全文获取类型
收费全文 | 426篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
安全科学 | 7篇 |
废物处理 | 16篇 |
环保管理 | 44篇 |
综合类 | 232篇 |
基础理论 | 43篇 |
污染及防治 | 72篇 |
评价与监测 | 16篇 |
社会与环境 | 5篇 |
出版年
2020年 | 4篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 7篇 |
2014年 | 5篇 |
2013年 | 18篇 |
2012年 | 10篇 |
2011年 | 16篇 |
2010年 | 12篇 |
2009年 | 4篇 |
2008年 | 14篇 |
2007年 | 10篇 |
2006年 | 11篇 |
2005年 | 7篇 |
2004年 | 6篇 |
2003年 | 8篇 |
2000年 | 7篇 |
1999年 | 4篇 |
1996年 | 4篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1983年 | 5篇 |
1981年 | 4篇 |
1977年 | 6篇 |
1965年 | 8篇 |
1963年 | 4篇 |
1962年 | 7篇 |
1961年 | 5篇 |
1960年 | 6篇 |
1959年 | 7篇 |
1958年 | 4篇 |
1957年 | 12篇 |
1956年 | 7篇 |
1955年 | 8篇 |
1954年 | 7篇 |
1952年 | 5篇 |
1941年 | 7篇 |
1940年 | 8篇 |
1939年 | 10篇 |
1938年 | 4篇 |
1937年 | 8篇 |
1936年 | 5篇 |
1935年 | 11篇 |
1934年 | 7篇 |
1931年 | 5篇 |
1929年 | 4篇 |
1928年 | 4篇 |
1927年 | 4篇 |
1926年 | 5篇 |
1924年 | 3篇 |
排序方式: 共有435条查询结果,搜索用时 562 毫秒
321.
322.
323.
An online air pollution forecasting system using neural networks 总被引:1,自引:0,他引:1
In this work, an online air pollution forecasting system for Greater Istanbul Area is developed. The system predicts three air pollution indicator (SO(2), PM(10) and CO) levels for the next three days (+1, +2, and +3 days) using neural networks. AirPolTool, a user-friendly website (http://airpol.fatih.edu.tr), publishes +1, +2, and +3 days predictions of air pollutants updated twice a day. Experiments presented in this paper show that quite accurate predictions of air pollutant indicator levels are possible with a simple neural network. It is shown that further optimizations of the model can be achieved using different input parameters and different experimental setups. Firstly, +1, +2, and +3 days' pollution levels are predicted independently using same training data, then +2 and +3 days are predicted cumulatively using previously days predicted values. Better prediction results are obtained in the cumulative method. Secondly, the size of training data base used in the model is optimized. The best modeling performance with minimum error rate is achieved using 3-15 past days in the training data set. Finally, the effect of the day of week as an input parameter is investigated. Better forecasts with higher accuracy are observed using the day of week as an input parameter. 相似文献
324.
325.
326.
Kristin Bunte John P. Potyondy Kurt W. Swingle Steven R. Abt 《Journal of the American Water Resources Association》2012,48(3):530-545
Bunte, Kristin, John P. Potyondy, Kurt W. Swingle, and Steven R. Abt, 2012. Spatial Variability of Pool-Tail Fines in Mountain Gravel-Bed Stream Affects Grid-Count Results. Journal of the American Water Resources Association (JAWRA) 48(3): 530-545. DOI: 10.1111/j.1752-1688.2011.00629.x Abstract: Fine sediment (<2 and <6 mm) particles underlying a 49-intersection grid placed on a streambed at 25, 50, and 75% of the wetted pool-tail width are commonly counted to assess the status and trend of aquatic ecosystems or to monitor changes in the supply of fines in mountain gravel-bed streams. However, results vary even when crews perform nearly identical procedures. This study hypothesized that spatial variability of pool-tail fines affects grid-count results and that a sampling scheme can be optimized for precision and accuracy. Grid counts taken at seven evenly spaced locations across the wetted width of 10 pool tails in a pool-riffle study stream indicated a bankward fining trend with secondary peaks of fines within the stream center. Sampling locations close to the waterlines harbored more than twice as many fines as central locations. Most of the five grid-count schemes derived from the seven sampled locations produced significantly different results. Compared with sampling at all seven locations, schemes that focus near waterlines overpredicted fines, while those that focus on the center underpredicted them. Variability of fines among pool tails was the highest within a broad band along the waterlines; hence, focusing sampling there yielded the most variable results. The scheme sampling at 25, 50, and 75% of the wetted width had the lowest precision and moderate accuracy. Accuracy and precision of grid-count results can be greatly improved by sampling at seven even-spaced locations across the pool tail. 相似文献
327.
