全文获取类型
收费全文 | 26078篇 |
免费 | 237篇 |
国内免费 | 258篇 |
专业分类
安全科学 | 740篇 |
废物处理 | 1211篇 |
环保管理 | 3485篇 |
综合类 | 3264篇 |
基础理论 | 7270篇 |
环境理论 | 6篇 |
污染及防治 | 6751篇 |
评价与监测 | 1976篇 |
社会与环境 | 1723篇 |
灾害及防治 | 147篇 |
出版年
2023年 | 103篇 |
2022年 | 235篇 |
2021年 | 247篇 |
2020年 | 168篇 |
2019年 | 216篇 |
2018年 | 478篇 |
2017年 | 480篇 |
2016年 | 788篇 |
2015年 | 461篇 |
2014年 | 645篇 |
2013年 | 2051篇 |
2012年 | 1154篇 |
2011年 | 1196篇 |
2010年 | 935篇 |
2009年 | 937篇 |
2008年 | 1058篇 |
2007年 | 1169篇 |
2006年 | 1048篇 |
2005年 | 1285篇 |
2004年 | 1485篇 |
2003年 | 1303篇 |
2002年 | 801篇 |
2001年 | 997篇 |
2000年 | 683篇 |
1999年 | 462篇 |
1998年 | 315篇 |
1997年 | 291篇 |
1996年 | 338篇 |
1995年 | 330篇 |
1994年 | 293篇 |
1993年 | 272篇 |
1992年 | 269篇 |
1991年 | 244篇 |
1990年 | 253篇 |
1989年 | 245篇 |
1988年 | 225篇 |
1987年 | 180篇 |
1986年 | 161篇 |
1985年 | 160篇 |
1984年 | 205篇 |
1983年 | 180篇 |
1982年 | 221篇 |
1981年 | 163篇 |
1980年 | 137篇 |
1979年 | 171篇 |
1978年 | 130篇 |
1977年 | 117篇 |
1976年 | 109篇 |
1975年 | 92篇 |
1974年 | 96篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Multi-objective, decision-based assessment of a water quality monitoring network in a river system 总被引:1,自引:0,他引:1
Water quality monitoring network design has historically tended to use experience, intuition and subjective judgement in locating monitoring stations. Better design procedures to optimize monitoring systems need to simultaneously identify significant planning objectives and consider a number of social, economic and environmental constraints. The consideration of multiple objectives may require further decision analysis to determine the preference weights associated with the objectives to aid in the decision-making process. This may require the application of an optimization study to extract such information from decision makers or experts and to evaluate the overall effectiveness of locating strategies. This paper assesses the optimal expansion and relocation strategies of a water quality monitoring network using a two-stage analysis. The first stage focuses on the information retrieval of preference weights with respect to the designated planning objectives. With the aid of a pre-emptive goal programming model, data analysis is applied to obtain the essential information from the questionnaire outputs. The second stage then utilizes a weighted multi-objective optimization approach to search for the optimal locating strategies of the monitoring stations in the river basin. Practical implementation is illustrated by a case study in the Kao-Ping River Basin, south Taiwan. 相似文献
122.
During the last 10–15 years heuristic methods have been developed for problems in optimal reserve selection. Unfortunately, there is no guarantee that heuristics will find optimal solutions. In recognizing this limitation, analysts have formulated reserve selection problems as set covering problems, for which matrix reduction and integer (0/1) programming can be used to find optimal solutions. In this paper we restate the set covering formulation and review solution techniques. A new 0/1 programming model, which is a generalization of the set covering model, is then presented and applied to a hypothetical reserve selection problem. Objectives of minimizing the number of sites selected and maximizing the number of species represented are addressed. Solutions which characterize the tradeoffs between these objectives provide a rich set of information for planners and decision makers. Applications of mathematical programming to related problems in land use planning and forestry are also discussed. 相似文献
123.
