全文获取类型
收费全文 | 254篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
安全科学 | 5篇 |
废物处理 | 11篇 |
环保管理 | 35篇 |
综合类 | 35篇 |
基础理论 | 62篇 |
环境理论 | 2篇 |
污染及防治 | 87篇 |
评价与监测 | 9篇 |
社会与环境 | 10篇 |
灾害及防治 | 2篇 |
出版年
2023年 | 2篇 |
2021年 | 3篇 |
2019年 | 2篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 7篇 |
2015年 | 5篇 |
2014年 | 5篇 |
2013年 | 27篇 |
2012年 | 8篇 |
2011年 | 7篇 |
2010年 | 5篇 |
2009年 | 14篇 |
2008年 | 8篇 |
2007年 | 18篇 |
2006年 | 14篇 |
2005年 | 7篇 |
2004年 | 12篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1992年 | 3篇 |
1990年 | 2篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1961年 | 1篇 |
1954年 | 3篇 |
1951年 | 1篇 |
1949年 | 1篇 |
1948年 | 2篇 |
1946年 | 1篇 |
1942年 | 1篇 |
1941年 | 1篇 |
1939年 | 2篇 |
1919年 | 1篇 |
1914年 | 1篇 |
排序方式: 共有258条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
65.
Forage fish—small, low trophic level, pelagic fish such as herrings, sardines, and anchovies—are important prey species in marine ecosystems and also support large commercial fisheries. In many parts of the world, forage fish fisheries are managed using precautionary principles that target catch limits below the maximum sustainable yield. However, there are increasing calls to further limit forage fish catch to safeguard their fish, seabird, and marine mammal predators. The effectiveness of these extra-precautionary regulations, which assume that increasing prey abundance increases predator productivity, are under debate. In this study, we used prey-linked population models to measure the influence of forage fish abundance on the population growth rates of 45 marine predator populations representing 32 fish, seabird, and mammal species from 5 regions around the world. We used simulated data to confirm the ability of the statistical model to accurately detect prey influences under varying levels of influence strength and process variability. Our results indicate that predator productivity was rarely influenced by the abundance of their forage fish prey. Only 6 predator populations (13% of the total) were positively influenced by increasing prey abundance and the model exhibited high power to detect prey influences when they existed. These results suggest that additional limitation of forage fish harvest to levels well below sustainable yields would rarely result in detectable increases in marine predator populations. 相似文献
66.
67.
Paul Jensen 《Journal of the Air & Waste Management Association (1995)》2013,63(12):1028-1034
The article reviews the current state of knowledge of noise and how people respond to noise. Sources of community noise are discussed and existing federal legislation pertaining to noise is mentioned. Methods of reducing the noise impact on communities from aircraft, surface transportation, and industrial sites are presented. Interior noise in industry, OSHA noise standards and means of controlling the noise to minimize hearing impairment are emphasized. 相似文献
68.
Andrea G. Jensen Stuart A. Batterman 《Journal of the Air & Waste Management Association (1995)》2013,63(8):995-1003
Thermal destruction capacity for commercial hazardous waste in the United States is examined to determine current and future capacity requirements. This study focuses on commercial incinerators and cement kilns burning conventional hazardous wastes. Aggregate maximum and available capacity estimates are derived using the most recent information. On a national basis, available capacity far exceeds present demand. On a regional basis, capacity appears sufficient with the exception of the California area. However, this shortfall appears insignificant given the overall capacity situation. While incineration demand may increase for solids and sludges as a consequence of Land Ban disposal restrictions and other reasons, capacity for these wastes again appears sufficient to meet current and projected demands. Thus, arguments that additional commercial incineration capacity will be needed to accommodate an expected increase in incinerable hazardous waste cannot be supported by the available information. The analysis raises concerns about the determination of realistic capacity estimates, and the lack of interaction between the capacity assurance process that documents the need for capacity and state siting processes for new waste management facilities. The excess incineration capacity shown in this paper will contribute to the successful implementation of EPA’s goal to reduce national capacity. 相似文献
69.
The acoustic behaviour of Eptesicus serotinus was investigated in the field using a 13.5-m vertical, linear microphone array that allowed for simultaneous recordings at
three different heights and for the calculation of flight altitude and distance from the array. Recordings were made at two
locations that differed in bat species diversity. E. serotinus hunted on average at an altitude of 10.7 m (±2.7) at one location and 6.8 m (±3.6) at the other location. Search signals
were 5–17 ms long depending on flight altitude, and consisted of two to three frequency-modulated harmonics. For bats flying
below 8–10 m altitude, signal duration decreased with decreasing flight altitude, whereas signal interval, terminal frequency,
peak frequency and frequency range of the first harmonic increased. Above 8–10 m flight altitude, the signal parameters were
fairly constant. The –10 dB bandwidth and duty cycle did not change with flight altitude. Source levels were calculated to
between 121 and 125 dB peSPL re 20 μPa at 10 cm. For bats flying higher than 9 m, the microphone placed 1.5 m above the ground
recorded significantly reduced signal durations and frequency ranges of the first harmonic compared to the same signals recorded
with the microphones at heights of 7 or 15 m. We caution the use of ground recordings to fully describe the echolocation signals
of high-flying bats. We demonstrate that flight altitude significantly influences the structure of sonar signals from E. serotinus.
Received: 17 May 1999 / Received in revised form: 20 September 1999 / Accepted: 25 September 1999 相似文献
70.