全文获取类型
收费全文 | 915篇 |
免费 | 87篇 |
国内免费 | 215篇 |
专业分类
安全科学 | 80篇 |
废物处理 | 59篇 |
环保管理 | 68篇 |
综合类 | 476篇 |
基础理论 | 164篇 |
环境理论 | 1篇 |
污染及防治 | 211篇 |
评价与监测 | 71篇 |
社会与环境 | 55篇 |
灾害及防治 | 32篇 |
出版年
2024年 | 3篇 |
2023年 | 21篇 |
2022年 | 63篇 |
2021年 | 62篇 |
2020年 | 58篇 |
2019年 | 56篇 |
2018年 | 41篇 |
2017年 | 61篇 |
2016年 | 50篇 |
2015年 | 61篇 |
2014年 | 55篇 |
2013年 | 89篇 |
2012年 | 68篇 |
2011年 | 70篇 |
2010年 | 73篇 |
2009年 | 55篇 |
2008年 | 53篇 |
2007年 | 43篇 |
2006年 | 38篇 |
2005年 | 36篇 |
2004年 | 36篇 |
2003年 | 32篇 |
2002年 | 26篇 |
2001年 | 12篇 |
2000年 | 8篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有1217条查询结果,搜索用时 187 毫秒
991.
Iesce MR Cermola F Graziano ML Montella S Di Gioia L Isidori M 《Environmental science and pollution research international》2004,11(4):222-226
BACKGROUND: The photolysis of pesticides is of high current interest since light is one of the most important abiotic factors which are responsible for the environmental fate of these substances and may induce their conversion into noxious products. The action of light can also be mediated by oxygen and synthetic or naturally occurring substances which act as sensitizers. Our objective in this study was to investigate the photochemical behaviour of the systemic fungicide furalaxyl in the presence of oxygen and various sensitizers, and to compare the toxicity of the main photoproduct(s) to that of the parent compound. Previous reports on the direct photolysis of the pesticide demonstrated a very slow degradation and the only identified photoproducts were N-2,6-xylyl-D,L-alaninare and 2,6-dimethylaniline. METHODS: Solutions of furalaxyl in CH3CN were photooxygenate using a 500W high-pressure mercury lamp (through a Pyrex glass filter, lambda>300 nm) or a 650W halogen lamp or sunlight and the proper sensitizer. When sunlight was used, aqueous solutions were employed. The photodegradation was checked by NMR and/or GC-MS. The photoproducts were spectroscopically evidenced and, when possible, isolated chromatographically. Acute toxicity tests were performed on the rotifer Brachionus calyciflorus, the crustacean cladoceran Daphnia magna and the anostracan Thamnocephalus platyurus, while chronic toxicity tests (sublethal endpoints) comprised a producer, the alga Pseudokirchneriella subcapitata and the crustacean Ceriodaphnia dubia, as a consumer. RESULTS AND DISCUSSION: In the presence of both oxygen and sensitizer, furalaxyl underwent rapid photochemical transformations mainly to N-disubstituted formamide, maleic anhydride and a 2(5H)-furanone derivative. The formation of these products was rationalized in terms of a furan endoperoxide intermediate derived from the reaction of furalaxyl with active dioxygenated species (singlet oxygen, superoxide anion or ground state oxygen). The 2(5H)-furanone exhibited a higher toxicity than the parent compound. CONCLUSION: This work reports the first data on the photosensitized oxygenation of furalaxyl with evidence of the high tendency of the pesticide to undergo photodegradation under these conditions leading, among other things, to a 2(5H)-furanone, which is more toxic than the starting furalaxyl towards aquatic organisms. RECOMMENDATIONS AND OUTLOOK: Investigation highlights that the photolytic fate of a pesticide, although quite stable to direct photoreaction due to its low absorption of solar radiation at ground level, can be significantly influenced in the environment by the presence of substances with energy or electron-transfer properties as natural dyes, e.g. chlorophyll, or synthetic pollutants, e.g. polycyclic aromatic hydrocarbons (PAH). 相似文献
992.
