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971.
Eric L. Hyman David H. Moreau Bruce Stiftel 《Journal of the American Water Resources Association》1984,20(6):915-922
SAGE, a proposed method for environmental assessment, focuses on eliciting and incorporating value weights in multiple-objective decision making. In this method, the value weights are inferred from the tradeoffs that people make in choices about alternatives. These weights are applied to scaled scores for accounts based on measurable attributes of each objective. In order to indicate the political ramifications of decisions and to facilitate sensitivity analysis, the values held by various groups are presented in matrix from arrayed by group affiliation or by judgment types that share common values. Results of a trial application of SAGE to a land use/watershed management problem in a growing urban area are presented. 相似文献
972.
Eric L Hyman 《Resources Policy》1984,10(3):163-176
This article provides an overview of natural resource economics. It begins with a summary of historical and current views on resource scarcity. It then discusses economic models for optimal management of non-renewable and renewable resources at the micro and macro levels and evaluates their usefulness in planning, management and policy making. 相似文献
973.
The ever-increasing amount of electronic scrap and the steadily-decreasing contents of the precious metals used in electronics, as well as the ever-growing environmental awareness, challenges such conventional precious-metal-oriented recycling techniques as pyrometallurgy. Separation and beneficiation of various materials encountered in electronic scrap might provide a correct solution ahead. In this context, mechanical separation-oriented characterization of electronic scrap was conducted in an attempt to evaluate the amenability of mechanical separation processes. Liberation degrees of various metals from the non-metals, which are crucial for mechanical separation, were analyzed by means of a grain counting approach. It is found that the metallic particles below 2 mm achieve almost complete liberation. Particle shapes were also quantified through an image processing system. The results obtained show that the shapes of the particles, as a result of shredding, turn out to be heterogeneous, thereby complicating mechanical separation processes. In addition, separability of various materials was ascertained by a sink–float analysis. It has been shown that density-based separation techniques shall be viable in separating metals from plastics, light plastics (ABS, PS and PVC, etc.) from glass fiber reinforced resins and aluminum from heavy metals. Specifically, a high quality copper concentrate can be expected by density-based separation techniques. Moreover, FT-IR spectra of plastics pieces from the light fractions after the sink–float testing show that PC scrap primarily contains ABS, PS and PVC plastics with the density range of +1.0–1.5 g/cm3, whereas PCB scrap mainly contains glass fiber reinforced epoxy resins plastics with the density range of +1.5–2.0 g/cm3. 相似文献
974.
PROBLEM: Home-study driver education programs exist in several states, but none have been scientifically evaluated to determine if such courses are as effective as classroom courses for teaching driver education. METHOD: Over 1,300 students were randomly assigned to classroom instruction, or CD ROM, workbook, or Internet/workbook home-study courses and compared on proctored exit examination knowledge and attitude scores, and written knowledge test outcomes. RESULTS: Few differences were found on exit examination knowledge and attitude scores, but they tended to favor the CD and Internet/workbook home-study courses over the classroom or workbook courses. Differences favoring the classroom on written knowledge test outcomes likely reflect a bias in classroom courses toward teaching test-specific material. DISCUSSION: The findings present no compelling evidence that home-study courses are less effective than classroom courses for teaching driver education. IMPACT ON INDUSTRY: The findings could result in more widespread use of home-study courses. Also, the use of low-cost home-study courses as the first course of a two-stage driver education and training system could make integrating such programs with graduated driver licensing more feasible and acceptable to the public. 相似文献
975.
Water samples were collected between 1999 and 2000 from wetlands in Minnesota that contained malformed frogs. The water samples were analyzed for 14 minerals/ions and screened for the presence of biologically active compounds using Xenopus laevis. Results indicated that water from two sites, CWB and ROI2, induced severe retardation with embryo lengths reduced 20% after 96 hr of development. The developmental delay observed with water from ROI2 was alleviated by supplementation with sodium, while both sodium and potassium alleviated the developmental delay observed with water whose mineral content mimicked that of CWB. Seasonal fluctuations in the sodium and potassium content at ROI2 and NEY correlated with changes in the rates of Xenopus development. Xenopus embryos reared on water from ROI2 for 120 hr displayed gut malformations not present in embryos reared on a synthetic media designed to mimic the mineral content of the water from ROI2. Embryos reared on water from ROI2 supplemented with minerals at levels comparable to that routinely employed in the rearing of Xenopus were neither retarded nor malformed. It is proposed that climate driven hydrology may influence the mineral composition at selected wetlands and delay development which may alter window(s) of susceptibility towards biologically active agents and the occurrence of malformed frogs. 相似文献
976.
