全文获取类型
收费全文 | 2871篇 |
免费 | 78篇 |
国内免费 | 25篇 |
专业分类
安全科学 | 126篇 |
废物处理 | 120篇 |
环保管理 | 843篇 |
综合类 | 280篇 |
基础理论 | 695篇 |
环境理论 | 1篇 |
污染及防治 | 619篇 |
评价与监测 | 166篇 |
社会与环境 | 87篇 |
灾害及防治 | 37篇 |
出版年
2023年 | 15篇 |
2022年 | 26篇 |
2021年 | 28篇 |
2020年 | 23篇 |
2019年 | 33篇 |
2018年 | 52篇 |
2017年 | 51篇 |
2016年 | 65篇 |
2015年 | 59篇 |
2014年 | 58篇 |
2013年 | 299篇 |
2012年 | 122篇 |
2011年 | 151篇 |
2010年 | 118篇 |
2009年 | 129篇 |
2008年 | 168篇 |
2007年 | 150篇 |
2006年 | 139篇 |
2005年 | 111篇 |
2004年 | 82篇 |
2003年 | 104篇 |
2002年 | 90篇 |
2001年 | 61篇 |
2000年 | 49篇 |
1999年 | 27篇 |
1998年 | 46篇 |
1997年 | 32篇 |
1996年 | 41篇 |
1995年 | 48篇 |
1994年 | 34篇 |
1993年 | 46篇 |
1992年 | 38篇 |
1991年 | 16篇 |
1990年 | 24篇 |
1989年 | 17篇 |
1988年 | 25篇 |
1987年 | 16篇 |
1986年 | 19篇 |
1985年 | 30篇 |
1984年 | 23篇 |
1983年 | 27篇 |
1982年 | 35篇 |
1981年 | 34篇 |
1980年 | 33篇 |
1979年 | 22篇 |
1978年 | 23篇 |
1977年 | 12篇 |
1976年 | 10篇 |
1974年 | 8篇 |
1972年 | 9篇 |
排序方式: 共有2974条查询结果,搜索用时 15 毫秒
41.
An Application of a Modified Ecological Footprint Method and Structural Path Analysis in a Comparative Institutional Study 总被引:1,自引:0,他引:1
This paper presents an application of a modified ecological footprint method, using a regional, disturbance-based approach. In contrast to conventional institutional ecological footprint calculations, energy and land use resulting from all upstream production processes are explored by employing an input-output framework. Ecological footprints are calculated for two research institutions: the School of Physics (SoP) at the University of Sydney, and the Sustainable Ecosystems (CSE) Department of the Commonwealth Scientific and Industrial Research Organisation. These are broken down further in terms of land disturbance and greenhouse gas emissions, and as a function of production layer. To enable the use of the results in policy formulation, the ecological footprints are decomposed into detailed contributing paths, which are ranked according to their importance, using structural path analysis. The paper demonstrates that a considerable proportion of impacts occur upstream in industrial production. Thus a significant result of the study is the weight of obscure paths in the total footprints and, therefore, the importance of conducting an holistic assessment in order to ensure all upstream contributions are captured in the final impact of the institution. 相似文献
42.
V. Krishna Prasad K.V.S. Badarinath H. Tsuruta S. Sudo S. Yonemura John Cardina Benjamin Stinner Richard Moore Deborah Stinner Casey Hoy 《The Environmentalist》2003,23(2):175-187
Forests and soils are a major sink of carbon, and land use changes can affect the magnitude of above ground and below ground carbon stores and the net flux of carbon between the land and the atmosphere. Studies on methods for examining the future consequences of changes in patterns of land use change and carbon flux gains importance, as they provide different options for CO2 mitigation strategies. In this study, a simulation approach combining Markov chain processes and carbon pools for forests and soils has been implemented to study the carbon flows over a period of time. Markov chains have been computed by converting the land use change and forestry data of India from 1997 to 1999 into a matrix of conditional probabilities reflecting the changes from one class at time t to another class time t+1. Results from Markov modeling suggested Indian forests as a potential sink for 0.94 Gt carbon, with an increase in dense forest area of about 75.93 Mha and decrease of about 3.4 Mha and 5.0 Mha in open and scrub forests, if similar land use changes that occurred during 1997–1999 would continue. The limiting probabilities suggested 34.27 percent as dense forest, 6.90 as open forest, 0.4 percent mangrove forest, 0.1 percent scrub and 58 percent as non-forest area. Although Indian forests are found to be a potential carbon sink, analysis of results from transition probabilities for different years till 2050 suggests that, the forests will continue to be a source of about 20.59 MtC to the atmosphere. The implications of these results in the context of increasing anthropogenic pressure on open and scrub forests and their contribution to carbon source from land use change and forestry sector are discussed. Some of the mitigation aspects to reduce greenhouse gas emissions from land use change and forestry sector in India are also reviewed in the study. 相似文献
43.
