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   585篇
  免费   13篇
  国内免费   5篇
安全科学   24篇
废物处理   30篇
环保管理   134篇
综合类   70篇
基础理论   126篇
环境理论   3篇
污染及防治   163篇
评价与监测   25篇
社会与环境   19篇
灾害及防治   9篇
  2023年   3篇
  2021年   7篇
  2020年   11篇
  2019年   9篇
  2018年   13篇
  2017年   16篇
  2016年   12篇
  2015年   12篇
  2014年   9篇
  2013年   90篇
  2012年   13篇
  2011年   32篇
  2010年   18篇
  2009年   26篇
  2008年   27篇
  2007年   27篇
  2006年   19篇
  2005年   18篇
  2004年   17篇
  2003年   22篇
  2002年   14篇
  2001年   12篇
  2000年   6篇
  1999年   4篇
  1998年   8篇
  1997年   12篇
  1996年   7篇
  1995年   10篇
  1994年   8篇
  1993年   5篇
  1991年   4篇
  1990年   9篇
  1989年   7篇
  1988年   3篇
  1987年   4篇
  1986年   4篇
  1985年   5篇
  1984年   11篇
  1983年   7篇
  1982年   8篇
  1981年   8篇
  1979年   7篇
  1976年   4篇
  1975年   4篇
  1974年   3篇
  1973年   4篇
  1971年   3篇
  1968年   2篇
  1961年   2篇
  1960年   2篇
排序方式: 共有603条查询结果,搜索用时 15 毫秒
91.
Two northern Minnesota lakes that had been studied in detail 22 years earlier (1958) were restudied to determine the extent of alteration in ecological conditions. Approximately one year after the original investigation, a coal-fired power plant, which incremented sulfate loading by about 6 kg/ha-yr, began operation nine miles away. These lakes lie within a region judged susceptible to acidic precipitation, though each lake, based on its buffering capacity, would be judged only moderately sensitive. In spite of the influence of this plant and other anthropogenic inputs, the change in lake ecology was apparently minimal. Water clarity decreased in both lakes and some alteration in zooplankton community structure was observed. The long-term utility of lake surveys depends upon how carefully and completely conditions can be reconstructed from records and reports. Past surveys generally omit measures of variability for the data, allowing only qualitative comparisons to be drawn. In order to judge the graded responses of aquatic ecosystems, necessary to sound management, quantitative measures are needed.Deceased.  相似文献   
92.
A systems approach was used to evaluate environmental loading of Cryptosporidium oocysts on five coastal dairies in California. One aspect of the study was to determine Cryptosporidium oocyst concentrations and loads for 350 storm runoff samples from dairy high use areas collected over two storm seasons. Selected farm factors and beneficial management practices (BMPs) associated with reducing the Cryptosporidium load in storm runoff were assessed. Using immunomagnetic separation (IMS) with direct fluorescent antibody (DFA) analysis, Cryptosporidium oocysts were detected on four of the five farms and in 21% of storm runoff samples overall. Oocysts were detected in 59% of runoff samples collected near cattle less than 2 mo old, while 10% of runoff samples collected near cattle over 6 mo old were positive. Factors associated with environmental loading of Cryptosporidium oocysts included cattle age class, 24 h precipitation, and cumulative seasonal precipitation, but not percent slope, lot acreage, cattle stocking number, or cattle density. Vegetated buffer strips and straw mulch application significantly reduced the protozoal concentrations and loads in storm runoff, while cattle exclusion and removal of manure did not. The study findings suggest that BMPs such as vegetated buffer strips and straw mulch application, especially when placed near calf areas, will reduce environmental loading of fecal protozoa and improve stormwater quality. These findings are assisting working dairies in their efforts to improve farm and ecosystem health along the California coast.  相似文献   
93.
