全文获取类型
收费全文 | 851篇 |
免费 | 12篇 |
国内免费 | 4篇 |
专业分类
安全科学 | 62篇 |
废物处理 | 47篇 |
环保管理 | 159篇 |
综合类 | 77篇 |
基础理论 | 260篇 |
环境理论 | 1篇 |
污染及防治 | 168篇 |
评价与监测 | 64篇 |
社会与环境 | 24篇 |
灾害及防治 | 5篇 |
出版年
2023年 | 5篇 |
2022年 | 6篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 8篇 |
2017年 | 11篇 |
2016年 | 19篇 |
2015年 | 13篇 |
2014年 | 21篇 |
2013年 | 85篇 |
2012年 | 25篇 |
2011年 | 48篇 |
2010年 | 32篇 |
2009年 | 30篇 |
2008年 | 30篇 |
2007年 | 38篇 |
2006年 | 53篇 |
2005年 | 23篇 |
2004年 | 19篇 |
2003年 | 28篇 |
2002年 | 36篇 |
2001年 | 24篇 |
2000年 | 29篇 |
1999年 | 14篇 |
1998年 | 15篇 |
1997年 | 12篇 |
1996年 | 15篇 |
1995年 | 16篇 |
1994年 | 15篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1991年 | 9篇 |
1990年 | 13篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 12篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1969年 | 5篇 |
排序方式: 共有867条查询结果,搜索用时 15 毫秒
21.
Aneja VP Arya SP Kim DS Rumsey IC Arkinson HL Semunegus H Bajwa KS Dickey DA Stefanski LA Todd L Mottus K Robarge WP Williams CM 《Journal of the Air & Waste Management Association (1995)》2008,58(9):1130-1144
Ammonia (NH3) fluxes from waste treatment lagoons and barns at two conventional swine farms in eastern North Carolina were measured. The waste treatment lagoon data were analyzed to elucidate the temporal (seasonal and diurnal) variability and to derive regression relationships between NH3 flux and lagoon temperature, pH and ammonium content of the lagoon, and the most relevant meteorological parameters. NH3 fluxes were measured at various sampling locations on the lagoons by a flowthrough dynamic chamber system interfaced to an environmentally controlled mobile laboratory. Two sets of open-path Fourier transform infrared (FTIR) spectrometers were also used to measure NH3 concentrations for estimating NH3 emissions from the animal housing units (barns) at the lagoon and spray technology (LST) sites. Two different types of ventilation systems were used at the two farms. Moore farm used fan ventilation, and Stokes farm used natural ventilation. The early fall and winter season intensive measurement campaigns were conducted during September 9 to October 11, 2002 (lagoon temperature ranged from 21.2 to 33.6 degrees C) and January 6 to February 2, 2003 (lagoon temperature ranged from 1.7 to 12 degrees C), respectively. Significant differences in seasonal NH3 fluxes from the waste treatment lagoons were found at both farms. Typical diurnal variation of NH3 flux with its maximum value in the afternoon was observed during both experimental periods. Exponentially increasing flux with increasing surface lagoon temperature was observed, and a linear regression relationship between logarithm of NH3 flux and lagoon surface temperature (T1) was obtained. Correlations between lagoon NH3 flux and chemical parameters, such as pH, total Kjeldahl nitrogen (TKN), and total ammoniacal nitrogen (TAN) were found to be statistically insignificant or weak. In addition to lagoon surface temperature, the difference (D) between air temperature and the lagoon surface temperature was also found to influence the NH3 flux, especially when D > 0 (i.e., air hotter than lagoon). This hot-air effect is included in the statistical-observational model obtained in this study, which was used further in the companion study (Part II), to compare the emissions from potential environmental superior technologies to evaluate the effectiveness of each technology. 相似文献
22.
Implications of urine-to-feces ratio in the thermophilic anaerobic digestion of swine waste. 总被引:1,自引:0,他引:1
Thermophilic anaerobic digestion of swine manure represents a potential waste treatment technology to address environmental concerns, such as odor emissions and removal of pathogenic microorganisms. However, there are concerns relative to the stability of this process when swine manure is the sole substrate. In this study, the potential of biogas production from swine manure as the sole substrate under thermophilic (50 degrees C) conditions was investigated in the laboratory, to determine whether separation of urine and feces as part of the waste collection process would benefit anaerobic digestion. Effluent from a continuously stirred tank reactor was used as the inoculum for batch tests, in which the substrate contained three different concentrations of urine (urine-free, as-excreted urine-to-feces ratio and double the as-excreted urine-to-feces ratio). Inocula were acclimated to these same urine-to-feces ratios to determine methane production. Results show that both urine-free and as-excreted substrates were not inhibitory to anaerobic inocula. Anaerobic microorganisms can be readily acclimated to substrate with double the as-excreted urine concentration, which contained nitrogen concentrations up to 7.20 g/L. Cumulative methane production reached similar levels in the batch tests, regardless of the substrate urine concentration. 相似文献
23.
