全文获取类型
收费全文 | 2197篇 |
免费 | 262篇 |
国内免费 | 885篇 |
专业分类
安全科学 | 26篇 |
废物处理 | 2篇 |
环保管理 | 230篇 |
综合类 | 1981篇 |
基础理论 | 292篇 |
污染及防治 | 173篇 |
评价与监测 | 291篇 |
社会与环境 | 311篇 |
灾害及防治 | 38篇 |
出版年
2024年 | 19篇 |
2023年 | 61篇 |
2022年 | 106篇 |
2021年 | 116篇 |
2020年 | 108篇 |
2019年 | 106篇 |
2018年 | 87篇 |
2017年 | 114篇 |
2016年 | 151篇 |
2015年 | 181篇 |
2014年 | 163篇 |
2013年 | 226篇 |
2012年 | 272篇 |
2011年 | 245篇 |
2010年 | 189篇 |
2009年 | 143篇 |
2008年 | 110篇 |
2007年 | 125篇 |
2006年 | 131篇 |
2005年 | 96篇 |
2004年 | 85篇 |
2003年 | 73篇 |
2002年 | 65篇 |
2001年 | 47篇 |
2000年 | 54篇 |
1999年 | 66篇 |
1998年 | 42篇 |
1997年 | 37篇 |
1996年 | 25篇 |
1995年 | 9篇 |
1994年 | 11篇 |
1993年 | 11篇 |
1992年 | 15篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 9篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1984年 | 4篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有3344条查询结果,搜索用时 11 毫秒
1.
2.
3.
Levee failure and overtopping as a result of Hurricane Katrina caused major flooding of New Orleans, Louisiana. Floodwaters, which were contaminated with heavy metals, organic chemicals, and fecal coliform bacteria (FCB), were pumped into neighboring Lake Pontchartrain during dewatering. The impact of levee failure on water and benthic sediment concentrations in the lake was investigated by applying a numerical water quality model coupled to a three-dimensional, numerical hydrodynamic model. The model was used to compute water and benthic sediment concentrations throughout the lake for lead, arsenic, benzo(a)pyrene (BaP), and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), and water concentrations for FCB. Computed concentrations resulting from actual pumped discharges with levee failure and overtopping were compared to computed concentrations resulting from pumped discharges without levee failure or overtopping, and concentrations from both sets of conditions were compared to ecological water and sediment quality screening guideline values. The model indicated that incremental increases above pre-Katrina benthic sediment concentrations are about a factor of 10 greater with dewatering of the floodwaters than with dewatering of storm water without flooding. However, these increases for the metals are small relative to pre-Katrina concentrations. The results showed that the ecological screening-level sediment quality guideline values were exceeded for BaP and DDE in areas near the south shoreline of the lake as a result of floodwater pump-out, whereas, this was not the case for storm water removal without flooding. The model showed that lake water column concentrations should be about the same during both dewatering conditions regardless of whether there is flooding or not. 相似文献
4.
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
5.
6.
太湖水体中悬浮颗粒物的比吸收光谱特性及其参数化分析 总被引:13,自引:0,他引:13
通过对太湖水体的野外采样,利用定量滤膜技术测量了水体中浮游植物色素的吸收系数(aph(λ))和非色素颗粒物的吸收系数(aNAP(λ)),进而推算比吸收系数.同时,对浮游植物色素和非色素颗粒物的比吸收系数的时空变化特征进行了分析.结果表明,浮游植物色素的比吸收系数(ap*h)在蓝光440nm的变化范围为0.008~0.268m2·mg-1,在红光670nm的变化范围为0.004~0.098m·2mg-1;;通过K-Mean算法将浮游植物色素的比吸收光谱分成3种具有不同光谱特征的类型,类别1、2和3占总数的百分比分别为61.0%、12.2%和26.8%,表明太湖水体中浮游植物色素的比吸收光谱是以类别1为主;;色素包裹效应因子Qa*(675)在Chla浓度<50mg·m-3时,随Chla浓度的增大迅速减小,而在Chla浓度>50mg·m-3时,其减小的趋势趋于缓慢,Qa*(675)与Chla浓度呈现出较好的幂函数关系.非色素颗粒物的比吸收系数(aN*AP)在蓝光440nm处的变化范围为0.012×10-3~0.143×10-3m2·mg-1,利用此处的比吸收系数建立的非色素颗粒物比吸收光谱的参数化模型,光谱曲线斜率... 相似文献
7.
