首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   590篇
  免费   13篇
  国内免费   7篇
安全科学   16篇
废物处理   39篇
环保管理   43篇
综合类   65篇
基础理论   161篇
污染及防治   186篇
评价与监测   54篇
社会与环境   44篇
灾害及防治   2篇
  2023年   8篇
  2022年   20篇
  2021年   15篇
  2020年   8篇
  2019年   12篇
  2018年   28篇
  2017年   26篇
  2016年   36篇
  2015年   14篇
  2014年   32篇
  2013年   49篇
  2012年   43篇
  2011年   55篇
  2010年   34篇
  2009年   38篇
  2008年   29篇
  2007年   36篇
  2006年   24篇
  2005年   26篇
  2004年   17篇
  2003年   16篇
  2002年   5篇
  2001年   8篇
  2000年   9篇
  1999年   3篇
  1997年   3篇
  1996年   3篇
  1993年   3篇
  1992年   1篇
  1991年   3篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1986年   1篇
  1972年   1篇
排序方式: 共有610条查询结果,搜索用时 46 毫秒
521.
Purpose. To investigate the point prevalence of upper back pain and lower back pain in Jordanian schoolteachers and to estimate the work-related reported disability. Method. A cross-sectional survey was used to assess back pain in a convenience sample of teachers in Jordan. Crude and weighted prevalence estimates of self-reported spinal pain and limited productivity were described. Demographic and occupational factors associated with self-reported pain and limited productivity were identified by multinomial/logistic regression. Results. Crude rates differed by gender, geographic location, school funding and grade levels of teaching. Weighted estimates for self-reported pain were 46% for females and 36% for males. Pain with limitation was 55% for males and 49% for females. Pain without limitation was associated with female gender (odds ratio [OR]?=?5.26). Pain with limitations was associated with female gender (OR?=?2.92), teaching in public school (OR?=?2.06) and body mass index (OR?=?1.1). Among subjects with pain, limitations were associated with male gender (OR?=?2.34), teaching in public school (OR?=?3.18) and pain in both upper and lower back (OR?=?4.64). Conclusions. Pain and occupational limitations are highly prevalent in schoolteachers in Jordan.  相似文献   
522.
Chitosan films (CF) [1 and 2% w/v] alone and with cinnamaldehyde (CNE) [0.25, 0.5 and 1% v/v] were prepared using an emulsion method, and the obtained films were characterized in terms of water vapor permeability (WVP), water solubility and optical, mechanical and antioxidant properties. The incorporation of CNE at 1% (v/v) significantly decreased the water solubility of the film by approximately 4% for the 1 and 2% CF films, whereas the WVP increased (2.5–3.5 times). The incorporation of CNE (0.25 and 0.5%) into 2% CF significantly increased the tensile strength (TS) (62 and 34%, respectively) and the percent elongation (%E) values, 26, 30 and 52% for CF that contained 0.25, 0.5 and 1% CNE, respectively. The largest value of the elasticity modulus (EM) was observed for 2% CF with 0.25% CNE. All films exhibited a yellow appearance (b*), but the CNE content had a marked impact on the coloration of the films. The CNE recoveries of the CF films (1 and 2%) with 1% of CNE were high (43 and 67%). The antioxidant activities indicated that the incorporation of 1% CNE into CF films (1 and 2%) increased the antioxidant activity. The protective effects of the films with and without CNE on erythrocytes were very strong (36–72% hemolysis inhibition). These results suggest there are potential applications for CF-CNE films as active packaging for the preservation of food products.  相似文献   
523.
This study evaluates the effects of the triazine herbicide simazine in an outdoor pond microcosm test system that contained two submerged rooted species (Myriophyllum spicatum and Elodea canadensis) and two emergent rooted species (Persicaria amphibia and Glyceria maxima) over a period of 84 days. Simazine was applied to the microcosms at nominal concentrations of 0.05, 0.5 and 5 mg/L. General biological endpoints and physiological endpoints were used to evaluate herbicide toxicity on macrophytes and the algae developing naturally in the system.Concentration-related responses of macrophytes and algae were obtained for the endpoints selected, resulting in a no observed ecologically adverse effect concentration (NOEAEC) at simazine concentrations of 0.05 mg active ingredient/L after 84 days. E. canadensis was the most negatively affected species based on length increase, which was consistently a very sensitive parameter for all macrophytes. The experimental design presented might constitute a suitable alternative to conventional laboratory single-species testing.  相似文献   
524.
To evaluate the spatial variability of ozone concentrations, two studies were undertaken in the montane environment of Trentino region, northern Italy, in 2007. In the first study, a 225 km2 area was considered. Here, a randomized design was used to evaluate the variability of ozone concentration at 1 and 225 km2 scale. Measurements were carried out by passive samplers between May and June 2007. In a second study, the whole 6207 km2 area of Trentino was considered. The area is covered by five grid cells of the European Monitoring and Evaluation Programme (EMEP). A systematic 15 × 15 km grid was used to allocate 15 passive samplers over the entire province, resulting into 1–4 samplers for each of the 5 EMEP grid cells (2500 km2 each) overlapping the study area. Measurements were carried out between June and September 2007. Accuracy of passive samplers was checked by direct comparison with conventional ozone analysers. Significant differences (P = 0.034) were found in ozone concentration among 1 × 1 km quadrates within the 225 km2 study area, while variability within the 1 × 1 km grid cells (coefficient of variation, CV′ = 0.12) slightly exceed the measurement error (CV′ = 0.08). At larger scales (225, 2500 and 6207 km2), ozone concentration shows much higher variability (CV′ from 0.18 to 0.28, with peak values at 0.40). Reported differences lead to very different AOT40 estimates even within the same EMEP grid cell. These findings suggest that 1 × 1 km resolution seems appropriate for ozone concentration modelling. On the other hand, significant sub-grid variation may exist at the resolution adopted by the EMEP model. Coupled with the likely variability of other important meteorological, soil and vegetation variables, our findings suggest that ozone risk assessment for vegetation based on large-scale modelled AOT40 and flux needs to be considered with great caution. The evidence reported in this paper asks for more detailed national-scale modelling, and the development of methods to incorporate local scale variations into large-scale models.  相似文献   
525.
