全文获取类型
收费全文 | 564篇 |
免费 | 66篇 |
国内免费 | 357篇 |
专业分类
安全科学 | 16篇 |
废物处理 | 29篇 |
环保管理 | 37篇 |
综合类 | 580篇 |
基础理论 | 181篇 |
污染及防治 | 113篇 |
评价与监测 | 18篇 |
社会与环境 | 11篇 |
灾害及防治 | 2篇 |
出版年
2024年 | 1篇 |
2023年 | 9篇 |
2022年 | 28篇 |
2021年 | 29篇 |
2020年 | 26篇 |
2019年 | 30篇 |
2018年 | 28篇 |
2017年 | 26篇 |
2016年 | 36篇 |
2015年 | 38篇 |
2014年 | 58篇 |
2013年 | 57篇 |
2012年 | 63篇 |
2011年 | 80篇 |
2010年 | 54篇 |
2009年 | 60篇 |
2008年 | 50篇 |
2007年 | 39篇 |
2006年 | 48篇 |
2005年 | 33篇 |
2004年 | 38篇 |
2003年 | 28篇 |
2002年 | 19篇 |
2001年 | 28篇 |
2000年 | 25篇 |
1999年 | 14篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1982年 | 3篇 |
1978年 | 1篇 |
排序方式: 共有987条查询结果,搜索用时 15 毫秒
891.
利用湿地中高丰度的代表性反硝化菌Shewanella denitrificans,文章通过批式实验,探究典型湿地环境条件下pH和C/N对微生物反硝化排放N_2O的影响和机制。结果表明,在典型湿地环境条件下,S. denitrificans介导的反硝化均能排放N_2O温室气体。其中,当C/N为7.5或75时N_2O排放速率最快,比最低排放速率高出约54%。当pH为5.5时,N_2O排放速率较pH为6.5时增加约67%。不同pH和C/N条件下N_2O的排放差异可能主要由p H差异导致,或p H和C/N差异共同所致。双因素方差分析结果表明,pH和C/N不仅分别显著影响N_2O排放,并且两者对N_2O排放具有显著的交互影响。这些发现为湿地生态系统N_2O排放的模型构建和评估预测提供了科学依据。 相似文献
892.
15N-labeling and solid-state 13C and 15N nuclear magnetic resonance (NMR) spectroscopy was applied to study the immobilization of 2,4,6 trinitrotoluene (TNT) into
soil organic matter (SOM). Uncontaminated soil from the Ap horizon of a Luvisol was mixed with 15N-TNT (enrichment: 99 atm%) and laid over an unspiked layer of the same material. The latter covered soil from the Bt horizon.
The microcosms were aerobically incubated under laboratory conditions for up to 11 months. After 1 week, within the total
microcosm approximately 90% of the added 15N (15Nadd) were recovered, mostly in the top layer (87%). After 11 months, this amount decreased to 71%, indicating losses due to denitration
or transamination. Within two months, half of 15Nadd had been immobilized in the residues not extractable with organic solvents and water. The amount of the sequestered 15Nadd remained fairly constant until the end of the experiment pointing towards a high stability of TNT-SOM associates. Solid-state
15N NMR revealed their formation by covalent binding, most tentatively as amides. Complete reduction of TNT to triaminotoluene
(TAT) was not prerequisite. The most pronounced downwards movement of 15N-TNT occurred during the first two months. The major part of it, however, experienced quick immobilization, leaving approximately
10% of 15Nadd recovered in the leachate at the end of the experiment. Calculations indicated contributions of inorganic 15Nadd. Approximately 25% of its organic 15Nadd originated from condensed N, suggesting that in soils the transport of partly reduced TNT is in close association with the
organic matter of the soil solution to which they are covalently bound. 相似文献
893.
