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41.
利用微型动物削减剩余污泥量的研究 总被引:3,自引:0,他引:3
在污水的好氧生物处理过程中会产生大量的剩余污泥。污泥的浓缩、脱水、处理和处置需要花费大量的人力和物力 ,而且如果处置不当 ,很容易对环境造成二次污染。因此 ,最大限度减少剩余污泥的排放成为人们关注的问题。根据生态学的理论 ,加强微型动物对细菌的捕食作用 ,可使能量在从低营养级向高营养级传递过程中有一定的损失 ,同时污泥量得以减少。应用两段式生物反应器或者直接向曝气池中投加微型动物均可达到此目的。本文详细地介绍了这两种方法 ,讨论了各自的优点和不足 ,并指出了未来的发展方向 相似文献
42.
Faced with an intermittent but potent threat, animals exhibit behavior that allows them to balance foraging needs and avoid predators and over time, these behaviors can become hard-wired adaptations with both species trying to maximize their own fitness. In systems where both predator and prey share similar sensory modalities and cognitive abilities, such as with marine mammals, the dynamic nature of predator-prey interactions is poorly understood. The costs and benefits of these anti-predator adaptations need to be evaluated and quantified based on the dynamic engagement of predator and prey. Many theoretic models have addressed the complexity of predator-prey relationships, but few have translated into testable mechanistic models. In this study, we developed a spatially-explicit, geo-referenced, individual-based model of a prototypical adult dusky dolphin off Kaikoura, New Zealand facing a more powerful, yet infrequent predator, the killer whale. We were interested in two primary objectives, (1) to capture the varying behavioral game between a clever prey and clever predator based on our current understanding of the Kaikoura system, (2) to compare evolutionary costs vs. benefits (foraging time and number of predator encounters) for an adult non-maternal dusky dolphin at various levels of killer whale-avoidance behaviors and no avoidance rules. We conducted Monte Carlo simulations to address model performance and parametric uncertainty. Mantel tests revealed an 88% correlation (426 × 426 distance matrix, km2) between observed field sightings of dusky dolphins with model generated sightings for non-maternal adult dusky dolphin groups. Simulation results indicated that dusky dolphins incur a 2.7% loss in feeding time by evolving the anti-predator behavior of moving to and from the feeding grounds. Further, each evolutionary strategy we explored resulted in dolphins incurring an additional loss of foraging time. At low killer whale densities (appearing less than once every 3 days), each evolutionary strategy simulated converged towards the evolutionary cost of foraging, that is, the loss in foraging time approached the 2.7% loss experienced by evolving near shore-offshore movement behavior. However, the highest level of killer whale presence resulted in 38% decreases in foraging time. The biological significance of these losses potentially incurred by a dusky dolphin is dependent on various factors from dolphin group foraging behavior and individual energy needs to dolphin prey availability and behavior. 相似文献
43.
污水生物处理系统中内源过程的研究进展 总被引:4,自引:0,他引:4
污水生物处理系统的内源过程涉及到一系列微生物学、生态学机制和过程,因而对处理系统的各个方面都有重要影响.然而-目前对内源过程的认识还相当有限.本文首先在总结现有知识的基础上对污水生物处理系统中的内源过程作了定义,并对其区分为细胞和群落两个水平-随后,分别对内源过程中的细胞维持、解偶联、程序化细胞死亡、饥饿状态、高等微生物捕食等过程作了综述,总结了其在污水生物处理领域的研究进展.此外.文章还概述了细胞维持能量和细胞衰减速率的测定方法及其研究进展和存在的问题.本文的目的是通过综述现有的知识,推动对污水生物处理系统中内源过程研究的进一步发展. 相似文献
44.
Summary. Predation is a pervasive selective agent highly variable in space and time. Due to the costs associated with antipredator
responses, prey would be at a selective advantage if they respond to predation threats with an intensitfy matching the threat
posed by the predator. Many aquatic organisms have been shown to use chemical alarm cues present in the water to assess the
level of risk in their environment. This includes mosquito larvae which show antipredator responses to conspecific alarm cues.
In this study, we investigated the nature of the responses of larval mosquitoes Culex restuans to those cues. In our initial observations, we showed pond/population differences in the response intensity of C. restuans to alarm cues. In experiment 1, we showed that the response intensity to alarm cues could be increased by increasing the
background level of risk in the mosquitoes’ environment (by adding salamander predators) and once turned on, the response
intensity to alarm cues was likely maintained for the remainder of the mosquitoes’ aquatic life. In experiments 2 and 3, we
investigated if the increase in response intensity to alarm cues was directly correlated with the level of background risk
in the mosquitoes’ environment. When given increasing levels of background risk, mosquito larvae subsequently showed a graded
response to conspecific alarm cues. This series of experiments demonstrates that the response intensity of larval mosquitoes
to a standard concentration of alarm cues is not fixed, but rather dependent on the background level of risk in the environment.
An understanding of the background level of risk is particularly important for comparing antipredator responses of prey between
habitats. 相似文献
45.
