全文获取类型
收费全文 | 90622篇 |
免费 | 1272篇 |
国内免费 | 1351篇 |
专业分类
安全科学 | 3814篇 |
废物处理 | 3290篇 |
环保管理 | 13972篇 |
综合类 | 21537篇 |
基础理论 | 26298篇 |
环境理论 | 74篇 |
污染及防治 | 14635篇 |
评价与监测 | 5386篇 |
社会与环境 | 3672篇 |
灾害及防治 | 567篇 |
出版年
2022年 | 839篇 |
2021年 | 840篇 |
2020年 | 719篇 |
2019年 | 875篇 |
2018年 | 1134篇 |
2017年 | 1180篇 |
2016年 | 2190篇 |
2015年 | 1862篇 |
2014年 | 2614篇 |
2013年 | 9308篇 |
2012年 | 2269篇 |
2011年 | 2575篇 |
2010年 | 3323篇 |
2009年 | 3461篇 |
2008年 | 2052篇 |
2007年 | 1910篇 |
2006年 | 2278篇 |
2005年 | 2242篇 |
2004年 | 2561篇 |
2003年 | 2380篇 |
2002年 | 1924篇 |
2001年 | 2182篇 |
2000年 | 1968篇 |
1999年 | 1496篇 |
1998年 | 1366篇 |
1997年 | 1359篇 |
1996年 | 1476篇 |
1995年 | 1576篇 |
1994年 | 1461篇 |
1993年 | 1320篇 |
1992年 | 1302篇 |
1991年 | 1276篇 |
1990年 | 1232篇 |
1989年 | 1188篇 |
1988年 | 1037篇 |
1987年 | 971篇 |
1986年 | 985篇 |
1985年 | 1066篇 |
1984年 | 1161篇 |
1983年 | 1160篇 |
1982年 | 1173篇 |
1981年 | 1095篇 |
1980年 | 942篇 |
1979年 | 925篇 |
1978年 | 817篇 |
1977年 | 716篇 |
1976年 | 637篇 |
1975年 | 603篇 |
1973年 | 633篇 |
1972年 | 637篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
871.
Lemly AD 《Environmental monitoring and assessment》2007,125(1-3):361-375
This paper gives step-by-step instructions for assessing aquatic selenium hazards associated with mining. The procedure was
developed to provide the U.S. Forest Service with a proactive capability for determining the risk of selenium pollution when
it reviews mine permit applications in accordance with the National Environmental Policy Act (NEPA). The procedural framework
is constructed in a decision-tree format in order to guide users through the various steps, provide a logical sequence for
completing individual tasks, and identify key decision points. There are five major components designed to gather information
on operational parameters of the proposed mine as well as key aspects of the physical, chemical, and biological environment
surrounding it — geological assessment, mine operation assessment, hydrological assessment, biological assessment, and hazard
assessment. Validation tests conducted at three mines where selenium pollution has occurred confirmed that the procedure will
accurately predict ecological risks. In each case, it correctly identified and quantified selenium hazard, and indicated the
steps needed to reduce this hazard to an acceptable level. By utilizing the procedure, NEPA workers can be confident in their
ability to understand the risk of aquatic selenium pollution and take appropriate action. Although the procedure was developed
for the Forest Service it should also be useful to other federal land management agencies that conduct NEPA assessments, as
well as regulatory agencies responsible for issuing coal mining permits under the authority of the Surface Mining Control
and Reclamation Act (SMCRA) and associated Section 401 water quality certification under the Clean Water Act. Mining companies
will also benefit from the application of this procedure because priority selenium sources can be identified in relation to
specific mine operating parameters. The procedure will reveal the point(s) at which there is a need to modify operating conditions
to meet environmental quality goals. By recognizing concerns early in the NEPA process, it may be possible for a mining company
to match operational parameters with environmental requirements, thereby increasing the likelihood that the permit application
will be approved. 相似文献
872.
McFarland MJ Olivas AC Atkins SG Kennedy RL Patel K 《Journal of the Air & Waste Management Association (1995)》2007,57(11):1317-1325
Maintenance of Department of Defense (DoD) weapon systems, conducting battlefield training exercises as well as meeting military construction and/or demolition schedules, invariably generate fugitive air emissions, many of which are visible. Although there is no codified federal method for quantifying fugitive emissions opacity, many state and local air regulatory agencies have instituted enforceable fugitive emission opacity standards at DoD facilities. The current study focused on comparing the performance of the digital opacity compliance system (DOCS) with U.S. Environment Protection Agency Method 9 (Method 9) certified human observers in quantifying the visible opacity associated with fugitive emissions produced using a commercial fog generator. By systematically repositioning both DOCS cameras and Method 9-certified observers during field testing, differences in method performance as a function of observational locations were documented. At both the 30- and 300-ft off-set distances, opacity levels reported by the DOCS technology and Method 9-certified smoke readers were found to be statistically different at the 99% confidence level. Alternatively, at the 90- and 150-ft off-set distances, results suggested that there was an insignificant difference at the 99% confidence level between the two methods. Comparing the magnitude of the each method's standard deviation suggested that, at the 30-ft off-set distance, the DOCS technology was consistently more precise than Method 9-certified readers regardless of the observer's downwind distance. However, at the 90, 150, and 300-ft off-set distances, method precision seemed to vary as a function of both off-set and downwind distance. The primary factor affecting the consistency in opacity measurements appeared to be the impact of ground-level air turbulence on fog plume dispersion and transport. Field observations demonstrated that localized wind shear played a critical and decisive role in how and to what extent fugitive emissions opacity could be determined, regardless of the method selected. 相似文献
873.
