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   1188篇
  免费   8篇
  国内免费   29篇
安全科学   12篇
废物处理   57篇
环保管理   156篇
综合类   101篇
基础理论   197篇
环境理论   1篇
污染及防治   424篇
评价与监测   210篇
社会与环境   62篇
灾害及防治   5篇
  2023年   33篇
  2022年   75篇
  2021年   64篇
  2020年   13篇
  2019年   27篇
  2018年   41篇
  2017年   35篇
  2016年   54篇
  2015年   27篇
  2014年   51篇
  2013年   151篇
  2012年   55篇
  2011年   64篇
  2010年   56篇
  2009年   47篇
  2008年   68篇
  2007年   43篇
  2006年   45篇
  2005年   34篇
  2004年   32篇
  2003年   30篇
  2002年   21篇
  2001年   17篇
  2000年   10篇
  1999年   10篇
  1998年   4篇
  1997年   7篇
  1996年   6篇
  1993年   5篇
  1992年   7篇
  1991年   8篇
  1990年   3篇
  1989年   6篇
  1988年   3篇
  1987年   8篇
  1986年   4篇
  1985年   3篇
  1982年   5篇
  1978年   4篇
  1976年   6篇
  1975年   4篇
  1974年   2篇
  1972年   3篇
  1969年   5篇
  1968年   4篇
  1967年   2篇
  1965年   2篇
  1959年   2篇
  1957年   3篇
  1956年   2篇
排序方式: 共有1225条查询结果,搜索用时 15 毫秒
941.
942.
943.
944.
Carbon Sequestration Potential of Indian Forests   总被引:3,自引:0,他引:3  
The forestry sector can not only sustain its carbon but also has the potential to absorb carbon from the atmosphere. India has maintained approximately 64 Mha of forest cover for the last decade. The rate of afforestation in India is one of the highest among the tropical countries, currently estimated to be 2 Mha per annum. The annual productivity has increased from 0.7 m3 per hactare in 1985 to 1.37 m3 per hectare in 1995. Increase in annual productivity directly indicates an increase in forest biomass and hence higher carbon sequestration potential. The carbon pool for the Indian forests is estimated to be 2026.72 Mt for the year 1995. Estimates of annual carbon uptake increment suggest that our forests and plantations have been able to remove at least 0.125 Gt of CO2 from the atmosphere in the year 1995. Assuming that the present forest cover in India will sustain itself with a marginal annual increase by 0.5 Mha in area of plantations, we can expect our forests to continue to act as a net carbon sink in future.  相似文献   
945.
Dust from haul and transport roads are the major source of air pollution in opencast coal mining areas. Dust generated during mining operations pollutes air which causes different health problems. Various available techniques are implemented in the field to minimize and control dust in mining areas. However, they are not very effective because dust deposited on road surfaces are not removed by these techniques. For effective control of dust in opencast mining areas, it has to be regularly collected from road surfaces and may be converted into solid form, and subsequently can be used as a domestic fuel considering its physicochemical properties. The present paper describes a comparative study of qualitative and quantitative aspects of road dust samples of four coalfields of India. The pH of the dust was found to be in the range of 5.1–7.7. Moisture, ash, volatile matter, fixed carbon, water-holding capacity, bulk density, and specific gravity of dust samples were found to be in the range of 0.5–3.0%, 45–76%, 12.6–20.0%, 10.2–45.3%, 21.17–31.71%, 1.15–1.70, and 1.73–2.30 g cm−3, respectively. Observing the overall generation and characteristics of coal dust, it is suggested that coal dust from haul and transport roads of mining areas can be effectively collected and used as domestic fuel.  相似文献   
946.
The groundwater quality for drinking, domestic and irrigation in the village Lutfullapur Nawada, Loni, district Ghaziabad, U.P., India, has been assessed. Groundwater samples were collected, processed and analyzed for temperature, pH, conductivity, salinity, total alkalinity, carbonate alkalinity, bicarbonate alkalinity, total hardness, calcium hardness, magnesium hardness, total solids, total dissolved solids, total suspended solids, nitrate-nitrogen, chloride, fluoride, sulfate, phosphate, silica, sodium, potassium, calcium, magnesium, total chromium, cadmium, copper, iron, nickel, lead and zinc. A number of groundwater samples showed levels of electrical conductivity (EC), alkalinity, chloride, calcium, sodium, potassium and iron exceeding their permissible limits. Except iron, the other metals (Cr, Cd, Cu, Ni, Pb, and Zn) were analyzed below the permissible limits. The correlation matrices for 28 variables were performed. EC, salinity, TS and TDS had significant positive correlations among themselves and also with NO (3) (-) , Cl(-), alkalinity, Na(+), K(+), and Ca(2+). Fluoride was not significantly correlated with any of the parameters. NO (3) (-) was significantly positively correlated with Cl(-), alkalinity, Na(+), K(+) and Ca(2+). Chloride also correlated significantly with alkalinity, Na(+), K(+) and Ca(2+). Sodium showed a strong and positive correlation with K(+) and Ca(2+). pH was negatively correlated with most of the physicochemical parameters. This groundwater is classified as a normal sulfate and chloride type. Base-exchange indices classified 73% of the groundwater sources as the Na(+)-SO (4) (2-) type. The meteoric genesis indices demonstrated that 67% of groundwater sources belong to a deep meteoric water percolation type. Hydrochemical groundwater evaluations revealed that most of the groundwaters belong to the Na(+)-K(+)-Cl(-)-SO (4) (2-) type followed by Na(+)-K(+)-HCO (3) (-) type. Salinity, chlorinity and SAR indices indicated that majority of groundwater samples can be considered suitable for irrigation purposes.  相似文献   
947.
