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   40271篇
  免费   399篇
  国内免费   297篇
安全科学   1053篇
废物处理   1604篇
环保管理   5467篇
综合类   5848篇
基础理论   11750篇
环境理论   22篇
污染及防治   9983篇
评价与监测   2543篇
社会与环境   2465篇
灾害及防治   232篇
  2022年   252篇
  2021年   235篇
  2019年   262篇
  2018年   945篇
  2017年   885篇
  2016年   1045篇
  2015年   637篇
  2014年   837篇
  2013年   2675篇
  2012年   1230篇
  2011年   2110篇
  2010年   1632篇
  2009年   1662篇
  2008年   2020篇
  2007年   2282篇
  2006年   1460篇
  2005年   1334篇
  2004年   1235篇
  2003年   1267篇
  2002年   1251篇
  2001年   1561篇
  2000年   1091篇
  1999年   668篇
  1998年   536篇
  1997年   524篇
  1996年   536篇
  1995年   589篇
  1994年   526篇
  1993年   463篇
  1992年   495篇
  1991年   453篇
  1990年   473篇
  1989年   497篇
  1988年   415篇
  1987年   351篇
  1986年   316篇
  1985年   364篇
  1984年   352篇
  1983年   392篇
  1982年   380篇
  1981年   320篇
  1980年   287篇
  1979年   321篇
  1978年   259篇
  1977年   230篇
  1976年   235篇
  1975年   228篇
  1974年   212篇
  1973年   212篇
  1972年   226篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
Considerable empirical evidence supports recovery of reef fish populations with fishery closures. In countries where full exclusion of people from fishing may be perceived as inequitable, fishing‐gear restrictions on nonselective and destructive gears may offer socially relevant management alternatives to build recovery of fish biomass. Even so, few researchers have statistically compared the responses of tropical reef fisheries to alternative management strategies. We tested for the effects of fishery closures and fishing gear restrictions on tropical reef fish biomass at the community and family level. We conducted 1,396 underwater surveys at 617 unique sites across a spatial hierarchy within 22 global marine ecoregions that represented 5 realms. We compared total biomass across local fish assemblages and among 20 families of reef fishes inside marine protected areas (MPAs) with different fishing restrictions: no‐take, hook‐and‐line fishing only, several fishing gears allowed, and sites open to all fishing gears. We included a further category representing remote sites, where fishing pressure is low. As expected, full fishery closures, (i.e., no‐take zones) most benefited community‐ and family‐level fish biomass in comparison with restrictions on fishing gears and openly fished sites. Although biomass responses to fishery closures were highly variable across families, some fishery targets (e.g., Carcharhinidae and Lutjanidae) responded positively to multiple restrictions on fishing gears (i.e., where gears other than hook and line were not permitted). Remoteness also positively affected the response of community‐level fish biomass and many fish families. Our findings provide strong support for the role of fishing restrictions in building recovery of fish biomass and indicate important interactions among fishing‐gear types that affect biomass of a diverse set of reef fish families.  相似文献   
12.
13.
14.
15.
16.
Journal of Material Cycles and Waste Management - The traditional Chinese medicinal plant Magnolia officinalis has a wide range of applications; including more than 200 kinds of patented Chinese...  相似文献   
17.
Introduced and cryptogenic species in Port Phillip Bay, Victoria, Australia   总被引:4,自引:0,他引:4  
Port Phillip Bay (PPB) is a large (1,930 km2), temperate embayment in southern Victoria, Australia. Extensive bay-wide surveys of PPB have occurred since 1840. In 1995/1996 the Commonwealth Scientific and Industrial Research Organization (CSIRO) Centre for Research on Introduced Marine Pests (CRIMP) undertook an intensive evaluation of the region with the aims of developing a comprehensive species list of native and introduced biota and contrasting previous bay-wide assessments with a current field survey in order to detect new incursions and discern alterations to native communities. Two methods were used to meet these aims: a re-evaluation of regional museum collections and published research in PPB to identify and determine the timing of introductions; and field surveys for benthic (infauna, epifauna and encrusting) organisms between September 1995 to March 1996. One hundred and sixty introduced (99) and cryptogenic (61) species were identified representing over 13% of the recorded species of PPB. As expected, the majority of these are concentrated around the shipping ports of Geelong and Melbourne. Invasions within PPB appear to be increasing, possibly due to an increase in modern shipping traffic and an increase in aquaculture (historically associated with incidental introductions); however the records of extensive biological surveys suggest that this may, in part, be an artefact of sampling effort. In contrast to Northern Hemisphere studies, PPB (and Southern Hemisphere introductions in general) have significantly different suites of successfully invading taxa. PPB is presented as one of the most invaded marine ecosystems in the Southern Hemisphere.Communicated by M.S. Johnson, Crawley  相似文献   
18.
19.
20.
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