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251.
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253.
Luis F. de Diego Margarita de las Obras-Loscertales Francisco García-Labiano Aránzazu Rufas Alberto Abad Pilar Gayán Juan Adánez 《International Journal of Greenhouse Gas Control》2011,5(5):1190-1198
CO2 and SO2 are some of the main polluting gases emitted into atmosphere in combustion processes using fossil fuel for energy production. The former is one of the major contributors to build-up the greenhouse effect implicated in global climate change and the latter produces acid rain. Oxy-fuel combustion is a technology, which consists in burning the fuel with a mix of pure O2 and recirculated CO2. With this technology the CO2 concentration in the flue gas may be enriched up to 95%, becoming possible an easy CO2 recovery. In addition, oxy-fuel combustion in fluidized beds allows in situ desulfurization of combustion gases by supplying calcium based sorbent.In this work, the effect of the principal operation variables affecting the sulfation reaction rate in fluidized bed reactors (temperature, CO2 partial pressure, SO2 concentration and particle size) under typical oxy-fuel combustion conditions have been analyzed in a batch fluidized bed reactor using a limestone as sorbent. It has been observed that sulfur retention can be carried out by direct sulfation of the CaCO3 or by sulfation of the CaO (indirect sulfation) formed by CaCO3 calcination. Direct sulfation and indirect sulfation operating conditions depended on the temperature and CO2 partial pressure. The rate of direct sulfation rose with temperature and the rate of indirect sulfation for long reaction times decreased with temperature. An increase in the CO2 partial pressure had a negative influence on the sulfation conversion reached by the limestone due to a higher temperature was needed to work in conditions of indirect sulfation. Thus, it is expected that the optimum temperature for sulfur retention in oxy-fuel combustion in fluidized bed reactors be about 925–950 °C. Sulfation reaction rate rose with decreasing sorbent particle size and increasing SO2 concentration. 相似文献
254.
Paolo Cabras Alberto Angioni Vincenzo L. Garau Marinella Melis Filippo. M. Pirisi Franco Cabitza 《Journal of environmental science and health. Part. B》2013,48(6):1189-1199
Abstract Residues of three pesticides (dimethoate, parathion, and pyrazophos) in two artichoke cultivars, Masedu and Spinoso sardo, were investigated. The amount of pesticides in artichokes was greatly affected by the head shape. In the case of the calix‐shaped Masedu artichoke, the residues in whole heads at commercial ripening were on average about twice higher than those of the pagoda‐shaped Spinoso sardo artichoke. In the heart this ratio was 4 to 42 times greater. Residue decay rates were very fast, mainly owing to the dilution effect due to head growth. 相似文献
255.
Ulises Diéguez-Aranda Fernando Castedo Dorado Juan Gabriel Álvarez González Alberto Rojo Alboreca 《Ecological modelling》2006
In this study we developed a dynamic growth model for Scots pine (Pinus sylvestris L.) plantations in Galicia (north-western Spain). The data used to develop the model were obtained from a network of permanent plots, of between 10 and 55-year-old, which the Unidade de Xestión Forestal Sostible (Sustainable Forest Management Unit) of the University of Santiago de Compostela has set up in pure plantations of this species of pine in its area of distribution in Galicia. In this model, the initial stand conditions at any point in time are defined by three state variables (number of trees per hectare, stand basal area and dominant height), and are used to estimate stand volume, classified by commercial classes, for a given projection age. The model uses three transition functions expressed as algebraic difference equations of the three corresponding state variables used to project the stand state at any point in time. In addition, the model incorporates a function for predicting initial stand basal area, which can be used to establish the starting point for the simulation. This alternative should only be used when the stand is not yet established or when no inventory data are available. Once the state variables are known for a specific moment, a distribution function is used to estimate the number of trees in each diameter class, by recovering the parameters of the Weibull function, using the moments of first and second order of the distribution (arithmetic mean diameter and variance, respectively). By using a generalized height–diameter function to estimate the height of the average tree in each diameter class, combined with a taper function that uses the above predicted diameter and height, it is then possible to estimate total or merchantable stand volume. 相似文献
256.
Maurizio Pettine Silvio Capri Maria Giuseppina Farrace Maura Manganelli Luisa Patrolecco Alberto Puddu Annamaria Zoppini 《Chemistry and Ecology》2002,18(1):13-25
The results obtained in the four seasonal cruises planned in the PRISMA II project are reported. These concern dissolved and colloidal organic carbon, free amino acids and total dissolved carbohydrates and heterotrophic activity. Main factors controlling organic matter degradation, resulting from laboratory tests not planned in the above project, are also discussed. Dissolved organic matter shows seasonal accumulation, which may be markedly different from year to year, and large contributions by colloidal and saccharide components. Heterotrophic activities play an important role in the carbon cycle, although laboratory runs highlight limitations caused by aging of organic matter and phosphorus deficiency. 相似文献
257.
