全文获取类型
收费全文 | 18007篇 |
免费 | 183篇 |
国内免费 | 163篇 |
专业分类
安全科学 | 512篇 |
废物处理 | 745篇 |
环保管理 | 2497篇 |
综合类 | 2438篇 |
基础理论 | 4805篇 |
环境理论 | 4篇 |
污染及防治 | 5229篇 |
评价与监测 | 1162篇 |
社会与环境 | 837篇 |
灾害及防治 | 124篇 |
出版年
2022年 | 127篇 |
2021年 | 156篇 |
2020年 | 99篇 |
2019年 | 141篇 |
2018年 | 245篇 |
2017年 | 243篇 |
2016年 | 402篇 |
2015年 | 339篇 |
2014年 | 506篇 |
2013年 | 1537篇 |
2012年 | 594篇 |
2011年 | 769篇 |
2010年 | 604篇 |
2009年 | 711篇 |
2008年 | 819篇 |
2007年 | 872篇 |
2006年 | 758篇 |
2005年 | 635篇 |
2004年 | 658篇 |
2003年 | 613篇 |
2002年 | 611篇 |
2001年 | 754篇 |
2000年 | 557篇 |
1999年 | 308篇 |
1998年 | 233篇 |
1997年 | 220篇 |
1996年 | 267篇 |
1995年 | 265篇 |
1994年 | 253篇 |
1993年 | 228篇 |
1992年 | 205篇 |
1991年 | 185篇 |
1990年 | 206篇 |
1989年 | 189篇 |
1988年 | 180篇 |
1987年 | 171篇 |
1986年 | 148篇 |
1985年 | 146篇 |
1984年 | 176篇 |
1983年 | 174篇 |
1982年 | 166篇 |
1981年 | 168篇 |
1980年 | 136篇 |
1979年 | 159篇 |
1978年 | 108篇 |
1977年 | 100篇 |
1976年 | 88篇 |
1975年 | 94篇 |
1973年 | 92篇 |
1972年 | 99篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
821.
This study is an assessment of the possible effects of the dredging project on the water quality of the surrounding environment. Water quality data for the Bonny offshore river were collected. The parameters assessed were temperature, dissolved oxygen (DO), pH, biochemical oxygen demand (BOD), total dissolved solids (TDS), total suspended solids (TSS), nitrogen as nitrate, and phosphate. The concentrations of TDS, TSS, and nitrate far exceeded the permissible standard. There were significant differences between the dry and rainy season values of BOD5, TDS, TSS, nitrate, and phosphate. Also, the sediment physicochemical analysis indicated the presence of heavy metals such as Pb, Fe, Cd, Zn, Cr, and elements such as Ca, K, and Na. Following an assessment of the potential impact of the project using interaction matrix and checklist questionnaires, results showed that the major physicochemical parameters influenced by dredging are DO, TDS, TSS, heavy metals and calcium, potassium, and sodium. Mitigation measures for eliminating or reducing the negative impacts of dredging are presented. 相似文献
822.
C. Sudhakar Reddy C. S. Jha V. K. Dadhwal 《Environmental monitoring and assessment》2013,185(5):4399-4415
Deforestation and fragmentation are important concerns in managing and conserving tropical forests and have global significance. In the Indian context, in the last one century, the forests have undergone significant changes due to several policies undertaken by government as well as increased population pressure. The present study has brought out spatiotemporal changes in forest cover and variation in forest type in the state of Odisha (Orissa), India, during the last 75 years period. The mapping for the period of 1924–1935, 1975, 1985, 1995 and 2010 indicates that the forest cover accounts for 81,785.6 km2 (52.5 %), 56,661.1 km2 (36.4 %), 51,642.3 km2 (33.2 %), 49,773 km2 (32 %) and 48,669.4 km2 (31.3 %) of the study area, respectively. The study found the net forest cover decline as 40.5 % of the total forest and mean annual rate of deforestation as 0.69 %?year?1 during 1935 to 2010. There is a decline in annual rate of deforestation during 1995 to 2010 which was estimated as 0.15 %. Forest type-wise quantitative loss of forest cover reveals large scale deforestation of dry deciduous forests. The landscape analysis shows that the number of forest patches (per 1,000) are 2.463 in 1935, 10.390 in 1975, 11.899 in 1985, 12.193 in 1995 and 15.102 in 2010, which indicates high anthropogenic pressure on the forests. The mean patch size (km2) of forest decreased from 33.2 in 1935 to 5.5 in 1975 and reached to 3.2 by 2010. The study demonstrated that monitoring of long term forest changes, quantitative loss of forest types and landscape metrics provides critical inputs for management of forest resources. 相似文献
823.