Richard Cowell James Tansey Marius Schwartz Peter Dickens Cliona Kimber 《Local Environment》1997,2(2):215-222
Making Cities Work: the role of local government in the urban environment. Richard Gilbert, Don Stevenson, Herbert Girardet & Richard Stren, 1996, London, Earthscan, 203pp. ISBN 1 85383 354 1, £13.95 pbk
Environmental Policy in an International Context, Vols 1-3: Perspectives, Conflicts and Prospects. P. Glasbergen & A. Blowers (Series Eds) London, Arnold
Rhetoric and Reality in Environmental Policy. M. Wintle & R. Reeve (Eds), 1994, Aldershot, Avebury Studies in Green Research, 154 pp. ISBN 1 85628 927 3
FutureNatural: Nature, Science, Culture. G. Roberston et al. (Eds) 1996, London, Routledge, ISBN 0415 070139, £40.00 hbk
Environmental Policy with Political Integration: the European Union and the United States. New horizons in environmental economics. John B. Braden, Henk Folmer & Thomas S. Ulen (Eds), 1996, Cheltenham, Elgar Publishing, 477 pp. ISBN 1 85898 217 0 相似文献
Environmental Policy in an International Context, Vols 1-3: Perspectives, Conflicts and Prospects. P. Glasbergen & A. Blowers (Series Eds) London, Arnold
Rhetoric and Reality in Environmental Policy. M. Wintle & R. Reeve (Eds), 1994, Aldershot, Avebury Studies in Green Research, 154 pp. ISBN 1 85628 927 3
FutureNatural: Nature, Science, Culture. G. Roberston et al. (Eds) 1996, London, Routledge, ISBN 0415 070139, £40.00 hbk
Environmental Policy with Political Integration: the European Union and the United States. New horizons in environmental economics. John B. Braden, Henk Folmer & Thomas S. Ulen (Eds), 1996, Cheltenham, Elgar Publishing, 477 pp. ISBN 1 85898 217 0 相似文献
44.
W. Richard Dubourg 《Natural resources forum》1997,21(3):191-200
Economic interpretations of sustainable development have concentrated on the need to maintain the aggregate capital stock intact, so as to ensure a constant stream of welfare through time. A sectoral approach to sustainability, in terms of this model, will be justified if substitution possibilities between that sector and the rest of the economy are limited. This assumption is examined in relation to the water sector, and it is found that further assumptions about substitution possibilities need to be made within the sector itself. Suggestions are offered as to how such substitutions might be made to advantage, which is contrasted to recent water management practices in England and Wales. It is argued that assumptions about substitution possibilities are in general overly restrictive, with the result that sustainability objectives fall short of optimum levels that could be achieved. 相似文献
45.
Liang Chen Syed H. Imam Sherald H. Gordon Richard V. Greene 《Journal of Polymers and the Environment》1997,5(2):111-117
Starch-PVOH cast films were prepared with and without crosslinking agent (hexamethoxymethylmelamine) in the absence of plasticizer.
Moisture absorption in films without crosslinking agent at a low relative humidity was similar to that of PVOH and increased
as the relative humidity increased. Films with crosslinking agent showed moisture absorption linearly proportional to the
relative humidity. Significant improvement in resistance to water disintegration for crosslinked starch-PVOH films was observed.
While the tensile strength decreased with increased relative humidity, crosslinking significantly improved the tensile strength.
Increased PVOH content improved elongation of films even when the relative humidity was 80% or higher. Biodegradation studies
revealed that the degradation rate was negatively correlated with the PVOH content in films and crosslinking generated more
converged degradation curves.
Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard
of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also
be suitable. 相似文献
46.
Steven N. Chillrud Richard F. Bopp James M. Ross Damon A. Chaky Sidney Hemming Edward L. Shuster H. James Simpson Frank Estabrooks 《Water, Air, & Soil Pollution: Focus》2004,4(2-3):469-482
Radionuclide, radiogenic lead isotope and trace metal analyses on fine-grained sediment cores collected along 160 km of the upper and tidal Hudson River were used to examine temporal trends of contaminant loadings and to develop radiogenic lead isotopes both as a stratigraphic tool and as tracers for resolving decadal particle transport fluxes. Very large inputs of Cd, Sb, Pb, and Cr are evident in the sediment record, potentially from a single manufacturing facility. The total range in radiogenic lead isotope ratios observed in well-dated cores collected about 24 km downstream of the plant is large (e.g., maximum difference in 206Pb/207Pb is 10%), characterized by four major shifts occurring in the 1950s, 1960s, 1970s and 1980s. The upper Hudson signals in Cd and radiogenic lead isotopes were still evident in sediments collected 160 km downstream in the tidal Hudson. The large magnitude and abrupt shifts in radiogenic lead isotope ratios as a function of depth provide sensitive temporal constraints that complement information derived from radionuclide analyses to significantly improve the precision of dating assignments. Application of a simple dilution model to data from paired cores suggests much larger sediment inputs in one section of the river than previously reported, suggesting particle influxes to the Hudson have been underestimated. 相似文献
47.
