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   39272篇
  免费   370篇
  国内免费   302篇
安全科学   1037篇
废物处理   1580篇
环保管理   4840篇
综合类   8698篇
基础理论   9712篇
环境理论   13篇
污染及防治   9591篇
评价与监测   2324篇
社会与环境   1921篇
灾害及防治   228篇
  2022年   312篇
  2021年   259篇
  2019年   264篇
  2018年   504篇
  2017年   520篇
  2016年   766篇
  2015年   599篇
  2014年   923篇
  2013年   2910篇
  2012年   1086篇
  2011年   1504篇
  2010年   1299篇
  2009年   1401篇
  2008年   1526篇
  2007年   1606篇
  2006年   1384篇
  2005年   1216篇
  2004年   1180篇
  2003年   1172篇
  2002年   1114篇
  2001年   1473篇
  2000年   1048篇
  1999年   652篇
  1998年   442篇
  1997年   486篇
  1996年   495篇
  1995年   574篇
  1994年   563篇
  1993年   482篇
  1992年   491篇
  1991年   506篇
  1990年   534篇
  1989年   501篇
  1988年   400篇
  1987年   396篇
  1986年   386篇
  1985年   378篇
  1984年   389篇
  1983年   384篇
  1982年   383篇
  1981年   386篇
  1980年   322篇
  1979年   363篇
  1978年   280篇
  1977年   284篇
  1975年   249篇
  1974年   260篇
  1973年   280篇
  1972年   248篇
  1967年   276篇
排序方式: 共有10000条查询结果,搜索用时 656 毫秒
691.
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   
692.
693.
An interdisciplinary approach based on high-resolution physical stratigraphy, biostratigraphy, organic matter analysis and clay mineralogy has been applied to the mixed siliciclastic/carbonate Kimmeridgian/Tithonian deposits of the Boulonnais (north-western France). These rocks are the age-equivalents of some of the offshore marine source rocks of the North Sea and were deposited in an overall storm-dominated homoclinal ramp setting which may represent one of the most shore-proximal sediments of this age cropping out in north-western Europe. Comparison with data from the Yorkshire, Dorset, Lorraine and Aquitaine areas allows the discrimination of three major transgressive-regressive sediment packages with disconformities of interregional extent: (1) from the Baylei Zone to top Eudoxus Zone; (2) from the Autissiodorensis Zone to base Scitulus Zone; (3) from the upper Scitulus Zone to the Pectinatus Zone. The lower two regionally correlative disconformities correspond to the sequence boundaries at the top of the Eudoxus Zone and the top of the Autissiodorensis Zone, formed by high-frequency relative sea-level variations during the periods of maximum transgression of the platform. The latter disconformity (the P1 nodule bed) reflects a major tectonically induced reorganization of the north-west European intrashelf sedimentary basin, characterized by a shift in both the location of the main depocentre and the sources of sediment production.  相似文献   
694.
Anticardiolipin antibodies were measured in 60 pregnant women with acute parvovirus B19 infection. Test results for eight (13.3 per cent) women were positive for anticardiolipin antibody. Six of these eight women became negative later, yielding a prevalence of anticardiolipin antibodies of 3.3 per cent (2/60) 6 months after acute parvovirus B19 infection. Anticardiolipin antibody positivity was not associated with an increased risk of abortion, fetal death, or maternal complications. This study suggests that there is an elevated frequency of anticardiolipin antibodies in pregnant women with acute parvovirus B19, probably representing an epiphenomenon. However, this is not associated with an adverse maternal or perinatal outcome.  相似文献   
695.
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   
696.
Dedicated to Prof. Jürgen Aschoff on the occasion of his 80th birthday.  相似文献   
697.
698.
699.
700.
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