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171.
This study investigates the stabilization of As in the contaminated sludge after treatment with MnO(2) or Ca(OH)(2), and the influence of the stabilizing materials on the leachability of the co-existing elements Pb and Zn. By exploiting a continuous-flow assembly facilitating a modified Wenzel's sequential extraction scheme (designed for the fractionation of arsenic), it is possible to ascertain the leachability, mobility and fractional alteration of these elements under stimulated natural (flow-through) leaching conditions. The fractionation data show that more than 80% of As, Pb and Zn in the untreated sludge are bound in the amorphous Fe oxides fraction and residual fraction. The addition of MnO(2) has only an insignificant effect on As fractional transformation, while Ca(OH)(2) caused an increase in As mobility. For Pb, the decrease in leachability was clearly visible. The extractable Pb was reduced by 18% and 40% in stabilized MnO(2) and Ca(OH)(2) sludge samples, respectively. Unlike that of Pb, the mobility of Zn was not affected by the additives used. Their fractional distribution patterns before and after the stabilization process remained the same. The ability to produce detailed leaching profiles for As and other elements (Pb, Zn, Ca, Mn and Fe) meant that elemental associations in individual fractions could be examined. From the MnO(2)-treated sludge, the coincidence of the As, Pb, Zn, Fe, and Mn peaks seems to indicate a close association of these elements in the Fe-oxides-bound fraction. Furthermore, the leaching profiles may be used as evidence of a strong affinity between these elements and added MnO(2). 相似文献
172.
Birgit Reger Patrick Sheridan Dietmar Simmering Annette Otte Rainer Waldhardt 《Environmental management》2009,43(6):1026-1038
Farmland habitat diversity in marginal European landscapes changed significantly in the past decades. Further changes toward
homogenization are expected, particularly in the course of European agricultural policy. Based on three alternative transfer
payment schemes, we modeled spatially explicit potential effects on the farmland habitat diversity in a marginal European
landscape. We defined (1) a scenario with direct transfer payments coupled to production, (2) a scenario with direct transfer
payments decoupled from production, and (3) a scenario phasing out all direct transfer payments. We characterized habitat
diversity with three indices: habitat richness, evenness, and rarity. The habitat pattern in 1995 served as reference for
comparison. All scenarios predicted a general trend of homogenization of the farmland habitat pattern, yet to a differing
extent. Transfer payments coupled to production (Scenario 1) favored the abandonment of agricultural production, particularly
in low-productive areas and arable land use in more productive areas. Habitat richness and habitat evenness had intermediate
values in this scenario. Decoupling transfer payments from production (Scenario 2) supported grassland as most profitable
farming system. This led to a grassland-dominated landscape with low values of all habitat diversity indices. Phasing out
transfer payments (Scenario 3) resulted in complete abandonment or afforestation of agricultural land and extremely low values
in all habitat diversity indices. Scenario results indicate that transfer payments may prevent cessation of agricultural production,
but may not counteract homogenization in marginal landscapes. Conserving high farmland habitat diversity in such landscapes
may require support schemes, e.g., Pillar Two of EU Common Agricultural Policy. 相似文献
173.
Anhand des Anwendungsbeispiels einer bewohnten Altlast wird eine probabilistische Expositionsabsch?tzung durchgeführt und es werden M?glichkeiten aufgezeigt, Variabilit?t und Unsicherheit in der Sch?tzung separat zu erfassen. Zur Charakterisierung der Variabilit?t personenspezifischer Variablen (z.B. K?rpergewicht) werden in das Expositionsmodell Wahrscheinlichkeitsverteilungen eingesetzt; die stoffspezifischen Expositionsparameter werden konstant gehalten. Zus?tzlich wird die Ungewi?heit einer ausgew?hlten Variablen (Bodeningestionsrate) modelliert. Der Vergleich mit denworst-case-Sch?tzungen zeigt, da? diese in den oberen Randbereichen bzw, au?erhalb der Bereiche der probabilistischen Sch?tzung liegen und somit sehr konservative, u.U. unrealistische Sch?tzungen liefern. 相似文献
174.
175.
