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   971篇
  免费   1篇
安全科学   18篇
废物处理   1篇
环保管理   84篇
综合类   779篇
基础理论   53篇
污染及防治   29篇
评价与监测   5篇
灾害及防治   3篇
  2022年   2篇
  2016年   3篇
  2015年   3篇
  2014年   2篇
  2013年   37篇
  2010年   5篇
  2009年   4篇
  2008年   5篇
  2007年   4篇
  2005年   3篇
  2004年   3篇
  2003年   12篇
  2002年   8篇
  1998年   11篇
  1997年   4篇
  1995年   56篇
  1994年   50篇
  1993年   38篇
  1992年   32篇
  1991年   26篇
  1990年   32篇
  1989年   25篇
  1988年   34篇
  1987年   29篇
  1986年   21篇
  1985年   14篇
  1984年   12篇
  1983年   14篇
  1982年   10篇
  1981年   4篇
  1979年   5篇
  1976年   6篇
  1975年   9篇
  1974年   4篇
  1973年   10篇
  1972年   2篇
  1971年   4篇
  1963年   3篇
  1962年   2篇
  1961年   3篇
  1959年   2篇
  1940年   2篇
  1920年   2篇
  1919年   47篇
  1918年   44篇
  1917年   36篇
  1916年   53篇
  1915年   37篇
  1914年   71篇
  1913年   106篇
排序方式: 共有972条查询结果,搜索用时 15 毫秒
811.
Blood collected from 62 fetuses aged 20–38 weeks of gestation was studied. The values of ten lipid parameters were determined: cholesterol (TC), triglycerides (TGs), apolipoprotein Al (apo A1), apolipoprotein B (apo B), apolipoprotein E (apo E), total apolipoprotein CIII (apo CIII), apolipoprotein CIII present in particles containing apo B (apo CIII LpB) or not (apo CIII Lp non-B), lipoparticles A1 (LpA1), and lipoprotein a (Lp(a)). The results show that, except for apo E, all the studied parameters were present in lower concentrations than in adults and newborns, and that Lp(a) is not detectable at that stage in life.  相似文献   
812.
The objective of this study was to assess the effects of two brief training interventions to improve obstetricians' and midwives' explanations to patients of a routine prenatal screening test. Health professionals were randomly allocated to one of two intervention groups or a control group. Information-giving about the test and communication skills were assessed at baseline, post-training and 3-month follow-up from audiotaped consultations. Both intervention groups received a 1-h training session involving small group discussions focused around a video. In addition, one group received individual feedback on their baseline and post-training consultations. Twenty-six midwives and nine obstetricians completed the study according to the protocol. Changes between baseline and post-training, and between baseline and follow-up, were computed. Information-giving and communication skills improved significantly in subjects receiving training and feedback on their performance, with the greatest improvements occurring before feedback was given. Those receiving training without feedback significantly improved their communication skills and showed some improvement in information-giving. These results show that modest improvements in communication can be made with relatively brief training. Greater and more sustained improvements may be found if all staff were trained, and trained on a regular basis.  相似文献   
813.
814.
Congenital erythropoietic porphyria (CEP) or Günther's disease is the rarest form of the porphyrias. The disease is usually diagnosed at birth or during early infancy, but rarely in utero. We describe here the first two cases of very early prenatal expression of CEP with cystic hygroma diagnosed at 14 weeks in the first fetus and at 19 weeks in the second. Both fetuses presented with severe nonimmune hydrops fetalis as early as 19 and 22 weeks, associated with intrauterine growth retardation, hyperechogenic kidneys and bones. Amniotic fluid was dark brown and uro- and coproporphyrin I was dramatically increased. Molecular screening of the CEP gene detected heterozygous C73R mutation in both fetuses, the other parental mutation being as yet unknown. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
815.
816.
817.
Maternal serum human chorionic gonadotropin (hCG) and the free alpha-hCG subunit were evaluated in 249 women from 9 to 11 weeks gestation who subsequently underwent chorionic villus sampling for determination of fetal karyotype and in 20 women of 18 or more weeks gestation who were ascertained to have an aneuploid fetus by genetic amniocentesis. Seven of the first-trimester pregnancies were determined to be aneuploid and six had hCG levels in the normal range (one triploid pregnancy had elevated hCG levels) whereas 12 of the 20 secondtrimester cases had abnormal hCG levels and an additional three had elevated levels of alpha-hCG. This study confirms the previous report of abnormal maternal serum hCG levels in women with an aneuploid fetus at ≥ 18 weeks gestation and demonstrates that hCG evaluation is not useful at 9–11 weeks gestation for selecting pregnancies at risk for fetal aneuploidy.  相似文献   
818.
Fourteen (2.5 per cent) of 568 chromosome preparations after CVS showed discrepancies between the placental and fetal karyotype, mainly due to placental mosaicism. The presence of a second cell line within the placenta was confirmed in all but one case, in which cytogenetic reinvestigations were carried out. Our clinical data indicate that severe developmental retardation in the newborn is not to be expected if only the placenta carries the chromosomally abnormal cell line.  相似文献   
819.
An extra small chromosome detected in amniotic fluid was identified as the product of a translocation [46,XX,t(9;15)(p24;q11.2)]. This case is unusual in that individuals with the unbalanced karyotype resulting from a 3:1 disjunction are phenotypically normal.  相似文献   
820.
跨世纪安全科学技术人才培养模式的探讨   总被引:1,自引:2,他引:1  
针对二十一世纪对安全科技人才的素质需求及我国现行安全科技人才培养模式的状况,从安全工程专业教学方法和课程体系两方面对我国跨世纪安全科技人才培养模式进行探讨  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