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341.
Susanne Foitzik Ilka Maria Kureck Markus Hannes Rüger Dirk Metzler 《Behavioral ecology and sociobiology》2010,64(10):1641-1654
The ant Hypoponera opacior exhibits alternative reproductive morphs of males and females associated with distinct sexual behaviours. Our long-term study
reports strong seasonality in sexual production with a mating season in early and one in late summer. Winged (alate) reproductives
emerge in June, swarm during the monsoon season and establish new colonies independently. In contrast, wingless worker-like
(ergatoid) reproductives that appear in late August mate within their natal or adjacent nests and either do not disperse or
establish new nests close by. These divergent dispersal patterns allowed us to analyse the impact of local factors on investment
strategies by comparing sex allocation between and within the two reproductive events. The optimal sex ratio for ergatoid
reproductives should be influenced both by competition for matings between brothers (local mate competition) and rivalry among
young locally dispersing queens for workers, nest sites or food (local resource competition). The greater importance of local
resource competition was demonstrated both by a male-biased sex ratio for wingless sexuals and a stronger increase in the
number of males with total sexual production than for the number of queens. Microsatellite analysis revealed that inter-nest
variation in relatedness asymmetry cannot explain split sex ratios in the August generation. Instead, nests with related ergatoid
males raised a male-biased sex ratio contrary to the expectations under local mate competition. In conclusion, male bias in
wingless H. opacior indicates that local mate competition is less strong than local resource competition among ergatoid queens over the help
of workers during nest foundation. 相似文献
342.
Quantitative PCR to estimate copepod feeding 总被引:1,自引:0,他引:1
Jens C. Nejstgaard Marc E. Frischer Paolo Simonelli Christofer Troedsson Markus Brakel Filiz Adiyaman Andrey F. Sazhin L. Felipe Artigas 《Marine Biology》2008,153(4):565-577
Copepods play a central role in marine food webs as grazers of plankton and as key prey for many predators. Therefore, quantifying
their specific trophic interactions is critical for understanding the role of copepods in ocean processes. However, because
of methodological constraints, it remains difficult to investigate in situ copepod feeding without reliance on laborious intrusive
and potentially biased incubation approaches. Recent advances in PCR-based methodologies have demonstrated the feasibility
of directly identifying copepod diets based on prey DNA sequences. Yet, obtaining quantitative information from these approaches
remains challenging. This study presents results of systematic efforts to develop a quantitative PCR (qPCR) assay targeted
to 18S rRNA gene fragments to estimate copepod gut content of specific species of prey algae. These results were first compared
to gut content estimates based on fluorescence in the copepod Calanus finmarchicus fed monocultures of two different microalgae species in controlled laboratory studies. In subsequent field studies, we compared
feeding rates obtained by microscopy and qPCR for Temora longicornis and Acartia clausi feeding on the haptophyte Phaeocystis globosa in natural blooms. These investigations demonstrate a semi-quantitative relationship between gut content estimates derived from qPCR, gut pigment,
and direct microscopy. However, absolute estimates of gut content based on qPCR methodology were consistently lower than expected.
This did not appear to be explained by the extraction methods used, or interference by non-target (predator) DNA in the PCR
reactions, instead suggesting digestion of prey-specific nucleic acids. Furthermore, the 18S rDNA target gene copy number
of the phytoplankton varied with growth phase. Nonetheless, when prey target gene copy number in the ambient water is quantified,
the qPCR-approach can be compared to other methods, and then used to semi-quantitatively estimate relative copepod grazing
on specific prey in situ without involving further incubations. A distinct advantage of a DNA-based molecular approach compared
to gut fluorescence and direct microscopic observation, is the ability to detect non-pigmented and macerated prey. Future
studies should aim to correct for breakdown in prey DNA and perform extensive calibrations to other methods in order to achieve
a quantitative measure of feeding rates in situ. 相似文献
343.
The social organization of gregarious lemurs significantly deviates from predictions of the socioecological model, as they
form small groups in which the number of males approximately equals the number of females. This study uses models of reproductive
skew theory as a new approach to explain this unusual group composition, in particular the high number of males, in a representative
of these lemurs, the redfronted lemur (Eulemur fulvus rufus). We tested two central predictions of “concession” models of reproductive skew theory, which assume that subordinates may
be allowed limited reproduction by dominant group members as an incentive to remain in the group, thereby increasing the group’s
overall productivity. Accordingly, relatives are predicted to receive less reproduction than non-relatives, and the overall
amount of reproductive concessions given to subordinates is predicted to increase as the number of subordinates increases.
