全文获取类型
收费全文 | 1534篇 |
免费 | 161篇 |
国内免费 | 1篇 |
出版年
2022年 | 13篇 |
2021年 | 17篇 |
2019年 | 12篇 |
2017年 | 15篇 |
2016年 | 21篇 |
2015年 | 42篇 |
2014年 | 31篇 |
2013年 | 54篇 |
2012年 | 63篇 |
2011年 | 69篇 |
2010年 | 27篇 |
2009年 | 36篇 |
2008年 | 42篇 |
2007年 | 47篇 |
2006年 | 43篇 |
2005年 | 50篇 |
2004年 | 47篇 |
2003年 | 55篇 |
2002年 | 48篇 |
2001年 | 52篇 |
2000年 | 66篇 |
1999年 | 39篇 |
1998年 | 24篇 |
1997年 | 14篇 |
1995年 | 12篇 |
1994年 | 13篇 |
1992年 | 25篇 |
1991年 | 27篇 |
1990年 | 21篇 |
1989年 | 21篇 |
1988年 | 21篇 |
1987年 | 32篇 |
1986年 | 37篇 |
1985年 | 29篇 |
1984年 | 27篇 |
1983年 | 42篇 |
1982年 | 22篇 |
1981年 | 23篇 |
1980年 | 23篇 |
1979年 | 29篇 |
1978年 | 30篇 |
1977年 | 24篇 |
1976年 | 19篇 |
1975年 | 17篇 |
1974年 | 20篇 |
1973年 | 15篇 |
1972年 | 13篇 |
1971年 | 21篇 |
1969年 | 13篇 |
1964年 | 11篇 |
排序方式: 共有1696条查询结果,搜索用时 15 毫秒
1.
Cultured porcine thoracic aorta endothelial cells were covalently labeled with 4-maleimido-2,2,6,6-tetramethylpiperidinooxyl. Electron paramagnetic resonance spectrometry revealed two major binding environments representing strongly and weakly immobilized species. The disorder parameter of weak/strong, determined from the respective peak amplitudes, was irreversibly elevated following incubation of endothelial cells with a superoxide-generating system, indicating increased membrane fluidity. The rate of increase in membrane disorder was dependent upon superoxide generation rates. Incorporation of the spin-label at concentrations less than 250 microM had no effect on cell viability. The cellular proteins reacting with the spin-label were predominantly membrane proteins, characterized by immunoblotting using a rabbit anti-4-maleimido-2,2,6,6-tetramethylpiperidinooxyl IgG, following sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electrophorectic transfer to nitrocellulose. 相似文献
2.
3.
A spontaneous rhythmic motility of the isolated intestine in snail, Chryptomphalus hortensis, has been registered at 30 degrees C with the aid of an electronic transductor and an appropriate amplification. These slow regular movements are affected by ionic composition changes in the suspension medium. Na+, K+ and Ca++ ions prove to be important in this motility, and the addition of Ba++ markedly stimulates it. ACh produces hypermotility from 1.8 X 10(-11) g/ml. Its effect decreases in the presence of atropine and increases in that of pyridostigmine. The intestine is sensitive to 5-HT from 10(-10) g/ml, which stimulates its activity. The effect of histamine is weak. Low concentrations of adrenaline tend to increase the amplitude, whereas concentrations from 10(-5) g/ml onward produce a cease of motility in relaxation. 相似文献
4.
Nucleotide sequencing of the second Synechocystis 6803 psbG gene, psbG2 shows the predicted polypeptide to be 219 amino acids long. It is less similar to chloroplast psbG genes than is the Synechocystis psbG1 copy. Alignment with seven other psbG protein sequences, including that from the Paramecium mitochondrial genome reveals a central highly conserved region common to each. This is discussed as evidence supporting the proposal that the psbG polypeptide is a NAD(P)H dehydrogenase (complex I) subunit in cyanobacteria, chloroplasts and mitochondria. 相似文献
5.
6.
7.
8.
Using an enzyme-linked immunosorbent assay (ELISA) based technique, Schistocephalus solidus infection was shown to considerably reduce levels of spiggin in the kidney of male three-spined sticklebacks Gasterosteus aculeatus from an oligotrophic upland lake. These results suggested a graduated effect of the infection on the reproductive physiology of male three-spined sticklebacks. 相似文献
9.
10.
Penicillium citrinum cultures have been germinated on an H2O-based medium, resuspended on a D2O-based medium and treated with [l,2-13C2] acetate. The resulting citrinin (1) has been analysed by2H and13C nuclear magnetic resonance spectroscopy and information about the metabolism of hydrogen in citrinin biosynthesis has been deduced. 相似文献