Optimal development programs that explicitly account for the environment impacts of extracting energy resources are analyzed. Possibilities of storing the resources above ground once it has been extracted are examined When environmental disruption results from resource extraction, as in the case of strip mining or drilling for oil, then the socially optimal rates of resource consumption and extraction depend on the type and severity of the environmental impact and on the prospects of storing the resource above ground.  相似文献   
94.
95.
96.
The ability of many insects to learn has been documented. However, a limited number of studies examining associative learning in medically important arthropods has been published. Investigations into the associative learning capabilities of Culex quinquefasciatus Say were conducted by adapting methods commonly used in experiments involving Hymenoptera. Male and female mosquitoes were able to learn a conditioned stimulus that consisted of an odor not normally encountered in nature (synthetic strawberry or vanilla extracts) in association with an unconditioned stimulus consisting of either a sugar (males and females) or blood (females) meal. Such information could lead to a better understanding of the ability of mosquitoes to locate and select host and food resources in nature.  相似文献   
97.
Dynamics in the global protected-area estate since 2004   总被引:1,自引:0,他引:1  
Nations of the world have committed to a number of goals and targets to address global environmental challenges. Protected areas have for centuries been a key strategy in conservation and play a major role in addressing current challenges. The most important tool used to track progress on protected-area commitments is the World Database on Protected Areas (WDPA). Periodic assessments of the world's protected-area estate show steady growth over the last 2 decades. However, the current method, which uses the latest version of the WDPA, does not show the true dynamic nature of protected areas over time and does not provide information on sites removed from the WDPA. In reality, this method can only show growth or remain stable. We used GIS tools in an approach to assess protected-area change over time based on 12 temporally distinct versions of the WDPA that quantify area added and removed from the WDPA annually from 2004 to 2016. Both the narrative of continual growth of protected area and the counter-narrative of protected area removal were overly simplistic. The former because growth was almost entirely in the marine realm and the latter because some areas removed were reprotected in later years. On average 2.5 million km2 was added to the WDPA annually and 1.1 million km2 was removed. Reasons for the inclusion and removal of protected areas in the WDPA database were in part due to data-quality issues but also to on-the-ground changes. To meet the 17% protected-area component of Aichi Biodiversity Target 11 by 2020, which stood at 14.7% in 2016, either the rate of protected-area removal must decrease or the rate of protected-area designation and addition to the WDPA must increase.  相似文献   
98.
Forty-two communities in rural Alaska are considered unserved or underserved with water and sewer infrastructure. Many challenges exist to provide centralized piped water and sewer infrastructure to the homes, and they are exacerbated by decreasing capital funding. Unserved communities in rural Alaska experience higher rates of disease, supporting the recommendation that sanitation infrastructure should be provided. Organizations are pursuing alternative solutions to conventional piped water and sewer in order to maximize water use and reuse for public health. This paper reviews initiatives led by the State of Alaska, the Alaska Native Tribal Health Consortium, and the Yukon Kuskokwim Health Corporation to identify and develop potential long-term solutions appropriate and acceptable to rural communities. Future developments will likely evolve based on the lessons learned from the initiatives. Recommendations include Alaska-specific research needs, increased end-user participation in the design process, and integrated monitoring, evaluation, and information dissemination in future efforts.  相似文献   
99.
I present an attributional approach to understanding how people perceive and respond to the effects of others' relationships in the workplace by suggesting that people perceive others' relationships to be causal sources of workplace outcomes. Specifically, I suggest that individuals' responses to negative outcomes at work can be better understood by differentiating between two types of external attributional explanations: external relational attributions and external nonrelational attributions. This research focuses on the conceptual development of external relational attributions, which are defined as those attributional explanations made for outcomes or behaviors experienced or observed by a focal individual that locate the cause of an outcome within the relationship between two others (people, groups, organizations, or any combination), not including the focal individual. Further, I propose situational antecedents and behavioral outcomes of external relational attributions, with an emphasis on individuals' behaviors toward others' relationships. Lastly, I highlight the advantages of considering the role of others' relationships when applying attribution theory to a variety of organizational phenomena and present directions for future research.  相似文献   
100.
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