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   603篇
  免费   71篇
  国内免费   191篇
安全科学   78篇
废物处理   35篇
环保管理   73篇
综合类   386篇
基础理论   115篇
污染及防治   105篇
评价与监测   34篇
社会与环境   28篇
灾害及防治   11篇
  2024年   2篇
  2023年   12篇
  2022年   11篇
  2021年   14篇
  2020年   18篇
  2019年   27篇
  2018年   19篇
  2017年   18篇
  2016年   34篇
  2015年   42篇
  2014年   41篇
  2013年   52篇
  2012年   60篇
  2011年   60篇
  2010年   51篇
  2009年   55篇
  2008年   33篇
  2007年   30篇
  2006年   52篇
  2005年   14篇
  2004年   20篇
  2003年   29篇
  2002年   22篇
  2001年   35篇
  2000年   24篇
  1999年   11篇
  1998年   11篇
  1997年   11篇
  1996年   5篇
  1995年   16篇
  1994年   6篇
  1993年   5篇
  1992年   6篇
  1991年   2篇
  1990年   5篇
  1989年   1篇
  1988年   2篇
  1987年   1篇
  1986年   1篇
  1985年   3篇
  1980年   1篇
  1977年   1篇
  1972年   1篇
  1971年   1篇
排序方式: 共有865条查询结果,搜索用时 562 毫秒
391.
Environmental scientists have long been frustrated by the difficulties involved in transferring their research findings into policy-making, management, and public spheres. Despite increases in scientific knowledge about social-ecological systems, research has consistently shown that regulators and stakeholders draw on tacit, informal, and experiential knowledge far more than scientific knowledge in their decision-making. Social science research in the fields of knowledge exchange (KE) and knowledge mobilization (KMb) suggest that one of the major barriers to moving knowledge into practice is that scientists fail to align their communication strategies with the information-seeking behaviours and preferences of potential knowledge users. This article presents findings from in-depth qualitative research with government employees and stakeholders involved in co-managing Pacific salmon fisheries in Canada’s Fraser River. We investigate how members of these groups access, view, and use scientific information, finding both similarities and differences. Members of both groups express a strong interest in academic science, and self-report using scientific information regularly in their work and advocacy. However, the two groups engage in different information-seeking behaviours, and provide notably different advice to academic scientists about how to make research and communication more relevant to potential users. For example, government employees focus on the immediate applications of research to known problems, while stakeholders express greater concern for the political context and implications of scientific findings. We argue that scientists need to “go where the users are” in the behavioural and intellectual sense, and tailor their communications and engagement activities to match the habits, preferences, and expectations of multiple potential user groups. We conclude with recommendations on how this may be done.  相似文献   
392.
Moving up the waste hierarchy is a key priority for UK waste policy. Waste prevention requires policy interventions to promote reuse. The term ‘reuse exchange’ has been adopted by UK policy makers to describe a variety of second-hand trading outlets including car boot sales, charity shops and online exchange sites. As waste policy is based on tonnage diverted from disposal (or landfill), policy interventions to promote reuse exchange will be based on the weight of goods estimated to be flowing through these sites. This paper uses a combination of field survey data and scale-up estimation to quantify and characterise the weight of goods exchanged at car boot sales in England in 2012. This is estimated at 50–60 000 tonnes per annum. The paper emphasises that movement up the waste hierarchy brings waste policy into closer contact with household consumption practices. It draws on qualitative research to show that, for participants, car boot sales are not associated with waste prevention. Instead, car boot sales rely on stocks of surplus household goods and exemplify the culture of thrift, which enables more, not less, consumption. The paper shows the collision between the social values that inform thrift and the environmental values that underpin reuse; and it argues that the policy goal of enhanced recovery for reuse might best be achieved by working with consumer culture. Two ways of achieving this are suggested: interventions that make it easier for consumers to do the right thing, through promoting opportunities for the circulation of stocks of surplus goods, for example, through increasing the frequency of car boot sales; and interventions which recognise that car boot sales also generate waste, which could be recovered for reuse.  相似文献   
393.
