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   248篇
  免费   2篇
  国内免费   1篇
安全科学   4篇
废物处理   21篇
环保管理   23篇
综合类   33篇
基础理论   42篇
环境理论   1篇
污染及防治   83篇
评价与监测   24篇
社会与环境   18篇
灾害及防治   2篇
  2023年   3篇
  2022年   8篇
  2021年   15篇
  2020年   8篇
  2019年   6篇
  2018年   11篇
  2017年   8篇
  2016年   12篇
  2015年   9篇
  2014年   23篇
  2013年   21篇
  2012年   10篇
  2011年   15篇
  2010年   11篇
  2009年   18篇
  2008年   10篇
  2007年   8篇
  2006年   4篇
  2005年   8篇
  2004年   6篇
  2003年   5篇
  2002年   7篇
  2001年   1篇
  2000年   5篇
  1999年   6篇
  1998年   1篇
  1997年   3篇
  1996年   2篇
  1995年   1篇
  1993年   1篇
  1990年   1篇
  1986年   1篇
  1984年   1篇
  1980年   1篇
  1975年   1篇
排序方式: 共有251条查询结果,搜索用时 15 毫秒
111.
Environmental Monitoring and Assessment - Due to the concern with the quality of hydric resources, the monitoring is essential to evaluate and identify the anthropogenic and environmental...  相似文献   
112.
The concentrations of rare earth elements (REE), measured in water samples from Atibaia River and its tributary Anhumas Creek, Brazil, present excess of dissolved gadolinium. Such anthropogenic anomalies of Gd in water, already described in other parts of the world, result from the use of stable and soluble Gd chelates as contrast agents in magnetic resonance imaging. Atibaia River constitutes the main water supply of Campinas Metropolitan area, and its basin receives wastewater effluents. The REE concentrations in water samples were determined in 0.22-μm pore size filtered samples, without and after preconcentration by solid-phase extraction with bis-(2-ethyl-hexyl)-phosphate. This preconcentration method was unable to retain the anthropogenic Gd quantitatively. The probable reason is that the Gd chelates dissociate slowly in acidic media to produce the free ion that is retained by the phosphate ester. Strong correlations between Gd and constituents or parameters associated with effluents confirmed the source of most Gd in water samples as anthropogenic. The shale-normalized REE patterns of Atibaia River and Anhumas Creek water samples showed light and heavy REE enrichment trends, respectively. Also, positive Ce anomalies in many Atibaia River samples, as well as the strong correlations of the REE (except Gd) with terrigenous elements, imply that inorganic colloidal particles contributed to the REE measured values.  相似文献   
113.
Jackfruit starch based biodegradable films containing lysozyme were characterized for their antimicrobial activity, thickness, solubility, water vapor permeability and mechanical properties. The biodegradable films had good appearance and antimicrobial activity against Micrococcus lysodeikticus. The thickness of the biodegradable films were not affected by the variation in pH, but the addition of lysozyme increased the thickness, the thickest films being those with the highest lysozyme concentrations. The variation in pH of the filmogenic solutions affected the solubility of the biodegradable films, water solubility being greatest at pH 7.0 and with the highest lysozyme concentration. The permeability of the biodegradable films was increased by incorporating lysozyme. The lysozyme concentration and pH variation caused changes in the mechanical properties. The addition of 8% lysozyme increased the tensile strength and Young’s modulus for all the pH values studied. With respect to the release of antimicrobial activity, the diffusion of lysozyme was shown to follow Fickian transport mechanism.  相似文献   
114.
Environmental effects of enlargement works in Puerto Calero (Lanzarote, Canary Islands) were analysed in the sediments using abiotic variables (total hydrocarbons, polyaromatic hydrocarbons, organic matter and granulometry) and three biotic indexes (AMBI, M-AMBI and BENTIX). A before–after/control–impact (BACI) design was developed with four sampling campaigns, before (November 2004), during (March and July 2005) and after (July 2006) works. Inner stations were characterised by high concentrations of pollutants (total hydrocarbons and polyaromatic hydrocarbons). A temporal trend (2004–2006) was observed in macrofaunal assemblage structure, and thus in AMBI, M-AMBI and BENTIX indexes. Macrobenthic assemblages also mirrored the pollution gradient, with bioindicator species in inner stations (the polychaete Pseudopolydora paucibranchiata and the mollusc Abra alba), sensitive species (the sipunculid Aspidosiphon muelleri, the crustacean Pariambus typicus and the polychaete Aponuphis bilineata) in outer stations and ubiquitous species (the polychaetes Aricidea assimilis and Armandia polyophthalma) in both stations (inner and outer).  相似文献   
115.
