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   572篇
  免费   3篇
  国内免费   6篇
安全科学   5篇
废物处理   39篇
环保管理   58篇
综合类   45篇
基础理论   134篇
污染及防治   162篇
评价与监测   110篇
社会与环境   27篇
灾害及防治   1篇
  2023年   15篇
  2022年   49篇
  2021年   32篇
  2020年   10篇
  2019年   11篇
  2018年   18篇
  2017年   15篇
  2016年   27篇
  2015年   17篇
  2014年   30篇
  2013年   56篇
  2012年   28篇
  2011年   31篇
  2010年   36篇
  2009年   22篇
  2008年   34篇
  2007年   27篇
  2006年   20篇
  2005年   14篇
  2004年   11篇
  2003年   13篇
  2002年   15篇
  2001年   7篇
  2000年   3篇
  1999年   5篇
  1998年   3篇
  1997年   1篇
  1996年   2篇
  1995年   2篇
  1994年   4篇
  1992年   4篇
  1991年   1篇
  1989年   2篇
  1984年   1篇
  1980年   1篇
  1978年   1篇
  1976年   1篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
  1969年   1篇
  1966年   1篇
  1964年   1篇
  1961年   3篇
  1960年   1篇
  1958年   1篇
  1957年   1篇
排序方式: 共有581条查询结果,搜索用时 234 毫秒
161.
The river Hindon is one of the important tributaries of river Yamuna in western Uttar Pradesh (India) and carries pollution loads from various municipal and industrial units and surrounding agricultural areas. The main sources of pollution in the river include municipal wastes from Saharanpur, Muzaffarnagar and Ghaziabad urban areas and industrial effluents of sugar, pulp and paper, distilleries and other miscellaneous industries through tributaries as well as direct inputs. In this paper, chemical mass balance approach has been used to assess the contribution from non-point sources of pollution to the river. The river system has been divided into three stretches depending on the land use pattern. The contribution of point sources in the upper and lower stretches are 95 and 81% respectively of the total flow of the river while there is no point source input in the middle stretch. Mass balance calculations indicate that contribution of nitrate and phosphate from non-point sources amounts to 15.5 and 6.9% in the upper stretch and 13.1 and 16.6% in the lower stretch respectively. Observed differences in the load along the river may be attributed to uncharacterized sources of pollution due to agricultural activities, remobilization from or entrainment of contaminated bottom sediments, ground water contribution or a combination of these sources.  相似文献   
162.
An area of 0.6 km(2) in the manganese nodule field of the Central Indian Basin was physically disturbed and sediments discharged in the near bottom waters to simulate seabed mining and study its impact on benthic ecosystem. An estimated 2 to 3 tonnes of sedimentary organic carbon (C(org)) was resuspended into the water column during a 9-day experiment. The majority of the sediment cores from within the disturbed area and areas towards the south showed a ~30% increase in C(org) content as well as an increase in carbon burial rates after disturbance, though with a reduction in carbon/phosphorus ratios. High specific surface area (SSA~25 m(2) g(-1)) and low C(org)/SSA ratios (mostly <0.5) are typical of deep-sea sediments. The increased C(org) values were probably due to the organic matter from dead biota and the migration and redeposition of fine-grained, organic-rich particles. Spatial distribution patterns of C(org) contents of cores taken before and after disturbance were used to infer the direction of plume migration and re-sedimentation. A positive relationship was observed between total and labile C(org) and macrobenthos density and total bacterial numbers prior to disturbance, whereas a negative relationship was seen after disturbance owing to drastic reduction in the density of macrofauna and bacteria. Overall decrease in labile organic matter, benthic biota and redistribution of organic matter suggest that the commercial mining of manganese nodules may have a significant immediate negative effect on the benthic ecosystem inducing changes in benthic community structure.  相似文献   
163.
