全文获取类型
收费全文 | 4570篇 |
免费 | 429篇 |
国内免费 | 1691篇 |
专业分类
安全科学 | 363篇 |
废物处理 | 176篇 |
环保管理 | 782篇 |
综合类 | 3033篇 |
基础理论 | 743篇 |
污染及防治 | 888篇 |
评价与监测 | 332篇 |
社会与环境 | 258篇 |
灾害及防治 | 115篇 |
出版年
2024年 | 6篇 |
2023年 | 73篇 |
2022年 | 137篇 |
2021年 | 171篇 |
2020年 | 149篇 |
2019年 | 171篇 |
2018年 | 193篇 |
2017年 | 216篇 |
2016年 | 290篇 |
2015年 | 257篇 |
2014年 | 330篇 |
2013年 | 413篇 |
2012年 | 427篇 |
2011年 | 448篇 |
2010年 | 353篇 |
2009年 | 444篇 |
2008年 | 275篇 |
2007年 | 325篇 |
2006年 | 303篇 |
2005年 | 291篇 |
2004年 | 200篇 |
2003年 | 188篇 |
2002年 | 156篇 |
2001年 | 138篇 |
2000年 | 121篇 |
1999年 | 114篇 |
1998年 | 87篇 |
1997年 | 63篇 |
1996年 | 69篇 |
1995年 | 74篇 |
1994年 | 55篇 |
1993年 | 34篇 |
1992年 | 31篇 |
1991年 | 18篇 |
1990年 | 14篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 2篇 |
排序方式: 共有6690条查询结果,搜索用时 296 毫秒
701.
Tony Prato Choongkwan Kang 《Journal of the American Water Resources Association》1998,34(6):1465-1472
ABSTRACT: Nitrogen (N) fertilizer rates for achieving optimum crop yields often vary within a field due to spatial variability in soil moisture and nitrogen content and other crop growth factors. When there is substantial within-field variability in these factors, uniform application of N (UAN) may not be economically efficient in terms of maximizing net return because N is likely to be over-applied in some areas and under-applied in other areas of the field. In addition, over-application can adversely affect water quality. A sample of fields in a Midwestern agricultural watershed is used to test for statistically significant differences in N application rates, crop yields, surface and ground water quality and net returns between UAN and variable application of N (VAN) for four cropping systems. Profitability and water quality benefits of VAN are sensitive to the distribution of soil types within a field. Water quality effects and profitability of UAN and VAN vary with cropping systems. VAN is not uniformly superior to UAN in terms of increasing net returns and improving water quality for the farming systems and watershed evaluated in this study. 相似文献
702.
M. H. N. Tabrizi S. E. Said A. W. Badr Y Mashor S. A. Billings 《Journal of the American Water Resources Association》1998,34(6):1333-1339
ABSTRACT: Model estimation and prediction of a river flow system are investigated using nonlinear system identification techniques. We demonstrate how the dynamics of the system, rainfall, and river flow can be modeled using NARMAX (Nonlinear Autoregressive Moving Average with eXogenuous input) models. The parameters of the model are estimated using an orthogonal least squares algorithm with intelligent structure detection. The identification of the nonlinear model is described to represent the relationship between local rainfall and river flow at Enoree station (inputs) and river flow at Whitmire (output) for a river flow system in South Carolina. 相似文献
703.
704.
研究了UV/H2O2工艺对2,4-二氯酚(2,4-DCP)的去除效果和水中阴离子、腐殖酸对该工艺降解2,4-DCP的影响。结果表明:UV/H2O2工艺可以有效的去除水中2,4-DCP,光降解过程符合一级反应动力学模型;在H2O2投加量为8mg/L,1个30W低压汞灯照射下,2,4-DCP在蒸馏水和自来水中光降解速率常数分别为0.0232/min和0.0162/min;NO3-、Cl-、HCO3-对2,4-DCP光降解有抑制作用;当3种离子浓度为0.5mmol/L、10mmol/L、20mmol/L时,对2,4-DCP光降解的抑制程度为HCO3->NO3->Cl-;随着离子浓度增大,抑制作用增强;自来水中的光降解速率常数低于蒸馏水中的光降解速率常数是由于水中多种离子影响的结果;腐殖酸在低浓度时,促进光降解反应的进行,在高浓度时,2,4-DCP的光降解氧化受到抑制。 相似文献
705.
706.
707.
本文建立了准确预测多环芳烃(PAHs)及其烷基衍生物的正-辛醇/水分配系数(Kow)模型。模型表明PAHs的分配性质可用零阶价分子连接性指数(~°x~v)描述,~°x~v数值与PAHs的logKow成正比。应用本模型可以预测大范围PAHs的logKow值。 相似文献
708.
讨论了城市污水经过A/O工艺处理时活性污泥的二次污染问题。将原水、处理后的出水及活性污泥用甲苯萃取,萃取相经过真空浓缩后,采用GC/MS测定了样品中的有机化合物,结果表明,在A/O工艺处理城市污水过程中,活性污泥的吸附作用是主要的,降解作用是次要的;A/O工艺所排放的活性污泥仍然是一种危险的污染物。 相似文献
709.
R. Lorenzo R. Kaegi R. Gehrig B. Grobty 《Atmospheric environment (Oxford, England : 1994)》2006,40(40):7831-7841
The goal of this study was to identify and quantify particles emitted from railway traffic. For that purpose PM10 samples were collected near a busy railway line using a wind direction and speed controlled sampling equipment consisting of five devices. Measurements taken perpendicular to the railway lines at 10, 36 and 120 m distance enable an identification and separation of particles caused by the railway traffic from background particles. Morphology and chemistry of more than 11,000 particles were analysed by computer controlled scanning electron microscopy (CCSEM). Based on chemical composition five particle classes are defined and assigned to their sources. The mass of the individual particles is determined by multiplying their volumes, calculated based on their morphology with a density assigned specifically to each particle class. The density of the particle classes is derived from their chemical composition. To estimate the PM10 contributions of the railway lines, the mass of PM10 at 120 m (background, not influenced by the railway lines) is subtracted from the mass of PM10 at 10 m. The emissions of the railway lines are dominated by ‘iron’ particles, which contribute 2.9 μg m−3 or 67% to the railway related PM10. In addition, ‘aluminium’ and ‘calcium’ particles contribute also to the railway related PM10 (1.0 μg m−3 or 23% for the ‘aluminium’ and 0.4 μg m−3 or 10% for the ‘calcium’ particles). These particles are assigned to abrasion of the gravel bed and re-suspension of mineral dust.Long-term gravimetric results of the contribution of iron to the mass of railway related PM10 from a study performed earlier at the same site are in good agreement with the data presented in this study. 相似文献
710.
In FRG and other countries unequivocal criteria for the limitation of dioxins (PCDD's/PCDF's) in food like vegetables and fruits are lacking. These have to be directly associated with the limitation of dioxins in the soil and the deposition of particulate matter as the two main pathways for plant contamination. Based on recent investigations in the vicinity of cable-waste incinerators in Northrhine-Westphalia with comparatively high contents of dioxins in garden plants and soils and other sources of dioxins, considerations are given for the establishment of the criteria urgently needed. 相似文献