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   1822篇
  免费   149篇
  国内免费   138篇
安全科学   463篇
废物处理   38篇
环保管理   347篇
综合类   697篇
基础理论   166篇
环境理论   3篇
污染及防治   121篇
评价与监测   70篇
社会与环境   88篇
灾害及防治   116篇
  2024年   5篇
  2023年   19篇
  2022年   16篇
  2021年   31篇
  2020年   44篇
  2019年   50篇
  2018年   40篇
  2017年   71篇
  2016年   81篇
  2015年   73篇
  2014年   94篇
  2013年   143篇
  2012年   113篇
  2011年   119篇
  2010年   103篇
  2009年   92篇
  2008年   76篇
  2007年   121篇
  2006年   125篇
  2005年   105篇
  2004年   83篇
  2003年   97篇
  2002年   66篇
  2001年   59篇
  2000年   59篇
  1999年   46篇
  1998年   28篇
  1997年   18篇
  1996年   13篇
  1995年   14篇
  1994年   11篇
  1993年   10篇
  1992年   6篇
  1991年   6篇
  1990年   8篇
  1989年   5篇
  1988年   8篇
  1987年   3篇
  1986年   3篇
  1985年   3篇
  1984年   7篇
  1983年   3篇
  1982年   5篇
  1980年   4篇
  1978年   5篇
  1977年   2篇
  1976年   3篇
  1974年   2篇
  1972年   3篇
  1971年   4篇
排序方式: 共有2109条查询结果,搜索用时 375 毫秒
971.
This study explores the meaning and functional design of a modulatory communication signal, the honey bee shaking signal, by addressing five questions: (I) who shakes, (II) when do they shake, (III) where do they shake, (IV) how do receivers respond to shaking, and (V) what conditions trigger shaking. Several results confirm the work of Schneider (1987) and Schneider et al. (1986a): (I) most shakers were foragers (at least 83%); (II) shaking exhibited a consistent temporal pattern with bees producing the most signals in the morning (0810–1150 hours) just prior to a peak in waggle dancing activity; and (IV) bees moved faster (by 75%) after receiving a shaking signal. However, this study differs from previous work by providing a long-term, temporal, spatial, and vector analysis of individual shaker behavior. (III) Bees producing shaking signals walked and delivered signals in all areas of the hive, but produced the most shaking signals directly above the waggle dance floor. (IV) Bees responded to the signal by changing their direction of movement. Prior to receiving a signal, bees selected from the waggle dance floor moved, on average, towards the hive exit. After receiving a signal, some bees continued moving towards the exit but others moved directly away from the exit. During equivalent observation periods, non-shaken bees exhibited a strong tendency to move towards the hive exit. (V) Renewed foraging activity after food dearth triggered shaking signals, and, the level of shaking is positively correlated with the duration of food dearth. However, shaking signal levels also increased in the morning before foraging had begun and in the late afternoon after foraging had ceased. This spontaneous afternoon peak has not previously been reported. The shaking signal consequently appears to convey the general message “reallocate labor to different activities” with receiver context specifying a more precise meaning. In the context of foraging, the shaking signal appears to activate (and perhaps deactivate) colony foraging preparations. The generally weak response elicited by modulatory signals such as the shaking signal may result from a high receiver response threshold which allows the receiver to integrate multiple sources of information and which thereby increases the probability that receiver actions will be appropriate to colony needs. Received: 21 March 1997 / Accepted after revision: 30 August 1997  相似文献   
972.
产品生态设计是一种新的设计理念,其以产品环境特性为目标,以生命周期评价为工具,综合考虑产品整个生命期相关的生态环境问题,设计出对环境友好的,又能满足人的需求的新产品。设计方法和步骤包括四个阶段:产品生态辨识,产品生态诊断,产品生态定义,生态产品评价。  相似文献   
973.
简要分析公安机关消防机构在进行建筑工程消防设计审核与验收工作中,建设、设计、施工单位及消防技术服务机构、消防产品生产单位、公安机关消防机构和其他行政主管部门7个责任相关方之间存在的问题;将修订后的《消防法》与现行《消防法》进行对比;总结出修订后的《消防法》在消防设计审核与验收工作方面的新规定、新举措,并从法律角度和现实意义两个方面进行分析和探讨,为新《消防法》施行后相关部门和单位消防设计审核与验收工作的开展提供一定的帮助。  相似文献   
974.