Extensive studies of the radiocarbon (14C) distribution and transfer in the marine environment of the North-Cotentin peninsula and along the English Channel have been carried out. The main aims of these studies have been to estimate the spatial and temporal variation of the 14C concentration in seawater and to calculate 14C concentration factors for some biological species. Such information will be helpful in order to calculate precisely radiation doses to humans. First results obtained in the vicinity of the COGEMA La Hague nuclear plant (Goury) indicate a 14C labelling of the dissolved inorganic carbon (DIC) in seawater (8.0-26.2 Bq.m(-3)) and a tight relationship between the 14C in the liquid releases from the plant and the 14C concentrations in DIC. The particulate organic carbon (POC) is also labelled. The concentration factor calculations for the brown algae (Fucus serratus) sampled from Goury, and also along the English Channel, give 14C values around 3000 Bq.kg(-1) fresh weight / Bq.L(-1). 相似文献
977.
Direct measurement of octanol-water partition coefficients of some environmentally relevant brominated diphenyl ether congeners 总被引:5,自引:0,他引:5
Octanol-water partition coefficients (K(OW)) of nine environmentally relevant brominated diphenyl ether (BDE) congeners present in two technical mixtures were directly measured using a slow-stir technique. LogK(OW) values of tri- to heptabrominated BDE congeners ranged from 5.74 to 8.27, and were related to bromine content by the equation logK(OW)=0.621(#Br)+4.12(R(2)=0.970). The directly determined K(OW) values were generally lower than those calculated using fragment constant methods, particularly at higher levels of bromine substitution. The quasi-experimental approach of using fragment constants to modify a "backbone" compound of known K(OW) was much more successful than using the fragment constants to "build" the entire molecule. The tri- and tetrabrominated congeners are in the range of optimum bioaccumulation potential. 相似文献
978.
This article looks at some of the barriers that have distorted the global flow of capital in the mining industry. The perceived threat of nationalization is discussed and Chile's expropriation of US copper mining companies in 1971 is examined. Political instability, leading not only expropriation but to loss of title, altered tax laws, and voided contracts, is also cited as a factor affecting investor confidence. Finally, inadequate infrastructure is regarded as a further barrier to development of Third World mineral industries. 相似文献
979.
Eric Grosjean Daniel Grosjean 《Atmospheric environment (Oxford, England : 1994)》1996,30(24):4107-4113
Carbonyl products have been identified and their formation yields measured in experiments involving the gas-phase reaction of ozone with the 1-alkenes (RCH = CH 2) 3-methyl-l-butene (R = i-propyl), 4-methyl-l-pentene (R = i-butyl), 3-methyl-l-pentene (R= s-butyl), 3,3-dimethyl-l-butene (R = t-butyl) and styrene (R = C6H5) at ambient T and p = 1 atm of air. Sufficient cyclohexane was added to scavenge OH in order to minimize reactions of OH with the alkenes and with their carbonyl products. Formation yields (carbonyl formed/ozone reacted) of primary carbonyls were close to the value of 1.0 that is consistent with the mechanism: O3 + RCH = CH2 → α(HCHO + RCHOO) + (1 - α) (H2COO + RCHO), where formaldehyde and RCHO are the primary carbonyls and H2COO and RCHOO are the biradicals. Measured sums of the primary carbonyl formation yields were 1.006 ± 0.053 (1 S.D.) for formaldehyde + methylpropanal from3-methyl-l-butene(α = 0.494 ± 0.049), 1.025 ± 0.017 for formaldehyde + 2-methylbutanal from 3-methyl-l-pentene (α = 0.384 ± 0.013),1.147 ± 0.050 for formaldehyde + 3-methylbutanal from 4-methyl-l-pentene (α = 0.384 ± 0.020), 0.986 ± 0.014 for formaldehyde + 2,2-dimethylpropanal from 3,3-dimethyl-l-butene (α = 0.320 ± 0.012) and 0.980 ± 0.086 for formaldehyde + benzaldehyde from styrene (α = 0.347 ± 0.059). Carbonyls other than the primary carbonyls were identified; formation pathways are proposed that involve subsequent reactions of the monosubstituted biradicals RCHOO. Similarities and differences between branched-chain 1-alkenes and n-alkyl-substituted 1-alkenes are discussed. 相似文献
980.
Biological Report 88(41):1–103), assessment of credits and determination of a compensation ratio that reflects existing and/or potential functional
condition in a mitigation bank has been a formidable task. This study presents a framework for a systematic approach for determination
of credits and debits and subsequently the compensation ratio. A model for riparian systems is developed based on this framework
that evaluates credits and debits for spatial and structural diversity, contiguity of habitats, invasive vegetation, hydrology,
topographic complexity, characteristics of flood-prone areas, and biogeochemical processes. The goal of developing this crediting
and debiting framework is to provide an alternative to the current methods of determining credits and debits in a mitigation
bank and assigning mitigation ratios, such as best professional judgement or use of preset ratios. The purpose of this crediting
and debiting framework is to develop a method that (1) can be tailored to evaluate ecological condition based on the target
resources of a specific mitigation bank, (2) is flexible enough to be used for evaluation of existing or potential ecologic
condition at a mitigation bank, (3) is a structured and systematic way to apply data and professional judgment to the decision-making
process, (4) has an ecologically defensible basis, (5) has ease of use such that the level of expertise and time required
to employ the method is not a deterrent to its application, and (6) provides a semiquantitative measure of the condition of
aquatic resources that can be translated to a mitigation ratio. 相似文献