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241.
Arnold Münster 《Die Naturwissenschaften》1948,35(11):343-344
242.
C. Santhi N. Kannan J. G. Arnold M. Di Luzio 《Journal of the American Water Resources Association》2008,44(4):829-846
Abstract: Physically based regional scale hydrologic modeling is gaining importance for planning and management of water resources. Calibration and validation of such regional scale model is necessary before applying it for scenario assessment. However, in most regional scale hydrologic modeling, flow validation is performed at the river basin outlet without accounting for spatial variations in hydrological parameters within the subunits. In this study, we calibrated the model to capture the spatial variations in runoff at subwatershed level to assure local water balance, and validated the streamflow at key gaging stations along the river to assure temporal variability. Ohio and Arkansas‐White‐Red River Basins of the United States were modeled using Soil and Water Assessment Tool (SWAT) for the period from 1961 to 1990. R2 values of average annual runoff at subwatersheds were 0.78 and 0.99 for the Ohio and Arkansas Basins. Observed and simulated annual and monthly streamflow from 1961 to 1990 is used for temporal validation at the gages. R2 values estimated were greater than 0.6. In summary, spatially distributed calibration at subwatersheds and temporal validation at the stream gages accounted for the spatial and temporal hydrological patterns reasonably well in the two river basins. This study highlights the importance of spatially distributed calibration and validation in large river basins. 相似文献
243.
Laturnus Frank von Arnold Karin Grn Christian 《Environmental science and pollution research international》2007,14(1):53-60
Goal, Scope and Background Sewage sludge produced in wastewater treatment contains large amounts of organic matter and nutrients and could, therefore,
be suitable as fertiliser. However, with the sludge, besides heavy metals and pathogenic bacteria, a variety of organic contaminants
can be added to agricultural fields. Whether the organic contaminants from the sludge can have adverse effects on human health
and wildlife if these compounds enter the food chain or groundwater still remains a point of controversial discussion.
Main Features This paper presents an overview on the present situation in Europe and a summary of some recent results on the possible uptake
of organic contaminants by crops after addition to agricultural fields by sewage sludge.
Results Greenhouse experiments and field trials were performed to study the degradation and uptake of organic micro-contaminants in
sludge-amended agricultural soil in crops, such as barley and carrots grown in agricultural soil amended with anaerobically-treated
sewage sludge from a wastewater treatment plant, but studies hitherto have revealed no immediate risks. Common sludge contaminants
such as linear alkylbenzene sulphonates (LAS), nonylphenol ethoxylates (NPE), polycyclic aromatic hydrocarbons (PAH), bis(diethylhexyl)
phthalate (DEHP), showed neither accumulation in soil nor uptake in plants.
Discussion It is assumed that the annual amount of sewage sludge produced in Europe will increase in the future, mainly due to larger
amounts of high quality drinking water needed by an increasing population and due to increasing demands for cleaner sewage
water. Application of sewage sludge to agricultural soils is sustainable and economical due to nutrient cycling and disposal
of sewage sludge. However, this solution also involves risks with respect to the occurrence of organic contaminants and other
potentially harmful contents such as pathogens and heavy metals present in the sludge. There have been concerns that organic
contaminants may accumulate in the soil, be taken up by plants and thereby transferred to humans via the food chain. Results
obtained so far revealed, however, no immediate risk of accumulation of common organic sludge contaminants in soil or uptake
in plants when applying sewage sludge to agricultural soil. With very high dosages of sewage sludge, there may be a risk for
accumulation of very apolar contaminants, such as DEHP, to the soil.
Conclusions Any conclusions on the safe use of sewage sludge in agriculture have to be drawn carefully, as the studies performed until
now have been limited. Further studies are required, and before final statements can be drawn, it is imminent to study a larger
variety of common crops and the effect sewage sludge application may have on a possible accumulation of organic contaminants
in the crops. Furthermore, a larger variety of organic contaminants need to be studied and special focus should be given to
contaminants newly introduced into the environment. Besides investigating possible plant uptake of organic contaminants, the
fate of these compounds in soil after sludge application need to be monitored too. Here, special attention has to begiven
to studies on degradation and the formation of degradation products, to weathering and to leaching effects on groundwater,
to the application of different crops on the same field (crop rotation), to the use of full-width tillage and strip tillage,
and to long term application of sewage sludge on the soil.
Recommendations and Perspectives There are environmental, political as well as economical incentives to increase the agricultural application of sludge. However,
such usage should be performed with care as there are also ways in which sludge fertilisation could harm the environment and
human health. Recently, a new European COST Action (859) has been established covering the field of food safety and improved
food quality. Part of the Action is dealing with the application of sewage sludge in agriculture. Before any political and
economical measures can be taken, the pros and cons have to be sufficiently investigated on a scientific level first.
ESS-Submission Editor: Prof. Elena Maestri (elena.maestri@unipr.it) 相似文献
244.
This study investigated the effects of individuals' affective traits (i.e., affect intensity and affect disposition) and affective states (i.e., positive and negative mood) on their motivations and behavior during episodes of organizational conflict. Two hundred and twenty‐three student employees from a variety of jobs and organizations kept daily records, for a three day period, of their conflict experiences at work. The results of hierarchical linear modelling indicated that employees' affective traits and affective states had parallel effects on the conflict management process. Subsequent analyses revealed the source of this parallelism: employees' moods on the day of the conflict fully mediated the effects of their affective disposition on the conflict process variables. The results are discussed in terms of their theoretical significance and practical implications. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
245.