This paper presents detailed modeling results of the BP Texas City refinery incident. Three different approaches and explosion modeling tools were used to study the event. The results predicted by all three approaches are similar and all approaches identified a hazard potential comparable to what was witnessed on March 23, 2005. This confirms that quantitative risk assessment (QRA) has the ability to model a realistic scenario, and is therefore useful in safety measure design and emergency preparedness decision making to improve overall safety performance. Had QRA been conducted during a management of change (MOC) decision-making process, personnel trailers likely would not have been sited in such close proximity to the process units. The resulting severe consequences would then not have occurred. This work also aims to emphasize the importance of QRA in process safety management.

The paper presents the authors’ perception of the sequence of events involved in the incident based on the published literature available at the time of writing. It also assesses potential consequences for the perceived sequence of events using a variety of consequence assessment tools. In doing so, the analysis illustrates how this incident could have been prevented in spite of many operational difficulties. The observations and commentary presented in this paper are intended solely for the purpose of process safety enhancement on the basis of the lessons learned. BP has published its own detailed report; the incident is also the subject of a recent investigation by the US Chemical Safety and Hazard Investigation Board, with the CSB's final report being available at http://www.csb.gov/index.cfm?folder=completed_investigations&page=info&INV_ID=52 (as of April 2007).  相似文献   

975.
976.
此文叙述了转向螺母锻模块液态模锻工艺及特点,对该工艺及模具设计作了较详细的分析研究。  相似文献   
977.
While it is widely known that sustainable development is the only sound and viable pathway for humankind’s future, its attainment remains elusive despite intensive efforts and some successes. The current industrial society approach based on product and process innovation in a variety of fields is not providing the expected results in addressing this important issue. In an attempt to carry out this unavoidable task, Osaka University’s Research Institute for Sustainability Science (RISS) introduces an integral and dynamic innovation system where technology plays a key role in fulfilling societal functions. This innovation system adopts a highly solution-driven approach that makes use of backcasting techniques based on long-term visions and mid-term strategic goals. Since technology management is the key to propelling effective innovation towards sustainability, we propose a technology transition management through the interaction of technology push, demand pull and institutional design, along with eight transition principles. RISS will develop this innovation system based on these three components and through the design of dynamic scenarios and their roadmaps.  相似文献   
978.
城市表层土壤重金属与磁化率的多尺度空间变异分析   总被引:4,自引:1,他引:3  
采集徐州市城区167个表层土壤的样品,并分别测定了磁化率χ的数值及其5种重金属(Cu、Zn、Mo、Cd和Pb)的含量.利用多元因子克里金分析上述研究变量在局部尺度(1 km变程)和区域尺度(5.5 km变程)的空间变异特征.研究表明,徐州城市表土中的磁化率与重金属在局部尺度上主要受到交通、工业和农业等人为因素的影响,在区域尺度上,则以土壤母岩等自然因素为主导.磁化率#与Cu、Zn、Mo、Cd、Pb在局部尺度上的结构相关性较高,在此尺度内选择适当的采样间隔,有助于提高磁化率作为上述重金属污染替代指标进行空间制图的精度.  相似文献   
979.
基于山西省王庄煤矿采煤塌陷和废弃物压占土地等主要环境问题和矿区生态条件,提出了生态恢复模式设计主要包括平面结构、垂直结构、食物链网、时间节律和工程措施等五项内容,并在此基础上优化集成了立体共生、设施农业、物质循环、农林鱼禽系统、旅游景观开发、科普园区设计等六种生态恢复模式;最后在典型塌陷区进行了经济、社会和生态效益的示范性评价,结果良好。这一切均为建设生态矿区、和谐矿区提供了理论依据。  相似文献   
980.
采用实验室测试和现场调查相结合的方法,测试了高性能聚乙烯纤维手套的防护性能,调查手套的适应性、防护时间和费用支出,探讨了其应用前景。  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