Alberto Fonseca Patricia Fitzpatrick Mary Louise McAllister 《Natural resources forum》2013,37(4):211-220
The socio‐economic fabric of single‐company mining towns needs to be carefully considered by both Government and companies in sustainability policymaking. Policy design and effectiveness in such towns are significantly impacted by the city's economic dependence on a single company. This paper explores the perceived effectiveness of government and voluntary private sector mining policies for pursuing sustainability in the historic mining town of Itabira, Brazil over a period of 20 years. Itabira serves as a worthwhile case study because it allows for an in‐depth and longitudinal analysis that can reveal valuable lessons to policymakers of different sectors and jurisdictions located elsewhere. Based on extensive face‐to‐face interviews and literature reviews, study results indicate that changes to the state environmental licensing policies in the 1990s led to significant socio‐environmental improvements in the area. The globalization of the mining company also contributed to an increase in the quantity and quality of voluntary industry policies. Recent technological improvements in the beneficiation processes of the mining company promises to extend the life of the mine to 2050. Although there are significant incremental socio‐environmental policies and programmes, sustainability remains an elusive vision in Itabira, with no clear objectives or monitoring and accountability mechanisms. The paper concludes by recommending a more formal integrated policymaking framework. 相似文献
258.
Urban waste recycling behavior: antecedents of participation in a selective collection program 总被引:1,自引:0,他引:1
ABSTRACT/
The aim of this study is to analyze the antecedents of urban waste recycling behavior. To achieve this goal, a concrete urban
waste management program was chosen. The study focuses on the Selective Collection Program (SCP) in Zaragoza, a medium-sized
city in northeastern Spain. The research starts with a conceptual model in which the variables that potentially affect recycling
behavior can be classified into two groups: incentives and barriers. Moreover, the sociodemographic characteristics of the
individuals are included in our study. Given that the proposed model requires specification of latent variables or constructs,
the analysis is based on the Structural Equation Models (SEM) methodology. The results revealed that environmental awareness,
knowledge of the environmental impact of urban waste, and the positive perception of management by local government exercise
a positive effect on individual recycling behavior, while perceived personal difficulties (space and time availability) and
distance to and from the container have a negative effect. As regards sociodemographic variables, this study found that annual
family income sustains a negative relationship with recycling behavior, while age maintains a positive one. The results obtained
clearly show the important role that the public authorities play, especially municipal governments, in achieving the waste
recycling objectives established in accordance with international legislation. 相似文献
259.
Madruga MJ Brogueira A Alberto G Cardoso F 《Journal of environmental radioactivity》2001,54(1):175-188
Large amounts of solid wastes (tailings) resulting from the exploitation and treatment of uranium ore at the Urgeiri?a mine (north of Portugal) have been accumulated in dams (tailing ponds). To reduce the dispersion of natural radionuclides into the environment, some dams were revegetated with eucalyptus (Eucalyptus globolus) and pines (Pinus pinea). Besides these plants, some shrubs (Cytisus spp.) are growing in some of the dams. The objective of this study is to determine the 226Ra bioavailability from uranium mill tailings by quantifying the total and available fraction of radium in the tailings and to estimate its transfer to plants growing on the tailing piles. Plant and tailing samples were randomly collected and the activity concentration of 226Ra in plants (aerial part and roots) and tailings was measured by gamma-spectrometry. The exchangeable fraction of radium in tailings was quantified using one single step extraction with 1 mol dm-3 ammonium acetate (pH = 7) or 1 mol dm-3 calcium chloride solutions. The results obtained for 226Ra uptake by plants show that 226Ra concentration ratios for eucalyptus and pines decrease at low 226Ra concentrations in the tailings and appear relatively constant at higher radium concentrations. For shrubs, the concentration ratios increase at higher 226Ra solid waste concentrations approaching a saturation value. Percentage values of 16.0 +/- 8.3 and 12.9 +/- 8.9, for the fraction of radium extracted from the tailings, using 1 mol dm-3 ammonium acetate or calcium chloride solutions, respectively, were obtained. The 226Ra concentration ratios determined on the basis of exchangeable radium are one order of magnitude higher than those based on total radium. It can be concluded that, at a 95% confidence level, more consistent 226Ra concentration ratios were obtained when calculated on the basis of available radium than when total radium was considered, for all the dams. 相似文献
260.
Leonardo?Alberto?Rios?OsorioEmail author Manuel?Ortiz?Lobato Xavier?álvarez?Del?Castillo 《Environment, Development and Sustainability》2005,7(4):501-518
The paper analyzes the concept of sustainable development in the light of the different interpretations existing on the issue
since its appearance and establishment as an ideal to lead humanity’s line of progress. Within these interpretations, a characteristic
generation of diverse debates can be appreciated, arising from different perspectives, academic as well as ideological, aiming
at describing, clarifying and determining their conceptual reach.
Based on these facts a model of categorization for these debates has developed, a model in which interpretations generated
on the concept of sustainable development were catalogued into four realms: conceptual, contextual, academic and geopolitical.
The configuration of these four areas of debate, as well as the recognition of the diversity of interpretations existing on
sustainable development, is a reflection of the intrinsic complexity of the phenomena, which affect the natural and social
world, both at the local and global level. The analysis of this complexity is based on the subjectivity, which is inherent
to the interpretation of these phenomena, with permanent reference to the cultural context from which the diverse discourses
were structured.
This global perspective on the state-of-the-art controversy concerning the idea of sustainable development as an articulatory
axis reveals the necessity of building epistemological models, which can give a new direction to scientific research. From
these new models, based on the analysis of the holistic character of reality, the subjective and the objective must be integrated
in the generation of knowledge, which contributes usefully to the unceasing reconstruction of our world-(view).
Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue. 相似文献