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   223篇
  免费   2篇
  国内免费   1篇
安全科学   7篇
废物处理   2篇
环保管理   20篇
综合类   127篇
基础理论   25篇
污染及防治   27篇
评价与监测   9篇
社会与环境   6篇
灾害及防治   3篇
  2019年   3篇
  2017年   4篇
  2016年   5篇
  2014年   4篇
  2013年   7篇
  2012年   3篇
  2011年   8篇
  2010年   7篇
  2009年   11篇
  2007年   6篇
  2006年   6篇
  2005年   3篇
  2003年   6篇
  2001年   2篇
  2000年   2篇
  1995年   2篇
  1985年   2篇
  1981年   5篇
  1979年   3篇
  1967年   4篇
  1964年   3篇
  1963年   3篇
  1960年   2篇
  1959年   3篇
  1958年   2篇
  1957年   2篇
  1955年   5篇
  1951年   2篇
  1942年   2篇
  1940年   3篇
  1939年   3篇
  1937年   2篇
  1936年   2篇
  1935年   2篇
  1934年   8篇
  1932年   4篇
  1931年   3篇
  1929年   5篇
  1928年   5篇
  1927年   2篇
  1926年   2篇
  1925年   2篇
  1923年   2篇
  1922年   2篇
  1921年   4篇
  1918年   4篇
  1916年   2篇
  1915年   3篇
  1914年   2篇
  1913年   8篇
排序方式: 共有226条查询结果,搜索用时 15 毫秒
221.
On separate days, 6 highly trained participants performed psychomotor tests while breathing for 60 min 3 carbon dioxide (CO(2)) mixtures (room air, 3% CO(2), or 4% CO(2)) prior to, between, and following two 15-min treadmill exercise bouts (70% VO(2)(max)). Each individual was extensively practiced (at least 4 days) before testing began, and both gas conditions and order of tasks were counterbalanced. Results showed physiological reactions and work-related psychomotor effects, but no effects of gas concentration on addition, multiplication, grammatical reasoning, or dynamic postural balance. These findings help define behavioral toxicity levels and support a re-evaluation of existing standards for the maximum allowable concentrations (also emergency and continuous exposure guidance levels) of CO(2). This research explored the selection of psychometric instruments of sufficient sensitivity and reliability to detect subtle changes in performance caused by exposure to low levels of environmental stress, in this case differential levels of CO(2) in the inspired air.  相似文献   
222.
The study of the negotiation process has enjoyed a recent resurgence of scholarly interest. Of particular concern is the ability of negotiators to achieve solutions which result in integrative outcomes. The purpose of this study is to identify the effects of different levels of aspiration/goals on negotiator success and their ability to reach integrative solutions in a competitive market. One hundred fifty-eight subjects who were assigned one of four levels of goal difficulty-no goal, compromise goal, challenging goal, and difficult goal-participated in a competitive, multi-person, multi-transaction market simulation. The study found (1) challenging and difficult goals significantly enhanced participants' performance; (2) the more difficult the goal, the fewer transactions were completed; and (3) while there were no differences in total profitability among the challenging goal, compromise goal, and no goal, the difficult goal condition had a significant and negative effect on the ability of participants to achieve profitable outcomes within the market. A discussion of these findings and directions for future research are presented.  相似文献   
223.
Seven pumice samples from excavations in North Sinai have been investigated with respect to their geochemical composition. This type of volcanic rock has been used as an abrasive and thus has been an object of trade since antiquity. With the help of Instrumental Neutron Activation Analysis, six of these Bronze Age samples could be correlated to their volcanic sources on the islands of Santorini, Nisyros and Giali (Greece) using the typical element concentrations (“chemical fingerprint”). The source of one pumice sample remains unidentified excluding, however, the Santorini eruption as a possible source. The concluding section of this article discusses the possible contribution, however indirect, of the pumice from Sinai and elsewhere in the Eastern Mediterranean to the controversial issue of the accurate date of the “Minoan” eruption of Santorini.  相似文献   
224.
Post-Triassic theropod, sauropodomorph, and ornithischian dinosaurs are readily recognized based on the set of traits that typically characterize each of these groups. On the contrary, most of the early members of those lineages lack such specializations, but share a range of generalized traits also seen in more basal dinosauromorphs. Here, we report on a new Late Triassic dinosaur from the Santa Maria Formation of Rio Grande do Sul, southern Brazil. The specimen comprises the disarticulated partial skeleton of a single individual, including most of the skull bones. Based on four phylogenetic analyses, the new dinosaur fits consistently on the sauropodomorph stem, but lacks several typical features of sauropodomorphs, showing dinosaur plesiomorphies together with some neotheropod traits. This is not an exception among basal dinosaurs, the early radiation of which is characterized by a mosaic pattern of character acquisition, resulting in the uncertain phylogenetic placement of various early members of the group.  相似文献   
225.
Mapping opportunities and challenges for rewilding in Europe   总被引:1,自引:0,他引:1       下载免费PDF全文
Farmland abandonment takes place across the world due to socio‐economic and ecological drivers. In Europe agricultural and environmental policies aim to prevent abandonment and halt ecological succession. Ecological rewilding has been recently proposed as an alternative strategy. We developed a framework to assess opportunities for rewilding across different dimensions of wilderness in Europe. We mapped artificial light, human accessibility based on transport infrastructure, proportion of harvested primary productivity (i.e., ecosystem productivity appropriated by humans through agriculture or forestry), and deviation from potential natural vegetation in areas projected to be abandoned by 2040. At the continental level, the levels of artificial light were low and the deviation from potential natural vegetation was high in areas of abandonment. The relative importance of wilderness metrics differed regionally and was strongly connected to local environmental and socio‐economic contexts. Large areas of projected abandonment were often located in or around Natura 2000 sites. Based on these results, we argue that management should be tailored to restore the aspects of wilderness that are lacking in each region. There are many remaining challenges regarding biodiversity in Europe, but megafauna species are already recovering. To further potentiate large‐scale rewilding, Natura 2000 management would need to incorporate rewilding approaches. Our framework can be applied to assessing rewilding opportunities and challenges in other world regions, and our results could guide redirection of subsidies to manage social‐ecological systems.  相似文献   
226.

The Internet of Things (IoT) triggers new types of cyber risks. Therefore, the integration of new IoT devices and services requires a self-assessment of IoT cyber security posture. By security posture this article refers to the cybersecurity strength of an organisation to predict, prevent and respond to cyberthreats. At present, there is a gap in the state of the art, because there are no self-assessment methods for quantifying IoT cyber risk posture. To address this gap, an empirical analysis is performed of 12 cyber risk assessment approaches. The results and the main findings from the analysis is presented as the current and a target risk state for IoT systems, followed by conclusions and recommendations on a transformation roadmap, describing how IoT systems can achieve the target state with a new goal-oriented dependency model. By target state, we refer to the cyber security target that matches the generic security requirements of an organisation. The research paper studies and adapts four alternatives for IoT risk assessment and identifies the goal-oriented dependency modelling as a dominant approach among the risk assessment models studied. The new goal-oriented dependency model in this article enables the assessment of uncontrollable risk states in complex IoT systems and can be used for a quantitative self-assessment of IoT cyber risk posture.

  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