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11.
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Neeraja Vajrala Luis A. Sayavedra-Soto Peter J. Bottomley Daniel J. Arp 《Archives of microbiology》2010,192(11):899-908
Nitrosomonas europaea has a single three-gene operon (nitABC) encoding an iron ABC transporter system (NitABC). Phylogenetic analysis clustered the subunit NitB with Fe3+-ABC transporter permease components from other organisms. The N.
europaea strain deficient in nitB (nitB::kan) grew well in either Fe-replete or Fe-limited media and in Fe-limited medium containing the catecholate-type siderophore,
enterobactin or the citrate-based dihydroxamate-type siderophore, aerobactin. However, the nitB::kan mutant strain was unable to grow in Fe-limited media containing either the hydroxamate-type siderophores, ferrioxamine and
ferrichrome or the mixed-chelating type siderophore, pyoverdine. Exposure of N. europaea cells to a ferrichrome analog coupled to the fluorescent moiety naphthalic diimide (Fhu-NI) led to increase in fluorescence
in the wild type but not in nitB::kan mutant cells. Spheroplasts prepared from N.
europaea wild type exposed to Fhu-NI analog retained the fluorescence, while spheroplasts of the nitB::kan mutant were not fluorescent. NitABC transports intact Fe3+-ferrichrome complex into the cytoplasm and is an atypical ABC type iron transporter for Fe3+ bound to ferrioxamine, ferrichrome or pyoverdine siderophores into the cytoplasm. The mechanisms to transport iron in either
the Fe3+ or Fe2+ forms or Fe3+ associated with enterobactin or aerobactin siderophores into the cell across the cytoplasmic membrane are as yet undetermined. 相似文献
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Jesudason R Sato S Parameswaran H Araujo AD Majumdar A Allen PG Bartolák-Suki E Suki B 《Biophysical journal》2010,99(9):3076-3083
Many fundamental cellular and extracellular processes in the body are mediated by enzymes. At the single molecule level, enzyme activity is influenced by mechanical forces. However, the effects of mechanical forces on the kinetics of enzymatic reactions in complex tissues with intact extracellular matrix (ECM) have not been identified. Here we report that physiologically relevant macroscopic mechanical forces modify enzyme activity at the molecular level in the ECM of the lung parenchyma. Porcine pancreatic elastase (PPE), which binds to and digests elastin, was fluorescently conjugated (f-PPE) and fluorescent recovery after photobleach was used to evaluate the binding kinetics of f-PPE in the alveolar walls of normal mouse lungs. Fluorescent recovery after photobleach indicated that the dissociation rate constant (koff) for f-PPE was significantly larger in stretched than in relaxed alveolar walls with a linear relation between koff and macroscopic strain. Using a network model of the parenchyma, a linear relation was also found between koff and microscopic strain on elastin fibers. Further, the binding pattern of f-PPE suggested that binding sites on elastin unfold with strain. The increased overall reaction rate also resulted in stronger structural breakdown at the level of alveolar walls, as well as accelerated decay of stiffness and decreased failure stress of the ECM at the macroscopic scale. These results suggest an important role for the coupling between mechanical forces and enzyme activity in ECM breakdown and remodeling in development, and during diseases such as pulmonary emphysema or vascular aneurysm. Our findings may also have broader implications because in vivo, enzyme activity in nearly all cellular and extracellular processes takes place in the presence of mechanical forces. 相似文献
15.
Namrata Singh Trang T. M. Dang Georgina V. Vergara Dev Mani Pandey Darlene Sanchez C. N. Neeraja Endang M. Septiningsih Merlyn Mendioro Evelyn Mae Tecson-Mendoza Abdelbagi M. Ismail David J. Mackill Sigrid Heuer 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2010,121(8):1441-1453
16.
