全文获取类型
收费全文 | 800篇 |
免费 | 8篇 |
国内免费 | 16篇 |
专业分类
安全科学 | 22篇 |
废物处理 | 34篇 |
环保管理 | 96篇 |
综合类 | 232篇 |
基础理论 | 149篇 |
环境理论 | 2篇 |
污染及防治 | 204篇 |
评价与监测 | 40篇 |
社会与环境 | 31篇 |
灾害及防治 | 14篇 |
出版年
2023年 | 9篇 |
2022年 | 15篇 |
2021年 | 23篇 |
2020年 | 19篇 |
2019年 | 11篇 |
2018年 | 22篇 |
2017年 | 28篇 |
2016年 | 44篇 |
2015年 | 25篇 |
2014年 | 32篇 |
2013年 | 62篇 |
2012年 | 35篇 |
2011年 | 47篇 |
2010年 | 29篇 |
2009年 | 43篇 |
2008年 | 36篇 |
2007年 | 33篇 |
2006年 | 18篇 |
2005年 | 16篇 |
2004年 | 17篇 |
2003年 | 20篇 |
2002年 | 28篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 12篇 |
1998年 | 8篇 |
1996年 | 10篇 |
1995年 | 4篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1987年 | 4篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1974年 | 3篇 |
1973年 | 8篇 |
1969年 | 3篇 |
1965年 | 5篇 |
1964年 | 3篇 |
1963年 | 5篇 |
1962年 | 3篇 |
1961年 | 6篇 |
1960年 | 4篇 |
1959年 | 3篇 |
1958年 | 5篇 |
1957年 | 6篇 |
1954年 | 5篇 |
排序方式: 共有824条查询结果,搜索用时 15 毫秒
11.
12.
13.
Pregnancies with fetal trisomy 21 have been associated with low amniotic fluid alpha-fetoprotein levels (AFAFP). This observation led to the suggestion that low AFAFP levels be used as a criterion for completion of a chromosomal analysis in patients who are not otherwise at increased risk for a fetal chromosome abnormality and in whom karyotyping might not have been completed for economic reasons. In order to assess the usefulness of such criteria, we reviewed the AFAFP levels of 90 cases of fetal trisomy 21, 23 cases of trisomy 18, and 10 cases of trisomy 13. These were compared with 2400 control samples with normal chromosome constitution. AFAFP levels were generally lower in pregnancies with trisomy 21, showing a median value of 0·72 MoM. However, 40 per cent of the trisomy 21 samples had AFAFP values greater than 0·8 MoM and 20 per cent were over 1·0 MoM. These data imply that over 50 per cent of Down syndrome cases might have been missed using a cut-off level of 0·70 MoM for completion of chromosome analysis. Using a higher cut-off level will leave only a small percentage of samples unkaryotyped. The distribution of AFP levels in trisomy 13 and 18 is no different from controls; we therefore believe that fetal karyotyping should be completed in every amniotic fluid sample obtained. 相似文献
14.
15.
16.
17.
18.
19.
We report on new chemical and lead isotopic results and interpretations of archaic Greek silver coins from the Asyut hoard which was buried around 475 B.C. Aeginetan coins were of central interest in this study. Possible ancient silver mines were explored in the Aegean region in the course of several geologic expeditions, and chemically and isotopically investigated. Some of the silver sources in Greece were traced by combination of the analytical methods and questions of provenance were solved. In addition, processes of silver smelting and refining were studied. Results and implications of this work are summarized in the final section on Conclusions. 相似文献
20.