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   112篇
  免费   4篇
  国内免费   3篇
安全科学   4篇
废物处理   4篇
环保管理   11篇
综合类   18篇
基础理论   33篇
污染及防治   28篇
评价与监测   12篇
社会与环境   8篇
灾害及防治   1篇
  2023年   2篇
  2022年   3篇
  2021年   8篇
  2020年   4篇
  2019年   6篇
  2018年   12篇
  2017年   7篇
  2016年   13篇
  2015年   2篇
  2014年   12篇
  2013年   9篇
  2012年   6篇
  2011年   10篇
  2010年   5篇
  2009年   6篇
  2008年   5篇
  2007年   1篇
  2006年   2篇
  2005年   1篇
  2003年   1篇
  2001年   2篇
  1995年   1篇
  1990年   1篇
排序方式: 共有119条查询结果,搜索用时 15 毫秒
1.
Wastewater treatment center(WTC) workers may be vulnerable to diseases caused by viruses, such as the common cold, influenza and gastro-intestinal infections. Although there is a substantial body of literature characterizing the microbial community found in wastewater, only a few studies have characterized the viral component of WTC aerosols,despite the fact that most diseases affecting WTC workers are of viral origin and that some of these viruses are transmitted through the air. In this study, we evaluated in four WTCs the presence of 11 viral pathogens of particular concern in this milieu and used a metagenomic approach to characterize the total viral community in the air of one of those WTCs. The presence of viruses in aerosols in different locations of individual WTCs was evaluated and the results obtained with four commonly used air samplers were compared.We detected four of the eleven viruses tested, including human adenovirus(h Ad V),rotavirus, hepatitis A virus(HAV) and Herpes Simplex virus type 1(HSV1). The results of the metagenomic assay uncovered very few viral RNA sequences in WTC aerosols, however sequences from human DNA viruses were in much greater relative abundance.  相似文献   
2.
We have applied our multimarker approach of maternal serum alpha-fetoprotein (AFP) and free-beta human chorionic gonadotropin (hCG) for Down syndrome screening to multiple gestations to assess its efficacy for improved detection of twin and triplet pregnancies. This study matched 225 cases of twin pregnancy and 39 cases of triplet pregnancy each with ten singleton pregnancies based on gestational week, race, time to receive sample, time of year of sample, and geographical area. The ratios of the MOM for each group at the tenth, 50th, and 90th percentiles were compared by the Wilcoxon test. Risks for twins were calculated using Bayes' rule, the age-related incidence of twins, and the levels of AFP and free-beta hCG. The tenth, 50th, and 90th percentiles of free-beta hCG MOMs in twin and triplet cases were 0.85, 1.99, and 4.51, and 1.38, 2.78, and 4.07, respectively. For AFP, the MOMs at these percentiles were 1.26, 1.91, and 2.99, and 2.02, 2.68, and 5.30, respectively. The twin and triplet distributions for each marker were statistically significantly different from the singleton distributions (P<0.0001) and from each other (P=0.0012). At a twin risk cut-off of 1 in 50, 77.4 per cent of all twin gestations can be detected in a second-trimester AFP and free-beta hCG screening protocol with 5.1 per cent of singleton pregnancies falsely identified as at risk for twins. Our dual marker protocol for mid-trimester pregnancy screening combining AFP and free-beta hCG can identify over 77 per cent of twin pregnancies in women less than 35 years of age. This benefit may contribute to an improved outcome of pregnancy by early detection of multiple gestation.  相似文献   
3.
Environmental Science and Pollution Research - This work proposes a novel approach for the coupling of ozonation and Fenton processes using a new prototype of a high rotation bubble reactor (HRBR),...  相似文献   
4.

Natural products may be applied in a wide range of domains, from agriculture to food and pharmaceutical industries. In this study, the antioxidant properties and the capacity to inhibit some enzymatic activities of Euphorbia resinifera and Euphorbia officinarum aqueous extracts and honeys were assessed. The physicochemical characteristics were also evaluated. Higher amounts of iron, copper and aluminium were detected in E. officinarum honey, which may indicate environmental pollution around the beehives or inadequate storage of honey samples. This honey sample showed higher amounts of total phenols and better capacity for scavenging superoxide anion free radicals and DPPH free radicals as compared with E. resinifera honey, but poorer capacity for inhibiting lipoxygenase, acetylcholinesterase, tyrosinase and xanthine oxidase. The ratio plant mass:solvent volume (1:100) and extraction time (1 - 2 h) were associated with higher total phenols and better antioxidant activities and lipoxygenase, acetylcholinesterase and tyrosinase inhibitory activities, regardless of the plant species. The aqueous extracts had systematically higher in vitro activities than the respective honey samples.

  相似文献   
5.
6.
7.
This paper focuses on the diversity of engine technologies for low emission vehicles (LEVs) that are developed by car manufacturers in order to substitute for the conventional internal combustion engine vehicle (ICEV). Our purpose is to analyse the competition between the various technologies for LEVs as well as the innovative strategy of car manufacturers. We first propose to define and to represent these technological trajectories in order to compare their performances and to identify their strengths and weaknesses. The technological bottlenecks, the barriers to the adoption of these alternative engine technologies as well as the features of this technological competition are underlined. We then use a patent data analysis to study the patent portfolios of the main car manufacturers in these technologies over the period [1990–2005]. The dynamics of patent applications by car manufacturers gives insight on the competition among technologies and on the strategy of firms. This analysis emphasises the progressive diversification of firms' patent portfolios over the whole set of engine technologies and the differentiated strategic positioning of car manufacturers according to countries.  相似文献   
8.
9.
10.
Fetal magnetic resonance spectroscopy (MRS) is technically feasible in utero and demonstrates similar findings to those observed in neonatal populations. MRS can provide additional information to conventional T1- and T2-weighted imaging of the fetal brain. It is of particular use when subtle changes are present on conventional fetal MRI sequences, and when imaging fetuses at risk of brain injury and metabolic abnormalities. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
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