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51.
52.
Defoliating insect immune defense interacts with induced plant defense during a population outbreak 总被引:1,自引:0,他引:1
During population outbreaks, top-down and bottom-up factors are unable to control defoliator numbers. To our knowledge, details of biotic interactions leading to increased population density have not been studied during real population outbreaks. We experimentally assessed the strength of plant defenses and of insect immunocompetence, assumed to contribute to active insect resistance against parasitoids and pathogens, in the geometrid Epirrita autumnata during a steep increase in population density. We demonstrated rapid (same-season) induced resistance in the foliage of its host, mountain birch. The response was systemic, spreading throughout the tree, and retarded larval growth rate by approximately 10%. On the other hand, no direct delayed carry-over effects were found in the next season in larval growth rate, mortality, or pupal mass. Larval damage to a tree during the previous year, however, significantly (by approximately 13%) accelerated the advance of the immune response (measured as melanization of an implant inserted into the pupal hemocoel). The encapsulation rate correlated positively with larval mortality in trees in which larvae had been introduced the previous year, but not in control trees. Both of these observations suggest that induced plant defense was associated with an increased insect immunocompetence during the population increase. 相似文献
53.
Contaminant mass discharge estimation in groundwater based on multi-level point measurements: a numerical evaluation of expected errors 总被引:1,自引:0,他引:1
Different methods for the field-scale estimation of contaminant mass discharge in groundwater at control planes based on multi-level well data are numerically analysed for the expected estimation error. We consider "direct" methods based on time-integrated measuring of mass flux, as well as "indirect" methods, where estimates are derived from concentration measurements. The appropriateness of the methods is evaluated by means of modelled data provided by simulation of mass transport in a three-dimensional model domain. Uncertain heterogeneous aquifer conditions are addressed by means of Monte-Carlo simulations with aquifer conductivity as a random space function. We investigate extensively the role of the interplay between the spatial resolution of the sampling grid and aquifer heterogeneity with respect to the accuracy of the mass discharge estimation. It is shown that estimation errors can be reduced only if spatial sampling intervals are in due proportion to spatial correlation length scales. The ranking of the methods with regard to estimation error is shown to be heavily dependent on both the given sampling resolution and prevailing aquifer heterogeneity. Regarding the "indirect" estimation methods, we demonstrate the great importance of a consistent averaging of the parameters used for the discharge estimation. 相似文献
54.
Background, Aim and Scope
Due to their large potential for manifold applications, the use of nanoparticles is of increasing importance. As large amounts
of nanoparticles may reach the environment voluntarily or by accident, attention should be paid on the potential impacts on
the environment. First studies on potential environmental effects of photocatalytic TiO2 nanoparticles have been performed
on the basis of widely accepted, standardized test systems which originally had been developed for the characterization of
chemicals. The methods were adapted to the special requirements of testing photocatalytic nanoparticles.
Materials and Methods:
Suspensions of two different nanoparticles were illuminated to induce their photocatalytic activity. For testing, the growth
inhibition test with the green alga Desmodesmus subspicatus and the immobilization test with the daphnid Daphnia magna were
selected and performed following the relevant guidelines (algae: ISO 8692, OECD 201, DIN 38412-33; daphnids: ISO 6341, OECD
202, DIN 38412-30). The guidelines were adapted to meet the special requirements for testing photocatalytic nanoparticles.
Results:
The results indicate that it is principally possible to determine the ecotoxicity of nanoparticles. It was shown that nanoparticles
may have ecotoxicological effects which depend on the nature of the particles. Both products tested differ in their toxicity.
Product 1 shows a clear concentration-effect curve in the test with algae (EC50: 44 mg/L). It could be proven that the observed
toxicity was not caused by accompanying contaminants, since the toxic effect was comparable for the cleaned and the commercially
available product. For product 2, no toxic effects were determined (maximum concentration: 50 mg/L). In the tests with daphnids,
toxicity was observed for both products, although the concentration effect-curves were less pronounced. The two products differed
in their toxicity; moreover, there was a difference in the toxicity of illuminated and non-illuminated products.