K. Stamatelatou G. Lyberatos C. Tsiligiannis S. Pavlou P. Pullammanappallil S.A. Svoronos 《Environmental Modeling and Assessment》1997,2(4):355-363
Anaerobic digester failure due to entry of inhibitors or sudden changes in the feed substrate concentration may be encompassed beneficially by applying optimal control theory. An almost proportional relationship between the dilution rate and the methane production rate leads to a simple suboptimal control law with only minor loss in performance, after the occurrence of the above mentioned events. 相似文献
124.
A simple,cost-effective multispecies toxicity test using organisms with a cosmopolitan distribution 总被引:4,自引:0,他引:4
John Cairns Jr. James R. Pratt B. R. Niederlehner P. V. McCormick 《Environmental monitoring and assessment》1986,6(3):207-220
Difficulties in making accurate, ecosystem-level predictions of environmental effects of chemicals, mixtures, and effluents based solely on the results of tests on single species have necessitated the development of more environmentally realistic, predictive testing methods. This paper describes a multispecies, community-level toxicity test based on the colonization of artificial substrates by microbial species. Tests examined the colonization of initially barren polyurethane foam artificial substrates by Protozoa from a species source colonized in a natural system. Differences in colonization were examined in microecosystems amended with low levels of cadmium, a very toxic heavy metal, and TFM, an organic biocide used against larval sea lamprey. Tests examined differences in colonization over 28 days. For cadmium, effect levels were estimated to be near 1 g 1–1, in the low range of effect levels determined from chronic single species tests. For TFM, effect levels were estimated to be between 1 and 10 ppm, overlapping the concentrations used in environmental applications. The colonization response, which depends on naked microbial cells reproducing and migrating through toxicant amended water to new substrates, is very sensitive. Tests based on colonization can be adapted to use species from a target receiving system or can use species from a designated natural source. Field validation of these tests can employ nearly identical methods to those used in laboratory studies to assess the accuracy of predictions based on test system data. 相似文献
125.
126.
G. L. Sia C. N. Ong S. E. Chia H. Y. Ong W. H. Phoon K. T. Tan 《Environmental monitoring and assessment》1991,19(1-3):401-411
This study was conducted to evaluate the usefulness of various biological parameters for monitoring of workers exposed to methyl ethyl ketone (MEK). Fifty male workers from a large magnetic videotape factory participated in this study. Personal air samples were collected using 3M organic vapor monitors and analysed for MEK by gas chromatography with flame ionisation detector (FID). 10 mL of urine; blood (1 mL) and exhaled air were also collected at the end of an 8-hour workshift. The headspace GC method was applied for measurement of urinary and blood MEK. MEK in expired air was analysed directly by using a GC/FID.The correlation coefficients (r) between environmental MEK and all other biological parameters measured show significant positive relationships. The r for environmental MEK and urine MEK was 0.84; for blood 0.73 and for breath 0.64. The correlation coefficients between blood and urine was 0.72; blood and breath was 0.88 and urine and breath 0.60. These findings suggest that measurements of unmetabolised MEK in blood, exhaled air and urine can be used for biological monitoring of MEK exposure. Nevertheless, laboratory methodological assessment is in favour of measuring urinary MEK as it is non-invasive and does not have to be analysed immediately after collection. 相似文献
127.
A pot culture experiment was conducted to evaluate the effect of different treatments of distillery wastewater, i.e. raw, treated, diluted and raw distillery wastewater mixed with domestic waste stabilization pond effluent (1:1) on populations of bacteria, fungi, actinomycetes and nitrogen fixing bacteria. The results indicated that raw wastewater decreased the population of bacteria, fungi and actinomycetes. The growth rates of Rhizobium and Azotobacter were also reduced after raw wastewater application. The toxic effect of raw wastewater was minimized when it was mixed with stabilization pond effluent (1:1), this was demonstrated by an increase in the populations of all the microorganisms studied. When a groundnut plant was irrigated with raw distillery wastewater, no fruits were produced and there was also less nodulation. This study indicates that raw distillery wastewater is very toxic to the soil microorganisms which are important in the soil ecosystem. 相似文献
128.
