全文获取类型
收费全文 | 908篇 |
免费 | 82篇 |
国内免费 | 107篇 |
专业分类
安全科学 | 94篇 |
废物处理 | 13篇 |
环保管理 | 265篇 |
综合类 | 357篇 |
基础理论 | 145篇 |
污染及防治 | 50篇 |
评价与监测 | 110篇 |
社会与环境 | 39篇 |
灾害及防治 | 24篇 |
出版年
2024年 | 3篇 |
2023年 | 22篇 |
2022年 | 14篇 |
2021年 | 31篇 |
2020年 | 35篇 |
2019年 | 32篇 |
2018年 | 29篇 |
2017年 | 34篇 |
2016年 | 50篇 |
2015年 | 37篇 |
2014年 | 62篇 |
2013年 | 67篇 |
2012年 | 64篇 |
2011年 | 76篇 |
2010年 | 51篇 |
2009年 | 46篇 |
2008年 | 43篇 |
2007年 | 55篇 |
2006年 | 56篇 |
2005年 | 38篇 |
2004年 | 31篇 |
2003年 | 25篇 |
2002年 | 26篇 |
2001年 | 26篇 |
2000年 | 25篇 |
1999年 | 15篇 |
1998年 | 13篇 |
1997年 | 12篇 |
1996年 | 12篇 |
1995年 | 12篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1972年 | 1篇 |
排序方式: 共有1097条查询结果,搜索用时 31 毫秒
971.
Realistic models of contaminant transport in groundwater demand detailed characterization of the spatial distribution of subsurface hydraulic properties, while at the same time programmatic constraints may limit collection of pertinent hydraulic data. Fortunately, alternate forms of data can be used to improve characterization of spatial variability. We utilize a methodology that augments sparse hydraulic information (hard data) with more widely available hydrogeologic information to generate equiprobable maps of hydrogeologic properties that incorporate patterns of connected permeable zones. Geophysical and lithologic logs are used to identify hydrogeologic categories and to condition stochastic simulations using Sequential Indicator Simulation (SIS). The resulting maps are populated with hydraulic conductivity values using field data and Sequential Gaussian Simulation (SGS). Maps of subsurface hydrogeologic heterogeneity are generated for the purpose of examining groundwater flow and transport processes at the Faultless underground nuclear test, Central Nevada Test Area (CNTA), through large-scale, three-dimensional numerical modeling. The maps provide the basis for simulation of groundwater flow, while transport of radionuclides from the nuclear cavity is modeled using particle tracking methods. Sensitivity analyses focus on model parameters that are most likely to reduce the long travel times observed in the base case. The methods employed in this study have improved our understanding of the spatial distribution of preferential flowpaths at this site and provided the critical foundation on which to build models of groundwater flow and transport. The results emphasize that the impacts of uncertainty in hydraulic and chemical parameters are dependent on the radioactive decay of specific species, with rapid decay magnifying the effects of parameters that change travel time. 相似文献
972.
Edeltrauda Helios Rybicka Michael Jefferson Wilson 《Environmental science and pollution research international》2000,7(1):7-13
The examinations of selected wastes and stream sediments from the vicinity of a chemical plant by sequential extraction procedures
and direct methods, SEM/EDX and XRD, were carried out in order to identify the different forms of chromium, particularly as
they are released to potential mobility. The results show that the top and bottom waste samples contain 37,756 and 53,650
μg g1 Cr, respectively, but about 7% and 2% of the total chromium type Cr(VI). The chemical extraction results show that the mobility
of Cr in the upper part of the waste pile is significantly higher than in the bottom section; the exchangeable form of Cr
accounts for 25% and < 1%, respectively, the last one irrespective of redox conditions. About 50% of Cr is associated with
the reducible fraction of the top waste, and similar with the residual fraction in the bottom waste. Oxidation of the bottom
waste shift some portion of Cr from residual to the moderately reducible fraction. The major Cr-forms in the river sediments
are compounded with Fe-oxides. The < 2 μm size fraction of the selected sediment sample, particular enriched in chromium contained
up to 73,000 μg g1 Cr with about 95% of this in the moderately reducible fraction, predominantly bound with oxyhydroxides. SEM/EDX and XRD analysis
of wastes and river sediment indicate that the main insoluble Cr-phase is ferroan — (Mg, Fe) (Cr, Al)2O4 which would be dissolved mainly in the residual fraction. 相似文献
973.
将上海市某城市污水处理厂的生产运行数据进行了计算机模拟,并将模拟结果中的COD及TSS、TN、NH3-N等组分的浓度与实测数据进行了比较。通过对模型参数进行修正和调整,仅改变ASM1数学模型中的4个参数,即取得了较好的预测效果。同时对城市污水处理厂进一步运用数学模型的可行性进行了讨论。 相似文献
974.
975.
