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1.
2.
Effects of soil amendments on the bioavailability of heavy metals from zinc mine tailings 总被引:2,自引:0,他引:2
A study was conducted to test the effects of soil amendments on the bioavailability of heavy metals in a zinc mine tailings containing soil to plants, using the Indian mustard plant (Brassica juncea) as a test organism. Zinc mine tailing containing soil was amended with humus soil (HS) and phosphatic clay (PC). The zinc mine tailing containing soil (ZMTS) was characterized for heavy metals. It was mixed with PC and HS, and four mixtures were prepared. The first mixture contained ZMTS, and served as a control. The second mixture contained ZMTS and PC in the ratio of 1:1 (w/w). The third mixture contained ZMTS and HS in the ratio of 1:1(w/w). The fourth mixture containing ZMTS, PC and HS in the ratio of (2:1:1) (w/w). A slight increase in the bioavailability of Pb, Cu, Zn and Mn was noticed with increase in the incubation time from 14 to 42 days. The bioavailability of Pb, Cu, Zn and Mn from ZMTS alone in Brassica plant was in the range of 94-99% up to 42 days. Addition of PC and HS to the ZMTS soil reduced the bioavailabilities of Pb by (15%), of Cu by (20%), of Zn by (20%) and of Mn by (25%) in the mustard plant. The data showed that PC in the presence of HS had a high affinity for the heavy metals in the order of Pb, Cu, Zn and Mn. 相似文献
3.
S. K. Jain G. N. Yoganarasimhan S. M. Seth 《Journal of the American Water Resources Association》1992,28(6):1037-1043
ABSTRACT: Many approaches are available for operation of a multipurpose reservoir during flood season; one of them is allocation of storage space for flood control. A methodology to determine a reservoir operation policy based on explicit risk consideration is presented. The objective of the formulation is to maximize the reservoir storage at the end of a flood season while ensuring that the risk of an overflow is within acceptable limits. The Dynamic Programming technique has been used to solve the problem. This approach has been applied to develop operation policies for an existing reservoir. The performance of the policy was evaluated through simulation and was found to be satisfactory. 相似文献
4.
A novel framework to classify marginal land for sustainable biomass feedstock production 总被引:1,自引:0,他引:1
To achieve food and energy security, sustainable bioenergy has become an important goal for many countries. The use of marginal lands to produce energy crops is one strategy for achieving this goal, but what is marginal land? Current definitions generally focus on a single criterion, primarily agroeconomic profitability. Herein, we present a framework that incorporates multiple criteria including profitability of current land use, soil health indicators (erosion, flooding, drainage, or high slopes), and environmental degradation resulting from contamination of surface water or groundwater resources. We tested this framework for classifying marginal land in the state of Nebraska and estimated the potential for using marginal land to produce biofuel crops. Our results indicate that approximately 1.6 million ha, or 4 million acres, of land (approximately 8% of total land area) could be classified as marginal on the basis of at least two criteria. Second-generation lignocellulosic bioenergy crops such as switchgrass ( Panicum virgatum L.), miscanthus (Miscanthus giganteus), native prairie grasses, and short-rotation woody crops could be grown on this land in redesigned landscapes that meet energy and environmental needs, without significant impacts on food or feed production. Calculating tradeoffs between the economics of redesigned landscapes and current practices at the field scale is the next step for determining functional designs for integrating biofuel feedstock production into current land management practices. 相似文献
5.
Disturbance regimes,resilience, and recovery of animal communities and habitats in lotic ecosystems 总被引:6,自引:0,他引:6
Disturbance regime is a critical organizing feature of stream communities and ecosystems. The position of a given reach in
the river basin and the sediment type within that reach are two key determinants of the frequency and intensity of flow-induced
disturbances. We distinguish between predictable and unpredictable events and suggest that predictable discharge events are
not disturbances.
We relate the dynamics of recovery from disturbance (i.e., resilience) to disturbance regime (i.e., the disturbance history
of the site). The most frequently and predictably disturbed sites can be expected to demonstrate the highest resilience.
Spatial scale is an important dimension of community structure, dynamics, and recovery from disturbance. We compare the effects
on small patches (⩽1 m2) to the effects of large reaches at the river basin level. At small scales, sediment movements and scour are major factors
affecting the distribution of populations of aquatic insects or algae. At larger scales, we must deal with channel formation,
bank erosion, and interactions with the riparian zone that will affect all taxa and processes.
Our understanding of stream ecosystem recovery rests on our grasp of the historical, spatial, and temporal background of contemporary
disturbance events. 相似文献
6.