L. D. Lacerda R. C. Campos R. E. Santelli 《Environmental monitoring and assessment》2013,185(5):4427-4447
Metal concentrations were evaluated in water, bottom sediments, and biota in four field campaigns from 2002 to 2004 in the Potiguar Basin, northeastern Brazil, where offshore oil exploration occurs. Analyses were performed by inductively coupled plasma mass spectrometry and inductively coupled plasma optical emission spectrometry. Total metal concentrations in water (dissolved?+?particulate) and sediments were in the range expected for coastal and oceanic areas. Abnormally high concentrations in waters were only found for Ba (80 μg?l?1) and Mn (12 μg?l?1) at the releasing point of one of the outfalls, and for the other metals, concentrations in water were found in stations closer to shore, suggesting continental inputs. In bottom sediments, only Fe and Mn showed abnormal concentrations closer to the effluent releasing point. Metal spatial distribution in shelf sediments showed the influence of the silt–clay fraction distribution, with deeper stations at the edge of the continental shelf, which are much richer in silt–clay fraction showing higher concentrations than shallower sediments typically dominated by carbonates. Metal concentrations in estuarine (mollusks and crustaceans) and marine (fish) organisms showed highest concentrations in oysters (Crassostrea rhizophorae). Fish tissues metal concentrations were similar between the continental shelf influenced by the oil exploration area and a control site. The results were within the range of concentrations reported for pristine environments without metals contamination. The global results suggest small, if any, alteration in metal concentrations due to the oil exploration activity in the Potiguar Basin. For monitoring purposes, the continental inputs and the distribution of the clay–silt fraction need to be taken into consideration for interpreting environmental monitoring results. 相似文献
824.
A. O. Oyeyiola C. M. Davidson K. O. Olayinka T. O. Oluseyi B. I. Alo 《Environmental monitoring and assessment》2013,185(3):2167-2177
Surface sediments collected from the Lagos Lagoon, Nigeria, and three adjoining rivers were analysed for their physicochemical properties and pseudo-total concentration of the potentially toxic metals (PTM) Cd, Cr, Cu, Pb and Zn. The concentration of the PTM varied seasonally and spatially. Odo-Iyaalaro was observed to be the most polluted river, with highest concentrations of 42.1 mg kg?1, 102 mg kg?1, 185 mg kg?1, 154 mg kg?1 and 1040 mg kg?1 of Cd, Cr, Cu, Pb and Zn, respectively, while Ibeshe River was the least contaminated, apart from a site affected by Cu from the textile industry. Some of the sediments were found to be above the consensus-based probable effect concentrations and Dutch sediment guideline for metals. Overall metal concentrations were similar to those reported for other tropical lagoon and estuarine systems affected by anthropogenic inputs as a result of rapid urbanisation. Due to the large number of samples, principal component analysis was used to examine relationships within the data set. Generally, sediments collected during the dry season were observed to have higher concentration of PTM than those collected during the rainy season. This means that PTM could accumulate over a prolonged period and then be released relatively rapidly, on an annual basis, into tropical lagoon systems. 相似文献
825.
