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   525篇
  免费   14篇
  国内免费   4篇
安全科学   28篇
废物处理   30篇
环保管理   72篇
综合类   45篇
基础理论   127篇
污染及防治   162篇
评价与监测   39篇
社会与环境   30篇
灾害及防治   10篇
  2023年   6篇
  2022年   10篇
  2021年   10篇
  2020年   8篇
  2019年   10篇
  2018年   13篇
  2017年   13篇
  2016年   20篇
  2015年   17篇
  2014年   16篇
  2013年   47篇
  2012年   26篇
  2011年   44篇
  2010年   29篇
  2009年   32篇
  2008年   28篇
  2007年   33篇
  2006年   35篇
  2005年   34篇
  2004年   19篇
  2003年   14篇
  2002年   17篇
  2001年   4篇
  2000年   3篇
  1999年   6篇
  1998年   4篇
  1997年   6篇
  1996年   5篇
  1995年   6篇
  1994年   6篇
  1993年   3篇
  1992年   4篇
  1991年   1篇
  1990年   3篇
  1989年   1篇
  1985年   2篇
  1983年   1篇
  1982年   2篇
  1981年   2篇
  1980年   1篇
  1974年   1篇
  1964年   1篇
排序方式: 共有543条查询结果,搜索用时 15 毫秒
351.
352.
The only remaining wild population of the endangered Whooping Crane ( Grus americana ) winters in salt marsh habitats of the Texas (U.S.) coast. Whooping Cranes are known to respond and utilize nearby upland habitats after a tire treatment has been applied. We investigated several factors that may attract Whooping Cranes to recently burned sites at Aransas National Wildlife Refuge between 1982 and 1994 and whether cranes utilize upland habitats primarily in response to a recent fire treatment or whether they occur regularly on uplands regardless of burning. We evaluated the effect of different years, burn site location, date of burn, and acorn production on crane use of specific burn sites. Crane use was determined with ground surveys from 1982 through 1985 and from weekly aerial surveys between 1986 and 1994. Whooping Cranes used fire-treated upland habitats to a significantly greater extent than unburned sites. The response of cranes to recently burned sites was greatest immediately after fire treatment and declined with time. No significant difference was found in crane use of burned sites among different years. Similarly, time of burn and acorn production had no significant effect on crane use of fire-treated habitats. Crane use among specific burn units differed significantly. We suggest that Whooping Cranes may be using fire-treated upland habitats to feed on recently killed vertebrates and invertebrates plus recently exposed plant items. Because cranes primarily inhabit salt marsh habitats, the availability of alternate food sources may be of considerable importance, particularly during years when marsh foods are scarce. But because it appears that areas must be burned to facilitate use by Whooping Cranes, we suggest that the extent of prescribed burning be based on reduced availability of marsh food resources and not on acorn production estimates alone.  相似文献   
353.
正The global and regional redistribution of mercury within the environment is of primary importance to both natural ecosystems and human health.The ratification of the Minamata Convention on Mercury by 91 parties represents a key step in protecting ecosystems and future societies from increasing mercury accumulation.However,key to the continued quanti-  相似文献   
354.
355.
356.
357.
The project focuses on the efficiency of combined technologies to reduce the release of micropollutants and bacteria into surface waters via sewage treatment plants of different size and via stormwater overflow basins of different types. As a model river in a highly populated catchment area, the river Schussen and, as a control, the river Argen, two tributaries of Lake Constance, Southern Germany, are under investigation in this project. The efficiency of the different cleaning technologies is monitored by a wide range of exposure and effect analyses including chemical and microbiological techniques as well as effect studies ranging from molecules to communities.  相似文献   
358.
This paper describes a case study in Flanders–Belgium on the reporting rate of road crashes. Crash data from three sources were compared: official crash data, data retrieved from an insurance company and newspaper articles. A sample of 140 injury crashes with motorcyclists from an insurance company was used as the reference category. The purpose was to explore factors that contribute to the likelihood of crashes (not) to be reported in official statistics and newspapers. Logistic regression analyses and chi-square tests were used to reveal differences in reporting rate according to some variables. About 80% of the crashes with severe injuries were reported in the official statistics whereas the reporting rate for crashes with slightly injured was about 55%. Newspapers covered about 50% of crashes with severe injuries. The reporting rate in both official statistics and newspapers increased with the severity of the crash.  相似文献   
359.
Outbound offending: The journey to crime and crime sprees   总被引:1,自引:0,他引:1  
Studies on crime and mobility primarily focus on local crime patterns. The city has long played an important role, whether analysing the offence or the offender. This paper goes beyond city boundaries and discusses ‘outbound offenders’, whose crime trips start in a city, but end outside. It is argued that a substantial proportion of crime trips follow this pattern, indicating that areas other than cities also provide interesting opportunities for property crime. We link outbound offending to a number of features that may explain crime travelling, including the target’s features and offender/offence features. We find that outbound offending mostly occurs towards affluent target regions and near motorways, as such confirming findings from previous research. We also find crime sprees to be indicative for mobile offending. Thus, mobile property offenders tend to compensate for travelled distances, not only by targeting affluent areas and using fast transportation means, but also by committing several successive offences, hereby reducing their relative transportation cost for each offence.  相似文献   
360.
Previous studies of loggerhead sea turtles have concluded that drifting longlines were the main threat for immature specimens in the western Mediterranean, because immature loggerhead sea turtles mainly inhabit oceanic waters. However, recent aerial surveys have revealed large numbers of immature loggerhead sea turtles over the continental shelf of eastern mainland Spain, where turtles are exposed to neritic fishing gears but not to drifting longlines. We satellite-tracked seven loggerhead sea turtles (minimum straight carapace length (SCLmin) range: 36.5–55.0 cm) to assess whether the turtles in this region are vagrants from the adjoining oceanic regions or whether these loggerheads mostly inhabit the continental shelf. Satellite-tracking revealed that six of the tagged turtles avoided the oceanic realm and made extended use of the continental shelf, whereas only one individual could be considered a true vagrant as it avoided the continental shelf and primarily used the oceanic habitat. These results are in sharp contrast with those previously reported for immature loggerhead sea turtles of similar size from the south-western Mediterranean and fit well a relaxed ontogenic model that was recently proposed for loggerhead sea turtles in the central Mediterranean. Furthermore, these results demonstrate the vulnerability of loggerhead sea turtles of eastern mainland Spain to neritic fishing gears, as three of the seven turtles died and one was bycaught incidentally while being tracked over the continental shelf.  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