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951.
Hydrogeochemical considerations about the origin of groundwater salinization in some coastal plains of Elba Island (Tuscany,Italy) 总被引:1,自引:0,他引:1
Elena Giménez-Forcada Alberto Bencini Giovanni Pranzini 《Environmental geochemistry and health》2010,32(3):243-257
Several coastal plains of the Elba Island (Marina di Campo, Portoferraio, Schiopparello, Mola, Porto Azzurro and Barbarossa
plains) in Tuscany (Italy) were studied to determine the causes of decline in groundwater quality, using major ion chemistry
to establish the causes of groundwater salinization. The study demonstrates that salinization of coastal plain alluvial aquifers
is not simply linked to seawater intrusion but is also intimately related to inflows from adjacent aquifers. Ionic ratios,
correlation graphs and distribution value maps were employed as the means to understand the hydrochemistry of the study areas.
The Mg/Cl ratio in particular can be considered a good tracer to distinguish the main salinization processes that control
groundwater chemistry. Seawater intrusion only partly determines the chemistry of some groundwaters, which generally belong
to a chloride facies where the salinity is derived principally from freshwater–seawater mixing and the participation of cation
exchange. Proceeding inland groundwater quality seems to be principally determined by the inflow of Mg, Ca-HCO3 or Ca, Na-HCO3 waters formed from the weathering of silicate minerals in adjoining aquifers. Hydrolysis of these minerals is of prime importance
in controlling groundwater chemistry in adjacent alluvial plains. The lateral recharge flows introduce water with a different
chemical composition and this variable of freshwater recharge changes the hydrochemistry as a result of mixing between two
or more waters types. This situation is further complicated when seawater and base exchange reactions participate, due to
seawater intrusion. 相似文献
952.
Nicole B. Richoux Sébastien Jaquemet Bo T. Bonnevie Yves Cherel Christopher D. McQuaid 《Marine Biology》2010,157(8):1755-1766
During chick-rearing, albatrosses can alternate between long foraging trips that provide the main source of food for the adults
and short foraging trips that they use to feed their young. This flexibility in foraging behaviour can lead to differences
in diet composition between adults and chicks and implies that they may be vulnerable in different ways to food shortages.
The trophic ecology of the Grey-headed albatross Thalassarche chrysostoma was investigated at the sub-Antarctic Prince Edward Islands during the chick-rearing period in April 2006 using a combination
of approaches. Diets of adults and chicks were assessed using stable isotope ratios and fatty acid (FA) profiles of blood
and/or stomach oils, in addition to stomach contents analysis. Fish from the family Macrouridae and cephalopods (particularly
the onychoteuthid Kondakovia longimana) were the primary prey, whereas crustaceans (krill Euphausia superba) represented a smaller proportion of the stomach contents. Stomach oil FA profiles contained more monounsaturated FA than
the profiles of plasma, which were richer in saturated FA and arachidonic acid (20:4n-6). There was also a distinct separation
of adults from chicks, with higher levels of monounsaturates in chick plasma, and higher saturated FA levels (particularly
16:0) in the adult plasma. Stable carbon isotope ratios of whole blood were similar in adults and chicks, whereas stable nitrogen
isotope ratios showed significant enrichment by >1‰ in chicks. The combined FA, stable isotopes and stomach contents analyses
suggest clear differences in diet quality between adults and chicks, with chicks feeding at a higher trophic position through
feeding more on highly nutritious fish and adults keeping much of the less nutritious zooplankton for themselves. 相似文献
953.
Nicolas Sturaro Stéphane Caut Sylvie Gobert Jean-Marie Bouquegneau Gilles Lepoint 《Marine Biology》2010,157(2):237-247
The coexistence of three idoteid species in Posidonia oceanica litter raises the question of trophic diversity and their role in the litter degradation process. Hence, diet composition
of Idotea balthica, Idotea hectica and Cleantis prismatica was studied using a combination of gut contents and stable isotopes analysis. Gut content observations indicate that P. oceanica dead leaves are an important part of the ingested food for the three species, although their tissues are constituted of only
a small to medium fraction of P. oceanica carbon. Our results also underlined the potential role of these species in the degradation of P. oceanica litter by mechanically fragmenting the litter and by assimilating a small to medium fraction of carbon. Moreover, we showed
that there were considerable inter- and intra-specific differences in diet composition. Diet differed between juveniles and
adults for I. balthica. Crustaceans are an important food source for adults of I. balthica, while I. hectica indicated a major contribution of algal material. C. prismatica showed an intermediate diet. This trophic diversity is probably one of the factors allowing these species to coexist in the
same biotope. 相似文献
954.