S. A. Power M. R. Ashmore A. C. Terry S. J. M. Caporn M. G. Pilkington D. B. Wilson C. G. Barker J. A. Carroll N. Cresswell E. R. Green G. W. HEIL 《Water, Air, & Soil Pollution: Focus》2004,4(6):259-267
The results from three long-term field manipulation studies of the impacts of increased nitrogen deposition (0–120 kg N ha–1 yr–1) on lowland and upland heathlands in the UK were compared, to test if common responses are observed. Consistent increases in Calluna foliar N content and decreases in litter C:N ratios were found across all sites, while increases in N leaching were not observed at any site over the range 0–80 kg ha–1 yr–1. However, the response of Calluna biomass did vary between sites, possibly reflecting site differences in nutrient status and management histories. Five versions of a simulation model of heathland responses to N were developed, each reflecting different assumptions about the fate and turnover of soil N. Model outputs supported the deduction from mass balance calculations at two of the field sites that N additions have resulted in an increase in immobilisation; the latter was needed to prevent the model overestimating measured N leaching. However, this version of the model significantly underestimated Calluna biomass. Model versions, which included uptake of organic N by Callunaand re-mobilisation of N from the soil organic store provided some improvement in the fit between modelled and field biomass data, but re-mobilisation also led to an overestimation of N leaching. Quantification of these processes and their response to increased N deposition are therefore critical to interpreting experimental data and predicting the long-term impacts of atmospheric deposition on heathlands and moorlands. 相似文献
894.
Richard W. McDowell Andrew N. Sharpley Peter J. A. Kleinman 《Journal of the American Water Resources Association》2002,38(2):479-491
ABSTRACT: The persistence of water quality problems has directed attention towards the reduction of agricultural nonpoint sources of phosphorus (P) and nitrogen (N). We assessed the practical impact of three management scenarios to reduce P and N losses from a mixed land use watershed in central Pennsylvania, USA. Using Scenario 1 (an agronomic soil P threshold of 100 mg Mehlich‐3 P kg‐1, above which no crop response is expected), 81 percent of our watershed would receive no P as fertilizer or manure. Under Scenario 2 (an environmental soil P threshold of 195 mg Mehlich‐3 P kg‐1, above which the loss of P in surface runoff and subsurface drainage increases greatly), restricts future P inputs in only 51 percent of the watershed. Finally, using scenario 3 (P and N indices that account for likely source and transport risks), 25 percent of the watershed was at high risk or greater of P loss, while 60 percent of the watershed was classified as of high risk of nitrate (NO3) leaching. Areas at risk of P loss were near the stream channel, while areas at risk of NO3 leaching were near the boundaries of the watershed, where freely draining soils and high manure and fertilizer N applications coincide. Remedial measures to minimize P export should focus on critical source areas, while remedial measures to reduce N losses should be source based, concentrating on more efficient use of N by crops. 相似文献
895.
《环境科学学报(英文版)》2023,35(7):213-228
Bisphenol A (BPA) has received increasing attention due to its long-term industrial application and persistence in environmental pollution. Iron-based carbon catalyst activation of peroxymonosulfate (PMS) shows a good prospect for effective elimination of recalcitrant contaminants in water. Herein, considering the problem about the leaching of iron ions and the optimization of heteroatoms doping, the iron, nitrogen and sulfur co-doped tremella-like carbon catalyst (Fe-NS@C) was rationally designed using very little iron, S-C3N4 and low-cost chitosan (CS) via the impregnation-calcination method. The as-prepared Fe-NS@C exhibited excellent performance for complete removal of BPA (20 mg/L) by activating PMS with the high kinetic constant (1.492 min−1) in 15 min. Besides, the Fe-NS@C/PMS system not only possessed wide pH adaptation and high resistance to environmental interference, but also maintained an excellent degradation efficiency on different pollutants. Impressively, increased S-C3N4 doping amount modulated the contents of different N species in Fe-NS@C, and the catalytic activity of Fe-NS@C-1-x was visibly enhanced with increasing S-C3N4 contents, verifying pyridine N and Fe-Nx as main active sites in the system. Meanwhile, thiophene sulfur (C-S-C) as active sites played an auxiliary role. Furthermore, quenching experiment, EPR analysis and electrochemical test proved that surface-bound radicals (·OH and SO4⋅−) and non-radical pathways worked in the BPA degradation (the former played a dominant role). Finally, possible BPA degradation route were proposed. This work provided a promising way to synthesize the novel Fe, N and S co-doping carbon catalyst for degrading organic pollutants with low metal leaching and high catalytic ability. 相似文献
896.
