全文获取类型
收费全文 | 3407篇 |
免费 | 339篇 |
国内免费 | 1469篇 |
专业分类
安全科学 | 310篇 |
废物处理 | 162篇 |
环保管理 | 269篇 |
综合类 | 2924篇 |
基础理论 | 809篇 |
污染及防治 | 401篇 |
评价与监测 | 275篇 |
社会与环境 | 42篇 |
灾害及防治 | 23篇 |
出版年
2024年 | 14篇 |
2023年 | 65篇 |
2022年 | 127篇 |
2021年 | 134篇 |
2020年 | 153篇 |
2019年 | 132篇 |
2018年 | 148篇 |
2017年 | 183篇 |
2016年 | 206篇 |
2015年 | 244篇 |
2014年 | 277篇 |
2013年 | 367篇 |
2012年 | 364篇 |
2011年 | 318篇 |
2010年 | 241篇 |
2009年 | 273篇 |
2008年 | 244篇 |
2007年 | 248篇 |
2006年 | 218篇 |
2005年 | 154篇 |
2004年 | 156篇 |
2003年 | 156篇 |
2002年 | 107篇 |
2001年 | 97篇 |
2000年 | 78篇 |
1999年 | 80篇 |
1998年 | 65篇 |
1997年 | 61篇 |
1996年 | 44篇 |
1995年 | 41篇 |
1994年 | 38篇 |
1993年 | 20篇 |
1992年 | 23篇 |
1991年 | 19篇 |
1990年 | 11篇 |
1989年 | 13篇 |
1988年 | 17篇 |
1987年 | 10篇 |
1986年 | 11篇 |
1985年 | 4篇 |
1984年 | 16篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 10篇 |
1974年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有5215条查询结果,搜索用时 15 毫秒
71.
用植物清除土壤中的重金属 总被引:11,自引:0,他引:11
介绍了生物修复技术去除土壤中的重金属及对植物的要求.植物能去除土壤中的有毒金属,将金属富集在生物体内,或将金属变成挥发性气体. 相似文献
72.
Mao Meizhou Liu Zihui Dong Huiru Liu Jingyi Kathe K. Bertines Minoru Koide Edward D. Goldberg 《环境科学学报(英文版)》1991,3(1):109-116
The fluxes of heavy metals and magnetite, a fly-ash component, from coal burning, to sediments of the Kunming Lake in Beijing have increased measurably over the last fifty years. Ages were introduced to the sediment strata through Pb-210 geochronologies. Even with a doubling of coal usage by the year 2000, the anthropogenic metal fluxes will still be less than those recorded in metropolitan Tokyo and U.S. lakes. 相似文献
73.
Accurate diagnosis of mosaicism in amniotic fluid cell cultures represents a major problem. If insufficient cells are analysed, true fetal mosaicism may go undetected. False-positive diagnosis is also possible since a second cell line may arise in vitro and not reflect the true fetal genetic constitution. These difficulties apply to both flask and in situ culture techniques, to varying degrees. The relative accuracy of flask versus in situ culture techniques in excluding mosaicism was determined by statistical analysis of experimental data from ten pairs of mixed male-female amniotic fluid specimens. The data support the idea that the majority of in situ colonies are independent of one another. The following conclusions are drawn: (1) analysis of a single metaphase from a number of different colonies enhances the confidence for excluding mosaicism; (2) analysis of more than one cell per colony offers little advantage; (3) exclusion of a given level of mosaicism requires analysis of fewer metaphases using the in situ method; (4) the confidence for excluding mosaicism is high with both in situ and flask techniques, using the provided guidelines; and (5) it is shown that the two-stage approach used by many laboratories is currently the most efficient way to exclude mosaicism. 相似文献
74.
We describe our experience of prenatal diagnosis of non-ketotic hyperglycinaemia in four at-risk pregnancies using the glycine/serine ratio in amniotic fluid obtained between 18 and 20 weeks of gestation. All glycine levels were in the normal range. Serine levels were normal in two patients and borderline in the others. Glycine/serine ratios were normal in two patients, moderately increased in one patient ( + 3 SD), and highly increased in one patient ( + 8 SD). All the children were perfectly normal at birth. Because of this false-positive prediction and the false-negative prediction recently reported, we suggest that this unreliable method should not be used. 相似文献
75.
研究表明,用多硫化物处理高浓度含氰电镀废水的同时,亦可有效地去除废水中的重金属,其方法操作简便。本文对实际应用中所需的工艺条件、反应产物硫氰化物的去向、残余多硫化物的处理、多硫化物的合成、反应热效应等进行了研究,取得了满意的结果。 相似文献
76.
We studied the validity of mid-trimester amniotic fluid testosterone and FSH in the diagnosis of fetal sex in abnormal fetuses and in twins. It was found that the testosterone/FSH ratio, but not the level of the individual hormones, was an excellent criterion for fetal sex diagnosis. In a control group of 32 female and 34 male fetuses, the testosterone/FSH ratio was diagnostic. In two cases the values were indeterminate and fetal sex could not be predicted, but there were no false diagnoses. The abnormalities of the fetuses were diagnosed by karyotype analyses or raised levels of α-fetoprotein. It was found that neither autosomal trisomies nor X-chromosome aneuploidy or neural tube defect interfered with the diagnostic value of the hormonal approach. The twin study included 14 pairs, three of whom were discordant for sex. In all twins the fetal sex diagnosis was appropriate. In co-twins of the same sex the hormone levels were very close to each other. 相似文献
77.
We report relatively high citrulline concentration in amniotic fluid of a citrullinemic fetus suggesting that prenatal detection of this condition could be done on this basis in conjunction with a direct or an indirect determination of argininosuccinate synthetase activity in amniotic fluid cells. 相似文献
78.
David J. H. Brock 《黑龙江环境通报》1981,1(1):11-16
An analysis is made of alphafetoprotein (AFP) concentrations in 3630 amniotic fluids submitted for prospective prenatal diagnoses over a 7-year period. There were 89 cases of anencephaly, 74 of open spina bifida and 3467 with normal singleton outcomes. The AFP data were expressed in both standard deviations above the mean and multiples of the normal median for individual weeks of gestation. False positive and false negative rates were comparable in the two systems at selected cut-offs. It is concluded that either system may be used in setting action limits for the primary distinction of unaffected pregnancies from those in which an open neural tube defect is present. 相似文献
79.
80.