全文获取类型
收费全文 | 511篇 |
免费 | 9篇 |
国内免费 | 57篇 |
专业分类
安全科学 | 7篇 |
废物处理 | 22篇 |
环保管理 | 51篇 |
综合类 | 123篇 |
基础理论 | 112篇 |
污染及防治 | 172篇 |
评价与监测 | 69篇 |
社会与环境 | 18篇 |
灾害及防治 | 3篇 |
出版年
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 13篇 |
2020年 | 14篇 |
2019年 | 9篇 |
2018年 | 9篇 |
2017年 | 19篇 |
2016年 | 23篇 |
2015年 | 14篇 |
2014年 | 23篇 |
2013年 | 62篇 |
2012年 | 11篇 |
2011年 | 20篇 |
2010年 | 25篇 |
2009年 | 23篇 |
2008年 | 23篇 |
2007年 | 25篇 |
2006年 | 23篇 |
2005年 | 23篇 |
2004年 | 18篇 |
2003年 | 13篇 |
2002年 | 19篇 |
2001年 | 21篇 |
2000年 | 11篇 |
1999年 | 9篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1982年 | 5篇 |
1979年 | 2篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1971年 | 4篇 |
1966年 | 4篇 |
1965年 | 5篇 |
1964年 | 4篇 |
1963年 | 5篇 |
1961年 | 6篇 |
1960年 | 2篇 |
1958年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有577条查询结果,搜索用时 31 毫秒
431.
K. V. Satish K. R. L. Saranya C. Sudhakar Reddy P. Hari Krishna C. S. Jha P. V. V. Prasada Rao 《Environmental monitoring and assessment》2014,186(12):8125-8140
Deforestation in the biosphere reserves, which are key Protected Areas has negative impacts on biodiversity, climate, carbon fluxes and livelihoods. Comprehensive study of deforestation in biosphere reserves is required to assess the impact of the management effectiveness. This article assesses the changes in forest cover in various zones and protected areas of Nilgiri Biosphere Reserve, the first declared biosphere reserve in India which forms part of Western Ghats-a global biodiversity hotspot. In this study, we have mapped the forests from earliest available topographical maps and multi-temporal satellite data spanning from 1920’s to 2012 period. Mapping of spatial extent of forest cover, vegetation types and land cover was carried out using visual interpretation technique. A grid cell of 1 km?×?1 km was generated for time series change analysis to understand the patterns in spatial distribution of forest cover (1920–1973–1989–1999–2006–2012). The total forest area of biosphere reserve was found to be 5,806.5 km2 (93.8 % of total geographical area) in 1920. Overall loss of forest cover was estimated as 1,423.6 km2 (24.5 % of the total forest) with reference to 1920. Among the six Protected Areas, annual deforestation rate of >0.5 was found in Wayanad wildlife sanctuary during 1920–1973. The deforestation in Nilgiri Biosphere Reserve is mainly attributed to conversion of forests to plantations and agriculture along with submergence due to construction of dams during 1920 to 1989. Grid wise analysis indicates that 851 grids have undergone large-scale negative changes of >75 ha of forest loss during 1920–1973 while, only 15 grids have shown >75 ha loss during 1973–1989. Annual net rate of deforestation for the period of 1920 to 1973 was calculated as 0.5 followed by 0.1 for 1973 to 1989. Our analysis shows that there was large-scale deforestation before the declaration of area as biosphere reserve in 1986; however, the deforestation has drastically reduced after the declaration due to high degree of protection, thus indicating the secure future of reserve in the long term under the current forest management practices. The present work will stand as the most up-to-date assessment on the forest cover of the Nilgiri Biosphere Reserve with immediate applications in monitoring and management of forest biodiversity. 相似文献
432.
433.
Assessment of nitrate contamination due to groundwater pollution in north eastern part of Anantapur District, A.P. India 总被引:1,自引:0,他引:1
Reddy AG Niranjan Kumar K Subba Rao D Sambashiva Rao S 《Environmental monitoring and assessment》2009,148(1-4):463-476
The north eastern part of Anantapur district is in the state of Andhra Pradesh, India, is significant as it is covered by varied geological formations and has different land use and irrigation practices. Though ground water is the major drinking water source, deterioration in its quality is going unchecked. In such agro-economy based rural areas, the nitrate contamination is rampant and much attention has not been drawn towards this anthropogenic pollution. In the study area ground water samples from different hydrogeological set-up have been collected during the pre and post monsoon seasons and analysed for the major ions such as Ca, Mg, Na, K, CO(3), HCO(3), Cl, SO(4), NO(3) and F. The study revealed that 65% of the samples were found to be unsuitable for drinking purposes in the pre monsoon season and 45% in the post monsoon due to excess nitrate (>45 mg/l) content in the ground water. Among the different seasons and environs, nitrate was in highest concentration in the granitic terrain and canal command areas during pre monsoon season. The nitrate was found to decrease with depth in all the hydrogeological set-ups in both the seasons. Intense agriculture practices, improper sewerage and organic waste disposal methods were observed to contribute nitrate to the shallow and moderately deep aquifers. 相似文献
434.