Discussion:
Both products differ in size and crystalline form, so that these parameters are assumed to contribute to the different toxicities.
The concentration-effect curves for daphnids, which are less-pronounced than the curves obtained for algae, may be due to
the different test organisms and/or the differing test designs. The increased toxicity of pre-illuminated particles in the
tests with daphnids demonstrates that the photocatalytic activity of nanoparticles lasts for a period of time.
Conclusions:
The following conclusions can be drawn from the test results: (I) It is principally possible to determine the ecotoxicity
of (photocatalytic) nanoparticles. Therefore, they can be assessed using methods comparable to the procedures applied for
assessing soluble chemicals. - (II) Nanoparticles may exert ecotoxicological effects, which depend on the specific nanoparticle.
- (III) Comparable to traditional chemicals, the ecotoxicity depends on the test organisms and their physiology. - (IV) The
photocatalytic activity of nanoparticles lasts for a relevant period of time. Therefore, pre-illumination may be sufficient
to detect a photocatalytic activity even by using test organisms which are not suitable for application in the pre-illumination-phase.
Recommendations and Perspectives:
First results are presented which indicate that the topic 'ecotoxicity and environmental effects of nanoparticles' should
not be neglected. In testing photocatalytic nanoparticles, there are still many topics that need clarification or improvement,
such as the cause for an observed toxicity, the improvement of the test design, the elaboration of a test battery and an assessment
strategy.
On the basis of optimized test systems, it will be possible to test nanoparticles systematically. If a potential risk by specific
photocatalytic particles is known, a risk-benefit analysis can be performed and, if required, risk reducing measures can be
taken. 相似文献
55.
56.
Goal and Methods
During two years, soil solution samples were collected at 18 forest sites with low anthropogenic heavy metal loads in Bavaria using ceramic suction cups. The collected samples were analysed for pH, conductivity, dissolved organic compounds, and the trace elements Al, Cr, Fe, Mn, Ni, Cu, Zn, Cd, Ba, and Pb.Results
In addition to initial interference effects caused by the installation of suctions cups, time series were characterised by seasonal variations. The results obtained for the replicated suction cups were comparable for every individual area with standard deviations of 20 to 25 percent. With increasing soil depth, the pH of the soil solution increases specifically at those sites (up to 2.5 pH units) where the topsoils have been acidified. On the other hand, concentrations of all trace elements investigated — excepted of Al and Mn — are not influenced by the soil depth. The forest stand has no significant additional effect on trace element concentrations. Contents of Al, Mn, and Zn are correlated with low pH-values in the soil solution, whereas the mobilisation of Ba is mainly caused by ion exchange. Complexes of trace elements and dissolved organic matter were only detected for Cu at one site. Element concentrations in the soil solution are not significantly influenced by the contents of aqua regia soluble portions in the soil matter. Only very high qua soluble portions increase the concentrations in the soil solution. The overall heavy metal concentrations determined in soil solutions are low compared with different limiting and threshold values, respectively.Conclusions
Trace element concentrations in soil solutions are mainly influenced by the soil properties themselves. The contribution of the forest stand is negligible. Therefore, from the ecotoxicologic point of view, the risk of leaching heavy metals contaminating the groundwater is not significant for the investigated forest sites and without any respect to silviculture practices. 相似文献57.
