全文获取类型
收费全文 | 95667篇 |
免费 | 1242篇 |
国内免费 | 1117篇 |
专业分类
安全科学 | 3899篇 |
废物处理 | 3564篇 |
环保管理 | 14634篇 |
综合类 | 21397篇 |
基础理论 | 27130篇 |
环境理论 | 78篇 |
污染及防治 | 16694篇 |
评价与监测 | 5789篇 |
社会与环境 | 4226篇 |
灾害及防治 | 615篇 |
出版年
2022年 | 827篇 |
2021年 | 847篇 |
2020年 | 664篇 |
2019年 | 878篇 |
2018年 | 1269篇 |
2017年 | 1294篇 |
2016年 | 2230篇 |
2015年 | 1868篇 |
2014年 | 2596篇 |
2013年 | 9294篇 |
2012年 | 2454篇 |
2011年 | 2946篇 |
2010年 | 3414篇 |
2009年 | 3587篇 |
2008年 | 2535篇 |
2007年 | 2370篇 |
2006年 | 2673篇 |
2005年 | 2588篇 |
2004年 | 2833篇 |
2003年 | 2676篇 |
2002年 | 2246篇 |
2001年 | 2476篇 |
2000年 | 2070篇 |
1999年 | 1575篇 |
1998年 | 1397篇 |
1997年 | 1394篇 |
1996年 | 1522篇 |
1995年 | 1631篇 |
1994年 | 1505篇 |
1993年 | 1351篇 |
1992年 | 1347篇 |
1991年 | 1315篇 |
1990年 | 1259篇 |
1989年 | 1224篇 |
1988年 | 1069篇 |
1987年 | 1002篇 |
1986年 | 1003篇 |
1985年 | 1071篇 |
1984年 | 1172篇 |
1983年 | 1178篇 |
1982年 | 1182篇 |
1981年 | 1108篇 |
1980年 | 944篇 |
1979年 | 944篇 |
1978年 | 836篇 |
1977年 | 726篇 |
1976年 | 641篇 |
1974年 | 612篇 |
1973年 | 655篇 |
1972年 | 651篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
581.
E.F. Brünig 《Agriculture, ecosystems & environment》1984,11(2):191
582.
583.
We report in detail two series of chorionic villus cultivation for prenatal chromosomal diagnosis. Chorionic villi were sampled from both first- and second-trimester pregnancies. One hundred cultures were treated with trypsin–EDTA for 2 h and collagenase overnight, (method A) and 100 were treated with trypsin–EDTA for 1 h and collagenase for 2 h (method B). Using short-term enzymatic digestion, the cultivation time was reduced from 14 days to 6 days. Sufficient amounts of metaphases of good quality were present in 93 per cent of primary cultures harvested in situ, whereas enough metaphases of sufficiently good quality were in most cases present only after subcultivation of the cultures using method A. The decrease in cultivation time obtained is probably due to a higher yield of viable cells in monocellular suspension, an increased attachment efficiency, and a more rapid attachment of single cells (within 24 h). 相似文献
584.
585.
Maya Thangavelu PhD Eugene Pergament Rafael Espinosa Iii Stefan K. Bohlander 《黑龙江环境通报》1994,14(7):583-588
We characterized by microdissection and fluorescence in situ hybridization (FISH) two marker chromosomes: (1) a de novo, acrocentric marker chromosome detected in 88 per cent of the amniotic fluid cells of one of two physically and developmentally normal twins; and (2) a metacentric marker chromosome present in a phenotypically normal female. Analysis of FISH probes developed from the marker chromosomes indicated that the marker chromosomes in cases 1 and 2 were del(14)(q11) and a derivative chromosome from a Robertsonian translocation, respectively. Microdissection in combination with FISH may prove to be a valuable technique in determining the chromosomal origin of de novo marker chromosomes and unbalanced structural rearrangements detected during prenatal diagnosis. 相似文献
586.
587.
588.
Manganese-oxidizing fungi and bacteria 总被引:1,自引:0,他引:1
The Science of Nature - 相似文献
589.
590.
Maternal age specific rates for all major chromosome aberrations have been determined in 52 965 pregnancies in mothers 35 years of age and over at the time of amniocentesis. Rates increase exponentially with advancing maternal age for trisomies 21, 18 and 13, and for the XXX and XXY syndromes, but in the autosomal trisomies this rise appears to be followed by a levelling off at the upper end of the age range. A significant inverse relationship with maternal age is found for 45,X cases. It is postulated that these various patterns are the result of the interaction of three principal factors: a maternal age effect acting particularly on first meiotic nondisjunction: a higher spontaneous abortion rate with advancing maternal age for aneuploid as compared to euploid conceptions; and an increased probability of spontaneous abortion before the time of amniocentesis for conceptions with more extensive chromosome imbalance. A stepwise logistic regression analysis of 13 299 pregnancies in which both parental ages are known shows that the father's age does not influence these maternal age specific rates, with the possible exception of the 47,XXY syndrome. 相似文献