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   33406篇
  免费   362篇
  国内免费   244篇
安全科学   886篇
废物处理   1411篇
环保管理   4562篇
综合类   5476篇
基础理论   9258篇
环境理论   14篇
污染及防治   8558篇
评价与监测   2068篇
社会与环境   1553篇
灾害及防治   226篇
  2022年   218篇
  2021年   242篇
  2019年   251篇
  2018年   428篇
  2017年   429篇
  2016年   689篇
  2015年   493篇
  2014年   750篇
  2013年   2588篇
  2012年   934篇
  2011年   1330篇
  2010年   1100篇
  2009年   1082篇
  2008年   1375篇
  2007年   1410篇
  2006年   1297篇
  2005年   1065篇
  2004年   1091篇
  2003年   1037篇
  2002年   983篇
  2001年   1282篇
  2000年   916篇
  1999年   549篇
  1998年   441篇
  1997年   438篇
  1996年   453篇
  1995年   520篇
  1994年   516篇
  1993年   451篇
  1992年   468篇
  1991年   443篇
  1990年   482篇
  1989年   461篇
  1988年   403篇
  1987年   375篇
  1986年   338篇
  1985年   331篇
  1984年   400篇
  1983年   355篇
  1982年   403篇
  1981年   363篇
  1980年   297篇
  1979年   323篇
  1978年   281篇
  1977年   233篇
  1975年   229篇
  1974年   251篇
  1973年   240篇
  1972年   247篇
  1971年   215篇
排序方式: 共有10000条查询结果,搜索用时 367 毫秒
741.
A case of spontaneous abortion after transcervical CVS is presented. Despite no evidence of bacteria in the vagina and cervix prior to sampling and the prophylactic use of Metronidazole, pathological evidence of chorioamnionitis was found. The implications of this are discussed.  相似文献   
742.
743.
The effects of reduced oxygen concentrations in the gas phase over the culture medium on colony formation and cell proliferation were investigated in high and low cell density primary and secondary cultures of amniotic fluid cells. Using two standard culture methods (25 cm2 plastic flasks and Leighton type tubes) a significantly reduced culture time was observed at high cell density for mass cultures by incubation within a low oxygen tension gas phase (2.5 per cent to 7.5 per cent O2) instead of conventional air (18 per cent O2). At low cell density colony formation was significantly enhanced in cultures grown at reduced oxygen tension. Using gas permeable membranes as support, lowering the oxygen tension from 7.5 per cent to 2.5 per cent yielded an increase in plating efficiency of cells from approximately 5 per cent to 25 per cent, whereas plating efficiency was less than 2 per cent for cells grown at ambient 18 per cent O2. It is suggested that low oxygen tension in the gas phase is an effective means of enhancing clonal growth in amniotic fluid cell cultures, thereby reducing both culture time and risk of culture failure.  相似文献   
744.
745.
Prenatal diagnosis of Sandhoff disease (infantile onset) at 16 weeks gestation has been made by detection and analysis of N-acetylglucosaminyl-oligosaccharides in amniotic fluid using high performance liquid chromatography. The elution profile for the branched chain oli-gosaccharides was identical with that obtained with neonatal and infantile Sandhoff urine. The concentration of the oligosaccharides in the fluid was 1/100th that of urine but when calculated relative to creatinine the levels were similar. No oligosaccharides were detected in normal control amniotic fluids (10 patients) at a similar gestational age. Based on the levels of the amniotic fluid oligosaccharides and the sensitivity limits of the assay, prenatal diagnosis of patients with the juvenile onset form of the disease may also be possible with this technique.  相似文献   
746.
747.
Tensile water     
Kuppers JR 《American scientist》1973,61(1):10; author reply 10
  相似文献   
748.
This paper presents data collected in Europe on 107 prenatal diagnoses of cystic fibrosis (CF) using linked DNA markers. To date, 38 children have been born without CF, as predicted, demonstrating the present rapid move from research to clinical genetic service.  相似文献   
749.
At 10 weeks' gestation, chorionic villus biopsy was obtained from a woman at risk for Sanfilippo type C disease. Acetyl-CoA: α-glucosaminide N-acetyltransferase activity was markedly deficient. The pregnancy was terminated at 12 weeks' gestation and follow-up study on fetal fibroblasts confirmed the diagnosis.  相似文献   
750.
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