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   34593篇
  免费   356篇
  国内免费   254篇
安全科学   946篇
废物处理   1275篇
环保管理   4459篇
综合类   5416篇
基础理论   9561篇
环境理论   24篇
污染及防治   8862篇
评价与监测   2143篇
社会与环境   2303篇
灾害及防治   214篇
  2022年   235篇
  2021年   254篇
  2019年   260篇
  2018年   496篇
  2017年   505篇
  2016年   690篇
  2015年   568篇
  2014年   858篇
  2013年   2541篇
  2012年   1048篇
  2011年   1474篇
  2010年   1211篇
  2009年   1236篇
  2008年   1480篇
  2007年   1604篇
  2006年   1386篇
  2005年   1207篇
  2004年   1195篇
  2003年   1118篇
  2002年   1089篇
  2001年   1427篇
  2000年   1017篇
  1999年   613篇
  1998年   474篇
  1997年   487篇
  1996年   484篇
  1995年   533篇
  1994年   482篇
  1993年   439篇
  1992年   453篇
  1991年   413篇
  1990年   428篇
  1989年   446篇
  1988年   374篇
  1987年   332篇
  1986年   315篇
  1985年   339篇
  1984年   328篇
  1983年   345篇
  1982年   361篇
  1981年   304篇
  1980年   279篇
  1979年   307篇
  1978年   250篇
  1977年   220篇
  1976年   220篇
  1975年   213篇
  1974年   195篇
  1973年   199篇
  1972年   229篇
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
451.
452.
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   
453.
A mother affected with Apert's syndrome was diagnosed by ultrasound scan at 16–17 weeks to have a fetus similarly affected. The typical features of acrocephaly and symmetrical syndactyly were seen. This is probably the first time that this condition has been diagnosed at such a gestation by ultrasound scan. The patient decided to continue the pregnancy, and intrauterine death occurred at 34 weeks. The diagnosis was confirmed by pathological examination.  相似文献   
454.
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   
455.
IntroductionTheprocessofmunicipalsolidwaste(MSW)isoneofthemostseriousissuesintermsofenvironmentalprotection.ProcessingofMSWwithoutfurtherdisastrouscontaminationcanbeachievedonlyinmodernizedmeasures,suchasincineratingandenergygeneratingconcurrently(Shen…  相似文献   
456.
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   
457.
IntroductionChengdu KunmingRailwayLineislocatedonthemountainregionofsouthwesternChina .Therearealotofdebrisflowgulliesspreadingbesidethisrailwayline .Onsummer,thedebrisflowoftenburstsandthreatensthesafetyoftherailwaytransportation.In 1981,alarge scaledebris…  相似文献   
458.
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   
459.
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   
460.
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   
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