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排序方式: 共有271条查询结果,搜索用时 265 毫秒
171.
Hofer N Alexou M Heerdt C Löw M Werner H Matyssek R Rennenberg H Haberer K 《Environmental pollution (Barking, Essex : 1987)》2008,154(2):241-253
The effect of free-air ozone fumigation and crown position on antioxidants were determined in old-growth spruce (Picea abies) trees in the seasonal course of two consecutive years (2003 and 2004). Levels of total ascorbate and its redox state in the apoplastic washing fluid (AWF) were increased under double ambient ozone concentrations (2xO3), whilst ascorbate concentrations in needle extracts were unchanged. Concentrations of apoplastic and symplastic ascorbate were significantly higher in 2003 compared to 2004 indicating a combined effect of the drought conditions in 2003 with enhanced ozone exposure. Elevated ozone had only weak effects on total glutathione levels in needle extracts, phloem exudates and xylem saps. Total and oxidised glutathione concentrations were higher in 2004 compared to 2003 and seemed to be more affected by enhanced ozone influx in the more humid year 2004 compared to the combined effect of elevated ozone and drought in 2003 as observed for ascorbate. 相似文献
172.
Haberer K Jaeger L Rennenberg H 《Environmental pollution (Barking, Essex : 1987)》2006,139(2):224-231
In the present field study the role of ascorbate in scavenging the harmful atmospheric trace gases O3 and NO2 was examined. For this purpose ascorbate contents were determined in needles of adult Scots pine trees (Pinus sylvestris L.) during three consecutive years. Ascorbate contents were correlated with ambient tropospheric O3 and NO2 concentrations and with meteorological parameters. The results showed a strong correlation of atmospheric O3 but not of atmospheric NO2 concentrations with the apoplastic content of ascorbate during the seasonal course. Ascorbate contents in needle extracts did not correlate with ambient trace gas concentrations. In the apoplastic space, but not in needle extracts ascorbate contents correlate highly significantly with global radiation. From these results it is assumed that apoplastic ascorbate in Scots pine needles is adapted to the actual atmospheric O3 concentration to mediate immediate detoxification of O3, while the atmospheric O3 concentration itself is largely dependent on light intensity. 相似文献
173.
Fabrice Helfenstein Murielle Podevin Heinz Richner 《Behavioral ecology and sociobiology》2010,64(4):557-565
Sperm competition exerts strong selection on males to produce spermatozoa with an optimal morphology that maximizes their
fertilization success. Long sperm were first suggested to be favored because they should swim faster. However, studies that
investigated the relationship between sperm length and sperm competitive ability or sperm swimming velocity yielded contradictory
results. More recently, ratios of the different sections of a spermatozoon (the head, midpiece, and flagellum) were suggested
to be more crucial in determining swimming velocity. Additionally, sperm ability to remain and survive in the female storage
organs may also influence fertilization success, so that optimal sperm morphology may rather maximize sperm longevity than
velocity. In this study, we investigated how sperm morphology is related to sperm velocity and sperm longevity in the house
sparrow Passer domesticus. Sperm velocity was found to be correlated with head/flagellum ratio. Sperm with small heads relative to their flagellum showed
higher swimming velocity. Additionally, shorter sperm were found to live longer. Finally, we found sperm morphological traits
to vary substantially within males and the head/flagellum ratio to be unrelated to total sperm length. We discuss the hypothesis
that the substantial within-male variation in sperm morphology reflects a male strategy to produce a diversity of sperm from
long, fast-swimming to short, long-living sperm to maximize their fertilization success in a context of sperm competition. 相似文献
174.
