首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   526篇
  免费   9篇
  国内免费   7篇
安全科学   12篇
废物处理   31篇
环保管理   41篇
综合类   118篇
基础理论   104篇
环境理论   2篇
污染及防治   149篇
评价与监测   48篇
社会与环境   35篇
灾害及防治   2篇
  2023年   7篇
  2022年   6篇
  2021年   17篇
  2020年   10篇
  2019年   10篇
  2018年   16篇
  2017年   17篇
  2016年   33篇
  2015年   16篇
  2014年   29篇
  2013年   46篇
  2012年   24篇
  2011年   35篇
  2010年   34篇
  2009年   24篇
  2008年   23篇
  2007年   14篇
  2006年   14篇
  2005年   14篇
  2004年   16篇
  2003年   16篇
  2002年   8篇
  2001年   5篇
  2000年   8篇
  1999年   5篇
  1998年   5篇
  1997年   3篇
  1994年   4篇
  1993年   3篇
  1989年   4篇
  1987年   5篇
  1984年   4篇
  1983年   5篇
  1975年   4篇
  1973年   3篇
  1972年   2篇
  1971年   2篇
  1970年   2篇
  1969年   3篇
  1968年   2篇
  1967年   5篇
  1966年   3篇
  1964年   2篇
  1963年   2篇
  1962年   4篇
  1959年   2篇
  1957年   3篇
  1956年   2篇
  1955年   4篇
  1952年   2篇
排序方式: 共有542条查询结果,搜索用时 62 毫秒
51.
52.
Summer dormancy in edible dormice (Glis glis) without energetic constraints   总被引:2,自引:1,他引:1  
Average longevity in free-living edible dormice (Glis glis) can reach 9 years, which is extremely high for a small rodent. This remarkable life span has been related to a peculiar life history strategy and the rarity of reproductive bouts in these seed eaters. Most females (96%) reproduce only once or twice in their lifetime, predominantly during years of mast seeding of, e.g., beech, but entire populations can skip reproduction in years of low seed availability. Surprisingly, in non-reproductive years, large fractions of populations apparently vanished and were never captured above ground. Therefore, we determined the duration of above-ground activity, and body temperature profiles in a subset of animals, of dormice under semi-natural conditions in outdoor enclosures. We found that non-reproductive dormice returned to dormancy in underground burrows throughout summer after active seasons as short as <2 weeks. Thus, animals spent up to >10 months per year in dormancy. This exceeds dormancy duration of any other mammal under natural conditions. Summer dormancy was not caused by energy constraints, as it occurred in animals in good condition, fed ad libitum and without climatic stress. We suggest that almost year-round torpor has evolved as a strategy to escape birds of prey, the major predators of this arboreal mammal. This unique predator-avoidance strategy clearly helps in explaining the unusually high longevity of dormice.  相似文献   
53.
The recent and upcoming reforms of the Common Agricultural Policies (CAPs) aim at strengthening the multifunctional role of agriculture, acknowledging the differences in economic, environmental and social potentials within European regions. This paper presents results from an integrated assessment of existing and future policies within the framework set up in the FP6 EU project MEA-Scope. Spatial explicit procedures allow for the MEA-Scope modelling tools to provide information related to regional, environmental and socio-economics settings. The impact of different policy scenarios on structural change, land abandonment and cropping pattern of typical farms has been assessed based on linked agent-based (ABM) and Linear Programming (LP) models at regional and farm scale for two study areas. For the German case study area Ostprignitz-Ruppin (OPR), the issue of policy targeting has been addressed by relating non-commodity outputs (NCOs) to soil quality and protection status. For the Italian case study area (Mugello), changes in landscape patterns in terms of increased fragmentation or homogeneity as affected by changes in agricultural intensity have been analysed using semivariance analysis. The spatial explicit approach highlighted the relevance of case study research in order to identifying response structures and explaining policy implementation patterns.  相似文献   
54.
Learning is considered as a promising mechanism to cope with rapid environmental change. The implications of learning for natural resource management (NRM) have not been explored in-depth and the evidence on the topic is scattered across multiple sources. We provide a qualitative review of types of learning outcomes and consider their manifestations in NRM across selected empirical literature. We conducted a systematic search of the peer-reviewed literature (N = 1,223) and a qualitative meta-synthesis of included articles, with an explicit focus on learning outcomes and NRM changes (N = 53). Besides social learning, we found several learning concepts used, including policy and transformative learning, and multiple links between learning and NRM reported. We observe that the development of skills, together with a system approach involving multi-level capacities, is decisive for implications of learning for NRM. Future reviews could systematically compare how primary research applies different learning concepts and discusses links between learning and NRM changes.  相似文献   
55.
