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   94105篇
  免费   1229篇
  国内免费   1107篇
安全科学   3854篇
废物处理   3514篇
环保管理   14426篇
综合类   21129篇
基础理论   26782篇
环境理论   72篇
污染及防治   16228篇
评价与监测   5696篇
社会与环境   4150篇
灾害及防治   590篇
  2022年   824篇
  2021年   831篇
  2020年   656篇
  2019年   865篇
  2018年   1233篇
  2017年   1264篇
  2016年   2208篇
  2015年   1838篇
  2014年   2567篇
  2013年   9213篇
  2012年   2380篇
  2011年   2833篇
  2010年   3356篇
  2009年   3505篇
  2008年   2440篇
  2007年   2242篇
  2006年   2553篇
  2005年   2506篇
  2004年   2780篇
  2003年   2621篇
  2002年   2173篇
  2001年   2451篇
  2000年   2042篇
  1999年   1554篇
  1998年   1378篇
  1997年   1373篇
  1996年   1506篇
  1995年   1606篇
  1994年   1487篇
  1993年   1338篇
  1992年   1336篇
  1991年   1311篇
  1990年   1254篇
  1989年   1220篇
  1988年   1065篇
  1987年   1001篇
  1986年   998篇
  1985年   1067篇
  1984年   1163篇
  1983年   1170篇
  1982年   1178篇
  1981年   1101篇
  1980年   939篇
  1979年   935篇
  1978年   830篇
  1977年   722篇
  1976年   640篇
  1975年   610篇
  1973年   652篇
  1972年   648篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
751.
The sinusoidal fetal heart rate pattern has been described in association with severe fetal anaemia, with fetal hypoxaemia, and with the administration of parenteral narcotics. Here, we report a case of decreased fetal movement in which a sinusoidal tracing was recorded. The sonographic diagnosis of a massive fetal intracranial haemorrhage was made. A non-interventive approach was taken and the fetus died soon after in utero. We review 28 previous cases in which the prenatal sonographic diagnosis of fetal intracranial haemorrhage was made, including the underlying maternal and fetal factors and neonatal outcomes. We propose that the sinusoidal tracing in this case was due to the intracranial bleed and suggest that fetal intracranial haemorrhage be considered in the sonographic evaluation of the fetus with a sinusoidal pattern.  相似文献   
752.
A 17-year-old woman was referred for amniocentesis due to a low maternal serum alpha-fetoprotein (AFP) concentration in a voluntary screening test. The fetal karyotype was 48,XXYY, and the pregnancy was terminated. Autopsy of the fetus disclosed agenesis of the corpus callosum and unusual facial features.  相似文献   
753.
754.
755.
756.
Fetal aspartylglucosaminuria (AGU) was studied during the first trimester of pregnancy in six at-risk pregnancies using chorionic villus samples. The activity of aspartylglucosaminidase (AGA) was high in five cases, indicating an unaffected fetus. This was confirmed through delivery of healthy newborns with a normal pattern of urinary oligosaccharides. Low enzyme activity in an uncultured biopsy specimen and in cultured amniotic fluid cells in one case demonstrated that the fetus was affected. The pregnancy was terminated and the prenatal diagnosis was confirmed by showing reduced AGA activity in cultured fibroblasts of the fetus.  相似文献   
757.
758.
We report herein a de novo unbalanced chromosome translocation in a fetus resulting from in vitro fertilization technology. Prenatal diagnostic analysis of an amniotic fluid revealed a 46,XX,4p+ karyotype. The origin of the extra material on the short arm of chromosome 4 could not be identified by a variety of banding techniques. However, examination of fetal parts did reveal some dysmorphic features.  相似文献   
759.
In vitro characteristics of human fetal cells have been investigated after chorionic villus sampling at the first trimester and amniocentesis at the second trimester of pregnancy. Light microscopy revealed heterogeneous morphology of cell types in both the chorionic villus culture and the amniotic fluid cultures. Based on the experiments performed, chorionic villus cells are more sensitive to pronase, trypsin, and versene during subculture and have a higher DNA content per single cell and release more [125I]-Beta-human chorionic gonadotropin into culture medium than those found in amniotic fluid cells. The practical applications of this study are discussed.  相似文献   
760.
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