全文获取类型
收费全文 | 873篇 |
免费 | 151篇 |
国内免费 | 116篇 |
专业分类
测绘学 | 2篇 |
大气科学 | 1篇 |
地球物理 | 346篇 |
地质学 | 712篇 |
海洋学 | 23篇 |
综合类 | 29篇 |
自然地理 | 27篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 12篇 |
2021年 | 27篇 |
2020年 | 20篇 |
2019年 | 22篇 |
2018年 | 37篇 |
2017年 | 37篇 |
2016年 | 31篇 |
2015年 | 38篇 |
2014年 | 50篇 |
2013年 | 102篇 |
2012年 | 40篇 |
2011年 | 42篇 |
2010年 | 36篇 |
2009年 | 66篇 |
2008年 | 89篇 |
2007年 | 62篇 |
2006年 | 70篇 |
2005年 | 57篇 |
2004年 | 39篇 |
2003年 | 42篇 |
2002年 | 22篇 |
2001年 | 28篇 |
2000年 | 30篇 |
1999年 | 23篇 |
1998年 | 17篇 |
1997年 | 24篇 |
1996年 | 11篇 |
1995年 | 10篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 10篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1987年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有1140条查询结果,搜索用时 125 毫秒
151.
Saed Khayat Peter Möller Stefan Geyer Amer Marei Christian Siebert Fayez Abu Hilo 《Environmental Geology》2009,57(8):1739-1751
The spatial and temporal changes of the composition of the groundwater from the springs along the Wadi Qilt stream running
from the Jerusalem–Ramallah Mountains towards the Jericho Plain is studied during the hydrological year 2006/2007. The residence
time and the intensity of recharge play an important role in controlling the chemical composition of spring water which mainly
depends on distance from the main recharge area. A very important factor is the oxidation of organics derived from sewage
and garbage resulting in variable dissolved CO2 and associated HCO3
− concentration. High CO2 yields lower pH values and thus under-saturation with respect to calcite and dolomite. Low CO2 concentrations result in over-saturation. Only at the beginning and at the end of the rainy season calcite saturation is
achieved. The degradation of dissolved organic matter is a major source for increasing water hardness. Besides dissolution
of carbonates dissolved species such as nitrate, chloride, and sulfate are leached from soil and aquifer rocks together with
only small amounts of Mg. Mg not only originates from carbonates but also from Mg–Cl waters are leached from aquifer rocks.
Leaching of Mg–Cl brines is particularly high at the beginning of the winter season and lowest at its end. Two zones of recharge
are distinguishable. Zone 1 represented by Ein Fara and Ein Qilt is fed directly through the infiltration of meteoric water
and surface runoff from the mountains along the eastern mountain slopes with little groundwater residence time and high flow
rate. The second zone is near the western border of Jericho at the foothills, which is mainly fed by the under-groundwater
flow from the eastern slopes with low surface infiltration rate. This zone shows higher groundwater residence time and slower
flow rate than zone 1. Groundwater residence time and the flow rate within the aquifer systems are controlled by the geological
structure of the aquifer, the amount of active recharge to the aquifer, and the recharge mechanism. The results of this study
may be useful in increasing the efficiency of freshwater exploitation in the region. Some precautions, however, should be
taken in future plans of artificial recharge of the aquifers or surface-water harvesting in the Wadi. Because of evaporation
and associated groundwater deterioration, the runoff water should be artificially infiltrated in zones of Wadis with high
storage capacity of aquifers. Natural infiltration along the Wadis lead to evaporation losses and less quality of groundwater. 相似文献
152.
深部咸水层CO2地质储存工程场地选址技术方法 总被引:4,自引:0,他引:4
CO2地质储存作为环保型工程项目,其合理的工程场址是实现长期、安全封存CO2的首要前提。我国CO2地质储存工作刚刚起步,尚未形成成熟的选址技术方法体系。CO2地质储存工程场地选址应遵循目标储层有效储存量大、安全、经济、符合一般建设项目环境保护选址条件、不受外部不良地质因素影响的原则,选址技术宜采用多尺度目标逼近法,选址程序包括规划选址和工程选址两大阶段。规划选址包括国家级、盆地级和目标区级潜力评价3个阶段;工程选址旨在通过目标靶区确定、综合地质调查、钻探及灌注试验和选定场地多因子排序综合评价,最终选出良好的工程场址。深部咸水层CO2地质储存工程场地多尺度目标逼近选址技术方法对我国批量开展CO2地质储存工程场地选址具有一定的指导意义。 相似文献
153.
