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181.
Jean E. Weber Chester C. Kisiel Lucien Ducksteiri 《Journal of the American Water Resources Association》1973,9(6):1075-1088
ABSTRACT: Many difficulties exist in the matching of models with data. This paper identifies elements of this problem and discusses considerations involved in model evaluation. The well known multivariate linear regression model is used to illustrate the distinctions between accuracy and precision and between estimation and prediction (because the model is commonly misused.) No amount of additional data will improve the accuracy of a poor model. A high R2, while indicative of a good matching between the observed data and model estimates, is a poor criterion for judging adequacy of the model to make good predictions of future events. Model evaluation also includes the problem of introducing secondary data and proxy variables into a model. Secondary data frequently enter, for example, the mass, energy and water budget equations because of difficulties in measuring the primary variables. Proxy variables arise because of a desire to collapse a vector of incomparable values, say, of water quality into a single number. Review of the above issues indicates that model evaluation is a multi-criterion problem, often imbedded in a larger framework where models are intended to meet multiple objectives. The mismatch of models and data has increasing legal and social consequences. 相似文献
182.
183.
The Science of Nature - 相似文献
184.
Relevance of BFRs and thermal conditions on the formation pathways of brominated and brominated-chlorinated dibenzodioxins and dibenzofurans 总被引:7,自引:0,他引:7
The widespread use of brominated flame-retarded products in the last two decades has resulted in an increasing presence of bromine in thermal processes such as waste combustion and accidental fires. Brominated and brominated-chlorinated dibenzodioxins and dibenzofurans (PBDDs/PBDFs, PXDDs/PXDFs) are micropollutants of concern arising from such processes. The present review aims to evaluate the relevance of these compound classes in actual thermal processes. Four categories of thermal processes are discussed in this respect according to their potential for PBDD/PBDF and PXDD/PXDF generation: thermal stress, pyrolysis/gasification, insufficient combustion conditions and controlled combustion conditions. Under thermal stress situations, as they may occur in production or recycling processes, PBDDs/PBDFs precursors like polybrominated diphenylethers (PBDE) can have a relevant potential for PBDD/PBDF formation via a simple elimination. Under insufficient combustion conditions as they are present in, e.g. accidental fires and uncontrolled burning as well as gasification/pyrolysis processes, considerable amounts of PBDDs/PBDFs can be formed from BFRs, preferably via the precursor pathway. In contrast, under controlled combustion conditions, BFRs and PBDDs/PBDFs can be destroyed with high efficiency. The relevance of de novo synthesis of PXDDs/PXDFs is discussed for this condition.Providing a basis for the understanding of PXDD/PXDF formation in actual thermal processes, the present paper also summarises the formation pathways of brominated and brominated-chlorinated PXDDs/PXDFs from brominated flame retardants (BFRs) investigated during laboratory thermolysis experiments. Relevant mechanistic steps for PBDD/PBDF formation from brominated precursors are discussed including elimination reactions, condensation steps and debromination/hydrogenation reactions.In addition, chlorination/bromination and halogen exchange reactions are briefly discussed with respect for their relevance on the final distribution of PBDDs/PBDFs, mixed chlorinated PXDDs/PXDFs and PCDDs/PCDFs resulting from thermal processes. 相似文献
185.
This paper analyzes five major causes of park-people conflicts that have occurred in Nepal's Royal Chitwan National Park.
The causes include illegal transactions of forest products from the park, livestock grazing in the park, illegal hunting and
fishing, crop damage, and threats to human and animal life caused by wild animals from the park. The conflicts indicate a
reciprocal relationship between the park and local people. They reflect the attitudes of local people and representatives
of the park authority whose priorities and objectives largely diverge. The results show that people settled adjacent to the
park are heavily dependent on its resources. Even in places where some, albeit few alternative sources exist, local people
continue to trespass the park boundary as these sources are inadequate to ensure the fulfillment of local people's resource
needs. Illegal transactions of resources continue throughout the year; however, they are less intense during summer due to
flooding caused by the Rapti River, which forms the park boundary towards the northern section where this study is conducted.
The frequency of local people's visits to the park is mainly determined by their age, distance between homesteads and park,
and volume of crop loss caused by wild animals. Crop damage is the function of size of landholding, distance, and frequency
of crop raid. Local people claim that they have no intention of letting their livestock graze in the park; however, the dense
vegetation of the park attracts livestock grazing on riverbanks just outside the open park boundary. Many head of livestock
are killed by carnivores of the park. Human casualties are mainly caused by sloth bear (Melursus ursinus), tiger (Panthera tigris), wild pig (Sug scrofa), and rhinoceros (Rhinoceros unicornis). There had been some earlier attempts to reconcile the conflicts by offering local people different kinds of compensations;
however, these were unsuccessful measures. An integrated approach is essential if efforts to resolve the park-people conflicts
are to succeed. The government is in the process of launching a project that aims to resolve the inherent problems with such
an approach. Suggestions are made to incorporate some key elements, such as maintaining effective communication between various
parties and the potential for wildlife conservation among local people. 相似文献
186.
