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31.
Copepod nauplii are important in plankton food web dynamics, but limited information is available about their ecology due to methodological challenges. Reported here is a new molecular method that was developed, optimized, and tested in laboratory and field samples that uses quantitative PCR (qPCR) to identify and estimate the abundance of nauplii of the planktonic copepod, Parvocalanus crassirostris. The overall approach included collection of bulk zooplankton samples in the field, size fractionation to create artificial cohorts of relatively few developmental stages, obtaining DNA copy number for each size fraction by qPCR amplification of a target gene region, and estimation of the number of animals in each fraction through application of known DNA copy number across developmental stage. Method validation studies found that our qPCR-based approach has comparable accuracy to microscope-based counts of early developmental stages. Naupliar abundance estimates obtained using the two methods on cultured populations were similar; the regression of qPCR estimates on microscope-based counts resulted in a nearly 1:1 ratio (slope = 1.09). The qPCR-based method is superior to traditional identification and quantification methods for nauplii due to its higher taxonomic resolution, sensitive detection over a range of DNA quantities, and relatively high throughput sample processing. 相似文献
32.
Ali?NasrolahiEmail author Christian?Pansch Mark?Lenz Martin?Wahl 《Marine Biology》2012,159(2):331-340
The fate of key species, such as the barnacle Amphibalanus improvisus, in the course of global change is of particular interest since any change in their abundance and/or performance may entail
community-wide effects. In the fluctuating Western Baltic, species typically experience a broad range of environmental conditions,
which may preselect them to better cope with climate change. In this study, we examined the sensitivity of two crucial ontogenetic
phases (naupliar, cypris) of the barnacle toward a range of temperature (12, 20, and 28°C) and salinity (5, 15, and 30 psu)
combinations. Under all salinity treatments, nauplii developed faster at intermediate and high temperatures. Cyprid metamorphosis
success, in contrast, was interactively impacted by temperature and salinity. Survival of nauplii decreased with increasing
salinity under all temperature treatments. Highest settlement rates occurred at the intermediate temperature and salinity
combination, i.e., 20°C and 15 psu. Settlement success of “naive” cyprids, i.e., when nauplii were raised in the absence of
stress (20°C/15 psu), was less impacted by stressful temperature/salinity combinations than that of cyprids with a stress
history. Here, settlement success was highest at 30 psu particularly at low and high temperatures. Surprisingly, larval survival
was not highest under the conditions typical for the Kiel Fjord at the season of peak settlement (20°C/15 psu). The proportion
of nauplii that ultimately transformed to attached juveniles was, however, highest under these “home” conditions. Overall,
only particularly stressful combinations of temperature and salinity substantially reduced larval performance and development.
Given more time for adaptation, the relatively smooth climate shifts predicted will probably not dramatically affect this
species. 相似文献
33.
Biodegradable Polyester-Based Blend Reinforced with Curauá Fiber: Thermal,Mechanical and Biodegradation Behaviour 总被引:1,自引:1,他引:0
Fernanda Harnnecker Derval dos Santos Rosa Denise Maria Lenz 《Journal of Polymers and the Environment》2012,20(1):237-244
Biodegradable composites can be produced by the combination of biodegradable polymers (BP) as matrix and vegetal fibers as
reinforcement. Composites of a commercial biodegradable polymer blend and curauá fibers (loaded at 5, 15 and 20 wt%) were
prepared by melt mixing in a twin-screw extruder. Chemical treatments such as alkali treatment of the fiber and addition of
maleic anhydride grafted polypropylene (MA-g-PP) as coupling agent were performed to promote polymer/fiber interfacial adhesion so that mechanical performance can be
improved. The resulting composites were evaluated through hardness, melt flow index and tensile, flexural and impact strengths
as well as water absorption. Thermal analysis and Fourier transform infrared spectroscopy were also employed to characterize
the composites. The polymer/fiber interface was investigated through scanning electron microscopy analysis. The biodegradability
of composites was evaluated by compost-soil burial test. The addition of curauá fiber promoted an increase in the mechanical
strengths and composites treated with 2 wt% MA-g-PP with 20 wt% curauá fiber showed an increase of nearly 75% in tensile and 56% in flexural strengths besides an improvement
in impact strength with respect to neat polymer blend. Nevertheless, treated composites showed an increase in water absorption
and biodegradation tests showed that the addition of fiber retards degradation time. The retained mass of BP/20 wt% fiber
composite with MA-g-PP and neat BP was 68 and 26%, respectively, after 210 days of degradation test. 相似文献
34.