Patsakron Assiri 《地下水科学与工程》2013,1(3):95-98
Phu tok Aquifer is the most productive water bearing rock in the Northeastern region of Thailand. Generally, well drilled in this aquifer yields approximately 20–50 m3/hr with some wells yield over 150 m3/hr. This aquifer characterized both unconfined and confined aquifer. Data collected from core sampling and TV bore hole show water bearing fractures in the fine grained massive sandstone intercalated with thin shale layers. These intermittently bedding plane fracture zones were found vertically at 60-65 and 95-110 m below ground surface. Three directions of vertically fractures were also found at 103-104 m in the test well with underlain densely sandstone until 120 m of depth. Wells drilled to 60-70 m fractures at the area where surface elevation between 150 and 170 m above mean sea level were artesian well with rising water about 1-3 m. Natural discharge rate from 2-5 inches of diameter casing is 5-10 m3/hr. Fractures at 90-110 m yield 150 m3/hr through 6 inch casing well with 5-6 m of risen water above the ground. It is found from pumping test of Phu Tok Aquifer that hydraulic conductivity of unconfined aquifer at shallower than 50 m is 0.005-17 m/d. Transmissivity and storage coefficient are 0.05-20 m2/d and 7×10-3-0.725 respectively. The confined aquifer at depth not exceed 90 m has hydraulic conductivity value of 0.2-10 m/d while transmissivity and storage coefficient are 3.19-150 m2/d and 1×10-10-1.6×10-2. Another confined aquifer at 90-120 m of depth have hydraulic conductivity value of 0.08-15 m/d and transmissivity and storage coefficient values of 1.7-178 m2/d and 4×10-7-4.5×10-3 respectively. 相似文献
154.
在滨海地区,地下水水位受潮汐波动影响较大,使得传统的抽水试验、水位回复试验等方法确定含水层参数存在困难且花费较大。通过对广西北海市滨海含水层地下水位动态资料进行分析,发现其上升段和下降段是不对称的。基于海岸带承压含水层正弦潮汐波的传播理论,提出了确定含水层参数的分段法,并与振幅衰减法和滞后时间法进行对比,各种方法求出的储水系数与导水系数之比(S/T)很接近,说明分段法是有效的。对于北海市滨海含水层,上升段求出的S/T值比下降段要大,其成因机理还有待进一步分析。 相似文献
155.
156.
��ѹ����dz�ѹ��ˮλ��ϫЧӦ���䶨������ 总被引:1,自引:0,他引:1
???????????????λ????Ч?????????????????????????? 相似文献
157.
158.
159.
???????????????????????????????????????????λ??????????????????????????????????????????????????????????£????λ????仯???????????????????????????????????????????????????????????????仯??????????????????????????????????????????й?? 相似文献
160.
在鄂尔多斯盆地都思兔河流域供水水文地质详查的基础上,通过水文地质钻探、抽水试验、样品分析等手段,查明了流域含水层的结构、埋深以及含水层和隔水层在水平和垂直方向上的变化规律,探讨了各含水层之间的水力联系,并求取了含水层的水文地质参数;对比圈定了包乐浩晓、巴彦布拉格、好勒包勒吉3处富水区;采用地下水流数值模拟方法对上述3处富水区地下水开采量进行计算,提出了27种地下水开采方案,并经过对比得到地下水开采推荐方案。结果表明:包乐浩晓、巴彦布拉格、好勒包勒吉3处富水区主要补给为侧向径流及大气降水入渗补给,排泄方式以潜水面蒸发及向河流排泄为主;在地下水浅埋区,结合含水层单井涌水量的大小,确定采用管井开采方式、中段悬挂式非完整井结构,平均布井,井深300m,单一开采白垩系环河组的地下水,最大限度夺取潜水蒸发排泄量;根据推荐方案,上述3个富水区总开采量达到123 500m3/d,可为该地区地下水资源开发与利用提供技术保障。 相似文献