Peter Weber 《Natural resources forum》1995,19(1):39-46
Research from the United Nations Food and Agriculture Organization and fishery scientists indicates that the wild catch of fish and other marine life from the oceans will not be able to increase significantly in the future, except through rehabilitation and better management of stocks. Despite the limited potential for bigger catches, fishing fleets have expanded rapidly in recent decades under government subsidies. Fishers now have approximately twice the capacity necessary to make the annual catch from the oceans. The juxtaposition of natural limits and overinvestment has created a crisis situation for the world's fishers, fishing communities, and traditional fishing cultures. Part I of this article (Natural Resources Forum, November 1994) discussed policy responses at the national and international level. How policy makers respond to the overextension of the marine fishing industry will determine the extent of job loss, hunger and dislocation that will result. Part II examines the social aspects of the world's fishing industry, including the demography of fishers, utilization of fisheries products, the relative social contribution of aquaculture and policy responses to overcapacity. Policy makers could enhance the social benefits of marine fisheries – both jobs and food – through a combination of government oversight and community-based management . 相似文献
187.
Christopher G. Uchrin Walter J. Weber 《Journal of the American Water Resources Association》1983,19(4):581-584
ABSTRACT A dynamic mathematical model was constructed to examine bacterial contamination problems affecting Ford Lake, a small recreational lake in Southeast Michigan. The model was calibrated and verified using summer dry weather averaged data and data from three wet weather surveys. Model simulations demonstrated that the major bacterial contamination was attributable to storm related perturbations affecting two point sources: the Huron River and the Ypsilanti Sewage Treatment Plant. The nonpoint source contribution was relatively minor. The Model is currently being used by the State of Michigan Department of Natural Resources as a management tool for assessing the effectiveness of planned pollution abatement strategies 相似文献
188.
Dewatering of wastewater sludge by heat treatment 总被引:1,自引:0,他引:1
J G Everett 《Journal - Water Pollution Control Federation》1972,44(1):92-100
189.
Maximilian Berthold Ulf Karsten Mario von Weber Alexander Bachor Rhena Schumann 《Ambio》2018,47(1):146-158
The EU-water framework directive aims at nutrient reductions, since anthropogenically induced eutrophication is a major threat for coastal waters. However, phytoplankton biomass in southern Baltic Sea coastal water bodies (CWB) remains high and the underlying mechanisms are not well understood. Therefore, a CWB data set was analysed regarding changes in phytoplankton biomass and nutrient concentration of nitrogen (N) and phosphorus (P) from 2000 to 2014. It was expected to find imbalances between produced phytoplankton biomass and total nutrient concentrations. Inner CWB were cyanobacteria-dominated and showed up to five times higher chlorophyll a-concentrations compared to outer CWB with similar total phosphorus-concentrations. Phytoplankton tended to be P-limited during spring and N-limited during summer. Phytoplankton biomass and nutrient concentrations were even higher during very humid years, which indicated a close coupling of the CWB with their catchment areas. This study suggests that re-mesotrophication efforts need to consider the importance of changed phytoplankton composition and nutrient availabilities. 相似文献
190.
Michael A. Lewis David E. Weber Larry R. Goodman Roman S. Stanley W. George Craven James M. Patrick Robert L. Quarles Thomas H. Roush John M. Macauley 《Environmental monitoring and assessment》2000,65(3):503-522
Periphyton colonization and sediment bioassessment were used ina survey to compare the relative environmental condition ofsampling sites located in Florida Bay and four peripheral sloughareas during the summer of 1995. Periphyton biomass, pigmentcontent, tissue quality and community composition weredetermined. In addition, benthic community composition and thetoxicities of whole sediments and associated pore waters weredetermined for two species of rooted macrophytes, an epibenthicinvertebrate and bioluminescent bacteria. Several locational differences were observed for the response parameters.Periphyton biomass was significantly greater in the Taylor Riverand the least in Shell Creek (P < 0.05). Most sediments were notacutely toxic to mysid shrimp nor phytotoxic. However, sedimentsfrom the Taylor River were more phytostimulatory than others (P< 0.05). Contaminant bioresidues were similar at most sites,however, mercury, chromium and nickel concentrations weregreater for periphyton colonized in the Taylor River and TroutCreek areas. Structural characteristics of the periphytic algalcommunity usually were statistically similar but a consistenttrend of lower density and diversity was evident for ShellCreek. The benthic community was the least diverse and dense inthe Canal C-111. The results of this study provide an initialindication of differences in the role of several slough areas aspossible sources of bioavailable contaminants to Florida Baywhich warrants additional investigation. 相似文献