全文获取类型
收费全文 | 572篇 |
免费 | 49篇 |
出版年
2023年 | 3篇 |
2021年 | 6篇 |
2020年 | 9篇 |
2019年 | 6篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 8篇 |
2015年 | 11篇 |
2014年 | 11篇 |
2013年 | 25篇 |
2012年 | 24篇 |
2011年 | 16篇 |
2010年 | 11篇 |
2009年 | 14篇 |
2008年 | 32篇 |
2007年 | 20篇 |
2006年 | 40篇 |
2005年 | 31篇 |
2004年 | 40篇 |
2003年 | 42篇 |
2002年 | 36篇 |
2001年 | 14篇 |
2000年 | 15篇 |
1999年 | 16篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1993年 | 6篇 |
1992年 | 11篇 |
1991年 | 11篇 |
1990年 | 14篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1978年 | 4篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 6篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1969年 | 3篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1965年 | 3篇 |
排序方式: 共有621条查询结果,搜索用时 15 毫秒
1.
2.
A novel phosphonoglycosphingolipid named SGL-I' containing 1 mol of 2-aminoethylphosphonate residue was isolated from the skin of Aplysia kurodai using two silicic acid chromatography systems. Data obtained on methanolysis, permethylation, mild acid hydrolysis, and hydrogen fluoride treatment combined with thin-layer chromatography, gas liquid chromatography, gas chromatography-mass spectrometry, and proton magnetic resonance spectrometry showed that this glycolipid was 3-O-MeGal beta 1----3GalNAc alpha 1----3[6'-O-(2-aminoethylphosphonyl)Gal alpha 1----2]Gal beta 1----4Glc beta 1----1Ceramide. Palmitic acid, octadeca-4-sphingenine and anteiso-nonadeca-4-sphingenine are its major aliphatic components. The new glycolipid has essentially the same structure as another major phosphonoglycosphingolipid in the skin of Aplysia, SGL-II, that contains 2 mol of 2-aminoethylphosphonate residue, suggesting a metabolic relationship between the two. 相似文献
3.
The role of phospholipase in beta-agonist-induced down regulation in guinea pig lungs 总被引:2,自引:0,他引:2
K Suzuki S Sugiyama K Takagi T Satake T Ozawa 《Biochemical medicine and metabolic biology》1987,37(2):157-166
It has been observed that repeated and prolonged beta-agonist treatment causes the impairment of beta-adrenergic function, so-called "desensitization" or "down regulation". To clarify the mechanism of down regulation, the following experiment was performed using guinea pig lungs. Animals were divided into four groups: In the metaproterenol groups, guinea pigs were treated with metaproterenol (10 mg/kg/day) by intraperitoneal injection once a day for 1 day or for 7 successive days In the control groups, guinea pigs were treated with saline by the same procedure as in the metaproterenol groups. In the group treated with metaproterenol for 7 days, there was a 45% reduction in the number of beta-adrenoceptors and a 62% reduction in adenylate cyclase activity, compared with those of the control group. However, there were no significant changes in the dissociation constant (Kd) of the receptors. On the other hand, no reduction in the number of beta-adrenoceptors and adenylate cyclase activity was observed in the group treated with metaproterenol once a day for 1 day, compared with those of the control group. Phospholipase (PLase) activity in the lung microsomes of guinea pigs injected with metaproterenol for 1 day and for 7 days was elevated by 14.4 and 33.1%, respectively, compared with that of the control groups. Phospholipid contents of lung membranes prepared from the animals treated with metaproterenol for 7 days were significantly decreased compared with those of the control group, though in the group treated with metaproterenol once a day for 1 day, phospholipid contents did not differ from those of the control. Lung membranes treated with PLase A2 revealed decreases both in the number of beta-adrenoceptors and adenylate cyclase activity, dose dependently. These results and the fact that membrane phospholipids are involved in the beta-adrenoceptor system suggest that down regulation observed during beta-agonist administration is, at least in part, attributed to degradation of phospholipids of lung membranes by the persistent activation of PLase in the tissue. 相似文献
4.
Sulfhydryl modification and activation of phenylalanine hydroxylase by dinitrophenyl alkyl disulfide
S Koizumi T Suzuki S Takahashi K Satake T Takeuchi H Umezawa T Nagatsu 《Biochemistry》1987,26(20):6461-6465
A new family of asymmetric thiol-disulfide exchange reagents, the dinitrophenyl alkyl disulfides (DNPSSR), was used to modify rat liver phenylalanine hydroxylase. The results indicate that the enzyme has two different types of reactive sulfhydryl (SH) residues per subunit. One SH residue was modified selectively by a DNPSSR having a neutral and hydrophilic alkyl group, and this modification was accompanied by appreciable activation of enzyme; the other SH residue was modified only by an anionic DNPSSR, and this modification did not result in activation. The catalytic properties of phenylalanine hydroxylase activated by DNPSSR were similar to those of the N-ethylmaleimide- (NEM-) modified enzyme, but the process of activation by DNPSSR was quite different from modification with NEM. An analysis of the reaction kinetics of the modification and of catalysis by the modified enzyme suggests that DNPSSR modification causes a change in the subunit interaction leading to a loss of the negative cooperativity normally seen with phenylalanine hydroxylase. 相似文献
5.