In addition, we tested whether the number of females in a group, a variable not previously incorporated in reproductive skew
theory, affected reproductive skew among males. Using microsatellite analyses of tissue DNA, we determined paternities of
49 offspring born into our study population in Kirindy forest (western Madagascar) since 1996 to determine patterns of male
reproductive skew to test these predictions. Our analyses revealed remarkable reproductive skew, with 71% of all infants being
sired by dominant males, but both predictions of reproductive skew models could not be supported. Instead, the number of females
best predicted the apportionment of reproduction among the males in this species, suggesting that current reproductive skew
models need to incorporate this factor to predict reproductive partitioning among male primates and perhaps other group-living
mammals.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Both Peter M. Kappeler and Markus Port contributed equally to this paper. 相似文献
344.
Maximum species richness at intermediate frequencies of disturbance: consistency among levels of productivity 总被引:2,自引:0,他引:2
Development of a mechanistic understanding and predictions of patterns of biodiversity is a central theme in ecology. One of the most influential theories, the intermediate disturbance hypothesis (IDH), predicts maximum diversity at intermediate levels of disturbance frequency. The dynamic equilibrium model (DEM), an extension of the IDH, predicts that the level of productivity determines at what frequency of disturbance maximum diversity occurs. To test, and contrast, the predictions of these two models, a field experiment on marine hard-substratum assemblages was conducted with seven levels of disturbance frequency and three levels of nutrient availability. Consistent with the IDH, maximum diversity, measured as species richness, was observed at an intermediate frequency of disturbance. Despite documented effects on productivity, the relationship between disturbance and diversity was not altered by the nutrient treatments. Thus, in this system the DEM did not improve the understanding of patterns of diversity compared to the IDH. Furthermore, it is suggested that careful consideration of measurements and practical definitions of productivity in natural assemblages is necessary for a rigorous test of the DEM. 相似文献
345.
Wybraniec S Schwartz L Wiesman Z Markus A Wolf D 《Journal of environmental science and health. Part. B》2002,37(3):235-245
The release characteristics of encapsulated formulations containing a combination of plant growth factors (PGF)--plant hormones (IBA, paclobutrazol), nutrients (fertilizers, microelements), and fungicide (prochloraz)--were studied. The formulations were prepared by encapsulating the active ingredients in a polyethylene matrix and, in some cases, subsequently coating the product with polyurethane. Dissolution experiments were carried out with both coated and non-coated formulations to determine the sustained release patterns of the active ingredients. The PGF controlled-release systems obtained have been shown to promote development of root systems, vegetative growth, and reproductive development in cuttings, potted plants, or garden plants of various plant species. These beneficial effects are attributable to the lasting and balanced PGF availability provided by these systems. 相似文献
346.
Incorporating soil structure and root distribution into plant uptake models for radionuclides: toward a more physically based transfer model 总被引:1,自引:0,他引:1
Albrecht A Schultze U Liedgens M Flühler H Frossard E 《Journal of environmental radioactivity》2002,59(3):329-350
Most biosphere and contamination assessment models are based on uniform soil conditions, since single coefficients are used to describe the transfer of contaminants to the plant. Indeed, physical and chemical characteristics and root distribution are highly variable in the soil profile. These parameters have to be considered in the formulation of a more realistic soil-plant transfer model for naturally structured soils. The impact of monolith soil structure (repacked and structured) on Zn and Mn uptake by wheat was studied in a controlled tracer application (dye and radioactive) experiment. We used Brilliant Blue and Sulforhodamine B to dye flow lines and 65Zn and 54Mn to trace soil distribution and plant uptake of surface-applied particle-reactive contaminants. Spatial variation of the soil water content during irrigation and plant growth informs indirectly about tracer and root location in the soil profile. In the structured monolith, a till pan at a depth of 30 cm limited vertical water flow and root penetration into deeper soil layers and restricted tracers to the upper third of the monolith. In the repacked monolith, roots were observed at all depths and fingering flow allowed for the fast appearance of all tracers in the outflow. These differences between the two monoliths are reflected by significantly higher 54Mn and 65Zn uptake in wheat grown on the structured monolith. The higher uptake of Mn can be modelled on the basis of radionuclide and root distribution as a function of depth and using a combination of preferential flow and rooting. The considerably higher uptake of Zn requires transfer factors which account for variable biochemical uptake as a function of location. 相似文献
347.
Michel G. J. den Elzen Niklas Höhne Markus M. Hagemann Jasper van Vliet Detlef P. van Vuuren 《Mitigation and Adaptation Strategies for Global Change》2010,15(5):433-465
The Bali Action Plan as adopted under the United Nations Framework Convention on Climate Change (UNFCCC) in 2007, states that Annex I (developed) countries should reduce their greenhouse gas emissions, based on comparable efforts. Within this context, we have explored various comparable effort approaches (for example, equal marginal abatement costs for all countries) for reducing emissions by the year 2020 for individual countries and regions. In all calculations, the total reduction for Annex I countries as a group is assumed to be 30% below 1990 levels. In the analysis, we compare the reduction targets as calculated from the different approaches with the emission reductions as pledged by these countries as part of the Copenhagen Accord, as drafted under the UNFCCC in 2009. Our analysis indicates that the different elements in these calculations may cause a diversity in outcomes and that, therefore, individual countries may favour certain elements over others. These elements include (a) the choice of the approach itself (the same approach may produce very different outcomes for countries with diverging national circumstances, such as Canada and Russia); (b) the reference year (such as 1990 or 2006 emissions, is very important for countries with an increase in emissions since 1990 (e.g. the United States, Canada) or for those that have lower emission levels (e.g. Russia, the Ukraine)); and (c) rules on land use (these are important for countries with large forest areas). It should be noted that the stringency of the individual countries’ reductions as pledged, differs substantially from the stringency of the reduction targets calculated from the effort-sharing approaches. The current pledges by both the European Union and the United States, are lower than the reductions that would be obtained in the effort-sharing approaches for a 30% overall reduction in Annex I countries. 相似文献
348.
