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81.
A. Greco R. Gennaro A. Timo F. Bonfantini A. Maffezzoli 《Journal of Polymers and the Environment》2013,21(4):910-916
This work is aimed to study the suitability of the wooden backbone of Opuntia ficus indica cladodes as reinforcement for the production of bio-composites. The wooden backbone can be extracted from O. ficus indica cladodes, which constitute a very relevant agricultural scrap, and is characterized by a thick walled cellular structure. In view of its potential in poly-lactic acid (PLA) matrix bio-composite production, two different possible applications were examined. In the first alternative, the wooden backbone was used in replacement of flax fibers for the production of fully consolidated bio-composites. Results obtained have shown that, though being characterized by lower properties compared to those of flax fiber composites, the opuntia actually works as an efficient reinforcement for PLA/wood flour matrix, increasing the flexural strength and elongation at break. In the second alternative, the cellular structure was used for the production of a sandwich bio-composite with a PLA/wood flour skin. In this case, the very high interlaminar adhesion strength between the skin and the core was considered as an indication of the potentiality of this material for the production of high strength sandwich structures. As a confirmation of this, no interlaminar debonding was observed during short beam tests. 相似文献
82.
Zambrano L Contreras V Mazari-Hiriart M Zarco-Arista AE 《Environmental management》2009,43(2):249-263
Awareness of environmental heterogeneity in ecosystems is critical for management and conservation. We used the Xochimilco
freshwater system to describe the relationship between heterogeneity and human activities. This tropical aquatic ecosystem
south of Mexico City is comprised of a network of interconnected canals and lakes that are influenced by agricultural and
urban activities. Environmental heterogeneity was characterized by spatially extensive surveys within four regions of Xochimilco
during rainy and dry seasons over 2 years. These surveys revealed a heterogeneous system that was shallow (1.1 m, SD = 0.4 ),
warm (17°C, SD = 2.9), well oxygenated (5.0 mg l−1, SD = 3), turbid (45.7 NTU SD = 26.96), and extremely nutrient-rich (NO3–N = 15.9 mg l−1, SD=13.7; NH4–N = 2.88 mg l−1, SD = 4.24; and PO4–P = 8.3 mg l−1, SD = 2.4). Most of the variables were not significantly different between years, but did differ between seasons, suggesting
a dynamic system within a span of a year but with a high resilience over longer periods of time. Maps were produced using
interpolations to describe distributions of all variables. There was no correlation between individual variables and land
use. Consequently, we searched for relationships using all variables together by generating a combined water quality index.
Significant differences in the index were apparent among the four regions. Index values also differed within individual region
and individual water bodies (e.g., within canals), indicating that Xochimilco has high local heterogeneity. Using this index
on a map helped to relate water quality to human activities and provides a simple and clear tool for managers and policymakers. 相似文献
83.
Hector G. Riveros Alfredo Alba Pilar Ovalle Beatriz Silva Ernesto Sandoval 《Journal of the Air & Waste Management Association (1995)》2013,63(5):459-462
ABSTRACT From the analysis of data of the Inspection/Maintenance (I/M) program, and of the long-term trend of ambient CO concentrations in Mexico City, it is inferred that three-way catalysts (TWCs) have a 45% efficiency, well below the expected 90% value. The most probable causes are sulfur poisoning, lead contamination, and ceramic breakage due to bumps and potholes on the streets. Also, we have found a ratio between the average daily peak value of atmospheric CO and gasoline consumption: (11 ± 1) ppbCO/MLm (million liters of gasoline per month) in 1988 decaying to (10 ±1) in 1991 for Mexico City before the introduction of TWCs. In addition, we found a correlation between the monthly averages of CO daily peak and meteorological variables, explaining most of the seasonal changes using only the intensity of the inversion layer and surface wind speed. 相似文献
84.
Daniela Turchetti Elisabetta Razzaboni Hila Zomer Cesare Rossi Simona Ferrari Donatella Greco Claudio Graziano Giovanni Romeo Marco Seri 《黑龙江环境通报》2006,26(12):1156-1159
Angelman Syndrome (AS), characterized by mental retardation, absence of speech, seizures and motor dysfunction, is caused by genetic defects leading to loss of expression of the maternal copy of the chromosome 15q11–13 imprinted region. Most cases are sporadic, being caused by de novo deletion of maternal chromosome 15q11–13 (75%) or by paternal uniparental disomy (3–4%). Familial cases can occur, due to mutations in the UBE3A gene or in the imprinting center. We describe the case of a pregnant woman having two nephews with AS caused by a UBE3A mutation; lack of communication within the family led the woman to be completely unaware of the risk of disease recurrence until 15 weeks of gestation. UBE3A genetic testing revealed she carried the familial mutation 892–893delCT. Prenatal diagnosis was performed on amniotic fluid and demonstrated that the fetus had inherited the mutation. The unexpected diagnosis and the subsequent termination of the pregnancy caused the woman to undergo acute psychological distress showing relevant psychopathological symptoms. Nevertheless, at 2-year follow-up, adverse consequences were minimized, and the couple was planning a new pregnancy. Factors affecting the psychological outcome of abortion and the role of psychological support in reducing the risk of long-term unfavorable consequences are discussed. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
85.
