全文获取类型
收费全文 | 201篇 |
免费 | 23篇 |
国内免费 | 67篇 |
专业分类
安全科学 | 30篇 |
废物处理 | 9篇 |
环保管理 | 28篇 |
综合类 | 146篇 |
基础理论 | 35篇 |
污染及防治 | 25篇 |
评价与监测 | 9篇 |
社会与环境 | 5篇 |
灾害及防治 | 4篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 10篇 |
2020年 | 14篇 |
2019年 | 9篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 10篇 |
2014年 | 9篇 |
2013年 | 12篇 |
2012年 | 8篇 |
2011年 | 15篇 |
2010年 | 6篇 |
2009年 | 14篇 |
2008年 | 9篇 |
2007年 | 16篇 |
2006年 | 9篇 |
2005年 | 10篇 |
2004年 | 13篇 |
2003年 | 12篇 |
2002年 | 11篇 |
2001年 | 7篇 |
2000年 | 10篇 |
1999年 | 5篇 |
1998年 | 8篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1986年 | 1篇 |
1981年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有291条查询结果,搜索用时 109 毫秒
61.
人工强制混合充氧及诱导自然混合对水源水库水质改善效果分析 总被引:8,自引:8,他引:0
为探究人工强制混合充氧与诱导持续混合对水质改善的影响及人工强制混合与自然混合的衔接条件,以李家河水库为例,于2017年6月至2019年4月开展水质及水文气象指标监测,分析自然过程及人工诱导混合过程各时期水温、溶解氧及水质变化特征.结果表明:①自然过程分层期持续时间长,混合期仅为2.5个月,人工诱导混合过程通过扬水曝气系统的运行, 9月底水体达到完全混合且进入降温期,诱导自然混合条件具备,表层水温、平均气温分别为20.17℃和16.5℃,此时系统关闭后水体持续自然混合,混合周期延长至5.5个月;②自然过程污染物浓度较高,混合期表层污染物浓度呈现先增加后降低的趋势,氧跃层伴随热分层出现,底部厌氧周期达6个月;③相较于自然过程,人工诱导混合过程水体等温层厌氧消除且污染物控制效果良好, 10月至翌年3月同期底层NH+4-N、 TP、 Fe和Mn浓度的削减率为76.2%、 75.5%、 82.2%和82.1%,均达到地表水环境质量标准,人工诱导混合过程有利于水质改善及混合作用时效的延长. 相似文献
62.
W. Graham Glen Michael P. Zelenka Richard C. Graham 《Atmospheric environment (Oxford, England : 1994)》1996,30(24):4225-4232
A model which quantifies the relationship between the monthly time series for CO emissions, the monthly time series in ambient CO concentration, and meteorologically driven dispersion was developed. Fifteen cities representing a wide range of geographical and climatic conditions were selected. An eight-year time series (1984–1991 inclusive) of monthly averaged data were examined in each city. A new method of handling missing ambient concentration values which is designed to calculate city-wide average concentrations that follow the trend seen at individual monitor sites is presented. This method is general and can be used in other applications involving missing data. The model uses emissions estimates along with two meteorological variables (wind speed and mixing height) to estimate monthly averages of ambient air pollution concentrations. The model is shown to have a wide range of applicability; it works equally well for a wide range of cities that have very different temporal CO distributions. The model is suited for assessing long-term trends in ambient air pollutants and can also be used for estimating seasonal variations in concentration, estimation of trends in emissions, and for filling in gaps in the ambient concentration record. 相似文献
63.
64.
本文讨论了川西前陆盆地气田区上三叠统和侏罗系地层水K+ +Na+ 、Ca2 + 、Mg2 + 、Br-与Cl-离子、矿物 (胶结物和充填物 )碳氧同位素和水的氢氧同位素成分组成以及相互关系。气田区上三叠统流体来源以地层海陆相沉积物质为主 ,并与渗流水混合 ,形成“下部流体”。有气藏的侏罗系内流体 (称“上部流体”)与“下部流体”的水化学和同位素组成相近 ,且具有同一演化趋势 ,表明它来源于下部流体并与侏罗系层内的渗流水发生过混合作用。本文提出该气田流体具跨层流动、二次混合演化特征 ,认为大规模的流体对流混合促进了上三叠统内天然气的运移聚积 ,在三叠系内有利构造圈闭中形成原生或残留气藏并向上运移 ,在侏罗系内有利圈闭中形成“次生”气藏。 相似文献
65.
66.
