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101.
102.
We modeled the impact of haze radiative effects on precipitation in North China.
Shortwave heating induced by haze radiative effects would reduce heavy rainfalls.
Convection was the key factor that whether precipitation was enhanced or suppressed.
Precipitation was often suppressed where CAPE, RH and updraft velocities were high.
The impact of haze radiative effect on summertime 24-h convective precipitation over North China was investigated using WRF model (version 3.3) through model sensitivity studies between scenarios with and without aerosol radiative effects. The haze radiative effect was represented by incorporating an idealized aerosol optical profile, with AOD values around 1, derived from the aircraft measurement into the WRF shortwave scheme. We found that the shortwave heating induced by aerosol radiative effects would significantly reduce heavy rainfalls, although its effect on the post-frontal localized thunderstorm precipitation was more diverse. To capture the key factors that determine whether precipitation is enhanced or suppressed, model grids with 24-h precipitation difference between the two scenarios exceeding certain threshold (>30 mm or<-30 mm) were separated into two sets. Analyses of key meteorological variables between the enhanced and suppressed regimes suggested that atmospheric convection was the most important factor that determined whether precipitation was enhanced or suppressed during summertime over North China. The convection was stronger over places with precipitation enhancement over 30 mm. Haze weakened the convection over places with precipitation suppression exceeding 30 mm and caused less water vapor to rise to a higher level and thus further suppressed precipitation. The suppression of precipitation was often accompanied with relatively high convective available potential energy (CAPE), relative humidity (RH) and updraft velocities. 相似文献
103.
J. Ovadnevaite D. Ceburnis K. Plauskaite-Sukiene R. Modini R. Dupuy I. Rimselyte M. Ramonet K. Kvietkus Z. Ristovski H. Berresheim C.D. O'Dowd 《Atmospheric environment (Oxford, England : 1994)》2009,43(32):4968-4974
High time resolution aerosol mass spectrometry measurements were conducted during a field campaign at Mace Head Research Station, Ireland, in June 2007. Observations on one particular day of the campaign clearly indicated advection of aerosol from volcanoes and desert plains in Iceland which could be traced with NOAA Hysplit air mass back trajectories and satellite images. In conjunction with this event, elevated levels of sulphate and light absorbing particles were encountered at Mace Head. While sulphate concentration was continuously increasing, nitrate levels remained low indicating no significant contribution from anthropogenic pollutants. Sulphate concentration increased about 3.8 μg m−3 in comparison with the background conditions. Corresponding sulphur flux from volcanic emissions was estimated to about 0.3 TgS yr−1, suggesting that a large amount of sulphur released from Icelandic volcanoes may be distributed over distances larger than 1000 km. Overall, our results corroborate that transport of volcanogenic sulphate and dust particles can significantly change the chemical composition, size distribution, and optical properties of aerosol over the North Atlantic Ocean and should be considered accordingly by regional climate models. 相似文献
104.
Georgina C. Andrada Gustavo G. Palancar Beatriz M. Toselli 《Atmospheric environment (Oxford, England : 1994)》2008,42(24):6011-6019
The main purpose of this study was to perform an evaluation of the particles’ optical parameters’ influence on surface solar UV-B (280–315 nm) irradiance in Córdoba, Argentina. To achieve this objective UV-B irradiance dataset, AERONET (AErosol RObotic NETwork) database, and TUV (Tropospheric Ultraviolet and Visible) model were used to analyze the effects of aerosols on surface irradiance on cloudless days during specific days of winter and spring of the period 1999–2006. Together with a direct observer, total irradiance (300–3000 nm) measurements were used as an ancillary tool to verify the cloudless condition. Every year, during this period, important reductions in surface irradiance are observed due to the aerosol load. Aerosols were incorporated in the model through the aerosol optical depth at 340 nm, the asymmetry parameter at 440 nm, and the single scattering albedo at 440 nm, all of them provided by AERONET Córdoba-CETT site. These factors vary from near to zero up to 1.4, from 0.56 up to 0.83 and from 0.43 up to 0.99, respectively. The behaviors of these factors along the year are analyzed considering the meteorology of Córdoba. When AERONET data are included in the TUV model they allow an accurate simulation of the UV-B irradiance, making the agreement with the experimental measurements substantially better. Only a small differences (±2%) remains, which can be attributed to diverse factors. As the AERONET site is 20 km away from the irradiance measurement site, these results show the regional character of the aerosols in Córdoba, although small contributions of urban aerosols are not discarded. An episode of high aerosol and pollutants laden due to fires in the surrounding hills is briefly analyzed. A set of additional studies are needed to describe comprehensively the characteristics and behavior of the Córdoba aerosols. Some of them are being already carried out. 相似文献
105.