Eliecer Díaz Christine Güldenzoph Markus Molis Christopher McQuaid Martin Wahl 《Marine Biology》2006,149(6):1301-1311
Variabilities in the responses of several South African red and green macroalgae to direct grazing and the responses of one green alga to cues from grazers were tested. We used two feeding experiments: (1) testing the induced responses of three red and one green algae to direct grazing by mesograzers and (2) a multi-treatment experiment, in which the direct and indirect effects of one macrograzer species on the green alga Codium platylobium were assessed. Consumption rates were assessed in feeding assays with intact algal pieces and with agar pellets containing non-polar extracts of the test algae. Defensive responses were induced for intact pieces of Galaxaura diessingiana, but were not induced in pellets, suggesting either morphological defence or chemical defence using polar compounds other than polyphenols. In contrast, exposure to grazing stimulated consumption of Gracilaria capensis and Hypnea spicifera by another grazing species. In the multi-treatment experiment, waterborne cues from both grazing and non-grazing snails induced defensive algal traits in C. platylobium. We suggest that inducible defences among macroalgae are not restricted to brown algae, but that both the responses of algae to grazers and of grazers to the defences of macroalgae are intrinsically variable and complex. 相似文献
58.
Markus Heid 《Environmental Sciences Europe》2003,15(1):39-44
Goal and Scope
Planning projects concerning the environment often provoke problems due to a lack of transparency of the applied scales and the appropriate evaluation methods. This paper therefore examines the general structure of all valuation processes before describing the character of the economic evaluation method in detail. From this point of view, requirements on planning processes are coming out which are to be achieved if their duty — the provision of public goods — is to be carried out efficiently.Features
It will be shown that from an economist’s perspective a planning procedure acts as a surrogate of the market in coordinating individual’s preferences. The reasons for the inefficient level of the provision of environmental goods by private producers are their main characteristics: non-rivality and non-excludability; therefore public goods do not possess prices. Thus environmental goods have to be produced by cooperation and planning processes have to guarantee this. The main character of planning procedures is be seen in communication processes which is documented by a narrative study.Results and Conclusions
Planning projects concerning the environment are strongly contingent on communication processes. Thus, they are also controllable by communication. The interdisciplinary research in communications shows that cooperative behaviour which is required for planning projects that should provide public goods can be benefited by applicative communication technologies. In this juncture (social) norms more and more emerge to act an important part in conveying cooperative behaviour. Especially so called ‘Sozialtechniken’ seem to be able to activate such norms.Outlook
From the economist’s point of view planning projects concerning the environment mostly desiderate two things: Firstly, the procedures and methods which are applied to evaluate the regarding environmental goods in many cases suffer from transparency. Secondly, individual’s preferences predominant by the local population and accordingly by the directly involved parties are mostly not acquired adequately to achieve an efficient allocation of environmental goods. Applying more communication technologies to solve these two problems in the future both an increase of efficiency and an increase of the acceptability of such planning projects can be expected. 相似文献59.
60.
S?nke Zaehle Stephen Sitch I Colin Prentice Jari Liski Wolfgang Cramer Markus Erhard Thomas Hickler Benjamin Smith 《Ecological applications》2006,16(4):1555-1574
We show the implications of the commonly observed age-related decline in aboveground productivity of forests, and hence forest age structure, on the carbon dynamics of European forests in response to historical changes in environmental conditions. Size-dependent carbon allocation in trees to counteract increasing hydraulic resistance with tree height has been hypothesized to be responsible for this decline. Incorporated into a global terrestrial biosphere model (the Lund-Potsdam-Jena model, LPJ), this hypothesis improves the simulated increase in biomass with stand age. Application of the advanced model, including a generic representation of forest management in even-aged stands, for 77 European provinces shows that model-based estimates of biomass development with age compare favorably with inventory-based estimates for different tree species. Model estimates of biomass densities on province and country levels, and trends in growth increment along an annual mean temperature gradient are in broad agreement with inventory data. However, the level of agreement between modeled and inventory-based estimates varies markedly between countries and provinces. The model is able to reproduce the present-day age structure of forests and the ratio of biomass removals to increment on a European scale based on observed changes in climate, atmospheric CO2 concentration, forest area, and wood demand between 1948 and 2000. Vegetation in European forests is modeled to sequester carbon at a rate of 100 Tg C/yr, which corresponds well to forest inventory-based estimates. 相似文献