煤矿职业安全与健康对经济的影响研究 总被引:1,自引:3,他引:1
煤矿职业安全与健康问题不但直接危害劳动者的生命安全与其家庭幸福,还对社会、经济发展和家庭造成巨大影响。笔者在对世界职业安全与健康状况分析基础上,重点分析了我国煤矿安全事故对经济发展的影响,并提出了迅速扭转煤矿安全生产的严峻形势及改善现状的相关对策:从借鉴国外先进经验;完善安全监管机制;维护员工合法权益;坚持以人为本,培育煤矿安全文化;落实煤矿安全生产主体责任;加大科技创新,安全投入等途径,不断提高煤矿职业安全与健康水平,建设本质安全型煤矿,大幅度降低伤亡事故发生。 相似文献
993.
通过分析在进行建设项目竣工环境保护验收监测过程中选用标准的重要性和存在的问题,提出应按照国家的新要求进行标准的选用,并对实际竣工验收监测中遇到的选用标准问题提出了解决的办法。 相似文献
994.
介绍采用自带PID(比例积分微分控制器)功能的变频器恒压供水系统的工作原理、控制系统设计及功能。 相似文献
995.
996.
Ca~(2+)、Al~(3+)对聚丙烯酰胺在高岭土絮凝过程中作用的影响 总被引:4,自引:0,他引:4
在实验条件下,Ca~(2+)、Al~(3+)离子对高岭土的絮凝过程有不利影响,且pH越高Ca~(2+)的影响越大,pH越低,Al~(3+)的影响越大.运用分子轨道(MO)理论、溶液化学计算、电子探针测试等手段,研究探讨了其作用机理.认为在酸性和中性范围内,Ca~(2+)、Al~(3+)离子及它们的羟基络合正离子与聚丙烯酰胺之间的相互作用造成后者分子链发生卷曲,导致絮凝效果下降;而在pH>9范围内,Ca~(2+)、Al~(3+)的氢氧化物沉积在高岭土表面,阻碍或抑制了聚丙烯酰胺与高岭土之间的氢键作用. 相似文献
997.
为探究MBBR泥膜复合硝化系统内泥膜竞争关系,通过小试试验研究了水处理过程中常规因素(污泥浓度、DO、温度、C/N)对MBBR泥膜复合系统硝化效果的影响,分析了系统内污泥容积负荷和移动床生物膜反应器(MBBR,Moving-Bed Biofilm Reactor)生物膜容积负荷变化趋势,进而得出泥膜竞争规律.结果表明,MBBR泥膜复合系统容积负荷均大于单一污泥或MBBR生物膜系统的容积负荷.在一定范围内,污泥浓度、DO、温度与MBBR泥膜复合系统容积负荷呈现正相关,且系统内活性污泥在与MBBR生物膜在竞争DO和基质时优势明显,而MBBR生物膜则具有更强的耐低温能力.进水C/N与MBBR泥膜复合系统硝化负荷呈负相关,且活性污泥在应对进水C/N过高时较MBBR生物膜更具优势,MBBR的“镶嵌”则强化了系统SND效果.微生物群落变化显示MBBR泥膜复合系统内的硝化细菌优势菌属为Nitrospira,且悬浮载体生物膜对其富集能力明显高于活性污泥. 相似文献
998.
999.
1000.
Amarjot Kaur Loredana Di Consiglio Ganapati P. Patil Charles Taillie 《Environmental and Ecological Statistics》1995,2(3):239-269
In environmental assessment and monitoring, a primary objective of the investigator is to describe the changes occurring in the environmentally important variables over time. Propagation functions have been proposed to describe the distributional changes occurring in the variable of interest at two different times. McDonald et al. (1992, 1995) proposed an estimator of propagation function under the assumption of normality. We conduct a detailed sensitivity analysis of inference based on the normal model. It turns out that this model is appropriate only for small departures from normality whereas, for moderate to large departures, both estimation and testing of hypothesis break down. Non-parametric estimation of the propagation function based on kernel density estimation is also considered and the robustness of the choice of bandwidth for kernel density estimation is investigated. Bootstrapping is employed to obtain confidence intervals for the propagation function and also to determine the critical regions for testing the significance of distributional changes between two sampling epochs. Also studied briefly is the mathematical form and graphical shape of the propagation function for some parametric bivariate families of distributions. Finally, the proposed estimation techniques are illustrated on a data set of tree ring widths. 相似文献