In this study, three rice varieties, Byou268 (low light-sensitive type), Nei5you768 (intermediate type), and Yixiangyou1108 (low light-tolerant), were used as experimental materials to investigate the yield and quality responses of different rice varieties to low light stress under normal light (CK) and low light (SH). The results showed the following: (1) Compared with normal light, the decrease in Yixiangyou1108’s 1 000-grain weight, grain number per spike, and seed setting rate under low light treatment were much lower than those of Nei5you768 and Byou268. The yield decline of Yixiangyou1108 (46.5%) was significantly lower than that of Nei5you768 (56.5%) and Byou268 (69.8%). Yixiangyou1108 showed strong tolerance to low light stress in terms of 1 000-grain weight, seed setting rate, grain number per panicle, and yield. (2) Compared with normal light, the reduction in grain length and width of Yixiangyou1108 under low-light treatment was significantly greater than that of Byou268; however, the reduction in the length-width ratio did not reach a significant level. The amylose content and gel consistency of the rice were significantly reduced. The reduction in amylose content of Yixiangyou1108 (24.5%) was significantly lower than that of Nei5you768 (28.1%) and Byou268 (30.6%); however, the decrease in gel consistency of Yixiangyou1108 (14.7%) was significantly higher than that of Nei5you768 (9.8%) and Byou268 (8.1%). After low light treatment, the characteristic values of the RVA curve of rice changed. The peak viscosity and breakdown viscosity of Yixiangyou1108, Nei5you768, and Byou268 were significantly decreased, but the cold glue viscosity and setback viscosity were significantly increased, while there was no significant difference in the peak time and peak temperature. The response of 1 000-grain weight, grain number per spike, and seed setting rate under low light stress can be used as a yield index of rice breeding with low light tolerance; rice grain type, amylose, and gel consistency; and peak viscosity and hot paset viscosity in RVA characteristic values can be used as quality indexes of low-light-tolerant rice material breeding. © 2022 Science Press. All rights reserved.  相似文献   
394.
PROBLEM: Supervisors are increasingly important to the functioning of manufacturing operations, in large part due to their role as leaders. While supervisors' relations and communication with their subordinates are known to be important in influencing subordinates' behavior, little is known about how these two factors will impact subordinates' safety. This study investigated how much each factor contributes to safety-related outcomes for blue-collar production employees. METHOD: Production employees at five Pennsylvania wood manufacturers completed a survey during their work shift. Five hundred and ninety eight employees provided data on leader-member exchange (LMX), safety communication, and safety-related events. Archival data on OSHA recordables were also obtained from the producers' human resources database. RESULTS: Analyses found that the influence of LMX was greater than that of safety communication in predicting safety-related events. Neither LMX nor safety communication was significantly related to OSHA recordables. Results also demonstrated that employee job satisfaction and demographic variables such as gender and age have safety implications. IMPACT ON INDUSTRY: Results from this study further emphasize the importance of production supervisors and illustrate the potential role of leader-member exchange in enhancing workplace safety. Specifically, organizations should foster positive social exchange between their employees and supervisors and enhance the leadership qualities of supervisors to help reduce workplace injuries.  相似文献   
395.
In many semi-arid environments of Mediterranean ecosystems, white poplar (Populus alba L.) is the dominant riparian tree and has been used to recover degraded areas, together with other native species, such as ash (Fraxinus angustifolia Vahl.) and hawthorn (Crataegus monogyna Jacq.). We addressed three main objectives: (1) to gain an improved understanding of some specific relationships between environmental parameters and leaf-level physiological factors in these riparian forest species, (2) to compare the leaf-level physiology of these riparian species to each other, and (3) to compare leaf-level responses within native riparian plots to adjacent restoration plots, in order to evaluate the competence of the plants used for the recovery of those degraded areas. We found significant differences in physiological performance between mature and young white poplars in the natural stand and among planted species. The net assimilation and transpiration rates, diameter, and height of white poplar plants were superior to those of ash and hawthorn. Ash and hawthorn showed higher water use efficiency than white poplar. White poplar also showed higher levels of stomatal conductance, behaving as a fast-growing, water-consuming species with a more active gas exchange and ecophysiological competence than the other species used for restoration purposes. In the restoration zones, the planted white poplars had higher rates of net assimilation and water use efficiency than the mature trees in the natural stand. We propose the use of white poplar for the rapid restoration of riparian vegetation in semi-arid Mediterranean environments. Ash and hawthorn can also play a role as accompanying species for the purpose of biodiversity.  相似文献   
396.
Carbon dioxide exchange was studied in the photosynthetic apparatus of Siberian spruce (Picea obovata Ledeb.), Siberian larch (Larix sibirica Ledeb.), and weeping birch (Betula pendula Roth.) in a mature spruce forest. Parameters of CO2 balance in different weather were characterized quantitatively on the basis of daily measurements of CO2 exchange in needles and leaves of woody plants. The percent ratios of the components of carbon balance in needles and leaves of woody plants depending on daily photosynthetic fixation of carbon were determined. In summer, trees consumed 210 kg CO2/ha (57 kg C/ha) in variable weather and 117 kg CO2/ha (32 kg C/ha) in cloudy weather. Species specificity of CO2 consumption was revealed, and the effects of environmental factors on the assimilatory activity of trees were determined.  相似文献   
397.