The influence of temperature on the levels of PCDD and PCDF remaining in, and desorbed from, a municipal solid waste incinerator flyash was investigated by heating the ash to between 200 and 400 degrees C under a simulated flue gas for four days reaction time. Considerable desorption of PCDD/PCDF from the flyash was seen at 275 degrees C and above. Maximum desorption occurred at 350 degrees C, with the equivalent of nearly eight times the total PCDD/PCDF concentration of the original flyash being lost to the vapour phase per unit mass of initial flyash. The I-TEQ value of the desorbed PCDD/PCDF was considerable, being over fourteen times that of the original flyash at 325 degrees C. The results indicate that formation of PCDD/PCDF on flyash deposits in the post-combustion plant of incinerators can result in the release of significant amounts of PCDD/PCDF to the flue gas stream. 相似文献
24.
The influence of temperature on the PCDD and PCDF isomer profiles of a municipal waste incinerator flyash and the PCDD/PCDF desorbed from the ash under an inert atmosphere was investigated using a bench-scale reactor. Exposure to temperatures of 250 degrees C and above resulted in significant changes in the distribution of isomers within most dioxin and furan congener groups. The PCDD content tended to become more evenly distributed across the range of isomers than was the case for the raw flyash, while the PCDF content became concentrated across a relatively lower number of isomers. In most cases the desorbed PCDD/PCDF were mainly mono- to tri-chlorinated, and hence had a relatively low I-TEQ value. The isomer profiles of the desorbed species were also influenced by temperature. There were some significant differences between the PCDF isomer profiles of the desorbed species and those of the treated flyashes under the same conditions, but no clear differences between the PCDD isomer profiles. 相似文献
25.
Sather ME Slonecker ET Mathew J Daughtrey H Williams DD 《Environmental monitoring and assessment》2007,124(1-3):211-221
Nitrogen Dioxide (NO2) is a common urban air pollutant that results from the combustion of fossil fuels. It causes serious human health effects,
is a precursor to the formation of ground level ozone, another serious air pollutant, and is one of the six criteria air pollutants
established by the United States (U.S.) Clean Air Act (CAA). Ogawa Passive Sampling Devices (PSDs) for NO2 were collocated and operated at six NO2 Federal Reference Method (FRM) monitor locations in the El Paso, Texas area for the 2004 calendar year. Passive samples were
taken at 2-week, 3-week, and 4-week intervals and compared against the continuously operating FRM monitors. Results showed
that the collective NO2 annual arithmetic mean for all passive monitors was identical to the NO2 mean for all FRM monitors. Of the individual locations, three passive annual NO2 means were identical to their corresponding FRM means, and three passive annual NO2 means differed from their corresponding FRM means by only one part per billion (ppb). Linear correlation analysis between
all readings of the individual NO2 PSDs and FRM values showed an average absolute difference of 1.2 ppb with an r
2 of 0.95. Paired comparison between high and low concentration annual NO2 sites, seasonal considerations, and interlab quality control comparisons all showed excellent results. The ease of deployment,
reliability, and the cost-savings that can be realized with NO2 PSDs could make them an attractive alternative to FRM monitors for screening purposes, and even possibly an equivalent method
for annual NO2 monitoring. More tests of the Ogawa NO2 PSD are recommended for different ecosystem and climate regimes. 相似文献
26.
The annual epidemic spawning period of a Scottish population of Arenicola marina (L.) has been recorded over a period of 13 yr. This population spawns between mid-October and mid-November in a discrete
spawning event over a period of 4 to 5 d. Endocrine manipulation experiments showed that spawning is induced in females only
if sufficient titres of PMH (prostomial maturation hormone) are present in the prostomia. These levels are attained during
the 2 to 3 wk prior to the natural spawning date. The East Sands, St. Andrews population always spawns during periods of spring
tides regardless of tidal amplitude or whether they are full- or new-moon tides. Meteorological data, including sea-temperature
data were collected for each year, and correlation of the environmental data with spawning time was attempted. Correlation
of spawning times with weather patterns showed that mean daily air pressures were significantly higher during the spawning
period than from September to November as a whole. Evidence also suggests that a reduction in sea temperature is required
prior to spawning. A significant moderate negative correlation was found between May to July air temperatures and spawning
date, suggesting that higher May to July temperatures may induce early spawning. Daily rainfall and wind speed were also lower
during the spawning period, but not significantly so. These results indicate that air pressure (or changes therein) may act
as a final spawning cue, and the advantages of this are discussed in relation to fertilization success. A model of the interplay
between environmental parameters and the endocrine mechanisms controlling the induction of spawning is proposed. Higher than
average summer temperatures may advance gametogenesis to bring the population into a state of maturity (full-size oocytes,
well-developed sperm morulae), and may also advance spawning time. Once the population has completed gametogenesis, a drop
in sea temperature is then required to trigger an increase in endocrine titres within the prostomium, without which spawning
cannot be induced by prostomial injection. The population spawns on spring tides; however a lack of clement weather coinciding
with the spring tide will result in population-wide spawning being aborted, as in 1996. Clement weather (high pressure, low
rainfall and wind speed) in conjunction with spring tides permits spawning to proceed to completion.
