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Herbicides of the chlorinated phenoxyalkanoic acid group like 2,4-D, 2,4-DP and MCPP, belong to the most commonly used pesticides. This is also true for the Land Brandenburg. Therefore, this substance group was integrated in the current state monitoring programme for ground and surface water quality. Starting in 2001, the analysis was carried out complying with DIN 38407-20 by gas chromatography and mass spectrometric detection after enrichment with solid phase extraction and following derivatization with diazomethane-forming methyl esters. Quantifying 2,4-D considering selected ions in a surface water sample from the river Oder, a remarkable peak pattern was observed. A second peak with identical spectrum was found about 0.7 minutes earlier than the 2,4-D calibrated peak. Its intensity suggested a concentration 10–20 fold higher than the 2,4-D level. This unknown peak was identified as 2,6-D which is a structure isomer of the herbicide 2,4-D. This substance has not been described in literature or chemical substance databases known to us yet. Structure isomers have been found in other samples too. We suppose that the chlorinated phenoxyalkanoic acids chlorinated in the 6-position of the phenyl ring are formed as a technical by-product and show a higher persistance than the commonly known agents. 相似文献
105.
Evaluation of factors influencing soluble microbial product in submerged MBR through hybrid ASM model 总被引:1,自引:0,他引:1
Fangyue Li Joachim Behrendt Knut Wichmann Ralf Otterpohl 《Frontiers of Environmental Science & Engineering in China》2009,3(2):226-235
In this study, a mathematical model was established to predict the formation of the soluble microbial product (SMP) in a submerged
membrane bioreactor. The developed model was calibrated under the reference condition. Simulation results were in good agreement
with the measured results under the reference condition. The calibrated model was then used in the scenario studies to evaluate
the effect of three chosen operating parameters: hydraulic retention time (HRT), dissolved oxygen concentration, and sludge
retention time (SRT). Simulation results revealed that the SMP dominated the soluble organic substances in the supernatant.
The scenario studies also revealed that the HRT can be decreased to 1 h without deteriorating the effluent quality; dissolved
oxygen concentration in the reactor can be kept at 2–3 mg/L to maintain the effluent quality, reduce the content of SMP, and
minimize operating costs; the optimal SRT can be controlled to 10–15 d to achieve complete nitrification process, less membrane
fouling potential, and acceptable organic removal efficiency. 相似文献
106.
Daria Schurmann Jana Collatz Steffen Hagenbucher Joachim Ruther Johannes L. M. Steidle 《Die Naturwissenschaften》2009,96(3):383-391
Associative learning of host-associated chemical cues was studied in Nasonia vitripennis, a parasitoid of fly pupae in nests of hole-nesting birds. When females encountered a fly pupa and performed one sequence
of host recognition behaviour including drilling the ovipositor into the host in the presence of the artificial odour furfurylheptanoate
(FFH), they were afterwards arrested by FFH in olfactometer experiments. The response vanished after 4 days and could be blocked
after 3 days by feeding wasps with ethacrynic acid prior and after the training. This indicates the formation of an intermediate
form of memory by one host experience in N. vitripennis. Interestingly, the trained wasps avoided odours that were not present during the host encounter, although naive wasps did
not react to these odours. This unique behaviour probably causes wasps to focus during host searching on those chemical cues
they have experienced in the host environment. Studies in nests of hole-nesting birds revealed that about 30% of all nests
contained only one fly pupa, and laboratory studies showed that N. vitripennis females are able to parasitise around 100 fly pupae in their life. It is discussed that under these conditions, the formation
of a non-permanent intermediate memory for host-associated odours after one host encounter is adaptive to avoid costs involved
with formation and maintenance of memory for misleading cues. The demonstration of associative olfactory learning in N. vitripennis, the first parasitoid species with sequenced genome, opens the gate to study molecular mechanisms of memory formation and
its ecological adaptation in parasitoids. 相似文献
107.
Giovannangelo ME Gehring U Nordling E Oldenwening M van Rijswijk K de Wind S Hoek G Heinrich J Bellander T Brunekreef B 《Environment international》2007,33(1):9-16
BACKGROUND: Mold growth is believed to be one causative factor underlying the association between dampness in buildings and increased respiratory morbidity. Measurements of beta(1-->3)-glucans and fungal extracellular polysaccharides (EPS) are used as markers of mold exposure in field studies. Little is known about their levels and determinants in homes. OBJECTIVE: To study levels and determinants of beta(1-->3)-glucan and EPS levels in mattress and living room floor dust in three European countries. METHODS: Mattress and living room floor dust was collected in the homes of 1065 German, Dutch, and Swedish (pre-)school children. All samples were analyzed for beta(1-->3)-glucans and EPS in one central laboratory. Determinants were assessed by questionnaire. RESULTS: Amounts of dust, EPS and beta(1-->3)-glucan levels differed between countries. Amounts of dust, beta(1-->3)-glucan and EPS levels for mattresses were only weakly correlated with those for living room floors. Floor dust beta(1-->3)-glucan loads, EPS loads and EPS concentrations were strongly correlated with the amount of dust sampled, which is largely determined by the type of floor that was sampled (carpeted floors had 5-20 higher amounts of dust). None of the other determinants was consistently and statistically significantly associated with amounts of dust, beta(1-->3)-glucan and EPS concentrations on floors and mattresses. CONCLUSION: Mattress dust and floor dust are two different measures of exposure to the investigated mold components. Living room floor beta(1-->3)-glucan and EPS loads and EPS concentrations are largely determined by the type of floor sampled. Differences between countries can only partly be explained by the determinants studied. 相似文献
108.
