全文获取类型
收费全文 | 2191篇 |
免费 | 265篇 |
国内免费 | 766篇 |
专业分类
安全科学 | 227篇 |
废物处理 | 92篇 |
环保管理 | 781篇 |
综合类 | 1184篇 |
基础理论 | 342篇 |
污染及防治 | 292篇 |
评价与监测 | 229篇 |
社会与环境 | 45篇 |
灾害及防治 | 30篇 |
出版年
2024年 | 5篇 |
2023年 | 98篇 |
2022年 | 127篇 |
2021年 | 148篇 |
2020年 | 136篇 |
2019年 | 123篇 |
2018年 | 76篇 |
2017年 | 132篇 |
2016年 | 93篇 |
2015年 | 114篇 |
2014年 | 119篇 |
2013年 | 149篇 |
2012年 | 134篇 |
2011年 | 156篇 |
2010年 | 100篇 |
2009年 | 166篇 |
2008年 | 101篇 |
2007年 | 128篇 |
2006年 | 123篇 |
2005年 | 114篇 |
2004年 | 80篇 |
2003年 | 100篇 |
2002年 | 83篇 |
2001年 | 74篇 |
2000年 | 92篇 |
1999年 | 72篇 |
1998年 | 48篇 |
1997年 | 31篇 |
1996年 | 48篇 |
1995年 | 35篇 |
1994年 | 26篇 |
1993年 | 19篇 |
1992年 | 16篇 |
1991年 | 11篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 4篇 |
1974年 | 2篇 |
1970年 | 2篇 |
排序方式: 共有3222条查询结果,搜索用时 656 毫秒
981.
Stocki TJ Blanchard X D'Amours R Ungar RK Fontaine JP Sohier M Bean M Taffary T Racine J Tracy BL Brachet G Jean M Meyerhof D 《Journal of environmental radioactivity》2005,80(3):305-326
In preparation for verification of the Comprehensive Nuclear-Test-Ban-Treaty, automated radioxenon monitoring is performed in two distinctive environments: Ottawa and Tahiti. These sites are monitored with SPALAX (Systeme de Prelevement d'air Automatique en Ligne avec l'Analyse des radioXenons) technology, which automatically extracts radioxenon from the atmosphere and measures the activity concentrations of (131m,133m,133,135)Xe. The resulting isotopic concentrations can be useful to discern nuclear explosions from nuclear industry xenon emissions. Ambient radon background, which may adversely impact analyser sensitivity, is discussed. Upper concentration limits are reported for the apparently radioxenon free Tahiti environment. Ottawa has a complex radioxenon background due to proximity to nuclear reactors and medical isotope facilities. Meteorological models suggest that, depending on the wind direction, the radioxenon detected in Ottawa can be characteristic of the normal radioxenon background in the Eastern United States, Europe, and Japan or distinctive due to medical isotope production. 相似文献
982.
983.
Spatial proximity of emissions sources to receptors may affect sensitivity to potential adverse human health effects. This research investigates whether receptor sensitivity to the location of emission sources can be utilized efficiently to minimize health risk in selecting sites for industrial enterprises, thermal electric stations, etc. A sensitivity function that is independent of the location of pre-existing emission sources is derived and applied to Minsk, Belarus. The function estimates exposures based on weather and climatic conditions as well as the distribution of population density at a given locality. Arraying prospective sites based on their sensitivity function magnitude provides a technique for minimizing health risk based on receptor sensitivity to the spatial proximity of atmospheric emissions sources. 相似文献
984.
An experimental speciation scheme consisting of ultra-filtration(1 kD), cation and anion exchange has been developed. Parallel calculations of the ion balances are performed using the computerroutine MINTEQA2. The experimental and computed ion balances suffer from non-equilibrium conditions, incalculability of metal-binding colloids or sub-colloids, inaccurate Eh measurements and analytical errors. In most samples colloidal or sub-colloidal structures of Fe oxy-hydroxides and/or gypsum influence the behavior of many trace elements. The comparison of theory and experiment has to be restricted to acid waters (pH < 5) where colloids (1–450 nm) and non-filterable colloids or sub-colloids (<1 nm) play a minor role. Yet, only a few transition metals such as Mn, Fe, Co, Ni, Cu, Zn, or Cd remain more or less free of colloidal influence in low pH waters. The effect of DOC on Al may be estimated by model substances like citrate. 相似文献
985.
The Cache River of southernmost Illinois is used as a case study for developing and demonstrating an approach to quantitatively
link (1) national agricultural policy and global agricultural markets, (2) landowner's decisions on land use, (3) spatial
patterns of land use at a watershed scale, and (4) hydrologic impacts, thus providing a basis to predict, under a certain
set of circumstances, the environmental consequences of economic and political decisions made at larger spatial scales. The
heart of the analysis is an estimation, using logistic regression, of the affect of crop prices and Conservation Reserve Program
(CRP) rental rates on farmland owner's decisions whether to reenroll in the CRP or return to crop production. This analysis
shows that reasonable ranges for crop prices (80%–150% of 1985–1995 values) and CRP rental rates (0–125% of 1985–1995 rates)
result in a range of 3%–92% of CRP lands being returned to crop production, with crop prices having a slightly greater effect
than CRP rental rates. Four crop price/CRP rental rate scenarios are used to display resulting land-use patterns, and their
effect on sediment loads, a critical environmental quality parameter in this case, using the agricultural non point source
(AGNPS) model. These scenarios demonstrate the importance of spatial pattern of land uses on hydrological and ecological processes
within watersheds. The approach developed can be adapted for use by local governments and watershed associations whose goals
are to improve watershed resources and environmental quality. 相似文献
986.