A three-site cation exchange model is proposed to describe the concentration dependent uptake of Cs on natural argillaceous rock systems. Major premises in the model are that the sorption of Cs is dominated by the illite mineral component in the rock and that there is a fixed relationship between the site capacities of the three site types denoted as frayed edge, type II and planar sites. The definition of a “reference illite” with a cation exchange capacity of 0.2 equiv. kg-1 allows the three site capacities to be fixed in the model calculations over the weight fraction of illite in the argillaceous rocks. Up to Cs equilibrium concentrations of 10-3 M sorption occurs predominantly on the frayed edge and type II sites (higher affinity sites), with the planar site type playing only a minor role. Competition with Cs for sorption on the former two site types arises predominantly from monovalent cations such as K, Rb and NH4 which have low hydration energies. H and Na (except at high concentrations) are considerably less competitive and bivalent cations such as Mg, Ca and Sr are effectively non-competitive. A consistent set of selectivity coefficients for Cs with respect to K, Rb, NH4 and Na was derived from analyses and modelling of a wide range of Cs sorption data available in the open literature on pure illites from many different sources. The model was tested against four Cs sorption isotherm data sets determined on argillaceous rocks: Boom clay, Oxford clay, Palfris marl and Opalinus clay. The water chemistries and illite contents given in these experiments allowed the Cs sorption isotherms to be predicted. It is concluded that the Cs sorption model presented here, in which there are no free parameters, can be used to predict the uptake of Cs at equilibrium concentrations below 10-3 M to within a factor of 2 to 3 in natural argillaceous rock systems.  相似文献   
398.
An integrated approach using hydrodynamic and transport numerical models, lepidochronology and stable isotope analysis was used to investigate how local hydrodynamic conditions influence the primary production and fate of the seagrass Posidonia oceanica in a Mediterranean semi-enclosed marine system (Stagnone di Marsala). The water mass exchange aptitude of different sectors of the basin was analysed, and data collected were used to select two sectors (colonized by Posidonia oceanica showing the lowest and highest water exchange values) for biological analyses. According to the mean dispersal coefficient differences simulated by the hydrodynamic model, growth rate and primary production of P. oceanica differed between sectors, with average values lower in the central sector where water exchange is lower than in the southern sector. Although P. oceanica coverage and primary production were higher in the southern sector, carbon and nitrogen stable isotope analysis suggests that the transfer of seagrass organic matter to higher trophic levels of the food web was higher in the central sector. The possibility of a link between hydrodynamism, production and fate of organic matter is proposed to explain the observed patterns.  相似文献   
399.
利用弱光(紫外和可见)激发Ti O2光降解污染物是拓展多相光催化实际应用的关键之一.以吸附相反应技术为基础,利用N掺杂以及共掺杂两种方式制备多组分Ti O2光催化剂,并研究其在弱光下光降解甲基橙的过程.结合紫外可见漫反射光谱、X射线衍射、X射线电子能谱以及光致发光光谱等表征手段,探索焙烧温度、N掺杂量以及共掺杂对催化剂光吸收和可见光响应拓展的影响,进而研究弱光下催化剂活性的变化规律.结果发现,N掺杂可以显著增强催化剂的光吸收,从而显著提升其在弱紫外光下光降解甲基橙催化活性,所有N掺杂催化剂的活性均优于商用P25光催化剂.N掺杂对催化剂的可见光响应拓展作用不大,因而单一N掺杂后大部分催化剂在弱可见光下没有活性,仅5%N掺杂催化剂在900℃热处理后有微弱活性.N和Fe2O3二元耦合形成的共掺杂催化剂中,两者之间的协同作用既增强了复合光催化剂的光吸收,也显著拓展了催化剂的可见光响应,因而得到了在弱可见光下具有良好活性的复合光催化剂.  相似文献   
400.
湖泊水-沉积物界面DIC和DOC交换通量及耦合关系   总被引:1,自引:1,他引:0  
王伟颖  吕昌伟  何江  左乐  颜道浩 《环境科学》2015,36(10):3674-3682
以乌梁素海和岱海为研究对象,采用柱状芯样模拟法,开展了2个湖泊水-沉积物界DIC和DOC交换通量及耦合关系研究.结果表明,在夏季90 d的时间内,乌梁素海明水区沉积物表现为上覆水中DIC和DOC的碳源,DIC和DOC的平均释放速率分别为71.07 mmol·(m2·d)-1和185.09 mmol·(m2·d)-1;岱海浅、深水区沉积物整体上表现为上覆水中DIC和DOC的碳汇,浅水区DIC和DOC的平均释放速率分别为155.75 mmol·(m2·d)-1和-1 478.08 mmol·(m2·d)-1,深水区DIC和DOC的平均释放速率分别为-486.53 mmol·(m2·d)-1和-1 274.02 mmol·(m2·d)-1;岱海浅水区和乌梁素海水-沉积物界面DIC与DOC耦合作用(含量、释放速率、总量变化量的同步变化)主要受微生物摄取、微生物或非生物降解及水生植物的影响;岱海深水区水-沉积物界面DIC与DOC耦合作用则主要与Ca CO3共沉淀作用及沉积物中无机碳形态分布特征等有关.总体上,不同类型湖泊或同一湖泊不同湖区的DIC或DOC源/汇功能差异是湖泊类型、离岸距离、湖泊水文地球化学及无机碳形态分布等多种因素综合作用的结果.  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