首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   258篇
  免费   42篇
  国内免费   73篇
大气科学   2篇
地球物理   99篇
地质学   236篇
综合类   8篇
自然地理   28篇
  2024年   5篇
  2023年   8篇
  2022年   11篇
  2021年   20篇
  2020年   18篇
  2019年   16篇
  2018年   11篇
  2017年   12篇
  2016年   11篇
  2015年   9篇
  2014年   14篇
  2013年   24篇
  2012年   8篇
  2011年   16篇
  2010年   13篇
  2009年   10篇
  2008年   14篇
  2007年   17篇
  2006年   16篇
  2005年   5篇
  2004年   9篇
  2003年   7篇
  2002年   6篇
  2001年   15篇
  2000年   18篇
  1999年   20篇
  1998年   11篇
  1997年   7篇
  1996年   7篇
  1995年   5篇
  1994年   3篇
  1993年   2篇
  1992年   1篇
  1991年   1篇
  1989年   1篇
  1988年   2篇
排序方式: 共有373条查询结果,搜索用时 328 毫秒
171.
高会  郝远平 《地下水》2011,(6):10-11
通过对渭南地下热水水化学特征的分析,对比研究不同水化学成分之间的关系,结合研究区岩性及矿物性质,全面的分析了各热水样所经历的各种水化学作用及主控作用.研究表明:渭南不同区域地下热水水化学类型存在较大差异,不同水样所经历的水化学作用亦差别较大,除经历不同程度的溶滤作用与阳离子交替作用外各具特征,指示地下热水赋存环境存在较...  相似文献   
172.
张涛 《山东地质》2011,(12):11-16
对胶东半岛出露的14处温泉的水化学特征、同位素特征进行了分析,得出胶东半岛温泉水的来源主要为大气降水补给、海水补给,年龄以现代水为主。胶东半岛温泉水与围岩矿物未达到完全平衡,不适宜用Na,K,Mg地热温标,玉髓的地热温标显示胶东半岛温泉热储温度在81.26~108.93℃之间。对下一步胶东半岛的温泉地热勘查、开发利用具有指导意义。  相似文献   
173.
对胶东半岛出露的14处温泉的水化学特征、同位素特征进行了分析,得出胶东半岛温泉水的来源主要为大气降水补给、海水补给,年龄以现代水为主。胶东半岛温泉水与围岩矿物未达到完全平衡,不适宜用Na,K,Mg地热温标,玉髓的地热温标显示胶东半岛温泉热储温度在81.26~108.93℃之间。对下一步胶东半岛的温泉地热勘查、开发利用具有指导意义。  相似文献   
174.
Solute and runoff fluxes from two adjacent alpine streams (one glacial and one non‐glacial) were investigated to determine how the inorganic solute chemistry of runoff responded to seasonal and interannual changes in runoff sources and volume, and to differences in physical catchment properties. Intercatchment differences in solute composition were primarily controlled by differences in catchment geology and the presence of soils, whereas differences in total solute fluxes were largely dependent on specific discharge. The glacial stream catchment had higher chemical denudation rates due to the high rates of flushing (higher specific discharge). The non‐glacial Bow River had higher overall concentrations of solutes despite the greater prevalence of more resistant lithologies in this catchment. This is likely the result of both longer average water–rock contact times, and a greater supply of protons from organic soils and/or pyrite oxidation. Increases in snowpack depth/snowmelt runoff reduced the retention of nitrate in the Bow River catchment (i.e. increased nitrate export), probably by reducing net biological uptake, or by reducing the proportion of runoff that had contact with biologically active soil horizons that tend to remove nitrate. The two streams exhibited opposite solute flux responses to climate perturbations over three melt seasons (1998, 1999, and 2000). The 1998 El Niño event resulted in an unusually thin winter snowpack, and increased runoff and solute fluxes from the glacial catchment, but decreased fluxes from the Bow River catchment. Solute fluxes in the Bow River increased proportionally to discharge, indicating that increased snowmelt runoff in this catchment resulted in a proportional increase in weathering rates. In contrast, the proportional variation in solute flux in the glacial stream was only ∼70–80% of the variation in water flux. This suggests that increased ablation of glacier ice and the development of subglacial channels during the 1998 El Niño year apparently reduced the average water–rock contact time in the glacial catchment relative to seasons when the subglacial drainage system was primarily distributed in character. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
175.
The seasonal evolution in the hydrochemistry of four types of wetland (pond, ice wedge trough, wet meadow and mesic site) was studied in a 0·5 km2 wetland complex in the Canadian High Arctic on the Fosheim Peninsula, Ellesmere Island. In the spring, a large influx of overland runoff from snowmelt quickly flushed away the solutes of the ice stored on the wetland surface over the winter, and homogenized the hydrochemistry across the entire wetland complex. As the surface flow receded, various wetland patches became hydrologically disconnected and their hydrochemical characteristics evolved differently. Although underlain by marine sediments and saline permafrost, solute concentrations in much of the wetland complex remained dilute compared with many Arctic wetlands. Through continued evaporation, melting of ground ice and localized thermokarst activities, the hydrochemistry of different wetland types acquired their distinctive characteristics as the summer progressed. This study demonstrates that large diversity in wetland hydrochemistry occurs even within a limited area, indicating the need to caution against generalizations based on limited spatial and temporal samples. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
176.
