全文获取类型
收费全文 | 1206篇 |
免费 | 127篇 |
国内免费 | 350篇 |
专业分类
安全科学 | 115篇 |
废物处理 | 90篇 |
环保管理 | 169篇 |
综合类 | 731篇 |
基础理论 | 204篇 |
污染及防治 | 206篇 |
评价与监测 | 69篇 |
社会与环境 | 38篇 |
灾害及防治 | 61篇 |
出版年
2024年 | 5篇 |
2023年 | 18篇 |
2022年 | 22篇 |
2021年 | 28篇 |
2020年 | 36篇 |
2019年 | 40篇 |
2018年 | 35篇 |
2017年 | 31篇 |
2016年 | 70篇 |
2015年 | 78篇 |
2014年 | 65篇 |
2013年 | 98篇 |
2012年 | 122篇 |
2011年 | 96篇 |
2010年 | 84篇 |
2009年 | 84篇 |
2008年 | 69篇 |
2007年 | 76篇 |
2006年 | 105篇 |
2005年 | 48篇 |
2004年 | 50篇 |
2003年 | 64篇 |
2002年 | 49篇 |
2001年 | 51篇 |
2000年 | 42篇 |
1999年 | 36篇 |
1998年 | 29篇 |
1997年 | 24篇 |
1996年 | 20篇 |
1995年 | 19篇 |
1994年 | 15篇 |
1993年 | 14篇 |
1992年 | 12篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
排序方式: 共有1683条查询结果,搜索用时 171 毫秒
841.
J. Marshall Baker John E. Teggins John W. Hoffman 《Journal of the American Water Resources Association》1971,7(6):1246-1249
Trace quantities of copper (II) ion can be found in natural water as waste products from industrial, mining, and agricultural operations. Because low concentrations of copper can be toxic to plant life, many workers have devised methods of analysis for this metal in water. These methods require expensive equipment and skilled technicians. The described study illustrates a simple method in which copper (II) ion is concentrated by a batch ion exchange technique and estimated colorimetrically after formation of the blue triethylenetetramine complex. Using the visible absorption peak of the complex at 600 nm it was possible to obtain accurate estimations of original copper concentrations in the range 0.5-3 ppm. Using the complex absorption peak at 260 nm in the ultra-violet region of the spectrum increased the sensitivity by a factor of twenty. Because of the dependence of the complex formation reaction on solution acidity it is possible to optimize conditions for the detection of copper (II) in the presence of other metal ions. This type of method, which could be extended to the analysis of other metal ions, could be performed by a relatively unskilled technician under field conditions. 相似文献
842.
Evaluating the characteristics of a set of sites as potential scientific research reserves is an example of land suitability
assessment. Suitability in this case is based upon multiple criteria, many of which can be linguistically imprecise and often
incompatible. Fuzzy logic is a useful method for characterizing imprecise suitability criteria and for combining criteria
into an overall suitability rating. The Ecosystem Management Decision Support software combined a fuzzy logic knowledge base
we developed to represent the assessment problem with a GIS database providing site-specific data for the assessment. Assessment
of sites as a potential natural reserve for the new University of California campus at Merced demonstrates the benefits of
fuzzy suitability assessment. The study was conducted in three stages of successively smaller assessment regions with increasingly
fine spatial resolution and specificity of criteria. Several sites were identified that best satisfy the suitability criteria
for a reserve to represent vernal pool habitat. 相似文献
843.
Hector D. Rivera‐Ramirez Glenn S. Warner Frederick N. Scatena 《Journal of the American Water Resources Association》2002,38(3):693-704
ABSTRACT: An analysis of hydrograph recessions and rainfall data was performed to estimate the recession constants for two watersheds in the Luquillo mountains of Puerto Rico. To account for seasonal rainfall patterns, the data were grouped into dry and wet seasons. Sets of three Master Recession Curves (MRC) per season for each watershed were developed: one using the Matching Strip Method (MS) and two using variations of the Correlation Method (CM). These variations were the envelope line (CME) and the least squares regression (CMR). Other regression based analytical expressions that consider the streamflow recession as an autore‐gressive or an integrated moving average process were also applied. The regression based methods performed consistently better than the graphical ones and they proved to be faster, easier, and less subjective. The recession constants from these methods were then used to estimate the time it would take the streamflow to reach the critical Q99 flow duration. Based on this study, once the streamflow reaches Q90, water managers have 6 to 12 days warning before streamflow reaches critical levels. 相似文献
844.
从1972年原国家地震局南京地震大队与原国家地震局工程力学研究所合作筹建长江大桥强震观测台网起至今,江苏省的强震观测已经走过了30年的路程。 30年中,江苏强震台网在1974年溧阳地震、 1983年菏泽地震和1990年常熟地震中获得的有科学价值的地震记录,为大型桥梁空间动力性质的分析提供了实证资料,也为中国东部深井地震性质等重要科学问题的研究提供了实证资料。 江苏省地震局的科技人员还进行了大量与强震观测相关的科研工作。 至今,在江苏省及邻近地区已形成了固定观测与流动观测相结合的强震观测台网。 本文简要回顾了江苏强震观测30年历程,并展望了未来发展的前景。 相似文献
845.
基于GIS工业危险源和隐患控制及应急调控技术的应用研究 总被引:6,自引:6,他引:6
笔者把面向对象方法及地理信息系统 (GIS)的技术应用于工业危险源与隐患控制及其应急调控技术中。介绍了面向对象的工业危险源、隐患控制及应急调控地理信息系统的功能、特点、开发环境以及设计与系统实现 ,旨在研究和探索更加完善和科学的现代化安全管理模式 相似文献
846.
在强震区进行投资应注意的几个问题 总被引:2,自引:0,他引:2
在强震区进行投资时,除要考虑一般经济环境下的投资风险外,还要考虑特殊自然环境条件下的风险.区域的地震危险性、自然环境危害性和经济运行安全性都是在强震区投资活动中应综合考虑的因素,文中就如何控制强震区的投资风险提出了建议. 相似文献
847.
848.
姚淑霞 《中国环境管理干部学院学报》2004,14(1):26-27
本实验通过对比实验方法,研制了一种具有优良耐腐蚀性能与机械性能的聚苯乙烯树脂溶剂型可剥防锈塑料,该产品采用废弃泡沫为主要成膜物质,即解决了白色垃圾问题,实现了废物利用,又解决了钢铁件的防锈问题。对该产品进行性能测试,所得到的产品膜层光亮、韧性好,易于涂施、流平性好。 相似文献
849.
本文分析了宁南山区农业生产条件和存在的问题,认为宁南山区农业资源十分丰富,只要合理开发利用,宁南山区必将成为我区油料、大豆、畜产品的生产基地,并相应地提出了加速开发宁南山区农业资源的措施。 相似文献
850.
Krishan P. Singh 《Journal of the American Water Resources Association》1990,26(6):901-911
ABSTRACT: In Illinois, a procedure has been developed to derive unit hydrographs for generating 100-year and probable maximum flood hydrographs, on the basis of 11 parameters that define the hydrograph shape very well. Regional regressions of these parameters with basin factors show very high correlation. Thus satisfactory values of parameters can be determined for ungaged areas or those with a few years' record. The nonlinearity in unit hydrographs derived from usual floods is largely attributed to mixing within-channel and overbank-flow flood events. To minimize the effects of nonlinearity and to derive unit hydrographa suitable for calculating spillway design floods, use of the proposed method of developing such hydrographs is recommended. 相似文献