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901.
Land Degradation: A Challenge to Ethiopia 总被引:11,自引:3,他引:8
Taddese G 《Environmental management》2001,27(6):815-824
Land degradation is a great threat for the future and it requires great effort and resources to ameliorate. The major causes
of land degradation in Ethiopia are the rapid population increase, severe soil loss, deforestation, low vegetative cover and
unbalanced crop and livestock production. Inappropriate land-use systems and land-tenure policies enhance desertification
and loss of agrobiodiversity. Utilization of dung and crop residues for fuel and other uses disturbs the sustainability of
land resources. The supply of inputs such as fertilizer, farm machinery and credits are very low. The balance between crop,
livestock, and forest production is disturbed, and the farmer is forced to put more land into crop production. For environmentally
and socially sustainable development, there is an urgent need to promote awareness and understanding of the interdependence
of natural, socioeconomic, and political systems at local and national levels. Understanding the current status and causes
of land degradation is very important. This paper reveals the important elements of land degradation in Ethiopia and suggests
possible solutions that may help to ameliorate the situation. 相似文献
902.
We develop indicators showing the relative environmental burdens that human activities place on locales for a given level of economic benefits. The main purpose is to develop tools that allow us to examine the potential vulnerabilities within economies to changes in resource conditions. The indicators of pollution emission or resource consumption per job can be used to identify potential challenges to resource and industry managers and to compare areas in terms of their ability to adapt to change. For example, if a large number of area jobs are dependent on abundant water, this indicates a vulnerability to a reduction in water availability for industrial use. We develop a case study for 23 counties and 1 city in Maryland to examine the usefulness and limitations of the indicators. Our case study demonstrates that the indicators provide an informative view into patterns of local economic activity and use of an area’s environmental goods and services. In contrast to patterns for total environmental burdens (e.g., total SO2 emissions) that are typically reported, the rates of environmental burden per job are not simply correlated with high or low economic output. Thus, the indicators represent distinct patterns of environmental burdens per job that reflect reliance on environmental services. The indicators have some limitations when used at this fine scale because they can misrepresent conditions in counties in which economic sectors are dominated by one or a few businesses. For this reason, the indicators are best used as a regional screening tool. 相似文献
903.
本文建立了连续点源和瞬时点源两种常见排污工况下河流污染带的特征参数预测模型,模型预测的污染带特征参数包括污染物达到全断面均匀混合的距离、污染带最大长度、最大宽度及其出现的位置、污染带面积等,并能利用污染带的特征参数反演推算允许排污量和削减量。模型所用方法简便易行,且具有较高精度,可用于常规连续排污和突发事故排污情况下的河流污染带预测。在此基础上,研制开发了河流污染带特征参数预测系统(RPZS),方便实用。 相似文献
904.
Pb2+、Cr6+、Cd2+单一及其复合污染对白蝴蝶叶片CAT、POD活性的影响 总被引:4,自引:0,他引:4
采用室内溶液培养法研究了Pb^2+、Cr^6+、Cd^2+单一及其复合污染对白蝴蝶叶片过氧化氢酶(CAT)和过氧化物酶(POD)活性的影响。结果表明在处理浓度范围内,处理后白蝴蝶叶片CAT活性明显高于对照,随着各处理浓度的增加,表现先升高后降低最后再上升的趋势。经Cd^2+及复合污染处理后,白蝴蝶叶片内POD活性变化趋势与CAT活性相似;但是经Pb^2+、Cr^6+处理后,其POD活性变化趋势与CAT不同,即在高浓度处理下,POD活性明显低于对照。当处理浓度为100mg/L时,POD活性随着处理时间的延长表现出先升高再降低的趋势。可以认为,酶活性升高是由于白蝴蝶对Pb^2+、Cr^6+、Cd^2+单一及其复合胁迫做出的应激反应。 相似文献
905.
