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   213篇
  免费   10篇
  国内免费   2篇
安全科学   16篇
废物处理   12篇
环保管理   51篇
综合类   38篇
基础理论   41篇
污染及防治   44篇
评价与监测   15篇
社会与环境   5篇
灾害及防治   3篇
  2023年   5篇
  2022年   5篇
  2021年   3篇
  2020年   1篇
  2019年   1篇
  2018年   3篇
  2017年   7篇
  2016年   13篇
  2015年   10篇
  2014年   8篇
  2013年   14篇
  2012年   13篇
  2011年   11篇
  2010年   8篇
  2009年   11篇
  2008年   12篇
  2007年   15篇
  2006年   13篇
  2005年   11篇
  2004年   5篇
  2003年   9篇
  2002年   8篇
  2001年   6篇
  2000年   2篇
  1999年   2篇
  1997年   4篇
  1996年   2篇
  1995年   1篇
  1994年   1篇
  1993年   2篇
  1992年   1篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1987年   6篇
  1986年   2篇
  1985年   1篇
  1983年   3篇
  1981年   1篇
  1941年   1篇
排序方式: 共有225条查询结果,搜索用时 15 毫秒
81.
Geographically isolated wetlands (GIWs) are wetlands completely surrounded by uplands. While common throughout the United States (U.S.), there have heretofore been no nationally available, spatially explicit estimates of GIW extent, complicating efforts to understand the myriad biogeochemical, hydrological, and habitat functions of GIWs and hampering conservation and management efforts at local, state, and national scales. We used a 10‐m geospatial buffer as a proxy for hydrological or ecological connectivity of National Wetlands Inventory palustrine and lacustrine wetland systems to nationally mapped and available stream, river, and lake data. We identified over 8.3 million putative GIWs across the conterminous U.S., encompassing nearly 6.5 million hectares of wetland resources (average size 0.79 ± 4.81 ha, median size 0.19 ha). Putative GIWs thus represent approximately 16% of the freshwater wetlands of the conterminous U.S. The water regime for the majority of the putative GIWs was temporarily or seasonally flooded, suggesting a vulnerability to ditching or hydrologic abstraction, sedimentation, or alterations in precipitation patterns. Additional analytical applications of this readily available geospatially explicit mapping product (e.g., hydrological modeling, amphibian metapopulation, or landscape ecological analyses) will improve our understanding of the abundance and extent, effect, connectivity, and relative importance of GIWs to other aquatic systems of the conterminous U.S.  相似文献   
82.
Interviews were carried out with Japanese firms and environmental agencies regarding their current practices regarding life-cycle assessment (LCA). The results of this informal survey are compared with an executive survey of U.S. Fortune 500 companies. The findings show that Japanese LCA activity has increased rapidly over the past four years with several government agencies involved in LCA. Private industry has also founded LCA forums and recycling centers. The primary Japanese LCA interests include use in ecodesign and ecolabeling with the main environmental efforts focused on design for environment. Solid waste was identified as the most significant current environmental problem in Japan, in contrast to the United States where atmospheric and liquid discharges are ranked equally important. Neither the Japanese nor EPA plan to use LCA as a regulatory tool. This article summarizes several LCA case studies performed in Japan and lists the agencies involved in LCA development, ISO 14000, and ecoauditing/ecolabeling. Some recent Japanese legislation affecting LCA is also reviewed.  相似文献   
83.
The combination of breeding for increased production and the intensification of housing conditions have resulted in increased occurrence of behavioral, physiological, and immunological disorders. These disorders affect health and welfare of production animals negatively. For future livestock systems, it is important to consider how to manage and breed production animals. In this paper, we will focus on selective breeding of laying hens. Selective breeding should not only be defined in terms of production, but should also include traits related to animal health and welfare. For this we like to introduce the concept of robustness. The concept of robustness includes individual traits of an animal that are relevant for health and welfare. Improving robustness by selective breeding will increase (or restore) the ability of animals to interact successfully with the environment and thereby to make them more able to adapt to an appropriate husbandry system. Application of robustness into a breeding goal will result in animals with improved health and welfare without affecting their integrity. Therefore, in order to be ethically acceptable, selective breeding in animal production should accept robustness as a breeding goal. L. Star, E. D. Ellen contributed equally to this work. Star belongs to the Adaptation Physiology Group, Wageningen University, and the rest of the authors belong to the Animal Breeding and Genomics Centre, Wageningen University.  相似文献   
84.
White lupine (Lupinus albus L.) was used as a phosphorus (P)-efficient model plant to study the effects of elevated atmospheric CO(2) concentrations on (i) P acquisition, (ii) the related alterations in root development and rhizosphere chemistry, and (iii) the functional and structural diversity of rhizosphere microbial communities, on a P-deficient calcareous subsoil with and without soluble P fertilization. In both +P (80 mg P kg(-1)) and -P treatments (no added P), elevated CO(2) (800 micromol mol(-1)) increased shoot biomass production by 20 to 35% and accelerated the development of cluster roots, which exhibit important functions in chemical mobilization of sparingly soluble soil P sources. Accordingly, cluster root formation was stimulated in plants without P application by 140 and 60% for ambient and elevated CO(2) treatments, respectively. Intense accumulation of citrate and increased activities of acid and alkaline phosphatases, but also of chitinase, in the rhizosphere were mainly confined to later stages of cluster root development in -P treatments. Regardless of atmospheric CO(2) concentrations, there was no significant effect on accumulation of citrate or on selected enzyme activities of C, N, and P cycles in the rhizosphere of individual root clusters. Discriminant analysis of selected enzyme activities revealed that mainly phosphatase and chitinase contributed to the experimental variance (81.3%) of the data. Phosphatase and chitinase activities in the rhizosphere might be dominated by the secretion from cluster roots rather than by microbial activity. Alterations in rhizosphere bacterial communities analyzed by denaturing gradient gel electrophoresis (DGGE) were related with the intense changes in root secretory activity observed during cluster root development but not with elevated CO(2) concentrations.  相似文献   
85.
Individuals with Down syndrome (DS) are diagnosed with autism spectrum disorder (ASD) at a significantly higher frequency than the typical population. The differentiation of ASD symptoms from those of severe intellectual disability presents diagnostic challenges, which have led to more refined methods in the clinical evaluation of ASD in DS. These improved phenotypic characterization methods not only provide better diagnosis of ASD in DS, but may also be useful in elucidating the etiology of the increased prevalence of ASD in DS. Because all individuals with the classic presentation of DS have trisomy 21, it is possible that those with co-occurring DS and ASD may have additional genetic variants which can act as modifiers of the phenotype, leading to the development of ASD. © 2016 John Wiley & Sons, Ltd.  相似文献   
86.
87.
88.
89.
90.
Food and Environmental Virology - Rural environments lack basic sanitation services. Facilities for obtaining water and disposing sewage are often under the initiative of each resident, who may not...  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