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   28997篇
  免费   364篇
  国内免费   559篇
安全科学   776篇
废物处理   1312篇
环保管理   4060篇
综合类   4557篇
基础理论   7907篇
环境理论   11篇
污染及防治   6811篇
评价与监测   1899篇
社会与环境   2419篇
灾害及防治   168篇
  2023年   136篇
  2022年   302篇
  2021年   265篇
  2020年   244篇
  2019年   240篇
  2018年   882篇
  2017年   855篇
  2016年   984篇
  2015年   516篇
  2014年   709篇
  2013年   2081篇
  2012年   1039篇
  2011年   1846篇
  2010年   1300篇
  2009年   1431篇
  2008年   1665篇
  2007年   1882篇
  2006年   989篇
  2005年   900篇
  2004年   889篇
  2003年   891篇
  2002年   876篇
  2001年   939篇
  2000年   711篇
  1999年   412篇
  1998年   296篇
  1997年   301篇
  1996年   314篇
  1995年   374篇
  1994年   289篇
  1993年   274篇
  1992年   252篇
  1991年   262篇
  1990年   249篇
  1989年   242篇
  1988年   210篇
  1987年   199篇
  1986年   199篇
  1985年   201篇
  1984年   250篇
  1983年   200篇
  1982年   221篇
  1981年   216篇
  1980年   171篇
  1979年   192篇
  1978年   122篇
  1977年   127篇
  1974年   125篇
  1973年   124篇
  1972年   138篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
New data on the composition of surface assemblages of plant macroremains from soil and swamp samples have been obtained in the study of geomorphologically different localities in the middle reaches of the Nizhnyaya Tunguska River. The results of paleocarpological analysis of forest soil sections supported by relevant palynological and geochronological data are presented. Natural changes of the forest cover over the past 2400 years and quantitative characteristics of the paleoclimate during each stage are described.Translated from Ekologiya, No. 1, 2005, pp. 3–10.Original Russian Text Copyright © 2005 by Koshkarova, Koshkarov.  相似文献   
83.
84.
Prader–Willi syndrome (PWS) results from either paternal deletion of 15q11–q13, or maternal uniparental disomy (UPD) of chromosome 15 or imprinting center mutation. Prenatal diagnosis of PWS is currently indicated for chromosomal parental translocation involving chromosome 15 and for decreased fetal movements during the third trimester of gestation. Here we present the prenatal diagnosis of PWS during the first trimester of gestation and autopsy findings. Chorionic villus sampling (CVS) was performed for advanced maternal age at 13 weeks' gestation. CVS showed mosaicism including cells with a normal karyotype and cells with trisomy 15. Amniocentesis showed cells with a normal karyotype. Molecular analysis demonstrated that the fetus had a typical PWS abnormal methylation profile and maternal disomy for chromosome 15. Fetal ultrasound examination showed slightly enlarged lateral ventricles and hypoplasic male external genitalia without intra-uterine growth retardation. The autopsy showed a eutrophic male fetus with facial dysmorphy, hypoplasic genitalia, abnormal position of both feet and posterior hypoplasia of the corpus callosum. This report points out that in a karyotypically normal fetus with ambiguous male external genitalia and cerebral anomalies, extensive cytogenetic and molecular biology studies are strongly recommended because of risk of PWS. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
85.
86.
87.
88.
89.
90.
Guzman N  Paz MX  Paz MI  Moreno NR  Nino F 《Disasters》1989,13(2):153-164
In the past 20 years a variety of indices have been suggested for measuring the severity of trauma, however none of them meets the requirement of being a simple and objective instrument that can be utilized efficiently by lay persons and providers of health services without previous experience in triaging. A new system has been proposed which meets this requirement and which has been validated with 197 injured persons at the emergency ward of the Valle University Hospital in Call, Colombia. The instrument showed a high level of concordance with the conventional triaging method and classifies victims into four categories: critical with recovery unlikely, critical but recoverable, moderately serious, and ambulatory. There is discussion on the reliability of this instrument and it is recommended that it be validated with victims from larger disasters. Regardless, it has the advantage of being specific and free of the subjectivity that characterizes other indices.  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