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   264篇
  免费   2篇
  国内免费   4篇
安全科学   3篇
废物处理   1篇
环保管理   4篇
综合类   232篇
基础理论   9篇
污染及防治   9篇
评价与监测   7篇
社会与环境   1篇
灾害及防治   4篇
  2022年   1篇
  2021年   2篇
  2020年   4篇
  2019年   5篇
  2018年   1篇
  2017年   1篇
  2015年   1篇
  2014年   3篇
  2013年   11篇
  2012年   1篇
  2011年   2篇
  2010年   4篇
  2009年   4篇
  2008年   1篇
  2007年   2篇
  2006年   1篇
  2005年   6篇
  2003年   2篇
  1998年   1篇
  1995年   49篇
  1994年   27篇
  1993年   40篇
  1992年   43篇
  1991年   28篇
  1990年   16篇
  1989年   8篇
  1987年   1篇
  1986年   1篇
  1983年   1篇
  1981年   1篇
  1979年   1篇
  1976年   1篇
排序方式: 共有270条查询结果,搜索用时 15 毫秒
131.
Hydrops fetalis and fetal death caused by fetal parovirus B19 infection have been reported to be associated with elevated maternal serum alpha-fetoprotein (AFP), based on a total of six cases. It has been suggested that the absence of AFP elevation may be reassuring. Maternal serum levels of the Down syndrome screening markers unconjugated oestriol and human chorionic gonadotropin in cases of fetal parvovirus infection have not been previously reported. We report four cases of hydrops fetalis and fetal death caused by fetal parvovirus infection, each with unremarkable second-trimester levels of AFP, unconjugated oestriol, and human chorionic gonadotropin.  相似文献   
132.
A 37-year-old gravida was referred for CVS because of advanced maternal age. A trisomy 21 was present in all cells after short-term incubation (direct processing (DP)) and long-term culture. According to our policy, a retap was offered for confirmation of the result during the legally required 3-day waiting period between communication of the result and termination of pregnancy. Unexpectedly all cells after DP showed a normal male chromosome complement. Further investigations revealed mosaicism in trophoblast tissue and a normal karyotype in amniotic fluid cells and fetal blood (50 mitoses each). The parents elected to continue the pregnancy after extensive ultrasound examinations did not show suspicious findings. After the birth of a healthy child, cell cultures from ten different placental sites confirmed mosaicism. Four out of 100 mitoses from a lymphocyte culture showed an additional chromosome 21. The child had no dysmorphic features and the development was normal at the age of 10 weeks. This case demonstrates the restricted validity of prenatal cytogenetic analysis in the presence of true fetal mosaicism. It also stresses the benefit of our policy to offer a retap in cases with abnormal cytogenetic results prior to termination of pregnancy which is considered unnecessary by many cytogeneticists.  相似文献   
133.
134.
Abstract

The effect of two sublethal fenitrothion concentrations (0.02 and 0.04 mg/L) on the energy metabolism of the european eel Anguilla anguilla and its recovery from intoxication was investigated. Analysis of various parameters such as glycogen, proteins and total lipids was made on liver and muscle eel tissues after 2, 8, 12, 24, 32, 48, 56, 72 and 96 hr of fenitrothion (0,0‐dimethyl 0–3‐methyl‐4‐nitrophenyl phosphorothioate) exposure. Subsequently, the fish were allowed recovery periods of 8, 12, 24, 48, 72, 96, 144 and 192 hr in clean water, and the same parameters were again evaluated. The results obtained during the exposure to the pesticide as well as during the recovery phase were used to calculate the caloric content in both tissues of A. anguilla. A reduction in energy reserves in the selected tissues was observed after exposure to both fenitrothion concentrations and the caloric content in those animals was lower than in the controls. Most of the metabolic disorders did not persist after allowing recovery in clean water during a week.  相似文献   
135.
136.
用溶剂萃取-白土精制法对4种废机油进行了再生研究,萃取过程剂油质量比为3∶1,萃取温度为60℃,减压蒸馏回收溶剂。白土精制过程中白土质量为油质量的10%,精制温度为185℃。精制后4种废机油的密度、凝点、黏度、闪点、酸值等都有不同程度的改善。  相似文献   
137.
138.
Paralytic ileus of the small bowel was diagnosed in a fetus at 32 weeks' gestation after referral because of polyhydramnios. The mother had taken clonazepam, a benzodiazepine, and carbamazepine during the entire pregnancy for epilepsy. All known causes for the ileus were ruled out and at 20 months the boy has developed normally. We conclude that maternal anticonvulsant drug intake was very likely the cause of the paralytic ileus. This side-effect is known in experimental and clinical pharmacology but has not yet been described in human fetuses.  相似文献   
139.
The appearance of excessive lipids in amniotic fluid during Caesarean section raised the suspicion of a hyperlipidaemic fetus. The amniotic fluid had elevated cholesterol (53 mg/dl) and triglycerides (81 mg/dl). At the age of 2 months, the infant was hyperlipidaemic (cholesterol of 161 mg/dl and triglycerides of 84 mg/dl). The case suggests the possibility of prenatal diagnosis of hyperlipidaemia, a major risk factor for atherosclerosis.  相似文献   
140.
The diagnosis of Dandy-Walker malformation was made on the ultrasonographic evaluation of a 33-week male fetus. Pedigree analysis revealed a family history of isolated Dandy-Walker malformation in three other males, suggesting an X-linked recessive inheritance pattern.  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