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201.
Christina Goldfine Ph.D. George J. Knight James E. Haddow Glenn E. Palomaki 《黑龙江环境通报》1989,9(3):167-172
In the present study, a recently reported immunochemical technique for measuring acetylcholinesterase (AChE) in amniotic fluid utilizing the 4F19 antibody was compared with the widely utilized polyacrylamide gel technique to determine whether the immunochemical assay provided an advantage in separating unaffected pregnancies from those associated with open spina bifida (OSB) and open ventral wall defects (OVWD). The study included (1) 73 amniotic fluid samples from unaffected pregnancies [alpha-fetoprotein (AFP) < 2 MoM] with no visible gel AChE band, (2) nine bloodstained samples from unaffected pregnancies (AFP 2·2–4·0 MoM) with visible gel AChE bands, (3) 18 samples associated with OSB (AFP 2·2–7·0 MoM) with visible gel AChE bands, and (4) 20 samples associated with OVWD (AFP 3·2–53·5 MoM) with visible gel AChE bands. The immunochemical assay produced ranges of measurements in the four respective categories as follows: (1) 2–60 arbitrary units (AU): (2) 14–69 AU, (3) 61–593 AU, and (4)22–476 AU. Eight of the nine unaffected pregnancies with visible gel AChE bands had immunochemical measurements below the highest measurement for the samples with no visible AChE band (60 AU), as did five out of 20 OVWD pregnancies. Two of the OSB cases had values of 61 and 62 AU. These data indicate that the 4F19 specific monoclonal antibody to AChE is capable of distinguishing unaffected from affected pregnancies with reasonable reliability but that more work needs to be done to establish the extent of overlap between the unaffected and affected populations. 相似文献
202.
Ideal free distribution (IFD) models are perhaps the group of mathematical models of behavior that have been the most widely
and successfully applied by empiricists. These models can be applied to nearly any situation in which consumers compete—by
any mechanism—for resources that are patchily distributed in their environment. Although IFD models have come to be broadly
accepted, experiments that simultaneously test more than a single prediction are rare. Instead, investigators normally either
test (1) for a relationship between the distribution of consumers and the distribution of resources or (2) whether average
fitnesses are equal across resource patches. We conducted experiments with pea aphids (Acyrthosiphon pisum Harris) feeding on two patches of fava beans (Vicia faba L.) to fully independently parameterize an IFD model with interference competition and then test quantitative predictions
about aphid spatial distributions and the payoffs of patch choice. We found a precise fit between aphids’ predicted and observed
reproductive successes. Furthermore, by varying patch “quality” in two ways, we were able to show that aphid distributions
vary with the mode of resource variation in the predicted manner: aphids (1) matched resources when patches varied in size
but not quality and (2) overmatched the good patch when patches varied in quality but not size (predicted as a consequence
of weak interference). The close correspondence between quantitative predictions of the model with observed behaviors suggests
that IFD theory is a framework with more explanatory power than is generally appreciated. 相似文献
203.
Nitrogen inputs promote the spread of an invasive marsh grass. 总被引:3,自引:0,他引:3
Anna Christina Tyler John G Lambrinos Edwin D Grosholz 《Ecological applications》2007,17(7):1886-1898
Excess nutrient loading and large-scale invasion by nonnatives are two of the most pervasive and damaging threats to the biotic and economic integrity of our estuaries. Individually, these are potent forces, but it is important to consider their interactive impacts as well. In this study we investigated the potential limitation of a nonnative intertidal grass, Spartina alterniflora, by nitrogen (N) in estuaries of the western United States. Nitrogen fertilization experiments were conducted in three mud-flat habitats invaded by S. alterniflora in Willapa Bay, Washington, USA, that differed in sediment N. We carried out parallel experiments in San Francisco Bay, California, USA, in three habitats invaded by hybrid Spartina (S. alterniflora x S. foliosa), in previously unvegetated mud flat, and in native S. foliosa or Salicornia virginica marshes. We found similar aboveground biomass and growth rates between habitats and estuaries, but end-of-season belowground biomass was nearly five times greater in San Francisco Bay than in Willapa Bay. In Willapa Bay, aboveground biomass was significantly correlated with sediment N content. Addition of N significantly increased aboveground biomass, stem density, and the rate of spread into uninvaded habitat (as new stems per day) in virtually all habitats in both estuaries. Belowground biomass increased in Willapa Bay only, suggesting that belowground biomass is not N limited in San Francisco Bay due to species differences, N availability, or a latitudinal difference in the response of Spartina to N additions. The relative impact of added N was greater in Willapa Bay, the estuary with lower N inputs from the watershed, than in San Francisco Bay, a highly eutrophic estuary. Nitrogen fertilization also altered the competitive interaction between hybrid Spartina and Salicornia virginica in San Francisco Bay by increasing the density and biomass of the invader and decreasing the density of the native. There was no significant effect of N on the native, Spartina foliosa. Our results indicate that excess N loading to these ecosystems enhances the vulnerability of intertidal habitats to rapid invasion by nonnative Spartina sp. 相似文献
204.
