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排序方式: 共有543条查询结果,搜索用时 31 毫秒
131.
Manon Gijtenbeek Monique C. Haak Tom J. P. Huberts Johanna M. Middeldorp Frans J. C. M. Klumper Femke Slaghekke Enrico Lopriore Dick Oepkes Jeanine M. M. van Klink 《黑龙江环境通报》2020,40(7):825-830
Objective
To investigate whether perioperative fetal hemodynamic changes in twin-to-twin transfusion syndrome (TTTS) are associated with neurodevelopmental impairment (NDI) at two years.Methods
Doppler parameters of three sonograms (day before, first day after and 1 week after laser surgery for TTTS) were assessed for correlation with neurodevelopmental outcome at two years (2008-2016). NDI was defined as: cerebral palsy, deafness, blindness, and/or a Bayley-III cognitive/motor developmental test-score > 2SD below the mean.Results
Long-term outcome was assessed in 492 TTTS survivors. NDI was present in 5% (24/492). After adjustment for severe cerebral injury (present in 4%), associated with NDI were: middle cerebral artery peak systolic velocity (MCA-PSV) >1.5 multiples of the median (MoM) 1 day after surgery (odds ratio [OR] 4.96; 95% confidence interval [CI]: 1.17-21.05, P = .03), a change from normal umbilical artery pulsatility index (UA-PI) presurgery to UA-PI >p95 postsurgery (OR 4.19; 95% CI: 1.04-16.87, P = .04), a change from normal to MCA-PSV >1.5MoM (OR 4.75; 95% CI: 1.43-15.77, P = .01).Conclusion
Perioperative fetal hemodynamic changes in TTTS pregnancies treated with laser are associated with poor neurodevelopmental outcome. Prospective research on the cerebrovascular response to altered hemodynamic conditions is necessary to further understand the cerebral autoregulatory capacity of the fetus in relation to neurodevelopmental outcome. 相似文献132.
Peter J. Taylor Glen R. Walker Geoff Hodgson Thomas J. Hatton Ray L. Correll 《Environmental management》1996,20(4):553-564
Irrigated agriculture has resulted in substantial changes in water flows to the lower reaches of the River Murray. These changes have led to large-scale occurrences of dieback inEucalyptus largiflorens (black box) woodlands as well as increased inputs of salt to the river. Management options to address problems of this scale call for the use of spatial data sets via geographic information systems (GIS). A GIS exists for one floodplain of the River Murray at Chowilla, and a simple model predicted six health classes ofEucalyptus largiflorens based on groundwater salinity, flooding frequency, and groundwater depth.To determine the usefulness of the model for vegetation management, the quality of both the model and the GIS data sets were tested. Success of the testing procedure was judged by the degree of spatial matching between the model's predictions of health and that assessed from aerial photographs and by field truthing. Analyses at 80 sites showed that tree health was significantly greater where groundwater salinity was less than 40 dS/m or flooding occurred more frequently than 1 in 10 years or depth to groundwater exceeded 4 m. Testing of the GIS data sets found that vegetation was misclassified at 15% of sites. Association was shown between GIS-predicted values and field-truthed values of groundwater salinity but not groundwater depth. The GIS model of health is a useful starting point for future vegetation management and can be further improved by increasing the quality of the data coverages and further refining of the model to optimize parameters and thresholds. 相似文献
133.
134.
Gaseous emissions from animal manure storage facilities can contribute to global greenhouse gas inventories. Biogas fluxes were measured for one year from a 2-ha anaerobic lagoon that received waste from a 10500-head swine (Sus scrofa) finishing operation in southwestern Kansas. During 2001, ebullition of biogas was measured continuously by using floating platforms equipped with gas-collection domes. Periodically, the composition of the biogas was determined by using gas chromatography. Detailed records of feed quality and quantity and animal weights and gains also were obtained to determine the carbon budget of the facility (barns and lagoon). Flux of biogas was very seasonal, with peak emission (18.7 mol m(-2) d(-1)) occurring in early June. Nearly 50% of the annual biogas losses occurred during a 30-d period beginning on day of year (DOY) 146. Flux patterns suggest that the start of the high biogas production period was governed by temperature, while the decline in production in mid-June was caused by substrate limitations. Average biogas composition was 0.71 L CH4 L(-1). The quantity of CH4 released from the lagoon was 86.3 Mg yr(-1), which represents about 38 g of CH4 per kg of animal weight gain. The average flux density of biogas from the lagoon was 382 mol m(-2) yr(-1) or 728 mol yr(-1) per resident animal where the resident animal population was 10500. Flux rates of CH4 were 1.7 to 3.4 times less than predictions made with Intergovernmental Panel on Climate Change (IPCC) models. Additional research is needed on the carbon budgets of other animal feeding operations so that better estimates of greenhouse gas emissions can be determined. 相似文献
135.
Habitat restoration at a landscape scale is becoming increasingly important in environmental management. In this context, geographical information systems are well suited as they can store and integrate many of the abiotic and biotic criteria used to assess the ecological worth of a site. However, this capacity can be limited by the availability or suitability of spatial data sets. A classic example of the latter case is the National Soil Map of England and Wales, which groups soils of a varied nature into associations. Consequently the national soil map has proved to be a poor predictor of habitat suitability. Using polytomous logistic regression we put forward a method for separating soil associations into their constituent soils within the Chilterns Natural Area. This approach used soil association, aspect, slope and relative height as variables for this analysis. Whilst the model's performance is likely to have been limited by the accuracy of the soil association data set, a predictive accuracy of between 47 and 65% is sufficient to facilitate better targeting of habitat restoration when combined with other abiotic factors such as climate and topography. 相似文献
136.