116.
The discovery of fetal DNA in maternal plasma from early pregnancies has led to new opportunities for clinical application. In the last few years there have been numerous reported applications, mainly fetal gender and RhD genotyping. The prenatal diagnosis of some inherited genetic diseases such as Huntington disease is also very frequently required in the prenatal diagnosis routine. We have successfully diagnosed, with a non-invasive procedure, an unaffected HD fetus at the 13th week of gestation using fetal DNA from maternal plasma and the quantitative fluorescent PCR method, which is one of the most sensitive ways to detect fetal DNA in maternal plasma at such an early time of gestation. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
117.
The fate of (14)C atrazine was investigated using microcosms and an undisturbed Red-Yellow Latossol (Oxisol) under simulated rainfall conditions of 200 mm water month(-1). Experiments were carried out using microcosm cores, the first with an uncovered surface soil; the second set with uncovered subsurface soil; the third with subsurface soil covered with 3 cm of cow manure and the last with subsurface soil covered with 5 cm of grass straw. Average values for the amount of atrazine leached after 60 days were as follows: surface soil 1.6%; subsurface 47.3%; subsurface plus manure 17.3% and subsurface plus straw 24.8%. In the surface soil, 53% of the (14)C atrazine remained within the upper 1 cm, while in the subsurface microcosms the atrazine was more evenly distributed. The authors report that surface soil was retained atrazine and its metabolites for 60 days. The addition of a straw or manure covering to exposed subsoil helped to retard atrazine leaching.  相似文献   
118.
This study addressed the effects of land use and slope position on soil inorganic nitrogen and was conducted in small watersheds. The study covered three land use types: tropical cloud forest, grassland, and coffee crop. To conduct this research, typical slope small watersheds were chosen in each land use type. Slopes were divided into three positions: shoulder, backslope, and footslope. At the center of each slope position, soil sampling was carried out. Soil inorganic nitrogen was measured monthly during a period of 14 months (July 2005–August 2006) with 11 observations. Significant differences in soil NH4 +–N and NO3 –N content were detected for both land use and sampling date effects, as well as for interactions. A significant slope position-by-sampling date interaction was found only in coffee crop for NO3 –N content. In tropical cloud forest and grassland, high soil NH4 +–N and low NO3 –N content were recorded, while soil NO3 –N content was high in coffee crop. Low NO3 –N contents could mean a substantial microbial assimilation of NO3 –N, constituting an important mechanism for nitrogen retention. Across the entire land use set, the relationship between soil temperature and soil inorganic N concentration was described by an exponential decay function (N = 33 + 2459exp−0.23T, R 2 = 0.44, P < 0.0001). This study also showed that together, soil temperature and gravimetric soil water content explained more variation in soil inorganic N concentration than gravimetric soil water content alone.  相似文献   
119.
Pereira Filho, Augusto J., Richard E. Carbone, John E. Janowiak, Phillip Arkin, Robert Joyce, Ricardo Hallak, and Camila G.M. Ramos, 2010. Satellite Rainfall Estimates Over South America – Possible Applicability to the Water Management of Large Watersheds. Journal of the American Water Resources Association (JAWRA) 46(2):344-360. DOI: 10.1111/j.1752-1688.2009.00406.x Abstract: This work analyzes high-resolution precipitation data from satellite-derived rainfall estimates over South America, especially over the Amazon Basin. The goal is to examine whether satellite-derived precipitation estimates can be used in hydrology and in the management of larger watersheds of South America. High spatial-temporal resolution precipitation estimates obtained with the CMORPH method serve this purpose while providing an additional hydrometeorological perspective on the convective regime over South America and its predictability. CMORPH rainfall estimates at 8-km spatial resolution for 2003 and 2004 were compared with available rain gauge measurements at daily, monthly, and yearly accumulation time scales. The results show the correlation between satellite-derived and gauge-measured precipitation increases with accumulation period from daily to monthly, especially during the rainy season. Time-longitude diagrams of CMORPH hourly rainfall show the genesis, strength, longevity, and phase speed of convective systems. Hourly rainfall analyses indicate that convection over the Amazon region is often more organized than previously thought, thus inferring that basin scale predictions of rainfall for hydrological and water management purposes have the potential to become more skillful. Flow estimates based on CMORPH and the rain gauge network are compared to long-term observed average flow. The results suggest this satellite-based rainfall estimation technique has considerable utility. Other statistics for monthly accumulations also suggest CMORPH can be an important source of rainfall information at smaller spatial scales where in situ observations are lacking.  相似文献   
120.
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