全文获取类型
收费全文 | 540篇 |
免费 | 68篇 |
国内免费 | 1篇 |
出版年
2021年 | 9篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 14篇 |
2017年 | 6篇 |
2016年 | 11篇 |
2015年 | 19篇 |
2014年 | 25篇 |
2013年 | 28篇 |
2012年 | 24篇 |
2011年 | 28篇 |
2010年 | 19篇 |
2009年 | 23篇 |
2008年 | 29篇 |
2007年 | 27篇 |
2006年 | 19篇 |
2005年 | 21篇 |
2004年 | 23篇 |
2003年 | 29篇 |
2002年 | 13篇 |
2001年 | 15篇 |
2000年 | 15篇 |
1999年 | 17篇 |
1998年 | 12篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 13篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1973年 | 4篇 |
1972年 | 6篇 |
1971年 | 4篇 |
1968年 | 3篇 |
1912年 | 2篇 |
1909年 | 3篇 |
排序方式: 共有609条查询结果,搜索用时 15 毫秒
1.
2.
Heat resistance of Listeria: strain differences and effects of meat type and curing salts 总被引:3,自引:1,他引:2
The heat resistances of 27 strains of Listeria monocytogenes and two strains of L. innocua were compared in broth heated at 57°C. No strain was exceptionally resistant. The heat resistance of a representative isolate of L. monocytogenes was compared in fresh and cured beef and chicken, and an equation was derived to predict the time necessary to achieve a '7D' inactivation at temperatures between 50 and 70°C. 相似文献
3.
The survival of Salmonella typhimurium after a standard heat challenge at 55°C for 25 min increased by several orders of magnitude when cells grown at 37°C were pre-incubated at 42°, 45° or 48°C before heating at the higher temperature. Heat resistance increased rapidly after the temperature shift, reaching near maximum levels within 30 min. Elevated heat resistance persisted for at least 10 h. Preincubation of cells at 48°C for 30 min increased their resistance to subsequent heating at 50°, 52°, 55°, 57° or 59°C. Survival curves of resistant cells were curvilinear. Estimated times for a '7D' inactivation increased by 2.6- to 20-fold compared with cells not pre-incubated before heat challenge. 相似文献
4.
5.
Determinants of time-dependent membrane conductance. The nonrole of classical ion-membrane molecule interactions 下载免费PDF全文
We have examined the steady-state and time-dependent electrical properties of a model membrane system. The model assumes that the directed velocity and energy of ions moving through the membrane are determined by the applied electric field, ionic diffusion forces, and central elastic collisions between ions and membrane molecules. A simple analysis of the steady-state electrical properties of the model yields results identical with ones obtained previously using a more complex analysis procedure. The time-dependent conductance changes of the model in response to a step change in electric field strength when there is solution symmetry display three qualitative patterns dependent on the nature of the ion-membrane molecule interaction. One of the patterns of conductance change is quite similar to that observed in the sodium conductance system of a number of excitable tissues: an initial conductance rise to a maximum (activation) followed by a decay to a final steady-state value (inactivation). However, the correspondence between the time-dependent model behavior and known experimental behavior of excitable systems is only qualitative. We conclude that the classical ion-membrane molecule interactions we consider are not involved in determining time-dependent conductance processes in the excitable systems for which comparison is possible. 相似文献
6.
7.
The effect of high hydrostatic pressure on Salmonella thompson and Listeria monocytogenes examined by electron microscopy 总被引:3,自引:0,他引:3
B.M. Mackey K. Forestière N.S. Isaacs R. Stenning B. Brooker 《Letters in applied microbiology》1994,19(6):429-432
Cells of Listeria monocytogenes that had been exposed to pressure contained vacuolar regions in the cytoplasm. Pressure-treated cells of Salmonella thompson contained no vacuoles but had fewer ribosomes than untreated cells and their appearance suggested that some cell lysis had occurred. In both organisms changes in the appearance of the nuclear material were observed. 相似文献
8.
Direct sequencing of the mitochondrial displacement loop (D-loop) of shrews
(genus Sorex) for the region between the tRNA(Pro) and the conserved
sequence block-F revealed variable numbers of 79-bp tandem repeats. These
repeats were found in all 19 individuals sequenced, representing three
subspecies and one closely related species of the masked shrew group (Sorex
cinereus cinereus, S. c. miscix, S. c. acadicus, and S. haydeni) and an
outgroup, the pygmy shrew (S. hoyi). Each specimen also possessed an
adjacent 76-bp imperfect copy of the tandem repeats. One individual was
heteroplasmic for length variants consisting of five and seven copies of
the 79-bp tandem repeat. The sequence of the repeats is conducive to the
formation of secondary structure. A termination-associated sequence is
present in each of the repeats and in a unique sequence region 5' to the
tandem array as well. Mean genetic distance between the masked shrew taxa
and the pygmy shrew was calculated separately for the unique sequence
region, one of the tandem repeats, the imperfect repeat, and these three
regions combined. The unique sequence region evolved more rapidly than the
tandem repeats or the imperfect repeat. The small genetic distance between
pairs of tandem repeats within an individual is consistent with a model of
concerted evolution. Repeats are apparently duplicated and lost at a high
rate, which tends to homogenize the tandem array. The rate of D- loop
sequence divergence between the masked and pygmy shrews is estimated to be
15%-20%/Myr, the highest rate observed in D-loops of mammals. Rapid
sequence evolution in shrews may be due either to their high metabolic rate
and short generation time or to the presence of variable numbers of tandem
repeats.
相似文献
9.
Thermal denaturation and loss of viability in Escherichia coli and Bacillus stearothermophilus 总被引:1,自引:0,他引:1
B. M. Mackey C. A. Miles D. A. Seymour S. E. Parsons 《Letters in applied microbiology》1993,16(2):56-58
When Escherichia coli was heated at 10°C/min in a differential scanning calorimeter, the onset of irreversible thermal denaturation occurred at 51°C, about 5°C above the maximum growth temperature. The temperature at which death rate was maximal (63°C) coincided with the thermogram peak caused by denaturation of the 30S ribosomal subunit. The maximum death rate in vegetative cells of Bacillus stearothermophilus occurred at the higher temperature of 71°C which also coincided with the leading edge of the main thermogram peak. 相似文献
10.