Poornima Parameswaran Ella Sklan Courtney Wilkins Trever Burgon Melanie A. Samuel Rui Lu K. Mark Ansel Vigo Heissmeyer Shirit Einav William Jackson Tammy Doukas Suman Paranjape Charlotta Polacek Flavia Barreto dos Santos Roxana Jalili Farbod Babrzadeh Baback Gharizadeh Dirk Grimm Mark Kay Satoshi Koike Peter Sarnow Mostafa Ronaghi Shou-Wei Ding Eva Harris Marie Chow Michael S. Diamond Karla Kirkegaard Jeffrey S. Glenn Andrew Z. Fire 《PLoS pathogens》2010,6(2)
We have used multiplexed high-throughput sequencing to characterize changes in small RNA populations that occur during viral infection in animal cells. Small RNA-based mechanisms such as RNA interference (RNAi) have been shown in plant and invertebrate systems to play a key role in host responses to viral infection. Although homologs of the key RNAi effector pathways are present in mammalian cells, and can launch an RNAi-mediated degradation of experimentally targeted mRNAs, any role for such responses in mammalian host-virus interactions remains to be characterized. Six different viruses were examined in 41 experimentally susceptible and resistant host systems. We identified virus-derived small RNAs (vsRNAs) from all six viruses, with total abundance varying from “vanishingly rare” (less than 0.1% of cellular small RNA) to highly abundant (comparable to abundant micro-RNAs “miRNAs”). In addition to the appearance of vsRNAs during infection, we saw a number of specific changes in host miRNA profiles. For several infection models investigated in more detail, the RNAi and Interferon pathways modulated the abundance of vsRNAs. We also found evidence for populations of vsRNAs that exist as duplexed siRNAs with zero to three nucleotide 3′ overhangs. Using populations of cells carrying a Hepatitis C replicon, we observed strand-selective loading of siRNAs onto Argonaute complexes. These experiments define vsRNAs as one possible component of the interplay between animal viruses and their hosts. 相似文献
17.
CD101 surface expression discriminates potency among murine FoxP3+ regulatory T cells 总被引:2,自引:0,他引:2
Fernandez I Zeiser R Karsunky H Kambham N Beilhack A Soderstrom K Negrin RS Engleman E 《Journal of immunology (Baltimore, Md. : 1950)》2007,179(5):2808-2814
CD4+CD25+FoxP3+ regulatory T cells (Treg) have been shown to be protective in animal models of autoimmunity and acute graft-vs-host disease. However, owing to the functional heterogeneity among CD4+CD25+ T cells, surface markers expressed selectively on functionally active Treg would be useful for purposes of identifying and isolating such cells. We generated a rabbit mAb against murine CD101, a transmembrane glycoprotein involved in T cell activation. Among freshly isolated T cells, CD101 was detected on 25-30% of CD4+CD25+ Treg and approximately 20% of conventional memory T cells. CD101(high) Treg displayed greater in vitro suppression of alloantigen-driven T cell proliferation as compared with CD101(low) Treg. In a model of graft-vs-host disease induced by allogeneic bone marrow transplantation in vivo bioluminescence imaging demonstrated reduced expansion of donor-derived luciferase-labeled conventional T cells in mice treated with CD101(high) Treg, compared with CD101(low) Treg. Moreover, treatment with CD101(high) Treg resulted in improved survival, reduced proinflammatory cytokine levels and reduced end organ damage. Among the CD101(high) Treg all of the in vivo suppressor activity was contained within the CD62L(high) subpopulation. We conclude that CD101 expression distinguishes murine Treg with potent suppressor activity. 相似文献
18.
The present study was directed to the production of N-acetyl-D-glucosamine using endochitinase and chitobiase from fungal cultures in solid culturing. Fifteen fungal strains were evaluated for endochitinase and chitobiase production under solid-state fermentation using agro-industrial residues, of which Penicillium aculeatum NRRL 2129 showed maximum endochitinase activity whereas Trichoderma harzianum TUBF 927 showed maximum chitobiase activity. Eleven substrates, alone and in combination with chitin, were evaluated for the enzyme production. Optimization of physico-chemical parameters such as incubation period and initial moisture content, and nutritional parameters such as chitin source, inorganic and organic nitrogen sources, were carried out. Optimization resulted in more than 3-fold increase in endochitinase production (from 3.5 to 12.53 U/g dry weight of substrate) and about 1.5-fold increase in chitobiase production (from 1.6 to 2.25 U/g dry weight of substrate). Studies on the degradation of colloidal chitin to N-acetyl-D-glucosamine showed improved efficiency when endochitinase and chitobiase were used in combination. 相似文献
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CH Balachiranjeevi Naik S. Bhaskar V. Abhilash S. Akanksha B. C. Viraktamath M. S. Madhav A. S. Hariprasad G. S. Laha M. S. Prasad S. M. Balachandran C. N. Neeraja M. Satendra Kumar P. Senguttuvel K. B. Kemparaju V. P. Bhadana T. Ram G. Harika H. K. Mahadeva Swamy S. K. Hajira A. Yugander K. Pranathi M. Anila G. Rekha M. B. V. N. Kousik T. Dilip Kumar R. K. Swapnil Archana Giri R. M. Sundaram 《Molecular breeding : new strategies in plant improvement》2015,35(7):1-12