全文获取类型
收费全文 | 427篇 |
免费 | 3篇 |
国内免费 | 3篇 |
专业分类
安全科学 | 18篇 |
废物处理 | 11篇 |
环保管理 | 95篇 |
综合类 | 102篇 |
基础理论 | 82篇 |
污染及防治 | 81篇 |
评价与监测 | 22篇 |
社会与环境 | 15篇 |
灾害及防治 | 7篇 |
出版年
2022年 | 4篇 |
2019年 | 4篇 |
2018年 | 8篇 |
2017年 | 4篇 |
2016年 | 12篇 |
2015年 | 6篇 |
2014年 | 5篇 |
2013年 | 36篇 |
2012年 | 17篇 |
2011年 | 8篇 |
2010年 | 11篇 |
2009年 | 10篇 |
2008年 | 14篇 |
2007年 | 13篇 |
2006年 | 15篇 |
2005年 | 12篇 |
2004年 | 7篇 |
2003年 | 12篇 |
2002年 | 18篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 10篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1988年 | 3篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1982年 | 3篇 |
1979年 | 3篇 |
1968年 | 3篇 |
1964年 | 3篇 |
1962年 | 3篇 |
1961年 | 4篇 |
1960年 | 6篇 |
1959年 | 3篇 |
1958年 | 5篇 |
1957年 | 7篇 |
1955年 | 3篇 |
1941年 | 5篇 |
1939年 | 6篇 |
1935年 | 3篇 |
1922年 | 3篇 |
排序方式: 共有433条查询结果,搜索用时 281 毫秒
121.
122.
Wilhelm Ludwig 《Die Naturwissenschaften》1937,25(28):459-460
123.
F.L. Ludwig R.C. Sandys A.E. Moon 《Journal of the Air & Waste Management Association (1995)》2013,63(6):499-504
Three separate mathematical models were combined to calculate the changes in carbon monoxide (CO) concentrations that might result from traffic engineering changes. The three models used were: (1) The Dynamic Highway Transportation model (DHTM) which relates traffic flow patterns to physical parameters and traffic signal characteristics of a network; (2) an emission model that predicts CO emissions from traffic flow parameters such as number of stops, idling time, etc; and (3) the APRAC-1A urban diffusion model which calculates CO concentrations from source distributions and meteorological factors. The composite model was applied to traffic in downtown Chicago for a specific set of meteorological conditions. Results are compared for two traffic signal control schemes. In those blocks where concentrations were highest, the model indicates a 20% reduction is possible through improved traffic signal controls. The model should be useful for testing other traffic control measures. 相似文献
124.
Jef Van Meensel Ludwig Lauwers Guido Van Huylenbroeck 《Journal of environmental management》2010,91(11):2370-2377
Reducing nitrogen emission from livestock production is usually perceived as costly. Nevertheless, production process related measures addressing the transformation of input(s) into output(s) may result in a cost-saving reduction of nitrogen emission. This paper explores the separate and combined use of traditional key performance indicators and an environmentally adjusted Data Envelopment Analysis (DEA) to reveal firm-specific cost-saving mechanisms for pig-finishing farms. Traditional key performance indicators are easy to communicate but have shortcomings when assessing benchmarks for comparative farm analysis. The environmentally adjusted DEA decomposes both cost and environmental efficiencies into technical and allocative efficiency components, separating the physical production analysis from price and nutrient content information. DEA makes efficiency benchmarks and improvement paths explicit, but the practical value of such efficiency scores is low. This paper proposes to take advantage of both methods: concrete benchmarks and eligible improvement paths are assessed using frontier methods, while the decision variables that steer farmers towards changes are described in terms of traditional key performance indicators. This leads to an improved diagnosis that is easy to communicate to farmers and may therefore facilitate decision support. Our pig-finishing case study shows that farms can achieve economic-environmental win–win situations through improving technical, cost allocative and cost efficiencies, which are mainly driven by feed conversion. Less technical efficient farms are found to require a lower delivery weight in order to minimize costs, which shows the farm-specificity of economic-environmental improvement advice. 相似文献
125.
