012,66(8):2379-2385
The effects of antecedent soil moisture on losses of rare earth elements (REEs) and phosphorus (P) in runoff were evaluated through a simulated rainfall experiment at the rate of 83?mm?h?1. The results revealed that antecedent moisture was a significant factor affecting the amounts of REE and P losses. It was observed that most REEs and P transported with sediments in the runoff. There was a significant correlation between the total amounts of REE losses and those of P losses in the runoff. The optimal antecedent moisture for minimization of losses for REEs ranged from 10.19 to 11.17% and it was 10.91% for P. 相似文献
85.
鄂尔多斯盆地多种能源矿产分布特征与协同勘探 总被引:2,自引:0,他引:2
鄂尔多斯盆地富含油、气、煤、铀等多种能源矿产。多种能源矿产在空间上具有一定的分布规律和组合形式,在时序上具有较为一致的矿产富集和后期保存、改造时期,在成因上具有一定的成生关系。结合多能源矿产的成矿背景、成藏(矿)机理、赋存规律、勘探理论与实践等,基于经济效益最大化和勘探方法最优化原则,建立了鄂尔多斯盆地多种能源矿产的协同勘探模式,将盆地划分为7个协同勘探区,每一个勘探区以某一种或两种矿产为主探,兼探其他矿产。在协同勘探模式的基础上,针对不同协同勘探区,制定了相应的协同勘探方法,为多种能源矿产协同勘探的实施奠定了理论基础。 相似文献
86.
The existence of three well-defined tongue-shaped zones of swell dominance, termed as ‘swell pools’, in the Pacific, the Atlantic
and the Indian Oceans, was reported by Chen et al. (2002) using satellite data. In this paper, the ECMWF Re-analyses wind wave data, including wind speed, significant wave
height, averaged wave period and direction, are applied to verify the existence of these swell pools. The swell indices calculated
from wave height, wave age and correlation coefficient are used to identify swell events. The wave age swell index can be
more appropriately related to physical processes compared to the other two swell indices. Based on the ECMWF data the swell
pools in the Pacific and the Atlantic Oceans are confirmed, but the expected swell pool in the Indian Ocean is not pronounced.
The seasonal variations of global and hemispherical swell indices are investigated, and the argument that swells in the pools
seemed to originate mostly from the winter hemisphere is supported by the seasonal variation of the averaged wave direction.
The northward bending of the swell pools in the Pacific and the Atlantic Oceans in summer is not revealed by the ECMWF data.
The swell pool in the Indian Ocean and the summer northward bending of the swell pools in the Pacific and the Atlantic Oceans
need to be further verified by other datasets. 相似文献
87.
Jinhua Pan Xin Jiang Xiaojie Li Yizhou Cong Zhuangzhi Zhang Zhiling Li Weili Zhou Houwei Han Shiju Luo Guanpin Yang 《中国海洋大学学报(英文版)》2011,10(2):147-152
Seagrass restoration as part of ocean ecosystem protection has been launched for many years all over the world, but intensive
research on this subject in China has just begun in recent years. Seed broadcasting has been widely accepted as the most potentially
useful method for seagrass restoration over large areas. We examined the influence of key environmental factors on seed germination
to help promote eelgrass bed restoration. Under anoxic conditions, the influence of temperature and salinity on the germination
rate of eelgrass (Zostera marina L.) seeds was examined at different combinations of four temperatures (4, 9, 14, and 24°C) and nine salinities (5 to 45,
increment of 5). The effect of significant interaction of temperature and salinity on germination rate was observed (ANOVA)
(P<0.001). The highest germination rate (83.3 ± 3.5)% was reached in 8 weeks at 14°C and salinity 5. Higher temperature significantly
increased the germination rate at salinity 5 (P<0.001) during the whole observation period except for 24°C, while lower salinity significantly increased the germination
rate at 14°C (P<0.001). Although significant interaction was found between temperature and salinity (P<0.001), the influence of salinity was stronger than that of temperature for the germination of eelgrass seeds. These results
provide useful information for the propagation of artificial seedlings for seagrass restoration in China. 相似文献
88.
选取大同地震台记录的2010—2019年531个MS≥5.0地震事件,根据发震区域的不同对其波形走时残差进行分析,得到不同发震区域地震波形的平均走时残差。结果表明,日本、喜马拉雅地区地震波形的走时残差总体为负值,平均残差分别为-1.51 s、-0.70 s;斐济、中国台湾地区、南美洲西海岸地区大多为正值,平均残差为0.79 s、1.83 s、1.86 s。同时发现,在有干扰的情况下参考不同区域平均走时残差计算结果,通过判断实际初至震相与理论初至震相的位置关系,可以更好地开展初至波震相识别工作。 相似文献
89.
90.
Cai Lin Yang Liu Ronggen Jiang Jinmin Chen Baohong Chen Weili Wang Kaiwen Zhou Hui Lin 《海洋学报(英文版)》2022,41(11):12-22
Resource exploitation in the Clarion-Clipperton Zone (CCZ) is of major research interest worldwide, but its influence on the environment is poorly understood, especially due to the lack of baseline values for metals in the surrounding sediment. This work aimed to establish the baseline values of 17 metals (Ba, Ca, K, Mg, Mn, Na, Ag, As, B, Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn) using normalization, the cumulative frequency curve method considering a total of 172 samples taken from 8 multitube cores and 1 box sediment core collected in the western CCZ during the COMRA-45 cruise campaign from August to September 2017. The baseline values of the evaluated metals were as follows: 1 932 mg/kg for Ba, 29 512 mg/kg for Ca, 18 150 mg/kg for K, 17 120 mg/kg for Mg, 6 747 mg/kg for Mn, 28 546 mg/kg for Na, 0.571 mg/kg for Ag, 5.00 mg/kg for As, 94.4 mg/kg for B, 0.626 mg/kg for Cd, 104 mg/kg for Co, 76.1 mg/kg for Cr, 370 mg/kg for Cu, 0.028 mg/kg for Hg, 190 mg/kg for Ni, 27.5 mg/kg for Pb and 156 mg/kg for Zn. Our findings would fill the baseline value gap in the study area and further improve accuracy of environmental impact assessments on the impact of resource exploitation. 相似文献