全文获取类型
收费全文 | 692篇 |
免费 | 19篇 |
国内免费 | 9篇 |
专业分类
720篇 |
出版年
2020年 | 6篇 |
2017年 | 17篇 |
2016年 | 7篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 16篇 |
2012年 | 18篇 |
2011年 | 20篇 |
2010年 | 25篇 |
2009年 | 25篇 |
2008年 | 34篇 |
2007年 | 20篇 |
2006年 | 27篇 |
2005年 | 16篇 |
2004年 | 20篇 |
2003年 | 8篇 |
2002年 | 16篇 |
2001年 | 12篇 |
2000年 | 24篇 |
1999年 | 17篇 |
1998年 | 6篇 |
1997年 | 8篇 |
1996年 | 12篇 |
1994年 | 5篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1989年 | 12篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1980年 | 5篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1974年 | 8篇 |
1972年 | 8篇 |
1971年 | 5篇 |
1959年 | 7篇 |
1958年 | 23篇 |
1957年 | 26篇 |
1956年 | 26篇 |
1955年 | 22篇 |
1954年 | 22篇 |
1953年 | 13篇 |
1952年 | 13篇 |
1951年 | 10篇 |
1950年 | 9篇 |
排序方式: 共有720条查询结果,搜索用时 0 毫秒
711.
712.
713.
L. V. Khitrina E. V. Mironova A. A. Khodonov 《Biochemistry (Moscow) Supplemental Series A: Membrane and Cell Biology》2009,3(2):128-133
Modification of the chromophore in bacteriorhodopsin (BR) from ET1001 and D96N strains of Halobacterium salinarum (halobium) was carried out. Purple membranes were decolored by means of light-dependent hydroxylaminolysis. The all-trans -isomers of retinal and its 3,4-didehydro-, 4-keto-, and phenyl analogs were reconstituted into apomembranes. Absorption maxima of the homonymic pigments in both strains were similar. The kinetics of the M-intermediates in the mode of a single turnover of the photocycle induced by a short light flash (532 nm, 15 ns) was compared. For the investigated bacteriorhodopsin analogs the efficiency of the M-intermediate formation did not exhibit any reliable dependence on the point mutation. Both for ET1001 and for D96N strains the M-relaxation of the 4-ketoBR was distinctly biphasic, with the slow phase comprising about 10–15% of the signal amplitude. Replacement of the ionone ring by phenyl caused a weak deceleration of the M relaxation (~1.5-fold decrease in t 1/2). Independence of the photocycle deceleration of the point mutation and chromophore modification was shown for all BR analogs studied. 相似文献
714.
LA Tziveleka D Abatis K Paulus R Bauer C Vagias V Roussis 《Chemistry & biodiversity》2005,2(7):901-909
A series of polyprenylated hydroquinones, quinones, and chromenols were isolated from the extracts of the marine sponge Ircinia spinosula and the brown alga Taonia atomaria, which gave rise to the constituents 1-4 and 5-8, respectively. Compounds 1, 2, 6, and 7 are new natural products, which were fully characterized. Their anti-inflammatory activities in terms of leukotriene formation were evaluated in an in vitro assay with pork leukocytes. The new hydroxylated compound, 2'-[28-hydroxy]heptaprenyl-1',4'-hydroquinone (= 2-[(2E,6E,10E,14E,18Z,22E)-19-(hydroxymethyl)-3,7,11,15,23,27-hexamethyloctacosa-2,6,10,14,18,22,26-heptaen-1-yl]benzene-1,4-diol; 1), the known tetraprenyl benzoquinone sargaquinone (5), and the known polyprenyl chromenols 3 and 4 exhibited the highest anti-inflammatory activities, with IC50 values of 1.9-9.4 microM (Table 3). Potential structure-activity relationships (SAR) are discussed. 相似文献
715.
716.
A total of 204 meningococcus strains were tested for the presence of hyaluronidase, and 45.5% of the strains were found to contain it. Strains penetrating into the cerebrospinal fluid were the ones which largely produced the enzyme (in 83% of the cases). The enzyme was revealed only in 25.5% of the strains habituating on the nasopharyngeal mucosa. Hyaluronidase was mostly found in the meningococcus strains referred to the serological group A; strains of other serological groups and ungrouped strains produced the enzyme in 23.7% of the case only. There was no correlation between the capacity to form hyaluronidase and the virulence determinable in intraperitoneal infection of mice. 相似文献
717.
718.
719.
720.