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301.
To balance advantages and disadvantages of group living, some species have fission-fusion social systems in which members of the same group form frequently changing subgroups. This allows flexible responses of group size to external conditions while at the same time retaining group stability. In chimpanzees, subgroup (party) size and composition depend mainly on the presence of receptive females, food availability and the activity of the party. Here we analyse the extent to which fission-fusion parameters are influenced by changes of demographic variables like community size and composition. Data were collected from a habituated West African chimpanzee community (Taï forest, Côte dIvoire) over 10 years, during which total community size decreased from 51 to 21, and the number of adult males decreased from 9 to 2. Taï chimpanzees are highly gregarious, as they spend more than 80% of their time with unrelated conspecifics. With decreasing community size, party size, party duration and male-female association increased. Neither activity nor the presence of receptive females or feeding competition could explain the observed changes in grouping patterns. Thus, the decrease in community size led to an increase of party cohesion and also enhanced cohesiveness between the sexes, while general sociality remained unchanged. Therefore, our data support the notion that small communities are more cohesive and have a less flexible fission-fusion system.Communicated by D. Watts 相似文献
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303.
The all-season vegetable known as waterleaf (Talinum triangulare) is extensively grown in Nigeria's metropolistan market gardens. This paper examines the soil compositions of some of the cultivation areas for this crop to determine the impacts of its very intensive repetitive cultivation. In general, the regular application of organic manures and mineral fertilizers has maintained the fertility status of the market garden soils. Multiple regression analysis indicated that base saturation, available phosphorus and organic matter were the most significant determinants to variations in crop production. 相似文献
304.
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306.
Julia Elena Serpa 《生态毒理学报》2000,22(2):32-34
咖啡种植、加工和流通既有积极的环境影响也有消极的环境影响.寿命周期分析是可以用来找到缓解这些消极影响的途径的手段之一.一个简单模式的系统化应当有社会经济性质的附加分析加以补充.当提请人们注意与咖啡生产链有关的问题时,即使旨在找到和提出与当地需要相适应的替代办法,也不应当忘记咖啡业给咖啡种植地区以及加工(洗涤、选择、炒制、研磨和掺合)地区带来很多效益. 相似文献
307.
Hillier Oam N Gennissen J Pickering B Smolenski R Brown P 《Journal of environmental management》2009,90(4):1605-1612
The perspectives of residents are brought together in this assembly of statements concerning the management of hexachlorobenzene waste in Botany, a southeastern suburb of Sydney. The paper indicates how residents have responded as participants in public participation exercises, and the contribution made by lay experts in the search for a negotiated solution to the problems of legacy wastes. Resident comments on the role of independent scientific experts, on legal liability, and on the State Government sponsored Commission of Inquiry, indicate the deficit of resources faced by the local community. The paper provides insights into the status of citizen knowledge in environmental controversies and the pitfalls of participatory processes. 相似文献
308.
Alice A. Han Emily B. Fabyanic Julie V. Miller Maren S. Prediger Nicole Prince Julia A. Mouch Jonathan Boyd 《Environmental monitoring and assessment》2017,189(4):190
Thousands of gallons of industrial chemicals, crude 4-methylcyclohexanemethanol (MCHM) and propylene glycol phenyl ether (PPh), leaked from industrial tanks into the Elk River in Charleston, West Virginia, USA, on January 9, 2014. A considerable number of people were reported to exhibit symptoms of chemical exposure and an estimated 300,000 residents were advised not to use or drink tap water. At the time of the spill, the existing toxicological data of the chemicals were limited for a full evaluation of the health risks, resulting in concern among those in the impacted regions. In this preliminary study, we assessed cell viability and plasma membrane degradation following a 24-h exposure to varying concentrations (0–1000 μM) of the two compounds, alone and in combination. Evaluation of different cell lines, HEK-293 (kidney), HepG2 (liver), H9c2 (heart), and GT1-7 (brain), provided insight regarding altered cellular responses in varying organ systems. Single exposure to MCHM or PPh did not affect cell viability, except at doses much higher than the estimated exposure levels. Certain co-exposures significantly reduced metabolic activity and increased plasma membrane degradation in GT1-7, HepG2, and H9c2 cells. These findings highlight the importance of examining co-exposures to fully understand the potential toxic effects. 相似文献
309.
