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11.
Rates and patterns of evolution in partial sequences of five mitochondrial
genes (cytochrome b, ATPase 6, NADH dehydrogenase subunit 5, tRNA(Glu), and
the control region) were compared among taxa in the passerine bird genera
Fringilla and Carduelis. Rates of divergence do not vary significantly
among genes, even in comparisons with the control region. Rate variation
among lineages is significant only for the control region and NADH
dehydrogenase subunit 5, and patterns of variation are consistent with the
expectations of neutral theory. Base composition is biased in all genes but
is stationary among lineages, and there is evidence for directional
mutation pressure only in the control region. Despite these similarities,
patterns of substitution differ among genes, consistent with alternative
regimes of selective constraint. Rates of nonsynonymous substitution are
higher in NADH dehydrogenase subunit 5 than in other protein-coding genes,
and transitions exist in elevated proportions relative to transversions.
Transitions appear to accumulate linearly with time in tRNA(Glu), and
despite exhibiting the highest overall rate of divergence among species,
there are no transversional changes in this gene. Finally, for resolving
phylogenetic relationships among Fringilla taxa, the combined
protein-coding data are broadly similar to those of the control region in
terms of phylogenetic informativeness and statistical support.
相似文献
12.
BiP and calreticulin form an abundant complex that is independent of endoplasmic reticulum stress 总被引:5,自引:1,他引:4 下载免费PDF全文
BiP is found in association with calreticulin, both in the presence and absence of endoplasmic reticulum stress. Although the BiP-calreticulin complex can be disrupted by ATP, several properties suggest that the calreticulin associated with BiP is neither unfolded nor partially or improperly folded. (1) The complex is stable in vivo and does not dissociate during 8 hr of chase. (2) When present in the complex, calreticulin masks epitopes at the C terminus of BiP that are not masked when BiP is bound to an assembly-defective protein. And (3) overproduction of calreticulin does not lead to the recruitment of more BiP into complexes with calreticulin. The BiP-calreticulin complex can be disrupted by low pH but not by divalent cation chelators. When the endoplasmic reticulum retention signal of BiP is removed, complex formation with calreticulin still occurs, and this explains the poor secretion of the truncated molecule. Gel filtration experiments showed that BiP and calreticulin are present in distinct high molecular weight complexes in which both molecules interact with each other. The possible functions of this complex are discussed. 相似文献
13.
Cecilia Ferndahl Nicklas Bonander Christel Logez Renaud Wagner Lena Gustafsson Christer Larsson Kristina Hedfalk Richard AJ Darby Roslyn M Bill 《Microbial cell factories》2010,9(1):47
Background
Recombinant protein production is universally employed as a solution to obtain the milligram to gram quantities of a given protein required for applications as diverse as structural genomics and biopharmaceutical manufacture. Yeast is a well-established recombinant host cell for these purposes. In this study we wanted to investigate whether our respiratory Saccharomyces cerevisiae strain, TM6*, could be used to enhance the productivity of recombinant proteins over that obtained from corresponding wild type, respiro-fermentative strains when cultured under the same laboratory conditions. 相似文献14.
15.
16.
Creager AN 《Studies in History and Philosophy of Science Part C: Studies in History and Philosophy of Biological and Biomedical Sciences》2007,38(1):159-190
The 1940s and 1950s were marked by intense debates over the origin of drug resistance in microbes. Bacteriologists had traditionally invoked the notions of 'training' and 'adaptation' to account for the ability of microbes to acquire new traits. As the field of bacterial genetics emerged, however, its participants rejected 'Lamarckian' views of microbial heredity, and offered statistical evidence that drug resistance resulted from the selection of random resistant mutants. Antibiotic resistance became a key issue among those disputing physiological (usually termed 'adaptationist') vs. genetic (mutation and selection) explanations of variation in bacteria. Postwar developments connected with the Lysenko affair gave this debate a new political valence. Proponents of the neo-Darwinian synthesis weighed in with support for the genetic theory. However, certain features of drug resistance seemed inexplicable by mutation and selection, particularly the phenomenon of 'multiple resistance'--the emergence of resistance in a single strain against several unrelated antibiotics. In the late 1950s, Tsutomu Watanabe and his collaborators solved this puzzle by determining that resistance could be conferred by cytoplasmic resistance factors rather than chromosomal mutation. These R factors could carry resistance to many antibiotics and seemed able to promote their own dissemination in bacterial populations. In the end, the vindication of the genetic view of drug resistance was accompanied by a recasting of the 'gene' to include extrachromosomal hereditary units carried on viruses and plasmids. 相似文献
17.