Bradley S. Williams Ellen D’Amico Jude H. Kastens James H. Thorp Joseph E. Flotemersch Martin C. Thoms 《Environmental monitoring and assessment》2013,185(9):7485-7499
River systems consist of hydrogeomorphic patches (HPs) that emerge at multiple spatiotemporal scales. Functional process zones (FPZs) are HPs that exist at the river valley scale and are important strata for framing whole-watershed research questions and management plans. Hierarchical classification procedures aid in HP identification by grouping sections of river based on their hydrogeomorphic character; however, collecting data required for such procedures with field-based methods is often impractical. We developed a set of GIS-based tools that facilitate rapid, low cost riverine landscape characterization and FPZ classification. Our tools, termed RESonate, consist of a custom toolbox designed for ESRI ArcGIS®. RESonate automatically extracts 13 hydrogeomorphic variables from readily available geospatial datasets and datasets derived from modeling procedures. An advanced 2D flood model, FLDPLN, designed for MATLAB® is used to determine valley morphology by systematically flooding river networks. When used in conjunction with other modeling procedures, RESonate and FLDPLN can assess the character of large river networks quickly and at very low costs. Here we describe tool and model functions in addition to their benefits, limitations, and applications. 相似文献
826.
R. Maurício C. J. Dias N. Jubilado F. Santana 《Environmental monitoring and assessment》2013,185(10):8125-8133
In this report, the development of an online, noninvasive, measurement method of the biofilm thickness in a liquid phase is presented. The method is based in the analysis of the ultrasound wave pulse-echo behavior in a liquid phase reproducing the real reactor conditions. It does not imply the removal of the biomass from the support or any kind of intervention in the support (pipes) to detect and perform the measurements (non-invasiveness). The developed method allows for its sensor to be easily and quickly mounted and unmounted in any location along a pipe or reactor wall. Finally, this method is an important innovation because it allows the thickness measurement of a biofilm, in liquid phase conditions that can be used in monitoring programs, to help in scheduling cleaning actions to remove the unwanted biofilm, in several application areas, namely in potable water supply pipes. 相似文献
827.
Vikrant Jaryan Sanjay Kr. Uniyal R. C. Gupta R. D. Singh 《Environmental monitoring and assessment》2013,185(7):6129-6153
Recognizing the array of effects that invasive alien species have, documenting their status from biodiversity rich regions has been much emphasized. Lack of such studies is a major limitation that hampers proper management of alien species. The present paper, therefore, documents the alien flora of the Indian Himalayan state of Himachal Pradesh (HP) based on data obtained from literature and herbarium records. The alien flora of HP comprises of 497 species belonging to 85 families. Majority of them belong to family Asteraceae (59 species), followed by Poaceae (47 species) and Fabaceae (43 species). Amongst the genera, Ipomoea (9 species), Eucalyptus and Euphorbia (7 species each) are the most predominant. Herbs constitute the majority (i.e., 73 %) of alien species and a large percentage of them (i.e., 22.94 %) have South America as their native region. Further, of the total alien species, 248 are intentional introductions and majority (31 % species) have been introduced for ornamental purposes. It was revealed that 34 % species have naturalized while 29 % species have become invasive. Today, in addition to human-disturbed landscapes, alien species have also been reported from dense forests. Himalaya being a biodiversity hotspot and HP being a bio-rich Himalayan state, it is hoped that this inventory and assessment of alien flora will help in designing informed management and monitoring strategies against problematic plant invasions in the state. 相似文献
828.
Luis Fernando Cáceres Choque Oswaldo E. Ramos Ramos Sulema N. Valdez Castro Rigoberto R. Choque Aspiazu Rocío G. Choque Mamani Samuel G. Fernández Alcazar Ondra Sracek Prosun Bhattacharya 《Environmental monitoring and assessment》2013,185(12):9979-9994
Chemical weathering is one of the major geochemical processes that control the mobilization of heavy metals. The present study provides the first report on heavy metal fractionation in sediments (8–156 m) of Lake Titicaca (3,820 m a.s.l.), which is shared by the Republic of Peru and the Plurinational State of Bolivia. Both contents of total Cu, Fe, Ni, Co, Mn, Cd, Pb, and Zn and also the fractionation of these heavy metals associated with four different fractions have been determined following the BCR scheme. The principal component analysis suggests that Co, Ni, and Cd can be attributed to natural sources related to the mineralized geological formations. Moreover, the sources of Cu, Fe, and Mn are effluents and wastes generated from mining activities, while Pb and Zn also suggest that their common source is associated to mining activities. According to the Risk Assessment Code, there is a moderate to high risk related to Zn, Pb, Cd, Mn, Co, and Ni mobilization and/or remobilization from the bottom sediment to the water column. Furthermore, the Geoaccumulation Index and the Enrichment Factor reveal that Zn, Pb, and Cd are enriched in the sediments. The results suggest that the effluents from various traditional mining waste sites in both countries are the main source of heavy metal contamination in the sediments of Lake Titicaca. 相似文献
829.
