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121.
122.
Ziel dieser Untersuchung war die Beantwortung der Frage, in wieweit mit Hilfe der Messung der Radioaktivit?t von Umweltisotopen
eine Aussage zum Alter von Einzelproben des Gew?ssersediments m?glich ist. Voraussetzung ist, da? die Sedimente n?herungsweisegleichf?rmig abgelagerte Schwebstoffe sind, und sei es auch nur in gewissen Zeitabschnitten (Zeitfenstern). Proben chaotisch wechselnder Sedimentation und Erosion
sind z.Zt. nicht beurteilbar im Hinblick auf ihr Alter.
Folgerung aus den Messungen von Umweltisotopen: Die Einzelproben werden mitReferenzschwebstoffen der 0 bis 38 μm Feinkornfraktion hinsichtlich ihrer Radioaktivit?tskonzentration verglichen. Dann werden sie grob in vier Altersklassen
eingeteilt:
相似文献
– | -überwiegend aktuelle Sedimente (seit etwa dem letzten Hochwasser) |
– | -überwiegende Anteile um das Jahr 1986 |
– | -überwiegende Anteile um die 60er Jahre |
– | -überwiegende Anteile vor 1955 (und Gew?sserboden) |
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In addition to heat production on the comb surface, honeybee workers frequently visit open cells (“gaps”) that are scattered
throughout the sealed brood area, and enter them to incubate adjacent brood cells. We examined the efficiency of this heating
strategy under different environmental conditions and for gap proportions from 0 to 50%. For gap proportions from 4 to 10%,
which are common to healthy colonies, we find a significant reduction in the incubation time per brood cell to maintain the
correct temperature. The savings make up 18 to 37% of the time, which would be required for this task in completely sealed
brood areas without any gaps. For unnatural high proportions of gaps (>20%), which may be the result of inbreeding or indicate
a poor condition of the colony, brood nest thermoregulation becomes less efficient, and the incubation time per brood cell
has to increase to maintain breeding temperature. Although the presence of gaps is not essential to maintain an optimal brood
nest temperature, a small number of gaps make heating more economical by reducing the time and energy that must be spent on
this vital task. As the benefit depends on the availability, spatial distribution and usage of gaps by the bees, further studies
need to show the extent to which these results apply to real colonies.
M. Fehler and M. Kleinhenz contributed equally to this work. 相似文献
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127.
H Paskerová K Hilscherová L Bláha 《Environmental science and pollution research international》2012,19(6):2024-2037
Cyanobacterial blooms represent a serious threat to the aquatic environment. Among other effects, biochemical markers have been studied in aquatic vertebrates after exposures to toxic cyanobacteria. Some parameters such as protein phosphatases may serve as selective markers of exposure to microcystins, but under natural conditions, fish are exposed to complex mixtures, which affect the overall biomarker response. This review aims to provide a critical summary of biomarker responses in aquatic vertebrates (mostly fish) to toxic cyanobacteria with a special focus on detoxification and oxidative stress. Detoxification biomarkers such as glutathione (GSH) and glutathione-S-transferase (GST) showed very high variability with poor general trends. Often, stimulations and/or inhibitions and/or no effects at GSH or GST have been reported, even within a single study, depending on many variables, including time, dose, tissue, species, etc. Most of the oxidative stress biomarkers (e.g., superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase) provided more consistent responses, but only lipid peroxidation (LPO) seemed to fulfill the criteria needed for biomarkers, i.e., a sufficiently long half-life and systematic response. Indeed, reviewed papers demonstrated that toxic cyanobacteria systematically elevate levels of LPO, which indicates the important role of oxidative damage in cyanobacterial toxicity. In summary, the measurement of biochemical changes under laboratory conditions may provide information on the mode of toxic action. However, comparison of different studies is very difficult, and the practical use of detoxification or oxidative stress biomarkers as diagnostic tools or early warnings of cyanobacterial toxicity is questionable. 相似文献
128.
