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   34399篇
  免费   335篇
  国内免费   337篇
安全科学   963篇
废物处理   1556篇
环保管理   4480篇
综合类   4629篇
基础理论   9099篇
环境理论   8篇
污染及防治   9557篇
评价与监测   2491篇
社会与环境   2053篇
灾害及防治   235篇
  2022年   306篇
  2021年   340篇
  2020年   220篇
  2019年   294篇
  2018年   523篇
  2017年   515篇
  2016年   818篇
  2015年   619篇
  2014年   940篇
  2013年   2949篇
  2012年   1135篇
  2011年   1481篇
  2010年   1253篇
  2009年   1324篇
  2008年   1514篇
  2007年   1650篇
  2006年   1448篇
  2005年   1204篇
  2004年   1228篇
  2003年   1175篇
  2002年   1128篇
  2001年   1457篇
  2000年   1036篇
  1999年   617篇
  1998年   460篇
  1997年   429篇
  1996年   499篇
  1995年   475篇
  1994年   456篇
  1993年   419篇
  1992年   392篇
  1991年   358篇
  1990年   372篇
  1989年   372篇
  1988年   346篇
  1987年   297篇
  1986年   245篇
  1985年   266篇
  1984年   317篇
  1983年   303篇
  1982年   323篇
  1981年   276篇
  1980年   243篇
  1979年   284篇
  1978年   211篇
  1977年   188篇
  1976年   173篇
  1975年   170篇
  1973年   162篇
  1972年   160篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
441.
442.
443.
444.
445.
Unemployment effects of climate policy   总被引:1,自引:0,他引:1  
This paper models the unemployment effects of restrictions on greenhouse gas emissions, embodying two of the most significant types of short-term economic imperfections that generate unemployment: sectoral rigidities in labor mobility and sectoral rigidities in wage adjustments. A labor policy is also analyzed that would reduce the direct negative economic effects of the emissions restrictions.The politics of limiting greenhouse gas emissions are often dominated by relatively short-term considerations. Yet the current economic modeling of emissions limitations does not embody economic features that are likely to be particularly important in the short term, in particular, the politically sensitive unemployment rate. Moreover, only a few of these studies also consider policies that would offset the negative direct economic effects of emissions restrictions. For plausible estimates of the parameters, the model shows that, with the labor market imperfections, if there were no offsetting policies, the reductions in GNP in the U.S. in the first 10 years after emissions restrictions were imposed would be as much as 4%. However, if there were two policies, instead of just one: a counteracting labor market policy, as well as the emissions restrictions, the negative direct economic effects could be completely eliminated.  相似文献   
446.
XII Ecdysone Workshop July 22–26, 1996 Barcelona, Spain  相似文献   
447.
A fetus with multiple structural defects was seen at prenatal ultrasound examination. After termination of the pregnancy a bilateral cleft lip, alveolus, and palate; micrognathia; and webbed joints were seen. Fetal tissues showed indications of infection, intranuclear inclusion bodies, chronic stress, haemolysis, arterial wall damage, and profuse haemorrhage. Parvovirus B19 DNA was detected in fetal tissues by dot hybridization after polymerase chain reaction. The possibility of parvovirus B19 infection leading to congenital malformations is discussed.  相似文献   
448.
449.
1977~1998年间,在苏格兰西部的艾尔萨克雷格对收集到的塘鹅蛋中的多氯联苯(PCB)同类物进行了回顾性分析.对一些年份所收集的塘鹅蛋中每年选择8~10个对其PCB同类物浓度范围分别进行了分析.所有的同类物在几年之内浓度都降在低,但不同的同类物降解速率不同.  相似文献   
450.
An integrated approach was developed to determine the critical levels of air pollution for ecological standard setting based on the unified index of biological response, by taking into account the effects of all pollution components simultaneously. An empirical model of plant productivity was taken as the dose response model for gaseous pollutant effect on the productivity of trees and the annual productivity of plants was used as the above mentioned index. The CO2 increase in the lower atmosphere was considered to potentially increase plant productivity and NO2 was estimated as neutral while being dangerous for plants as a chemical precursor of ozone or as a source of acidification. The maximum permissible chronic O3 and SO2 levels for trees were estimated and it was found that O3 is much more phytotoxic, as compared to SO2 , with a rather narrow range of permissible levels (27-33 ppb) which complicates its monitoring and control.  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