全文获取类型
收费全文 | 4480篇 |
免费 | 29篇 |
国内免费 | 8篇 |
专业分类
安全科学 | 71篇 |
废物处理 | 162篇 |
环保管理 | 194篇 |
综合类 | 1645篇 |
基础理论 | 945篇 |
环境理论 | 8篇 |
污染及防治 | 1116篇 |
评价与监测 | 192篇 |
社会与环境 | 178篇 |
灾害及防治 | 6篇 |
出版年
2022年 | 32篇 |
2019年 | 41篇 |
2018年 | 88篇 |
2017年 | 86篇 |
2016年 | 100篇 |
2015年 | 91篇 |
2014年 | 117篇 |
2013年 | 204篇 |
2012年 | 104篇 |
2011年 | 192篇 |
2010年 | 128篇 |
2009年 | 142篇 |
2008年 | 213篇 |
2007年 | 184篇 |
2006年 | 155篇 |
2005年 | 130篇 |
2004年 | 116篇 |
2003年 | 111篇 |
2002年 | 139篇 |
2001年 | 92篇 |
2000年 | 80篇 |
1999年 | 59篇 |
1998年 | 42篇 |
1997年 | 45篇 |
1996年 | 44篇 |
1995年 | 47篇 |
1994年 | 57篇 |
1993年 | 31篇 |
1992年 | 44篇 |
1991年 | 44篇 |
1990年 | 40篇 |
1989年 | 33篇 |
1984年 | 31篇 |
1981年 | 33篇 |
1977年 | 31篇 |
1976年 | 35篇 |
1967年 | 35篇 |
1966年 | 32篇 |
1965年 | 49篇 |
1964年 | 40篇 |
1963年 | 40篇 |
1962年 | 34篇 |
1961年 | 48篇 |
1960年 | 45篇 |
1959年 | 49篇 |
1958年 | 46篇 |
1957年 | 45篇 |
1956年 | 44篇 |
1955年 | 40篇 |
1954年 | 42篇 |
排序方式: 共有4517条查询结果,搜索用时 906 毫秒
921.
922.
923.
924.
925.
Jörgen I. Johnsson Karin Kjällman-Eriksson 《Behavioral ecology and sociobiology》2008,62(10):1613-1620
Little is known about how cryptic colouration influences prey search in near-surface aquatic habitats, although such knowledge
is critical for understanding the adaptive value of colour crypsis as well as the perceptive constraints influencing foraging
behaviour in these environments. This study had two main aims: (1) to investigate how background colour matching by prey affects
foraging efficiency by brown trout parr and (2) to investigate how foraging ability on cryptic and conspicuous prey is affected
by fish size at age (reflecting dominance). We addressed these questions by training wild brown trout parr to forage individually
on live brown-coloured maggots on a cryptic (brown) or conspicuous (green) background. A separate experiment confirmed the
absence of trout preference for brown or green substrate. The results show that prey background colour matching increases
search time in brown trout. Search time generally decreased by learning, but conspicuous prey remained an easier prey to find
throughout the six training trials. Thus, perceptive constraints appear to limit search efficiency for cryptic prey, suggesting
that cryptic colouration can confer survival benefits to prey in natural environments. Smaller fish generally found conspicuous
prey faster than larger individuals, whereas search time for cryptic prey was not influenced by body size. This suggests that
smaller individuals compensate for inferior competitive ability by increasing foraging activity rather than improving cognitive
ability. The technique of varying cognitive demands in behavioural tasks could be used more in future studies aimed at distinguishing
motivational effects from cognitive explanations for variation in behavioural performance. 相似文献
926.
