全文获取类型
收费全文 | 34822篇 |
免费 | 366篇 |
国内免费 | 273篇 |
专业分类
安全科学 | 973篇 |
废物处理 | 1452篇 |
环保管理 | 4805篇 |
综合类 | 5366篇 |
基础理论 | 9559篇 |
环境理论 | 14篇 |
污染及防治 | 9358篇 |
评价与监测 | 2175篇 |
社会与环境 | 1515篇 |
灾害及防治 | 244篇 |
出版年
2022年 | 224篇 |
2021年 | 266篇 |
2019年 | 249篇 |
2018年 | 427篇 |
2017年 | 446篇 |
2016年 | 735篇 |
2015年 | 574篇 |
2014年 | 866篇 |
2013年 | 2836篇 |
2012年 | 1047篇 |
2011年 | 1430篇 |
2010年 | 1150篇 |
2009年 | 1236篇 |
2008年 | 1471篇 |
2007年 | 1581篇 |
2006年 | 1390篇 |
2005年 | 1158篇 |
2004年 | 1169篇 |
2003年 | 1107篇 |
2002年 | 1078篇 |
2001年 | 1346篇 |
2000年 | 1006篇 |
1999年 | 567篇 |
1998年 | 444篇 |
1997年 | 448篇 |
1996年 | 493篇 |
1995年 | 524篇 |
1994年 | 501篇 |
1993年 | 461篇 |
1992年 | 433篇 |
1991年 | 419篇 |
1990年 | 447篇 |
1989年 | 419篇 |
1988年 | 390篇 |
1987年 | 369篇 |
1986年 | 330篇 |
1985年 | 314篇 |
1984年 | 384篇 |
1983年 | 345篇 |
1982年 | 389篇 |
1981年 | 361篇 |
1980年 | 297篇 |
1979年 | 320篇 |
1978年 | 262篇 |
1977年 | 232篇 |
1976年 | 209篇 |
1975年 | 213篇 |
1974年 | 211篇 |
1973年 | 224篇 |
1972年 | 230篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
531.
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
532.
533.
534.
R. B. H. Schutgens G. Schrakamp R. J. A. Wanders H. S. A. Heymans H. W. Moser A. E. Moser J. M. Tagers H. V. D. Bosch P. Aubourm 《黑龙江环境通报》1985,5(5):337-344
Prenatal diagnosis of the cerebro-hepato-renal (Zellweger) syndrome has been performed in 10 pregnancies at risk by measuring both the activity of acyl CoA: dihydroxyacetonephosphate acyltransferase (DHAP-AT) and the de novo plasmalogen biosynthesis, either in cultured amniotic fluid cells or in fibroblasts cultured from a chorionic villus biopsy. In 7 of the pregnancies both tests indicated no abnormality. All 7 continued to term and normal infants were delivered. However, in amniotic fluid cells from 2 fetuses affected by Zellweger syndrome unequivocal differences from control values were found. The activity of DHAP-AT was clearly deficient and the de novo plasmalogen biosynthesis was impaired. In one pregnancy at risk prenatal diagnosis was performed during the first trimester by measuring both the DHAP-AT activity and the de novo plasmalogen biosynthesis in fibroblasts cultured from a chorionic villi biopsy. From the deficient DHAP-AT activity and the impaired de novo plasmalogen biosynthesis it was concluded that the fetus was affected. This was confirmed biochemically after induced abortion. It can be concluded that measurement of the DHAP-AT activity and the de novo plasmalogen biosynthesis provides convenient methods for the early prenatal detection of Zellweger syndrome. 相似文献
535.
536.
537.
538.
539.
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
540.
C. Vaccarino G. Cimino M.M. Tripodo G. Lagan L. Lo Giudice R. Matarese 《Agriculture, ecosystems & environment》1983,10(3):275-283
Necrotic brown lesions developing on leaves and fruits of lemon, and other plants, near fossil-fuel-burning power plants emitting vanadium-rich ash, were reproduced experimentally by inoculating leaves with this type of ash, which is strongly acidic. Comparable lesions were formed when drops of vanadium oxide, dissolved in NaOH, were put on leaves and fruits. Neutralizing, or adding excess H2SO4 (to pH 3), did not alter lesion formation. The histology of these lesions was similar to that of lesions attributed to vanadium-rich ash. 相似文献