全文获取类型
收费全文 | 33271篇 |
免费 | 387篇 |
国内免费 | 235篇 |
专业分类
安全科学 | 906篇 |
废物处理 | 1355篇 |
环保管理 | 4559篇 |
综合类 | 5895篇 |
基础理论 | 8982篇 |
环境理论 | 18篇 |
污染及防治 | 8246篇 |
评价与监测 | 2046篇 |
社会与环境 | 1644篇 |
灾害及防治 | 242篇 |
出版年
2022年 | 233篇 |
2021年 | 238篇 |
2019年 | 241篇 |
2018年 | 396篇 |
2017年 | 439篇 |
2016年 | 673篇 |
2015年 | 534篇 |
2014年 | 764篇 |
2013年 | 2683篇 |
2012年 | 968篇 |
2011年 | 1331篇 |
2010年 | 1086篇 |
2009年 | 1136篇 |
2008年 | 1304篇 |
2007年 | 1395篇 |
2006年 | 1282篇 |
2005年 | 1056篇 |
2004年 | 1020篇 |
2003年 | 1019篇 |
2002年 | 946篇 |
2001年 | 1167篇 |
2000年 | 898篇 |
1999年 | 532篇 |
1998年 | 416篇 |
1997年 | 431篇 |
1996年 | 440篇 |
1995年 | 493篇 |
1994年 | 464篇 |
1993年 | 447篇 |
1992年 | 441篇 |
1991年 | 431篇 |
1990年 | 440篇 |
1989年 | 408篇 |
1988年 | 372篇 |
1987年 | 347篇 |
1986年 | 346篇 |
1985年 | 328篇 |
1984年 | 369篇 |
1983年 | 354篇 |
1982年 | 379篇 |
1981年 | 348篇 |
1980年 | 304篇 |
1979年 | 321篇 |
1978年 | 267篇 |
1977年 | 248篇 |
1975年 | 199篇 |
1974年 | 244篇 |
1973年 | 230篇 |
1972年 | 231篇 |
1971年 | 214篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
841.
Ian D. Leith Lucy J. Sheppard David Fowler J. Neil Cape Matt Jones Alan Crossley Ken J. Hargreaves Y. Sim Tang Mark Theobald Mark R. Sutton 《Water, Air, & Soil Pollution: Focus》2005,4(6):207-218
Providing an accurate estimate of the dry component of N deposition to low N background, semi-natural habitats, such as bogs and upland moors dominated by Calluna vulgaris is difficult, but essential to relate nitrogen deposition to effects in these communities. To quantify the effects of NH3 inputs to moorland vegetation growing on a bog at a field scale, a field release NH3 fumigation system was established at Whim Moss (Scottish Borders) in 2002. Gaseous NH3 from a line source was released along of a 60 m transect, when meteorological conditions (wind speed >2.5 m s?1 and wind direction in the sector 180–215°) were met, thereby providing a profile of decreasing NH3 concentration with distance from the source. In a complementary study, using a NH3 flux chamber system, the relationships between NH3 concentrations and cuticular resistances were quantified for a range of NH3 concentrations and micrometeorological conditions for moorland vegetation. Cuticular resistances increased with NH3 concentration from 11 s m?1 at 3.0 μg m?3 to 30 s m?1 at 30 μg m?3. The NH3 concentration data and the concentration-dependent canopy resistance are used to calculate NH3 deposition taking into account leaf surface wetness. The implications of using an NH3 concentration-dependent cuticular resistance and the importance for refining critical loads are discussed. 相似文献
842.
R. Skinner P. Ineson W. K. Hicks H. E. Jones D. Sleep I. D. Leith L. J. Sheppard 《Water, Air, & Soil Pollution: Focus》2005,4(6):219-228
A field ammonia (NH3) release experiment and open top chambers containing moorland monoliths continuously fumigated with NH3 or sprayed with NH4Cl were used to assess the potential for using δ15N values in determining the area of influence around a point NH3 emission source. δ15N values are being increasingly used as environmental tracers and we tested the hypothesis that the δ15N signal from an NH3 emission source is observable in nearby vegetation. Using modified monitoring devices, atmospheric NH3 concentrations were found to decrease with distance from source, with δ15N values also reflecting this trend, producing a signal shift with changing concentration. Open top chamber studies of δ15N values of Calluna vulgaris (L.) Hull indicated a correlation with deposition treatments in current year shoots. Analysis of Calluna shoots from the NH3 release showed a similar trend of δ15N enrichment. Significant linear correlations between δ15N and percent N in plant material were found, both in the controlled conditions of the open top chambers and at the NH3 release site, illustrating the possible use of this technique in N deposition biomonitoring. 相似文献
843.