Bishawjit Mallick Khan Rubayet Rahaman Joachim Vogt 《Mitigation and Adaptation Strategies for Global Change》2011,16(6):629-648
This paper aimed at to explore the consequences of cyclone victims due to unavailability of infrastructural supports and to
prop up the recognition that the infrastructure has a vital role to play in societies’ resilience during catastrophic situation.
The paper begins with a review of the science regarding climate change impact and cyclone disaster in Bangladesh. It emphasizes
the consequences of cyclone Aila in a selected coastal community in the remote coastal area. A field survey was conducted
by authors during March-August 2009. Eight available infrastructures were selected for this analysis. Uniformity of distribution
(R), demand index (Di) and degree of demand (DD) of the selected infrastructures were calculated by using nearest neighbourhood
methods of analysis. Results show that based on its specific planning standards none of the selected infrastructure can support
50% of the total population. Accordingly, it was observed that 76% respondent could not reach in safer place due to rush of
water intrusion and also because of the inundation of road-network. The nearness to the available cyclone shelter, and place
of taking shelter during cyclone is positively correlated (r = 0.38; p < 0.001). However, the poor people had less opportunity to take shelter in cyclone shelters, although none of the respondents
groups whose monthly income is above 75 USD stands without any infrastructural support. Such important observation may hint
the influence of local elites on the local disaster mitigation planning practice in Bangladesh. Almost 90% of the respondents
claimed that they had no access to enter the available cyclone shelter. Furthermore, the damaged infrastructures added more
hindrances during post disaster activities and also increased the sufferings of the victims. If there were adequate cyclone
shelters or rehabilitation centre, the affected people could take shelter and continue other works temporarily. Results drawn
from this research will be useful for local and national level planners, as well as international donors for future disaster
mitigation planning in the studied area and the methodology can be applied in similar countries and geographical territories. 相似文献
109.
Heidelore Fiedler Mohammad Sadia Thomas Krauss Abeer Baabish Leo W.Y. Yeung 《Frontiers of Environmental Science & Engineering》2022,16(10):132
110.
Polychlorinated dibenzo‐p‐dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) represent a class of tricylic, almost planar, aromatic ethers with 1 to 8 chlorine atoms. Congeners with substituents in the positions 2, 3, 7, and 8 are of special concern due to their toxicity, stability, and persistence. These compounds have been identified in almost all environmental compartments and humans. Dioxins are a potent carcinogen for animals and—at the moment—considered a probable carcinogen for humans. Actual toxicological risk assessment for humans are based on 2,3,7,8‐Cl4DD carcinogenicity studies on rodents. Tumorigenic effects were found for 2 strains of rats and 2 strains of mice. All dioxins and furans elicit common toxic and biological responses, starting with a specific binding to a protein receptor, but existing epidemiologic data do not provide definitive data on human health effects. Toxicity equivalency factors (TEFs) have been developed by several agencies as a provisional method of risk assessment for complex mixtures of PCDD/PCDF. Dioxins have never been produced intentionally and have never served any useful purpose. They are formed in trace amounts as by‐products in industrial processes; for instance within the chemical industry, of the pulp and paper industry, metallurgical processes, processes for reactivation of granular carbon, dry cleaning, and the manufacture of flame‐retarded plastics. The main pathway for dioxins to enter the environment is via combustion processes. Incineration is of special importance since PCDD/PCDF are directly released to the atmosphere from either stationary sources, such as municipal, hazardous and hospital waste incinerators, the combustion of sewage sludge, and scrap metal recycling, or diffuse sources, e.g. automobile exhausts, private home heating with fossil fuels, forest fires, and cigarette smoking. Furthermore, fires with PCB and PVC have additionally contributed to the total dioxin load. The emission gases can undergo long‐range transport, so that dioxins have been found even in remote areas. Besides the two primary sources (industrial processes and combustion processes) the release of dioxins from contaminated areas and waste dumps via the leachate and the application of sewage sludge for fertilization represents a third source of PCDD/PCDF. After more than 10 years of dioxin research the most important sources of PCDD/PCDF have been identified and analytical methods have been developed for their quantification in trace levels and in complex matrices. Various efforts have been undertaken to reduce the emission of dioxins: for example, optimization of combustion processes for municipal waste incineration, use of unleaded gasoline, ban of chemicals, such as polychlorinated biphenyls (PCBs) and pentachlorophenol (PCP). More detail is provided in the pulp and paper section where changes have been initiated to significantly reduce the sources of PCDD/PCDF. However, relatively little is known about transport and transformation processes, so only rough estimates can be made. Photodegradation has been found to be the primary process for 2,3,7,8‐Cl4DD breakdown. A half‐life of 3–4 days has been estimated for photochemical degradation under oxidative conditions. Field studies on the fate of 2,3,7,8‐Cl4DD in soil gave a half‐life of 9.1 (Seveso) and 12 years (under special conditions: sand, erosion), respectively. Biodegradation seems to be negligible. Transfer factors soil‐plants for PCDD/PCDF have been determined—with a high degree of uncertainty—to be less than 0.1. Human exposure primarily occurs via ingestion whereas inhalation is a minor pathway. Dermal absorption can be neglected although skin contact to polluted surfaces may occur. Due to the lipophilicity of PCDD/PCDF and their potential for accumulation, foods such as meat and especially dairy products contribute most to the dioxin body burden of humans. Both national agencies and international organizations have recognized the significance of this problem and as a result have initiated regulations, recommendations and research programmes (1) to understand where and how PCDD/PCDF are formed, (2) to reduce their impact on the environment and to humans, and (3) to start remedial action on contaminated areas. 相似文献