Received: 21 June 1999 / Accepted: 25 January 2000 相似文献
27.
28.
Forage-based livestock systems have been implicated as major contributors to deteriorating water quality, particularly for phosphorus (P) from commercial fertilizers and manures affecting surface and ground water quality. Little information exists regarding possible magnitudes of nutrient losses from pastures that are managed for both grazing and hay production and how these might impact adjacent bodies of water. We examined the changes that have occurred in soil fertility levels of rhizoma peanut (Arachis glabrata Benth.)-based beef cattle pastures (n = 4) in Florida from 1988 to 2002. These pastures were managed for grazing in spring followed by haying in late summer and were fertilized annually with P (39 kg P2O5 ha(-1)) and K (68 kg K2O ha(-1)). Additionally, we investigated trends in water quality parameters and trophic state index (TSI) of lakes (n = 3) associated with beef cattle operations from 1993 to 2002. Overall, there was no spatial or temporal buildup of soil P and other crop nutrients despite the annual application of fertilizers and daily in-field loading of animal waste. In fact, soil fertility levels showed a declining trend for crop nutrient levels, especially soil P (y = 146.57 - 8.14 x year; r2= 0.75), even though the fields had a history of P fertilization and the cattle were rotated into the legume fields. Our results indicate that when nutrients are not applied in excess, cow-calf systems are slight exporters of P, K, Ca, and Mg through removal of cut hay. Water quality in lakes associated with cattle production was "good" (30-46 TSI) based on the Florida Water Quality Standard. These findings indicate that properly managed livestock operations may not be major contributors to excess loads of nutrients (especially P) in surface water. 相似文献
29.
Jianjun Niu Pat E. Rasmussen Amanda Wheeler Ron Williams Marc Chénier 《Atmospheric environment (Oxford, England : 1994)》2010,44(2):235-245
Factors and sources affecting measurement uncertainty associated with monitoring metals in airborne particulate matter (PM) were investigated as part of the Windsor, Ontario Exposure Assessment Study (WOEAS). The assessment was made using co-located duplicate samples and a comparison of two analytical approaches: ED-XRF and ICP-MS. Sampling variability was estimated using relative percent difference (RPD) of co-located duplicate samples. The comparison of ICP-MS and ED-XRF results yields very good correlations (R2 ≥ 0.7) for elements present at concentrations that pass both ICP-MS and ED-XRF detection limits (e.g. Fe, Mn, Zn, Pb and Cu). PM concentration ranges (median, sample number) of 24-h indoor PM10 and personal PM10 filters, and outdoor PM2.5 filters were determined to be 2.2–40.7 (11.0, n = 48) μg m?3, 8.0–48.3 (11.9, n = 48) μg m?3, and 17.1–42.3 (21.6, n = 18) μg m?3, respectively. The gravimetric analytical results reveal that the variations in PM mass measurements for same-day sampling are insignificant compared to temporal or spatial variations: 92%, 100% and 96% of indoor, outdoor and personal duplicate samples, respectively, pass the quality criteria (RPD ≤ 20%). Uncertainties associated with ED-XRF elemental measurements of S, Ca, Mn, Fe and Zn for 24-h filter samples are low: 78%–100% of the duplicate samples passed the quality criteria. In the case of 24-h filter samples using ICP-MS, more elements passed the quality criteria due to the lower detection limits. These were: Li, Na, K, Ca, Si, Al, V, Fe, Mn, Co, Cu, Mo, Ag, Zn, Pb, As, Mg, Sb, Sn, Sr, Th, Ti, Tl, and U. Low air concentrations of metals (near or below instrumental detection limits) and/or inadvertent introduction of metal contamination are the main causes for excluding elements based on the pass/fail criteria. Uncertainty associated with elemental measurements must be assessed on an element-by-element basis. 相似文献
30.
Rachel F. Brummel Kristen C. Nelson Stephanie Grayzeck Souter Pamela J. Jakes Daniel R. Williams 《Journal of Environmental Planning and Management》2010,53(6):681-699
Policies such as the US Healthy Forests Restoration Act (HFRA) mandate collaboration in planning to create benefits such as social learning and shared understanding among partners. However, some question the ability of top-down policy to foster successful local collaboration. Through in-depth interviews and document analysis, this paper investigates social learning and transformative learning in three case studies of Community Wildfire Protection Planning (CWPP), a policy-mandated collaboration under HFRA. Not all CWPP groups engaged in social learning. Those that did learned most about organisational priorities and values through communicative learning. Few participants gained new skills or knowledge through instrumental learning. CWPP groups had to commit to learning, but the design of the collaborative-mandate influenced the type of learning that was most likely to occur. This research suggests a potential role for top-down policy in setting the structural context for learning at the local level, but also confirms the importance of collaborative context and process in fostering social learning. 相似文献