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排序方式: 共有222条查询结果,搜索用时 78 毫秒
51.
Christophe Roos Meelis Kolmer Pirkko Mattila Risto Renkonen 《The Journal of biological chemistry》2002,277(5):3168-3175
The whole genome approach enables the characterization of all components of any given biological pathway. Moreover, it can help to uncover all the metabolic routes for any molecule. Here we have used the genome of Drosophila melanogaster to search for enzymes involved in the metabolism of fucosylated glycans. Our results suggest that in the fruit fly GDP-fucose, the donor for fucosyltransferase reactions, is formed exclusively via the de novo pathway from GDP-mannose through enzymatic reactions catalyzed by GDP-D-mannose 4,6-dehydratase (GMD) and GDP-4-keto-6-deoxy-D-mannose 3,5-epimerase/4-reductase (GMER, also known as FX in man). The Drosophila genome does not have orthologs for the salvage pathway enzymes, i.e. fucokinase and GDP-fucose pyrophosphorylase synthesizing GDP-fucose from fucose. In addition we identified two novel fucosyltransferases predicted to catalyze alpha1,3- and alpha1,6-specific linkages to the GlcNAc residues on glycans. No genes with the capacity to encode alpha1,2-specific fucosyltransferases were found. We also identified two novel genes coding for O-fucosyltransferases and a gene responsible for a fucosidase enzyme in the Drosophila genome. Finally, using the Drosophila CG4435 gene, we identified two novel human genes putatively coding for fucosyltransferases. This work can serve as a basis for further whole-genome approaches in mapping all possible glycosylation pathways and as a basic analysis leading to subsequent experimental studies to verify the predictions made in this work. 相似文献
52.
Nanoscale organization and dynamics of the siglec CD22 cooperate with the cytoskeleton in restraining BCR signalling
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Andreas Bruckbauer Pieta K Mattila Jennifer Müller Lars Nitschke Dennis Bray Facundo D Batista 《The EMBO journal》2016,35(3):258-280
Receptor organization and dynamics at the cell membrane are important factors of signal transduction regulation. Using super‐resolution microscopy and single‐particle tracking, we show how the negative coreceptor CD22 works with the cortical cytoskeleton in restraining BCR signalling. In naïve B cells, we found endogenous CD22 to be highly mobile and organized into nanodomains. The landscape of CD22 and its lateral diffusion were perturbed either in the absence of CD45 or when the CD22 lectin domain was mutated. To understand how a relatively low number of CD22 molecules can keep BCR signalling in check, we generated Brownian dynamic simulations and supported them with ex vivo experiments. This combined approach suggests that the inhibitory function of CD22 is influenced by its nanoscale organization and is ensured by its fast diffusion enabling a “global BCR surveillance” at the plasma membrane. 相似文献
53.
54.
T A Miettinen G Alfthan J K Huttunen J Pikkarainen V Naukkarinen S Mattila T Kumlin 《BMJ (Clinical research ed.)》1983,287(6391):517-519
A longitudinal case-control study of 33 patients with one or more risk factors for coronary heart disease and 64 controls showed that the serum selenium concentration (range 0.63-1.33 mumol/l (50-105 micrograms/l] was not associated with development of clinical manifestations of coronary heart disease during a follow up of five to seven years. The content of polyunsaturated fatty acids, especially eicosapentaenoic acid, in serum cholesterol esters and phospholipids was positively correlated with selenium concentration. As a low content of polyunsaturated fatty acids in serum lipids was an independent risk factor for coronary heart disease in these subjects it may be hypothesised that the high coronary risk in subjects with a very low serum selenium concentration (less than 0.57 mumol/l (less than 45 micrograms/l] might be due not to selenium deficiency but to the coexisting low concentrations of polyunsaturated fatty acids in serum. 相似文献
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56.