Tom Entwistle 《Local Environment》1998,3(1):55-65
On the face of it, the 1990s have marked the transformation of the UK's waste management policy. A commitment to waste minimisation and recycling, within the terms of the internationally accepted waste hierarchy, have replaced an almost complacent defence of landfill. However, aside from the dramatic transformation of the vocabulary, the reality of local authority waste disposal has, with a few notable exceptions, been characterised more by continuity than revolution. This article suggests that the modesty of local authority recycling is best explained through an appreciation of what can be described as recycling practice. Recycling in the UK has taken a distinctive form comprising: environmentalism, entrepreneurialism and policy advocacy. The components of this practice explain both the successes and failures of local authority recycling. Despite its oppositional roots, the Conservative Government found 'recycling practice' conducive to their reliance upon a mix of aspirational targets and market-based instruments (MBIs). Advice circulated as guidance to local authorities emphasised viability as the principal criterion of scheme assessment and in such a way sustained the limited scale and ambitions of recycling practice. 相似文献
137.
Tom Van Remmen 《Waste management (New York, N.Y.)》1998,18(6-8)
After many years of research and debate, in August of 1997 the United States Environmental Protection Agency (EPA) issued New Source Performance Standards (NSPS) and Emission Guidelines (EG) for medical/infectious waste incinerators in the United States. These new emissions and operational standards establish considerably more restrictive limitations on air emissions for medical/infectious waste incinerators and will undoubtedly have a significant impact on the over 2300 hospitals presently operating an incinerator on-site. This paper will explore the options available to these facilities, and those facilities which may be considering installation of an incinerator, relative to achieving compliance with the NSPS and EG for medical/infectious waste incinerators. 相似文献
138.
Dedecker AP Goethals PL D'heygere T Gevrey M Lek S De Pauw N 《Environmental monitoring and assessment》2005,111(1-3):223-241
This study aimed at analysing the relationship between river characteristics and abundance of Gammarus pulex. To this end, four methods which can identify the relative contribution and/or the contribution profile of the input variables
in neural networks describing the habitat preferences of this species were compared: (i) the ‘PaD‘ (‘Partial Derivatives‘)
method consists of a calculation of the partial derivatives of the output in relation to the input variables; (ii) the ‘Weights‘method
is a computation using the connection weights of the backpropagation Artificial Neural Networks; (iii) the ‘Perturb‘method
analyses the effect of a perturbation of the input variables on the output variable; (iv) the ‘Profile‘ method is a successive
variation of one input variable while the others are kept constant at a fixed set of values. The dataset consisted of 179
samples, collected over a three-year period in the Zwalm river basin in Flanders, Belgium. Twenty-four environmental variables
as well as the log-transformed abundance of Gammarus pulex were used in this study. The different contribution methods gave similar results concerning the order of importance of the
input variables. Moreover, the stability of the methods was confirmed by gradually removing variables. Only in a limited number
of cases a shift in the relative importance of the remaining input variables could be observed. Nevertheless, differences
in sensitivity and stability of the methods were detected, probably as a result of the different calculation procedures. In
this respect, the ‘PaD‘method made a more severe discrimination between minor and major contributing environmental variables
in comparison to the ‘Weights‘, ‘Profile‘ and ‘Perturb‘ methods. From an ecological point of view, the input variables ‘Ammonium‘
and to a smaller extent ‘COD‘, were selected by these methods as dominant river characteristics for the prediction of the
abundance of Gammarus pulex in this study area. 相似文献
139.
Ludmila Wilhelmová Milan Tomášek Karel Štukheil 《Environmental monitoring and assessment》1995,34(2):145-149
The results of measurements of Krypton-85 (85Kr) concentrations in the ground-level air of Prague between 1983 and 1992 are presented and time-related changes analysed. The long-term trend in activity level of 85Kr has been steadily increasing with a growth rate of 0.04 Bq.m–3 (STP) per year. Some peaks of 85Kr activity were observed due to the influence of undispersed radioactive plumes coming from distant sources. Short-term variations within a typical range of concentrations from 0.61 to 1.25 Bq.m–3 (STP) were found to be seasonally dependent, with the maximum occurring in spring. 相似文献
140.
Thomas C Pagano David C Garen Tom R Perkins Phillip A Pasteris 《Journal of the American Water Resources Association》2009,45(3):767-778
Abstract: Official seasonal water supply outlooks for the western United States are typically produced once per month from January through June. The Natural Resources Conservation Service has developed a new outlook product that allows the automated production and delivery of this type of forecast year‐round and with a daily update frequency. Daily snow water equivalent and water year‐to‐date precipitation data from multiple SNOTEL stations are combined using a statistical forecasting technique (“Z‐Score Regression”) to predict seasonal streamflow volume. The skill of these forecasts vs. lead‐time is comparable to the official published outlooks. The new product matches the intra‐monthly trends in the official forecasts until the target period is partly in the past, when the official forecasts begin to use information about observed streamflows to date. Geographically, the patterns of skill also match the official outlooks, with highest skill in Idaho and southern Colorado and lowest skill in the Colorado Front Range, eastern New Mexico, and eastern Montana. The direct and frequent delivery of objective guidance to users is a significant new development in the operational hydrologic seasonal forecasting community. 相似文献