Heavy metal contamination in sediments of the Karasu spring was investigated in the presented study. In this respect, sediment
samples were collected from contaminant sites along the spring starting from the spring water manifestation site, base of
the Akkaya dam to the dam exit site. Heavy metal concentrations were determined by X-ray Fluorescence Spectrometer. Cobalt,
copper, arsenic, tin, nickel, zinc, cadmium, lead, aluminum, iron, titan, chromium and manganese contents of the Karasu creek
sediments are found as 18.30–69.00, 12.40–595.0 5.50–345.3, 5.80–15.1, 10.9–64.1, 28.90–103,300, 4.1–356.2, 7.70–37,840, 13,460–109,400,
11,740–62,900, 22.18–59.04, 41.70–369 and 12.09–3,480 mg/kg, respectively. Results indicate the presence of a contamination
in the Karasu creek. All the metal concentrations were found to be exceeding their acceptable limit values. Eutrophication
is developed in the Karasu creek and the Akkaya dam. It is thought that heavy metal accumulation in the creek is originated
from discharge from mine quarries, industrial and domestic wastes. Protection zones should be defined and all necessary measures
must be taken along the Karasu creek. 相似文献
874.
Houghton DC 《Environmental monitoring and assessment》2007,135(1-3):253-264
Over 300,000 caddisfly specimens representing 249 species were collected from nearly 250 sites throughout Minnesota during
2000 and 2001 to determine the effects of human disturbance on the composition of caddisfly trophic functional groups at the
landscape level. Canonical correspondence analysis determined that stream width was the most important variable influencing
functional group composition in regions of the state with relatively low disturbance, and that differences in the caddisfly
fauna between sizes of streams generally followed trends predicted by the river continuum concept. In regions of the state
with moderate disturbance, both stream width and the percentage of disturbed habitat upstream of a site were important variables
influencing functional group composition. In highly disturbed regions, no variables corresponded to changes in the composition
of caddisfly functional groups. Instead, ecosystems were homogeneous: fine-particle filtering collectors dominated in all
sizes of streams. The observed aquatic ecosystem homogenization is attributed mostly to input of fine-particle organic and
inorganic sediment from extensive agriculture. 相似文献
875.
Spalinger SM von Braun MC Petrosyan V von Lindern IH 《Environmental monitoring and assessment》2007,130(1-3):57-72
House dust has been identified as a major exposure medium for lead (Pb) in children. High levels of Pb in soil and house dust
have been recorded at the Bunker Hill Superfund Site (BHSS) in northern Idaho, an historic mining and smelting district. Soil
and dust remediation at the site was required; however, regional background soil and dust Pb levels had not been well characterized.
The objective of this survey was to determine background house dust Pb levels and to compare those levels with concentrations,
and dust and Pb loading rates measured at the BHSS. Soil and house dust samples were collected in five towns demographically
similar to the BHSS but unaffected by the mining industry. The background concentrations and loading rates were significantly
lower than those observed at the site. House age was a significant factor affecting background soil and house dust Pb concentrations
and loading rates. 相似文献
876.
One hundred forty seven samples of bovine milk were collected from 14 districts of Haryana, India during December 1998–February
1999 and analysed for the presence of organochlorine pesticide (OCPs) residues. ∑HCH, ∑DDT, ∑endosulfan and aldrin were detected
in 100%, 97%, 43% and 12% samples and with mean values of 0.0292, 0.0367, 0.0022 and 0.0036 μg/ml, respectively. Eight percent
samples exceeded the maximum residue limit (MRL) of 0.10 mg/kg as recommended by WHO for ∑HCH, 4% samples of 0.05 mg/kg for
α-HCH, 5% samples of 0.01 mg/kg for γ-HCH, 26% samples of 0.02 mg/kg for β-HCH as recommended by PFAA and 24% samples of 0.05 mg/kg
as recommended by FAO for ∑DDT. Concentrations of β-HCH and p,p′-DDE were more as compared to other isomers and metabolites
of HCH and DDT. 相似文献
877.