Anirban Akhand Abhra Chanda Sachinandan Dutta Sudip Manna Pranabes Sanyal Sugata Hazra K. H. Rao V. K. Dadhwal 《Environmental monitoring and assessment》2013,185(8):6505-6515
A comprehensive attempt has been made to evaluate the diurnal and spatial pattern of CO2 exchange between the atmosphere and water along the estuarine track of Indian Sundarbans during the two summer months, April and May, 2011. Rigorous field observations were carried out which included the hourly measurements of total alkalinity, pH, fugacity of CO2 in ambient air and water surface, dissolved oxygen, and chlorophyll a. The estuarine water was found rich in total alkalinity and was oversaturated with CO2 throughout the diurnal cycle in the two stations situated at the inner and middle estuary, respectively, whereas an entirely reverse situation was observed in the outer fringes. The fugacity of CO2 in water ranged from 152 to 657 μatm during the study period. The percentage of over-saturation in inner and middle estuary varied from 103 to 168 and 103 to 176 %, respectively, whereas the degree of under-saturation in the outer estuary lied between 40 and 99 %. Chlorophyll a concentrations were found higher in the outer estuary (12.3?±?2.2 mg?m?3) compared to the middle (6.4?±?0.6 mg?m?3) and inner parts (1.6?±?0.2 mg?m?3), followed by a similar decreasing pattern in nutrient availability from the outer to inner estuary. The sampling stations situated at the inner and middle estuary acted as a net source of 29.69 and 23.62 mg?CO2?m?2 day?1, respectively, whereas the outer station behaved as a net sink of ?33.37 mg?CO2 m?2 day?1. The study of primary production and community respiration further supports the heterotrophic nature of the estuary in the inner region while the outer periphery was marked by dominant autotrophic character. These contrasting results are in parity with the source characters of many inner estuaries and sinking characters of the outer estuaries situated at the distal continental shelf areas. 相似文献
435.
Rao NS Rao PS Reddy GV Nagamani M Vidyasagar G Satyanarayana NL 《Environmental monitoring and assessment》2012,184(8):5189-5214
Study on chemical characteristics of groundwater and impacts of groundwater quality on human health, plant growth, and industrial sector is essential to control and improve the water quality in every part of the country. The area of the Varaha River Basin is chosen for the present study, where the Precambrian Eastern Ghats underlain the Recent sediments. Groundwater quality is of mostly brackish and very hard, caused by the sources of geogenic, anthropogenic, and marine origin. The resulting groundwater is characterized by Na(+)?>?Mg(2+)?>?Ca(2+)?:?[Formula: see text]?>?Cl(-)?>?[Formula: see text], Na(+)?>?Mg(2+)?>?Ca(2+)?:?[Formula: see text]?>?Cl(-)?>?[Formula: see text]?>?[Formula: see text], Na(+)?>?Mg(2+)?>?Ca(2+)?:?[Formula: see text]?>?Cl(-), and Na(+)?>?Mg(2+)?>?Ca(2+)?:?Cl(-)?>?[Formula: see text]?>?[Formula: see text] facies, following the topographical and water flow-path conditions. The genetic geochemical evolution of groundwater ([Formula: see text] and Cl(-)-[Formula: see text] types under major group of [Formula: see text]) and the hydrogeochemical signatures (Na(+)/Cl(-), >1 and [Formula: see text]/Cl(-), <1) indicate that the groundwater is of originally fresh quality, but is subsequently modified to brackish by the influences of anthropogenic and marine sources, which also supported by the statistical analysis. The concentrations of total dissolved solids (TDS), TH, Mg(2+), Na(+), K(+), [Formula: see text], Cl(-), [Formula: see text], and F(-) are above the recommended limits prescribed for drinking water in many locations. The quality of groundwater is of mostly moderate in comparison with the salinity hazard versus sodium hazard, the total salt concentration versus percent sodium, the residual sodium carbonate, and the magnesium hazard, but is of mostly suitable with respect to the permeability index for irrigation. The higher concentrations of TDS, TH, [Formula: see text], Cl(-), and [Formula: see text] in the groundwater cause the undesirable effects of incrustation and corrosion in many locations. Appropriate management measures are, therefore, suggested to improve the groundwater quality. 相似文献
436.
Evaluation of significant sources influencing the variation of water quality of Kandla creek, Gulf of Katchchh, using PCA 总被引:1,自引:0,他引:1
S. G. Dalal P. V. Shirodkar T. G. Jagtap B. G. Naik G. S. Rao 《Environmental monitoring and assessment》2010,163(1-4):49-56
To evaluate the significant sources contributing to water quality parameters, we used principal component analysis (PCA) for the interpretation of a large complex data matrix obtained from the Kandla creek environmental monitoring program. The data set consists of analytical results of a seasonal sampling survey conducted over 2 years at four stations. PCA indicates five principal components to be responsible for the data structure and explains 76% of the total variance of the data set. The study stresses the need to include new parameters in the analysis in order to make the interpretation of principal components more meaningful. The PCA could be applied as a useful tool to eliminate multi-collinearity problems and to remove the indirect effect of parameters. 相似文献
437.