TEDDY A. WILKIN‡ DANY GARANT† REW G. GOSLER BEN C. SHELDON 《Conservation biology》2007,21(5):1207-1217
Abstract: In contemporary fragmented landscapes, edges are commonplace, and understanding the effects of edge environments is thus essential for the conservation of forest communities. The reproductive output of forest passerines is often reduced close to forest edges. Possible explanations include overcrowding by conspecifics, elevated rates of predation, and the occurrence of lower-quality habitat and/or individuals at forest edges. We attempted to separate these processes by examining edge effects in the absence of nest predation and by effectively controlling for differences in breeding density and the quality of habitats and individuals. We used an edge distance index (EDI), which accounts for the number and distribution of edges in close proximity to a breeding location, to help explain variation in breeding density, nesting success, and reproductive traits of 8308 pairs of Great Tits ( Parus major ) breeding between 1965 and 2005, in Wytham, near Oxford, United Kingdom. Results from linear mixed modeling confirmed higher breeding density and a higher proportion of immigrant individuals at forest edges. Nevertheless, independently of these effects, we also found that birds laying later, with smaller clutches but larger eggs, were typical of edge environments. The number of offspring recruited to the breeding offspring per breeding attempt was also reduced at edges, both directly and mediated through changes in clutch size and laying date. Edge effects on life histories were detectable within individual females and up to 500 m from the woodland edge. Woodland edges are increasingly common in contemporary fragmented landscapes. Therefore these results, which suggest a pervasive effect of edges on reproduction, are of considerable importance to the management and conservation of forest communities. 相似文献
46.
Eisner T Schroeder FC Snyder N Grant JB Aneshansley DJ Utterback D Meinwald J Eisner M 《Chemoecology》2008,18(2):109-119
Summary. Beetles of the family Lycidae have long been known to be chemically protected. We present evidence that North American species
of the lycid genera Calopteron and Lycus are rejected by thrushes, wolf spiders, and orb-weaving spiders, and that they contain a systemic compound that could account,
at least in part, for this unacceptability. This compound, a novel acetylenic acid that we named lycidic acid, proved actively
deterrent in feeding tests with wolf spiders and coccinellid beetles. Species of Lycuscommonly figure as models of mimetic associations. Among their mimics are species of the cerambycid beetle genus Elytroleptus, remarkable because they prey upon the model lycids. We postulated that by doing so Elytroleptus might incorporate the lycidic acid from their prey for their own defense. However, judging from analytical data, the beetles
practice no such sequestration, explaining why they remain relatively palatable (in tests with wolf spiders) even after having
fed on lycids. Chemical analyses also showed the lycids to contain pyrazines, such as were already known from other Lycidae,
potent odorants that could serve in an aposematic capacity to forestall predatory attacks.
David Utterback: Deceased 相似文献
47.
David W. Pfennig George R. HarperJr Abel F. Brumo William R. Harcombe Karin S. Pfennig 《Behavioral ecology and sociobiology》2007,61(4):505-511
Batesian mimicry evolves when a palatable species, the “mimic,” resembles a dangerous species, the “model,” because both receive
protection from predation. Yet, this protection should break down where the model is absent, because predators in such areas
would not be under selection to avoid the model. Here, we test this prediction in a coral snake mimicry complex. We exposed
plasticine replicas of milk snakes that closely mimic coral snakes to natural predators to determine if good mimetic milk
snakes are preferentially attacked in allopatry with their model. Moreover, we evaluated whether attack rates on these replicas
varied among three different allopatric regions that differed in the type of mimic found locally (i.e., good mimic, poor mimic,
or no mimic). When all three regions were considered together, mimics were not preferentially attacked. When regions were
analyzed separately, however, attacks on mimics were significantly greater than randomness only where good mimics were found.
These variable levels of predation on good mimics might reflect frequency-dependent (i.e., apostatic) predation. In allopatric
regions where good mimics are present, predators might have learned or evolved preferences for conspicuous, palatable prey
that they encounter frequently. By contrast, in allopatric regions where good mimics are absent, predators might not have
learned or evolved preferences for novel phenotypes. Thus, when predation is frequency-dependent, as long as good mimics are
rare, they might not experience elevated levels of predation in allopatry with their model as predicted by the Batesian mimicry
hypothesis. 相似文献
48.
蠕虫污泥减量效果及其影响因素分析 总被引:19,自引:2,他引:17
研究了蠕虫生长在活性污泥法中试系统的污泥减量效果及其对出水水质的影响 ,同时对蠕虫生长的影响因素进行了初步分析 .结果表明 ,除了初始的20d之外 ,整个试验过程中均有蠕虫出现 ,其中红斑瓢体虫(Aeolosomahemprichicii)和仙女虫(Naiselinguis)交替占据优势地位 ,但红斑瓢体虫占据主导地位的时间长于仙女虫 ,而吻盲虫 (Pristinaaequiseta)只是偶尔存在 .蠕虫连续保持高密度生长 (曝气池中蠕虫总密度大于 30条 /mg)长达 172d .高密度下的蠕虫生长不仅能显著降低污泥产率 ,而且能明显提高污泥的沉降性能 .蠕虫密度越高 ,出水水质越差 .仙女虫比红斑瓢体虫具有更大的污泥减量能力 ,并且前者对出水水质的影响也大于后者 .蠕虫生长不影响硝化过程 ,但当仙女虫占优势时 ,蠕虫生长会导致出水PO343--P浓度的升高 .蠕虫生长影响因素的分析表明 ,只有污泥龄对 2种蠕虫的生长没有影响 ,但温度和水力停留时间均能显著影响它们的生长 . 相似文献
49.
50.