Nafiseh Rang Zan S. P. Datta R. K. Rattan B. S. Dwivedi M. C. Meena 《Environmental monitoring and assessment》2013,185(12):10015-10025
Risk assessment of metal-contaminated soil depends on how precisely one can predict the solubility of metals in soils. Responses of plants and soil organisms to metal toxicity are explained by the variation in free metal ion activity in soil pore water. This study was undertaken to predict the free ion activity of Zn, Cu, Ni, Cd, and Pb in metal-contaminated soil as a function of pH, soil organic carbon, and extractable metal content. For this purpose, 21 surface soil samples (0–15 cm) were collected from agricultural lands of various locations receiving sewage sludge and industrial effluents for a long period. One soil sample was also collected from agricultural land which has been under intensive cropping and receiving irrigation through tube well water. Soil samples were varied widely in respect of physicochemical properties including metal content. Total Zn, Cu, Ni, Cd, and Pb in experimental soils were 2,015?±?3,373, 236?±?286, 103?±?192, 29.8?±?6.04, and 141?±?270 mg kg?1, respectively. Free metal ion activity, viz., pZn2+, pCu2+, pNi2+, pCd2+, and pPb2+, as estimated by the Baker soil test was 9.37?±?1.89, 13.1?±?1.96, 12.8?±?1.89, 11.9?±?2.00, and 11.6?±?1.52, respectively. Free metal ion activity was predicted by pH-dependent Freundlich equation (solubility model) as a function of pH, organic carbon, and extractable metal. Results indicate that solubility model as a function of pH, Walkley–Black carbon (WBC), and ethylenediaminetetraacetic acid (EDTA)-extractable metals could explain the variation in pZn2+, pCu2+, pNi2+, pCd2+, and pPb2+ to the extent of 59, 56, 46, 52, and 51 %, respectively. Predictability of the solubility model based on pH, KMnO4-oxidizable carbon, and diethylenetriaminepentaacetic acid-extractable or CaCl2-extractable metal was inferior compared to that based on EDTA-extractable metals and WBC. 相似文献
830.
J. L. F. Angeli T. H. Trevizani A. Ribeiro E. C. Machado R. C. L. Figueira B. Markert S. Fraenzle S. Wuenschmann 《Environmental monitoring and assessment》2013,185(10):8333-8342
Concentrations of arsenic and four additional trace elements (Cu, Cr, Ni, and Zn) were determined by inductively coupled plasma–optical emission spectrometry in the muscular tissue of the yellow catfish (Cathorops spixii) and the urutu catfish (Genidens genidens) from Paranaguá Estuarine Complex, Brazil (PEC). The PEC can be characterized by an environment of high ecological and economic importance in which preserved areas of rainforest and mangroves coexist with urban activities as ports and industries. The average concentrations (in milligram per kilogram dry weight) of elements in the muscle tissue of C. spixii are as follows: Zn (31), As (17), Cu (1.17), Cr (0.62), and Ni (0.28). Similar concentrations could be found in G. genidens with exception of As: Zn (36), As (4.78), Cu (1.14), Cr (0.51), and Ni (0.14). Fish from the geographic northern rural region (Guaraqueçaba–Benito) display higher As concentrations in the muscle tissues than fish found in the south-western (urban) part of the PEC. An international comparison of muscle tissue concentrations of trace elements in fish was made. Except for Ni in C. spixii, a tendency of decrease in element concentration with increasing size (age) of the fish could be observed. According to the National Health Surveillance Agency of Brazil, levels of Cr and As exceeded the permissible limits for seafood. An estimation of the provisional tolerable weekly intake of As was calculated with 109 % for C. spixii and with 29 % for G. genidens. 相似文献