Sophie Quérouil Luís Freitas Irma Cascão Filipe Alves Ana Dinis Joana R. Almeida Rui Prieto Silvia Borràs José A. Matos Diogo Mendonça Ricardo S. Santos 《Marine Biology》2010,157(11):2567-2580
Several cetacean species exhibit fine-scale population structure despite their high dispersal capacities and the apparent continuity of the marine environment. In dolphins, most studies have focused on coastal areas and continental margins, and they revealed differentiated populations within relatively small geographic areas, sometimes in conjunction with a specialisation for different habitats (ecotypes). We analysed the population genetic structure of short-beaked common dolphins (Delphinus delphis) and Atlantic spotted dolphins (Stenella frontalis) in the Azores and Madeira, the two most isolated archipelagos of the North Atlantic. The archipelago of the Azores is divided into three groups of islands and stands 900 km away from Madeira. It is not known whether individuals migrate between groups of islands and archipelagos, nor whether distinct ecotypes are present. These questions were investigated by genetic analyses of 343 biopsy samples collected on free-ranging dolphins. The analyses consisted in sequencing part of the mitochondrial hyper-variable region, screening up to 14 microsatellite loci, and molecular sexing. Results did not unravel any population structure at the scale of the study area. Lack of differentiation matches expectations for spotted dolphins, which are transient in both archipelagos, but not for common dolphins, which are present year-round in the Azores and potentially resident. Absence of genetic structure over hundreds and even thousands of kilometres implies the existence of gene flow over much larger distances than usually documented in small delphinids, which could be achieved through individual movements. This finding indicates that population structure in oceanic habitat differs from that observed in coastal habitat. 相似文献
955.
João Paulo Silva Author Vitae Mário Santos Author Vitae Author Vitae Domingos Leitão Author Vitae Author Vitae Márcia Pinto Author Vitae Author Vitae João Alexandre Cabral Author Vitae 《Ecological modelling》2010,221(16):1954-1963
Collision with conductors and earth cables is a known impact generated by transmission power lines, however there is virtually no information on how these infrastructures might affect bird distribution in a landscape context. With this work we specifically hypothesise that transmission power lines may affect the occurrence of a threatened bird, the little bustard (Tetrax tetrax). To test this hypothesis we used a Stochastic Dynamic Methodology (StDM), analysing the effects of power lines in a landscape perspective and simulating population trends as a response to power line installation and habitat changes induced by agricultural shifts in southern Portugal. The data used in the dynamic model construction included relevant gradients of environmental conditions and was sampled during the breeding seasons of 2003-2006. Transmission power lines were significantly avoided by the little bustard and the developed StDM model showed that the distance to these utility structures is the most important factor determining breeding densities in sites with suitable habitat for the species, which possibly leads to displacement of populations and habitat fragmentation. The model simulations also provided the base to analyse the cumulative effects caused by the habitat degradation that can ultimately lead to the extinction of local populations. Within priority conservation sites, the dismantling of existing transmission lines should be considered whenever possible, in order to ensure adequate breeding habitat. The model is considered useful as an auxiliary tool to be used in environmental impact assessments, management and conservation studies. 相似文献
956.
