全文获取类型
| 收费全文 | 119篇 |
| 免费 | 6篇 |
| 国内免费 | 1篇 |
专业分类
| 测绘学 | 1篇 |
| 大气科学 | 14篇 |
| 地球物理 | 32篇 |
| 地质学 | 66篇 |
| 海洋学 | 6篇 |
| 天文学 | 4篇 |
| 综合类 | 1篇 |
| 自然地理 | 2篇 |
出版年
| 2024年 | 1篇 |
| 2023年 | 1篇 |
| 2022年 | 3篇 |
| 2021年 | 7篇 |
| 2020年 | 8篇 |
| 2019年 | 4篇 |
| 2018年 | 6篇 |
| 2017年 | 9篇 |
| 2016年 | 30篇 |
| 2015年 | 7篇 |
| 2014年 | 8篇 |
| 2013年 | 12篇 |
| 2012年 | 8篇 |
| 2011年 | 5篇 |
| 2010年 | 1篇 |
| 2009年 | 4篇 |
| 2008年 | 4篇 |
| 2007年 | 2篇 |
| 2005年 | 2篇 |
| 1998年 | 1篇 |
| 1995年 | 1篇 |
| 1991年 | 1篇 |
| 1984年 | 1篇 |
排序方式： 共有126条查询结果，搜索用时 0 毫秒
41.
42.
Sayed Zia Mohammadi Daryoush Afzali Mohammad Ali Taher Hedayat Darijani 《洁净——土壤、空气、水》2010,38(2):140-145
In the present article, a procedure for the simultaneous separation and preconcentration of trace amounts of cadmium and zinc is proposed. It is based on the adsorption of cadmium and zinc ions onto a column of Amberlite XAD‐4 resin loaded with aluminon reagent. Cadmium and zinc ions are quantitatively retained on the column in the pH range from 6.5–7.5, at a flow rate of 2 mL min–1. The cadmium and zinc ions are eluted with 5.0 mL of 5 mol L–1 HNO3 solution. Cadmium and zinc are measured by flame atomic absorption spectrometry (FAAS). In the present case, 0.1 μg of cadmium and 0.5 μg of zinc can be concentrated in the column from 1000 mL of aqueous sample, where their concentrations are as low as 0.1 and 0.5 ng mL–1, respectively. The relative standard deviations, for seven replicated determinations of 1.0 μg mL–1 of cadmium and zinc, are 1.2 and 1.1%, respectively. The detection limits for cadmium and zinc in the original solution are 0.02 and 0.11 ng mL–1, respectively. The interference of a large number of anions and cations has been studied and the optimized conditions are utilized for the determination of trace amounts of cadmium and zinc in different environmental and standard samples. 相似文献
43.
Assessing hydrochemical evolution of groundwater in limestone terrain via principal component analysis 总被引：2，自引：2，他引：0
Zargham Mohammadi 《Environmental Earth Sciences》2009,59(2):429-439
This paper describes the use of multivariate statistical analysis to trace hydrochemical evolution in a limestone terrain
at Zagros region, Iran. The study area includes a deep confined aquifer, overlaid by an unconfined aquifer. The method involves
the use of principal component analysis (PCA) to assess and evaluate the hydrochemical evolution based on chemical and isotope
variables of 12 piezometers drilled in both the unconfined and confined aquifers. First PCA on all variables shows that water–rock
interaction under different conditions with respect to the atmospheric CO2 is the main process responsible for chemical constituents. As a result, combinations of several ratios such as Ca/TDS, SO4/TDS and Mg/TDS with physico-chemical and isotope variables reveal different hydrochemical evolution trend in the aquifers.
Second PCA on the selective samples and variables reveals that displacement of the unconfined samples from dry to wet season
follows a refreshing trend towards river samples that is characterized by reducing electrical conductivity and increasing
sulphate and tritium contents. However, the refreshing trend cannot be traced in the confined aquifer samples suggesting no
recharge from river to the confined aquifer. Third PCA reveals that, chemical composition of water samples in the unconfined
aquifer tends to have considerable difference from each other in the end of recharge period. In contrast, the confined aquifer
samples have a tendency to show similar chemical composition during recharge period in comparison to end of dry period. This
difference is caused by different mechanism of recharge in the unconfined aquifer (through the whole aquifer surface) and
the confined aquifer (through the limited recharge area). 相似文献
44.
Historically, there has been a dispute over water allocation between users and policymakers in Iran's Zayandeh-Roud Basin (ZRB). In this study, we used the “System of Environmental-Economic Accounting for Water” (SEEAW) framework in combination with the hydrologic model “Soil and Water Assessment Tool” (SWAT) to achieve the water balance in ZRB. We used SEEAW to combine a wide range of water-related statistics across stakeholders and SWAT to evaluate the unknown agricultural water use. The SWAT model is calibrated based on the stream flows and crop yields in the basin. The model assess the renewable water of the basin into two components, about 363 and 70 mm as green and blue water, respectively. Also results from the physical water supply and water use tables demonstrates that the agricultural sector uses 78% of the total renewable freshwater, followed by the residential, 16%, and the industrial sector, 6%. The flows of water from source to services in ZRB are traced based on the water supply and water use tables. The flow diagram shows that 8 MCM of industrial reused water was transferred to the agricultural sector, and 137 MCM and 18 MCM of water from the wastewater treatment plants to the agricultural and industrial sectors, respectively. Furthermore, the results show that the index of the basin dependence on groundwater resources is high (61%), the value of water stress is high (0.88) and the dependence of the basin on transboundary water resources is 30%. Therefore, this method is highly beneficial for achieving a conceptual water balance in disputed basins without enough agricultural water uses data. 相似文献
45.
46.
47.
48.
49.
50.