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   27890篇
  免费   274篇
  国内免费   272篇
安全科学   765篇
废物处理   1329篇
环保管理   3422篇
综合类   3601篇
基础理论   7371篇
环境理论   6篇
污染及防治   7697篇
评价与监测   2163篇
社会与环境   1921篇
灾害及防治   161篇
  2022年   280篇
  2021年   274篇
  2020年   191篇
  2019年   232篇
  2018年   440篇
  2017年   433篇
  2016年   697篇
  2015年   482篇
  2014年   748篇
  2013年   2330篇
  2012年   900篇
  2011年   1201篇
  2010年   1062篇
  2009年   1080篇
  2008年   1252篇
  2007年   1337篇
  2006年   1188篇
  2005年   997篇
  2004年   961篇
  2003年   982篇
  2002年   908篇
  2001年   1262篇
  2000年   879篇
  1999年   539篇
  1998年   376篇
  1997年   350篇
  1996年   391篇
  1995年   406篇
  1994年   350篇
  1993年   312篇
  1992年   330篇
  1991年   302篇
  1990年   319篇
  1989年   318篇
  1988年   273篇
  1987年   231篇
  1986年   179篇
  1985年   212篇
  1984年   240篇
  1983年   231篇
  1982年   259篇
  1981年   198篇
  1980年   173篇
  1979年   206篇
  1978年   151篇
  1977年   154篇
  1976年   139篇
  1975年   126篇
  1974年   128篇
  1973年   125篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
381.
382.
In a case of hydrops fetalis, serological examination showed a recent maternal human parvovirus B19 infection. Amniocentesis revealed a unique unbalanced translocation between chromosomes 3 and 11 of the fetus. The mother proved to have a balanced reciprocal translocation between chromosomes 3 and 11. A grossly macerated hydropic male fetus was delivered with a flat nose and low implanted deformed ears. Histopathological examination revealed nuclear inclusion bodies in fetal erythroid cells, confirming human parvovirus B19 infection. Parvovirus B19 DNA was demonstrated by in situ hybridization in the nuclei of heart muscle cells. Our finding of two different disorders in one case illustrates the importance of a complete evaluation of every case of hydrops fetalis, especially concerning counselling on the outcome of future pregnancies. The human parvovirus B19 infection will not recur due to the acquired immunity of the mother, whereas the balanced reciprocal translocation will endanger future pregnancies.  相似文献   
383.
384.
385.
Reverse phase HPLC of radioactive globin chains has been compared to classical carboxy methyl cellulose chromatography for the prenatal diagnosis of β thalassaemia. The two methods correlated highly (r = 0.97 p < 0.0005) and provided an identical diagnosis for 40 fetal blood samples of fetuses homozygous or heterozygous for β thalassaemia. The HPLC procedure was much faster and required fewer biochemical steps (no globin preparation). It was at least as accurate and more sensitive than the classical chromatography. A single column can be used for 150 analyses and is always ready to be used. Last but not least it is much less expensive than CMC chromatography.  相似文献   
386.
387.
388.
The polymerase chain reaction (PCR) was used on material from a blighted ovum to confirm indirectly the carrier status of a woman with a family history of Becker muscular dystrophy. Conventional testing including creatine kinase levels, muscle biopsy, and EMG had been inconclusive, and on the basis of one elevated creatine kinase level, the woman had been designated a possible carrier. Ultrasound examination at 10 weeks of pregnancy indicated a blighted ovum, from which DNA was subsequently extracted and subjected to PCR testing for determination of sex and genotypic status with respect to the known familial deletion of the dystrophin gene. The blighted ovum was found to have a Y chromosome and also to be deleted for at least exon 6 of the dystrophin gene, indirectly indicating that the mother most likely carried the family mutation for Becker muscular dystrophy.  相似文献   
389.
390.
Although malignant transformation of fetal cervical teratoma is extremely rare, perinatal morbidity is high and usually related to the size of the tumour, which may compromise fetal swallowing and subsequently lead to upper airway obstruction. We present a case in which mid-trimester serial sonography demonstrated markedly rapid early growth of a lesion of this type between 17 and 19 weeks' gestation indicating the aggressive nature of this tumour, assisting parental decision to terminate the pregnancy. Histopathology confirmed grade 3 immaturity of the lesion.  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