Indika Herath Markus Deurer David HorneRanvir Singh Brent Clothier 《Journal of Cleaner Production》2011,19(14):1582-1589
Hydroelectricity has been rated to have a large water footprint (WF) on global average. We assessed the WF of hydroelectricity by three different methods using New Zealand as a case study. The first (WF-1) and second (WF-2) methods only consider the consumptive water use of the hydroelectricity generation system, while our third method (WF-3) accounts for the net water balance. Irrespective of the method, the WF of New Zealand’s hydroelectricity was found much smaller than the commonly cited international value of 22 m3 GJ−1. Depending on the method, the national WF ranged from 1.55 m3 GJ−1 (WF-3) to 6.05 m3 GJ−1 (WF-1). The WF- 3 considers the net water balance including rainfall, which is the key driver for replenishing water resources. It provides meaningful information that helps our understanding of the differences of the WF in locations, which are diverse in terms of water resource availability. We highlight the effects of local climatic differences and the structural specifics of a hydroelectricity scheme on the WF. The large variation in the WF of hydropower across New Zealand illustrates the inappropriateness of using global average values. Local values, calculated using our hydrologically rational method, must be used. 相似文献
349.
Gräfe M Landers M Tappero R Austin P Gan B Grabsch A Klauber C 《Journal of environmental quality》2011,40(3):767-783
We describe the application of quantitative evaluation of mineralogy by scanning electron microscopy in combination with techniques commonly available at hard X-ray microprobes to define the mineralogical environment of a bauxite residue core segment with the more specific aim of determining the speciation of trace metals (e.g., Ti, V, Cr, and Mn) within the mineral matrix. Successful trace metal speciation in heterogeneous matrices, such as those encountered in soils or mineral residues, relies on a combination of techniques including spectroscopy, microscopy, diffraction, and wet chemical and physical experiments. Of substantial interest is the ability to define the mineralogy of a sample to infer redox behavior, pH buffering, and mineral-water interfaces that are likely to interact with trace metals through adsorption, coprecipitation, dissolution, or electron transfer reactions. Quantitative evaluation of mineralogy by scanning electron microscopy coupled with micro-focused X-ray diffraction, micro-X-ray fluorescence, and micro-X-ray absorption near edge structure (mXANES) spectroscopy provided detailed insights into the composition of mineral assemblages and their effect on trace metal speciation during this investigation. In the sample investigated, titanium occurs as poorly ordered ilmenite, as rutile, and is substituted in iron oxides. Manganese's spatial correlation to Ti is closely linked to ilmenite, where it appears to substitute for Fe and Ti in the ilmenite structure based on its mXANES signature. Vanadium is associated with ilmenite and goethite but always assumes the +4 oxidation state, whereas chromium is predominantly in the +3 oxidation state and solely associated with iron oxides (goethite and hematite) and appears to substitute for Fe in the goethite structure. 相似文献
350.
Saara Kupsala Pekka Jokinen Markus Vinnari 《Journal of Agricultural and Environmental Ethics》2013,26(1):119-135
This paper explores citizens’ views about the welfare of farmed fish and the mental abilities of fish with a large survey data sample from Finland (n = 1,890). Although studies on attitudes towards animal welfare have been increasing, fish welfare has received only limited empirical attention, despite the rapid expansion of aquaculture sector. The results show that the welfare of farmed fish is not any great concern in the Finnish society. The analysis confirms the distinct character given to farmed fish compared to traditional farmed animals. Salmon are rated low in their mental abilities, including the capacity to feel pain, which may weaken ethical concerns for fish welfare. When analyzing the social determinants surrounding the rating of the welfare of farmed fish, it was shown that fish welfare attitudes follow general animal welfare attitudes regarding age and place of residence as fish welfare tends to be rated more negatively among younger age groups and among urban residents. However, no clear connection could be identified between gender and the rating of fish welfare, which may suggest that the distinct cultural categorization of fish diminishes the typical gender difference identified in animal attitudes. It is concluded that in order to improve awareness about fish welfare, there is a need to increase dissemination of scientific knowledge about fish and their welfare. Moreover, further research should be directed toward studying the moral positioning of fish and the distinct moral categorization they receive. 相似文献