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871.
Major cities in China and many other fast-growing economies are expanding their subway systems in order to address worsening air pollution and traffic congestion. This paper quantifies the impact of subway expansion on air quality by leveraging fine-scale air quality data and the rapid build-out of 14 new subway lines and 252 stations in Beijing from 2008 to 2016. Our main empirical framework examines how the density of the subway network affects air quality across different locations in the city during this period. To address the potential endogenous location of subway stations, we construct an instrument based on historical subway planning, long before air pollution and traffic congestion were of concern. Our analysis shows that an increase in subway density by one standard deviation improves air quality by two percent and the result is robust to a variety of alternative specifications including the distance-based difference-in-differences method. The total discounted health benefit during a 20-year period from reduced mortality and morbidity as a result of 14 new subway lines amounts to $1.0–3.1 billion, or only 1.4–4.4 percent of the total construction and operating cost. 相似文献
872.
Jutta Geldermann Robert Gabriel Otto Rentz 《Environmental science and pollution research international》1999,6(2):115-121
The burning of kerosene in jet turbines is investigated for two reference flights with a Boeing 747-400 and an Airbus A320-200,
representing the typical Lufthansa planes for long and middle distance. The ecological evaluation is performed by Life Cycle
Assessment (LCA). Formation of condensation trails, which is a specific environmental impact caused by air traffic, has to
be considered in addition to established LCA impact categories. Based on the ecological assessment, an improvement assessment
is performed. Environmental performance of diesel fuel during the combustion in car engines is analysed based on available
publications. The relevant parameters for the environmental impact of the combustion of diesel (aromatics content, reduction
of sulphur content, the reduction of the density and raising of the cetane number) are discussed with regard to improvements
of the exhaust qualities of kerosene. A reduction of the aromatics content promises to improve the emission of soot which
should be further investigated. 相似文献
873.
Tao Wang Liping Xiao Hongbin Lu Shaoyong Lu Jiaxin Li Xiaochun Guo Xiaoliang Zhao 《环境科学学报(英文版)》2022,34(1):249-262
A pilot-scale multistage constructed wetland-pond(MCWP) system with a "pre-ecological oxidation pond, two-stage horizontal subsurface flow constructed wetland(HSCW) and surface flow constructed wetland(SFCW) as the core and postsubmerged plant pond" as the process was used to treat actual polluted river water in the field, and the variation in nitrogen removal from summer to winter was investigated. The results showed that the average total nitrogen(TN) removal efficiency in the MCWP was approxi... 相似文献
874.
乌鲁木齐市大气污染限期治理对策探讨 总被引:1,自引:0,他引:1
以乌鲁木齐市大气污染问题日益严重的现状为主题,针对大气污染产生的原因,阐述做好大气污染综合治理工作的对策和环保部门如何在大气污染治理工作中发挥职能作用,以期使大气环境质量得到根本的改善。 相似文献
875.
876.
Levels and congener distributions of PCDDs,PCDFs and dioxin-like PCBs in environmental and human samples: a review 总被引:1,自引:0,他引:1
K. Srogi 《Environmental Chemistry Letters》2008,6(1):1-28
The term “dioxins” is often used in a confusing way. In toxicological considerations—and also in the present report—the term
is used to designate the PCDDs, the PCDFs and the coplanar (“dioxin-like”) PCBs, since these classes of compounds show the
same type of toxicity. Because of the large number of congeners, relevant individual congeners are assigned with a toxic equivalency
factor (TEF) that relate their toxicity to that of tetrachlorodibenzo-p-dioxin (TCDD) (2,3,7,8-TCDD) and are to be evaluated as dioxins. Each concentration of an individual congener in a mixture
is multiplied with its TEF, and the resulting TCDD equivalents are added up and expressed as WHO-endorsed toxic equivalents
(WHO-TEQ). Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are mainly the by-products of industrial processes (such as metallurgical
processing, bleaching of paper pulp, and the manufacturing of some herbicides and pesticides) but they can also result from
natural processes like volcanic eruptions and forest fires. Waste incineration, particularly if combustion is incomplete,
is among the largest contributors to the release of PCDDs and PCDFs into the environment. Due to their persistence, PCDDs,
PCDFs and PCBs are part of the so-called persistent organic pollutants group of compounds that also include some chlorinated
pesticides. Since they have a high lipophilicity and resist transformation, they bio-accumulate in animal and human adipose
tissues. Consumption of food is considered as the major source of non-occupational human exposure to PCDD/Fs with foodstuffs
from animal origin accounting for more than 90% of the human body burden. With meat, dairy, and fish products being the main
contributors. The aim of the present review was to summarize experimental data regarding dioxin emissions from contaminated
and uncontaminated biological and environmental samples, from the available literature. The information will be presented
chronologically with respect to distribution in human milk, serum; food, water, air, soils and sediments. 相似文献
877.