Die aus der chemischen Umsetzung mit endogenen Molekülen resultierende biologische Wirkung von Fremdstoffen wird diskutiert,
ausgehend von den Grunds?tzen der Thermodynamik und Kinetik. Dabei führt ein unter vereinfachenden Annahmen durchgeführter
Vergleich der thermischen Energieverteilung von Molekülen mit typischen biochemischen Aktivierungsenergien zu dem Ergebnis,
da? aus statistischen Gründen für jede mit stofflichen Umsetzungen zusammenh?ngende biologische Wirkung ein Schwellenwert
existieren sollte. 相似文献
176.
177.
Christian Steinberg Markus Haitzer Sebastian Höss Renate Lorenz Rainer Brüggemann B. Kent Burnison 《Environmental Sciences Europe》1997,9(2):64-68
Humic substances, in aqueous bodies primarily fulvic acids, may demonstrate an inhibitory as well as an activating influence on organisms. We present evidence with bacteria-containing algal cultures and with cultures of the nematodeCaenorhabditis elegans. Structural elements of the fulvic acids which may be responsible for such effects are not yet known. Furthermore, the presence of fulvic acids may lead to increases in bioconcentration of xenobiotics. Increase in the toxicity of xenobiotics in the presence of humic substances have also been described. We present studies applying lethal as well as sublethal toxicity endpoints. 相似文献
178.
由以往和化学品安全相关的国际活动发展而来的国际化学品管理战略(SAICM)得到了联合国环境署(UNEP)理事会的支持.全球化学品行业认为SAICM应该被作为实现世界可持续发展首脑会议议定目标的路线图.全球在化学品安全使用问题上的不断进步将要求生产者、销售者、使用者、政府和其他利益相关方在生产链各有关环节责任分担的基础上采取共同协调的行动.从这个意义上说,制定一个全球战略提供了通过建立新的伙伴关系来实现化学品安全的机会.但是,如果SAICM成为国家、地区和国际层面附加的更严格的调控手段的基础,则其可能达不到期望的影响. 相似文献
179.
Flow and diffusion of water in natural porous media, quartz sand, and calcareous gravel were measured using a 1.5-T clinical magnetic resonance tomograph. The spatial resolution of the dynamic measurements was 1.32 x 1.32 x 5 mm3, and the time between two cross-sectional measurements was approximately 10 s. The measured coefficients of molecular diffusion for water were in good agreement with theoretical data. Flow was measured without any tracer at velocities between 0.15 and 6.67 mm/s. The results, based on a calibration within one part of the column, were in good agreement with data obtained from a tracer experiment and from a numerical model. It was possible to measure the flow velocity in larger pores and preferential flow paths directly. The results of the flow measurements in smaller pores reflected the mean velocity within that volume element. In that case the obtained values were close to the average linear velocity. Since the time resolution is high a monitoring of flow processes is possible. The pore space was imaged with a spatial resolution of 0.5 x 0.5 x 0.5 mm3. Here, the porosity of pores that are larger than 0.2 mm can be measured directly; for smaller pores a calibration is necessary. 相似文献
180.
Linking socio-economic factors, environment and land cover in the German Highlands, 1945-1999 总被引:4,自引:0,他引:4
Land-cover changes are caused by human activities and natural ecological processes. Thus, our study uses an interdisciplinary approach to research land-cover changes. We present a method to (i) link socio-economic/environmental factors and land-cover changes, (ii) identify indicators of land-cover changes, and (iii) distinguish between socio-economic and environmental indicators associated with local types of overall land-cover changes. The study was conducted in the Lahn-Dill Highlands, Germany, a typical marginal rural landscape. In this region, we investigated land-cover changes occurring over the period 1945-1999. Land-cover data were derived from multi-temporal aerial photographs. Types of overall land-cover changes characterising the districts within the study area were differentiated. With the help of redundancy analysis (RDA), we analysed the relationships between land-cover changes and widely available socio-economic/environmental factors. The results reveal that both individual land-cover changes at patch level and types of overall land-cover changes characterising districts are correlated with socio-economic and environmental factors. Whereas the stable environmental factors are drivers of land-cover changes in our rural study area, socio-economic factors introduced into the analysis mostly result from land-cover changes. We identified correlative socio-economic indicators that cannot explain land-cover changes, but that in combination with the environmental factors can be used to greatly facilitate the reconstruction of past land-cover changes and thus lead to a better knowledge of land-cover history. Based on the types of overall land-cover changes, the results of the study can be adopted for the study of land-cover changes in other regions. 相似文献