Abstract

Studies of the chemical composition of snowpack and stream water were carried out in a catchment having an area of 53km2 (31°03′-30°55′N and 78°40′-78°51′E) in the Garhwal Himalaya, India. The dominant ions in the snowpack and stream water were Ca2+, Na+, NO? 3, SO2- 4 and HCO? 3. Solute patterns in the snowpack show preferential elution. Investigation of the chemical composition of stream water shows that meltwater changes its composition substantially as it passes through soil pathways to the stream. The groundwater flushing perhaps controls the chemical composition of meltwater in the early spring. However, in the period from July to September, the stream water carries the chemical signature of monsoonal precipitation.  相似文献   
177.
《水文科学杂志》2013,58(1):206-220
Abstract

The Asmari limestone formation is the major aquifer system at the Khersan 3 Dam site, Zagros, Iran. Characterization of the aquifer system and study of karst development are essential for forecasting leakage potential and to plan remediation works. The aquifer functioning and karst structure were evaluated by geology, well hydrodynamics and natural tracing studies, showing one unconfined and three artesian sub-aquifers, the last being characterized by rapid flow, with contributing old recharge water, and a recharge at higher elevation than the unconfined sub-aquifer. The anticline structure outcrops the artesian sub-aquifers downstream of the site. The confining layers disappear and the aquifer system discharges as a mix of all groundwater. Artesian groundwater is estimated to contribute about 80% (dry season) and 50% (wet season) of flow in the mixing zone. Very few karst features are observed in cores and galleries at the site, despite some karst landforms in the reservoir area. However the aquifer exhibits fast flow of karst type in the artesian sub-aquifers.  相似文献   
178.
Simultaneously acquiring time series of climate, hydrology and hydrochemical data over decades on river systems is pivotal to understand the complex interactions involving rock, soil water, air and biota in the Critical Zone, to build integrated modelling and to propose predictive scenarios. Among the Critical Zone Observatories (CZOs) implemented in the past 25 years, only a few are located in the humid Tropics despite the importance of these regions in terms of population density, fast-changing land use, biodiversity hotspots, biomass stock on continents, size of river systems, etc. Since 1994, weathering and erosion processes and fluxes have been investigated at both local (experimental watershed) and regional scales in the Nyong River Basin (Cameroon) which belongs to the Critical Zone Observatories network named Multiscale TROPIcal CatchmentS (M-TROPICS). The data shared by M-TROPICS in Cameroon are: (1) rainfall; (2) air temperature, air relative humidity, wind speed and direction, and global radiation; (3) stream and river water level; (4) pH, electrical conductivity, water temperature and suspended particulate matter (SPM) concentration; (5) major ion, alkalinity and dissolved organic carbon (DOC) concentrations. The dataset already contributed to describe the water partitioning in these tropical humid watersheds, to better understand the factors controlling chemical weathering and physical erosion in tropical ecosystems, particularly the role of organic matter. The dataset also contributed to calculate elemental weathering fluxes and saprolite production rate and to propose denudation rates on tropical cratonic landscapes. Hydrological modelling allowed quantification of the geographical water sources contributing to streamflow. DOC data were used to determine greenhouse-gas emissions and carbon budgets from African inland waters. However, long-term solute concentrations at the outlet of a small tributary of the Nyong River exhibit non-stationary behaviour over the last 26 years. The processes governing those fluctuations are not yet fully understood and might be related to changes in the hydrological regime, land-cover and land-use. The latter highlights the need for longer time-series and continued support for CZOs particularly in the humid tropics.  相似文献   
179.
The chemistry of major cations (Mg2+, Ca2+, Na+, and K+) and anions (HCO3 , SO4 2−, and Cl) in the water of Lake Pumayum Co and its inflow river was studied, revealing the obvious ionic difference among various inflow rivers and the lake. The chemical type of the lake water was Mg2+-Ca2+-HCO3 -SO4 2+, but the major ions of the main inflow rivers were Ca2+-Mg2+-HCO3 . In the lake inlet of Jiaqu River, the main inflow river, there was significant variance of water chemistry within the depth less than 2 m. However, it was almost homogeneous at other area of the lake. Therefore, with the evidence of distribution of water chemistry and oxygen isotope of lake water, a conclusion can be outlined that Jiaqu River had a distinct effect on the hydrochemistry of the water on the submerged delta, whereas this is not the case for other rivers. The Gibbs plot revealed that the dominant mechanism responsible for controlling chemical compositions of the lake water was rocks weathering in the drainage area. Ion ratios and ternary plots further explored the main processes controlling the water chemistry of the catchment, i.e., carbonate weathering, pyrite weathering, and silicate weathering. The different hydrochemistry characteristics between river water and lake water may result from the CaCO3 precipitation. The findings will benefit the explanation of the environmental significance of carbonate in paleolimnological studies in the lake.  相似文献   
180.
天水及其南北地区地热水水化学特征及起源   总被引:1,自引:0,他引:1  
运用水化学和同位素示踪的原理追溯地热水的水岩相互作用和起源,得出武山和天水地热水为pH较高(7.94~9.06)的低TDS(226~255 mg/L)HCO3型水,通渭和清水地热水为pH较低(7.1~8.07)的较高TDS(915~1 793 mg/L)SO4型水,地热水的水化学特征主要受不同的围岩及与围岩相互作用的程度所控制。地热水的δD和δ18O值说明地热水起源于大气降水,且未受水-岩同位素交换明显影响。综合应用各种地热温标,估算地热水的热储温度为70~111℃,属于中低温地热资源。对年均降雨量约500 mm的天水及其南北地区,应采取采、停交替的地热水利用方式。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号