全文获取类型
收费全文 | 43281篇 |
免费 | 773篇 |
国内免费 | 4704篇 |
专业分类
安全科学 | 1646篇 |
废物处理 | 2040篇 |
环保管理 | 4990篇 |
综合类 | 12376篇 |
基础理论 | 9809篇 |
环境理论 | 16篇 |
污染及防治 | 12461篇 |
评价与监测 | 2533篇 |
社会与环境 | 2143篇 |
灾害及防治 | 744篇 |
出版年
2023年 | 325篇 |
2022年 | 820篇 |
2021年 | 747篇 |
2020年 | 520篇 |
2019年 | 588篇 |
2018年 | 888篇 |
2017年 | 973篇 |
2016年 | 1189篇 |
2015年 | 1169篇 |
2014年 | 1687篇 |
2013年 | 3793篇 |
2012年 | 1908篇 |
2011年 | 2380篇 |
2010年 | 1881篇 |
2009年 | 1938篇 |
2008年 | 2112篇 |
2007年 | 2021篇 |
2006年 | 1846篇 |
2005年 | 1439篇 |
2004年 | 1330篇 |
2003年 | 1424篇 |
2002年 | 1299篇 |
2001年 | 1539篇 |
2000年 | 1200篇 |
1999年 | 957篇 |
1998年 | 726篇 |
1997年 | 684篇 |
1996年 | 731篇 |
1995年 | 677篇 |
1994年 | 588篇 |
1993年 | 534篇 |
1992年 | 501篇 |
1991年 | 457篇 |
1990年 | 448篇 |
1989年 | 423篇 |
1988年 | 382篇 |
1987年 | 308篇 |
1986年 | 278篇 |
1985年 | 298篇 |
1984年 | 308篇 |
1983年 | 302篇 |
1982年 | 343篇 |
1981年 | 279篇 |
1980年 | 251篇 |
1979年 | 274篇 |
1978年 | 246篇 |
1977年 | 214篇 |
1976年 | 213篇 |
1974年 | 212篇 |
1973年 | 191篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
721.
722.
723.
Dedicated to Professor Dr. Tuneo Yamada on the occasion of his 80th birthday. 相似文献
724.
We describe a patient with a significantly elevated serum alphafetoprotein (AFP) concentration at 17 weeks of gestation, who showed only a marginally increased amniotic fluid AFP and lacked the second rapidly migrating band of acetylcholinesterase electrophoresis. Ultrasound examination revealed an encephalocele and ventriculomegaly. Autopsy showed that the encephalocele was not covered by skin. 相似文献
725.
云南热海热田中的碱金属元素 总被引:2,自引:0,他引:2
1982至1983年在云南腾冲一已知水热区及其毗邻约 60km2 范围内采集了131个土壤样品。样品分析结果表明锂和铷的异常能圈定两个已知水热区,且与若干已知热田地球化学指示元素的异常相当一致,从而进一步肯定了这一地区的开发前景。与此同时,对区内水样中的钠钾含量也进行了测定并做出解译。锂铷和已知地球化学指标之间的相关分析表明它们之间确存有某种内在联系,同时可看出盐湖与古地热系统之间的一些联系。最后得出结论:土壤中的锂铷可作为圈定热田的地球化学指标;地热系统不仅能作为能源资源而且也应视作矿产资源。 相似文献
726.
727.
In vitro characteristics of human fetal cells have been investigated after chorionic villus sampling at the first trimester and amniocentesis at the second trimester of pregnancy. Light microscopy revealed heterogeneous morphology of cell types in both the chorionic villus culture and the amniotic fluid cultures. Based on the experiments performed, chorionic villus cells are more sensitive to pronase, trypsin, and versene during subculture and have a higher DNA content per single cell and release more [125I]-Beta-human chorionic gonadotropin into culture medium than those found in amniotic fluid cells. The practical applications of this study are discussed. 相似文献
728.
Reverse phase HPLC of radioactive globin chains has been compared to classical carboxy methyl cellulose chromatography for the prenatal diagnosis of β thalassaemia. The two methods correlated highly (r = 0.97 p < 0.0005) and provided an identical diagnosis for 40 fetal blood samples of fetuses homozygous or heterozygous for β thalassaemia. The HPLC procedure was much faster and required fewer biochemical steps (no globin preparation). It was at least as accurate and more sensitive than the classical chromatography. A single column can be used for 150 analyses and is always ready to be used. Last but not least it is much less expensive than CMC chromatography. 相似文献
729.
730.
The polymerase chain reaction (PCR) was used on material from a blighted ovum to confirm indirectly the carrier status of a woman with a family history of Becker muscular dystrophy. Conventional testing including creatine kinase levels, muscle biopsy, and EMG had been inconclusive, and on the basis of one elevated creatine kinase level, the woman had been designated a possible carrier. Ultrasound examination at 10 weeks of pregnancy indicated a blighted ovum, from which DNA was subsequently extracted and subjected to PCR testing for determination of sex and genotypic status with respect to the known familial deletion of the dystrophin gene. The blighted ovum was found to have a Y chromosome and also to be deleted for at least exon 6 of the dystrophin gene, indirectly indicating that the mother most likely carried the family mutation for Becker muscular dystrophy. 相似文献