8.
Vertical and temporal distributions of N and P in soil solution in aquatic-terrestrial ecotone (ATE) of Taihu Lake were investigated, and the relations among N, P, ORP (oxidation reduction potential), TOC, root system biomass and microorganism were studied. As a whole, significant declines in TN, NO3^--N, DON (dissolved organic nitrogen) and TP concentration in soil solution have occurred with increase of the depth, and reached their minima at 60 cm depth, except for NH4^+-N, which increased with depth. The concentration of TP increased gradually from spring to winter in the topsoil, the maximum 0.08 mg/L presented in the winter while the minimum 0.03 mg/L in spring. In the deeper layer, the concentration value of TP fluctuated little. As for the NO3^--N, its seasonal variation was significant at 20 cm depth, its concentration increased gradually from spring to autumn, and decreased markedly in winter. Vertical and temporal distribution of DON is contrary to that of NO3^--N. The results also show that the variation of N and P in the percolate between adjacent layers is obviously different. The vertical variation ofTN, TP, NO3^--N, NH4^+-N and DON is significant, of which the variation coefficient of NO3^--N along the depth reaches 100.23%, the highest; while the variation coefficient of DON is 41.14%, the smallest. The results of correlation analysis show that the concentration of nitrogen and phosphorus correlate significantly with TOC, ORP, root biomass and counts of nitrifying bacteria. Most nutrients altered much from 20 to 40 cm along the depth. However, DON changed more between 60 and 80 cm. Results show that soil of 0-60 cm depth is active rhizoplane, with strong capability to remove the nitrogen and phosphorus in ATE. It may suggest that there exists the optimum ecological efficiency in the depth of above 60 cm in reed wetland. This will be very significant for ecological restoration and reestablishment. 相似文献
9.
采用多介质环境数学模型,评价太湖流域居民暴露于DDTs的健康风险,分析风险来源、暴露介质及暴露途径,并结合蒙特卡罗方法分析研究过程中的不确定性. 结果表明,太湖流域居民中男性和女性对环境中DDTs的终身日平均暴露量分别为4.00×10-4~8.28×10-3和3.73×10-4~7.28×10-3 mg/(kg·d). 暴露途径中食物摄取是最主要途径,其次是吸入,皮肤暴露作用很小. 食物中贡献较大的为谷物、鱼类和肉类. 相应的男性和女性的健康风险度分别为0.114×10-6~2.366×10-6 和0.107×10-6~2.081×10-6 a-1,低于可接受健康风险度标准的累积概率分别为80.85%和86.05%. 相似文献
10.
巢湖水体组分垂向分布特征及其对水下光场的影响 总被引:4,自引:1,他引:4
富营养化湖泊不同组分垂向分布及其对水下光场的影响是湖泊水环境遥感领域亟待开展的内容.利用巢湖野外实测数据,分析水体不同组分垂向分布特征,结合Hydrolight辐射传输模型模拟研究水体不同组分垂向分布对漫衰减系数Kd的影响.结果表明,巢湖水体悬浮物以及有色可溶性有机物CDOM垂向分布较为均一,水面未发生藻华现象时叶绿素a垂向分布符合高斯正态分布,漫衰减系数Kd受叶绿素a以及无机悬浮物的显著影响,其垂向变化复杂多样,以往以水体光学性质均一为前提计算得到的Kd仅仅表示其衰减的平均情况,不能精确反映水下光场的垂向变化,因此研究水体组分垂向分布特征及其对漫衰减系数Kd的影响是开展藻类垂向分布异质性对水下光场影响机制研究的前提和基础. 相似文献