Joachim G. Frommen Marion Mehlis Christina Brendler Theo C. M. Bakker 《Behavioral ecology and sociobiology》2007,61(4):533-539
Shoaling with familiar kin is a well-known phenomenon. It has been described both for adult and for fry of three-spined sticklebacks
(Gasterosteus aculeatus). However, evidence of preference for kin independent of familiarity is scarce. Furthermore, inbreeding effects have not
been studied for shoaling preferences and there is a lack of studies about changes in individuals’ ability to recognise kin
during different phases of life history. We gave inbred and outbred, nonreproductive sticklebacks of different age the choice
to shoal with a group of familiar siblings vs unfamiliar non-siblings and with unfamiliar siblings vs unfamiliar non-siblings.
Subadult sticklebacks preferred to shoal with familiar kin over unfamiliar non-kin, but inbred and outbred individuals had
similar preferences. When given the choice between unfamiliar siblings and unfamiliar non-sibs, adult outbred fish preferred
the shoal of kin, while inbred fish behaved indifferently. Body characteristics of the group such as body mass, standard length
and condition of its members did not significantly explain the shoaling preferences for kin. Thus, sticklebacks were capable
of recognising familiar and unfamiliar kin. The latter capability was lost by inbreeding. 相似文献
205.
William O'Neil Martin David Christina Moore Erhard Joeres 《Journal of Environmental Economics and Management》1983,10(4):346-355
Recent emphasis on reforms of environmental regulation has led to suggestions for strategies which maintain environmental standards but allow the needed flexibility and cost effectiveness. The transferable discharge permit (TDP) is one such strategy for water pollution control recently adopted in Wisconsin. In this article, the potential for substantial cost savings from trading TDPs is demonstrated using data on the Fox River in Wisconsin. A simulation model of water quality (Qual-III) and a linear programming model of abatement costs determine the optimum pattern of discharge. Reaching that optimum from proposed pollution abatement orders is shown to be feasible. Varying conditions of flow and temperature can be accommodated using trade coefficients which can be accurately estimated through interpolation. The calculations demonstrate the value and feasibility of flexible regulations governing water pollution abatement. 相似文献
206.
Christina Goldfine Ph.D James E. Haddow George J. Knight Glenn E. Palomaki 《黑龙江环境通报》1989,9(10):697-700
In this study we define for the first time the distribution of alpha-fetoprotein levels and acetylcholinesterase ratios in amniotic fluid samples associated with fetal gastroschisis. Elevated alpha-fetoprotein levels and positive acetylcholinesterase measurements are found in virtually all cases, indicating that these combined measurements are highly reliable in detecting this lesion. 相似文献
207.
The European Water Framework Directive (WFD) requires the definition of reference conditions, i.e. pristine conditions, for all surface waters. As the present state of Danish coastal waters cannot be referred to as pristine, reference conditions have to be assessed by analysis of historical data or by the use of models. Using Randers Fjord as an example, the aim of this work was i) to demonstrate possibilities and restrictions of assessing reference conditions by historical data and by modelling; and ii) to demonstrate how ecological conditions have changed along with eutrophication. The ample historical data from Randers Fjord allowed us to assess reference conditions with respect to benthic macrophytes and benthic fauna. Models of varying complexity enabled us to assess reference conditions for nutrients, chlorophyll a, Secchi depth, and eelgrass. We conclude that models can be a useful supplement to assess reference conditions, though they are presently restricted by the lack of quantitative links between eutrophication and species composition. 相似文献
208.
Papadopoulos A Vassiliadou I Costopoulou D Papanicolaou C Leondiadis L 《Chemosphere》2004,57(5):413-419
Food intake is the main source of exposure to dioxin-like compounds for humans. The results of a surveillance programme on polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and co-planar polychlorinated biphenyls (co-PCBs) in 77 food samples from the Greek market and producers are presented. The study included the analyses of milk and dairy products, meat and meat products, fish, vegetable oil, eggs, fruit, vegetable and rice collected between August and December 2002. After extraction, extracts were cleaned up on a series of carbon column chromatography, silica gel, alumina chromatography, and then analysed by high resolution gas chromatography/high resolution mass spectrometry. All samples had a dioxin content far below the EC Regulation (2375/2001/EC) limits. 相似文献
209.
Organic synthesis is usually performed in solution to dissolve both reactants and catalysts and to deliver heat. Here, we
show that glycerol, which is a non-toxic, biodegradable, and recyclable liquid manufactured from renewable sources, has a
high potential to serve as alternative green solvent for organic reactions. Several catalytic and non-catalytic reactions
were successfully performed in glycerol. High products yields and selectivities were achieved. Besides solubility of the reactants
and the catalysts and easy separation of the product, glycerol offers several other benefits such as catalyst recycling, microwave
assisting reaction, and biphasic and emulsion modes. 相似文献
210.