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   98篇
  免费   2篇
  国内免费   11篇
安全科学   2篇
废物处理   1篇
环保管理   15篇
综合类   30篇
基础理论   39篇
污染及防治   15篇
评价与监测   4篇
社会与环境   5篇
  2020年   1篇
  2019年   1篇
  2018年   1篇
  2017年   4篇
  2016年   4篇
  2015年   4篇
  2014年   2篇
  2013年   14篇
  2012年   6篇
  2011年   7篇
  2010年   6篇
  2009年   3篇
  2008年   2篇
  2007年   6篇
  2006年   2篇
  2005年   2篇
  2004年   7篇
  2003年   5篇
  2002年   4篇
  2001年   2篇
  2000年   4篇
  1999年   4篇
  1998年   2篇
  1997年   7篇
  1996年   5篇
  1995年   1篇
  1993年   3篇
  1992年   1篇
  1991年   1篇
排序方式: 共有111条查询结果,搜索用时 265 毫秒
21.
Arthropod communities in pear are conceptualized as hierarchically organized systems in which several levels of organization or subsystems can be recognized between the population level and the community as a whole. An individual pear tree is taken to be the community habitat with arthropod subcommunities developing on leaf, fruit, and wood subcommunity habitats. Each subcommunity is composed of trophically organized systems of populations. Each system of populations is comprised of a functional group or guild of phytophagous arthropods that use the habitat primarily for feeding but also for overwintering or egg deposition, and associated groups of specialized predators, parasitoids, and hyperparasitoids. Several species move from one subcommunity to another during the course of community development and thus integrate community subsystems. Community development or change in organization through time is conceptualized as being jointly determined by the development of the habitat and the organization of the species pool. The influence of habitat development on community development within a species pool is emphasized in this research. Seasonal habitat development is expressed as change in the kinds and biomasses of developmental states of wood, leaf, and fruit subcommunity habitats. These changes are accompanied by changes in the kinds, biomasses, and distributions of associated community subsystems.  相似文献   
22.
果树光合作用研究进展   总被引:7,自引:0,他引:7  
综述了果树光合作用的研究方法,观测仪器,日变化和季节变化,以及内在因素(种类、品种、年龄、叶位、叶绿素含量、酶系统)和外部因素(光照、CO2、温度、湿度、土壤、外用药剂)对果树光合作用的影响。  相似文献   
23.
作者从WTO对果业的影响及现代果业科技创新的表现,揭示了衡阳果业技术创新的优势与存在的问题,并从健全科技创新制度,提高果业生产科技含量和农业信息化等方面提出了促进科技创新,提高衡阳果业竞争力的途径。  相似文献   
24.
模拟酸雨对龙眼幼果纤维素酶活性和内源激素含量的影响   总被引:5,自引:0,他引:5  
酸雨胁迫后,龙眼幼果IAA、GA1 3、ZRs、DHZRs、iPAs含量下降,ABA含量升高,生长抑制物ABA和生长促进物(IAA、GA1 3)的比值提高,酸雨胁迫还使纤维素酶活性上升,促进幼果脱落.易脱落幼果的纤维素酶活性和ABA含量高于正常幼果,而IAA、GA1 3、iPAs、ZRs、DHZRs含量低于正常幼果.图6表1参14  相似文献   
25.
观赏果树在乌鲁木齐市绿化环境的效果及应用分析   总被引:1,自引:0,他引:1  
为比较不同观赏果树在乌鲁木齐市对绿化环境的效果,分析不同观赏果树在乌鲁木齐市的应用方式.本实验以乌鲁木齐市20年生的常见观赏果树山桃、新疆梨等为实验材料,分析其可观赏性、生长期、生长状况、抗性、产量、滞尘量、绿化环境的不利因素,结果显示8种观赏果树绿化环境的效果从优往劣依次是黑桑、红果山楂、黄太平、毛杏、山桃、李子、新疆梨、葡萄.对乌鲁木齐市绿化环境的建设,这8种观赏果树与其他观赏植物配合进行花园立体绿化环境,效果更好.  相似文献   
26.