126.
Ludwig A. Hothorn Makoto Hayashi Dirk Seidel 《Environmental and Ecological Statistics》2000,7(1):27-42
The objective of mutagenicity assays in regulatory toxicology is the decision on non-mutagenicity or mutagenicity. An inherent problem of statistical tests is the possibility of false decisions, i.e., a mutagenic substance will be falsely labeled as non-mutagenic or a non-mutagenic substance will be falsely labeled as mutagenic. These probabilities of false negative (consumer's risk=type II error) and/or false positive decision (producer's risk=type I error) can be limited by using suitable testing procedures as well as a design including an appropriate positive control. Using the proof of hazard concept the well-known many-to-one procedures with total order restriction for increasing effect differences are used, while using the proof of safety concept procedures on equivalence with total order restriction are discussed. Both approaches are demonstrated on a real data example. 相似文献
127.
Microbial diversity and spatial distribution of the diversity within tissue of the marine sponge Tethya californiana was analyzed based on 16S rRNA gene sequences. One candidate division and nine bacterial phyla were detected, including members
of all five subdivisions of Proteobacteria. Moreover, chloroplast-derived Stramenopiles- and Rhodophyta-affiliated 16S rRNA gene sequences were found and Stramenopiles represented the most abundant clones (30%) in the clone library. On the phylum-level, the microbial fingerprint of T. californiana showed a similar pattern as its Mediterranean relative T. aurantium. An interesting difference was that Cyanobacteria that were abundantly present in T. aurantium were not found in T. californiana, but that the latter sponges harbored phototrophic Stramenopiles instead. Surprisingly, the phototrophic microorganisms were evenly distributed over the inner and outer parts of the sponge
tissue, which implies that they also reside in regions without direct light exposure. The other phyla were also present in
both the outer cortex and the mesohyl of the sponges. These results were confirmed by analysis on the operational taxonomic
unit level. This leads to the conclusion that from a qualitative point of view, spatial distribution of microorganisms in
T. californiana tissue is quite homogeneous. Thirty-two percent of the operational taxonomic units shared less than 95% similarity with any
other known sequence. This indicates that marine sponges are a rich source of previously undetected microbial life. 相似文献
128.
Weissflog L Krueger G Elansky N Putz E Lange CA Lisitzina L Pfennigsdorff A Kotte K 《Chemosphere》2006,65(6):975-980
Artemisia lerchiana is a wormwood species of the Central Asian steppe regions, where it completely cover whole areas. For the first time it was possible to show through field experiments that C(1)/C(2) halocarbons (VCHCs), such as chloroform (CHL), tetrachloroethene (PER) and hexachloroethane (HEX), can be taken up by test plants of the species A. lerchiana via the soil/root pathway and metabolised inter alia into trichloroacetic acid (TCA) under semi-aride conditions. At the same time, chlorophyll a fluorescence measurements carried out on the test plants revealed a phytotoxic influence on plant vitality (max. decline in vitality of 52% with application of CHL) and less efficient energy flows in the photosynthesis mechanism of the A. lerchiana test plants. The authors examine possible links between the simultaneous appearance of VCHCs and additional drought stress in the acceleration of desertification processes. 相似文献
129.
130.
Kathleen M. Beatty Harvey Doerksen John C. Pierce 《Journal of the American Water Resources Association》1978,14(2):394-403
ABSTRACT: The traditional strong role of interest groups in water resources policy making has been modified recently by the introduction of many environmental groups. The new groups differ from traditional groups in their relatively modest resources and their relative lack of access to traditional decision points. This paper examines the extent to which the new groups differ in their perceptions of the effectiveness of tactics and in their use of tactics, taking into account group resources and group access to decision makers. 相似文献