A solution containing 35SO4 2- and 3H2O was applied to four plots (5 × 5 m) in a boreal coniferous forest in the Laflamme Lake watershed, Québec, under two contrasting conditions: in summer (plots 1 and 2), and on the snowpack before snowmelt (plots 3 and 4). The transit of both these tracers in the soil solution was then followed through a network of soil lysimeters located at different depths. Four months after the summer application, 3H2O had infiltrated the whole soil profile at plot 1, while 35SO4 2- was only observed in the LFH and Bhf horizons. A 35SO4 2- budget calculated from mid-August to November indicated that 89 and 10.6% of the added 35SO4 2- was retained within the LFH and the Bhf layers, respectively. Fifteen months later, the added 35SO4 2- was distributed in the following proportions within the soil horizons: LFH (73.7%), Bhf (11.8%) and Bf (12.8%), for a total retention rate of 98.3%. The superficial penetration of 3H2O at plot 2 was indicative of a major lateral water movement that prevented the calculation of a 35SO4 2- budget. This situation also was observed at plot 4 during snowmelt. At plot 3, 3H2O moved freely through the soil profile and a significant fraction of the added 35SO4 2- reached the B horizons, where it was presumably adsorbed on aluminum (Al) and ferric (Fe) oxides. The 35SO4 2- budget for plot 3 from March to November indicated that 87% of the added 35SO4 2- was retained within the soil profile, with most being retained in the B horizons (LFH = 33.1%, Bhf = 33.1%, Bf = 20.8%). The contrasting retention patterns of 35SO4 2- within the soil profile following the summer addition and snowmelt likely was caused by the contrastingsoil temperatures and soil solution residence times within the differentsoil layers. The persistence of 35SO4 2- in the soil solution of the entire profile long after the initial tracer infiltration, and the relative temporal stability of specific activity of SO4 2-, point to the establishment of an isotopic equilibrium between the added 35SO4 and the active S-containing reservoirs within a given soil horizon. Overall, the results clearly illustrate the very strong potential for 35SO4 2- retention and recycling in forest soils. 相似文献
48.
Ali M Alhemood Ashraf M Genaidy Richard Shell Michael Gunn Christin Shoaf 《International journal of occupational safety and ergonomics》2004,10(4):303-318
In this study, a survey instrument was developed to measure safety climate. A review of the scientific literature as well as consultation with an expert panel was used to determine the survey's dimensions. Next, the survey was administered, first as a pilot study (n = 15) and then as a full scale study (n = 229), to employees of the City of Cincinnati Department of Public Works. The psychometric integrity of the survey was assessed according to validity, reliability and utility criteria. Results are presented and discussed. 相似文献
49.
This study addresses the behaviors of project managers under various conditions of cognitive and affective trust, and the implications for obtaining client loyalty. Theoretical foundations were drawn from interpersonal and interorganizational trust literature. A test of the proposed theoretical framework was conducted in a field setting utilizing a matched design of both project managers and their clients. The results show that reliable project performance positively impacted client loyalty intentions and service‐oriented OCBs positively impacted client secondary retention. An interaction showed that in low cognitive trust situations the project manager behavior of reliable project performance facilitated the obtainment of client loyalty intentions. Implications for research and practice are discussed. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
50.
Craig A. Evans Kevin S. McLeary George P. Partridge Richard S. Huebner 《Journal of the American Water Resources Association》2004,40(2):409-417
ABSTRACT: Computer programs that model the fate and transport of organic contaminants through porous media typically use Fick's first law to calculate vapor phase diffusion. Fick's first law, however, is limited to the case of a single, dilute species diffusing into a stagnant, high concentration, bulk vapor phase. When dealing with more than one diffusing species and at higher concentrations, the multicomponent coupling effects on vapor phase diffusion and advection of the various constituents become significant. VLEACH, a one‐dimensional finite difference model developed for the U.S. Environmental Protection Agency (USEPA), is typical of the models using Fick's first law to model vapor‐phase diffusion. The VLEACH model was modified to accommodate up to 10 components and to calculate the binary diffusion coefficients for each of the components based on molecular weight, molecular volume, temperature and pressure, and to address the coupling effects on multiple component vapor phase diffusion and its impact on ground water. The resulting model was renamed MC‐CHEMSOIL. At low vapor phase concentrations, MC‐CHEMSOIL predicts identical ground water impacts (dissolved phase loading) to those from VLEACH 2.2a. At higher vapor phase concentrations, however, the relative difference between the models exceeded 20 percent. 相似文献