全文获取类型
收费全文 | 1165篇 |
免费 | 57篇 |
出版年
2023年 | 11篇 |
2022年 | 17篇 |
2021年 | 42篇 |
2020年 | 18篇 |
2019年 | 35篇 |
2018年 | 45篇 |
2017年 | 15篇 |
2016年 | 44篇 |
2015年 | 70篇 |
2014年 | 68篇 |
2013年 | 77篇 |
2012年 | 81篇 |
2011年 | 90篇 |
2010年 | 45篇 |
2009年 | 42篇 |
2008年 | 63篇 |
2007年 | 67篇 |
2006年 | 57篇 |
2005年 | 30篇 |
2004年 | 29篇 |
2003年 | 33篇 |
2002年 | 22篇 |
2001年 | 20篇 |
2000年 | 23篇 |
1999年 | 20篇 |
1998年 | 13篇 |
1997年 | 11篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 14篇 |
1989年 | 4篇 |
1988年 | 14篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 8篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1963年 | 1篇 |
排序方式: 共有1222条查询结果,搜索用时 15 毫秒
21.
C Costa J J Moura I Moura M Y Liu H D Peck J LeGall Y N Wang B H Huynh 《The Journal of biological chemistry》1990,265(24):14382-14388
M?ssbauer and EPR spectroscopy were used to characterize the heme prosthetic groups of the nitrite reductase isolated from Desulfovibrio desulfuricans (ATCC 27774), which is a membrane-bound multiheme cytochrome capable of catalyzing the 6-electron reduction of nitrite to ammonia. At pH 7.6, the as-isolated enzyme exhibited a complex EPR spectrum consisting of a low-spin ferric heme signal at g = 2.96, 2.28, and 1.50 plus several broad resonances indicative of spin-spin interactions among the heme groups. EPR redox titration studies revealed yet another low-spin ferric heme signal at g = 3.2 and 2.14 (the third g value was undetected) and the presence of a high-spin ferric heme. M?ssbauer measurements demonstrated further that this enzyme contained six distinct heme groups: one high-spin (S = 5/2) and five low-spin (S = 1/2) ferric hemes. Characteristic hyperfine parameters for all six hemes were obtained through a detailed analysis of the M?ssbauer spectra. D. desulfuricans nitrite reductase can be reduced by chemical reductants, such as dithionite or reduced methyl viologen, or by hydrogenase under hydrogen atmosphere. Addition of nitrite to the fully reduced enzyme reoxidized all five low-spin hemes to their ferric states. The high-spin heme, however, was found to complex NO, suggesting that the high-spin heme could be the substrate binding site and that NO could be an intermediate present in an enzyme-bound form. 相似文献
22.
1. Ferricytochrome c3 from D. gigas exhibits two low-spin ferric heme EPR resonances with gz-values at 2.959 and 2.853. Ferrocytochrome c3 is diamagnetic based on the absence of any EPR signals. 2. EPR potentiometric titrations result in the resolution of the two low-spin ferric heme resonances into two additional heme components representing in total the four hemes of the cytochrome, with EM values of -235 mV and -315 mV at heme resonance I and EM values of -235 mV and -306 mV at heme resonance II. 3. EPR spectroscopy has detected a significant diminution of intensity (approx. 60 p. 100) in the gx amplitude of ferricytochrome c3 in the presence of D. gigas ferredoxin II. The presence of ferredoxin II also causes a more negative shift in the EM of the second components of the signals at heme resonances I and II of cytochrome C3. Both observations suggest that an interaction has occurred between cytochrome C3 and ferredoxin II. 4. The results presented suggest that the heme ligand environment of ferricytochrome c3 from D. gigas is less perturbed and/or less asymmetric than environment for ferricytochrome c3 from D. vulgaris whose EPR behavior indicates the non-equivalence of all four hemes. 相似文献
23.
24.
25.
Mireille Bruschi E.Claude Hatchikian Jean Le Gall JoséJ.G. Moura António V. Xavier 《BBA》1976,449(2):275-284
Three forms of ferredoxin FdI, FdI′, and FdII have been isolated from Desulfovibrio gigas, a sulfate reducer. They are separated by a combination of DEAE-cellulose and gel filtration chromatographic procedures. FdI and FdI′ present a slight difference in isoelectric point which enables the separation of the two forms over DEAE-cellulose, while FdII is easily separated from the two other forms by gel filtration. The three forms have the same amino acid composition and are isolated in different aggregation states. Molecular weight determinations by gel filtration gave values of 18 000 for FdI and FdI′ and 24 000 for FdII, whereas a value of 6000 is determined when dissociation is accomplished with sodium dodecyl sulfate. The electronic spectra are different and their ultraviolet-visible absorbance rations are 0.77, 0.87 and 0.68 respectively for FdI, FdI′ and FdII. Despite these differences, the physiological activities of the three forms are similar as far as the reduction of sulfite by molecular hydrogen is concerned. 相似文献
26.
Luiz Henrique Soares de Andrade Wilson Max Almeida Monteiro de Moraes Eduardo Hiroshi Matsuo Junior Elizabeth de Orleans Carvalho de Moura Hanna Karen Moreira Antunes Jairo Montemor Ednei Luiz Antonio Danilo Sales Bocalini Andrey Jorge Serra Paulo José Ferreira Tucci Patricia Chakur Brum Alessandra Medeiros 《Molecular and cellular biochemistry》2015,402(1-2):193-202
27.
28.
Reis Ricardo Souza Vale Ellen Moura Sousa Kariane Rodrigues Santa-Catarina Claudete Silveira Vanildo 《Plant Cell, Tissue and Organ Culture》2021,145(1):101-115
Plant Cell, Tissue and Organ Culture (PCTOC) - Several factors influence culture conditions and somatic embryogenesis responses, such as the role of plant growth regulators (PGRs) during the... 相似文献
29.
30.