Direct and indirect photolysis of two quinolinecarboxylic herbicides in aqueous systems 总被引:2,自引:0,他引:2
The photodegradation of two quinolinecarboxylic herbicides, 7-chloro-3-methylquinoline-8-carboxylic acid (QMe) and 3,7-dichloroquinoline-8-carboxylic acid (QCl), was studied in aqueous solution at different irradiation wavelengths. The effect of sunlight irradiation was investigated also in the presence of titanium dioxide (TiO2). UV irradiation degraded rapidly QMe affording 7-chloro-3-methylquinoline (MeQ) through a decarboxylation reaction. The reaction rate was lower in the presence of dissolved organic carbon (DOC) because of the adsorption of the herbicide on the organic components. Instead, QCl was stable under both UV light and sunlight irradiation. The irradiation of QMe or QCl solutions with simulated sunlight in the presence of TiO2 produced the complete mineralization of the two herbicides. 相似文献
86.
87.
88.
Alba Pineda-Solano Lina R. Saenz Victor Carreto Maria Papadaki M. Sam Mannan 《Journal of Loss Prevention in the Process Industries》2012,25(5):797-802
This work shows an application of inherent safety principles to a reaction widely used in the pharmaceutical industry. More specifically, it incorporates the teachings of Trevor Kletz into the design of an inherently safer process for the N-oxidation of alkylpyridines. This reaction is of interest because of the hazards resulting from the undesired, gas-generating decomposition of hydrogen peroxide, the oxidizing agent. The generation of oxygen, combined with the flammability of the alkylpyridines, represents a serious fire and explosion hazard for this process. The purpose of this paper is to demonstrate how an inherently safer process can be potentially achieved by designing improved reactors and by assessing conditions that reduce or eliminate the hazards. Furthermore, it is shown that such improvement in safety increases the efficiency of the process and results in a cost reduction. 相似文献
89.
Optimal defense theory posits that plants with limited resources deploy chemical defenses based on the fitness value of different tissues and their probability of attack. However, what constitutes optimal defense depends on the identity of the herbivores involved in the interaction. Generalists, which are not tightly coevolved with their many host plants, are typically deterred by chemical defenses, while coevolved specialists are often attracted to these same chemicals. This imposes an "evolutionary dilemma" in which generalists and specialists exert opposing selection on plant investment in defense, thereby stabilizing defenses at intermediate levels. We used the natural shift in herbivore community composition that typifies many plant invasions to test a novel, combined prediction of optimal defense theory and the evolutionary dilemma model: that the within-plant distribution of defenses reflects both the value of different tissues (i.e., young vs. old leaves) and the relative importance of specialist and generalist herbivores in the community. Using populations of Verbascum thapsus exposed to ambient herbivory in its native range (where specialist and generalist chewing herbivores are prevalent) and its introduced range (where only generalist chewing herbivores are prevalent), we illustrate significant differences in the way iridoid glycosides are distributed among young and old leaves. Importantly, high-quality young leaves are 6.5x more highly defended than old leaves in the introduced range, but only 2x more highly defended in the native range. Additionally, defense levels are tracked by patterns of chewing damage, with damage restricted mostly to low-quality old leaves in the introduced range, but not the native range. Given that whole-plant investment in defense does not differ between ranges, introduced mullein may achieve increased fitness simply by optimizing its within-plant distribution of defense in the absence of certain specialist herbivores. 相似文献
90.
Avian incubation dramatically reduces the abundance and diversity of microbial assemblages on eggshells, and this effect has
been hypothesized as an adaptive explanation for partial incubation, the bouts of incubation that some birds perform during
the egg-laying period. However, the mechanisms for these antimicrobial effects are largely unknown. In this study, we hypothesized
that microbial inhibition is partly achieved through removal of liquid water, which generally enhances microbial growth, from
eggshells, and experimentally tested this hypothesis in two ways. First, we placed the first- and second-laid eggs of tree
swallow (Tachycineta bicolor) clutches in unincubated holding nests with either ambient or increased water on eggshells. Second, we added water to eggshells
in naturally partially incubated nests. We compared microbial growth on shells during a 5-day experimental period and found
that, as predicted, both unincubated groups had higher microbial growth than naturally partially incubated controls, and that
only in the absence of incubation did wetted eggs have higher microbial growth than unwetted eggs. Thus, we have shown that
water increases microbial growth on eggshells and that incubation nullifies these effects, suggesting that removal of water
from egg surfaces is one proximate mechanism for the antimicrobial effects of incubation. 相似文献