In order to evaluate the exposure of the northern India rural population to polyaromatic hydrocarbon (PAH) inhalation, indoor pollution was assessed by collecting and analyzing the respirable particulate matter PM2.5 and PM10 in several homes of the village Bhithauli near Lucknow, UP. The home selection was determined by a survey. Given the nature of biomass used for cooking, homes were divided into two groups, one using all kinds of biomass and the second type using plant materials only. Indoor mean concentrations of PM2.5 and associated PAHs during cooking ranged from 1.19 ± 0.29 to 2.38 ± 0.35 and 6.21 ± 1.54 to 12.43 ± 1.15 μg/m3, respectively. Similarly, PM10 and total PAHs were in the range of 3.95 ± 1.21 to 8.81 ± 0.78 and 7.75 ± 1.42 to 15.77 ± 1.05 μg/m3, respectively. The pollutant levels during cooking were significantly higher compared to the noncooking period. The study confirmed that indoor pollution depends on the kind of biomass fuel used for cooking.  相似文献   
164.
This study was carried out in three different cities of western Madhya Pradesh (India) to investigate the effects of long-term irrigation with industrial waste water (IWW), contaminated groundwater (CGW), and untreated municipal sewage water (USW) on soil fertility as well as on wheat crop yield. Irrigation with these three types of polluted water increased organic matter content as well as contents of available P (with IWW and USW only), available K, available S, available Zn, available Cu (IWW only), and available Mn (IWW and CGW only). The magnitude of improvement in soil fertility status was the highest in the case of USW, followed by IWW and finally, by CGW. Concentrations of Na in wheat leaf tissue increased by 198 and 58 % whereas concentrations of Ca decreased significantly by 16 and 13 % due to the use of IWW and CGW, respectively, resulting in poor Ca nutrition to the crop. Although wheat grain yield increased considerably due to USW, the same recorded significant decreases with IWW and CGW. In spite of the enhancement in the available nutrient status, decrease in wheat grain yield with the use of IWW and CGW could be due to the build-up of salts in the soil and an imbalance in the Na/Ca ratio in wheat crops irrigated with IWW and CGW. The adverse effect on wheat productivity was more pronounced with IWW as compared to CGW.  相似文献   
165.
166.
Arsenic in the soil and water of eastern districts of Uttar Pradesh (Ballia and Ghazipur) was estimated. Survey results revealed that arsenic in soil samples ranged from 5.40 to 15.43 parts per million (ppm). In water samples, it ranged from 43.75 to 620.75 parts per billion (ppb) which far exceeded the permissible limit of 10 ppb as recommended by the World Health Organization. Maximum concentration of arsenic in water was found in Haldi village of Ballia (620.75 ppb). However, mean arsenic concentration in water followed the order: Karkatpur (257.21 ppb) < Haldi (310.15 ppb) < Sohaon (346.94 ppb) < Dharmarpur (401.75 ppb). In case of soil, maximum arsenic was detected in soil of Sohaon (15.43 ppm). Mean arsenic levels in soils followed the order: Karkatpur (9.24 ppm) < Haldi (9.82 ppm) < Dharmarpur (11.32 ppm) < Sohaon (14.08 ppm). Arsenic levels were higher in soils collected from 15–30 cm depth than 0–15 cm from the soil surface.  相似文献   
167.
Persistence of cypermethrin, deltamethrin, profenofos, and triazophos in cauliflower curd was studied, following application of two premix formulations viz: Roket 44EC (profenofos 40 % + cypermethrin 4 %) and Anaconda Plus 36EC (triazophos 35 % + deltamethrin 1 %) at recommended (1.0 L ha?1) and double doses (2.0 L ha?1). In the case of Roket 44EC, residues of cypermethrin dissipated with the half-life values of 1.5–2.1 days, whereas residues of profenofos dissipated with the half-life of 2.9–3.3 days on cauliflower curd. In the case of Anaconda, residues of triazophos and deltamethrin dissipated from curd with the half-life values of 2.6–3.0 and 2.2–2.6 days, respectively. Both the combination mix significantly reduced the aphid population up to 14 days after spray and increased the yield by 155–160 % over control. Anaconda (2.0 L ha?1) treated plots yielded the highest number of marketable curds. Based on risk assessment analysis, safe waiting period of 3 and 5 days has been suggested for Roket 44EC and Anaconda Plus 36EC, respectively, in cauliflower at recommended dose of application.  相似文献   
168.