四川省气溶胶光学厚度时空分布特征 总被引:2,自引:0,他引:2
本文利用MODIS气溶胶光学厚度产品,建立了气溶胶光学厚度与PM10/2.5的线性关系。分析了2008年~2012年四川省的气溶胶光学厚度时空分布特征,以成都市为特例分析了2003年~2012年的气溶胶光学厚度时空分布。结果显示:气溶胶光学厚度与PM10/2.5的线性关系较高;川西高原具有较低的气溶胶光学厚度,康定、马尔康、西昌、雅安等地年均气溶胶光学厚度约0.2;四川盆地区域具有较高的气溶胶光学厚度,以成都、德阳等地为代表,年均值在0.8~1.0之间,并具有明显季节变化特征;成都市的气溶胶光学厚度时空分布具有明显的城市特点。这些时空分布的特征与四川省的工业情况、地理位置、气候条件有关。 相似文献
106.
《Process Safety and Environmental Protection》2014,92(6):750-759
Experiments have been conducted to gain insight into the credibility of sparging aqueous solutions as an electrostatic ignition hazard for sensitive hydrogen/air or fuel/oxygen mixtures (Minimum Ignition Energies of ∼0.017 mJ and ∼0.002 mJ, respectively, compared to ∼0.25 mJ for hydrocarbon/air mixtures). Tests performed in a 0.5 m3 ullage produced electric field strengths between 125 and 560 V m−1 for air flows of 5–60 l min−1, respectively, comprised of 2–4 mm diameter bubbles. Field strength can be related to the space charge and fitting to an exponential accumulation curve enabled the charge generation rate from the air flows to be estimated. This was observed to be directly proportional to the air flow and its magnitude was consistent with literature data for bubble bursts. The charge accumulation observed at laboratory scale would not be a cause for concern. On the basis of a simple model, the charge accumulation in a 27 m3 ullage was predicted for a range of air flows. It is apparent from such calculations that ignition of hydrocarbon/air mixtures would not be expected. However, it would seem possible that field strengths might be sufficient to cause a risk of incendive spark or corona discharges in moderately sized vessels with sensitive flammable mixtures. 相似文献
107.
Particulate matter emissions from ammonia-based wet flue gas desulfurization (Ammonia-WFGD) systems are composed of a filterable particulate matter and a condensable particulate matter (CPM) portion. However, the CPM part has been ignored for a long time, which results in an underestimation of the aerosol problems caused by Ammonia-WFGD systems. In our research, the characteristics of the CPM that emits from an Ammonia-WFGD system are investigated experimentally for the first time, with the US Environmental Protection Agency Method 202 employed as the primary measurement. The influences of some essential desulfurizing parameters are evaluated based on the experimental data. The results show that CPM contributes about 68.8% to the total particulate matter emission. CPM consists mainly of ammonium sulfates/sulfites, with the organic part accounting for less than 4%. CPM is mostly in the submicron fraction, about 71.1% of which originates from the NH3–H2O–SO2 reactions. The appropriate adjustments for the parameters of the flue gas and the desulfurizing solution can inhibit CPM formation to different extents. This indicates that the parameter optimizations are promising in solving CPM emission problems in Ammonia-WFGD systems, in which the pH adjustment alone can abate CPM emission by around 49%. The opposite variations of the parameters need attention because they can cause tremendous CPM emission increase. 相似文献
108.
109.
Noshan Bhattarai Shuxiao Wang Yuepeng Pan Qingcheng Xu Yanlin Zhang Yunhua Chang Yunting Fang 《Frontiers of Environmental Science & Engineering》2021,15(6):126
110.
云贵高原1961-2006年大气能见度和消光因素变化趋势及原因 总被引:2,自引:0,他引:2
根据云贵高原203个气象台站1961—2006年大气能见度、降水、相对湿度、风速和天气现象等观测资料,采用倾向率方法对能见度和大气消光系数的变化趋势进行了分析。还应用Mann-Kendall方法对19km能见度、霾日数和消光系数的多年变化进行了气候突变检验。结果表明,有84.2%台站出现了能见度减少趋势。减少最多为-11km·10a-1,最少为-1km·10a-1。减少的平均气候倾向率在1961—1979年为0.96km·10a-1,1980—2006年为1.6km·10a-1,高原平均能见度从60年代的约34km下降到目前的约27km。另一方面,有15.8%台站能见度有增加趋势,且多集中在人类活动较为稀少的高海拔山区。有71%的台站19km能见度频率出现减少的趋势,平均倾向率为-2%·10a-1,主要出现在高原东部和中部人口和工业稠密区。该地区同时也出现霾日增加的现象。Mann-Kendall检测结果表明,19km能见度频率减少和霾日数增加现象出现突变的时间相同。年平均消光系数发生突变的时间稍推后。认为能见度下降、消光因素增加的原因与人为排放污染物浓度增加有密切关系。 相似文献