全文获取类型
收费全文 | 286篇 |
免费 | 62篇 |
出版年
2018年 | 4篇 |
2016年 | 3篇 |
2015年 | 6篇 |
2014年 | 6篇 |
2013年 | 11篇 |
2012年 | 8篇 |
2011年 | 9篇 |
2010年 | 7篇 |
2008年 | 8篇 |
2007年 | 9篇 |
2006年 | 10篇 |
2005年 | 4篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2000年 | 4篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1993年 | 6篇 |
1992年 | 10篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 5篇 |
1979年 | 12篇 |
1978年 | 5篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 12篇 |
1973年 | 6篇 |
1972年 | 5篇 |
1971年 | 11篇 |
1970年 | 5篇 |
1969年 | 11篇 |
1968年 | 10篇 |
1967年 | 3篇 |
1966年 | 3篇 |
1964年 | 4篇 |
1962年 | 6篇 |
1960年 | 2篇 |
排序方式: 共有348条查询结果,搜索用时 109 毫秒
81.
82.
83.
84.
85.
Identification of cyclic intermediates in Azorhizobium caulinodans nicotinate catabolism. 总被引:4,自引:4,他引:0
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
In wild-type Azorhizobium caulinodans ORS571, nicotinate served both as anabolic substrate for NAD+ production and as catabolic substrate for use as the N source. Catabolic enzyme activities were greatest from cultures grown with nicotinate as the N source and least when cultures were grown with ammonium as the N source. Vector insertion mutants unable to catabolize nicotinate (nic::Vi mutants) still required micromolar quantities of this compound for growth. Therefore, A. caulinodans wild type is NAD+ auxotrophic. As the first two intermediates in A. caulinodans nicotinate catabolism, two cyclic compounds, 6-hydroxynicotinate and 1,4,5,6-tetrahydro-6-oxonicotinate, were identified. These compounds were purified from the growth medium of strain 61009 (a nic::Vi mutant) by high-performance liquid chromatography; their identities were subsequently confirmed by UV absorbance, nuclear magnetic resonance, and mass spectra. The conversion of 1 mol of nicotinate to 6-hydroxynicotinate consumed 0.5 mol of O2. From 18O isotopic incorporation experiments, water was the hydroxyl-equivalent source. A nicotinate hydroxylase activity proved to be cell wall-membrane associated; this activity served as direct electron donor (not indirect via NADP+) to O2 via membrane electron transport. These catabolic reactions have not previously been witnessed together in the same organism. A. caulinodans nicotinate catabolism seems coupled to N2 fixation, although the explicit mechanism of this coupling remains to be determined. 相似文献
86.
Chromosomal sites of integration of simian virus 40 DNA sequences mapped by in situ hybridization in two transformed hybrid cell lines. 总被引:5,自引:2,他引:3
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The neutralizing characteristics of monoclonal antibodies directed to four antigenic sites on the hemagglutinin-neuraminidase glycoprotein of Newcastle disease virus were determined. Neutralization by each antibody resulted in a persistent fraction of nonneutralized virus which varied from 1 to 17% depending on the hemagglutinin-neuraminidase site recognized, but not on the antibody. The addition of antibodies to all four sites on the hemagglutinin-neuraminidase glycoprotein was required to give a level of neutralization comparable with that obtained with polyclonal mouse antiserum. The high persistent fractions were not due to viral aggregates, a high level of variants in the virus stock, the use of insufficient antibody, low antibody avidity, or an effect peculiar to the use of the chicken cells as host. The addition of rabbit anti-mouse immunoglobulin to the persistent fraction left by any of the antibodies resulted in a further reduction in infectivity, often by as much as two logs. Thus, some viral particles are capable of binding antibody while retaining their infectivity. The implications of these findings to the mechanism of neutralization are discussed. 相似文献
87.
88.
89.
90.
The binding of monoribosomes, oligoribosomes and polyribosomes to reticular membranes from rat liver. 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《The Biochemical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Proteoglycans from pig laryngeal cartilage prepared by dissociative extraction in guanidine hydrochloride were studied in dilute solution by light-scattering and ultracentrifugation. In buffered 150mM-NaCl, pH7.4, the proteoglycan particle weights were about 5x10(6) daltons, but at 100mM-, 200mM- and 300mM-NaCl particle weights of 2.5x10(6)--3.0x10(6) daltons were observed. These results, together with corroborative evidence from sedimentation-velocity experiments, were interpreted in terms of proteoglycans self-associating at physiological ionic strength. The data were examined by using a proteoglycan monomer-dimer model. Proteoglycan preparations that had thiol groups partially carboxymethylated gave particle weights of 3.2x10(6)--3.5x10(6) daltons in 150mM-NaCl, which suggested that carboxymethylation inhibited multimerization and hence that the protein core is implicated in the binding site. Further studies showed that the multimers were stable to 60 degrees C, unlike the hyaluronate-proteoglycan complex. 相似文献