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61.
T. Giray Z.-Y. Huang Ernesto Guzmán-Novoa G. E. Robinsons 《Behavioral ecology and sociobiology》1999,47(1-2):17-28
Two factors that influence age at onset of foraging in honeybees are juvenile hormone (JH) and colony age demography (older
bees inhibit behavioral development of younger bees). We tested the hypothesis that genetic variation among bees for these
factors influences genetic variation in behavioral development. Pairs of colonies showing genetic differences in rates of
behavioral development were identified in a screening experiment and bees from these colonies were used for physiological
and behavioral assays. Six pairs were assayed, three with European bees only and three with both European and Africanized
bees. There was genetic variation for the following four components: (1) production of JH in four pairs (experiment 1); (2)
sensitivity to JH in three pairs (experiment 2); (3) sensitivity to social inhibition in three pairs (experiment 3), and (4)
potency of social inhibition in four pairs (experiment 4). Cross-fostering assays (experiment 5), which allowed all four components
to be evaluated simultaneously, revealed genetic variation for production of JH, sensitivity to JH, or sensitivity to social
inhibition in five of six pairs, and potency of social inhibition in five of six pairs. There was often evidence for genotypic
differences in more than one component, and no consistent pattern of association among any of the components. Africanized
bees had faster rates of behavioral development than European bees, but there were no racial differences in patterns of variation
among the four components. These results indicate that there are at least several, apparently distinct, physiological processes
associated with JH and colony age demography upon which natural selection can act to alter the rate of behavioral development
in honeybees.
Received: 8 December 1998 / Received in revised form: 29 July 1999 / Accepted: 8 August 1999 相似文献
62.
Ernesto Bonilla Rocío Contreras Shirley Medina-Leendertz Marylu Mora Virginia Villalobos Milagros Paz 《毒物与环境化学》2013,95(4):742-747
The effect of resveratrol was studied on the life span and motor activity of Drosophila melanogaster treated with manganese (Mn). Two days after emerging from the pupa, male wild type D. melanogaster were fed for 13 days with corn media containing 15?mM Mn. Thereafter, Drosophila were divided into six groups of 300 flies each: (1) the flies remained treated with Mn; (2) began treatment with 0.43?mM resveratrol (Mn-resveratrol group); (3) received no additional treatment (Mn-no treatment group); (4) simultaneously fed with Mn and resveratrol (Mn?+?resveratrol group). In addition, a control (5) with no treatment and another group (6) fed only with resveratrol after emerging from the pupa were included. All Mn-treated flies (group 1) were dead on the 25th day. The life span in the resveratrol group was 91?±?0.33 days (mean?±?S.E.M.) and in Mn-resveratrol flies was 83?±?2 days. These two values were significantly higher than those detected in the control (5) and Mn-no treatment (group 3) flies whose life span were 68?±?0.33 and 67?±?2.31 days, respectively. The Mn?+?resveratrol-fed flies had a markedly higher life span (31?±?1.53 days) than Mn-fed flies (23?±?0.88 days). In the flies that received Mn (Mn and Mn?+?resveratrol groups), the motor activity decreased significantly with respect to control (groups 5) and the Mn–resveratrol and resveratrol groups. In conclusion, resveratrol increased significantly the life span of Mn-treated D. melanogaster. 相似文献
63.
Tracking the evolution of research in waste recycling science (WRS) can be valuable for environmental agencies, as well as for recycling businesses. Maps of science are visual, easily readable representations of the cognitive structure of a branch of science, a particular area of research or the global spectrum of scientific production. They are generally built upon evidence collected from reliable sources of information, such as patent and scientific publication databases. This study uses the methodology developed by Rafols et al. (2010) to make a "double overlay map" of WRS upon a basemap reflecting the cognitive structure of all journal-published science, for the years 2005 and 2010. The analysis has taken into account the cognitive areas where WRS articles are published and the areas from where it takes its intellectual nourishing, paying special attention to the growing trends of the key areas. Interpretation of results lead to the conclusion that extraction of energy from waste will probably be an important research topic in the future, along with developments in general chemistry and chemical engineering oriented to the recovery of valuable materials from waste. Agricultural and material sciences, together with the combined economics, politics and geography field, are areas with which WRS shows a relevant and ever increasing cognitive relationship. 相似文献
64.
Ernesto Bosatta 《Ecological modelling》1981,13(4):237-245
This is the second part of a study aimed at achieving some qualitative understanding of the stability properties of the root-microorganism soil system. The first part concentrated on the effect on this stability of different patterns of either nitrogen- or energy-limiting conditions. To this end, a mathematical model has been developed. The model, the theory and some results of the first part are extended here to more complex situations.A factor is first defined to measure the likelihood of the danger of extinction of the roots. It is found that this danger is increased with increasing specific mortality rates, decreasing nitrogen input and/or increasing periods of time during which decomposers are nitrogen-limited. It is also found that the danger of extinction is not directly proportional to absolute nitrogen losses from the system. Some possible explanations in terms of compensatory mechanisms of the roots are discussed. 相似文献
65.