This study was undertaken to ascertain optimal methods of sampling, preserving, separating, and analyzing arsenic species
in potentially contaminated waters. Arsenic species are readily transformed in nature by slight changes in conditions. Each
species has a different toxicity and mobility. The conventional field sampling method using filters of 0.45 μm in size could
overestimate the dissolved arsenic concentrations, as passing suspended particles that can act as a sink or source of arsenic
depending on the site condition. For arsenic species in neutral pH and iron-poor waters, the precipitation can be stable for
up to 3 days without any treatment, but for longer periods, a preservative, such as phosphoric acid, is required. Also, the
analytical procedure must be selected carefully because the levels and hydride generation efficiencies of arsenic in different
species can vary, even for the same amount of arsenic. For arsenic speciation in samples that also include organic species,
a hybrid high-performance liquid chromatography (HPLC) column and inductively coupled plasma mass spectrometry (ICP-MS) gave
the best resolution and lowest detection limits. However, the procedure using a solid phase extraction (SPE) cartridge can
be used economically and conveniently for analyzing samples containing only inorganic arsenic species, such as groundwater,
especially that related to mine activity. 相似文献
976.
977.
Environmental impact assessment (EIA) procedures have been in existence in the People's Republic of China over the last decade.
The impetus for China's introduction of EIA was provided by the Environmental Protection Law of the People's Republic of China,
which was adopted by the Fifth National People's Congress in 1979. The EIA process, which is administrative and not statutorily
mandated, has been applied primarily to construction projects.
Four stages are typically involved in an EIA investigation: design of the investigation, evaluation of background environmental
quality, prediction of environmental impacts, and an assessment and analysis of the environmental impacts. A variety of approaches
is used for predicting and analyzing environmental impacts, ranging from ad hoc methods to fairly sophisticated mathematical
models. The results of the EIA investigation are compiled in an environmental impact statement, which is used as the basis
for decision making by personnel in environmental protection departments. The EIA process does not include provisions for
citizen notification or involvement.
Views differ concerning the effectiveness of the EIA program in protecting China's natural, social, and cultural environments.
Some hold that the EIA program has brought about improvement in environmental protection, while critics contend that the program
has had little effect in the prevention of pollution. However, most, if not all, observers seem to feel that the program should
be continued and improved. A major avenue for improvement is to place the evaluation of a particular project in a regional
context.
An earlier version of this paper was distributed at a workshop on Environmental Assessment Development Planning held in conjunction
with the VII Annual Meeting of the International Association for Impact Assessment, Brisbane, Australia, July 5–8, 1988. 相似文献
978.
如何提高COD比色法测试的精密度和准确度 总被引:3,自引:0,他引:3
针对COD比色法测试的技术特点,通过总结日常分析、验收考核中存在的经验和问题,给出了如何提高COD测试仪测量精密度、准确度的方法和仪器质量的核查方法。 相似文献
979.
Estimation of the Soil Respiration Using the Constant Pressure Volumetric Respirometer and the Flow-Through Respirometer UNI-RES10 总被引:1,自引:0,他引:1
Among commonly employed methods of fast estimation of the soil biological activity a method of the oxygen consumption determination is used. The main goal of this research was an estimation of a soil respiratory metabolism using the constant pressure volumetric respirometer and also using the flow-through respirometer UNI-RES10.Soil respiration measurements were done using both types of respirometers in temperatures 10, 15, 20, 25, 30 and 35 °C, keeping up the constant humidity. The investigated soil was a soil humus belonged to organic soils from the Dziekanów Leny field. The soil respiration was also measured for 8 plant communities in Sudeten Mountains with various respiration intensity.After the experiments it was stated that both measuring instruments could be used for the soil metabolism evaluation. Readouts obtained from the UNI-RES10 respirometer are smaller then readouts when using the constant pressure volumetric respirometer. The flow-through respirometers have to be calibrated to obtain results comparable with these from volumetric ones. The volumetric and flow-through respirometry methods are useful for the comparative analysis of metabolism levels. 相似文献
980.
Hydrological influences on the water quality trends in Tamiraparani Basin,South India 总被引:5,自引:0,他引:5
Ravichandran S 《Environmental monitoring and assessment》2003,87(3):293-309
Water quality variables – Turbidity, pH, Electrical Conductivity(EC), Chlorides and Total Hardness (TH) were monitored at adownstream location in the Tamiraparani River during 1978–1992. The observations were made at weekly intervals in a watertreatment and supply plant using standard methods. Graphical andstatistical analyses were used for data exploration, trenddetection and assessment. Box-Whisker plots of annual andseasonal changes in variables indicated apparent trends beingpresent in the data and their response to the seasonal influenceof the monsoon rainfall. Further, the examination of the medianvalues of the variables indicated that changes in the directionof trend occurred during 1985–1986, especially in pH, EC and TH. The statistical analyses were done using non-parametric methods,the ANCOVA on rank transformed data and the Seasonal Man-Kendalltest. The presence of monotonic trend in all the water qualityvariables was confirmed, however, with independent direction ofchange. The trend line was fitted by the method of leastsquares. The estimated values indicated significant increases inEC (28 S cm-1) while significant decreases were observed inturbidity (90 NTU), pH (0.78), and total hardness (23 ppm) in a span of 15 years. The changes induced in river flow by the addition of a stabilizing reservoir, the influence of seasonal and spatialpattern of monsoon rainfall across the river basin and the increased agriculture appear causative factors for the water quality trends seen in the Tamiraparani River system. 相似文献