Sewage sludge addition to agricultural lands requires judicious management to avoid environmental risks arising from heavy metal and nitrate contamination of surface water and accumulation in edible plants. A field study was conducted on a silty-loam soil of 10% slope at Kentucky State University Research Farm. Eighteen plots of 22 × 3.7 m each were separated using metal borders and the soil in six plots was mixed with sewage sludge and yard waste compost mix (SS-YW) at 15 t acre?1, six plots were mixed with sewage sludge (SS) at 15 t acre?1, and six unamended plots that never received sludge were used for comparison purposes. Plots were planted with eggplant, Solanum melongena L. as the test plant. The objectives of this investigation were to: 1) assess the effect of soil amendments on the transport of NO3, NH4, and heavy metals (Cd, Cr, Ni, Pb, Zn, Cu, and Mo) into surface water; 2) investigate the effect of soil amendments on heavy metal bioavailability in eggplant fruits at harvest; and 3) assess chemical and physical properties of soil following addition of soil amendments and their impact on the yield and quality of eggplant fruit. SS-YW treatments reduced runoff water by 63% while plots incorporated with sewage sludge alone reduced runoff water by 37% compared to control treatment. The SS-YW treatments transported more mineral nitrogen (NO3-N and NH4-N) in runoff water than SS treatments. Total marketable yield (lbs acre?1) and number of eggplant fruits were greatest in SS-YW treatments. This response may be due to improved soil porosity, water, and nutrient retention of the soil amended with SS-YW mixture. Concentrations of heavy metals in soil amended with sludge were below the U.S. Environmental Protection Agency (USEPA) limits. Chromium, Ni, Zn, and Cu were taken up by eggplant fruits but their concentrations were below the Codex Commission allowable levels.  相似文献   
27.
This research conducted on municipal solid waste management for the first time quantified food spoilage as being 8.8% weight of all officially collected household garbage in the Brazilian city under study. The unexpected size of this waste fraction gave rise to work on the causes of waste and on its distribution over the product life cycle specific to fruit and vegetables. Waste was defined as being the combination of losses and scraps. Administrative shortcomings were identified as basic reasons for waste. At the producer and consumer ends of the cycle, negligence was shown to be the single most important problem. Fruit and vegetables deteriorate during the operations of handling, transport, packaging, storage, selling and consumption. The study detailed the occurrence of waste at all of these stages. In the medium-size Brazilian city, the total waste of fruit and vegetables was shown to amount to 16.6% weight in the marketing stage of the life cycle. At the consumer level, it was measured as 3.4% weight of all household garbage. Specific reasons for this waste were identified at the levels of producer, wholesaler and retailer. Short-term remedies were pointed out that invariably corrected deficient management procedures. It was shown that very simple administrative measures can significantly reduce the spoilage of fruit and vegetables. Long-term strategies involve the creation of sample cases for administration of the fruit and vegetables life cycle at all stages.  相似文献   
28.
赣中南柑橘果实生长发育规律与栽培技术关系   总被引:1,自引:0,他引:1  
通过果实体积的累积生长量,日均生长速度和相对生长速率三个指标的测定。可得到各类果实生长的“S”形曲线。生长呈三个时期,第一期为细胞分裂期,这个时期,生长速度较慢,而相对生长速率最高,是是实生长能力最高阶段;第二期为细胞膨大期,生长速度最快时期,而相对生长速率则呈下降趋势;第三期为成熟期,日均生长速度和相对生长速率都是低速和稳定时期。主要内部生理变化,柑橘各类果 个指标各异,此外,果实生长过程中,有  相似文献   
29.
西藏尼洋河流域果树资源及其开发途径探讨   总被引:3,自引:0,他引:3  
西藏尼洋河流域果树资源丰富,栽培果树有苹果、梨、桃、李、杏和葡萄等9种和90多个品种;野生果树有7科16属41种,目前利用程度低,开发潜力大。文中提出了该地区果树资源的开发途径,在尼洋河下游和雅鲁藏布江的扎绕乡至派乡之间段的河谷地上形成“Y”字型的水(干)果种植带,建设成为西藏的水(干)果生产基地,并对现有果园改造更新,充分利用野生水果资源,建立果品综合加工厂等以满足西藏市场对水果和果品的需要。  相似文献   
30.
As in many sectors in emerging economies, the concept of corporate social responsibility (CSR) has become important for exporting agri‐food firms in view of their integration in global supply chains. The purpose of this research was to assess the implementation by Chilean fruit exporters of CSR practices that go beyond minimum legal requirements. The principal results are that, although socio‐economic components of CSR such as poverty reduction and socially just working conditions receive much attention, firms consider comprehensive environmental practices as less important. The results also indicate a slightly higher implementation of comprehensive CSR practices by large firms as compared to small and medium sized enterprises (SMEs). The main conclusion is that, although CSR is increasingly considered by Chilean firms, among SMEs in particular, more attention needs to be paid to raising awareness among managers about CSR practices and to providing assistance in their implementation. This supports findings on CSR implementation in other emerging economies that an active role of civil society and industry organizations is key and that targeted support strategies are needed to install a holistic awareness of CSR and help firms to improve on those aspects of CSR that are relatively underdeveloped.  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