全文获取类型
收费全文 | 19410篇 |
免费 | 181篇 |
国内免费 | 136篇 |
专业分类
安全科学 | 450篇 |
废物处理 | 811篇 |
环保管理 | 1984篇 |
综合类 | 3928篇 |
基础理论 | 5120篇 |
环境理论 | 12篇 |
污染及防治 | 4976篇 |
评价与监测 | 1238篇 |
社会与环境 | 1109篇 |
灾害及防治 | 99篇 |
出版年
2022年 | 156篇 |
2021年 | 128篇 |
2020年 | 118篇 |
2019年 | 145篇 |
2018年 | 273篇 |
2017年 | 321篇 |
2016年 | 420篇 |
2015年 | 353篇 |
2014年 | 549篇 |
2013年 | 1382篇 |
2012年 | 602篇 |
2011年 | 869篇 |
2010年 | 731篇 |
2009年 | 698篇 |
2008年 | 860篇 |
2007年 | 870篇 |
2006年 | 734篇 |
2005年 | 630篇 |
2004年 | 624篇 |
2003年 | 598篇 |
2002年 | 616篇 |
2001年 | 721篇 |
2000年 | 539篇 |
1999年 | 297篇 |
1998年 | 214篇 |
1997年 | 238篇 |
1996年 | 251篇 |
1995年 | 278篇 |
1994年 | 273篇 |
1993年 | 209篇 |
1992年 | 235篇 |
1991年 | 215篇 |
1990年 | 235篇 |
1989年 | 213篇 |
1988年 | 169篇 |
1987年 | 180篇 |
1986年 | 172篇 |
1985年 | 178篇 |
1984年 | 169篇 |
1983年 | 159篇 |
1982年 | 147篇 |
1981年 | 141篇 |
1980年 | 132篇 |
1979年 | 138篇 |
1978年 | 123篇 |
1977年 | 133篇 |
1976年 | 107篇 |
1975年 | 106篇 |
1973年 | 116篇 |
1972年 | 107篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
381.
382.
383.
The most common mutation in alpha-1-antitrypsin deficiency, conversion of a G to an A at base 9989 (PI-Z), was detected with the chemical cleavage of mismatch method, demonstrating the power of the method for prenatal diagnosis. Exon V of the gene was amplified using the polymerase chain reaction and heteroduplexes were formed to test for the presence of the mutation. The predicted C mismatch was readily detectable with hydroxylamine, and by making the probe from the chorionic villus sample it was possible to determine that the fetus was heterozygous, not homozygous, for the mutation. 相似文献
384.
The nature of the cosmic redshift is one of the most fundamental questions in modern science. Hubble's discovery of the apparent Expansion of the Universe is derived from observations on a small number of galaxies at very low redshifts. Today, quasar redshifts have a range more than 1000 times greater than those in Hubble's sample, and represent more than 100 times as many objects. A recent comprehensive compilation of published measurements provides the basis for a study indicating that quasar observations are not in good agreement with the original predictions of the Expanding Universe theory, but are well fit by the predictions of an alternative theory having fewer adjustable parameters. 相似文献
385.
386.
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
387.
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
388.
The index patient is a female fetus in which prenatal diagnosis of 8p trisomy was established after amniocentesis at 16 weeks of gestation. This fetus was the unbalanced product of a maternal translocation of 5q/8p (karyotype: 46,XX,t(5;8)(q35;pl 1). Internal malformations include an anomalous lobature of the right lung, a little and high atrio-ventricular communication, and an anomaly in the number and shape of the aortic semilunar valves. The possible relationship between the phenotype and the chromosomal abnormality is briefly discussed. 相似文献
389.
390.