全文获取类型
收费全文 | 1303篇 |
免费 | 165篇 |
国内免费 | 289篇 |
专业分类
安全科学 | 260篇 |
废物处理 | 57篇 |
环保管理 | 224篇 |
综合类 | 763篇 |
基础理论 | 172篇 |
污染及防治 | 105篇 |
评价与监测 | 40篇 |
社会与环境 | 35篇 |
灾害及防治 | 101篇 |
出版年
2024年 | 6篇 |
2023年 | 25篇 |
2022年 | 47篇 |
2021年 | 49篇 |
2020年 | 56篇 |
2019年 | 47篇 |
2018年 | 44篇 |
2017年 | 41篇 |
2016年 | 50篇 |
2015年 | 70篇 |
2014年 | 73篇 |
2013年 | 87篇 |
2012年 | 106篇 |
2011年 | 108篇 |
2010年 | 81篇 |
2009年 | 90篇 |
2008年 | 62篇 |
2007年 | 95篇 |
2006年 | 83篇 |
2005年 | 76篇 |
2004年 | 64篇 |
2003年 | 54篇 |
2002年 | 46篇 |
2001年 | 43篇 |
2000年 | 42篇 |
1999年 | 31篇 |
1998年 | 31篇 |
1997年 | 29篇 |
1996年 | 30篇 |
1995年 | 29篇 |
1994年 | 18篇 |
1993年 | 14篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1984年 | 2篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有1757条查询结果,搜索用时 31 毫秒
431.
本文讨论了将硫酸亚铁剂量计和铜-铁剂量计用于强脉冲混合辐射场测定的实验设计,利用直径220毫米的聚乙烯球,将硫酸亚铁剂量计的快中子响应降低到20%以下,由它和完全暴露在中子、γ混合场中的硫酸亚铁剂量计响应之差,测量中子吸收剂量。这种方法两次实际用于强脉冲混合辐射场中子、γ吸收剂量测量,得到的结果和热释光剂量计、固体径迹探测器的测量结果进行了比较,在±25%的误差范围内一致 相似文献
432.
Lee H. MacDonald 《Journal of the American Water Resources Association》1993,29(3):357-368
ABSTRACT: Recent assessments have emphasized the lack of a field and laboratory component in hydrologic education at the university level. Consequences of this lack include: (1) an unwarranted faith in published data; (2) lack of appreciation for the spatial and temporal variability of most hydrologic processes; (3) lack of appreciation for the difficulty of collecting good quality field data; (4) an inability to design and execute projects to collect field data; (5) a lack of field experience which can be applied when confronted with different problems or new environments; (6) an inability to evaluate published materials or models against “field reality;” (7) an excessive reliance on, and trust in, theoretical or conceptual models; and (8) reduced potential for lifelong learning through observation and analysis. Field courses need not be costly or difficult, but the instructor must be willing to adapt to the uncertainty and problems associated with field measurements. A recently updated course on watershed measurements at Colorado State University illustrates the type of field courses which can be developed if there is the necessary commitment and flexibility. The lack of a current text can be overcome by assembling selected portions of existing government documents, and a sample bibliography is included. 相似文献
433.
Jay R. Stauffer Kenneth L. Dickson John Cairns 《Journal of the American Water Resources Association》1974,10(5):860-876
ABSTRACT. Studies were conducted to determine the distribution of fish in the New and East Rivers in relation to thermal discharges from Appalachian Power Company's fossil fuel plant at Glen Lyn, Virginia. Over 15,300 specimens representing 41 species were collected with seines, electrogear and rotenone at six sampling locations from February, 1973 to October 1973. Sampling frequency was designed to evaluate the effects of ambient temperature upon preferred temperature. Diversity indices were calculated for each location. There was a slight decrease in the diversity indices for those stations located in the thermal discharge. Condition coefficients calculated for Notropis albeolus Jordan, Notropis rubellus Aqasaiz, Notropis spilopterus Cope, Ictalurus punctatus Rafinesque, and Etheostoma blennioides Rafuesque were found to be significantly (p =.05) lower in the thermal discharge for all species tested except E. blennioides. Temperatures were plotted against frequency of capture to determine a particular species temperature selection from field data and indicated that: (1) Some species avoided high temperatures (i.e., Curnpostoma anomalum Rafuesque). (2) Some species were attracted to high temperatures (i.e., Ictalurus punctatus). (3) Some species distribution was not effected by temperatures (i.e., Notropis spilopterus). 相似文献
434.
J. A. Carfrae L. J. Sheppard J. A. Raven I. D. Leith W. Stein A. Crossley M. Theobald 《Water, Air, & Soil Pollution: Focus》2004,4(6):229-239
This paper reports data from a field study investigating the impacts of elevated ammonia (NH3) deposition on Calluna vulgaris growing on an ombrotrophic peat bog in S.E. Scotland. Shoot extension, foliar N concentrations, chlorophyll concentration and chlorophyll fluorescence were measured during the second growing season of exposure to a gradient of ammonia concentrations. Results indicate that NH3 increases growth between 150–200 kg N ha–1y–1 cumulative deposition. Foliar N content increased significantly in response to NH3 cumulative deposition up to 400 kg N ha–1 y–1 whereas chlorophyll a content significantly decreased. Measurements of Fv/Fm suggest that although NH3 exposure altered the growth and reduced chlorophyll a, the efficiency of photosystem II was insensitive to NH3-N deposition at this stage. 相似文献
435.
436.
城市地下水流场人工调控与减灾方案 总被引:2,自引:1,他引:1
以郑州市为例,针对城市区域长期过量开采地下水导致的一系列严重的环境地质灾害,诸如地下水水位持续下降形成区域地下水降落漏斗并不断扩张、含水层疏干、供水井吊泵、泉水断流、地下建筑工程浸没、地面沉降和塌陷等,探讨了城市地下水流场人工调控的减灾方案。建立了地下水系统的准三维动态数值仿真模型,以非均质各向同性渗流模型仿真地下水流,用不规则三角网格有限差分法求解了三维数值仿真模型。先解逆问题反求参数,再解正问题计算地下水各项资源量,数值仿真预报地下水渗流场至1998年。在此基础上,通过地下水渗流场的宏观调控与优化管理,使研究区内不合理开采地下水资源所引发的环境灾害减小到最低程度,为郑州市的环境减灾工作提供了科学依据。 相似文献
437.
438.
439.
查清了冀东油田废水池分布和分析了废水水质,提出了废井回灌、集中处理后回灌或回注、用废水处理机现场处理后回注或回灌等三种处理方案。通过室内、外试验论证了废水和废水池废泥治理方法,在采油所产生的含油污水实现全部回注不外排的基础上,再加上钻井废水不外排处理,从此做到了防治环境污染。 相似文献
440.
油气田废水中石油类物质测定问题的探讨 总被引:5,自引:0,他引:5
本文针对油气田废水复杂多样的特点,对石油类物质测定方法的选择;标准油品的选定以及难萃取样品的处理方法等监测技术问题进行了探讨,旨在提高监测数据的准确性及可靠性。 相似文献