Colleen J. Howell Kurt A. Schwabe Azizan Haji Abu Samah 《Environment, Development and Sustainability》2010,12(1):1-18
Non-timber forest products (NTFP) represent key sources of cash and subsistence income for millions of rural and indigenous
peoples living in tropical developing countries throughout the world. The current study investigates the use and significance
of NTFP within a sample of Peninsular Malaysia’s Orang Asli (indigenous people). Data collected via household surveys across
three sampling phases reveals that more than 75% of the population is actively engaged in NTFP collection. Household responses
indicate diversity in both the types and uses of products collected. NTFP collection participation, frequency of collection,
and collection reliance are found to be significantly negatively related to village proximity to the market, as well as to
income level relative to the Malaysian poverty line. When collection variables are examined by different product categories,
relationships with market access and income group are variable. Implications for different approaches to forest conservation
and rural development are discussed. 相似文献
328.
Clara M Gans O Windhofer G Krenn U Hartl W Braun K Scharf S Scheffknecht C 《Chemosphere》2011,82(8):1116-1123
The occurrence of cashmerane (DPMI), celestolide, phantolide, traesolide (ATII), galaxolide (HHCB) and tonalide (AHTN) in sewage and surface waters and their fate during wastewater treatment and anaerobic sludge digestion is investigated. AHTN and HHCB are the most important representatives and influent concentrations of 0.41-1.8 and 0.9-13 μg L−1 are observed. DPMI is detected in influent and effluent samples but in notably lower concentrations than AHTN and HHCB. Major sources of polycyclic musks are households, whereas industrial emitters seem to be of minor importance. This conclusion is supported by the analysis of selected industrial wastewaters (metal, textile and paper industry). Specific emissions of 0.36 ± 0.19 and 1.6 ± 1.0 mg cap−1 d−1 for AHTN and HHCB are calculated. Overall removal efficiencies between approx 50% and more than 95% are observed during biological wastewater treatment and removal with the excess sludge is the major removal pathway. Log KD values of 3.73-4.3 for AHTN, 3.87-4.34 for HHCB and 2.42-3.22 for DPMI are observed in secondary sludge. During sludge digestion no or only slight removal occurred. Mean polycyclic musk concentrations in digested sludge amounted to 1.9 ± 0.9 (AHTN), 14.2 ± 5.8 (HHCB), 0.8 ± 0.4 (ATII) and 0.2 ± 0.09 (DPMI) mg kg−1 dry matter. In the receiving water systems a comparable distribution as during wastewater treatment is observed. AHTN, HHCB and DPMI are detected in surface waters (ND (not detected) - < 0.04, ND - 0.32 and ND - 0.02 μg L−1) as well as AHTN and HHCB in sediments (ND - 20, ND - 120 μg kg−1). For HHCB an apparent KOC value of 4.1-4.4 is calculated for sediments. Major source for polycyclic musks in surface waters are discharges from wastewater treatment plants. For HHCB and DPMI 100% of the load observed in the sampled surface waters derive from discharges of treated wastewater. 相似文献
329.
Steinman AD Biddanda B Chu X Thompson K Rediske R 《Environmental monitoring and assessment》2007,134(1-3):177-189
Groundwater withdrawal has major economic, social, and environmental implications. In Michigan, recent legislative activity
has begun to address the issue of groundwater sustainability. However, more hydrologic data are needed to help inform policy
and legislation. A study was conducted in Mecosta County, Michigan to: (1) determine if a relationship could be established
between land use/land cover and groundwater quality; and (2) develop a conceptual model for the shallow groundwater system
of the study region. In general, groundwater quality was good, with below detection levels of E. coli, low total bacterial counts, and relatively low nutrient concentrations. No statistically significant associations were found
between the bacterial numbers and either land use or the physical/chemical attributes measured, which may be because the scale
of our spatial analysis was too coarse to detect patterns. Finer-scale, localized processes may have a greater influence on
microorganism growth and abundance than coarser-scale, regional processes in this area. Our groundwater analysis suggested
that shallow groundwater flow paths are generally consistent with regional surface water flow networks, and that shallow groundwater
levels in most of the region have fluctuated within 1–2 m over the past 30 years, with no obvious increasing or decreasing
trend. 相似文献
330.
Momcilo Markus James Angel Kurt Woolford Kexuan Wang Shailendra Singh Brian Kerschner 《Journal of the American Water Resources Association》2023,59(3):466-480
Storm frequency estimates and their temporal distributions are important in determining estimates of runoff or peak flow rates in many engineering and hydrological problems. Illinois State Water Survey Bulletin 70 has been serving as the design rainfall standard in Illinois since its publication in 1989. Although Bulletin 70 represented the best available data at the time of its publication, the standards needed to be reevaluated and updated after more than three decades and with the growing evidence of the nonstationary nature of heavy precipitation. The trends in heavy precipitation in Illinois prompted the creation of a new frequency study named Bulletin 75, providing precipitation frequencies for event durations ranging from 5 min to 10 days and for recurrence intervals ranging from 2 months to 500 years. The results are presented for the same 10 geographic sections in Illinois as in Bulletin 70 to maintain the continuity of hydrologic studies and compatibility with regulations. The primary goal of this paper is to outline some of the key methodological issues and challenges, to compare the results with the previous sources, and to highlight the effects of the changing precipitation standards on the development of amendments to existing ordinances. Lake County in Illinois, as one of the most affected urban areas with the highest change in heavy precipitation, was selected to illustrate issues related to the application of modified precipitation standards. 相似文献