全文获取类型
收费全文 | 626篇 |
免费 | 32篇 |
国内免费 | 251篇 |
专业分类
安全科学 | 39篇 |
废物处理 | 34篇 |
环保管理 | 59篇 |
综合类 | 342篇 |
基础理论 | 130篇 |
污染及防治 | 189篇 |
评价与监测 | 41篇 |
社会与环境 | 41篇 |
灾害及防治 | 34篇 |
出版年
2023年 | 9篇 |
2022年 | 33篇 |
2021年 | 27篇 |
2020年 | 21篇 |
2019年 | 24篇 |
2018年 | 31篇 |
2017年 | 36篇 |
2016年 | 29篇 |
2015年 | 36篇 |
2014年 | 30篇 |
2013年 | 54篇 |
2012年 | 50篇 |
2011年 | 56篇 |
2010年 | 52篇 |
2009年 | 37篇 |
2008年 | 42篇 |
2007年 | 45篇 |
2006年 | 41篇 |
2005年 | 23篇 |
2004年 | 23篇 |
2003年 | 22篇 |
2002年 | 32篇 |
2001年 | 29篇 |
2000年 | 31篇 |
1999年 | 11篇 |
1998年 | 16篇 |
1997年 | 9篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 13篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 9篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有909条查询结果,搜索用时 343 毫秒
101.
102.
为解决人工神经网络(ANN)对复杂系统进行事故预测建模时,易导致网络复杂,降低网络性能和增大预测误差的问题,提出一种基于主成分分析法(PCA)的ANN事故预测方法。介绍PCA法和ANN的基本理论,阐述基于PCA法的ANN事故预测模型及其预测步骤,即在利用ANN预测之前,先用PCA法分析事故影响指标,将多个指标转化为少数几个能反映原始信息的互不相关的综合变量(主成分),然后以这些变量作为输入进行ANN建模,从而达到简化模型,提高网络性能和计算精度的目的。以煤矿事故预测为例,进行应用和对比研究。结果表明:基于PCA的ANN事故预测相对误差小于3%,而直接运用ANN方法预测的相对误差达到5%。这说明,对复杂安全系统进行事故预测时,基于PCA法的ANN预测方法是更可行的。 相似文献
103.
为得到地铁区间隧道竖井送风有效风量的无量纲计算模型,通过推导地铁区间隧道竖井送风有效风量的无量纲公式,并采用数值模拟方法明确竖井送风有效风量与火源功率、火源距离、阻塞比和竖井送风量之间的量化关系。结果表明:火源功率、火源距离与竖井送风有效风量之间不存在函数关系;阻塞比对竖井送风有效风量影响显著,随着阻塞比的增大,有效风量逐渐减小,单侧列车停靠时,无量纲有效风量Qe*与阻塞比β呈-1.08次方减小关系,两侧列车停靠时,无量纲有效风量Qe*与阻塞比β呈-0.22次方减小关系;有效风量随竖井送风风量的增大逐渐增大,且有效风量增大比例高于送风风量,单侧列车停靠时,无量纲有效风量与无量纲送风风量呈1.11次方增大关系,两侧列车停靠时,无量纲有效风量与无量纲送风风量呈1.07次方增大关系。 相似文献
104.
105.
The mineralization of phenol in aerated electrochemical oxidation has been investigated.The results show that a cathodic Fenton process can occur when the Ti-0.3Mo-0.8Ni alloy material is used as cathode in solution containing ferric or ferrous ions; moreover,the reinforcement of cathodic Fenton process on the total organic carbon (TOC) removal rate of phenol is quite distinct.Among the metallic ions investigated,the ferric ion is the best catalyst for the electrochemical mineralization of phenol at initial... 相似文献
106.
107.