S. A. Power M. R. Ashmore A. C. Terry S. J. M. Caporn M. G. Pilkington D. B. Wilson C. G. Barker J. A. Carroll N. Cresswell E. R. Green G. W. HEIL 《Water, Air, & Soil Pollution: Focus》2005,4(6):259-267
The results from three long-term field manipulation studies of the impacts of increased nitrogen deposition (0–120 kg N ha?1 yr?1) on lowland and upland heathlands in the UK were compared, to test if common responses are observed. Consistent increases in Calluna foliar N content and decreases in litter C:N ratios were found across all sites, while increases in N leaching were not observed at any site over the range 0–80 kg ha?1 yr?1. However, the response of Calluna biomass did vary between sites, possibly reflecting site differences in nutrient status and management histories. Five versions of a simulation model of heathland responses to N were developed, each reflecting different assumptions about the fate and turnover of soil N. Model outputs supported the deduction from mass balance calculations at two of the field sites that N additions have resulted in an increase in immobilisation; the latter was needed to prevent the model overestimating measured N leaching. However, this version of the model significantly underestimated Calluna biomass. Model versions, which included uptake of organic N by Callunaand re-mobilisation of N from the soil organic store provided some improvement in the fit between modelled and field biomass data, but re-mobilisation also led to an overestimation of N leaching. Quantification of these processes and their response to increased N deposition are therefore critical to interpreting experimental data and predicting the long-term impacts of atmospheric deposition on heathlands and moorlands. 相似文献
844.
S. M. Smart M. R. Ashmore M. Hornung W. A. Scott D. A. Fowler U. Dragosits D. C. Howard M. A. Sutton D. Famulari 《Water, Air, & Soil Pollution: Focus》2005,4(6):269-278
Model estimates of NOy and NHx deposition across Britain for 1996 (5 km square resolution) were applied as explanatory variables to account for national-scale, fine-grained changes in plant species composition between 1990 and 1998. Plant species data were recorded from up to 27 fixed plots located within a stratified random sample of 596 1 km2. The response variable was a cover-weighted Ellenberg fertility score for each plot. Analyses were carried out separately for woodlands, semi-natural grasslands and heaths/bogs. Most of the variation in the botanical response variable occurred between plots within squares and so could not be explained by the model deposition data. NHx deposition estimates accounted for significant, but small components of between 1 km2 variation in the change in Ellenberg score in grasslands (5.6%) and heath/bogs (9.8%) but not woodlands. NOy deposition estimates were not significantly associated with vegetation change. Linear models provided the best fit and the slope of the relationship was lower for heath/bogs than grasslands. Further signal attribution at sub-kilometre square scales requires the development of fine-grained models of N deposition that can be generalised across regional sampling domains. 相似文献
845.
In 1995, the U.S. Environmental Protection Agency (US EPA) initiated the Brownfields Program to help local governments clean up and reuse hundreds of thousands of contaminated former factories and transportation and other commercial sites in cities and industrialized suburbs. By the end of 2002, the Brownfields Program had distributed grants of about $200,000 each to 436 local governments. Program grants have diffused through federal, state, regional, and local levels of government and private and not‐for profit organizations, and have reached into economically distressed neighborhoods. As expected, grant recipients disproportionately had a legacy of contaminated industrial sites and relatively large African American and/or Latino populations. But abandoned factories and environmental justice concerns do not completely explain the geographical distribution of recipients. Award winners tended to be larger cities with more capacity to compete for grants and were likely to be connected to sources of information about the grant opportunity and to decision makers. With a few exceptions, recipients consider the program to be highly successful at stimulating entrepreneurs to remediate and redevelop sites and, sometimes, surrounding neighborhoods. © 2005 Wiley Periodicals, Inc. 相似文献
846.
This study investigates the potential for perchlorate biodegradation in the sediments of the Las Vegas Wash area in Henderson, Nevada. The continuous transport of perchlorate from a contaminated seepage to the Las Vegas Wash, Lake Mead, and the Colorado River has resulted in considerable deposition of perchlorate along the sediments of the Las Vegas Wash. The contaminated sediments act as a distributed source of perchlorate, making efforts to stop the flow of perchlorate to the Colorado River very challenging. In this study, perchlorate‐ reducing bacteria were enumerated and microcosm tests were performed to investigate the role of indigenous microorganisms and the limitations to natural perchlorate biodegradation in the contaminated sediments. The results of microcosm tests revealed that, despite the high number of perchloratereducing bacteria present, natural perchlorate in the area appears to be limited by (1) high salinity levels, the presence of nitrate, and the low perchlorate concentrations present in the sediments and (2) an insufficient carbon source. However, the potential for in situ bioremediation of the sediments along the Wash area is considered to be high due to the presence of significant numbers of perchlorate‐ reducing bacteria and to the ease in which an additional carbon source could be provided to sustain nitrate and perchlorate biodegradation. The economics of this process are expected to be very favorable; however, detailed cost estimates, pilot‐scale testing, and permit applications are required before this concept can be applied. © 2005 Wiley Periodicals, Inc. 相似文献
847.