Japanese encephalitis (JE) virus was shown to grow in in vitro cultures of human monocytes. Interferon (IFN)-alpha and IFN-gamma inhibited JE virus production by the infected monocytes in the absence of anti-JE virus antibody, but interleukin (IL)-1 alpha, IL-2, IL-3, granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte-CSF (G-CSF), and tumor necrosis factor (TNF)-alpha did not show a significant inhibition. Antibody against JE virus increased the JE virus production by the infected monocytes probably by enhanced uptake of virus-antibody complexes via Fc receptors. IFN-gamma and GM-CSF increased JE virus production by monocytes in the presence of anti-JE virus antibody, whereas IFN-alpha inhibited JE virus production even in the presence of the antibody. The other 5 cytokines (IL-1 alpha, IL-2, IL-3, G-CSF, and TNF-alpha) did not show a significant effect on JE virus production by monocytes in the presence or absence of the antibody. 相似文献
6.
Hiroshi Yonemitsu Koichiro Shimomura Motoyoshi Satake Shunji Mochida Masahiko Tanaka Thoru Endo Akira Kaji 《Plant cell reports》1990,9(6):307-310
Hairy roots were obtained following inoculation of the stems of Lobelia inflata L. with Agrobacterium rhizogenes strain ATCC 15834. These hairy roots contained agropine and mannopine. In addition, lobeline was detected by HPLC and confirmed by mass spectrometry. Various media were tested for the growth of hairy roots as well as for the content of lobeline in hairy roots. The growth rate of hairy roots cultured in Nitsch and Nitsch's medium was approximately one third of those cultured in other media. The lobeline content of hairy roots (18–54 g/g dry weight) cultured in these media was the same order of magnitude compared with that of roots of L. inflata (24 g/g dry weight) cultivated in pots. The hairy roots cultured in Nitsch and Nitsch's medium were morphologically different from those cultured in other media.Abbreviations MS medium
Murashige and Skoog's medium
- 1/2 MS medium
one-half strength of the standard Murashige and Skoog's medium
- B5 medium
Gamborg's B5 medium
- NN medium
Nitsch and Nitsch's medium
- FW
fresh weight
- DW
dry weight 相似文献
7.
Twelve polyether compounds originating from dinoflagellates were tested for growth-inhibiting activities againstAspergillus niger, Penicillium funiculosum, Candida rugosa, Escherichia coli, Bacillus megaterium andStaphylococcus aureus by a paper disc method. These polyethers represent six groups of different skeletons and originate from three species;Prorocentrum lima, Dinophysis fortii andGambierdiscus toxicus. Potent antifungal activities were observed with okadaic acid and its two congeners, desulfated yessotoxin, and ciguatoxin but not with okadaic acid esters, prorocentrolide, pectenotoxin-1, yessotoxin, maitotoxin, and desulphated maitotoxin. The antifungal activities and mouse lethalities of the polyethers were markedly affected by slight modification of their structures. Antibacterial potency of the tested compounds was not significant. 相似文献
8.
9.
Thermal hysteresis of longitudinal relaxation times (T1) ofwater protons in hypocotyls of etiolated Vigna radiata and V.mungo seedlings was investigated by pulse nuclear magnetic resonance(NMR) spectroscopy. Various lengths of chilling exposures duringa cool-warm cycle between 20 and 0?C (below 10?C, about 4 h)for the T1 hysteresis measurement did not cause any visibleinjury symptoms in hypocotyls. However, the profiles of T1 hysteresisvaried as a result of different chilling exposures. The sumsof the T1 ratio (for detail see Introduction) reflecting T1prolongation or shortening upon the warming process were a goodquantitative index for the extent of T1 hysteresis, and thewide dispersion of this value ranging on the "minus" side (T1prolongation upon warming) suggested the occurrence of a primaryresponse of cells to chilling stress before obvious visiblesymptoms occur while the T1 ratio sums on the "plus" side (T1shortening upon warming) corresponded to a response of seriousvisible injury. Therefore, the sums of the T1 ratio can be usedas a non-destructive diagnostic tool for monitoring the primaryevent of chilling injury when lacking any visible injury symptoms.The data indicate that the critical temperature for the occurrenceof primary response for chilling stress was around 7.5?C forV. radiata and 12.5?C for V. mungo. (Received February 1, 1988; Accepted June 1, 1988) 相似文献
10.