首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   66篇
  免费   3篇
  2021年   1篇
  2019年   4篇
  2018年   2篇
  2017年   3篇
  2016年   2篇
  2015年   3篇
  2014年   5篇
  2013年   1篇
  2012年   4篇
  2011年   5篇
  2010年   3篇
  2009年   1篇
  2008年   5篇
  2007年   2篇
  2006年   4篇
  2005年   1篇
  2004年   1篇
  2003年   2篇
  2002年   2篇
  2000年   2篇
  1998年   1篇
  1995年   1篇
  1994年   3篇
  1993年   1篇
  1992年   1篇
  1989年   1篇
  1986年   1篇
  1984年   1篇
  1980年   2篇
  1979年   1篇
  1977年   1篇
  1976年   1篇
  1975年   1篇
排序方式: 共有69条查询结果,搜索用时 31 毫秒
1.
A new anaerobic thermophilic Gram-positive, nonsporeforming bacterium strain ZE-1 was isolated from a hot spring of Kamchatka (USSR). The cells are rod-shaped, (0.5–0.8 · 2.0–20 m), non-motile. The bacterium can grow between 42 and 75°C; the optimal temperature is 65°C. The growth is possible between pH values 5.0 and 8.5; optimal pH is 7.0. The cultures grow on the media containing peptone, yeast extract, or casein hydrolysate as nitrogen sources in the presence of glucose or some other sugars, mannitol or starch. The main fermentation products of glucose are ethanol, acetate, lactate, H2, CO2; byproducts are propionic, butyric and isovaleric acids. Glucose is metabolized via Embden-Meyerhoff-Parnas pathway. Molecular hydrogen does not inhibit growth. The bacterium does not reduce aceton to isopropanol, but is able to form H2S from elemental sulfur. The bacterium contains a soluble hydrogenase. This enzyme catalyzes both evolution and uptake of H2 and is active in the presence of methyl viologen. The DNA-base composition is 34.6 mol%; the genome size 2.08x109 D. The name proposed for the isolated bacterium strain ZE-1 is Thermoanaerobium lactoethylicum spec. nov.  相似文献   
2.
We have analyzed a total of 12 different global and local multiple protein-sequence alignment methods. The purpose of this study is to evaluate each method's ability to correctly identify the ordered series of motifs found among all members of a given protein family. Four phylogenetically distributed sets of sequences from the hemoglobin, kinase, aspartic acid protease, and ribonuclease H protein families were used to test the methods. The performance of all 12 methods was affected by (1) the number of sequences in the test sets, (2) the degree of similarity among the sequences, and (3) the number of indels required to produce a multiple alignment. Global methods generally performed better than local methods in the detection of motif patterns.   相似文献   
3.
The African Black Oystercatcher Haematopus moquini is a charismatic, southern African near-endemic, wader species, that is often seen as a flagship species for coastal bird conservation, as it was recently down-listed regionally to Least Concern on the IUCN Red List of Threatened Species. To celebrate this rare conservation success story, BirdLife South Africa named it the 2018 Bird of the Year and ran a year-long programme in collaboration with the Nature’s Valley Trust highlighting aspects of the species’ biology, current threats, and conservation success. We used data collected by the Southern African Bird Atlas Project (SABAP1 and SABAP2) to examine changes in the species’ range and relative abundance, both in the records between the two projects, as well as trends within the SABAP2 sampling period (2008–2017). This case study enabled us to assess whether such metrics can accurately reflect abundance and distributional changes in a species. We found increases in the reported range and the reporting rates between the two Atlas projects, and that the SABAP2 reporting rate was stable. Regionally, across four coastal categories, the reporting rate was lowest in KwaZulu-Natal, though this region also showed an increase in the probability of reporting during the SABAP2 period. While corroborating the recent change in the species’ conservation status, we also provide good evidence that the long-term SABAP data can be used successfully to assess population trends and range changes over time.  相似文献   
4.
5.
Using genetic and flow cytometric analyses, we showed that wine strain S6U is an allotetraploid of S. cerevisiae x S. bayanus. Hybrid constitution of the strain and its meiotic segregants was confirmed by Southern hybridization analysis of their chromosomal DNAs using four S. cerevisiae cloned genes: LYS2 (chr. II), TRK1 (chr. X), ARG4 (chr. VIII), ACT1 (chr. VI) and PCR/RFLP analysis of the MET2 gene (chr. XIV). Monosporic progeny of strain S6U was highly viable in first generation but completely nonviable in the second one. According to the genetic analysis, sherry strain S. cerevisiae SBY 2592 was found to be an autotetraploid heterozygous for homo-heterothallism.  相似文献   
6.