Polycyclic aromatic hydrocarbons (PAHs) have earned considerable attention due to their widespread environmental distribution and toxicity. In the environment, PAHs decompose by a variety of biotic and abiotic pathways. In both polar and nonpolar environments, phenanthrene (Phe, a common, three-ring PAH) is converted by sunlight to more polar products such as 9,10-phenanthrenequinone (PheQ) and subsequent oxidation products such as the corresponding open-ring dicarboxylic acid product. Biodegradation of phenanthrene also usually leads to oxidative metabolites, and eventually ends in mineralization. Our experimental objective was to investigate the photodegradation of phenanthrene and determine the effect of reaction products such as PheQ on microbial biodegradation of two- and three-ring PAHs. Abiotic experiments were performed to examine the photolytic breakdown of Phe; Phe was converted to PheQ, which catalyzed its own formation. In biodegradation experiments PheQ (0.04-4 mg/L) caused marked inhibition of naphthalene (Nap) biodegradation by a Burkholderia species; Phe did not. Only 20% of the naphthalene was degraded in the presence of PheQ compared with 75% in the control culture with no PheQ added. No PAH-degrading cultures were able to use PheQ as sole carbon source; however, the Phe-degrading enrichment culture dominated by a Sphingomonas species was able to degrade PheQ cometabolically in the presence of Phe. These results may explain why photooxidized phenanthrene-containing mixtures can resist biodegradation. 相似文献
7.
8.
Endocrine disrupting compounds (EDCs) are exogenous environmental chemicals that can interfere with normal hormone function and present a potential threat to both environmental and human health. The fate, distribution and degradation of EDCs is a subject of considerable investigation. To date, several studies have demonstrated that conventional water treatment processes are ineffective for removal of most EDCs and in some instances produce multiple unknown transformation products. In this study we have investigated the use of direct photolysis with low-pressure (LP) Hg UV lamps and UV+hydrogen peroxide (H(2)O(2)) advanced oxidation process (AOP) for the degradation of a prototypic endocrine disrupter, bisphenol A (BPA), in laboratory water. Removal rates of BPA and formation of degradation products were determined by high performance liquid chromatography (HPLC) analysis. Changes in estrogenic activity were evaluated using both in vitro yeast estrogen screen (YES) and in vivo vitellogenin (VTG) assays with Japanese medaka fish (Oryzias latipes). Our results demonstrate that UV alone did not effectively degrade BPA. However, UV in combination with H(2)O(2) significantly removed BPA parent compound and aqueous estrogenic activity in vitro and in vivo. Removal rates of in vivo estrogenic activity were significantly lower than those observed in vitro, demonstrating differential sensitivities of these bioassays and that certain UV/AOP metabolites may retain estrogenic activity. Furthermore, the UV/H(2)O(2) AOP was effective for reducing larval lethality in treated BPA solutions, suggesting BPA degradation occurred and that the degradation process did not result in the production of acutely toxic intermediates. 相似文献
9.
In the current paper, we studied downtime at work. Downtime represents a unique aspect of work time, as employees have low workload and more discretion about their activities but are still paid to be at work. Despite its prevalence and potentially significant implications for productivity and well‐being, the experience of downtime has not been a focus in the literature. To study this phenomenon, we first used a qualitative method involving 15 focus groups. Results from 95 employees showed that downtime is distinct from formal breaks and withdrawal behavior and is generally a negative subjective experience. Categories of antecedents of experience and downtime activities were classified. Next, to further explore the phenomenon, and based on Study 1 and relevant literature, we proposed several hypotheses and tested them using an experience sampling method. Results from 86 employees (across 5 workdays and 689 data points) indicated that the amount of downtime was negatively related to day level job satisfaction, job performance, and subjective health. The duration of relaxation activities during downtime mitigated the negative effects of downtime on fatigue. The effects of enjoyment level of the activities, job autonomy, work engagement, and boredom proneness were also examined. Implications, limitations, and future research are discussed. 相似文献
10.
Gita R. Kolluru Gregory F. Grether Heidy Contreras 《Behavioral ecology and sociobiology》2007,61(5):689-701
Food availability is expected to influence the relative cost of different mating tactics, but little attention has been paid
to this potential source of adaptive geographic variation in behavior. Associations between the frequency of different mating
tactics and resource availability could arise because tactic use responds directly to food intake (phenotypic plasticity),
because populations exposed to different average levels of food availability have diverged genetically in tactic use, or both.
Different populations of guppies (Poecilia reticulata) in Trinidad experience different average levels of food availability. We combined field observations with laboratory “common
garden” and diet experiments to examine how this environmental gradient has influenced the evolution of male mating tactics.
Three independent components of variation in male behavior were found in the field: courtship versus foraging, dominance interactions,
and interference competition versus searching for mates. Compared with low-food-availability sites, males at high-food-availability
sites devoted more effort to interference competition. This difference disappeared in the common garden experiment, which
suggests that it was caused by phenotypic plasticity and not genetic divergence. In the diet experiment, interference competition
was more frequent and intense among males raised on the greater of two food levels, but this was only true for fish descended
from sites with low food availability. Thus, the association between interference competition and food availability in the
field can be attributed to a genetically variable norm of reaction. Genetically variable norms of reaction with respect to
food intake were found for the other two behavioral components as well and are discussed in relation to the patterns observed
in the field. Our results indicate that food availability gradients are an important, albeit complex, source of geographic
variation in male mating strategies. 相似文献