全文获取类型
收费全文 | 134篇 |
免费 | 1篇 |
专业分类
安全科学 | 8篇 |
废物处理 | 1篇 |
环保管理 | 9篇 |
综合类 | 40篇 |
基础理论 | 19篇 |
污染及防治 | 37篇 |
评价与监测 | 11篇 |
社会与环境 | 8篇 |
灾害及防治 | 2篇 |
出版年
2021年 | 3篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2014年 | 6篇 |
2013年 | 9篇 |
2011年 | 5篇 |
2010年 | 7篇 |
2009年 | 8篇 |
2008年 | 6篇 |
2007年 | 5篇 |
2006年 | 2篇 |
2004年 | 7篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1964年 | 1篇 |
1962年 | 2篇 |
1961年 | 3篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1954年 | 4篇 |
1932年 | 1篇 |
1929年 | 1篇 |
1923年 | 1篇 |
1921年 | 1篇 |
排序方式: 共有135条查询结果,搜索用时 15 毫秒
41.
ABSTRACT Both because of its effectiveness and ease in use, linear programming has become progressively popular in water resources planning problems. Yet, the assumptions of linear construction costs can be misleading. Diseconomies of scale in construction can be handled by successive approximations to the cost function but problems with economies of scale yield paradoxical results when piecewise approximations are used. If significant economies of scale exist in only one facility, the solution to problems of this nature can be found using normal linear programming codes by successively adjusting the unit construction cost on that single facility to iteratively work toward the true optimal solution. 相似文献
42.
Chloe Hannan Aimee J. Palumbo Megan C. Fisher Thiel Eve Weiss 《Traffic injury prevention》2018,19(8):S84-S90
AbstractObjective: Recently developed advanced driver assistance systems (ADAS) have the potential to compensate for teen driving errors and reduce overall crash risk. To date, very limited research has been conducted on the suitability of ADAS for teen drivers—the population most likely to benefit from such systems. The opportunity for ADAS to reduce the frequency and severity of crashes involving teen drivers is hindered when there is a lack of trust, acceptance, and use of those technologies. Therefore, there is a need to study teen and parent perceptions of ADAS to help identify and overcome any potential barriers to ADAS use.Methods: A U.S. national survey was developed based on themes from previously conducted teen and parent ADAS focus groups. Survey topics included trust in ADAS, effect of ADAS on teen driver safety and driving behavior, effect of ADAS on skill development, data privacy, and cybersecurity. Responses included 5-point Likert scales and open-ended questions. The survey was managed through an online respondent panel by ResearchNow. Eligibility criteria included licensed teens (16–19 years) and parents of licensed teens. Teen and parent responses were compared using chi-square statistics in SAS 9.4.Results: Two thousand and three (teens?=?1,000; parents?=?1,003) respondents qualified for and completed the survey between September 1 and September 20, 2017. Overall, teens (72%) and parents (61%) felt that ADAS would have a positive impact on transportation. However, teens were more likely to exhibit a positive outlook on ADAS, whereas parents were more likely to have a negative outlook (P?<?.01). Teens felt that ADAS would be useful during bad weather or drowsy driving but were less concerned than parents about ADAS intervention during their own risky driving (P?<?.01). The majority of teens (65%) and parents (71%) agreed that teens should learn to drive on vehicles without ADAS, with parents being more likely to agree than teens (P?<?.01). Parents (55%) were more likely than teens (47%) to be concerned about insurance companies keeping track of teen driving data (P?<?.01). Most respondents exhibited some concern of ADAS being susceptible to hacking (57%).Conclusions: This study represents the first effort to quantify ADAS perceptions among teen drivers and their parents at the U.S. national level. These data highlight potential barriers to ADAS use among teen drivers, including a relative disinterest among teens for ADAS intervention during risky driving as well as concerns among both teens and parents that ADAS will inhibit skill development. These survey findings will help inform educational programs to accelerate fleet turnover and provide the foundation for ADAS optimization and evaluation studies among sociodemographic groups. 相似文献
43.
Altitude profiles of total chlorinated paraffins in humus and spruce needles from the Alps (MONARPOP) 总被引:1,自引:0,他引:1
Saverio Iozza Peter Schmid Rodolfo Bassan Gert Jakobi Karl-Werner Schramm Wolfgang Moche Peter Weiss Wilhelm Knoth 《Environmental pollution (Barking, Essex : 1987)》2009,157(12):3225-3231
Chlorinated paraffins (CPs) are toxic, bioaccumulative, persistent, and ubiquitously present in the environment. CPs were analyzed in humus and needle samples, which were taken within the Monitoring Network in the Alpine Region for Persistent and other Organic Pollutants (MONARPOP) at sampling sites of 7 different altitude profiles in the Alps. Gas chromatography combined with electron ionization tandem mass spectrometry (EI-MS/MS) was used for the determination of total CPs (sum of short, medium and long chain CPs). CPs were found in all samples; the concentrations varied between 7 and 199 ng g−1 dry weight (dw) and within 26 and 460 ng g−1 dw in humus and needle samples, respectively. A clear vertical tendency within the individual altitude profiles could not be ascertained. Within all altitude profiles, elevated concentrations were observed in humus samples taken between 700 and 900 m and between 1300 and 1500 m. In the needle samples no similar correlation could be observed due to higher variation of the data. 相似文献
44.