56.
Improved separations of a wide range of anions of environmental importance in scrubbers of waste incinerators were achieved by applying a Na2B4O7/NaOH composition gradient of low electrical conductivity in combination with suppressed ion chromatography. Fluoride, Acetate, Formiate and 16 other ions including Iodide could be separated within the same run in less than 20 minutes. The selective detection of small amounts of several anions in presence of excessive amounts of Chloride and Sulfate is discussed. Furtheron various adsorbents were tested for the removal of Phenol as a potential trouble shooting source in 5 ion chromatography. Depending on the analytical task and circumstances several adsorbents reveiled promising properties.  相似文献   
57.
To examine the suitability of benthic foraminifera and their test deformations as bioindicators of pollution in coastal marine environments, we studied foraminifera and metal concentrations in 72 marine sediment samples, collected from the inner shelf along the Sicilian coast (Gulfs of Palermo and Termini) and on the south-eastern coast of Lampedusa Island. These areas are characterised by different environmental conditions. On the basis of pollution sources and foraminiferal assemblages, we recognised different zones in the Gulf of Palermo. The most polluted zones showed high metal concentrations, and low diversity of benthic foraminifera with species typical of stressed environments. By contrast, the lowest polluted zones showed a high population density and the highest percentages of epiphytes. Epiphytes were abundant where a Posidonia oceanica meadow was present and decreased in the most polluted zones. Sediments of the Gulf of Termini and Lampedusa exhibited high percentages of benthic foraminifera typical of well-oxygenated waters and low concentrations of metals, with the exception of sites located near sewage outfalls and harbour areas. Furthermore, even though deformed tests are commonly known in natural stressed environmental conditions, this study shows that in the most polluted zones, benthic foraminifera were characterised by the highest percentages of deformed individuals.  相似文献   
58.
This article reports a novel, eco-friendly herbal method to synthesize Cu nanoparticles in large scales. Cu nanoparticles are an alternative to Ag and Au nanoparticles and have potential applications in many industrial areas. Many synthetic routes have been documented for the preparation of copper nanoparticles, but very few routes are eco-friendly and large-scale. We report here the preparation of Cu nanoparticles from aqueous CuSO4 using non-toxic and inexpensive materials like curd, milk, and herbal extracts such as tamarind and lemon juice as capping agents. X-ray diffraction and transmission electron microscopy show that produced particles are nanocrystalline copper 20–50 nm in size with a face-centered cubic structure. Fourier-transformed infrared spectroscopy evidences the role of organic acids in the capping process. The novelty of this work is the synthesis of Cu nanoparticles from CuSO4 without electricity and using non-toxic, cheap capping agents.  相似文献   
59.
The allelopathic potential of fescue (Festuca arundinacea Shreb.) was investigated under field and laboratory conditions. In the field, incorporation of fescue aboveground biomass into the soil provided an effective weed control as it significantly reduced both the number and the dry weight of all weed species. The effect on weeds was species specific. The reduction of the most abundant species, Picris echioides, with respect to the number of individuals and their dry weight was 67 and 45%. Fescue aboveground biomass, harvested immediately before soil incorporation, was utilized in a bioassay-oriented fractionation, aimed at identifying the compounds in the toxic extracts of the plant. While phytotoxic activity was detected for the n-butanol fraction, no activity was found for the aqueous one. Germination of an indicator species, lettuce (Lactuca sativa L.), was reduced by 33% at the higher extract concentration of 20 mg/mL, owing to the increase of the number of abnormal seedlings. The LC/MS profile of the extract revealed the presence of two alkaloids, seven flavonol glycosides, and two flavonol aglyca. Quercetin 3-O-rutinoside, isorhamnetin 3-O-rutinoside, and kaempferol 3-O-rutinoside were reported in fescue for the first time.  相似文献   
60.
Competition for space changes species’ distributions and community organization on tropical rocky shores, and the presence of secondary metabolites in the tissues of non-indigenous species may aid them in establishing and expanding their range through negative competitive interactions. The aim of this study was to describe the range of chemical substances produced by the non-indigenous cup corals Tubastraea coccinea and T. tagusensis and to test whether they varied in the field when the corals were placed in proximity to two local competitors. Cholest-5-en-3β-ol and 9-octadecanoic acid were two common secondary metabolites found in the tissues of Tubastraea. In the competition interaction experiment, necrosis was detected on the tissues of the coral Mussismilia hispida, and this species induced variation in sterol, alkaloid, and fatty acid production in Tubastraea tissues. In contrast, a sponge overgrew Tubastraea colonies. These results indicate that chemical defense may contribute to the ability of these non-indigenous corals to invade native communities.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号