Social information use is a process across time, space, and ecology, reaching heterospecifics 总被引:2,自引:0,他引:2
Decision making can be facilitated by observing other individuals faced with the same or similar problem, and recent research suggests that this social information use is a widespread phenomenon. Implications of this are diverse and profound: for example, social information use may trigger cultural evolution, affect distribution and dispersal of populations, and involve intriguing cognitive traits. We emphasize here that social information use is a process consisting of the scenes of (1) event, (2) observation, (3) decision, and (4) consequence, where the initial event is a scene in such a process of another individual. This helps to construct a sound conceptual framework for measuring and studying social information use. Importantly, the potential value of social information is affected by the distance in time, space, and ecology between the initial observation and eventual consequence of a decision. Because negative interactions between individuals (such as direct and apparent competition) also depend on the distance between individuals along these dimensions, the potential value of information and the negative interactions may form a trade-off situation. Optimal solutions to this trade-off can result in adaptively extended social information use, where using information gathered some time ago, some distance away, and from ecologically different individuals is preferred. Conceivably, using information gathered from a heterospecific individual might often be optimal. Many recent studies demonstrate that social information use does occur between species, and the first review of published cases is provided here. Such interaction between species, especially in habitat selection, has important consequences for community ecology and conservation. Adaptively extended social information use may also be an important evolutionary force in guild formation. Complex coevolutionary patterns may result depending on the effect of information use on the provider of information. 相似文献
927.
Ulrike Schulte-Oehlmann Jörg Oehlmann Wilhelm Püttmann 《Environmental Sciences Europe》2007,19(3):168-179
Background
The presence of a large spectrum of pharmaceutical agents has been reported for aquatic environments (surface—and groundwater) and other aquatic media (influents and effluents of sewage treatment plants) in Germany and beyond, including their occurrence in drinking water. Considering the large number of pharmaceuticals produced for human use and released into the environment, various authors (Sattelberger 1999, Hanisch et al. 2004, Castiglioni et al. 2006, IWW 2006, Stockholm County Council 2006) tried to compile ‘priority lists’ focusing on those substances with environmental relevance. The following agents are included in all lists: ciprofloxacine, clarythromycine (antibiotics), carbamazepine (anti-epileptic agent), bezafibrate (lipid reducer), clofibric acid (lipid reducer metabolite), ethinylestradiol (sex hormone) and cylophosfamide (cytostatic agent). The agents erythromycine and sulfamethoxazole (antibiotics), ibuprofen, indometacine, propyphenazone (analgesics), atenolol (beta-blocker) and ifosfamide (cytostatic agent) can be found in three of four priority lists.Results
Pharmaceuticals mainly enter the aquatic environment via effluent water, coming from wastewater treatment plants (including hospital and household sewerage), untreated discharges (e.g, secondary transfer of active agents into ground- and surface waters via sewage sludge application in agriculture and via landfill leachate) and leakages in the municipal sewer network.Discussion
Potential activities towards a reduced release of pharmaceuticals into the environment should consider primarily the origin of the exposure to allow a separation of drug containing flows already at the source. Following the latter it would be possible to minimize the contamination of spring-, ground- and surface waters which serve as raw water resources for drinking water supply. However, considering the actual water pollution with pharmaceuticals and other substances, ‘end-of pipe’ techniques in the sewage and drinking water treatment are absolutely essential.Conclusions
Sustainability criteria (e.g. protection of drinking water resources, habitats and biocoenoses, recycling and economizing use of resources) and economic aspects of modern sewage disposal concepts require a useful choice and combination of technical measures as components of centralized and decentralized sewage and drinking water treatment methods. It is though not realistic to cover and eliminate all pharmaceutical agents of environmental relevance equally effective even if a catalogue of potential technical treatment methods is elaborated thoroughly. Therefore, a concentration of efforts on selected drug agents, at least following initially some of the priority lists, is recommended.Recommendations and Perspectives
The contamination of the water cycle with pharmaceuticals is nevertheless not exclusively to be solved via the application of technical methods. The BMBF (Federal Ministry for Education and Research) funded project start (Management Strategies for Pharmaceuticals in Drinking Water, www.start-project.de) therefore tries by implementation of a transdisciplinary approach to integrate technical-, behavioral-, and agent-orientated management strategies towards a more comprehensive and sustainable problem solution. 相似文献928.