Public Perception of Flood Hazard in the Niger Delta,Nigeria 总被引:3,自引:0,他引:3
Summary Our study had the aim of understanding how floodplain dwellers regard the risk of flooding. About 500 questionnaires were
administered to landowners in the selected settlements in the study area using systematic random sampling. The results of
analysis show, among other things, that the population regards most important the causes of floods as heavy, prolonged rainfall
and river overflow. Nevertheless, they have little knowledge of the frequency of severe floods, and flood alleviation schemes.
Most flood victims do not get compensation or relief during flood disaster, and the reason why they remain in the study area
is influenced by their occupations, especially fishing, subsistence agriculture, and the presence of crude oil in the region
which has attracted many migrants who cannot afford the high cost of accommodation and are therefore forced to live in vulnerable
areas of the floodplain. Finally, the study concludes that flood control in the region needs the cooperation of government,
community efforts and an enlightenment programmes through environmental education and mass media. 相似文献
848.
Using resource-monitoring data from seven protected areas, the effectiveness of three campfire policies—campfire ban, designated campfires, and unregulated campfires—were assessed based on the number of fire sites and the amount of tree damage. Results indicate that unregulated campfire policies permitted substantial numbers of fire sites and tree damage in campsites, although fire bans did not eliminate or even substantially decrease these problems. A designated campfire policy was effective in decreasing number of fire sites, but little difference was found among policies regarding tree damage. Given the importance of campfires to visitor experiences, campfire prohibitions could be viewed as unnecessarily restrictive based on their limited success in preventing resource damage. Conclusions encourage protected-area managers to consider designated campfire policies and prohibitions on axes, hatchets, and saws to better meet resource protection and visitor experience mandates. 相似文献
849.
The paper explores how decisions made on animal feeding operations (AFOs) influence the management of manure and phosphorus. Variability among these decisions from operation to operation and from field to field can influence the validity of nutrient loss risk assessments. These assessments are based on assumptions that the decision outcomes regarding manure distribution will occur as they are planned. The discrepancy between planned versus actual outcomes in phosphorus management was explored on nine AFOs managing a contiguous set of 210 fields in south-central Wisconsin. A total of 2611 soil samples were collected and multiple interviews conducted to assign phosphorus index (PI) ratings to the fields. Spearman's rank correlation coefficients (r(S)) indicated that PI ratings were less sensitive to soil test phosphorus (STP) levels (r(S) = 0.378), universal soil loss equation (USLE) (r(S) = 0.261), ratings for chemical fertilizer application (r(S) = 0.185), and runoff class (r(S) = -0.089), and more sensitive to ratings for manure application (r(S) = 0.854). One-way ANOVA indicated that mean field STP levels were more homogenous than field PI ratings between AFOs. Kolmogorov-Smirnov (K-S) tests displayed several nonsignificant comparisons for cumulative distribution functions, S(x), of mean STP levels on AFO fields. On the other hand, the K-S tests of S(x) for PI ratings indicated that the majority of these S(x) functions were significantly different between AFOs at or greater than the 0.05 significance level. Interviews suggested multiple reasons for divergence between planned and actual outcomes in managing phosphorus, and that this divergence arises at the strategic, tactical, and operational levels of decision-making. 相似文献
850.
Sustainable land application: an overview 总被引:1,自引:0,他引:1
O'Connor GA Elliott HA Basta NT Bastian RK Pierzynski GM Sims RC Smith JE 《Journal of environmental quality》2005,34(1):7-17
Man has land-applied societal nonhazardous wastes for centuries as a means of disposal and to improve the soil via the recycling of nutrients and the addition of organic matter. Nonhazardous wastes include a vast array of materials, including manures, biosolids, composts, wastewater effluents, food-processing wastes, industrial by-products; these are collectively referred to herein as residuals. Because of economic restraints and environmental concerns about land-filling and incineration, interest in land application continues to grow. A major lesson that has been learned, however, is that the traditional definition of land application that emphasizes applying residuals to land in a manner that protects human and animal health, safeguards soil and water resources, and maintains long-term ecosystem quality is incomplete unless the earning of public trust in the practices is included. This overview provides an introduction to a subset of papers and posters presented at the conference, "Sustainable Land Application," held in Orlando, FL, in January 2004. The USEPA, USDA, and multiple national and state organizations with interest in, and/or responsibilities for, ensuring the sustainability of the practice sponsored the conference. The overriding conference objectives were to highlight significant developments in land treatment theory and practice, and to identify future research needs to address critical gaps in the knowledge base that must be addressed to ensure sustainable land application of residuals. 相似文献