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   4187篇
  免费   29篇
  国内免费   5篇
安全科学   66篇
废物处理   155篇
环保管理   192篇
综合类   1537篇
基础理论   877篇
环境理论   9篇
污染及防治   1014篇
评价与监测   196篇
社会与环境   169篇
灾害及防治   6篇
  2022年   30篇
  2019年   40篇
  2018年   82篇
  2017年   84篇
  2016年   97篇
  2015年   88篇
  2014年   111篇
  2013年   190篇
  2012年   101篇
  2011年   180篇
  2010年   121篇
  2009年   124篇
  2008年   203篇
  2007年   166篇
  2006年   149篇
  2005年   122篇
  2004年   106篇
  2003年   98篇
  2002年   132篇
  2001年   81篇
  2000年   76篇
  1999年   51篇
  1998年   40篇
  1997年   39篇
  1996年   45篇
  1995年   48篇
  1994年   47篇
  1992年   43篇
  1991年   37篇
  1990年   38篇
  1989年   33篇
  1981年   31篇
  1977年   29篇
  1976年   32篇
  1973年   29篇
  1968年   29篇
  1967年   34篇
  1966年   30篇
  1965年   47篇
  1964年   39篇
  1963年   39篇
  1962年   33篇
  1961年   45篇
  1960年   45篇
  1959年   43篇
  1958年   46篇
  1957年   42篇
  1956年   40篇
  1955年   38篇
  1954年   41篇
排序方式: 共有4221条查询结果,搜索用时 15 毫秒
61.
Summary. In the present experiment the behaviour and endocrine status of males of the brown trout, Salmo trutta L., (Salmoniformes: Salmonidae) were studied when males were kept in a stream tank with a nest digging female. Groups of mature adult males and precocious intact or anosmic male parr were placed with the nesting female so that the group resembled a natural spawning situation with big anadromous fish acting as dominant males and precocious parr acting as “sneakers”. A control experiment was also run with only males without a female present. In intact parr there were significant positive correlations between the per cent of the total observation time spent with a female, milt volume, and plasma concentration of 17α, 20β-dihydroxy-4-pregnen-3-one. Anosmic parr had significantly lower volumes of strippable milt and gonadal steroid hormone levels compared with intact parr. However, no differences were found in the control experiment. Significantly fewer anosmic parr attended and courted the nesting female and those anosmic fish that attended the female had significantly lower plasma levels of gonadal hormones. Intact parr also displayed a greater number of agonistic acts against other parr without any difference in fighting ability. No differences in aggression occured in the control experiment. In adult males together with a female, post-experimental gonadal steroid hormone levels were higher than pre-experimental levels. Positive correlations between aggression and androgen hormone levels were observed in adult males. No differences in plasma hormone levels were observed between adult males and intact precocious males. The results show that olfactory occlusion results in low steroid hormone levels and milt volumes in precocious males placed in a spawning situation. The courting behaviour was also affected by anosmia. Odours from the nesting female may have caused the enhanced plasma hormone levels and stimulated the males to attend the female. Received 15 May 1997; accepted 29 June 1997.  相似文献   
62.
63.
Abstract

In many studies, ergonomics has been shown to influence human performance. The aim of this paper was to demonstrate imp ortan t ergonomics influences on quality in industrial production, from the perspective of interactions between humans, technology, organization, and work environment. A second aim was to elab orate on the implications of these findings for the development of quality management strategies. This paper shows that ergonomics problems in terms of adverse work environmental conditions, in appropriate design of technology, and an unsuitable org an izatio n are important causes of quality deficiencies. Problem solving aimed at improving ergonomics, quality, and productivity simultaneously is likely to obtain sup po rt from most of the interest parties of the company, and may also enhance participation. Ergonomics has the potential of becoming a driving force for the development of new quality management strategies.  相似文献   
64.
This paper presents the use of new technical equipment by young adults (30 years old or younger), and the physical symptoms they have. The paper then analyses how the symptoms are associated with the use of computers and mobile phones, taking into account the background information. The study is based on a survey of 15000 working-age ( 18-65) Finns. The responses (1563) covering young adults’ physical symptoms were analysed. Altogether 53.3% of all young adults had pretty often or more frequently pain, numbness or aches in the neck and 32.2% had aches in the hip and lower back. Women experienced more pain, numbness or aches in the neck (65.0%) than men (34.5%). The use of different computers at leisure quite often had an association with some symptoms in different parts of the body. In addition, exhaustion at work had associations with some physical symptoms. In the future, it is essential to note ergonomic reasons and exhaustion at work when young adults experience pain, numbness or aches.  相似文献   
65.
