全文获取类型
收费全文 | 544篇 |
免费 | 57篇 |
出版年
2022年 | 3篇 |
2021年 | 9篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 7篇 |
2017年 | 8篇 |
2016年 | 16篇 |
2015年 | 26篇 |
2014年 | 19篇 |
2013年 | 45篇 |
2012年 | 39篇 |
2011年 | 41篇 |
2010年 | 23篇 |
2009年 | 20篇 |
2008年 | 24篇 |
2007年 | 26篇 |
2006年 | 35篇 |
2005年 | 26篇 |
2004年 | 32篇 |
2003年 | 27篇 |
2002年 | 24篇 |
2001年 | 12篇 |
2000年 | 6篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1987年 | 3篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1973年 | 2篇 |
1969年 | 2篇 |
1968年 | 2篇 |
1966年 | 3篇 |
1961年 | 3篇 |
1957年 | 2篇 |
1955年 | 2篇 |
1935年 | 2篇 |
排序方式: 共有601条查询结果,搜索用时 31 毫秒
81.
Arno G Siraki Jalal Pourahmad Tom S Chan Sumsullah Khan Peter J O'Brien 《Free radical biology & medicine》2002,32(1):2-10
The rat hepatocyte catalyzed oxidation of 2',7'-dichlorofluorescin to form the fluorescent 2,7'-dichlorofluorescein was used to measure endogenous and xenobiotic-induced reactive oxygen species (ROS) formation by intact isolated rat hepatocytes. Various oxidase substrates and inhibitors were then used to identify the intracellular oxidases responsible. Endogenous ROS formation was markedly increased in catalase-inhibited or GSH-depleted hepatocytes, and was inhibited by ROS scavengers or desferoxamine. Endogenous ROS formation was also inhibited by cytochrome P450 inhibitors, but was not affected by oxypurinol, a xanthine oxidase inhibitor, or phenelzine, a monoamine oxidase inhibitor. Mitochondrial respiratory chain inhibitors or hypoxia, on the other hand, markedly increased ROS formation before cytotoxicity ensued. Furthermore, uncouplers of oxidative phosphorylation inhibited endogenous ROS formation. This suggests endogenous ROS formation can largely be attributed to oxygen reduction by reduced mitochondrial electron transport components and reduced cytochrome P450 isozymes. Addition of monoamine oxidase substrates increased antimycin A-resistant respiration and ROS formation before cytotoxicity ensued. Addition of peroxisomal substrates also increased antimycin A-resistant respiration but they were less effective at inducing ROS formation and were not cytotoxic. However, peroxisomal substrates readily induced ROS formation and were cytotoxic towards catalase-inhibited hepatocytes, which suggests that peroxisomal catalase removes endogenous H(2)O(2) formed in the peroxisomes. Hepatocyte catalyzed dichlorofluorescin oxidation induced by oxidase substrates, e.g., benzylamine, was correlated with the cytotoxicity induced in catalase-inhibited hepatocytes. 相似文献
82.
John E Burden Peg Davis Frank Porreca Arno F Spatola 《Bioorganic & medicinal chemistry letters》2002,12(2):213-216
Substitution in position 4 of the potent opioid peptide YkFA with aliphatic hydrophobic residues resulted in compounds that retained low nanomolar activities at both mu and delta opioid receptors, while ring contraction by incorporation of diaminobutyric acid in position 2 resulted in a more pronounced decrease in potency at both receptors for the psi[CH(2)NH] pseudopeptide as compared to the all amide parent. 相似文献
83.
84.
Galande Amit K. Spatola Arno F. 《International journal of peptide research and therapeutics》2001,8(3-5):247-251
Summary A series of disulfide bridged peptides were designed as potential inhibitors of protein-protein interactions. Following solid
phase synthesis, completely deprotected linear peptides were first oxidized to their disulfide analogs and then transformed
into their lanthionine equivalents via a base-assisted reaction in water. Peptides consisting of cystine bridges of lengthi, i+3, with and without discrimination of the chiral centers, were studied for this transformation. Lanthionine peptides were also
obtained directly from the reduced linear peptides under mild alkaline treatment, and the reaction proceeded via disulfide
bond formation. The extent of conversion of a disulfide bridge into its lanthionine counterpart varied according to the primary
sequence. Product characterization revealed diastereomeric lanthionine formation. The presence of D-amino acids, peptide conformation,
and/or position of the cystine bridge are among the factors determining the facility of this reaction. Elimination of the
backbone proton beta to the sulfur atom followed by intramolecular thiol Michael addition is the most likely mechanism for
this transformation. 相似文献
85.
86.
87.
88.
89.
90.
Michel Randriaminahy Ludger Witte Arno Kunze Victor Wray Peter Proksch 《Biochemical Systematics and Ecology》1992,20(8):711-722
Five naturally occurring chromenes from the Asteraceae including the insecticidal compounds precocene II (1) and encecalin (2) were administered to last instar larvae of Spodoptera littoralis via the food or by topical contact. Metabolites formed and excreted via the frass were analysed by GC-MS and by direct comparison with reference compounds obtained by partial synthesis. In total 28 different metabolites were identified, many of them reported here for the first time. All metabolites detected originated from phase I reactions (most probably catalysed by Cytochrom P-450-dependent monooxygenases) by hydroxylation, demethylation or reduction of the parent chromenes. The resulting metabolites can be regarded as detoxification products based on previous structure-activity studies. The increased polarity of the metabolites will furthermore facilitate their excretion by the larvae compared to the more apolar parent chromenes. The largest number of metabolites (eight for each compound) was detected following oral treatment with precocene II and encecalin respectively. 3-Monool as well as 3,4-trans-diol derivatives predominated in the frass of larvae treated with the latter compounds whereas the 6-hydroxyethyl derivatives were the major metabolites of the other chromenes investigated. The patterns of metabolites originating from precocene II or encecalin were the same following oral application or topical treatment. 相似文献