Zapletal M Cudlín P Chroust P Urban O Pokorný R Edwards-Jonášová M Czerný R Janouš D Taufarová K Večeřa Z Mikuška P Paoletti E 《Environmental pollution (Barking, Essex : 1987)》2011,159(5):1024-1034
Daily ozone deposition flux to a Norway spruce forest in Czech Republic was measured using the gradient method in July and August 2008. Results were in good agreement with a deposition flux model. The mean daily stomatal uptake of ozone was around 47% of total deposition. Average deposition velocity was 0.39 cm s−1 and 0.36 cm s−1 by the gradient method and the deposition model, respectively. Measured and modelled non-stomatal uptake was around 0.2 cm s−1. In addition, net ecosystem production (NEP) was measured by using Eddy Covariance and correlations with O3 concentrations at 15 m a.g.l., total deposition and stomatal uptake were tested. Total deposition and stomatal uptake of ozone significantly decreased NEP, especially by high intensities of solar radiation. 相似文献
129.
Landscape multifunctionality: a powerful concept to identify effects of environmental change 总被引:2,自引:0,他引:2
Janine Bolliger Michèle Bättig Justus Gallati Andreas Kläy Michael Stauffacher Felix Kienast 《Regional Environmental Change》2011,11(1):203-206
The interdisciplinary concept of landscape multifunctionality provides a suitable platform to combine or disentangle effects
of multiple environmental stressors acting on the landscape. The concept allows mapping of trade-offs, synergies, and priority
conflicts between individual landscape functions, thus providing easily accessible, hands-on means to communicate findings
of environmental research to decision makers and society. This rapid communication provides an overview of current developments
and potential future research avenues in landscape multifunctionality. 相似文献
130.
Haeba MH Hilscherová K Mazurová E Bláha L 《Environmental science and pollution research international》2008,15(3):222-227
BACKGROUND, AIM AND SCOPE: Pollution-induced endocrine disruption in vertebrates and invertebrates is a worldwide environmental problem, but relatively little is known about effects of endocrine disrupting compounds (EDCs) in planktonic crustaceans (including Daphnia magna). Aims of the present study were to investigate acute 48 h toxicity and sub-chronic (4-6 days) and chronic (21 days) effects of selected EDCs in D. magna. We have investigated both traditional endpoints as well as other parameters such as sex determination, maturation, molting or embryogenesis in order to evaluate the sensitivity and possible use of these endpoints in ecological risk assessment. MATERIALS AND METHODS: We have studied effects of four model EDCs (vinclozolin, flutamide, ketoconazole and dicofol) on D. magna using (i) an acute 48 h immobilization assay, (ii) a sub-chronic, 4-6 day assay evaluating development and the sex ratio of neonates, and (iii) a chronic, 21 day assay studying number of neonates, sex of neonates, molting frequency, day of maturation and the growth of maternal organisms. RESULTS: Acute EC50 values in the 48 h immobilization test were as follows (mg/L): dicofol 0.2, ketoconazole 1.5, flutamide 2.7, vinclozolin >3. Short-term, 4-6 day assays with sublethal concentrations showed that the sex ratio in Daphnia was modulated by vinclozolin (decreased number of neonate males at 1 mg/L) and dicofol (increase in males at 0.1 mg/L). Flutamide (up to 1 mg/L) had no effect on the sex of neonates, but inhibited embryonic development at certain stages during chronic assay, resulting in abortions. Ketoconazole had no significant effects on the studied processes up to 1 mg/L. DISCUSSION: Sex ratio modulations by some chemicals (vinclozolin and dicofol) corresponded to the known action of these compounds in vertebrates (i.e. anti-androgenicity and anti-oestrogenicity, respectively). Our study revealed that some chemicals known to affect steroid-regulated processes in vertebrates can also affect sublethal endpoints (e.g. embryonic sex determination and/or reproduction) in invertebrates such as D. magna. CONCLUSIONS: A series of model vertebrate endocrine disrupters affected various sub-chronic and chronic parameters in D. magna including several endpoints that have not been previously studied in detail (such as sex determination in neonates, embryogenesis, molting and maturation). Evaluations of traditional reproduction parameters (obtained from the 21 day chronic assay). as well as the results from a rapid, 4-6 day, sub-chronic assay provide complementary information on non-lethal effects of suspected organic endocrine disrupters. RECOMMENDATIONS AND PERSPECTIVES: It seems that there are analogies between vertebrates and invertebrates in toxicity mechanisms and in vivo effects of endocrine disruptors. However, general physiological status of organisms may also indirectly affect endpoints that are traditionally considered 'hormone regulated' (especially at higher effective concentrations as observed in this study) and these factors should be carefully considered. Further research of D. magna physiology and comparative studies with various EDCs will help to understand mechanisms of action as well as ecological risks of EDCs in the environment. 相似文献