全文获取类型
收费全文 | 145篇 |
免费 | 12篇 |
出版年
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 14篇 |
2012年 | 9篇 |
2011年 | 7篇 |
2010年 | 1篇 |
2009年 | 6篇 |
2008年 | 3篇 |
2007年 | 4篇 |
2006年 | 4篇 |
2005年 | 5篇 |
2004年 | 3篇 |
2003年 | 6篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1973年 | 1篇 |
1968年 | 2篇 |
1962年 | 1篇 |
1961年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有157条查询结果,搜索用时 15 毫秒
1.
The mechanism of resistance to gentamicin and tobramycin in a clinical isolate ofAcinetobacter baumannii, in which aminoglycoside-modifying enzymes were not detected, was investigated. For increase of the resistance gene product, DNA prepared from theA. baumannii isolate was cloned into pUC18 and introduced intoEscherichia coli by transformation. Gentamicin-resistant transformants were screened for aminoglycoside-modifying enzymes. This approach identified two genes encoding AAC(3) and AAD(2) activity, respectively. To determine whether both genes are expressed in the hostAcinetobacter strain, we extracted total cellular RNA from this strain, and Northern blots were hybridized with the cloned AAC(3) and AAD(2) structural genes. mRNA transcribed from the AAC(3) gene alone was detected. This shows that cloning a functional resistance gene is not sufficient in itself to investigate mechanisms of resistance in bacterial strains without detectable aminoglycoside-modifying activity. Furthermore, this study suggests a potential limitation of antibiotic resistance gene probes for studying mechanisms of resistance. 相似文献
2.
G. J. Steyn 《Cryobiology》1993,30(6)
Cryoprotective agents were evaluated to find the optimal concentration of the cryoprotectant and most suitable combination of solution and cryoprotectant. A cryoprotective agent composed of 4% glucose and 9% glycerol yielded the best results. It was established that the optimal freezing rate is dependent on the composition of the cryoprotective agent. Maximal survival of catfish spermatozoa (60%) occurs at 5°C min-1 and faster and slower freezing rates result in poor survival or no survival at all. Incorporation of an isothermal holding period into the freezing rate led to remarkable increase (20-30%) in sperm survival when Me2SO was present in the cryoprotective agent. Cryoprotective agents containing glucose also showed improved survival when a three phase freezing rate was used. These results lead to the conclusion that the presence of an isothermal holding period in the freezing rate is beneficial for the cryoprotective action of Me2SO and glucose. 相似文献
3.
Cloning and expression in Escherichia coli of a recA homologue from Mycobacterium tuberculosis. 总被引:1,自引:0,他引:1
A 3.8 kb PstI fragment of Mycobacterium tuberculosis was cloned in a recA-deleted Escherichia coli by selecting transformants with increased EMS resistance. The cloned fragment restored homologous recombination in Hfr crosses and conferred resistance to long wave (302 nm) but not short wave (254 nm) UV light. E. coli containing the 3.8 kb PstI fragment produced a 38-40 kDa protein which cross-reacted with antibodies raised against the E. coli RecA protein. The cloned DNA thus probably encodes a RecA homologue. 相似文献
4.
5.
Production of sterigmatocystin by Aspergillus versicolor and Bipolaris sorokiniana on semisynthetic liquid and solid media. 总被引:4,自引:4,他引:0 下载免费PDF全文
Higher yields of sterigmatocystin were obtained with Aspergillus versicolor than with Bipolaris sorokiniana both in liquid and on solid media. The optimum temperature for sterigmatocystin production by A. versicolor was 27 to 29 degrees C and 23 degrees C for B. sorokiniana. In liquid shake cultures, production of sterigmatocystin by B. sorokiniana was negligible, whereas maximal production by A. versicolor was 210 mg/liter. On solid substrates, the highest yields (8 g/kg) were obtained with A. versicolor on still cultures of whole corn supplemented with Soytone. 相似文献
6.
7.
