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   54206篇
  免费   549篇
  国内免费   625篇
安全科学   1568篇
废物处理   2244篇
环保管理   7160篇
综合类   8675篇
基础理论   15153篇
环境理论   36篇
污染及防治   13544篇
评价与监测   3492篇
社会与环境   3164篇
灾害及防治   344篇
  2022年   436篇
  2021年   439篇
  2020年   349篇
  2019年   437篇
  2018年   1091篇
  2017年   1055篇
  2016年   1376篇
  2015年   930篇
  2014年   1309篇
  2013年   3968篇
  2012年   1771篇
  2011年   2736篇
  2010年   2111篇
  2009年   2172篇
  2008年   2638篇
  2007年   2844篇
  2006年   2051篇
  2005年   1785篇
  2004年   1697篇
  2003年   1751篇
  2002年   1643篇
  2001年   2045篇
  2000年   1424篇
  1999年   891篇
  1998年   678篇
  1997年   670篇
  1996年   679篇
  1995年   752篇
  1994年   748篇
  1993年   636篇
  1992年   656篇
  1991年   615篇
  1990年   653篇
  1989年   641篇
  1988年   559篇
  1987年   495篇
  1986年   423篇
  1985年   478篇
  1984年   484篇
  1983年   496篇
  1982年   482篇
  1981年   440篇
  1980年   360篇
  1979年   407篇
  1978年   358篇
  1977年   278篇
  1976年   285篇
  1975年   290篇
  1974年   257篇
  1972年   288篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
Nylund  G. M.  Pavia  H. 《Marine Biology》2003,143(5):875-882
We examined the chemical antifouling properties of four sublittoral red algae, Chondrus crispus, Delesseria sanguinea, Osmundea ramosissima, and Polyides rotundus, which are all rarely fouled in the field. Two different approaches were used. Firstly, we tested the effects of lipophilic crude extracts on the settlement behaviour of cyprid larvae of the co-existing barnacle Balanus improvisus. Secondly, in a settlement preference experiment, we tested whether B. improvisus cyprid larvae settle on living algae when given a choice between natural algal surfaces and control surfaces. With this procedure, we were able to test both if the algae inhibit recruitment of cyprids, and if this inhibition is a result of chemistry. The settlement of B. improvisus larvae was strongly inhibited at concentrations estimated to be potentially ecologically relevant for all of the tested extracts. However, only C. crispus significantly inhibited settlement in the preference experiment, even though there was also a tendency for settlement inhibition on P. rotundus and O. ramosissima. In contrast, D. sanguinea seemed to stimulate settlement. This contradiction probably resulted from an extraction of metabolites that naturally occur only inside the alga. However, as this study shows, a combination of settlement assays with whole-cell extracts and preference tests of ecologically relevant fouling organisms on natural algal and control surfaces may be a useful procedure to avoid erroneous conclusions regarding natural antifouling roles of compounds based on settlement assays with only whole-cell extracts. Furthermore, this study also shows that production of inhibitory metabolites may explain the low degree of fouling, especially by B. improvisus, on C. crispus.Communicated by L. Hagerman, Helsingør  相似文献   
133.
134.
Four small- to medium-sized municipalities in the south-east of Sweden were chosen for a 5-year study of their Local Agenda 21 (LA21) processes. The study shows that the LA21 processes have instigated many new ideas, brought fields together and introduced new subjects into the municipal world. In the decisions of the local governments environmental considerations are treated seriously. There are signs of an extended dialogue and of public influence, especially within fields where citizens are directly involved. LA21 does not seem to have great influence on which natural resources are dealt with, but does on how they are dealt with. New stakeholders within and outside the municipal organization have been identified through the LA21 processes, and more comprehensive ways of solving problems and a positive climate for testing new ideas have been created. In these respects LA21 has been and will be a significant support to the development of appropriate natural resource management at the local level.  相似文献   
135.
136.
137.
In a 1981 survey of 436 Florida citrus growers, 27 pesticide related poisoning incidents were reported that were to have taken place within one year of the interview date. From these reports it is possible to estimate that there are 376 citrus fieldworker related poisonings per year in Florida. This number of estimated poisonings may be developed into an incidence rate of 113 fieldworker poisonings per 10,000 fieldworkers.  相似文献   
138.
139.
   Global change, i.e. the mega-process radically transforming the relationship between nature and human civilization since the end of World War II, is investigated from the point of view of systems analysis. It is argued that this unbridled process should rather be domesticated by planetary control strategies transpiring from a new science called “geocybernetics”. The formal aspects of geocybernetic theory are sketched and illustrated in a tutorial theatre world reflecting the overall environment and development problematic. Within this setting a straightforward operationalization of the sweeping “sustainable development” ideal through a set of concise paradigms can be achieved. Evidence is provided that geocybernetics is actually feasible on the basis of earth system modelling and fuzzy-control techniques.  相似文献   
140.
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