全文获取类型
收费全文 | 84061篇 |
免费 | 1215篇 |
国内免费 | 1058篇 |
专业分类
安全科学 | 3626篇 |
废物处理 | 2982篇 |
环保管理 | 13135篇 |
综合类 | 20844篇 |
基础理论 | 25404篇 |
环境理论 | 71篇 |
污染及防治 | 11648篇 |
评价与监测 | 5036篇 |
社会与环境 | 3112篇 |
灾害及防治 | 476篇 |
出版年
2022年 | 773篇 |
2021年 | 774篇 |
2020年 | 635篇 |
2019年 | 849篇 |
2018年 | 1027篇 |
2017年 | 1056篇 |
2016年 | 2071篇 |
2015年 | 1809篇 |
2014年 | 2554篇 |
2013年 | 9201篇 |
2012年 | 1903篇 |
2011年 | 1928篇 |
2010年 | 3119篇 |
2009年 | 3244篇 |
2008年 | 1422篇 |
2007年 | 1215篇 |
2006年 | 1802篇 |
2005年 | 1896篇 |
2004年 | 2222篇 |
2003年 | 2038篇 |
2002年 | 1604篇 |
2001年 | 1781篇 |
2000年 | 1736篇 |
1999年 | 1389篇 |
1998年 | 1339篇 |
1997年 | 1318篇 |
1996年 | 1441篇 |
1995年 | 1531篇 |
1994年 | 1435篇 |
1993年 | 1288篇 |
1992年 | 1269篇 |
1991年 | 1246篇 |
1990年 | 1191篇 |
1989年 | 1164篇 |
1988年 | 1004篇 |
1987年 | 947篇 |
1986年 | 980篇 |
1985年 | 1047篇 |
1984年 | 1140篇 |
1983年 | 1156篇 |
1982年 | 1166篇 |
1981年 | 1087篇 |
1980年 | 932篇 |
1979年 | 902篇 |
1978年 | 812篇 |
1977年 | 705篇 |
1976年 | 629篇 |
1975年 | 589篇 |
1973年 | 611篇 |
1972年 | 615篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
811.
We report a gas chromatographic-mass spectrometric method which allows the very long chain fatty acids content of trophoblastic tissue to be directly measured in samples collected by biopsy between 8 and 11 weeks of gestation. This method has been successfully applied to the detection of fetal Zellweger syndrome in two pregnant women who had previously delivered affected infants. In one of them, increased concentrations of C26:0 (0.254 versus 0.108±0.035 μ/mg proteins) and C24:0 (1.32 versus 0.815±0.325 μ/mg proteins) in trophoblast indicated that the fetus had Zellweger syndrome, a diagnosis confirmed by pathological findings after abortion. In the second case, the pregnancy was allowed to proceed, on the basis of normal concentrations of very long chain fatty acids in trophoblastic tissue, and its outcome was actually a healthy newborn. 相似文献
812.
Distribution of Meynert cells in primate striate cortex 总被引:1,自引:0,他引:1
W. Fries 《Die Naturwissenschaften》1986,73(9):557-558
813.
814.
815.
816.
817.
818.
Harold N. Bass Joan B. Oliver Murali Srinivasan Ruth Petrucha Won Ng Jo Ellen S. Lee 《黑龙江环境通报》1986,6(1):33-35
Intrauterine fetal demise (IUFD) in one of twins at 12 weeks of gestation was accompanied by markedly elevated maternal serum alpha-fetoprotein (AFP) at 17 and 18 weeks. Amniotic fluid AFP from the healthy surviving twin's sac at 18·5 and 23 weeks was also greatly increased along with a positive acetylcholinesterase (AChE) band. Persistently elevated AFP and positive AChE so long after fetal demise–-6·5 and 11 weeks post IUFD–-has not, to our knowledge, been previously described. In similar cases, high level ultrasound and careful placental examination at birth should be utilized to search for fetal abnormalities or multiple pregnancy with IUFD. 相似文献
819.
Frances R. Sweetman Kenneth M. Gibson Lawrence Sweetman Ph.D William L. Nyhan Homer Chin William Swartz Oliver W. Jones 《黑龙江环境通报》1986,6(3):187-194
We have documented the presence of five mitochondrial enzymes in samples of chorionic villus tissue and measured the levels of activity. Three of the enzymes catalyse biotindependent reactions. These are propionyl-CoA carboxylase, 3-methylcrotonyl-CoA carboxylase and pyruvate carboxylase. the other enzymes. 4-aminobutyric acid aminotransferase and succinic semialdehyde dehydrogenase, are involved inthe degradation of the central inhibitory neurotransmitter GABA. Distinct diseases in whichthere is deficiency of each of these enzymes have been documented in man. Significant levels of activity were observed for all five enzymes in chorionic villus tissue. This methodology should permit early prenatal diagnosis of deficiencies of these enzymes by chorionic villus biopsy in the first trimester. 相似文献
820.