The dry deposition of ozone to aconiferous forest in northeastern Bavaria(southern Germany) was quantified during 1999with both the eddy correlation method and a bigleaf model. The model included parameterizationsof the atmospheric transfer resistances fromdirect measurements, stomatal resistance from aplant ecological model, and an estimation of thecuticle resistance as function of leaf wetness.Early in the season, the measured and themodelled deposition fluxes were in goodagreement, although the modelled fluxes tended tounderestimate the measured ones. Thisunderestimation was more pronounced in the latesummer, when high nocturnal fluxes werefrequently measured. The model parameterizationof the cuticle and the stomatal resistances didnot allow for such high fluxes. In these cases,the 24 hour average of the measured fluxes wereup to 4.5 times higher than the modelled ones.The reasons for these large discrepancies remainunknown. However, assigning the unaccounted partof the deposition to a nonstomatal surfacedeposition pathway, a new parameterization of therespective resistance yielded an average value of300 s m-1. It exhibited a decreasing trendthrough the vegetation period. 相似文献
987.
An inventory of volatile organic compound (VOC) and nitrogen oxides (NOx) emissions is an important tool for the management of ground-level ozone pollution. This paper has two broad aims: it illustrates the potential of a geographic information system (GIS) for enhancing an existing spatially-aggregated, anthropogenic emissions inventory (EI) for Tucson, AZ, and it discusses the ozone-specific management implications of the resulting spatially-disaggregated EI. The main GIS-related methods include calculating emissions for specific features, spatially disaggregating region-wide emissions totals for area sources, and adding emissions from various point sources. In addition, temporal allocation factors enable the addition of a multi-temporal component to the inventory. The resulting inventory reveals that on-road motor vehicles account for approximately 50% of VOC and NOx emissions annually. On-road motor vehicles and residential wood combustion are the largest VOC sources in the summer and winter months, respectively. On-road motor vehicles are always the largest NOx sources. The most noticeable weekday vs. weekend VOC emissions differences are triggered by increased residential wood combustion and increased lawn and garden equipment use on weekends. Concerning the EI's uncertainties and errors, on-road mobile, construction equipment, and lawn and garden equipment are identified as sources in the most need of further investigation. Overall, the EIs spatial component increases its utility as a management tool, which might involve visualization-driven analyses and air quality modeling. 相似文献
988.
The successful management of atmospheric pollution is best achieved when the benefits of controls can be clearly demonstrated to those who the controls affect. There is a need to demonstrate to a population that change will benefit the social and biophysical aspects of that population’s environment as a whole. This paper suggests that policy-makers need to demonstrate clearly the advantages of a change in behaviour for the local environment while concurrently minimising the life-style costs of the people whose co-operation is needed to bring that change about. This requires an improved understanding of the activities affected and the message and media by which environmental benefits can be communicated in the light of that understanding.Using the example of tropospheric ozone, this paper argues that air-quality management requires close regional co-ordination which can facilitate the establishment and implementation of local policy options. The ability of the UK National Air Quality Strategy to achieve this in its present form is discussed and the existence of a strategic gap between the current approach to air-quality management and the major issues surrounding air quality considered. 相似文献
989.
Alan E. Haberstock Henry G. Nichols Mark P. DesMeules Jed Wright Jon M. Christensen Daniel H. Hudnut 《Journal of the American Water Resources Association》2000,36(6):1271-1286
ABSTRACT: Successful restoration of declining anadromous species is dependent upon effective riparian buffer zone management. Natural resource managers, policy developers and local conservation groups require science‐based information concerning the width at which a given buffer will be effective for its stated purpose. This paper summarizes a method developed in 1999 to determine effective riparian buffer widths for Atlantic salmon habitat protection as part of the Atlantic Salmon Conservation Plan for Seven Maine Rivers. A major assumption of the method is that no two buffers are alike with respect to their effectiveness and that various buffer characteristics dictate the required width for a given level of effectiveness. The method uses a predictive model that generates suggested riparian buffer widths as a function of specific, measurable buffer characteristics (such as slope, soil characteristics, and plant community structure and density) that affect buffer function. The method utilizes a variable‐width, two‐zone approach and specifies land uses that are consistent with desired buffer function within the two zones. 相似文献
990.
Glenn E. Moglen 《Journal of the American Water Resources Association》2000,36(6):1391-1400
ABSTRACT: The NRCS curve number approach to runoff estimation has traditionally been to average or “lump” spatial variability into a single number for purposes of expediency and simplicity in calculations. In contrast, the weighted runoff curve number approach, which handles each individual pixel within the watershed separately, tends to result in larger estimates of runoff than the lumped approach. This work proposes further enhancements that consider not only spatial variability, but also the orientation of this variability with respect to the flow aggregation pattern of the drainage network. Results show that the proposed enhancements lead to much reduced estimates of runoff production. A revised model that considers overland flow lengths, consistent with existing NRCS concepts is proposed, which leads to only mildly reduced runoff estimates. Although more physically‐based, this revised model, which accounts directly for spatially distributed curve numbers and flow aggregation, leads to essentially the same results as the original, lumped runoff model when applied to three study watersheds. Philosophical issues and implications concerning the appropriateness of attempting to disaggregate lumped models are discussed. 相似文献