全文获取类型
收费全文 | 49281篇 |
免费 | 496篇 |
国内免费 | 586篇 |
专业分类
安全科学 | 1378篇 |
废物处理 | 2207篇 |
环保管理 | 5604篇 |
综合类 | 10392篇 |
基础理论 | 11964篇 |
环境理论 | 29篇 |
污染及防治 | 12796篇 |
评价与监测 | 3217篇 |
社会与环境 | 2521篇 |
灾害及防治 | 255篇 |
出版年
2022年 | 588篇 |
2021年 | 555篇 |
2020年 | 379篇 |
2019年 | 446篇 |
2018年 | 851篇 |
2017年 | 848篇 |
2016年 | 1239篇 |
2015年 | 927篇 |
2014年 | 1439篇 |
2013年 | 3788篇 |
2012年 | 1686篇 |
2011年 | 2216篇 |
2010年 | 1810篇 |
2009年 | 1809篇 |
2008年 | 2188篇 |
2007年 | 2207篇 |
2006年 | 1886篇 |
2005年 | 1609篇 |
2004年 | 1529篇 |
2003年 | 1533篇 |
2002年 | 1402篇 |
2001年 | 1720篇 |
2000年 | 1180篇 |
1999年 | 760篇 |
1998年 | 517篇 |
1997年 | 527篇 |
1996年 | 510篇 |
1995年 | 641篇 |
1994年 | 639篇 |
1993年 | 517篇 |
1992年 | 550篇 |
1991年 | 531篇 |
1990年 | 577篇 |
1989年 | 530篇 |
1988年 | 432篇 |
1987年 | 410篇 |
1986年 | 377篇 |
1985年 | 400篇 |
1984年 | 422篇 |
1983年 | 418篇 |
1982年 | 407篇 |
1981年 | 392篇 |
1980年 | 313篇 |
1979年 | 342篇 |
1978年 | 294篇 |
1974年 | 243篇 |
1972年 | 254篇 |
1971年 | 243篇 |
1967年 | 267篇 |
1966年 | 245篇 |
排序方式: 共有10000条查询结果,搜索用时 468 毫秒
841.
A 17-year-old woman was referred for amniocentesis due to a low maternal serum alpha-fetoprotein (AFP) concentration in a voluntary screening test. The fetal karyotype was 48,XXYY, and the pregnancy was terminated. Autopsy of the fetus disclosed agenesis of the corpus callosum and unusual facial features. 相似文献
842.
A simplified method is described for processing both direct preparations and long-term cultures from the same fragment of chorionic villi. Enzyme separation of the outer trophoblast layers (used for direct preparations) from the inner mesenchymal core (used to initiate long-term cultures) facilitates the utilization of the same fragments for the two procedures, without jeopardizing the success of either method. This has proved useful in cases where the sample was so small that only one method of chromosome preparation may have been possible using other techniques. 相似文献
843.
844.
845.
Dedicated to Professor Dr. Tuneo Yamada on the occasion of his 80th birthday. 相似文献
846.
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
847.
Fetal aspartylglucosaminuria (AGU) was studied during the first trimester of pregnancy in six at-risk pregnancies using chorionic villus samples. The activity of aspartylglucosaminidase (AGA) was high in five cases, indicating an unaffected fetus. This was confirmed through delivery of healthy newborns with a normal pattern of urinary oligosaccharides. Low enzyme activity in an uncultured biopsy specimen and in cultured amniotic fluid cells in one case demonstrated that the fetus was affected. The pregnancy was terminated and the prenatal diagnosis was confirmed by showing reduced AGA activity in cultured fibroblasts of the fetus. 相似文献
848.
849.
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
850.