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   13458篇
  免费   125篇
  国内免费   109篇
安全科学   367篇
废物处理   591篇
环保管理   2112篇
综合类   2592篇
基础理论   2983篇
环境理论   6篇
污染及防治   3511篇
评价与监测   830篇
社会与环境   627篇
灾害及防治   73篇
  2022年   113篇
  2021年   115篇
  2020年   78篇
  2019年   91篇
  2018年   181篇
  2017年   163篇
  2016年   268篇
  2015年   209篇
  2014年   281篇
  2013年   1096篇
  2012年   373篇
  2011年   515篇
  2010年   423篇
  2009年   453篇
  2008年   519篇
  2007年   584篇
  2006年   533篇
  2005年   440篇
  2004年   427篇
  2003年   458篇
  2002年   412篇
  2001年   449篇
  2000年   341篇
  1999年   230篇
  1998年   150篇
  1997年   146篇
  1996年   138篇
  1995年   180篇
  1994年   172篇
  1993年   145篇
  1992年   154篇
  1991年   171篇
  1990年   144篇
  1989年   148篇
  1988年   157篇
  1987年   132篇
  1986年   104篇
  1985年   122篇
  1984年   159篇
  1983年   156篇
  1982年   156篇
  1981年   133篇
  1980年   119篇
  1979年   149篇
  1978年   113篇
  1977年   105篇
  1976年   97篇
  1975年   93篇
  1974年   110篇
  1973年   77篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
132.
Biology as an autonomous science   总被引:1,自引:0,他引:1  
  相似文献   
133.
134.
135.
136.
Early arnniocentesis between 11 and 14 weeks' gestation was offered to 110 women at risk of a chromosomally abnormal fetus due to maternal age. Four were found to be unsuitable for the procedure, and 106 early amniocenteses were performed. In 102 cases, clear amniotic fluid was obtained with a single tap. There were two dry taps and two bloodstained tapis; sampling was repeated in three of these cases before 15 weeks. In the fourth case, placental biopsy was performed at 16 weeks. Thus, we were able to obtain a satisfactory sample in all but three cases(2.8 percent). Karyotyping of cells harvested from the early amniotic fluid samples was successful in all the 105 cases. Cell culture from the initial samples revealed a normal karyotype in 99 cases, two balanced translocations, two tetraploid karyotypes, and two cases of pseudomosaicism. Of the 105 pregnancies successfully sampled, there have been two losses to date (1–8 per cent). Two further patients presented with premature rupture of membranes, both pregnancies having successful outcomes. Sixty-two babies have delivered to date, with four congenital anomalies. There were no respiratory problems. Twenty-nine pregnancies are continuing without known complications, and details are not yet available on the remaining 12. The results indicate that early arnniocentesis may replace the traditional test at 15–17 weeks.  相似文献   
137.
The prenatal diagnosis by ultrasound of an unusual case of supernumerary head is reported. The problems of differential diagnosis, the pathological findings after voluntary interruption of the pregnancy, and the problems of obstetric management are presented.  相似文献   
138.
Six cases of cystic hygromas detected during second trimester ultrasound examination are reported: 4 fetuses (67 per cent) had a 45, X karyotype, 1 fetus had trisomy 18, 1 fetus had a normal karyotype (46,XX) and at autopsy multiple anomalies were observed. In the latter case the family history suggested an autosomal recessive pattern of inheritance. In order to reach a definite diagnosis and give proper genetic counselling when a fetus is found to have cystic hygroma, a fetal karyotype as well as a family and reproductive history should be obtained.  相似文献   
139.
In 40 pregnancies at risk for the Hurler syndrome 13 affected fetuses were detected by the demonstration of an α-L -iduronidase deficiency and an increased level of 35S-sulphate incorporation. The diagnoses were confirmed by the analysis of fetal tissues and/or cultured fetal skin fibroblasts. Microassays for α-L -iduronidase, using phenyl α-L -iduronide and more recently 4–methyl-umbelliferyl α-L -iduronide, enabled a reliable diagnosis to be made within 15 to 18 days after amniocentesis. 35S-sulphate incorporation has been a valuable adjunct in cases with a low (heterozygote) enzyme activity.  相似文献   
140.
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