全文获取类型
收费全文 | 2109篇 |
免费 | 9篇 |
国内免费 | 5篇 |
专业分类
安全科学 | 37篇 |
废物处理 | 47篇 |
环保管理 | 153篇 |
综合类 | 1437篇 |
基础理论 | 192篇 |
污染及防治 | 197篇 |
评价与监测 | 37篇 |
社会与环境 | 18篇 |
灾害及防治 | 5篇 |
出版年
2017年 | 15篇 |
2013年 | 76篇 |
2012年 | 34篇 |
2011年 | 30篇 |
2010年 | 28篇 |
2009年 | 32篇 |
2008年 | 28篇 |
2007年 | 30篇 |
2006年 | 29篇 |
2005年 | 35篇 |
2004年 | 40篇 |
2003年 | 45篇 |
2002年 | 34篇 |
1998年 | 22篇 |
1995年 | 70篇 |
1994年 | 61篇 |
1993年 | 48篇 |
1992年 | 38篇 |
1991年 | 31篇 |
1990年 | 39篇 |
1989年 | 34篇 |
1988年 | 36篇 |
1987年 | 31篇 |
1986年 | 25篇 |
1985年 | 19篇 |
1984年 | 17篇 |
1983年 | 18篇 |
1965年 | 15篇 |
1964年 | 14篇 |
1963年 | 28篇 |
1962年 | 19篇 |
1961年 | 16篇 |
1960年 | 23篇 |
1959年 | 26篇 |
1958年 | 15篇 |
1957年 | 17篇 |
1956年 | 15篇 |
1955年 | 27篇 |
1954年 | 33篇 |
1953年 | 19篇 |
1952年 | 14篇 |
1951年 | 24篇 |
1929年 | 13篇 |
1919年 | 48篇 |
1918年 | 45篇 |
1917年 | 39篇 |
1916年 | 54篇 |
1915年 | 37篇 |
1914年 | 71篇 |
1913年 | 106篇 |
排序方式: 共有2123条查询结果,搜索用时 15 毫秒
21.
The karyotype of cultured amniotic fluid cells obtained on the indication of advanced maternal age was shown to be a mosaic 45,X/46,X,r(?). The small size and banding pattern made it difficult to determine whether the ring was derived from and X or a Y chromosome, or even from an autosome. By using an X-centromeric probe and fluorescence in situ hybridization (FISH), we demonstrated the ring to have an X centromere. Thus, a more complete genetic counselling was possible. This confirms the usefulness of FISH in identifying and characterizing this and other chromosome rearrangements in prenatal diagnosis. 相似文献
22.
With growing awareness of the problems associated with prenatal cytogenetic diagnoses after CVS, attempts have been made to provide early amniocentesis as an alternative to CVS. Since 1990, at our clinic the gestational age limit for routine diagnostic amniocentesis has been successively lowered, first to 14 and then to 13 weeks of gestation. Thus, 811 prenatal diagnoses were performed after early amniocentesis at 13 weeks (n = 217) and at 14 weeks of gestation (n = 594). No problems were encountered. Culture failure was never observed in the early samples. Using the criteria ‘number of colonies’ and ‘culture duration until harvest’, early samples taken at 14 weeks did not differ significantly from the controls after standard amniocentesis performed at 15 and 16 weeks, respectively, whereas a minority of samples taken at 13 weeks experienced some delay in culturing. However, in each group at least 85 per cent of samples led to a diagnosis fulfilling our standard criteria of a safe diagnosis (at least 20 metaphases of at least five colonies from at least one primary culture after trypsinization) within 15 days. Some differences between the different groups can be recognized: culture duration of less than 11 days tends to be increasing after standard amniocentesis, whereas long culture duration (more than 20 days) is more often associated with early amniocentesis. However, this trend is only minimal and did not result in an increased risk of missing a diagnosis. 相似文献
23.
Sylvie Gagnon William Fraser Dr Bertrand Fouquette Adrien Bastide Marc Bureau Jean-Yves Fontaine Céline Huot 《黑龙江环境通报》1992,12(1):9-18
During a 7-year period, 117 fetal karyotypes were available from 131 genetic amniocenteses. These procedures were performed between 14 and 37 weeks' gestation for the following abnormal ultrasound findings: (1) intrauterine growth retardation (IUGR)—61 cases; (2) fetal malformation—71 cases; and (3) amniotic fluid volume (AFV) abnormality—60 cases. Chromosomal abnormalities were identified in 19 cases (16.2 per cent). Aneuploidy was 2.5 times as frequent in the presence of malformations than in their absence. No correlation was demonstrated between specific fetal malformations and specific chromosomal abnormalities. Aneuploidy was also twice as frequent in the presence of symmetrical IUGR than in its absence. No chromosomal abnormalities were found among eight cases of asymmetrical IUGR. Four cases of aneuploidy presented with isolated IUGR, three of these involving the X chromosome. The frequency of aneuploidy was the same with or without abnormalities of AFV (14.3 versus 16.4 per cent). No chromosomal abnormality was found associated with isolated AFV abnormalities. 相似文献
24.
25.
26.
27.
28.
29.
30.