Allelopathic inhibition on red tide microalgae Skeletonema costatum by five macroalgal extracts 总被引:1,自引:0,他引:1
Zhen An Zhenyu Wang Fengmin Li Zhijia Tian Hongying Hu 《Frontiers of Environmental Science & Engineering in China》2008,2(3):297-305
This study aims to identify effective antialgal allelochemicals from marine macroalgae that inhibit the growth of red tide
microalgae. Practically, new algicidal agents were developed to control red tide. The growth inhibitory effects of 5 marine
macroalgae Porphyra tenera, Laminaria japonica, Ulva pertusa, Enteromorpha clathrata, and Undaria pinnatifida on Skeletonema costatum were evaluated by adding crude seawater extracts of macroalgal dry tissue into the culture medium containing S. costatum. The half-effective concentrations at 120 h (EC50, 120 h) of the seawater extracts were 0.6, 0.9, 1.0, 1.0, and 4.7 g/L for the five macroalgae above, respectively. E. clathrata, L. japonica and U. pertusa showed strong allelopathic effect on the growth of S. costatum. There have been no previous reports with regard to the allelopathic effects of the former two macroalgae so far. The possible
allelochemicals of 21 compounds of the E. clathrata were detected using Gas chromatography-mass spectrometry (GC-MS) analysis. Unsaturated fatty acids, acrylic acid (C3H4O2), and linolenic acid (C18H30O2) were the most likely allelochemicals in E. clathrata. 相似文献
108.
Solubilization of mixed polycyclic aromatic hydrocarbons through a rhamnolipid biosurfactant 总被引:2,自引:0,他引:2
The solubilization of phenanthrene (PHE) and pyrene (PYR) by rhamnolipid biosurfactant was systematically investigated. The solubilities of both polycyclic aromatic hydrocarbons (PAHs) were increased linearly with the biosurfactant concentration at above critical micelle concentration. A competitive effect was observed between PHE and PYR. The solubility of PHE in a mixed system was lower than that in a single PAH system, whereas the solubility of PYR in a mixed system was enhanced. This is because the hydrophobicity of PYR is higher than that of PHE, so PYR is favored in the competitive solubilization. The combined effect of biosurfactant and dissolved organic matter (DOM) on PAH solubilization was also examined. Two kinds of DOM (derived from soil and from compost) were used. There was an obvious enhancement of solubility for PHE and PYR in systems with concurrence of DOM and biosurfacrant compared with systems with only DOM or biosurfactant; however, the enhancement in the mixed system was less than their additive. This could be explained as the formation of a DOM-biosurfactant complex. In addition, the solubility enhancement of PAHs in a compost-DOM system was higher than that in a soil-DOM system. This could be explained as functional group differences of two DOM types. 相似文献
109.
Effects of salinity and organic matter on the partitioning of perfluoroalkyl acid (PFAs) to clay particles 总被引:1,自引:0,他引:1
The influence of salinity and organic matter on the distribution coefficient (K(d)) for perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in a brackish water-clay system was studied. The distribution coefficients (K(d)) for PFAs onto inorganic clay surfaces increased with salinity, providing evidence for electrostatic interaction for the sorption of PFAs, whereas the relationship between K(d) and organic carbon content (f(oc)) suggested that hydrophobic interaction is the primary driving force for the sorption of PFAs onto organic matter. The organic carbon normalized adsorption coefficient (K(oc)) of PFAs can be slightly overestimated due to the electrostatic interaction within uncoated inorganic surfaces. In addition, the dissolved organic matter released from coated clay particles seemed to solvate PFA molecules in solution, which contributed to a decrease in K(d). A positive relationship between K(d) and salinity was apparent, but an empirical relationship for the 'salting-out' effect was not evident. The K(d) values of PFAs are relatively small compared with those reported for persistent organic pollutants. Thus, sorption may not be a significant route of mass transfer of PFAs from water columns in estuarine environments. However, enhancement of sorption of PFAs to particulate matter at high salinity values could evoke potential risks to benthic organisms in estuarine areas. 相似文献
110.
我国自然灾害时空分布及其粮食风险评估 总被引:6,自引:0,他引:6
分析了旱灾、水灾、风雹灾、霜冻灾、台风灾和农业病虫害、草害、鼠害8种自然灾害的时空分布情况,计算了其造成的历年粮食减产量,并在此基础上评估2020年自然灾害对粮食产量的影响。结果表明,2020年不同自然灾害对我国各省粮食生产的影响程度不同。旱灾风险区集中在我国北方地区,分布在黄淮海区、西北区等;涝灾风险区集中在我国南方地区,分布在长江中下游区等;风雹灾风险区对我国粮食产量影响相对较小,主要分布在新疆和青海;台风灾风险区集中在我国南方沿海地区;农业病虫害风险区集中在我国的南方地区,分布在华南沿海区和西南区等;而霜冻灾、农业草害、鼠害对粮食生产的影响范围和影响程度较小。 相似文献