Residues of flubendiamide and desiodo flubendiamide were studied following three applications of flubendiamide 480 SC at 7 days interval at 90 and 180 g a.i. ha(-1) in/on brinjal fruits. An average initial deposit of 0.33 and 0.61 mg kg(-1) of flubendiamide was observed respectively after application at single and double dosages. The residues of flubendiamide dissipated quickly at both the dosages, and after 3 days, the extent of dissipation was found to be about 76% and 79% at the single and double dosages, respectively. Brinjal fruit samples analysed at different time intervals did not show the presence of desiodo flubendiamide. The half-life of flubendiamide was observed to be 0.62 and 0.54 days at single and double dosages, respectively. The limit of determination of flubendiamide and desiodo flubendiamide was observed to be 0.05 mg kg(-1). Soil samples analysed after 15 days of the last application did not reveal the presence of flubendiamide and desiodo flubendiamide at their determination limit of 0.05 mg kg(-1). An assessment of the total intake of flubendiamide resulting through the consumption of brinjal fruits and its comparison with acceptable daily intake seems to be quite safe from consumer point of view.  相似文献   
948.
In this study, an attempt has been made to work out water balance, determine rate of sedimentation and physico-chemical analysis of the lake water. The water balance is carried out using the mass balance equation to account for various input and output components. Sedimentation rates and pattern are estimated using (137)Cs and (210)Pb radiometric dating techniques. The physico-chemical analysis of the lake water is done by collecting samples from twelve locations of the lake at three different depths. The major inflow to the lake is catchment runoff, which accounts for nearly 56% of the total annual inflow and about 98% inflow takes place during monsoon period. The major outflow from the lake is weir overflow, which occurs in monsoon season only and accounts for about 85% of the total annual outflow. The estimated mean sedimentation rate in the lake is 0.58 +/- 0.028 cm/year. The estimated useful life of the lake based on post-1964 (appearance of the major peak of (137)Cs due to weapon fallout record pattern) average sedimentation rate is around 467 +/- 23 years. The lake has attained the hyper-eutrophic state due to high nitrogen and phosphorous contents in the lake water. Based on the trophic state index (TSI), the lake has become unsuitable for drinking, bathing and even for fish culture.  相似文献   
949.
Herbal formulations are getting popularity throughout the world and commercialized extensively for various medicinal properties. WHO has emphasized the need for quality assurance of herbal products, including testing of heavy metals and pesticides residues. 'Dashmoola', a popular herbal formulation, with immunomodulator and febrifugal properties, consists of ten single root drugs. In view of WHO guidelines, single herbal drugs used in 'Dashmoola', were collected from different places of India for testing heavy metals and persistent pesticides residue. Although use of roots in 'Dashmoola' is prescribed in original ayurvedic literature but now many pharmacies use stem in place of roots. Therefore, in the present study both roots and stems were selected for estimation of six heavy metals namely arsenic (As), mercury (Hg), lead (Pb), cadmium (Cd), chromium (Cr) and nickel (Ni). Apart from these, the organochlorine pesticides residue viz. different metabolites of DDT, DDE, isomers of HCH and alpha-endosulfan were checked in total 40 samples of single crude drugs. Heavy metals except Hg, were present in most of the samples. In few samples Pb and Cd concentration were beyond the WHO permissible limits. Although alpha-HCH and gamma-HCH were present in almost all the samples, but other pesticides were not detected in these samples. DDT and DDE were found only in two samples.  相似文献   
950.
A study was conducted to evaluate the water quality of Jaipur City. Groundwater samples from hand pumps and tube wells of eleven sampling stations were analyzed during monsoon session with the help of standard methods of APHA. The analytical results shows higher concentration of total dissolved solids, electrical conductivity, total hardness and nitrate, which indicate signs of deterioration but values of pH, calcium, magnesium, sulphate and fluoride are within permissible limit as per WHO standards. From the Hill-Piper trilinear diagram, it is observed that the majority of ground water from sampling stations are calcium-magnesium-chloride-sulphate type water. The values of sodium absorption ratio and electrical conductivity of the ground water were plotted in the US salinity laboratory diagram for irrigation water. Most of the samples fall in C3S1 quality with high salinity hazard and low sodium hazard. Chemical analysis of groundwater shows that mean concentration of cation (in meq/l) is in order magnesium > sodium > calcium > potassium while for the anion (in meq/l) it is chloride > bicarbonate > sulphate > nitrate > carbonate > fluoride.  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