Terrestrial and Aquatic Invertebrates as Bioindicators for Environmental Monitoring, with Particular Reference to Mountain Ecosystems 总被引:8,自引:0,他引:8
The use of terrestrial and aquatic invertebrates as a management tool for monitoring change in ecosystems is reviewed and critically evaluated. Their suitability and value for assessing a range of environmental problems from pollution impacts, through habitat evaluation for conservation to the long-term degradation and recovery of ecosystems, is critically discussed. Guidelines are provided for the choice of appropriate bioindicators. Examples of the use of a broad spectrum of invertebrates to assess a variety of environmental problems are summarized. The particular potential of invertebrates for monitoring montane ecosystems is highlighted. 相似文献
906.
Reyad A. Shawabkeh Omar A. Al-Khashman Hamzeh S. Al-Omari Ali F. Shawabkeh 《The Environmentalist》2007,27(3):357-363
Natural bentonite was treated by hydrochloric, nitric, and phosphoric acids followed by washing with sodium hydroxide in order
to enhance its adsorption capacity. The sample that treated with hydrochloric acid followed by further treatment with NaOH
showed the highest cation exchange capacity with a value of 51.20 meq/100 g. The zero-point of charge for this sample was
found to be 4.50. Adsorption isotherms for both cobalt and zinc were fitted using Langmuir, Freundlich, and Redlich-Peterson
and showed an adsorption capacity of 138.1 mg Co2+ and 202.6 mg Zn2+ per gram of treated sample. 相似文献
907.
908.
Can China control the side effects of motor vehicle growth? 总被引:2,自引:0,他引:2
Michael P. Walsh 《Natural resources forum》2007,31(1):21-34
Motor vehicle growth in China is the fastest in the world. This is placing great strain on the urban environment and causing a rapid increase in oil imports and motor vehicle carbon dioxide emissions. To deal with the environmental and health effects of air pollution, China has adopted a strong motor vehicle pollution control programme and imposed limits on fuel consumption of new light duty vehicles. The article will review these problems and programmes. Special focus will be given to the need to reduce sulphur levels in both gasoline and diesel fuel. 相似文献
909.
Various air pollution control (APC) techniques were employed in order to reduce emissions of air pollutants produced from
chemical plants, which have many different chemical production facilities. For an emission reduction of acid gases, this study
employed a method to improve solubility of pollutants by decreasing the operating temperature of the scrubbers, increasing
the surface area for effective contact of gas and liquid, and modifying processes in the acid scrubbers. To reduce emission
of both amines and acid gases, pollutant gas components were first separated, then condensation and/or acid scrubbing, depending
on the chemical and physical properties of pollutant components, were used. To reduce emission of solvents, condensation and
activated carbon adsorption were employed. To reduce emission of a mixture gases containing acid gases and solvents, the mixed
gases were passed into the first condenser, the acid scrubber, the second condenser, and the activated carbon adsorption tower
in sequence. As a strategy to reduce emission of pollutants at the source, this study also employed the simple pollution prevention
concept of modification of the previously operating APC control device. Finally, air emissions of pollutants produced from
the chemical plants were much more reduced by applying proper APC methods, depending upon the types (physical or chemical
properties) and the specific emission situations of pollutants. 相似文献
910.
A multiple regression model of atmospheric deposition of salt, combined with geographic information systems (GIS) data on
four classes of roads, is used to predict sodium concentrations in 162 randomly chosen streams in Massachusetts. All four
classes of roads, as well as atmospheric deposition, were found to be highly significant in a model that explains 68% of the
observed variation in sodium concentration. The highest salt loading rates are associated with interstate and major state
roads with an estimated 22,500 and 17,700 kg of salt per kilometer, respectively. Our mass balance calculations indicate road
salt is the major source of salt to the streams in Massachusetts.
We examined some of the common statistical problems associated with the use of multiple regression for this type of analysis.
Our confidence in the accuracy of the loading rates estimated above are limited by the collinear nature of environmental data
and uncertainties related to model specification. Our results suggest multiple regression techniques can lead to overconfidence
in the accuracy of the estimated loading rates and thus should not be used as the basis for policy unless the model is validated. 相似文献