Chlorobenzenes and hexachlorocyclohexanes (HCHs) in the atmosphere of Bitterfeld and Leipzig (Germany) 总被引:1,自引:0,他引:1
Concentrations of tetrachlorobenzenes, pentachlorobenzene, hexachlorobenzene and alpha-, beta-, gamma- and delta-HCH in air and deposition were measured at three different contaminated sites in Greppin, Roitzsch (both near Bitterfeld) and Leipzig during five time intervals of 14 days in the summer months of 1998. The mean values of the chlorobenzene concentrations (gas phase and particle bound portions) over the whole sampling time were 0.11 ng/Nm3 (Leipzig), 0.17 ng/Nm3 (Roitzsch) and 0.37 ng/Nm3 (Greppin), the mean values of the HCH concentrations were 0.22 ng/Nm3 (Leipzig), 0.31 ng/Nm3 (Roitzsch) and 0.69 ng/Nm3 (Greppin). This increase of the concentration values from Leipzig over Roitzsch to Greppin indicates the influences of industrial waste sites in the Bitterfeld region on the atmospheric environment. The significantly higher values of hexachlorobenzene, alpha- and beta-HCH in Greppin are probably caused by emissions from the former chemical plant Bitterfeld-Wolfen and the landfill 'Antonie' near Greppin. Compared with literature data from other industrial impacted areas the measured air concentration and deposition values are relatively low. 相似文献
45.
46.
Mathematical modeling of competing risks often uses a single risk function for all individuals within a population. In this paper we use several specific examples to argue that such representations remain approximations until account is taken of the existence of genetic variability within and between populations, and the impact of this upon liability to disease. The extent of human genetic variability is also indicated. 相似文献
47.
48.
The theory behind,and the challenges of,conserving nature's stage in a time of rapid change 下载免费PDF全文
Joshua J. Lawler David D. Ackerly Christine M. Albano Mark G. Anderson Solomon Z. Dobrowski Jacquelyn L. Gill Nicole E. Heller Robert L. Pressey Eric W. Sanderson Stuart B. Weiss 《Conservation biology》2015,29(3):618-629
Most conservation planning to date has focused on protecting today's biodiversity with the assumption that it will be tomorrow's biodiversity. However, modern climate change has already resulted in distributional shifts of some species and is projected to result in many more shifts in the coming decades. As species redistribute and biotic communities reorganize, conservation plans based on current patterns of biodiversity may fail to adequately protect species in the future. One approach for addressing this issue is to focus on conserving a range of abiotic conditions in the conservation‐planning process. By doing so, it may be possible to conserve an abiotically diverse “stage” upon which evolution will play out and support many actors (biodiversity). We reviewed the fundamental underpinnings of the concept of conserving the abiotic stage, starting with the early observations of von Humboldt, who mapped the concordance of abiotic conditions and vegetation, and progressing to the concept of the ecological niche. We discuss challenges posed by issues of spatial and temporal scale, the role of biotic drivers of species distributions, and latitudinal and topographic variation in relationships between climate and landform. For example, abiotic conditions are not static, but change through time—albeit at different and often relatively slow rates. In some places, biotic interactions play a substantial role in structuring patterns of biodiversity, meaning that patterns of biodiversity may be less tightly linked to the abiotic stage. Furthermore, abiotic drivers of biodiversity can change with latitude and topographic position, meaning that the abiotic stage may need to be defined differently in different places. We conclude that protecting a diversity of abiotic conditions will likely best conserve biodiversity into the future in places where abiotic drivers of species distributions are strong relative to biotic drivers, where the diversity of abiotic settings will be conserved through time, and where connectivity allows for movement among areas providing different abiotic conditions. 相似文献
49.
Rohan Jain Domician Dominic Norbert Jordan Eldon R. Rene Stephan Weiss Eric D. van Hullebusch René Hübner Piet N. L. Lens 《Environmental Chemistry Letters》2016,14(3):381-386
Cadmium (Cd) is a carcinogenic metal contaminating the environment and ending up in wastewaters. There is therefore a need for improved methods to remove Cd by adsorption. Biogenic elemental selenium nanoparticles have been shown to adsorb Zn, Cu and Hg, but these nanoparticles have not been tested for Cd removal. Here we studied the time-dependency and adsorption isotherm of Cd onto biogenic elemental selenium nanoparticles using batch adsorption experiments. We measured ζ-potential values to assess the stability of nanoparticles loaded with Cd. Results show that the maximum Cd adsorption capacity amounts to 176.8 mg of Cd adsorbed per g of biogenic elemental selenium nanoparticles. The ζ-potential of Cd-loaded nanoparticles became less negative from ?32.7 to ?11.7 mV when exposing nanoparticles to an initial Cd concentration of 92.7 mg L?1. This is the first study that demonstrates the high Cd uptake capacity of biogenic elemental selenium nanoparticles, of 176.8 mg g?1, when compared to that of traditional adsorbents such as carboxyl-functionalized activated carbon, of 13.5 mg g?1. An additional benefit is the easy solid–liquid separation by gravity settling due to coagulation of Cd-loaded biogenic elemental selenium nanoparticles. 相似文献