Pollination is an ecological process that provides important services to humans. Pollination service in agroecosystems depends on several factors, including the land management systems used by farmers. Here we focused on the effects of insect pollinator diversity on coffee fruit production along a gradient of management systems in central Veracruz, Mexico. The gradient ranged from low environmental impact management systems (the native forest is not completely removed) to high environmental impact management systems (the native forest is completely removed). We hypothesized that pollinator diversity should be higher in low-impact systems. Then, if fruit production is positively related to pollinator diversity, plantations with low-impact management systems should display higher fruit production than plantations with high-impact management systems. We used observational and experimental data to test this hypothesis. Our results indicated that low-impact management systems have higher species richness and relative diversity (measured with the Shannon-Wiener diversity index) of pollinators than high-impact management systems. In all cases, fruit production was positively related with species richness and diversity of pollinators. Moreover, fruit production was higher in low-impact than in high-impact management systems. These results suggest that the diversity of insect pollinators can be influenced by the management system applied by farmers, and that such effects may have strong consequences on coffee fruit production. 相似文献
66.
Rao D Ceballos Fernandez O Castañeda-Barbosa E Díaz-Fleischer F 《Die Naturwissenschaften》2011,98(8):699-703
Most orb-web spiders face downwards in the web. A downward orientation has been proposed to be the optimal strategy because
spiders run faster downwards and thus can catch prey quicker. Consequently, orb-web spiders also extend their web in the lower
part, leading to top-down web asymmetry. Since the majority of orb-web spiders face downwards, it has been difficult to test
the effect of orientation on prey capture and web asymmetry. In this study, we explored the influence of reverse orientation
on foraging efficiency and web asymmetry in Verrucosa arenata, a neotropical orb-web spider that faces upwards in the web. We show that reverse orientation does not imply reverse web
asymmetry in this species. V. arenata spiders captured more prey in the lower part of the web but more prey per area on the upper part. The average running speeds
of spiders did not differ between upward and downward running, but heavier spiders took longer to capture prey while running
upwards. We discuss these findings in the context of foraging efficiency and web asymmetry. 相似文献
67.
Hector G. Riveros Alfredo Alba Pilar Ovalle Beatriz Silva Ernesto Sandoval 《Journal of the Air & Waste Management Association (1995)》2013,63(5):459-462
ABSTRACT From the analysis of data of the Inspection/Maintenance (I/M) program, and of the long-term trend of ambient CO concentrations in Mexico City, it is inferred that three-way catalysts (TWCs) have a 45% efficiency, well below the expected 90% value. The most probable causes are sulfur poisoning, lead contamination, and ceramic breakage due to bumps and potholes on the streets. Also, we have found a ratio between the average daily peak value of atmospheric CO and gasoline consumption: (11 ± 1) ppbCO/MLm (million liters of gasoline per month) in 1988 decaying to (10 ±1) in 1991 for Mexico City before the introduction of TWCs. In addition, we found a correlation between the monthly averages of CO daily peak and meteorological variables, explaining most of the seasonal changes using only the intensity of the inversion layer and surface wind speed. 相似文献
68.
Ernesto Di Maio Raed Mali Salvatore Iannace 《Journal of Polymers and the Environment》2010,18(4):626-633
Conventional direct melt mixing technology was investigated on zein and kafirin, two vegetable proteins extracted, respectively,
from maize and sorghum. A lab scale internal mixer has been used to thoroughly study the thermo-plasticization process of
the proteins with several plasticizers. Different compositions were investigated under different processing conditions. In
particular, the lengthy procedures of forming the protein/solvent/plasticizer solution followed by drying or the protein/plasticizer
emulsion followed by the precipitation of the extrudable resin, reported in the literature for these systems, were avoided
and the protein and plasticizer were directly fed into the mixer to obtain a plastic-like material. The effect of plasticizer
type and content and mixing process variables on the mechanical properties was analyzed. Compression molded slabs were transparent,
strong and flexible, with properties similar to the cast films reported in the literature, prepared with the same type of
plasticizers. However, lower plasticizer content was sufficient to produce equally flexible films, proving an enhanced plasticization
efficiency of the mixing process, as compared to casting. 相似文献
69.
Y.F. Elshorbany J. Kleffmann R. Kurtenbach E. Lissi M. Rubio G. Villena E. Gramsch A.R. Rickard M.J. Pilling P. Wiesen 《Atmospheric environment (Oxford, England : 1994)》2010,44(40):5383-5394
The oxidation capacity of the highly polluted urban area of Santiago de Chile has been evaluated during a winter measurement campaign from May 25 to June 07, 2005, with the results compared and contrasted with those previously evaluated during a summer campaign from March 8 to 20, 2005. The OH radical budget was evaluated in both campaigns employing a simple quasi-photostationary state model (PSS) constrained with simultaneous measurements of HONO, HCHO, O3, NO, NO2, j(O1D), j(NO2), 13 alkenes and meteorological parameters. In addition, a zero dimensional photochemical box model based on the Master Chemical Mechanism (MCMv3.1) has been used for the analysis of the radical budgets and concentrations of OH, HO2 and RO2. Besides the above parameters, the MCM model has been constrained by the measured CO and other volatile organic compounds (VOCs) including alkanes and aromatics. Total production and destruction rates of OH and HO2 in winter are about two times lower than that during summer. Simulated OH levels by both PSS and MCM models are similar during the daytime for both winter and summer indicating that the primary OH sources and sinks included in the simple PSS model are predominant. On a 24 h basis, HONO photolysis was shown to be the most important primary OH radical source comprising 81% and 52% of the OH initiation rate during winter and summer, respectively followed by alkene ozonolysis (12.5% and 29%), photolysis of HCHO (6.1% and 15%), and photolysis of O3 (<1% and 4%), respectively. During both winter and summer, there was a balance between the OH secondary production (HO2 + NO) and destruction (OH + VOCs) showing that initiation sources of RO2 and HO2 are no net OH initiation sources. This result was found to be fulfilled also for all other studies investigated. Seasonal impacts on the radical budgets are also discussed. 相似文献