Rosqvist S Johannesson G Lindh CH Jönsson BA 《Journal of environmental monitoring : JEM》2000,2(2):155-160
Hexahydrophthalic anhydride (HHPA) and methylhexahydrophthalic anhydride (MHHPA) are two highly allergenic compounds used in the chemical industry. A method was developed for quantification of protein adducts of HHPA and MHHPA in human plasma. The plasma was dialysed and the anhydrides were hydrolysed from the proteins at mild acidic conditions. The released hexahydrophthalic acid (HHP acid) and methylhexahydrophthalic acid (MHHP acid) were purified by reversed solid phase extraction followed by derivatisation with pentafluorobenzyl bromide. The derivatives were analysed using GC-MS in negative ion chemical ionisation mode with ammonia as moderating gas. As internal standards, deuterium labelled HHP and MHHP acids were used. The detection limits were 0.06 pmol mL(-1) plasma for HHP acid and 0.03 pmol mL(-1) plasma for MHHP acid. The between-day precisions for HHP acid were 18% at 0.3 pmol mL(-1) and 8% at 4 pmol mL(-1). For MHHP acid, the precisions were 13% at 0.3 pmol mL(-1) and 9% at 4 pmol mL(-1). There were strong correlations (r=0.94 for HHPA and 0.99 for MHHPA) between total plasma protein adduct concentrations and serum albumin adduct levels. Workers exposed to time-weighted average air levels of HHPA between < 1 and 340 microg m(-3) and between 2 and 160 microg m(-3) for MHHPA had plasma adduct levels between the detection limits of the methods and 8.40 and 19.0 pmol mL(-1), respectively. 相似文献
129.
Hofschreuder P van der Meulen W Heeres P Slanina S 《Journal of environmental monitoring : JEM》1999,1(2):143-147
Passive samplers provide an excellent opportunity to perform indicative measurements or establish a dense network of measuring sites. A drawback compared with conventional active measuring methods is the larger spread of results. This variation can, to a large extent, be attributed to the influence of temperature, sampler geometry and wind on sampling results. A proper design of sampler geometry and optimum choice of draught shield can reduce the influence of wind velocity on a badge type sampler to less than 10%. Wire mesh screens prove to be inadequate in damping turbulence. Filters give good results. Attention should be paid to the size and isolation value of the walls of the sampler to prevent thermal updrafts occurring within the sampler. Tube type samplers are less influenced by wind, provided that turbulence is prevented from influencing diffusion within the sampler. 相似文献
130.
Effects of Roadway Crossings on Leaf Litter Processing and Invertebrate Assemblages in Small Streams
The effects of the Maine Turnpike (Interstate 95) on leaf litter processing were examined in five first- and second-order coastal plain streams in southern Maine, U.S.A. Invertebrate assemblages and red maple leaf softening and loss rates were compared at 53 stations arrayed upstream and downstream of the turnpike. Litter softening rate was not affected by the roadway. Litter loss rate was significantly faster at downstream stations (-0.0024 degree-day(-1)) than at upstream stations or at stations nearest the roadway, which were not different from each other (-0.0022 degree-day(-1)). Litter softening and loss rates were more strongly related to physical and chemical habitat variables than to shredder assemblage characteristics. Significant among-stream differences were observed in most community structural metrics and in biomass of important shredder taxa, but effects of the roadway were rarely consistent among streams. This is attributed in part to habitat variation, which was greater among streams than within streams. This study suggests that while the presence of the Maine Turnpike may influence stream water quality and habitat structure, the relatively subtle effects of roadway runoff and associated habitat modifications on stream ecosystem processes are masked by within- and among-stream variability in litter processing and leaf pack invertebrate assemblage structure. 相似文献