Tamas Komives Gabor Gullner Heinz Rennenberg John E. Casida 《Water, Air, & Soil Pollution: Focus》2003,3(3):277-283
The ability of poplar trees to resist chemical stress caused by chloroacetanilide herbicides was studied. Detached leaves of Lombardy poplar (Populus nigra L.) were exposed to seven chloroacetanilide herbicides via uptake through the cut petiole. The leaves showed high tolerance against the phytotoxicity of these compounds. Their tolerance was further enhanced by treatment with 2-oxothiazolidine-4-carboxylic acid (OTC, a precursor of the amino acid cysteine). High levels of glutathione (GSH) and GSH S-transferase (GST) activity were detected in poplar leaves. Treatments with chloroacetanilide herbicides left the GSH content in the leaves unchanged but strongly induced the GST activity. In contrast, in OTC-treated leaves increased GSH contents were measured, but GST activities remained unchanged. It therefore appears that a highly active and inducible GSH-conjugation Phase II detoxification system in their leaves may make poplar trees useful for phytoremediation of soils contaminated with chloroacetanilide herbicides. Based on these findings a phytoremediation project using different poplar hybrids at a site heavily polluted with such compounds in Hungary has been launched. 相似文献
175.
Schröder HC Brandt D Schlossmacher U Wang X Tahir MN Tremel W Belikov SI Müller WE 《Die Naturwissenschaften》2007,94(5):339-359
Biomineralization, biosilicification in particular (i.e. the formation of biogenic silica, SiO2), has become an exciting source of inspiration for the development of novel bionic approaches following “nature as model”.
Siliceous sponges are unique among silica forming organisms in their ability to catalyze silica formation using a specific
enzyme termed silicatein. In this study, we review the present state of knowledge on silicatein-mediated “biosilica” formation
in marine sponges, the involvement of further molecules in silica metabolism and their potential application in nanobiotechnology
and medicine.
Werner E. G. Müller dedicated this study to Prof. Vera Gamulin (Rudjer Boskovic Institute, Zagreb, Croatia) in honour of her
unique contributions in molecular evolution. 相似文献
176.
Heinz L. Engelbrecht 《Environment international》1981,6(1-6)
Dust build-up on adjacent surfaces is often an unwanted effect in industrial processes handling pulverized materials. In the case of electrostatic precipitation, build-up of dust on the collecting surface is the purpose of the process. Removal of this build-up is sometimes difficult, but necessary to maintain the continuity of the process. Dry-process methods for dust removal include rapping by impact.It is the intent of this paper to provide information on the general subject of dust removal from plates, on rapping systems used in electrostatic precipitators, and on measurements and order of magnitude of rapping forces.Rapping acceleration test results obtained in the laboratory are expanded to cover full-scale collecting surface plates.Effects of plate design, plate height and length, method of support, rapping, hammer weight, and lift are analyzed. 相似文献
177.
178.
Heinz P. Kollig 《Chemosphere》1985,14(11-12)
An experiment was conducted to investigate the variability in biotransformation rate coefficients of a xenobiotic, the butoxyethyl ester of 2,4-
, in natural waters between aufwuchs grown on Teflon strips located on the bottom and at the water surface of a pond and a river. The colonized strips and the natural waters were transported to the laboratory where the biotransformation studies were done under controlled conditions. Statistical analyses applied to the first-order rate coefficients showed a significant difference between bottom and surface aufwuchs for the river only. For both pond and river, a significant difference was shown when the aufwuchs was suspended, however. The aufwuchs mat thickness was significantly different between bottom and surface for the pond but not for the river and the biomass as ash-free dry weight was significantly different for both water bodies. The variability of biomass and first-order rate coefficients was higher with the bottom colonized aufwuchs than with the surface colonized aufwuchs. 相似文献
179.
180.
The combustion of municipal solid waste leads to emissions containing high contents of heavy metals and organic pollutants. These residues, mainly collected by the electrostatic precipitator, have either to be deposited in special waste dumps or treated before being disposed in ordinary landfills. For the treatment or partial recycling of these residues the composition and the related variation are of primary importance. In this context a national inquiry for analysis data about fly ash composition was started. The results of this study, completed by own analytical results are presented in this paper. 相似文献