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   45526篇
  免费   436篇
  国内免费   354篇
安全科学   1219篇
废物处理   1789篇
环保管理   6369篇
综合类   6605篇
基础理论   13006篇
环境理论   24篇
污染及防治   11620篇
评价与监测   2825篇
社会与环境   2568篇
灾害及防治   291篇
  2022年   263篇
  2021年   300篇
  2020年   230篇
  2019年   321篇
  2018年   989篇
  2017年   932篇
  2016年   1146篇
  2015年   749篇
  2014年   1047篇
  2013年   3288篇
  2012年   1421篇
  2011年   2310篇
  2010年   1782篇
  2009年   1854篇
  2008年   2251篇
  2007年   2528篇
  2006年   1692篇
  2005年   1501篇
  2004年   1443篇
  2003年   1408篇
  2002年   1431篇
  2001年   1687篇
  2000年   1201篇
  1999年   740篇
  1998年   589篇
  1997年   576篇
  1996年   614篇
  1995年   659篇
  1994年   602篇
  1993年   547篇
  1992年   527篇
  1991年   505篇
  1990年   506篇
  1989年   534篇
  1988年   464篇
  1987年   419篇
  1986年   371篇
  1985年   401篇
  1984年   399篇
  1983年   430篇
  1982年   438篇
  1981年   391篇
  1980年   332篇
  1979年   371篇
  1978年   301篇
  1977年   254篇
  1976年   257篇
  1975年   254篇
  1973年   238篇
  1972年   273篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
121.
122.
123.
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   
124.
125.
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   
126.
127.
128.
   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   
129.
130.
Four microbial isolates, OP2, OP3, OP6, and OP7, of earthworm casts ofPontoscolex corethrurus were found to be acid tolerant actinomycetes and efficient rock phosphate (RP) solubilizers that could grow fast on NH4Cl-enriched or N-free carboxymethyl cellulose or glucose as sole carbon source. CMC (carboxymethyl cellulose) induced production of extracellular cellulase enzyme and the production of reducing sugar in all the isolates. RP solubilizing power was observed to be inversely related to glucose consumption. The most efficient RP solubilizer was found to consume the least glucose. Growth was faster on cellulose than on glucose media. N-free CMC induced greater glucose production than NH4Cl-enriched CMC medium. Both CMC and glucose media were acidified by all the isolates, however, RP solubilizing power decreased with acidification. Solubilization power was greatest with isolate OP7, which also produced the greatest amount of reducing sugar per gram CMC. Both RP solubilizing power and the cellulolytic efficiency varied among isolates. A minimum of 631 μg P/0.1 g RP and a maximum of 951.4 μg P/0.1 g RP was recorded.  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