Ground-level concentrations of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) were monitored over three seasons, i.e., post-monsoon (September–October), winter (January–February), and summer (May–June) for 1 year during 2013–2014 in Nagpur City in India. The selected gases had moderate to high variation both spatially (residential, commercial, traffic intersections, residential cum commercial sites) and temporally (at 7:00, 13:00, 18:00, and 23:00 hours in all three seasons). Concentrations of gases were randomly distributed diurnally over city in all seasons, and there was no specific increasing or decreasing trend with time in a day. Average CO2 and N2O concentrations in winter were higher over post-monsoon and summer while CH4 had highest average concentration in summer. Observed concentrations of CO2 were predominantly above global average of 400 ppmv while N2O and CH4 concentrations frequently dropped down below global average of 327 ppbv and 1.8 ppmv, respectively. Two-tailed Student’s t test indicated that post-monsoon CO2 concentrations were statistically different from summer but not so from winter, while difference between summer and winter concentrations was statistically significant (P < 0.05). CH4 concentrations in all seasons were statistically at par to each other. In case of N2O, concentrations in post-monsoon were statistically different from summer but not so from winter, while difference between summer and winter concentrations was statistically significant (P < 0.05). Average ground-level concentrations of the gases calculated for three seasons together were higher in commercial areas. Environmental management priorities vis a vis greenhouse gas emissions in the city are also discussed. 相似文献
438.
Sorption of cadmium and zinc from aqueous solutions by zeolite 4A, zeolite 13X and bentonite 总被引:3,自引:0,他引:3
Purna Chandra Rao G Satyaveni S Ramesh A Seshaiah K Murthy KS Choudary NV 《Journal of environmental management》2006,81(3):265-272
The sorption and desorption of cadmium and zinc on zeolite 4A, zeolite 13X and bentonite has been studied using batch sorption studies. Parameters such as equilibrium time, effect of pH and sorbent dose were studied. The sorbents exhibited good sorption potential for cadmium and zinc with a peak value at pH 6.0 and 6.5, respectively. The sorption followed the Freundlich sorption model. More than 70% sorption occurred within 20 min and equilibrium was attained at around 90 min for the three sorbents. The metals sorption by zeolite 4A was higher than that by zeolite 13X and bentonite. The desorption studies were carried out using NaCl solution and the effect of NaCl concentration on desorption was also studied. Maximum desorption of 76% for cadmium and 80% for zinc occurred with 10% NaCl. 相似文献
439.
熵权物元分析模型在湖泊富营养化评价中的应用 总被引:13,自引:3,他引:10
根据熵权法确定评价指标权重,利用物元分析方法对湖泊富营养化进行综合评价,评价结果与属性识别理论方法、模糊隶属函数法进行对比,结果表明,利用物元分析法进行湖泊富营养化评价是可行的。 相似文献
440.
This study aimed to analyze the ecological, socio-economic and policy implications of land-use diversity in a traditional
village landscape (900–1,000 m amsl.) in the Garhwal region of Indian Himalaya. The village landscape was differentiated into three major land-use types viz.,
forests, settled agriculture and shifting agriculture. Settled agriculture was further differentiated into four agroecosystem
types viz., homegarden system (HGS), rainfed agroforestry system (RAS), rainfed crop system (RCS) and irrigated crop system
(ICS), and shifting agriculture system (SAS) was differentiated into different stages of a 4-year long cropping phase and
a 7-year long fallow phase, and forests into Community Forests (CF) and Reserve Forests (RF). HGS is the most productive agroecosystem,
with soil organic carbon and nutrient concentrations significantly higher than all other forest/agricultural land-uses. Farmers
capitalize upon crop diversity to cope with the risks and uncertainties of a monsoon climate and spatial variability in ecological
factors influencing productivity. The SAS, a land-use adopted as a means of acquiring inheritable rights over larger land
holdings provided in the policies during the 1890s, is less efficient in terms of land productivity than the traditional RAS
and HGS but is maintained for its high labour productivity coupled with availability of high-quality fuelwood from fallow
vegetation. Dominance of fodder trees in the RAS seems to derive from policies causing shortage of fodder available from forests.
Cultural norms have favoured equity by allowing hiring of labour only from within the village community and income from non-timber
forest products only to the weaker section of the society. Conversion of rainfed to irrigated cropping, a change facilitated
by the government, improves agricultural productivity but also increases pressure on forests due to higher rates of farmyard
manure input to the irrigated crops. Existing forest management systems are not effective in maintenance of a large basal
area in forests together with high levels of species richness, soil fertility and resistance to invasive alien species Lantana camara. Farmers have to spend huge amount of labour and time in producing manure, managing livestock and other subsidiary farm activities.
Interlinkages among agriculture, forests and rural economy suggest a need of replacing the present policies of treating agricultural
development, forest conservation and economic development as independent sectors by an integrated sustainable development
policy. The policy should promote technological and institutional innovations enabling parallel improvements in agricultural
productivity and functions of forest ecosystems. 相似文献