Creager MS Izdebski T Brooks AE Lewis RV 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2011,159(3):219-224
Spider silk has been evolutionarily optimized for contextual mechanical performance over the last 400 Ma. Despite precisely balanced mechanical properties, which have yet to be reproduced, the underlying molecular architecture of major ampullate spider silk can be simplified being viewed as a versatile block copolymer. Four primary amino acid motifs: polyalanine, (GA)(n), GPGXX, and GGX (X = G,A,S,Q,L,Y) will be considered in this study. Although synthetic mimetics of many of these amino acid motifs have been produced in several biological systems, the source of spider silk's mechanical integrity remains elusive. Mechanical robustness may be a product not only of the amino acid structure but also of the tertiary structure of the silk. Historically, solid state nuclear magnetic resonance (ssNMR) has been used to reveal the crystalline structure of the polyalanine motif; however, limitations in amino acid labeling techniques have obscured the structures of the GGX and GPGXX motifs thought to be responsible for the structural mobility of spider silk. We describe the use of metabolic pathways to label tyrosine for the first time as well as to improve the labeling efficiency of proline. These improved labeling techniques will allow the previously unknown tertiary structures of major ampullate silk to be probed. 相似文献
18.
The Open Microscopy Environment (OME) Data Model and XML file: open tools for informatics and quantitative analysis in biological imaging 总被引:2,自引:0,他引:2
Goldberg IG Allan C Burel JM Creager D Falconi A Hochheiser H Johnston J Mellen J Sorger PK Swedlow JR 《Genome biology》2005,6(5):R47
The Open Microscopy Environment (OME) defines a data model and a software implementation to serve as an informatics framework for imaging in biological microscopy experiments, including representation of acquisition parameters, annotations and image analysis results. OME is designed to support high-content cell-based screening as well as traditional image analysis applications. The OME Data Model, expressed in Extensible Markup Language (XML) and realized in a traditional database, is both extensible and self-describing, allowing it to meet emerging imaging and analysis needs. 相似文献
19.
M Imboden A Nieters AJ Bircher M Brutsche N Becker M Wjst U Ackermann-Liebrich W Berger NM Probst-Hensch 《Clinical and molecular allergy : CMA》2006,4(1):1-9
Background
Avoidance of allergens is still recommended as the first and best way to prevent allergic illnesses and their comorbid diseases. Despite a variety of attempts there has been very limited success in the area of environmental control of allergic disease. Our objective was to identify a non-invasive, non-pharmacological method to reduce indoor allergen loads in atopic persons' homes and public environments. We employed a novel in vivo approach to examine the possibility of using aluminum sulfate to control environmental allergens.Methods
Fifty skin test reactive patients were simultaneously skin tested with conventional test materials and the actions of the protein/glycoprotein modifier, aluminum sulfate. Common allergens, dog, cat, dust mite, Alternaria, and cockroach were used in the study.Results
Skin test reactivity was significantly reduced by the modifier aluminum sulfate. Our studies demonstrate that the effects of histamine were not affected by the presence of aluminum sulfate. In fact, skin test reactivity was reduced independent of whether aluminum sulfate was present in the allergen test material or removed prior to testing, indicating that the allergens had in some way been inactivated.Conclusion
Aluminum sulfate was found to reduce the in vivo allergic reaction cascade induced by skin testing with common allergens. The exact mechanism is not clear but appears to involve the alteration of IgE-binding epitopes on the allergen. Our results indicate that it may be possible to diminish the allergenicity of an environment by application of the active agent aluminum sulfate, thus producing environmental control without complete removal of the allergen. 相似文献20.
Unusual growth pattern in the Frasnian alveolitids (Tabulata) from the Holy Cross Mountains (Poland)
Abstract: Growth periodicity is a phenomenon occurring in fossil and modern corals. The most apparent feature is growth banding, and environmental changes are broadly accepted as controls on this phenomenon. If environment controls the growth, then all corallites within a colony should repeat the same growth pattern, as individuals are clones and must have shared the same environment. A study on several species of Alveolitidae (Anthozoa, Tabulata) from the Late Devonian (Early Frasnian) of the Holy Cross Mountains (Poland) shows that the growth pattern varies between neighbouring individuals within the same corallum. This contradicts observations of closely related Favositida as demonstrated on Pachyfavosites sp. from the Givetian of Avesnois, France, where neighbouring individuals repeat the same pattern. Therefore, environmental control on growth rhythm in Alveolitidae can be excluded; the causes of differences between individuals remain unknown. 相似文献