The main objective of this paper is to present a model for generating synthetic rainfall totals on various timescales to be
applicable for a variety of uses. Many large-scale ecological and water resource models require daily, monthly and yearly
rainfall data as input to the model. As historical data provides only one realisation, synthetic generated rainfall totals
are needed to assess the impact of rainfall variability on water resources systems (Srikanthan, In: MODSIM2005, Melbourne,
Dec. 2005, pp. 1915–1921, 2005). Thus, our preferred model should simulate rainfall for yearly, monthly and daily periods. We believe that, for water supply
issues, no higher resolution is needed, although higher resolution would be useful in models designed to measure the risk
of local flooding. The critical factors are daily, monthly and yearly totals and daily, monthly and yearly variation. A model
for generating yearly totals will be described using traditional time series methods. This model, along with a similarly constructed
daily generation model by Piantadosi et al. (A New Model for Correlated Daily Rainfall, 2008), will be cascaded to start with a synthetic yearly total, then generate a synthetic sequence of monthly totals (through
selection from a large number of realisations) that match the yearly total, and subsequently perform a similar operation for
sequences of daily totals to match the required monthly totals. We present a new model for the generation of synthetic monthly
rainfall data, which we demonstrate for Parafield in Adelaide, South Australia. The rainfall for each month of the year is
modelled as a non-negative random variable from a mixed distribution with either a zero outcome or a strictly positive outcome.
We use maximum likelihood to find parameters for both the probability of a zero outcome and the gamma distribution that best
matches the observed probability density for the strictly positive outcomes. We describe a new model that generates correlated
monthly rainfall totals using a diagonal band copula with a single parameter to generate lag-1 correlated random numbers.
Our model preserves the marginal monthly distributions and, hence, also preserves the monthly and yearly means. We show that,
for Parafield, the correlation between rainfall totals for successive months is not significant, and so, it is reasonable
to assume independence. This is, however, not true for daily rainfall. We describe a new model that generates correlated daily
rainfall totals using a diagonal band copula with a single parameter to generate lag-1 correlated random numbers.
This is an extended version of a paper presented at the 17th Biennial Congress on Modelling and Simulation, Christchurch,
New Zealand, December 2007. 相似文献
310.
We consider the management of urban stormwater in two connected dams. Stormwater generated by local rainfall flows into a
capture dam and is subsequently pumped into a similar sized holding dam. We assume random gross inflow and constant demand.
If we wish to minimise overflow from the system then the optimal management policy is to pump as much water as possible each
day from the capture dam to the holding dam without allowing the holding dam to overflow. We shall refer to this policy as
the pump-to-fill policy. The model is based on the Parafield stormwater management system in the City of Salisbury (CoS) but assumes constant
demand instead of level dependent outflow. If there is insufficient water in the holding dam to meet the desired daily demand
then all water in the holding dam is used and the shortfall is obtained from other sources. CoS, in suburban Adelaide in South
Australia, is recognised in local government circles as a world leader in urban stormwater management. The water is supplied
to local industry to replace regular mains water and is also used to restore and maintain urban wetlands. In mathematical
terms the pump-to-fill policy defines a Markov chain with a large transition matrix and a characteristic regular block structure.
We use specialised Matrix Analytic Methods to decompose the event space and find simplified equations for the steady state
probability vector. In this way we enable an elementary solution procedure which we illustrate by solving the modified Parafield
problem. The optimal nature of the pump-to-fill policy is established in a recent paper by Pearce et al. (JIMO 3(2):313–320,
2007). The purpose of the current study is to find optimal management policies for urban stormwater systems.
Work supported by the Australian Research Council. 相似文献