The background noise generated in large social aggregations of calling individuals is a potent source of auditory masking for animals that communicate acoustically. Despite similarities with the so-called "cocktail-party problem" in humans, few studies have explicitly investigated how non-human animals solve the perceptual task of separating biologically relevant acoustic signals from ambient background noise. Under certain conditions, humans experience a release from auditory masking when speech is presented in speech-like masking noise that fluctuates in amplitude. We tested the hypothesis that females of Cope's gray treefrog (Hyla chrysoscelis) experience masking release in artificial chorus noise that fluctuates in level at modulations rates characteristic of those present in ambient chorus noise. We estimated thresholds for recognizing conspecific advertisement calls (pulse rate=40-50 pulses/s) in the presence of unmodulated and sinusoidally amplitude modulated (SAM) chorus-shaped masking noise. We tested two rates of modulation (5 Hz and 45 Hz) because the sounds of frog choruses are modulated at low rates (e.g., less than 5-10 Hz), and because those of species with pulsatile signals are additionally modulated at higher rates typical of the pulse rate of calls (e.g., between 15-50 Hz). Recognition thresholds were similar in the unmodulated and 5-Hz SAM conditions, and 12 dB higher in the 45-Hz SAM condition. These results did not support the hypothesis that female gray treefrogs experience masking release in temporally fluctuating chorus-shaped noise. We discuss our results in terms of modulation masking, and hypothesize that natural amplitude fluctuations in ambient chorus noise may impair mating call perception. 相似文献
957.
Jorge M. Mendes Patrícia Cortés de Zea Bermudez José Pereira K. F. Turkman M. J. P. Vasconcelos 《Environmental and Ecological Statistics》2010,17(1):1-28
In Portugal, due to the combination of climatological and ecological factors, large wildfires are a constant threat and due
to their economic impact, a big policy issue. In order to organize efficient fire fighting capacity and resource management,
correct quantification of the risk of large wildfires are needed. In this paper, we quantify the regional risk of large wildfire
sizes, by fitting a Generalized Pareto distribution to excesses over a suitably chosen high threshold. Spatio-temporal variations
are introduced into the model through model parameters with suitably chosen link functions. The inference on these models
are carried using Bayesian Hierarchical Models and Markov chain Monte Carlo methods. 相似文献
958.
T. Gallé 《Environmental Sciences Europe》2010,22(6):656-660
The Water Framework Directive’s (WFD) choice of good ecological status as a metric of the immission situation in water bodies implicitly considers the exposure of biota to pollutants. However, the exposure concept lacks consequent links to food webs and substance cycles where sediments and suspended matter play an important role. This is traceable in monitoring as well as in evaluation schemes. This article identifies the major challenges towards a process-oriented approach. 相似文献
959.
Effects of atrazine and nicosulfuron on freshwater microalgae 总被引:2,自引:0,他引:2
Growth modifications caused by various concentrations of atrazine and nicosulfuron were monitored in closed and continuous culture of Chlorella vulgaris (chlorophyta), Navicula accommoda (diatomophyta), and Oscillatoria limnetica (cyanophyta). The concentration at which algal growth rate was reduced twofold (EC50) was determined in the three species for both herbicides. Comparatively, the two toxicants were applied at 10 microg/l level in microcosms inoculated with natural phytoplankton from Lake Geneva. The relative abundances of major phytoplanktonic species were measured by algal cell count at the beginning and at the end of each experiment. Atrazine and nicosulfuron have different targets in plant metabolism, respectively, photosystem II (PSII) and acetolactate synthase (ALS), and the expected effects were different. Generally, the cultured phytoplankton exhibited various sensitivities, depending on species or herbicide. In the microcosms, the major taxa of natural phytoplanktonic samples exhibited various patterns, from acute toxicity to growth enhancement. For example, the diatoms inside the community were not affected by atrazine and nicosulfuron, except for Stephanodiscus minutulus that was sensitive to both, and Asterionella/formosa that was sensitive only to nicosulfuron. The specific physiology and the relationships among the phytoplanktonic communities have to be carefully considered when one would try to predict the extent of herbicide action on natural phytoplankton using in vitro tests. There is a need to test the toxic effect on various cultured strains, representative of most of the taxonomic composition of natural communities, to take into account the wide range of sensitivities and reaction to herbicide contamination. But this is not enough to give a solid frame when transposing the results to the field, and the use of more ecologically relevant systems is recommended. 相似文献
960.
Magnago Rachel Faverzani de Alcântara Braglia Thiago de Aguiar Ana Carolina Baungarten Polyana Mendonça Bruno Afonso Büchele Silva Heloisa Regina Turatti Egert Paola Girotto Edivandro Júnior Américo Cruz Parma Gabriel Oscar Cremona 《Journal of Material Cycles and Waste Management》2021,23(3):1126-1140
Journal of Material Cycles and Waste Management - This article aims to study the mechanical strength and fire resistance of polyurethane/cement (PuCem) composites containing glass sludge and sludge... 相似文献