The prevalence of fluorosis is mainly due to the consumption of more fluoride (F?1) through drinking water, vegetables, and crops. The objective of the study was mapping of F?1 endemic area of Newai Tehsil, Tonk district, Rajasthan, India. For the present study, water, soil (0–45 cm), and vegetation samples were collected from 17 villages. Fluoride concentration in water samples ranged from 0.3 to 9.8 mg/l. Out of 17 villages studied, the amounts of F?1 content of eight villages were found to exceed the permissible limits. Labile F?1 content and total F?1 content in soil samples ranges 11.00–70.05 mg/l and 50.3–179.63 μg g?1, respectively. F?1 content in tree species was found in this order Azadirachta indica 47.3255.76 μg g?1 > Prosopis juliflora 40.16–49.63 μg g?1 > Acacia tortilis 34.39–43.60 μg g?1. While in case of leafy vegetables, F?1 content order was Chenopodium album 54.23–98.42 μg g?1 > Spinacea oleracea 30.41–64.09 μg g?1 > Mentha arvensis 35.4851.97 μg g?1. The order of F?1 content in crops was found as 41.04 μg g?1 Pennisetum glaucum > 13.61 μg g?1 Brassica juncea > 7.98 μg g?1 Triticum sativum in Krishi Vigyan Kendra (KVK) farms. Among vegetation, the leafy vegetables have more F?1 content. From the results, it is suggested that the people of KVK farms should avoid the use of highly F?1 containing water for irrigation and drinking purpose. It has been recommended to the government authority to take serious steps to supply drinking water with low F?1 concentration for the fluorosis affected villages. Further, grow more F?1 hyperaccumulator plants in F?1 endemic areas to lower the F?1 content of the soils.  相似文献   
169.
Urbanisation is a ubiquitous phenomenon with greater prominence in developing nations. Urban expansion involves land conversions from vegetated moisture-rich to impervious moisture-deficient land surfaces. The urban land transformations alter biophysical parameters in a mode that promotes development of heat islands and degrades environmental health. This study elaborates relationships among various environmental variables using remote sensing dataset to study spatio-temporal footprint of urbanisation in Surat city. Landsat Thematic Mapper satellite data were used in conjugation with geo-spatial techniques to study urbanisation and correlation among various satellite-derived biophysical parameters, [Normalised Difference Vegetation Index, Normalised Difference Built-up Index, Normalised Difference Water Index, Normalised Difference Bareness Index, Modified NDWI and land surface temperature (LST)]. Land use land cover was prepared using hierarchical decision tree classification with an accuracy of 90.4 % (kappa?=?0.88) for 1990 and 85 % (kappa?=?0.81) for 2009. It was found that the city has expanded over 42.75 km2 within a decade, and these changes resulted in elevated surface temperatures. For example, transformation from vegetation to built-up has resulted in 5.5?±?2.6 °C increase in land surface temperature, vegetation to fallow 6.7?±?3 °C, fallow to built-up is 3.5?±?2.9 °C and built-up to dense built-up is 5.3?±?2.8 °C. Directional profiling for LST was done to study spatial patterns of LST in and around Surat city. Emergence of two new LST peaks for 2009 was observed in N–S and NE–SW profiles.  相似文献   
170.
Inverse modeling technique based on nonlinear least square regression method (LSRM) is developed for the identification of aquatic source and transport parameters. Instantaneous line source release model in two-dimensional domain and continuous point source release model in three-dimensional domain are used for the purpose. Case studies have been carried out for both types of releases to illustrate their application. Error analysis has been carried out to identify the maximum error that can be tolerated in the input concentration data used in the inverse model and to specify the minimum number of sampling points to generate such input data. The LSRM is compared with the well-established correlation coefficient optimization method for instantaneous line source release model, and good comparison is observed between them. The LSRM is used to quantitatively estimate the releases of different radionuclides into the Pacific Ocean which has resulted due to the discharge of highly radioactive liquid effluent from the affected Daiichi Nuclear Power Station at Fukushima in Japan. The measured concentrations of these radionuclides in seawater samples collected from two sampling points near Fukushima are used for the estimation. The average release works out to be 1.09?×?1016 for 131I, 3.4?×?1015 Bq for 134Cs, and 3.57?×?1015 Bq for 137Cs. Very good agreement is observed between the releases estimated in this study and those estimated by other different agencies.  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