全文获取类型
收费全文 | 933篇 |
免费 | 104篇 |
国内免费 | 191篇 |
专业分类
安全科学 | 174篇 |
废物处理 | 21篇 |
环保管理 | 144篇 |
综合类 | 495篇 |
基础理论 | 127篇 |
环境理论 | 6篇 |
污染及防治 | 85篇 |
评价与监测 | 84篇 |
社会与环境 | 67篇 |
灾害及防治 | 25篇 |
出版年
2024年 | 2篇 |
2023年 | 19篇 |
2022年 | 15篇 |
2021年 | 27篇 |
2020年 | 26篇 |
2019年 | 38篇 |
2018年 | 37篇 |
2017年 | 40篇 |
2016年 | 34篇 |
2015年 | 40篇 |
2014年 | 44篇 |
2013年 | 82篇 |
2012年 | 87篇 |
2011年 | 88篇 |
2010年 | 54篇 |
2009年 | 66篇 |
2008年 | 46篇 |
2007年 | 62篇 |
2006年 | 54篇 |
2005年 | 46篇 |
2004年 | 31篇 |
2003年 | 33篇 |
2002年 | 35篇 |
2001年 | 39篇 |
2000年 | 23篇 |
1999年 | 35篇 |
1998年 | 20篇 |
1997年 | 12篇 |
1996年 | 15篇 |
1995年 | 13篇 |
1994年 | 15篇 |
1993年 | 15篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 11篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1971年 | 2篇 |
排序方式: 共有1228条查询结果,搜索用时 15 毫秒
91.
Irving Spiewak 《Journal of the American Water Resources Association》1971,7(4):844-855
ABSTRACT The selection of an evaporator design must reflect the balancing of captial cost (primarily in heat exchanger surface and vessels) against operating cost (primarily steam cost) to achieve minimum cost. In a conjunctive plant the tendency is to select a low-capital cost, high-operating cost plant. In addition, it is advantageous to use a high-capacity plant which needs to be operated much less of the time than a plant which is sized just at the needed rate. For example, in the study of a possible system to satisfy a future increase of 450 MGD in water supply to New York Qty, a plant of 750 MGD capacity was selected as optimum. This plant, of the advanced VTE-MSF process type, would have a performance ratio of 9 lb product/1000 Btu as compared to 10-13 normally used for base-loaded plants. Steam would be supplied by a multi-unit dual-purpose nuclear power plant. The most economical type of energy supply would be “interruptible”; the steam would be used by a low pressure turbine to generate electricity during periods of peak electrical demand but would be available to the desalting plant at other times. The low pressure turbine would be available as spinning reserve during desalting plant operation. It is estimated that the desalting plant would have a load factor of 27 per cent over its life. 相似文献
93.
介绍了锦州东港电力有限公司地震台多年来应用超低频电磁信息探索地震前兆所总结出的异常形态分别与远震、近震、地方震的对应实例,揭示了ULF电磁波异常与将要发生地震映震的一些初步规律,说明了电磁波是地震短临预报的好方法。 相似文献
94.
以战略导弹核武器系统的设计、生产、使用与维修为背景,分析了人为失误的定义、原因及分类,并根据模糊图理论,提出了一种评估人员可靠性的双向模糊图模型,并对人因工程学在战略导弹核武器系统的应用,提出了一些看法和建议。 相似文献
95.
Veiga LH Koifman S Melo VP Sachet I Amaral EC 《Journal of environmental radioactivity》2003,70(3):161-176
This paper aims to present an assessment of the environmental radiological exposure at a Brazilian area of high natural radiation and discusses the indoor radon exposure risk. A survey of inhabitant exposures arising from the inhalation of radon progeny and external gamma exposure was conducted in urban and rural areas of the Po?os de Caldas Plateau, which is recognized worldwide as a high natural radiation region. The results of this survey indicated that highest radiation exposure was restricted to the rural area of Po?os de Caldas. The radiation exposure in urban locations was quite similar to the values observed in normal background areas in some Brazilian counties. By the application of a constant relative risk model, an additional 20% in the lifetime risk of lung cancer mortality due to the exposure to radon progeny was estimated at Po?os de Caldas. It was also estimated that 16% of all lung cancer deaths at Po?os de Caldas county could be attributable to radon exposure. 相似文献
96.
