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   42344篇
  免费   561篇
  国内免费   606篇
安全科学   1493篇
废物处理   1952篇
环保管理   5903篇
综合类   6731篇
基础理论   11053篇
环境理论   15篇
污染及防治   10624篇
评价与监测   2774篇
社会与环境   2672篇
灾害及防治   294篇
  2022年   403篇
  2021年   442篇
  2020年   340篇
  2019年   351篇
  2018年   638篇
  2017年   659篇
  2016年   1016篇
  2015年   772篇
  2014年   1157篇
  2013年   3489篇
  2012年   1460篇
  2011年   1986篇
  2010年   1593篇
  2009年   1688篇
  2008年   1982篇
  2007年   1944篇
  2006年   1731篇
  2005年   1500篇
  2004年   1463篇
  2003年   1372篇
  2002年   1284篇
  2001年   1524篇
  2000年   1137篇
  1999年   721篇
  1998年   516篇
  1997年   545篇
  1996年   552篇
  1995年   661篇
  1994年   554篇
  1993年   495篇
  1992年   502篇
  1991年   489篇
  1990年   466篇
  1989年   456篇
  1988年   402篇
  1987年   343篇
  1986年   363篇
  1985年   352篇
  1984年   413篇
  1983年   359篇
  1982年   402篇
  1981年   345篇
  1980年   273篇
  1979年   307篇
  1978年   237篇
  1977年   210篇
  1975年   211篇
  1974年   208篇
  1973年   234篇
  1972年   214篇
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
941.
The pesticide formulation industry is dependent upon the basic manufacturers for the main raw materials. Waste minimization efforts are, therefore, limited to process/handling sources. The economic incentive for waste reduction has mandated significant changes throughout each facility. There are waste problems, however, that require industry-wide action, e.g., empty containers. The ongoing regulatory actions affecting this business will require continuing efforts to maintain operations.  相似文献   
942.
943.
The importance of the incorporation of personal communication devices in emergency evacuation simulators will be discussed. Four case studies are examined to identify usage statistics and human behavior when using the devices in an emergency. The case studies are: 9/11 World Trade Center Attacks, London train bombings, Virginia Tech shooting and United Flight #93. The case studies’ findings are implemented into the Vacate evacuation simulator, which uses particle swarm optimization to mimic human pedestrian behavior. The physical actions of using a device, as well as the reaction to the information transmitted during usage, are examined. Findings show that the effects of the personal communication devices can affect individuals that are close to the user of the device, as well as those not in the local vicinity of the user. These effects, combined with the rapid mainstream acceptance of communication technologies, justify the implementation of personal communication devices into evacuation simulators.  相似文献   
944.
This paper presents the design and the implementation of a methodology for measuring and improving safety culture at a nuclear power plant (NPP). The study has involved the completion of a pilot project aimed at seeing how to make use of the RADAR logic (Results, Approach, Deployment, Assessment and Review) of the EFQM model as a tool for the self assessment of safety culture in a nuclear power plant. The work was aimed at finding evidence of the safety culture that was in place at the plant and at identifying both the strengths of that culture and any areas in which it could be improved. The score obtained from an analysis of those strengths and areas for improvement has made it possible to prioritise the actions to be taken. The identification of perceptions and evidence, the agreement on the strong points and areas for improvement and the quantification of the safety culture have been performed by groups comprising volunteers who work at the NPP. The advantages of this methodology are assessed in the paper.  相似文献   
945.
某城市污水处理厂二沉池出水拟采用强化混凝技术进行深度处理后用作邻近发电厂的冷却用水。为了指导生产运行,采用正交试验对强化混凝技术的主要影响因素进行了研究。结果表明:影响因素的主次顺序为助凝剂投加量>搅拌转速>接触污泥浓度>絮凝阶段的pH。强化混凝技术处理该二沉池出水的最佳运行工况:PAM浓度为0.3 mg/L,接触污泥浓度为2.5 g/L,搅拌转速为80 r/min,pH为6.0。在最佳运行工况下,浊度由10.0 NTU降至0.5 NTU以下,TP浓度由1.5 mg/L左右降至1.0 mg/L以下,最低可达0.2 mg/L,优于GB/T 19923—2005《城市污水再生利用 工业用水水质》的相关要求。  相似文献   
946.
947.
948.
The general integument of reptiles is traditionally defined as being dry, but we report here the discovery of unicellular mucoid glands (UCMG) in the dorsal skin of lizards of the genus Phelsuma (Gekkonidae). To this end, the skin of these lizards and of some others for comparison was studied by scanning electron microscopy and transmission electron microscopy. These photographs showed that the development and function of the UCMGs are related to the skin's sloughing cycle. The UCMGs differentiate at scattered locations from Oberh?utchen cells of the inner (new) epidermal generation, above the differentiating beta-keratin layer. While the inner generation matures, the UCMG increases in size; unlike the surrounding Oberh?utchen cells, it does not develop the spinules that characterize gecko skin. When, upon sloughing, the inner generation becomes the new outer generation, and the Oberh?utchen forms the skin surface, the UCMGs, several per scale, dot the surface as mucus-inflated "blebs" projecting from the surrounding spinulate Oberh?utchen, each nesting in a shallow pit of the underlying beta-keratin. On the surface, the UCMGs rupture and the mucus appears to dissipate in cords, flowing over the tips of the spinules, and incorporating minute foreign bodies. It is concluded that, due to the low wettability of the spinulate surface (derived from the spacing of the spinules), the cords brush off easily, with the mucus functioning as a cleaning agent.  相似文献   
949.
950.
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