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   312篇
  免费   4篇
  国内免费   3篇
安全科学   25篇
废物处理   18篇
环保管理   84篇
综合类   28篇
基础理论   66篇
污染及防治   70篇
评价与监测   7篇
社会与环境   19篇
灾害及防治   2篇
  2021年   2篇
  2020年   2篇
  2019年   2篇
  2018年   4篇
  2017年   6篇
  2016年   2篇
  2015年   4篇
  2014年   6篇
  2013年   33篇
  2012年   11篇
  2011年   18篇
  2010年   9篇
  2009年   13篇
  2008年   8篇
  2007年   14篇
  2006年   19篇
  2005年   12篇
  2004年   15篇
  2003年   11篇
  2002年   8篇
  2001年   2篇
  2000年   5篇
  1999年   3篇
  1998年   2篇
  1997年   3篇
  1996年   3篇
  1995年   10篇
  1994年   6篇
  1993年   3篇
  1992年   6篇
  1991年   2篇
  1990年   4篇
  1988年   3篇
  1987年   4篇
  1986年   7篇
  1985年   4篇
  1984年   10篇
  1983年   7篇
  1982年   10篇
  1981年   2篇
  1979年   6篇
  1977年   2篇
  1975年   2篇
  1974年   1篇
  1972年   2篇
  1969年   1篇
  1968年   1篇
  1967年   1篇
  1962年   1篇
  1952年   1篇
排序方式: 共有319条查询结果,搜索用时 250 毫秒
111.
112.
113.
A survey of literature is given with respect to two problems: (1) resistance temperature adaptation in protozoans and multicellular animals at early stages of ontogenesis (cellular adaptations), and (2) changes in thermostability of somatic cells related to temperature adaptations of multicellular organisms. The following aspects are considered and discussed in detail: changes in resistance of protozoans to cold and heat, their causes and genetic controls; possible mechanisms of changes in thermostability of gametes, zygotes and multicellular organisms at oligolcellular stages of development; mechanisms of heat injury to cells; types of changes in heat-resistance of somatic cells from multi-cellular animals during individual life and during phylogenesis. The object of the review is to emphasize those aspects of temperature resistance adaptation of animals which have scarcely been investigated.  相似文献   
114.
Learning and adaptation in the management of waterfowl harvests   总被引:1,自引:0,他引:1  
A formal framework for the adaptive management of waterfowl harvests was adopted by the U.S. Fish and Wildlife Service in 1995. The process admits competing models of waterfowl population dynamics and harvest impacts, and relies on model averaging to compute optimal strategies for regulating harvest. Model weights, reflecting the relative ability of the alternative models to predict changes in population size, are used in the model averaging and are updated each year based on a comparison of model predictions and observations of population size. Since its inception the adaptive harvest program has focused principally on mallards (Anas platyrhynchos), which constitute a large portion of the U.S. waterfowl harvest. Four competing models, derived from a combination of two survival and two reproductive hypotheses, were originally assigned equal weights. In the last year of available information (2007), model weights favored the weakly density-dependent reproductive hypothesis over the strongly density-dependent one, and the additive mortality hypothesis over the compensatory one. The change in model weights led to a more conservative harvesting policy than what was in effect in the early years of the program. Adaptive harvest management has been successful in many ways, but nonetheless has exposed the difficulties in defining management objectives, in predicting and regulating harvests, and in coping with the tradeoffs inherent in managing multiple waterfowl stocks exposed to a common harvest. The key challenge now facing managers is whether adaptive harvest management as an institution can be sufficiently adaptive, and whether the knowledge and experience gained from the process can be reflected in higher-level policy decisions.  相似文献   
115.
Sexual selection is often characterized by polygynous breeding systems, size dimorphism, and skewed operational sex ratios. Koalas are sexually dimorphic in multiple domains, yet are absent from the literature on sexual selection and the structure of their mating system is unclear. We provide the first documentation of the strength of sexual selection in koalas by using microsatellite markers to identify sires. We combine the genetic data with morphological data in order to assess the role of body size in regulating reproductive output. During our 4-year study, 37% of males were identified as possible sires. Males were significantly larger than females, with sires heavier than non-sires. Male body mass correlated with annual reproductive output, with Crow’s Index of Opportunity for Selection revealing that variation in male reproductive success was threefold higher than that of females. Since it appears that male koalas rarely engage in physical confrontations over access to females, size dimorphism could be based upon non-agonistic competition and/or female mate choice. We propose that size dimorphism in koalas evolved as a consequence of endurance rivalry promoting vocal sexual advertisements that attract females. We suggest that female choice is a key mediator of male reproductive output.  相似文献   
116.
117.
Since the early 1990s the U.S. government has been developing and implementing public policies that advance the redevelopment of brownfields, and the recent passage of the Small Business Liability Relief and Brownfields Revitalization Act (SBLRBRA) will significantly advance efforts to integrate environmental contamination mitigation and redevelopment. Experience has demonstrated that successful redevelopment requires the collection, analysis, and interpretation of environmental data in a timely and cost‐effective manner in order to allow developers and lenders to efficiently use cleanup resources, develop response strategies that integrate cleanup with redevelopment, and support meaningful outreach to involved stakeholders. Recent advances in the science and technology of site characterization hold the promise of improved site characterization outcomes while saving time and money. One such advancement, the Triad Approach, combines systematic up‐front planning with the use of a dynamic field investigation process and the generation of real time data to allow in‐field decision making on sample location selection. This article describes an application of the Triad Approach to redevelopment of an urban greenway in Trenton, New Jersey. The Triad Approach, initiated through a partnership between the City of Trenton, New Jersey Department of Environmental Protection, New Jersey Institute of Technology, and the U.S. Environmental Protection Agency, demonstrated that this approach could accelerate the characterization of the 60‐acre, 11‐parcel project area. Environmental issues that were solved using the Triad Approach included the delineation of the extent of historic fill, determination of no further action for several areas of concern, detailed investigation of specific impacted areas and the acquisition of sufficient data to allow the city to make important decisions regarding remediation costs and property acquisition. © 2003 Wiley Periodicals, Inc.  相似文献   
118.
After first providing the meaning of psychological capital (PsyCap), we present a micro‐intervention to develop it. Drawn from hope, optimism, efficacy, and resiliency development, this PsyCap Intervention (PCI) is shown to have preliminary support for not only increasing participants' PsyCap, but also financial impact and high return on investment. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
119.
120.
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