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   89篇
  免费   0篇
安全科学   1篇
废物处理   2篇
环保管理   2篇
综合类   61篇
基础理论   7篇
污染及防治   11篇
评价与监测   3篇
社会与环境   2篇
  2017年   1篇
  2016年   1篇
  2014年   1篇
  2013年   6篇
  2012年   1篇
  2011年   4篇
  2010年   1篇
  2008年   6篇
  2007年   3篇
  2005年   1篇
  2003年   2篇
  2002年   2篇
  2001年   1篇
  1999年   1篇
  1993年   4篇
  1987年   1篇
  1985年   1篇
  1980年   1篇
  1977年   1篇
  1972年   1篇
  1966年   1篇
  1964年   1篇
  1962年   1篇
  1961年   2篇
  1960年   2篇
  1959年   2篇
  1957年   1篇
  1956年   1篇
  1955年   4篇
  1953年   1篇
  1952年   1篇
  1951年   1篇
  1950年   2篇
  1941年   2篇
  1940年   1篇
  1939年   1篇
  1938年   3篇
  1937年   1篇
  1934年   1篇
  1931年   3篇
  1930年   2篇
  1929年   1篇
  1927年   1篇
  1926年   4篇
  1925年   2篇
  1919年   1篇
  1918年   1篇
  1917年   1篇
  1914年   1篇
  1913年   2篇
排序方式: 共有89条查询结果,搜索用时 15 毫秒
51.
The characteristics of UV-absorbing compounds, particularly soluble phenolics, were studied in needles of 63-day-old seed-grown Scots pine (Pinus sylvestris L.) seedlings of two provenances in a UV exclusion field experiment at Pallas-Ounastunturi National Park in Finnish Lapland (68 degrees N, 270 m a.s.l.). The experiment used the following plastic filters in exclosure treatments to manipulate the spectral balance of natural irradiance: (1) 'control' (a polyethene plastic filter); (2) 'UV-B exclusion' (a clear polyester filter); and (3) 'UV-B/UV-A exclusion' (a clear acryl plate). Polyethene transmitted 89% of the ambient levels of total UV (280-400 nm), polyester transmitted 75% of the total UV, but only 0.6% of the UV-B (280-315 nm) component, while acryl plate transmitted 0.2% of UV (280-360 nm). The research also included (4) 'Ambient' plants that were not subjected to any treatment exclosures. After the 58 day UV exclusion, significant (p<0.0001) differences due to treatments were determined for a kaempferol derivative, kaempferol 3-glucoside, and a quercetin derivative, the quantities of which ranged from 0.23 to 0.45, 0.42 to 1.34 and 0.39 to 0.75 micromol g FW(-1), respectively, depending on treatment and provenance. Overall, Scots pine seedlings grown at ambient UV radiation (PAS300, Caldwell's generalized Plant Action Spectrum (PAS) normalized at 300 nm, 72 mW m(-2)) or under a control had significantly (p<0.05) higher quantities of soluble phenolics than seedlings grown under UV-B or UV-B/UV-A exclusion treatments. There were no significant differences in the quantity of soluble phenolics between the two exclosure treatments or between the two Scots pine provenances. The sums of diacylated flavonol glucosides ranging from 3.75 to 4.55 micromol g FW(-1) depending on treatment and provenance, were already present at very low UV-levels under the UV-B/UV-A exclusion treatment. The present study indicated that soluble phenolics, particularly the diacylated flavonol glucosides, may provide an effective preformed protection for young Scots pine seedlings against UV-B and UV-A radiation.  相似文献   
52.
53.
Motivated by an inconclusive debate over implications of resource scarcity for violent conflict, and common reliance on national data and linear models, we investigate the relationship between socio-ecological vulnerability and armed conflict in global drylands on a subnational level. Our study emanates from a global typology of smallholder farmers’ vulnerability to environmental and socioeconomic stresses in drylands. This typology is composed of eight typical value combinations of variables indicating environmental scarcities, resource overuse, and poverty-related factors in a widely subnational spatial resolution. We investigate the relationships between the spatial distribution of these combinations, or vulnerability profiles, and geocoded armed conflicts, and find that conflicts are heterogeneously distributed according to these profiles. Four profiles distributed across low- and middle-income countries comprise all drylands conflicts. Comparing models for conflict incidence using logit regression and receiver operator characteristic analysis based on (1) the set of all seven indicators as independent variables and (2) a single, only vulnerability profile-based variable proves that the nonlinear typology-based variable is the better explanans for conflict incidence. Inspection of the profiles’ value combinations makes this understandable: A systematic explanation of conflict incidence and absence across all degrees of natural resource endowments is only reached through varying importance of poverty and resource overuse depending on the level of endowment. These are nonlinear interactions between the explaining variables. Conflict does not generally increase with resource scarcity or overuse. Comparison with conflict case studies showed both good agreement with our results and promise in expanding the set of indicators. Based on our findings and supporting literature, we argue that part of the debate over implications of resource scarcity for violent conflict in drylands may be resolved by acknowledging and accounting for nonlinear processes.  相似文献   
54.
Evaluation of sites for the location of WEEE recycling plants in Spain   总被引:1,自引:0,他引:1  
As a consequence of new European legal regulations for treatment of waste electrical and electronic equipment (WEEE), recycling plants have to be installed in Spain. In this context, this contribution describes a method for ranking of Spanish municipalities according to their appropriateness for the installation of these plants. In order to rank the alternatives, the discrete multi-criteria decision method PROMETHEE (Preference Ranking Organisation METHod for Enrichment Evaluations), combined with a surveys of experts, is applied. As existing plants are located in North and East Spain, a significant concentration of top ranking municipalities can be observed in South and Central Spain. The method does not present an optimal structure of the future recycling system, but provides a selection of good alternatives for potential locations of recycling plants.  相似文献   
55.
Environmental Chemistry Letters - Groundwater is the main source of freshwater in the European Union, yet freshwaters are polluted by organic contaminants if contaminants are not efficiently...  相似文献   
56.
57.
58.
59.
Data in the literature suggest that confined placental mosaicism might be associated with intrauterine growth retardation. However, this association may be coincidental and due to bias of ascertainment. We therefore started a prospective study based on the cytogenetic evaluation of placentae derived from growth-retarded newborns. We further minimized possible bias by excluding those small-for-date infants displaying findings which already could explain intrauterine growth retardation (mothers who are smokers, multiple pregnancies, gestosis, dysmorphic infants). In a collection of 71 small-for-gestational age newborns, we did not see a single case of true confined placental mosaicism.  相似文献   
60.
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