Background
Residues of pharmaceuticals are meanwhile detected widely in the aquatic environment. Waste water treatment plants are the main route of entry: after intake the agents or their metabolites are excreted predominantly via urine into the sewage. Largely unknown is, however, if the improper disposal of unused medicines via domestic sanitary devices (toilet or sink) contributes to the measured concentrations in the environment. Aim of this investigation was to clarify to what extent consumers in Germany dispose of unused medicines directly via domestic sewage. In July and August 2006 a representative survey of the population with 2.000 interviewees was performed for this purpose.Results
The analysis of the survey shows that the disposal of unused medicines via domestic sewage takes place on relevant scales: approx. 16% of the population dispose at least occasionally of unused or expired tablets in the toilet whereas 43% proceed alike with liquid drugs (toilet or sink).Discussion
A possible reason for this disposal behaviour is the widely inconsistent waste disposal communication by the municipalities and the federal states. The resulting uncertainty about the correct way to dispose of unused medicines gains in importance in the context of the high recycling willingness of the (German) population: appropriate disposal options for drug residues (tablets or liquids) arising from waste separation are often not realised.Conclusions
Quantitative assessments on the basis of the collected data demonstrate that the established frequency of direct disposal of unused medicines via domestic sewage can partly contribute significantly to the occurrence of pharmaceuticals in the aquatic environment. Crucial parameters are here the excretion rate of the active pharmaceutical ingredient considered and the actual amount of medication waste.Recommendations
Based on the inquiry results, measures that lead to a more adequate handling of pharmaceutical waste disposal are demanded. The establishment of a consistent and binding disposal standard for unused medicines via return in pharmacies is recommended. This measure needs to be accompanied by a simplification of the established take back systems which partly cause high time and effort for pharmacies. 相似文献929.
Elin A. Thomas Monika Böhm Caroline Pollock Chong Chen Mary Seddon Julia D. Sigwart 《Conservation biology》2022,36(2):e13854
Hydrothermal vents are rare deep-sea oases that house faunal assemblages with a similar density of life as coral reefs. Only approximately 600 of these hotspots are known worldwide, most only one-third of a football field in size. With advancing development of the deep-sea mining industry, there is an urgent need to protect these unique, insular ecosystems and their specialist endemic faunas. We applied the IUCN (International Union for the Conservation of Nature) Red List criteria to assess the extinction risk of vent-endemic molluscs with varying exposure to potential deep-sea mining. We assessed 31 species from three key areas under different regulatory frameworks in the Indian, West Pacific, and Southern Oceans. Three vent mollusc species were also examined as case studies of different threat contexts (protected or not from potential mining) to explore the interaction of local regulatory frameworks and IUCN Red List category assignment. We found that these assessments were robust even when there was some uncertainty in the total range of individual species, allowing assessment of species that have only recently been named and described. For vent-endemic species, regulatory changes to area-based management can have a greater impact on IUCN Red List assessment outcomes than incorporating additional data about species distributions. Our approach revealed the most useful IUCN Red List criteria for vent-endemic species: criteria B and D2. This approach, combining regulatory framework and distribution, has the potential to rapidly gauge assessment outcomes for species in insular systems worldwide. 相似文献
930.
Effects of heavy metals and nitroaromatic compounds on horseradish glutathione S-transferase and peroxidase 总被引:7,自引:0,他引:7
Glutathione S-transferase (GST) and peroxidase (POX) activities have a direct relation to the effect of stress on plant metabolism. Changes in the activities of the enzymes were therefore studied. Horseradish hairy roots were treated by selected bivalent ions of heavy metals (HMs) and nitroaromatic compounds (NACs). We have shown differences in GST activity when assayed with substrates 1-chloro-2,4-dinitrobenzene (CDNB) and 1,2-dichloro-4-nitrobenzene (DCNB). The conjugation of DCNB catalysed by GST was inhibited in all roots treated with HMs as compared to non-treated roots, whereas NACs caused induction of the activity in dependence on the exposition time and concentration of compounds. The conjugation of CDNB by GST was not affected to the same extent. The increase of GST activity was determined in cultures treated by nickel (0.1 mM) and diaminonitrotoluenes (DANTs, 0.1 mM) for 6 h, whereas the roots treated by 2,4,6-trinitrotoluene (TNT), 4-amino-2,6-dinitrotoluene (ADNT) and dinitrotoluene (DNT, 1.0 mM) needed 27 h treatment to induce the activity. The POX activity of cultures treated by HMs was inhibited to 17-35% in comparison to non-treated cultures. The POX activity of roots treated by TNT (0.1 and 1.0 mM) for 6 and 27 h and by ADNT (0.1 and 1.0 mM) for 6 h was inhibited. A partial increase of POX activity was measured in roots treated by all NACs for 27 h. The content of oxidized glutathione (GSSG) and reduced glutathione (GSH) in the roots differed significantly. It was followed as a symptom of the stress reaction of the plant metabolism to the effect of NACs and HMs. 相似文献