Gerhard H. Jirka 《Environmental Fluid Mechanics》2006,6(1):43-100
An integral model for the plane buoyant jet dynamics resulting from the interaction of multiple buoyant jet effluxes spaced
along a diffuser line is considered as an extension of the round jet formulation that was proposed in Part I. The receiving
fluid is given by an unbounded ambient environment with uniform density or stable density stratification and under stagnant
or steady sheared current conditions. Applications for this situation are primarily for submerged multiport diffusers for
discharges of liquid effluents into ambient water bodies, but also for multiple cooling tower plumes and building air-conditioning.
The CorJet model formulation describes the conservation of mass, momentum, buoyancy and scalar quantities in the turbulent
jet flow in the plane jet geometry. It employs an entrainment closure approach that distinguishes between the separate contributions
of transverse shear and of internal instability mechanisms, and contains a quadratic law turbulent pressure force mechanism.
But the model formulation also includes several significant three-dimensional effects that distinguish actual diffuser installations
in the water environment. These relate to local merging processes from the individual multiple jets, to overall finite length
effects affecting the plume geometry, and to bottom proximity effects given by a “leakage factor” that measures the combined
affect of port height and spacing in allowing the ambient flow to pass through the diffuser line in order to provide sufficient
entrainment flow for the mixing downstream from the diffuser. The model is validated in several stages: First, comparison
with experimental data for the asymptotic, self-similar stages of plane buoyant jet flows, i.e. the plane pure jet, the pure
plume, the pure wake, the advected line puff, and the advected line thermal, support the choice of the turbulent closure coefficients
contained in the entrainment formulation. Second, comparison with data for many types of non-equilibrium flows with a plane
geometry support the proposed functional form of the entrainment relationship, and also the role of the pressure force in
the jet deflection dynamics. Third, the observed behavior of the merging process from different types of multiport diffuser
discharges in both stagnant and flowing ambient conditions and with stratification appears well predicted with the CorJet
formulation. Fourth, a number of spatial limits of applicability, relating to terminal layer formation in stratification or
transition to passive diffusion in a turbulent ambient shear flow, have been proposed. In sum, the CorJet integral model appears
to provide a mechanistically sound, accurate and reliable representation of complex buoyant jet mixing processes, provided
the condition of an unbounded receiving fluid is satisfied. 相似文献
67.
In order to evaluate the performance of different methods for estimation of the vertical eddy diffusivity in thermally stratified
lakes, two field studies were conducted in Lake Biwa, Japan and Lake Kinneret, Israel. Lake Biwa experienced three typhoons
during the campaign while Lake Kinneret experienced high winds in the afternoons. Microstructure profiles were collected by
a portable flux profiler (PFP) during calm and disturbed periods. Then, the vertical eddy diffusivity was estimated by three
indirect methods. The estimated vertical eddy diffusivities varied more than one order of magnitude, from 4.7× 10−7 to 7.7× 10−6 m2 s−1. The comparison of results with previous buoyancy flux measurements and scaling arguments showed that the Dillon–Park’s method
is not appropriate and Osborn–Cox method performs better than Osborn method in the studied case. Furthermore, the low value
of vertical eddy diffusivity within the thermocline suggests that within the thermocline of these lakes, diffusive vertical
transport can be neglected. 相似文献
68.
Environmental Impact of Undular Tidal Bores in Tropical Rivers 总被引:3,自引:1,他引:3
A tidal bore impacts significantly on the estuarine ecosystem, although little is known on the flow field, mixing and sediment
motion beneath tidal bores. In the absence of detailed systematic field measurements, a quasi-steady flow analogy was applied
to investigate undular tidal bores with inflow Froude numbers between 1.25 and 1.6. Experimental results indicated that rapid
flow redistributions occur beneath the free-surface undulations, with significant variations in bed shear stress between wave
crests and troughs. Dynamic similarity was used to predict detailed flow characteristics of undular tidal bores. The effects
of periodic loading on river sediments, scour of river bed and flow mixing behind the bore are discussed. A better understanding
of these processes will contribute to better management practices in tidal bore affected rivers, including the Styx and Daly
rivers in tropical Australia. 相似文献
69.
本研究采用上流式厌氧污泥床滤层反应器对蛋鸡场鸡粪混合液离心出水进行处理,试验结果:在中温25℃,进水COD_(cr)18000mg/L和氨氮1600mg/L的条件下,COD_(cr)去除率74.08%,BOD_5去除率83.78%,水力停留时间26.15h,容积负荷15.60kg·COD_(cr)/m~3·d,产气率0.52m~3/去除km·COD_(cr).反应器运行状况良好. 相似文献
70.
燃煤型倒焰窑排放的烟法浓度高,处理难度大,已成为大气治理中的新热点。采用实用新型燃煤机,改变煤的燃烧方式使其完全燃烧,从而使燃煤烟气污染得到有效的控制达标排放并节约能源。 相似文献