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81.
Optimization of exergy and implications of body sizes of phytoplankton and zooplankton in an aquatic ecosystem model 总被引:2,自引:0,他引:2
Size appears to be an important parameter in ecological processes. All physiological processes vary with body size ranging from small microorganisms to higher mammals. In this model, five state variables — phosphorus, detritus, phytoplankton, zooplankton and fish are considered. We study the implications of body sizes of phytoplankton and zooplankton for total system dynamics by optimizing exergy as a goal function for system performance indicator. The rates of different sub-processes of phytoplankton and zooplankton are calculated, by means of allometric relationships of their body sizes. We run the model with different combinations of body sizes of phytoplankton and zooplankton and observe the overall biomass of phytoplankton, zooplankton and fish. The highest exergy values in different combinations of phytoplankton and zooplankton size indicate the maximum biomass of fish with relative proportions of phytoplankton and zooplankton. We also test the effect of phosphorus input conditions corresponding to oligotrophic, mesotrophic, eutrophic system on its dynamics. The average exergy to be maximized over phytoplankton and zooplankton size was computed when the system reached a steady state. Since this state is often a limit cycle, and the exergy copies this behaviour, we averaged the exergy computed for 365 days (duration of 1 year) in the stable period of the run. In mesotrophic condition, maximum fish biomass with relative proportional ratio of phytoplankton, zooplankton is recorded for phytoplankton size class 3.12 (log V μm3 volume) and zooplankton size 4 (log V μm3 volume). In oligotrophic condition the highest average exergy is obtained in between phytoplankton size 1.48 (log V μm3 volume) and zooplankton size 4 (log V μm3 volume), whereas in eutrophic condition the result shows the highest exergy in the combination of phytoplankton size 5.25 (log V μm3 volume) and zooplankton size 4 (log V μm3 volume). 相似文献
82.
This paper describes an individual-based model, MORPH, that has been designed to predict the effect of environmental change on foraging animal populations. The key assumptions of MORPH are that individuals within populations behave in order to maximise their perceived fitness, but that perceived fitness may not always be positively related to the actual chances of survival and reproduction. MORPH has been parameterised for coastal birds on several European sites and predicted the effect of environmental change, caused by factors such as habitat loss, disturbance from humans and sea-level rise, on the survival and body condition of these species. However, MORPH contains a basic framework to describe animal physiology and foraging behaviour, and the distribution and abundance of the resources required by these animals. Therefore, MORPH is not restricted to coastal birds, and is potentially applicable to a wider range of systems. To be applied to a forager system, MORPH requires parameters describing (i) the distribution of the food supply and how food quality and abundance changes through time; (ii) the rate at which foragers consume food given the abundance of food and competitors; (iii) the amount of food the forager must consume each day to survive; (iv) the distribution and seasonal changes in other factors which influence the foraging behaviour and survival of foragers. The purpose of this paper is to (i) describe MORPH, (ii) give examples of its application, (iii) describe the types of systems to which MORPH can be applied, and (iv) publish its source code and a user guide. 相似文献
83.
Survival of dippers Cinclus cinclus in the wild was studied in relation to their dominance. Dominance was assessed amongst groups of temporary captives in a
laboratory arena. Adults tended to be more dominant than juveniles, and within age classes males generally dominated females.
Dominant individuals also sang more. Logistic regression was used to examine survival in the wild in relation to dominance
and other factors. Annual survival of juvenile males was negatively related to dominance during the previous autumn. No significant
effects of dominance on winter or annual survival were found amongst females or adult males. Dominance effects on overwinter
survival approached significance for adult females, however, and were significant for both winter and annual survival when
the data from adult females and juvenile males were combined. None of the other factors considered, which included body size,
song frequency and year, had a significant effect on overwinter or annual survival. We concluded that dominance either had
no influence on survival, or had a negative effect particularly on dippers of intermediate status. We were unable to show
if dominance had a direct effect, however, or acted indirectly on survival via an unidentified factor we did not examine.
Received: 23 June 1994/Accepted after revision: 28 October 1995 相似文献
84.
85.
Alexandre Roulin 《Die Naturwissenschaften》2009,96(3):375-382
Identifying the factors that mediate covariation between an ornament and other phenotypic attributes is important to determine
the signaling function of ornaments. Sign and magnitude of a covariation may vary across environments if the expression of
the ornament or of its linked genes regulating correlated phenotypes is condition-dependent. I investigated in the barn owl
Tyto alba whether sign and magnitude of covariation between body mass and two heritable melanin-based plumage ornaments change with
food supply, along the reproductive cycle and from the morning to the evening. Using a dataset of 1,848 measurements of body
mass in 336 breeding females, I found that females displaying large black spots were heavier than conspecifics with smaller
spots in the afternoon (i.e., a long time after the last feeding) but not in the morning (i.e., a short time after the last
feeding). This is consistent with the recently proposed hypothesis that eumelanin-based ornaments are associated with the
ability to maintain energy balance between food intake and energy expenditure. Thus, covariation between melanin-based coloration
and body mass can be detected only under specific conditions potentially explaining why it has been reported in only ten out
of 28 vertebrate species. The proposition that ornamented individuals achieve a higher fitness than drab conspecifics only
in specific environments should be tested for other ornaments. 相似文献
86.
K. Mohamed Ali B.W.C. Sathiyasekaran 《International journal of occupational safety and ergonomics》2013,19(3):319-325
Carpal Tunnel Syndrome (CTS) is an important problem among computer professionals. Hence the prevalence of CTS among computer professionals and risk factors were studied. 648 subjects were selected from 4,276 computer professionals from 21 companies with a simple random sampling method. CTS was diagnosed based on clinical features.The prevalence of CTS was found to be 13.1% (95% CI 10.5–15.7%). Subjects with over 8 years of computer work, over 12 hrs of work per day and system administrators were at a higher risk for CTS (OR 3.3, 4.9 and 2.5 respectively). Flexed or extended hand position had higher risk for CTS.Higher risk for CTS was found with higher exposure to computer work. Ergonomic considerations are important in facilitating proper positioning of hand while working with a computer. Further studies on CTS risk factors among computer professionals are essential for planning prevention. 相似文献
87.
Carotenoid pigments cannot be synthesized by vertebrates but must be ingested through the diet. As they seem to be a limited
resource, carotenoid-based ornaments are particularly interesting as possible honest signals of individual quality, in particular
of foraging efficiency and nutritional status. Some studies have demonstrated the condition dependence of carotenoid-based
plumage in birds. However, many other carotenoid-pigmented bare parts (i.e. skin, caruncles, bills, cere, and tarsi) are present
in birds but, in comparison with plumage, little is known about these traits as indicators of individual quality. Here, we
show that the eye ring pigmentation and bill redness of the red-legged partridge (Alectoris rufa) are positively associated to body condition and recent changes in body mass. Also, we found a negative relationship between
these two traits and heterophil-to-lymphocyte ratio, an indicator of physiological stress (the relationship with bill redness
being significant only for males). In an experiment, we found that after a period of reduction in food intake (with the consequent
loss of body mass), food-restricted birds showed lower eye ring pigmentation than ad-libitum-fed birds. Therefore, different
ornaments seem to reflect changes in body condition but at different speeds or intensities (eye ring, a fleshy ornament, appears
to respond more rapidly to changes in the nutritional status than a keratinized structure as the bill). These results indicate
that carotenoid-based ornaments are condition-dependent traits in the red-legged partridge, being therefore susceptible to
be employed as honest signals of quality in sexual selection. 相似文献
88.
89.