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241.
242.
In both humans and mice the number of hair cells in the inner ear sensory epithelia declines with age, indicating cell death
(Park et al. 1987; Rosenhall 1973). However, recent reports demonstrate the ability of the vestibular sensory epithelia to
regenerate after injury (Forge et al. 1993, 1998; Kuntz and Oesterle 1998; Li and Forge 1997; Rubel et al. 1995; Tanyeri et
al. 1995). Still, a continuous hair cell turnover in the vestibular epithelia has not previously been demonstrated in mature
mammals. Bats are the only flying mammals, and they are known to live to a higher age than animals of equal size. The maximum
age of many species is 20 years, with average lifespans of 4–6 years (Schober and Grimmberger 1989). Further, the young are
fully developed and able to fly at the age of 2 months, and thus the vestibular organs are thought to be differentiated at
that age. Consequently, long-lived mammals such as bats might compensate for the loss of hair cells by producing new hair
cells in their postembryonic life. Here we show that the utricular macula of adult Daubenton's bats (more than 6 months old)
contains innervated immature hair cells as well as apoptotic hair cells, which strongly indicates a continuous turnover of
hair cells, as previously demonstrated in birds.
Received: 30 August 1999 / Accepted in revised form: 20 October 1999 相似文献
243.
244.
Bartonova A Clench-Aas J Gram F Grønskei KE Guerreiro C Larssen S Tønnesen DA Walker SE 《Journal of environmental monitoring : JEM》1999,1(4):337-340
In Oslo, traffic has been one of the dominating sources of air pollution in the last decade. In one part of the city where most traffic collects, two tunnels were built. A series of before and after studies was carried out in connection with the tunnels in use. Dispersion models were used as a basis for estimating exposure to nitrogen dioxide and particulate matter in two fractions. Exposure estimates were based on the results of the dispersion model providing estimates of outdoor pollutant concentrations on an hourly basis. The estimates represent concentrations in receptor points and in a square kilometre grid. The estimates were used to assess development of air pollution load in the area, compliance with air quality guidelines, and to provide a basis for quantifying exposure-effect relationships in epidemiological studies. After both tunnels were taken in use, the pollution levels in the study area were lower than when the traffic was on the surface (a drop from 50 to 40 micrograms m-3). Compliance with air quality guidelines and other prescribed values has improved, even if high exposures still exist. The most important residential areas are now much less exposed, while areas around tunnel openings can be in periods exposed to high pollutant concentrations. The daily pattern of exposure shows smaller differences between peak and minimum concentrations than prior to the traffic changes. Exposures at home (in the investigation area) were reduced most, while exposures in other locations than at home showed only a small decrease. Highest hourly exposures are encountered in traffic. 相似文献
245.
The Capital Region of Denmark tested the Multi Increment Sampling® (MIS) technology at 14 children's playgrounds in the region to assess whether the method provides representative test results and an improved foundation for risk assessment. The purpose of the investigation was to determine whether the previous uses of the playground areas have led to soil contamination that poses a health risk to its current users (children). The unpaved areas of the playgrounds were divided into decision units based on historical data along with the expected patterns of movement from its users. The samples from each unit consisted of 45 to 100 increments were collected from three depths within the upper one‐half meter. Furthermore, triplicate samples were taken from the upper sampling depth in at least one unit for quality control purposes. The investigation results showed excellent consistency between the pollution parameters and contamination levels in different decision units for each playground. The decision units where high levels of soil contamination exist coincide well with the previous site history. The MIS method has proven to be expensive and time consuming. However, in the future it will be easier to implement as we gain more experience with use of this method. ©2016 Wiley Periodicals, Inc. 相似文献
246.
Chhatra Mani Sharma Bjørn Olav Rosseland Marit Almvik Ole Martin Eklo 《Environmental pollution (Barking, Essex : 1987)》2009,157(8-9):2452-2458
Organochlorine pollutants in the major fish species (pike Esox lucius, perch Perca fluviatilis, and roach Rutilus rutilus) of Lake Årungen, Norway, were investigated after an extensive removal of large pike in 2004. The organochlorine pollutants detected in fish liver samples in 2005 were dichlorodiphenyltrichloroethane (DDTs), polychlorinated biphenyls (PCBs), hexachlorobenzene (HCB), and heptachlor epoxide (HCE). DDTs were the dominant among all analyzed OCs. ΣPCB and HCB, detected in fish from two clearly distinct trophic levels (prey and predators), give an indication of biomagnification. All OC concentrations in female pike were significantly lower compared to males, which might be due to the removal of high concentrations of pollutants in roe during spawning. 相似文献
247.
A.W. Larsen H. Merrild J. Møller T.H. Christensen 《Waste management (New York, N.Y.)》2010,30(5):744-754
Recycling of paper and glass from household waste is an integrated part of waste management in Denmark, however, increased recycling is a legislative target. The questions are: how much more can the recycling rate be increased through improvements of collection schemes when organisational and technical limitations are respected, and what will the environmental and economic consequences be? This was investigated in a case study of a municipal waste management system. Five scenarios with alternative collection systems for recyclables (paper, glass, metal and plastic packaging) were assessed by means of a life cycle assessment and an assessment of the municipality’s costs. Kerbside collection would provide the highest recycling rate, 31% compared to 25% in the baseline scenario, but bring schemes with drop-off containers would also be a reasonable solution. Collection of recyclables at recycling centres was not recommendable because the recycling rate would decrease to 20%. In general, the results showed that enhancing recycling and avoiding incineration was recommendable because the environmental performance was improved in several impact categories. The municipal costs for collection and treatment of waste were reduced with increasing recycling, mainly because the high cost for incineration was avoided. However, solutions for mitigation of air pollution caused by increased collection and transport should be sought. 相似文献
248.
249.
Gilbert C. S. Lui W. K. Li Anders Bjørgesæter Kenneth M. Y. Leung 《Environmental science and pollution research international》2014,21(1):177-192
This paper describes a novel statistical approach to derive ecologically relevant sediment quality guidelines (SQGs) from field data using a nonparametric empirical Bayesian method (NEBM). We made use of the Norwegian Oil Industrial Association database and extracted concurrently obtained data on species density and contaminant levels in sediment samples collected between 1996 and 2001. In brief, effect concentrations (ECs) of each installation (i.e., oil platform) at a given reduction in species density were firstly derived by fitting a logistic-type regression function to the relationship between the species density and the corresponding concentration of a chemical of concern. The estimated ECs were further improved by the NEBM which incorporated information from other installations. The distribution of these improved ECs from all installations was determined nonparametrically by the kernel method, and then used to determine the hazardous concentration (HC) which can be directly linked to the species loss (or the species being protected) in the sediment. This method also enables an accurate estimation of the lower confidence limit of the HC, even when the number of observations was small. To illustrate the effectiveness of this novel technique, barium, cadmium, chromium, copper, mercury, lead, tetrahydrocannabinol, and zinc were chosen as example contaminants. This novel approach can generate ecologically sound SQGs for environmental risk assessment and cost-effectiveness analysis in sediment remediation or mud disposal projects, since sediment quality is closely linked to species density. 相似文献