20 0 1 0 1 2 6印度西北部的普杰地区发生了 7 8级强烈地震。对这次强震事件 ,利用卫星遥感监测地气系统射出长波辐射的数值产品资料 ,分析了以普杰为中心整个西亚范围内 ,事件发生前后共计 6个月的月平均辐射场的分布特征及其演变过程。发现自震前 2个月至震时当月 ,普杰地区始终是一个辐射 (热 )场的高值中心 ,震后明显消散。据此认为印度大地震有可识别的预警信息 ,提出利用卫星遥感技术及其产品 ,有可能为“突破”短临地震预报开拓出一种新的预测技术生长点 相似文献
97.
98.
J. Roger McHenry Jerry C. Ritchie Frank R. Schiebe 《Journal of the American Water Resources Association》1977,13(1):81-92
ABSTRACT: The total suspended sediment loads of four north Mississippi reservoirs were determined from measurements of concentrations of suspended sediment in a vertical profile at several locations on each reservoir made during the year. These data were combined with the stage-height and known stage-volume relationships for each reservoir in a numerical integration to determine the total suspended sediment in the water body. Total suspended sediments were estimated using the product of the suspended sediment concentration in the surface water by the appropriate reservoir volume. The averaged ratios of the estimated to measured suspended sediment loads for each reservoir exceeded 0.90. Since the concentration of suspended sediments in surface waters of north Mississippi reservoirs has been shown as highly correlated with spectral reflectance, estimating the total suspended sediment of these reservoirs using remotely sensed spectral reflectance data is possible. 相似文献
99.
I. Vigano T. Rckmann R. Holzinger A. van Dijk F. Keppler M. Greule W.A. Brand H. Geilmann H. van Weelden 《Atmospheric environment (Oxford, England : 1994)》2009,43(35):5637-5646
Recent experiments have shown that dry and fresh leaves, other plant matter, as well as several structural plant components, emit methane upon irradiation with UV light. Here we present the source isotope signatures of the methane emitted from a range of dry natural plant leaves and structural compounds. UV-induced methane from organic matter is strongly depleted in both 13C and D compared to the bulk biomass. The isotopic content of plant methoxyl groups, which have been identified as important precursors of aerobic methane formation in plants, falls roughly halfway between the bulk and CH4 isotopic composition. C3 and C4/CAM plants show the well-established isotope difference in bulk 13C content. Our results show that they also emit CH4 with different δ13C value. Furthermore, δ13C of methoxyl groups in the plant material, and ester methoxyl groups only, show a similar difference between C3 and C4/CAM plants. The correlation between the δ13C of emitted CH4 and methoxyl groups implies that methoxyl groups are not the only source substrate of CH4.Interestingly, δD values of the emitted CH4 are also found to be different for C3 and C4 plants, although there is no significant difference in the bulk material. Bulk δD analyses may be compromised by a large reservoir of exchangeable hydrogen, but no significant δD difference is found either for the methoxyl groups, which do not contain exchangeable hydrogen. The δD difference in CH4 between C3 and C4 plants indicates that at least two different reservoirs are involved in CH4 emission. One of them is the OCH3 group, the other one must be significantly depleted, and contribute more to the emissions of C3 plants compared to C4 plants. In qualitative agreement with this hypothesis, CH4 emission rates are higher for C3 plants than for C4 plants. 相似文献
100.
《环境科学学报(英文版)》2023,35(7):202-212
The excessive accumulation of potentially toxic metals (Pb and Cd) in coastal wetlands is among the main factors threatening wetland ecosystems. However, the effects of water table depth (WTD) on the risk and binding mechanisms of potentially toxic metals in sediments remain unclear. Here, sediments from different WTD obtained from a typical coastal wetland were evaluated using a newly developed strategy based on chemical extraction methods coupled with high-resolution spectroscopy. Our findings indicated that the WTD of the coastal wetland fluctuates frequently and the average enrichment factor for Pb was categorized as minor, whereas Cd enrichment was categorized as moderate. High-resolution spectroscopy techniques also demonstrated that organic functional groups and partly inorganic compounds (e.g., Fe-O/Si-O) played a vital role in the binding of Pb and Cd to surface sediments. Additionally, mineral components rather than organic groups were mainly bound to these metals in the bottom sediments. Collectively, our findings provide key insights into the potential health effects and binding characteristics of potentially toxic metals in sediments, as well as their dynamic behavior under varying sediment depths at a microscale. 相似文献