Peter Steyn 《Ostrich》2013,84(3-4):173-178
Steyn, P. 1999. The breeding biology of the Scimitarbilled Woodhoopoe. Ostrich 70 (3&4): 173–178. The breeding biology of the Scimitarbilled Woodhoopoe Rhinopomastus cyanomelas was studied at two sites in Zimbabwe over a 13-year period from 1964–1977. The pairs were resident, remained together throughout the year, and inspected their nest sites occasionally during the non-breeding season. The breeding season extended from August to December with a marked September/October peak. Eggs were laid at daily intervals. Clutch size averaged 2.9 (range 2–4). Incubation began either with the penultimate or last laid egg. During the 13–14 day incubation period the female left the nest only occasionally each day and was reliant on the male for food. This pattern continued for four days after the chicks hatch. Thereafter she started to forage and gradually increased her contribution to chick provisioning until she overtook that of the male. With one exception, he never fed the chicks directly and delivered the food to the female. The nestlings were brooded overnight for the first two weeks. The anti-predator response of the young included a malodorous brown exudation from the preen gland and unpleasant liquid excreta. The nestling period was 21–24 days and the young left the vicinity of the nest with their parents and did not return to roost in it. Twelve breeding cycles were monitored and 76% of eggs laid (n=37) produced fledged young. Second broods were raised in the same nest on two occasions after successful rearing of the first, presumably by the same pair, but the birds were not individually marked. There was no evidence of helpers at the nest. 相似文献
8.
A receptor linked to a Gi-family G-protein functions in initiating oocyte maturation in starfish but not frogs 总被引:1,自引:0,他引:1
The stimulation of oocyte maturation by 1-methyladenine in starfish, and by a steroid in frogs, has been proposed to involve G-protein-coupled receptors. To examine whether activation of receptors linked to G(i) or G(z) was sufficient to cause oocyte maturation, we expressed mammalian G(i)- and G(z)-linked receptors in starfish and frog oocytes. Application of the corresponding agonists caused meiosis to resume in the starfish but not the frog oocytes. We confirmed that the receptors were effectively expressed in the frog oocytes by using a chimeric G-protein, G(qi), that converts input from G(i)- and G(z)-linked receptors to a G(q) output and results in a contraction of the oocyte's pigment. These results argue against G(i) or G(z) functioning to cause maturation in frog oocytes. Consistently, maturation-inducing steroids did not cause pigment contraction in frog oocytes expressing G(qi), and G(z) protein was not detectable in frog oocytes. For starfish oocytes, however, our results support the conclusion that G(i) functions in 1-methyladenine signaling and suggest the possibility of using frog oocyte pigment contraction as an assay to identify the 1-methyladenine receptor. To test this concept, we coexpressed G(qi) and a starfish adenosine receptor in frog oocytes and showed that applying adenosine caused pigment contraction. 相似文献
9.
The biofilm proteome of a dairy-associated Bacillus cereus strain (B. cereus 5) was investigated. Biofilm biomass of sufficient concentration for 2D-PAGE was obtained by growing the culture in the presence of glass wool. B. cereus 5 readily attached to the glass wool and biofilms formed within 18 h. The biofilm proteome of whole-cell proteins revealed that 10 proteins were synthesized as a result of surface attachment of which four were unique to the biofilm profile. Seven proteins appeared to be absent in the biofilm profile. The altered proteomes indicated that changes took place in the regulation of protein expression when B. cereus 5 cells attached to surfaces. 相似文献
10.
Lippa B Kauffman GS Arcari J Kwan T Chen J Hungerford W Bhattacharya S Zhao X Williams C Xiao J Pustilnik L Su C Moyer JD Ma L Campbell M Steyn S 《Bioorganic & medicinal chemistry letters》2007,17(11):3081-3086
The synthesis and biological evaluation of potent and selective inhibitors of the erbB2 kinase is presented. Based on the 4-anilinoquinazoline chemotype, the syntheses of several new series of erbB2 inhibitors are described with quinazoline and pyrido[4,3-d]pyrimidine cores. The vast majority of these compounds are found to be >100x selective over the closely related EGFR kinase. Two lead compounds are further shown to have low clearance and moderate bioavailability in rat. 相似文献