We surveyed nine diallelic polymorphic sites on the Y chromosomes of 1,544 individuals from Africa, Asia, Europe, Oceania, and the New World. Phylogenetic analyses of these nine sites resulted in a tree for 10 distinct Y haplotypes with a coalescence time of approximately 150,000 years. The 10 haplotypes were unevenly distributed among human populations: 5 were restricted to a particular continent, 2 were shared between Africa and Europe, 1 was present only in the Old World, and 2 were found in all geographic regions surveyed. The ancestral haplotype was limited to African populations. Random permutation procedures revealed statistically significant patterns of geographical structuring of this paternal genetic variation. The results of a nested cladistic analysis indicated that these geographical associations arose through a combination of processes, including restricted, recurrent gene flow (isolation by distance) and range expansions. We inferred that one of the oldest events in the nested cladistic analysis was a range expansion out of Africa which resulted in the complete replacement of Y chromosomes throughout the Old World, a finding consistent with many versions of the Out of Africa Replacement Model. A second and more recent range expansion brought Asian Y chromosomes back to Africa without replacing the indigenous African male gene pool. Thus, the previously observed high levels of Y chromosomal genetic diversity in Africa may be due in part to bidirectional population movements. Finally, a comparison of our results with those from nested cladistic analyses of human mtDNA and beta-globin data revealed different patterns of inferences for males and females concerning the relative roles of population history (range expansions) and population structure (recurrent gene flow), thereby adding a new sex-specific component to models of human evolution.   相似文献   
7.

Background  

Post-translational protein modification with ubiquitin, or ubiquitylation, is one of the hottest topics in a modern biology due to a dramatic impact on diverse metabolic pathways and involvement in pathogenesis of severe human diseases. A great number of eukaryotic proteins was found to be ubiquitylated. However, data about particular ubiquitylated proteins are rather disembodied.  相似文献   
8.
Little is known about the effect of exercise training on the expression of adiponectin receptor genes in peripheral blood mononuclear cells (PBMCs). In this study, we investigated the effects of aerobic training on the expression of AdipoR1 and AidpoR2 mRNAs in PBMCs, whole body insulin sensitivity, and circulating adiponectins in men. Thirty young men were randomly assigned to either a control (n=15) or an exercise (n=15) group. Subjects assigned to the exercise group underwent a 12-week jogging and/or running programme on a motor-driven treadmill at an intensity of 60%-75% of the age-based maximum heart rate with duration of 40 minutes per session and a frequency of 5 days per week. Two-way mixed ANOVA with repeated measures was used to test any significant time-by-group interaction effects for the measured variables at p=0.05. We found significant time-by-group interaction effects for waist circumference (p=0.001), VO2max (p<0.001), fasting insulin (p=0.016), homeostasis model assessment for insulin resistance (HOMA-IR) (p=0.010), area under the curve (AUC) for insulin response during the 75-g oral glucose tolerance test (p=0.002), high-molecular weight (HMW) adiponectin (p=0.016), and the PBMC mRNA levels of AdipoR1 (p<0.001) and AdipoR2 (p=0.001). The exercise group had significantly increased mRNA levels of AdipoR1 and AdipoR2 in PBMCs, along with increased whole body insulin sensitivity and HMW adiponectin, decreased waist circumference, and increased VO2max compared with the control group. In summary, the current findings suggest that exercise training modulates the expression of AdipoR1 and AdipoR2 mRNAs in PBMCs, implying that manipulation of the expression of these genes could be a potential surrogate for lifestyle intervention-mediated improvements of whole body insulin sensitivity and glucose homeostasis.  相似文献   
9.
Genes of β-mannosidase 97 kDa, GH family 2 (bMann9), β-mannanase 48 kDa, GH family 5 (bMan2), and α-galactosidase 60 kDa, GH family 27 (aGal1) encoding galactomannan-degrading glycoside hydrolases of Myceliophthora thermophila C1 were successfully cloned, and the recombinant enzymes were purified to homogeneity and characterized. bMann9 displays only exo-mannosidase activity, the K m and k cat values are 0.4 mM and 15 sec?1 for p-nitrophenyl-β-D-mannopyranoside, and the optimal pH and temperature are 5.3 and 40°C, respectively. bMann2 is active towards galac-tomannans (GM) of various structures. The K m and k cat values are 1.3 mg/ml and 67 sec?1 for GM carob, and the optimal pH and temperature are 5.2 and 69°C, respectively. aGal1 is active towards p-nitrophenyl-α-D-galactopyranoside (PNPG) as well as GM of various structures. The K m and k cat values are 0.08 mM and 35 sec?1 for PNPG, and the optimal pH and temperature are 5.0 and 60°C, respectively.  相似文献   
10.
The species Mycobacterium avium includes several subspecies representing highly specialized avian and mammalian pathogens, non-obligatory pathogens of immune compromised humans and saprophitic organisms. Recently obtained information concerning the diversity of M. avium genomic structures not only clarified phylogenic relationships within this species, but began to shed light on the question of how such closely related microorganisms adapt to the occupation of distinct ecological niches. In this review we discuss specific features of M. avium genetic composition, as well as genetic and molecular aspects of M. avium hominissuis (MAH)-triggered disease pathogenesis, including virulence, penetration, immune response manipulation and host genetic control.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号