全文获取类型
收费全文 | 564篇 |
免费 | 215篇 |
国内免费 | 89篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 7篇 |
地球物理 | 123篇 |
地质学 | 293篇 |
海洋学 | 153篇 |
天文学 | 1篇 |
综合类 | 16篇 |
自然地理 | 268篇 |
出版年
2024年 | 3篇 |
2023年 | 12篇 |
2022年 | 24篇 |
2021年 | 17篇 |
2020年 | 17篇 |
2019年 | 19篇 |
2018年 | 26篇 |
2017年 | 22篇 |
2016年 | 30篇 |
2015年 | 26篇 |
2014年 | 36篇 |
2013年 | 30篇 |
2012年 | 16篇 |
2011年 | 36篇 |
2010年 | 23篇 |
2009年 | 51篇 |
2008年 | 32篇 |
2007年 | 62篇 |
2006年 | 46篇 |
2005年 | 37篇 |
2004年 | 30篇 |
2003年 | 29篇 |
2002年 | 32篇 |
2001年 | 23篇 |
2000年 | 26篇 |
1999年 | 18篇 |
1998年 | 18篇 |
1997年 | 10篇 |
1996年 | 17篇 |
1995年 | 24篇 |
1994年 | 18篇 |
1993年 | 19篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有868条查询结果,搜索用时 703 毫秒
121.
Long-term monitoring of wall paintings affected by soluble salts 总被引:1,自引:0,他引:1
Long-term monitoring of wall paintings in historical monuments aims at clarifying involved decay processes and at the same
time controlling effects of interventions for conservation. Monitored decay processes relate to the crystallisation of various
salts – particularly of nitronatrite and gypsum – from hygroscopic solutions accumulated in the zone of ground moisture. The
salts crystallise in response to climatic variations and other environmental changes. Measures for conservation such as protection
from water infiltration, reduction of heating temperature and reduction of surface salt accumulation cause a significant slow-down
but not a stop of decay. The particular dynamics and causes of remaining slow decay processes are described on three sites
in Switzerland: the convent church of Müstair, the crypt in the cathedral of Basel and the crypt in the Grossmünster church
of Zürich. 相似文献
122.
This paper presents an examination of the timescale of phase transition behaviour of a series of salts known to cause damage
to wall paintings and other cultural property. The rate of deliquescence and crystallisation of single salts (nitromagnesite
and halite) under different RH regimes, and the extent to which this was affected when mixed with other salts (niter, nitratite
and gypsum), was investigated. The study was conducted using simple conventional techniques (mass measurements over time)
and also using an innovative new method: timelapse video imaging with online data annotation. The results demonstrate the
synergy gained from combining video imaging with environmental data in reference to time in the study of salt phase changes:
where it revealed new information concerning the kinetics of deliquescence and crystallisation. The implications of these
results for the implementation of environmental control measures within historic buildings are discussed.
相似文献
Alison SawdyEmail: |
123.
新疆乌尊布拉克盐湖是我国目前少见的含钾硝酸盐型盐湖。文中根据资料和CK96—1钻孔剖面中(14)C年龄以及岩性的变化,粗略地探讨第四纪晚更新世末期大约4万年以来新疆乌尊布拉克盐湖沉积特征、成盐环境和大致年代。 相似文献
124.
125.
126.
127.
A significant criterion in evaluating disposal strategies for high-level nuclear waste is the assessment of the isolation capacity for the most radiotoxic radionuclides, the actinides. Important processes pertinent to potential mobilization from the waste forms, retention in secondary phases and migration of actinides in the geochemical environment of the near field of disposal locations are summarized. Criteria are formulated for assessing engineered barrier performance as a geochemical barrier for actinide long-term retention. 相似文献
128.
柴达木盆地盐湖对维系区域生态平衡、保障农业安全和国民经济发展具有重要的作用。受青藏高原气候暖湿化影响,盆地湖泊格局发生了一系列变化。为分析盆地盐湖变化特征,本文以小柴旦湖为例,基于长时间序列卫星数据,利用随机森林法提取盐湖水域范围并解构、评估“点—线—面”形态变化,同时构建矿化度指数表征盐湖资源禀赋。结果表明:(1) 1990—2022年小柴旦湖面积呈“缓减—缓增—快增”的阶段性变化特征,岸线长度呈阶段性变化(2016年后增长明显),湖泊质心总体向西北方向迁移,截止2022年湖泊质心累计迁移距离为2363.49 m。(2) 1990—2022年矿化度指数波动下降,呈“淡化”态势。(3)气象数据显示研究区年平均气温升高、年降水量增多、年潜在蒸散量下降,处于暖湿化轻度转型期,降水增多、蒸发下降、增温引起的冰雪融水增加综合叠加效应引起区域水资源增加,进而导致湖泊扩张和“淡化”。(4)小柴旦湖扩张和“淡化”对社会经济和生态平衡影响明显,一方面,影响湖区周边基础设施,近70 km2区域受淹没直接影响,包括德小高速公路、柳格高速公路部分路段;另一方面,作为资源型湖泊,小柴旦湖... 相似文献
129.
以内蒙古锡林郭勒盟苏尼特右旗的察干淖尔盐湖为研究对象,利用OSL(Optically Stimulated Luminescence)测年技术和DEM(Digital Elevation Model)数字高程模型,重建湖面波动历史,探讨湖泊形成与环境变化过程.通过对察干淖尔盐湖周边大量的野外考察,发现湖泊周围存在海拔高程为1020、978和973 m的三级古湖岸阶地,其OSL测年结果分别为29.2±1.3、18.4±0.8及8.2 8.0 ka.通过湖岸阶地高程恢复的上述3个时期的古湖面积分别为3600、500和400 km~2.与现今的干旱盐湖景观迥然不同. 相似文献
130.
The Trans Indus-Salt Range, located in northern Pakistan, is one of the most tectonically active fold-and-thrust belts and comprises three main regions: the Potwar-Salt Range, the Kohat-Surghar Range and the Bannu Basin-Khisor Range. Of these, the Bannu Basin is the least studied and only a handful of publically accessible datasets and publications are available. Recently made public 2D seismic profiles and well data from the Bannu Basin indicate the presence of salt as well as evidence for a main detachment surface which is Neoproterozoic in age. Our findings suggest that the Salt Range Formation could be the main detachment for the entire basin.Interpretation also shows a Miocene-Eocene basin-wide unconformity that marks the Himalayan orogenic event which separates the pre-Himalayan from the syn-Himalayan sedimentary units. On the basis of seismic reflection data, we conclude that the basin experienced three main tectonic settings. An early stage of pre-Himalayan passive tectonic environment is followed by the compressional Himalayan tectonics which resulted in uplifted areas sourcing the fluviatile fill of the subsided basin. During this time, sedimentation from the northern margin of the basin may have influenced the southward flow of salt. This is followed by a more recent stage of thrusting that produced folds and thrusts deforming all of the sedimentary units.Structural geometries suggest that prospective traps are developed mainly in the anticlines outlining the eastern and western boundaries of the Bannu Basin, as well as the southern zone of the basin. Furthermore, the presence of salt diapirism and transpression zones together with numerous oil seeps in and around the basin increase the probability of hydrocarbon accumulation and indicate great potential for future exploration. 相似文献