W. Bowman Cutter Matthew Neidell 《Journal of Environmental Economics and Management》2009,58(3):253-265
This paper assesses whether individuals change their transportation choices in response to ‘Spare the Air’ (STA) advisories, a public voluntary information program in the San Francisco Bay Area that elicits reductions in ozone-producing activities. Since STAs are issued when ozone levels are predicted to exceed a particular threshold, we use a regression discontinuity design to identify the effect of STAs. We also use traffic conditions in Southern California, an area without STAs, to estimate difference-in-differences models. The results suggest that STAs reduce traffic volume and slightly increase the use of public transit, supporting a potential role for voluntary information programs that directly target individuals as a means for improving local air quality. 相似文献
878.
ebnem Andreani-Aksoyolu Johannes Keller Carlos Ordez Michel Tinguely Martin Schultz Andr S.H. Prvt 《Ecological modelling》2009,217(3-4):209
In this study, we investigated the effect of numerous regulations enforced since 1985 to improve air quality on ozone in Europe with the focus on Switzerland, using the Comprehensive Air Quality Model with Extensions (CAMx) for a specific summer period. Several emission scenarios for the year 2010 were also considered. The model results suggest that the emission reductions of ozone precursors should have been effective to reduce ozone production between 1985 and 2000 in northern Switzerland. However, observations do not indicate any significant change in surface ozone levels since early 1990s, except in the region of Zurich where there is a small negative trend. On the other hand, the model predictions match very well the spatial variability of the trends but the calculated trends are around 0.5 ppb year−1 lower than those observed. This difference is similar to the background ozone increase as suggested by the long-term observations at the high Alpine station Jungfraujoch. These results support the hypothesis that the decrease in local ozone production due to emission reductions might have been partly or completely compensated by the simultaneous increase in the background ozone. In 2010, a strict application of the Gothenburg Protocol in Europe would lead to a decrease in peak ozone concentrations by about 5% in Switzerland under the meteorological conditions applied. Our calculations also indicated that emission controls only in Switzerland would not be very effective to improve the air quality in the future. The further development of the background ozone will in any case be very important for the tropospheric ozone levels. 相似文献
879.
H. Chanson 《Environmental Fluid Mechanics》2009,9(2):125-142
In hydraulic structures, free-surface aeration is commonly observed: i.e., the white waters. The air bubble entrainment may
be localised (hydraulic jumps, plunging jets) or continuous along an interface (water jets, chutes). Despite recent advances,
there are some basic concerns about the extrapolation of laboratory results to large size prototype structures. Herein the
basic air bubble entrainment processes are reviewed and the relevant dynamic similarities are discussed. Traditionally, physical
studies are conducted using a Froude similitude which implies drastically smaller laboratory Reynolds numbers than in the
corresponding prototype flows. Basic dimensional analyses are developed for both singular and interfacial aeration processes.
The results are discussed in the light of systematic investigations and they show that the notion of scale effects is closely
linked with the selection of relevant characteristic air–water flow properties. Recent studies of local air–water flow properties
highlight that turbulence levels, entrained bubble sizes and interfacial areas are improperly scaled based upon a Froude similitude
even in large-size models operating with the so defined Reynolds numbers ρ
w × q
w/μ
w up to 5 E+5. In laboratory models, the dimensionless turbulence levels, air–water interfacial areas and mass transfer rates
are drastically underestimated. 相似文献
880.
Etienne Roth 《毒物与环境化学》2013,95(4):313-330
Specific usage of neutron activation analysis, charged particle analysis, y photons analysis, G.C.M.S. coupling, stable isotope dilution techniques, are discussed. Dust collected on filters, oxygenated compounds in exhaust gases from car engines, nitrogen oxides, have thus been determined. Special calibration methods for ozone, and remote detection by Lidar Raman are also described. 相似文献