E. C. Pariser L. Gilbert N. Hazon K. E. Arnold J. A. Graves 《Behavioral ecology and sociobiology》2012,66(4):519-527
Females are expected to partition resources between offspring in a context-dependent way to maximise total fitness returns
from a reproductive attempt. Female zebra finches (Taeniopygia guttata) vary the allocation of yolk androgens and antioxidants among offspring. Importantly, the balance between androgens and antioxidants
in yolks may be more important than their independent absolute amounts in terms of fitness consequences for developing young.
Therefore, we tested whether the relative allocation of these two resources in yolks varies according to either the Trivers–Willard,
positive or compensatory maternal investment hypothesis. We manipulated male attractiveness using coloured leg bands (red-banded
males appear attractive; green-banded males, unattractive) and measured yolk androgens and antioxidants in each egg, egg sex,
clutch sex ratio and female condition. While female zebra finches manipulated the balance of androgens and antioxidants within
and between clutches in response to mate attractiveness, offspring sex and their own condition, they did not do so in a way
that consistently followed any of the hypotheses. Mothers paired with unattractive males allocated a larger antioxidant/androgen
ratio to daughters than sons. This pattern was reversed when paired to an attractive male; sons received a larger antioxidant/androgen
ratio than daughters. We also found offspring sex ratio decreased with increasing female condition for unattractive males,
but not for attractive males. However, without knowing the fitness consequences of the balance of different egg constituents,
it is difficult to interpret the patterns consistently in terms of the Trivers–Willard, compensatory and positive investment
hypotheses. 相似文献
246.
Diversity, host affinity, and distribution of seed-infecting fungi: a case study with Cecropia 总被引:1,自引:0,他引:1
Recruitment limitation has been proposed as an important mechanism contributing to the maintenance of tropical tree diversity. For pioneer species, infection by fungi significantly reduces seed survival in soil, potentially influencing both recruitment success and adult distributions. We examined fresh seeds of four sympatric Cecropia species for evidence of fungal infection, buried seeds for five months in common gardens below four C. insignis crowns in central Panama, and measured seed survival and fungal infection of inviable seeds. Seed survival varied significantly among species and burial sites, and with regard to local (Panama) vs. foreign (Costa Rica) maternal seed sources. Fresh seeds contained few cultivable fungi, but > 80% of soil-incubated seeds were infected by diverse Ascomycota, including putative pathogens, saprophytes, and endophytes. From 220 isolates sequenced for the nuclear internal transcribed spacer region (ITS), 26 of 73 unique genotypes were encountered more than once. Based on the most common genotypes, fungal communities demonstrate host affinity and are structured at the scale of individual crowns. Similarity among fungal communities beneath a given crown was significantly greater than similarity among isolates found under different crowns. However, the frequency of rare species suggests high fungal diversity and fine-scale spatial heterogeneity. These results reveal complex plant-fungal interactions in soil and provide a first indication of how seed survival in tropical forests may be affected by fungal community composition. 相似文献
247.
The dynamics of shifting cultivation captured in an extended Constrained Cellular Automata land use model 总被引:3,自引:0,他引:3
Rohan Chandralal Wickramasuriya Arnold K. Bregt Hedwig van Delden Alex Hagen-Zanker 《Ecological modelling》2009
This paper presents an extension to the Constrained Cellular Automata (CCA) land use model of White et al. [White, R., Engelen, G., Uljee, I., 1997. The use of constrained cellular automata for high-resolution modelling of urban land-use dynamics. Environment and Planning B: Planning and Design 24(3), 323–343] to make it better suited for modelling the dynamics of shifting cultivation. In the extended model the time passed since the last land use transition of a location is a factor of its land use potential. The model can now account for the gradual decrease in soil fertility after an area of forest has been cleared for cultivation and also capture the process of regeneration once the plot is fallowed. The model is applied for the Ruhunupura area of Sri Lanka where chena, a particular practice of shifting cultivation, is a common land use that dominates the landscape dynamics. The model is calibrated for the period 1985–2001 and the results are assessed in terms of location to location overlap as well as structural similarity at multiple scales. These results give confidence in the representation of land use dynamics for the main land use classes. On the basis of a long term scenario run for the period 2001–2030, it is verified that the model captures stylized facts related to chena dynamics, in particular shortening fallow periods and increasingly long cultivation periods of chena, as a result of increasing land use pressure. 相似文献
248.
249.
On 21 September 1999, the Ji Ji earthquake killed 2,347 people. In the immediate aftermath the international community, mobilised rapidly and sent urban search-and-rescue (US&R) teams to the scene. This paper will present an annotated survey of the expertise and standard of equipment of international US&R teams following that earthquake which could serve as a blueprint for the establishment of US&R teams elsewhere at risk from earthquakes. 相似文献
250.
ABSTRACT: Common constraints in using existing mathematical models are the lack of appropriate input data and inadequate time and money to perform the modeling. A decision support system was developed to aid in selecting inputs to a basin scale soil and water resources model. The system prompts users for input values and formats them in the model input file. The system also accesses large data bases, interfaces with expert systems, gives explanations, suggests default values, and provides graphics. Technology transfer will be enhanced by decreasing the time and money spent during model use and increasing user confidence in the model. 相似文献