全文获取类型
收费全文 | 6480篇 |
免费 | 63篇 |
国内免费 | 90篇 |
专业分类
系统科学 | 65篇 |
丛书文集 | 69篇 |
教育与普及 | 25篇 |
理论与方法论 | 15篇 |
现状及发展 | 2451篇 |
研究方法 | 303篇 |
综合类 | 3673篇 |
自然研究 | 32篇 |
出版年
2021年 | 49篇 |
2016年 | 47篇 |
2015年 | 66篇 |
2014年 | 75篇 |
2013年 | 128篇 |
2012年 | 189篇 |
2011年 | 209篇 |
2010年 | 108篇 |
2009年 | 92篇 |
2008年 | 171篇 |
2007年 | 206篇 |
2006年 | 160篇 |
2005年 | 133篇 |
2004年 | 152篇 |
2003年 | 118篇 |
2002年 | 128篇 |
2001年 | 220篇 |
2000年 | 186篇 |
1999年 | 141篇 |
1992年 | 119篇 |
1991年 | 76篇 |
1990年 | 89篇 |
1989年 | 74篇 |
1988年 | 75篇 |
1987年 | 86篇 |
1986年 | 59篇 |
1985年 | 103篇 |
1984年 | 94篇 |
1983年 | 81篇 |
1982年 | 63篇 |
1981年 | 58篇 |
1980年 | 74篇 |
1979年 | 188篇 |
1978年 | 147篇 |
1977年 | 124篇 |
1976年 | 116篇 |
1975年 | 126篇 |
1974年 | 162篇 |
1973年 | 134篇 |
1972年 | 139篇 |
1971年 | 176篇 |
1970年 | 212篇 |
1969年 | 160篇 |
1968年 | 172篇 |
1967年 | 141篇 |
1966年 | 148篇 |
1965年 | 113篇 |
1958年 | 68篇 |
1957年 | 47篇 |
1954年 | 47篇 |
排序方式: 共有6633条查询结果,搜索用时 8 毫秒
871.
A DNA insertion in the apolipoprotein A-I gene of patients with premature atherosclerosis 总被引:2,自引:0,他引:2
Apolipoprotein A-I (apo A-I) is the major protein constituent of high-density lipoprotein (HDL). The study of the apo A-I gene is of interest because plasma levels of HDL have been inversely correlated with the development of coronary artery disease and because polymorphisms related to this gene have been associated with hypertriglyceridaemia and premature atherosclerosis. We have recently isolated and characterized the human apo A-I gene and have shown that apo A-I and apolipoprotein C-III (apo C-III) genes are physically linked and that a polymorphism (of unknown frequency in the general population) of the apo A-I gene is inherited as a mendelian trait linked to premature atherosclerosis in an affected family (not the same polymorphism as has previously been reported to be associated with hypertriglyceridaemia). Here we report that this polymorphism is due an at least 6.5-kilobase (kb) DNA insertion in the coding region of the apo A-I gene and that there is no detectable alteration (as determined by limited genomic blotting analysis) of the apo C-III gene of these patients. 相似文献
872.
D. Bergqvist I. M. Nilsson M. Pandolfi 《Cellular and molecular life sciences : CMLS》1984,40(1):67-68
Summary An extractive fibrinolytic enzyme has been characterized and found to belong to the class of vascular plasminogen activators. The agent has been found to have an antithrombotic action in the rabbit.Provided by Dr L. Dussourd d'Hinterland, Laboratoires Pierre Fabre, Castres, France. 1000 units have a fibrinolytic activity of about 15 PU urokinase. 相似文献
873.
Calmodulin and pancreatic B-cell function 总被引:1,自引:0,他引:1
874.
V. Jiráček I. Macháčková J. Koštíř 《Cellular and molecular life sciences : CMLS》1972,28(10):1164-1165
Summary Fifteen-day-old green pea seedlings were intoxicated 48 h by 1% gaseous sulphur dioxide and in their individual organs the activity of glutamate-oxalacetate (l-aspartate: 2-ketoglutarate-aminotransferase) and aspartate-pyruvate (l-alanine: oxalacetate-aminotransferase) transaminases estimated. The activity of glutamate-oxalacetate transaminase in the intoxicated seedlings was lowered in shoots by 77.8% and in roots by 78,9% as compared with the control plants. The activity of aspartate-pyruvate transaminase was lowered in shoots by 33.5%, in roots by 76% and in cotyledons by 54.5% in comparison with the control plants. 相似文献
875.
876.
877.
878.
879.
880.