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   32220篇
  免费   367篇
  国内免费   248篇
安全科学   1020篇
废物处理   1149篇
环保管理   4805篇
综合类   4911篇
基础理论   9157篇
环境理论   25篇
污染及防治   8312篇
评价与监测   1907篇
社会与环境   1334篇
灾害及防治   215篇
  2022年   194篇
  2021年   197篇
  2019年   240篇
  2018年   420篇
  2017年   426篇
  2016年   621篇
  2015年   544篇
  2014年   734篇
  2013年   2487篇
  2012年   934篇
  2011年   1372篇
  2010年   1106篇
  2009年   1137篇
  2008年   1371篇
  2007年   1466篇
  2006年   1278篇
  2005年   1098篇
  2004年   1107篇
  2003年   1026篇
  2002年   1020篇
  2001年   1288篇
  2000年   920篇
  1999年   587篇
  1998年   471篇
  1997年   464篇
  1996年   495篇
  1995年   528篇
  1994年   495篇
  1993年   432篇
  1992年   450篇
  1991年   408篇
  1990年   403篇
  1989年   438篇
  1988年   380篇
  1987年   329篇
  1986年   305篇
  1985年   334篇
  1984年   307篇
  1983年   354篇
  1982年   366篇
  1981年   308篇
  1980年   267篇
  1979年   291篇
  1978年   252篇
  1977年   222篇
  1976年   214篇
  1975年   199篇
  1974年   180篇
  1973年   176篇
  1972年   207篇
排序方式: 共有10000条查询结果,搜索用时 500 毫秒
411.
412.
We report a 16-month-old boy with delayed psychomotor development, dysmorphic features, and failure to thrive. He had a mosaic karyotype detected prenatally: mos 46,XY/47,XY,+r(20)/47,XY,+20. After birth, the abnormal cell lines were confirmed in a number of tissues. The small ring chromosome was identified using fluorescence in situ hybridization as derived from chromosome 20. We compared our patient with previously reported cases of mosaic trisomy 20 detected prenatally and associated with an abnormal phenotype. In an attempt to characterize an r(20) syndrome, we also compared our case with two similar reports in the literature.  相似文献   
413.
Many authors have suggested that individuals affected by a terminal 1q deletion display a phenotypically definable and recognizable syndrome. In all of the 27 cases reported to date, the breakpoints were at band q42 or distally to it. To our knowledge, we report the first case of a terminal 1q41 deletion. Diagnosis was made prenatally by amniocentesis, following ultrasonographic diagnosis of omphalocele, cerebral ventriculomegaly, and increased nuchal fold thickness in a 19-week female fetus. Multiple facial and extremity features were consistent with the proposed distal 1q deletion syndrome; omphalocele, however, has not been reported previously. The absence of liver herniation into the omphalocele sac in this case supports the previously reported association of this finding with chromosomal anomalies.  相似文献   
414.
IntroductionTheprocessofmunicipalsolidwaste(MSW)isoneofthemostseriousissuesintermsofenvironmentalprotection.ProcessingofMSWwithoutfurtherdisastrouscontaminationcanbeachievedonlyinmodernizedmeasures,suchasincineratingandenergygeneratingconcurrently(Shen…  相似文献   
415.
Chinese life cycle impact assessment factors   总被引:5,自引:0,他引:5  
IntroductionLifecycleassessment(LCA)isanenvironmentalmanagementtoolthatisusedtoexamineandevaluatetheenvironmentalimpactsassociatedwiththeexistenceofproducts(Jensen,1998;Weidema,1997;Wenzel,1997).ThefocusofLCAisontheentirelifecycleoftheproduct,i.e.fromtheextracti…  相似文献   
416.
IntroductionChengdu KunmingRailwayLineislocatedonthemountainregionofsouthwesternChina .Therearealotofdebrisflowgulliesspreadingbesidethisrailwayline .Onsummer,thedebrisflowoftenburstsandthreatensthesafetyoftherailwaytransportation.In 1981,alarge scaledebris…  相似文献   
417.
Ten out of the 12 new EU members, used to belong to the so-called “former eastern block”, with a post WWII environmental policy radically different from the tendencies followed in Western Europe. The lack of conservation regulations has resulted in a rather harmful industrialization, regarding natural resources and environmental quality. While air pollution transfer is a phenomenon of transboundary level, there is a particular interest in examining the contribution of the new EU member states to the environmental pressure faced by the older member states and vice versa. The current study utilises the official data for almost 20 years published by the European Monitoring and Evaluation Program concerning the transboundary transfer of NOx and SO2 in order to analyse the situation and discuss the present and future environmental policy regarding air pollution.  相似文献   
418.
A multiple pregnancy of high rank may occur in a couple at risk for a Mendelian disorder. Prenatal diagnosis is hampered by the difficulty of (1) obtaining chorionic villi from each zygote arid (2) unequivocally relating each sample to the corresponding embryo. The calculation of the genetic risk according to the number of zygotes led us to propose a diagnostic strategy based on embryo reduction, a technique initially designed to improve the perinatal outcome of multiple pregnancies with normal embryos. We report a case in which this approach allowed rational use of first-trimester chorionic villus sampling in a quintuplet pregnancy at risk for non-ketotic hyperglycinaemia, resulting in the selective birth of unaffected twins.  相似文献   
419.
A case is described of the prenatal diagnosis of choroid plexus cysts at 17 weeks' gestation which persisted beyond 36 weeks but could not be detected after delivery. At birth the child was found to have trisomy 18.  相似文献   
420.
A number of different models of CF carrier screening have now been tested in pilot trials. Apart from opportunistic and cascade testing (which are strictly speaking not true forms of screening), the major programmes have been directed either to young adults in primary care or to pregnant women in antenatal clinics. Only in the latter form of screening has sufficient data been collected to allow conclusions to be reached on the optimum mode of delivery. It seems very probable that when CF carrier screening passes into routine service, it will be the antenatal couple model that is used.  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