Differences between the root uptake of fallout radionuclides by different cultivars ('inter-cultivar' variability) growing on the same field may be influenced not only by genetic differences of the cultivars, but also by the spatial variability of the soil-to-grain transfer within the cultivation area of each cultivar. This 'intra-cultivar' variability was investigated in 2001 and 2002 for 137Cs and 90Sr using three winter wheat cultivars with four replicates for each cultivar at three different sites in Bavaria, Germany. The intra-cultivar variability proved to be in the same range as the inter-cultivar variability which was determined earlier at the same sites for both radionuclides. An ANOVA of the 137Cs data set revealed that the variability of the 137Cs soil-to-grain transfer was caused by the soil and climate (year) at the field sites and the interaction of cultivar and field. A significant contribution of the factor 'cultivar' alone to the variability could not be detected. This may be due to the complex environmental conditions to which plants are exposed in field experiments. To find wheat cultivars with minimal uptake of fallout radionuclides it may be better to examine the molecular mechanisms of their root uptake in order to identify targets for breeding "safer" plants.  相似文献   
66.
The Kyoto Protocol’s Clean Development Mechanism (CDM) is often cited as an exemplar of new, hybrid forms of global environmental governance operating at the public–private interface. Practically, enacting this arrangement involves a wide range of non-state actors. This broad involvement is here assumed to mark a shift towards more polycentric and networked modes of governance in which agents collaborate as ‘stakeholders’ in the process of consensual rule-setting and implementation. Using post-political critique, the depoliticising effects of the stakeholder framework on civil society actors are interrogated, using formal and informal participation opportunities to raise concerns regarding specific CDM projects. The analysis suggests that the CDM’s collaborative narrative of stakeholding structurally fails to stimulate public (re)engagement and is, instead, a prime example of simulative governance that struggles to achieve the simultaneity of two incompatibilities: the participatory revolution and the post-political turn.  相似文献   
67.
Value stream mapping (VSM) is a well-accepted tool within lean manufacturing concept which is often used for analysing and designing the flow of materials and information required to manufacture a product. However, the analysis is static and single product oriented, which fails to cope with either the variation of production plan or a multi-product environment. In addition, the environmental impact of a manufacturing system is highly associated with the dynamic consumption of energy and resources. Despite the recent integration of VSM with simulation or environmental studies (in the domain of energy efficiency), still neglected is the dynamic assessment of all the resources involved in a multi-product production environment. This paper presents a methodology for modelling multi-product manufacturing systems with dynamic material, energy and information flows with the aim to generate economic and environmental value stream maps (E2VSM). The proposed methodology is validated with an industrial case.  相似文献   
68.
This paper reviews the effects of six post-modern management concepts as applied to Turkish forestry. Up to now, Turkish forestry has been constrained, both in terms of its operations and internal organization, by a highly bureaucratic system. The application of new thinking in forestry management, however, has recently resulted in new organizational and production concepts that promise to address problems specific to this Turkish industry and bring about positive changes. This paper will elucidate these specific issues and demonstrate how post-modern management thinking is influencing the administration and operational capacity of Turkish forestry within its current structure.  相似文献   
69.
This study investigated some of the important physical (thickness swelling) and mechanical (modulus of rupture, modulus of elasticity and internal bond) properties of single-layer particleboard panels made from eucalyptus (Eucalyptus camaldulensis Dehn.), waste of grass clippings (Lolium perenne L.) and combinations of the two. The chemical properties (pH, holocelluse and alpha cellulose contents, and water, alcohol-benzene and 1% sodium hydroxide solubilities) of the raw materials were also determined. Panels with a 6:94 ratio of grass-to-eucalyptus particles had the required mechanical properties for interior fitments including furniture and general uses. Boards manufactured with 100% grass clippings exhibited the lowest quality. The overall panel properties improved with a lower percentage of grass clippings added. Based on initial results, it also appears that grass should compose no more than 13% to achieve acceptable panel properties for interior fitments and general uses.  相似文献   
70.
In urine-diverting toilets, urine and faeces are collected separately so that nutrient content can be recycled unmixed. Faeces should be sanitized before use in agriculture fields due to the presence of possible enteric pathogens. Composting of human faeces with food waste was evaluated as a possible method for this treatment. Temperatures were monitored in three 78-L wooden compost reactors fed with faeces-to-food waste substrates (F:FW) in wet weight ratios of 1:0, 3:1 and 1:1, which were observed for approximately 20 days. To achieve temperatures higher than 15 degrees C above ambient, insulation was required for the reactors. Use of 25-mm thick styrofoam insulation around the entire exterior of the compost reactors and turning of the compost twice a week resulted in sanitizing temperatures (>or=50 degrees C) to be maintained for 8 days in the F:FW=1:1 compost and for 4 days in the F:FW=3:1 compost. In these composts, a reduction of >3 log(10) for E. coli and >4 log(10) for Enterococcus spp. was achieved. The F:FW=1:0 compost, which did not maintain >or=50 degrees C for a sufficiently long period, was not sanitized, as the counts of E. coli and Enterococcus spp. increased between days 11 and 15. This research provides useful information on the design and operation of family-size compost units for the treatment of source-separated faeces and starchy food residues, most likely available amongst the less affluent rural/urban society in Uganda.  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