Schröder P Navarro-Aviñó J Azaizeh H Goldhirsh AG DiGregorio S Komives T Langergraber G Lenz A Maestri E Memon AR Ranalli A Sebastiani L Smrcek S Vanek T Vuilleumier S Wissing F 《Environmental science and pollution research international》2007,14(7):490-497
Goal, Scope and Background One of the burning problems of our industrial society is the high consumption of water and the high demand for clean drinking
water. Numerous approaches have been taken to reduce water consumption, but in the long run it seems only possible to recycle
waste water into high quality water. It seems timely to discuss alternative water remediation technologies that are fit for
industrial as well as less developed countries to ensure a high quality of drinking water throughout Europe.
Main Features The present paper discusses a range of phytoremediation technologies to be applied in a modular approach to integrate and
improve the performance of existing wastewater treatment, especially towards the emerging micro pollutants, i.e. organic chemicals
and pharmaceuticals. This topic is of global relevance for the EU.
Results Existing technologies for waste water treatment do not sufficiently address increasing pollution situation, especially with
the growing use of organic pollutants in the private household and health sector. Although some crude chemical approaches
exist, such as advanced oxidation steps, most waste water treatment plants will not be able to adopt them. The same is true
for membrane technologies.
Discussion Incredible progress has been made during recent years, thus providing us with membranes of longevity and stability and, at
the same time, high filtration capacity. However, these systems are expensive and delicate in operation, so that the majority
of communities will not be able to afford them. Combinations of different phytoremediation technologies seem to be most promising
to solve this burning problem.
Conclusions To quantify the occurrence and the distribution of micropollutants, to evaluate their effects, and to prevent them from passing
through wastewater collection and treatment systems into rivers, lakes and ground water bodies represents an urgent task for
applied environmental sciences in the coming years.
Recommendations Public acceptance of green technologies is generally higher than that of industrial processes. The EU should stimulate research
to upgrade existing waste water treatment by implementing phytoremediation modules and demonstrating their reliability to
the public. 相似文献
35.
Inhibitory effects of selenite and selenate towards hydrogenotrophic and acetoclastic methanogenesis were evaluated in anaerobic toxicity assays. The 50% inhibitory concentration (IC(50)) of both selenium oxyanions was below 6.1x10(-5)M in hydrogenotrophic assays, whereas acetoclastic methanogens were less inhibited: IC(50)=8.3x10(-5)M and 5.5x10(-4)M for selenite and selenate, respectively. Selenite completely inhibits methanogenesis from both substrates tested at concentrations 10(-3)M selenite, while only marginal methanogenic activities occur at equimolar concentrations of selenate. Selenite becomes irreversibly inhibitory upon a single exposure, whereas selenate inhibits methanogens upon repeated exposure. Consequently, methane recovery can be seriously hampered or even impossible during anaerobic treatment of highly selenium contaminated waste streams. 相似文献
36.
M J Martin G E Host K E Lenz J G Isebrands 《Environmental pollution (Barking, Essex : 1987)》2001,115(3):425-436
Predicting ozone-induced reduction of carbon sequestration of forests under elevated tropospheric ozone concentrations requires robust mechanistic leaf-level models, scaled up to whole tree and stand level. As ozone effects depend on genotype, the ability to predict these effects on forest carbon cycling via competitive response between genotypes will also be required. This study tests a process-based model that predicts the relative effects of ozone on the photosynthetic rate and growth of an ozone-sensitive aspen clone, as a first step in simulating the competitive response of genotypes to atmospheric and climate change. The resulting composite model simulated the relative above ground growth response of ozone-sensitive aspen clone 259 exposed to square wave variation in ozone concentration. This included a greater effect on stem diameter than on stem height, earlier leaf abscission, and reduced stem and leaf dry matter production at the end of the growing season. Further development of the model to reduce predictive uncertainty is discussed. 相似文献
37.