Current demand analysis methods do not formally cover the case of chronic deficits in quantity or quality of water and sanitation
services. These services include drinking water supply (DWS), wastewater and sewage treatment (WST), and municipal solid waste
management (MSW). Formal analysis of this case would, at minimum, define the deficit state and evaluate appropriate options
for reducing it. This paper proposes for a formal analytical model for municipal sanitation systems (MSS) that operate with
deficits in at least one of the constituent services of DWS, WST, or MSW. The model introduces definitions and notation for
describing the deficit state for conducting demand analysis on municipal sanitation systems. This model of demand analysis
for systems with chronic deficits will hereinafter be referred to as deficit analysis. A case study for Bacoor, Philippines is presented as an example. 相似文献
878.
Relation of waste generation and composition to socio-economic factors: a case study 总被引:3,自引:0,他引:3
Bandara NJ Hettiaratchi JP Wirasinghe SC Pilapiiya S 《Environmental monitoring and assessment》2007,135(1-3):31-39
To develop an effective waste management strategy for a given region, it is important to know the amount of waste generated
and the composition of the waste stream. Past research has shown that the amount of waste generated is proportional to the
population and the average mean living standards or the average income of the people. In addition, other factors may affect
the amount and composition of waste. These are climate, living habits, level of education, religious and cultural beliefs,
and social and public attitudes. This paper presents the findings of a study carried out in a suburban municipal area in Sri
Lanka to determine the solid waste generation rate and waste composition based on field surveys and to determine the related
socio-economic factors. A database was developed that included information on the quantity and composition of waste generated
in a sample of households in the study area over a time period. The collected data was analysed to relate waste generation
and composition data to various socio-economic factors. Over 400 sample households were selected for the study using a stratified
random sampling methodology based on municipal wards and property values. A technique that considers both the number of households
in a particular income group (property value range) and the standard deviation of property values within a given income group
was used to determine the appropriate sample size for each municipal ward. Through category and regression analyses, the quantities
of waste and waste composition were related to several socio-economic factors. The paper describes the basis for the sample
selection, the methodology adopted for data collection, the socio-economic parameters used for the analysis, and the relationships
developed from the analysis. 相似文献
879.
We present a hitherto unknown prey perception strategy in bats: Myotis nattereri (Vespertilionidae, Chiroptera) is able to perceive prey by echolocation within a few centimeters of echo-cluttering vegetation,
by using frequency-modulated search signals of very large bandwidth (up to 135 kHz). We describe the species’ search behavior
and echolocation repertoire from the field and from experiments in a flight tent. In the field, bats varied signal parameters
in relation to their distance from vegetation and usually flew close to vegetation. In the flight tent, M. nattereri detected and localized prey by echolocation alone as close as 5 cm from vegetation. Apparently, the bats were able to tolerate
some overlap between prey and clutter echoes. Passive prey cues (vision, olfaction, prey-generated sounds) were not used in
prey perception. The bats selected prey by size. The animals performed aerial catches and produced approach sequences typical
for aerial hawking bats, but were able to do so within a few centimeters of the substrate. M. nattereri thus has access to silent, suspended prey very close to vegetation (e.g., spiders, and caterpillars on threads).
Received: 29 September 1999 / Received in revised form: 12 February 2000 / Accepted: 12 February 2000 相似文献
880.
Characteristics that influence male reproductive success on a lek of Lethrinops c.f. parvidens (Teleostei: Cichlidae) 总被引:1,自引:1,他引:0
Sexual selection has long been proposed as a mechanism leading to the diverse cichlid (Teleostei: Cichlidae) fauna of Lake
Malawi, Africa. Many of the shallow-water, sand-dwelling, bower-building cichlid species are particularly well suited for
studies of sexual selection because they participate in leks. Since females in lekking systems appear to acquire only genetic
material from their mates, it has been suggested that leks are ideal systems to study female mate choice. The objectives of
the investigation were to examine Lethrinops c.f. parvidens male bower characteristics (i.e., bower size and location) as well as other male characteristics (i.e., length, gular color,
and duration on the lek) for their influence on male mating success as measured by the number of visits, circles, and eggs
laid by females. These measures are nested in that a visit by a female may or may not lead to circling, and circling by a
female may or may not lead to egg-laying. We found increased bower height and higher numbers of conspecific neighbors (analogous
to shallow-water, near-shore bower positions) to be positively, significantly associated with the number of visits by females.
The only significant correlate with the number of circles was visits, and similarly circles was the only significant correlate
with the number of eggs laid. The R
2 value for the egg-laying regression was quite low (19.8%) compared with visits (54.3%) and circling (78.9%), suggesting that
females may be using additional cues, that we failed to measure, when in close proximity to males or simply that a small proportion
of the females were ready to spawn. Both indirect selection and direct selection pressure due to egg predation may have influenced
female choice on the lek.
Received: 10 April 1999 / Received in revised form: 26 July 1999 / Accepted: 18 September 1999 相似文献