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71.
Audrey Athlan Christian Braud Michel Vert 《Journal of Polymers and the Environment》1997,5(4):243-247
Oligomers of poly(3-hydroxybutyric acid) (P(3-HB)) were prepared by partial degradation of high molecular weight P(3-HB) dissolved
in 1,2-dichloroethane/water mixture in the presence of p-toluene sulfonic acid (p-TSA). The water-soluble fraction of the
resulting oligomers was extracted from the mixture with neutral sodium phosphate buffer. Capillary zone electrophoresis showed
that the aqueous extracts were composed of two series of oligomers. The first one was composed of one to seven P(3-HB) oligomers
(O(3-HB)). In contrast, the second series was composed of four oligomers characterized by the presence of a terminal C=C bond
[O’(3-HB)]. Both series of oligomers behaved differently insofar as their fate in aqueous medium was concerned. The 0(3-HB)
compounds were stable over a period of 2 months. On the other hand, the population of the O’(3-HB) oligomers varied, the proportion
of oligomers increasing with aging time. 相似文献
72.
Audrey E. McGowin Laura L. Kinner Stanley E. Manahan
David W. Larsen
《Chemosphere》1991,22(12):1191-1209The ChemChar reverse-burn gasification process was evaluated to determine its feasibility for use in the regeneration of spent activated carbon. This non-incinerative, thermochemical gasification process pyrolyzes the sorbed wastes and restores the sorptive capacity of the carbon in one energy-efficient step. The effects of moisture and supplemental fuel addition on regeneration were determined with a laboratory-scale reactor and a flow-through assay method was developed for determining regeneration effectiveness. The process produces good quality regenerated carbon simply and inexpensively with a minimum of carbon loss. Carbons can be regenerated several times and the method is non-polluting. 相似文献
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77.
Valve activity rhythm of the oyster Crassostrea gigas is mainly driven by tides in the field, but in the laboratory, only a circadian clock mechanism has been demonstrated. In an attempt to reconcile these results, the mechanisms underlying the circatidal rhythm were studied in the laboratory under different entrainment or free-running regimes and in the field at Arcachon (44°39′N/1°09′W) in February–April 2011). Results confirm the existence of a circadian clock in C. gigas. Under entrainment regimes (12-h dark/12-h light photoperiod and tidal cycles simulated by a reversing current flow), oysters exhibited both circadian and circatidal cycles. Under free-running conditions (e.g., continuous darkness), the endogenous rhythm appeared to be circadian. There was no experimental evidence for an endogenous circatidal rhythm, even in oysters just transferred from the field, where a clear tidal cycle was expressed. There are two possible mechanisms to explain tidal behavior in C. gigas: an exogenous tidal cue that drives tidal activity and masks the circadian rhythm and an endogenous circatidal clock that is sensitive to tidal zeitgebers and runs at tidal frequency. 相似文献
78.
Andréanne Lessard Audrey Bourret Marc Bélisle Fanie Pelletier Dany Garant 《Behavioral ecology and sociobiology》2014,68(5):733-742
Evaluating the contribution of individual and environmental determinants of reproductive success is essential to improve our understanding of sexual selection. In socially monogamous bird species with high rates of extrapair paternity, traits or environmental contexts affecting the number of within-pair young (WPY) produced by males can differ from those affecting the number of extrapair young fathered (EPY). Here, we use a 4-year dataset collected in contrasted environments to assess the factors affecting male reproductive success in tree swallows (Tachycineta bicolor), a species showing high levels of extrapair paternity. Our analyses revealed that the number of WPY was higher under better environmental conditions, while the number of EPY was mainly related to male characteristics. Males nesting in more intensive agricultural areas had fewer WPY produced and a lower reproductive success. Also, males breeding earlier in the season had more WPY. The presence of parasites reduced males’ reproductive success, mainly by reducing the number of EPY. The influence of male phenotype varied according to population density: Tarsus length variation had a greater effect on reproductive success at low population density than at high density, while wing length was also positively related to the number of EPY, more so at high than at low density. Altogether, our results suggest a complex interplay between individual and environmental determinants of reproductive success and imply that sexual selection dynamics varies depending on environmental contexts. 相似文献
79.
The authors look at Britain's post‐war response to the challenge of the Inner Cities and attempts to account for this response's more obvious failings. The paper considers the challenge facing the planners and considers the nature of their response, concluding that the future of planning as a weapon in the armoury of public policy is assured. 相似文献
80.
A fundamental property of most animals is the ability to see whether an object is approaching on a direct collision course
and, if so, when it will collide. Using high-density electroencephalography in 5- to 11-month-old infants and a looming stimulus
approaching under three different accelerations, we investigated how the young human nervous system extracts and processes
information for impending collision. Here, we show that infants’ looming related brain activity is characterised by theta
oscillations. Source analyses reveal clear localised activity in the visual cortex. Analysing the temporal dynamics of the
source waveform, we provide evidence that the temporal structure of different looming stimuli is sustained during processing
in the more mature infant brain, providing infants with increasingly veridical time-to-collision information about looming
danger as they grow older and become more mobile. 相似文献