农田土壤硝化-反硝化作用与N_2O的排放 总被引:2,自引:0,他引:2
在北京潮土上研究了冬小麦夏玉米轮作体系下土壤硝化反硝化作用以及N2O排放情况。结果表明,小麦生育期土壤温度及含水量较低,无论是反硝化损失氮量还是土壤的N2O生成排放量均不高。土壤的N2O生成排放量与反硝化氮量相当或低于反硝化氮量。玉米生育期土壤温度升高以及孔隙含水量有较大的改善,反硝化损失氮量、N2O生成排放量有明显上升。通常情况下土壤反硝化损失氮量与N2O排放氮量基本处于同一水平。在玉米十叶期追肥后的较短时间内,N2O总排放量明显高于反硝化损失氮量,说明至少在这一阶段中,硝化作用在北方旱地土壤N2O的排放中发挥了主要作用。在评价北方旱地农田土壤氮素硝化反硝化损失中,硝化作用的氮素损失是不可忽视的重要方面。 相似文献
897.
选取引江济太工程中长江来水进入太湖第一站的贡湖湾为研究对象,基于2011年11月~2013年8月在贡湖湾的逐月野外调查,同时以湖心水域为参考,探讨引江济太对湖体N2O通量的影响.结果表明,贡湖湾N2O排放通量要显著高于湖心排放量,其N2O通量均值分别为6.9,2.1μmol/(m2·d),但在非引水期间2个湖区的N2O通量无显著差异.贡湖湾和湖心N2O通量呈现明显的季节变化,且均与水温呈显著负相关关系,但因受外源来水的影响,贡湖湾N2O通量的温度依赖程度相对较低.另外,2个湖区的N2O通量还与营养盐等因素有关.总体上,外源引水提高了贡湖湾N2O排放通量,但考虑到湖泊N2O通量受到内部和外部因子的综合协同影响,外源引水对湖泊N2O通量的具体调控机理还需要进一步探讨. 相似文献
898.
899.
以模拟低C/N比污水为研究对象,采用集成模块式污水处理装置与技术,在反应器主反应区实现了同步硝化反硝化(SND),研究了在不同DO、HRT、C/N比、pH值下污水氨氮、总氮的去除,研究结果表明,DO=1.2~1.4mg/L,总HRT=20h(主反应区HRT=8h),原水C/N=5:1,pH=7.5时,NH3--N可以从15mg/L降至2.5mg/L,总氮可以从20mg/L降至4mg/L,去除率可以达到83%和80%;主反应区SND动力学模型求解得出集成模块式污水处理SND动力学方程及反硝化过程中硝酸盐氮饱和常数 =1.55mg/L,远高于普通活性污泥反硝化过程中的饱和常数0.06~0.2mg/L.集成模块式污水处理技术能高效去除低C/N比污水中的总氮,且具有运行稳定和抗冲击等优点.为中小城镇生活污水深度脱氮提供了技术支持和理论基础. 相似文献
900.
芦芽山土壤有机碳和全氮沿海拔梯度变化规律 总被引:1,自引:0,他引:1
研究不同海拔梯度和坡向的土壤碳氮分布,能在较小的空间尺度上反映不同气候状况下土壤碳氮分布规律,揭示多个互相关联的环境因子对土壤碳氮分布规律的综合影响。对山西省北部芦芽山芦芽山沿海拔梯度土壤有机碳和全氮含量的变化规律进行了分析。自海拔1703.1 m至2756.3 m每上升约50 m设置一个样带(共计21块),每样带内布设30 m×30 m样地3个,每个样地内“S”形布点,分3层(0~10、10~25、25~40 cm)钻取土样。结果表明,在研究海拔范围内土壤垂直剖面自表层向下有机碳质量分数分别为(35.71±13.32)、(29.18±12.85)和(26.39±12.74) g· kg-1,全氮质量分数分别为(2.83±0.93)、(2.38±0.84)和(2.12±0.80) g· kg-1。土壤有机碳和全氮含量的分布特征均表现为随海拔升高而增加的趋势,与海拔呈极显著的线性正相关。土壤有机碳含量与海拔线性模型的回归系数在10~25 cm土层最大,而全氮与海拔线性模型的回归系数随土层深度增加而递减。土壤有机碳含量最高值出现在较高海拔处寒温性针叶林下,而土壤全氮含量最高值出现在最高海拔的亚高山草甸。碳氮含量的剖面分布呈现为表层(0~10 cm)最高,随深度下降而递减。研究区土壤C/N值介于5~19,最小值为海拔最高(2756.3 m)的亚高山草甸,而最大值为较高海拔分布的寒温性针叶林(2332.6 m),沿海拔梯度表现呈“Λ”型的变化趋势。 相似文献