In eusocial insects, sex allocation often constitutes a ground for intracolonial conflicts. This occurrence provides ideal opportunities to test kin-selection theory. A vast literature on this topic is available for social Hymenoptera, but the same field remains almost untouched in termites. A preeminent case is that of some species of Coptotermes, where the sex-allocation ratio in nymphs shifts from near equity to all-male when the primary reproductives are replaced by neotenics. To shed light on the developmental origin of this shift, we compared the sex ratio of the various castes and instars in primary- and neotenic-headed mature colonies of Coptotermes lacteus. The male-biased sex allocation in the latter type of colony results from two concurrent events: first, the sex ratio of the youngest instars (larvae) is male-biased by a 3:1 ratio; and second, all female larvae become workers, while a large fraction of the male larvae proceed to the nymphal and alate stages. Colony-founding experiments showed that inbreeding by itself cannot account for the male bias at hatching. We suggest that both genetic factors, due to the reproductive behaviour of neotenics, and environmental factors (colony condition and resource availability) may influence this process. Their exact nature and respective impact have not yet been clarified. 相似文献
38.
Standing stock and size composition of the zooplankton comunity (>100 m) were studied in four depth strata of the upper 200 m of the water column during a Meteor cruise to the central Red Sea and Gulf of Aden in spring 1987. The central Red Sea was divided into a northern area of higher salinity and a less saline southern part. Both areas exhibited significant differences in zooplankton abundance and standing stock. The latter increased by the ratio 1:2:3 from the northern central Red Sea to its southern part and further south to the Gulf of Aden. For size structure analysis samples were fractionated into three size classes (100 to 300, 300 to 500, 500 to 5000 m). In the central Red Sea the smallest size was dominant whereas in the Gulf of Aden the largest size fraction played a greater relative role than in the central Red Sea. This shift in size structure of the zooplankton community from the Red Sea to the Gulf of Aden is apparently primarily related to ecosystem difference between both areas, leading to a change in species composition. In addition, size reduction of individual species common to both seas may be of some significance in the extreme environment of the Red Sea. 相似文献
39.
On detritus as a food source for pelagic filter-feeders 总被引:2,自引:0,他引:2
J. Lenz 《Marine Biology》1977,41(1):39-48
Data on the amount of organic detritus within the particle size fraction 1 to 150 are presented for the Western Kiel Bight. Grouped into a mixed surface layer and a stratified lower layer in accordance with the main hydrographic features of the Western Baltic Sea, the rounded-off values show a seasonal variation between 100 and 600 mg m-3 expressed as dry weight of organic matter. The overall average for both layers is about 200 mg m-3. Organic detritus thus comprises more than 40% of total organic matter in the above size class, which is the class most easily accessible to the relatively small filter-feeders in this area. Attempting to trace the origin of organic detritus, a positive correlation to phytoplankton standing stock was found in some cases, suggesting the predominance of autochthonous detritus. Proceeding from the assumption that pelagic filter-feeders select their food mainly by size and not by taste, it is concluded that organic detritus plays an important role as a supplementary food source, being ingested together with phytoplankton and small nonmotile heterotrophs. The nutritive value of detritus is increased by the adsorption of dissolved organic matter and above all through the subsequent colonization by bacteria, which utilize the dissolved substances. Detritus particles serving as a substratum for bacteria thus form a means whereby dissolved organic substances reenter the food chain. The ingestion of detritus by filter-feeders is, therefore, thought to be instrumental in increasing the effectivity of energy transfer from the primary to the secondary food-chain level. 相似文献
40.