The main purpose of this work was the preliminary qualitative study of organic compounds in wastewaters of swine slaughterhouses. The samples were collected in a local abattoir and submitted to Liquid-Liquid Extraction (LLE) and Solid-phase Extraction (SPE) with XAD-4TM resin as stationary phase. The instrumental analysis was performed by Gas Chromatography with Mass Spectrometer Detector (GC/MSD). The compounds present in the LLE and SPE extracts were identified by the GC/MSD library (Wiley). The results pointed out that SPE and LLE can extract practically the same classes of compounds at the same amounts. LLE works well for the extraction of polar organic compounds, with acidified samples, while SPE presents a better performance for the extraction of less polar organic compounds. Aldehydes were main class of the compounds extracted by SPE and LLE and decenal was the major aldehyde identified. Fatty alcohols and carboxylic acids were also identified but in minor proportions.  相似文献   
526.
This study was undertaken to evaluate the degradation and mobility of the herbicide tebuthiuron (N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N'-dimethylurea) in soil under field conditions, and its potential for leaching and groundwater contamination. A watershed, Espraiado, located over a recharge area in Brazil, was chosen for soil and water studies. At Espraiado, water samples were collected from seven wells at intervals of three months from March 2004 to June 2006 and analyzed for tebuthiuron. Other samples were taken from city wells located outside of the recharge area. To assess the potential movement to the aquifer, tebuthiuron was also applied to trial plots at the recommended label rate of 1.0 kg/ha a.i. in May of 2004, with and without sugarcane coverage, on sandy soil. Soil samples were collected during the years of 2004 and 2005, at depths intervals of 20 cm from soil surface down to 120 cm and analyzed for tebuthiuron at zero, 3, 30, 60, 90, 120, 150, 180, 240, and 300 days after application. There was no clear effect of sugarcane coverage on the tebuthiuron degradation in soils, but it moved faster into the soil where there was no cover. After 180 days there were no measurable residues in the soil, and tebuthiuron was not found below 40 cm depth in any time. Tebuthiuron had a half-life of 20 days under those conditions. No tebuthiuron residue was found in ground water samples at any sampling time.  相似文献   
527.
Monitoring of forest condition and ozone (O3) at 83 sites in France, Italy, Luxenbourg, Spain and Switzerland resulted in a number of findings in relation to the knowledge of O3 exposure (concentration and cumulative AOT40), feasibility of the assessment of stomatal O3 flux and relationships between O3 and crown defoliation of beech and visible symptoms on native vegetation. However, the project provides evidence of issues to be addressed within the current monitoring system (data quality, validation sites and response indicators) and indications as to how the monitoring of O3 risk in the context of an effect-oriented monitoring program can be improved.  相似文献   
528.
Ozone and forests in South-Western Europe   总被引:1,自引:0,他引:1  
The paper provides basic information about background, objectives and structure of O3SWE (Ozone at the permanent monitoring plots in South-Western Europe), an international co-operative project aimed at evaluating O3 concentrations, cumulative exposure, uptake and effects on forest vegetation in four countries of South-Western Europe (France, Italy, Luxenbourg, Spain and Switzerland). The project covers a total of 83 permanent plots of the EU and UN/ECE intensive forest monitoring programme and span over three years of investigation (2000-2002). The O3SWE project aims to demonstrate how, using data collected routinely in an intensive forest monitoring network, O3 exposure, flux and effects can be assessed and exceedances critically evaluated.  相似文献   
529.
The benefits of flue gas recirculation in waste incineration   总被引:1,自引:0,他引:1  
Flue gas recirculation in the incinerator combustion chamber is an operative technique that offers substantial benefits in managing waste incineration. The advantages that can be obtained are both economic and environmental and are determined by the low flow rate of fumes actually emitted if compared to the flue gas released when recirculation is not conducted. Simulations of two incineration processes, with and without flue gas recirculation, have been carried out by using a commercial flowsheeting simulator. The results of the simulations demonstrate that, from an economic point of view, the proposed technique permits a greater level of energy recovery (up to +3%) and, at the same time, lower investment costs as far as the equipment and machinery constituting the air pollution control section of the plant are concerned. At equal treatment system efficiencies, the environmental benefits stem from the decrease in the emission of atmospheric pollutants. Throughout the paper reference is made to the EC legislation in the field of environmental protection, thus ensuring the general validity in the EU of the foundations laid and conclusions drawn henceforth. A numerical example concerning mercury emission quantifies the reported considerations and illustrates that flue gas recirculation reduces emission of this pollutant by 50%.  相似文献   
530.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号