Muscle surfaces of pork were inoculated with a mixture of Yersinia enterocolitica and Staphylococcus aureus, and chicken muscle with Campylobacter jejuni or a mixture of Salmonella typhimurium and Staph. aureus. The surface growth at 20 degrees C was followed microscopically. Organisms grew as discrete colonies bound together by a glycocalyx which differed between bacterial species. On prolonged incubation colonies spread peripherally and tended to coalesce, while still retaining their colony structure. Staphylococcus aureus colonies were very small and remained so. The glycocalyx was considered critical in maintaining the dense populations of bacteria on the meat surfaces. 相似文献
57.
Microsatellite genetic distances between oceanic populations of the humpback whale (Megaptera novaeangliae) 总被引:1,自引:0,他引:1
Valsecchi E; Palsboll P; Hale P; Glockner-Ferrari D; Ferrari M; Clapham P; Larsen F; Mattila D; Sears R; Sigurjonsson J; Brown M; Corkeron P; Amos B 《Molecular biology and evolution》1997,14(4):355-362
Mitochondrial DNA haplotypes of humpback whales show strong segregation
between oceanic populations and between feeding grounds within oceans, but
this highly structured pattern does not exclude the possibility of
extensive nuclear gene flow. Here we present allele frequency data for four
microsatellite loci typed across samples from four major oceanic regions:
the North Atlantic (two mitochondrially distinct populations), the North
Pacific, and two widely separated Antarctic regions, East Australia and the
Antarctic Peninsula. Allelic diversity is a little greater in the two
Antarctic samples, probably indicating historically greater population
sizes. Population subdivision was examined using a wide range of measures,
including Fst, various alternative forms of Slatkin's Rst, Goldstein and
colleagues' delta mu, and a Monte Carlo approximation to Fisher's exact
test. The exact test revealed significant heterogeneity in all but one of
the pairwise comparisons between geographically adjacent populations,
including the comparison between the two North Atlantic populations,
suggesting that gene flow between oceans is minimal and that dispersal
patterns may sometimes be restricted even in the absence of obvious
barriers, such as land masses, warm water belts, and antitropical migration
behavior. The only comparison where heterogeneity was not detected was the
one between the two Antarctic population samples. It is unclear whether
failure to find a difference here reflects gene flow between the regions or
merely lack of statistical power arising from the small size of the
Antarctic Peninsula sample. Our comparison between measures of population
subdivision revealed major discrepancies between methods, with little
agreement about which populations were most and least separated. We suggest
that unbiased Rst (URst, see Goodman 1995) is currently the most reliable
statistic, probably because, unlike the other methods, it allows for
unequal sample sizes. However, in view of the fact that these alternative
measures often contradict one another, we urge caution in the use of
microsatellite data to quantify genetic distance.
相似文献
58.
59.
B cells form an essential part of the adaptive immune system by producing specific antibodies that can neutralize toxins and target infected or malignant cells for destruction. During B cell activation, a fundamental role is played by a specialized intercellular structure called the immunological synapse (IS). The IS serves as a platform for B cell recognition of foreign, often pathogenic, antigens on the surface of antigen‐presenting cells (APC). This recognition is elicited by highly specific B cell receptors (BCR) that subsequently trigger carefully orchestrated intracellular signaling cascades that lead to cell activation. Furthermore, antigen internalization, essential for full B cell activation and differentiation into antibody producing effector cells or memory cells, occurs in the IS. Recent developments especially in various imaging‐based methods have considerably advanced our understanding of the molecular control of B cell activation. Interestingly, the cellular cytoskeleton is emerging as a key player at several stages of B cell activation, including the initiation of receptor signaling. Here, we discuss the functions and molecular mechanisms of the IS and highlight the multifaceted role of the actin cytoskeleton in several aspects of B cell activation. 相似文献
60.
Tuomas Mattila Pekka Leskinen Sampo Soimakallio Susanna Sironen 《The International Journal of Life Cycle Assessment》2012,17(6):696-705