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排序方式: 共有220条查询结果,搜索用时 15 毫秒
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Josephine Herbst Annabel Girke Mohammad Reza Hajirezaei Guy Hanke Bernhard Grimm 《The Plant journal : for cell and molecular biology》2018,94(3):485-496
Chlorophyll is synthesized from activated glutamate in the tetrapyrrole biosynthesis pathway through at least 20 different enzymatic reactions. Among these, the MgProto monomethylester (MgProtoME) cyclase catalyzes the formation of a fifth isocyclic ring to tetrapyrroles to form protochlorophyllide. The enzyme consists of two proteins. The CHL27 protein is proposed to be the catalytic component, while LCAA/YCF54 likely acts as a scaffolding factor. In comparison to other reactions of chlorophyll biosynthesis, this enzymatic step lacks clear elucidation and it is hardly understood, how electrons are delivered for the NADPH‐dependent cyclization reaction. The present study intends to elucidate more precisely the role of LCAA/YCF54. Transgenic Arabidopsis lines with inactivated and overexpressed YCF54 reveal the mutual stability of YCF54 and CHL27. Among the YCF54‐interacting proteins, the plastidal ferredoxin‐NADPH reductase (FNR) was identified. We showed in N. tabacum and A. thaliana that a deficit of FNR1 or YCF54 caused MgProtoME accumulation, the substrate of the cyclase, and destabilization of the cyclase subunits. It is proposed that FNR serves as a potential donor for electrons required in the cyclase reaction and connects chlorophyll synthesis with photosynthetic activity. 相似文献
24.
Competitive inhibition of binding between radioiodine-labelled encephalitogenic basic protein from human myelin (125I-HEProt) and normal human alpha-2 macroglobulin and between 125I-HEProt and rabbit antiHEProt serum was used to study concentrated cerebrospinal fluid (CSF) under “blind” control for cross-reactivity with HEProt. Samples of CSF from patients meeting the standard criteria for definite MS and possible MS, and from patients with optic neuritis and “other” diagnoses were studied. CSF from patients in all four groups was shown to have an inhibitor cross-reactive with HEProt when studied by the 125I-HEProt/alpha-2 macroglobulin test, but the amount was significantly greater in the definite MS group than in the “other” group. Results of the two tests on CSF from MS patients correlated, suggesting that the tests were identifying the same inhibitor. It was concluded that CSF contains an inhibitor similar to HEProt and that the amount present in CSF could be a useful diagnostic marker of MS. 相似文献
25.
In six cases of congenital syphilis in newborn at Los Angeles County-USC Medical Center over a seven-month period the clinical findings fell into two categories related to the time of onset of symptoms. Infants ill in the nursery presented evidence of transplacental infection; infants who became ill later showed the “classic” findings of rash, rhinorrhea and pseudoparalysis.No single clinical symptom was present in all cases but all symptomatic infants had radiographic evidence of bone disease. Respiratory distress was present at the onset of symptoms in three of four infants with neonatal disease, and all three had evidence of interstitial pneumonia in chest radiographs.Serologic testing may be difficult to evaluate in the newborn period, but more recent and specific tests are helpful in diagnosis. Penicillin remains the drug of choice. The only death occurred at five hours of life in a premature infant. Growth and development in surviving infants appeared normal. 相似文献
26.
Claudia Olak Annabel Muenter J?rg Andr? Gerald Brezesinski 《Journal of peptide science》2008,14(4):510-517
The structure of the antimicrobial peptide NK-2 has been studied at the air-water interface and in different solutions using spectroscopic methods such as circular dichroism (CD) and infrared reflection absorption spectroscopy (IRRAS) as well as specular X-ray reflectivity (XR). NK-2 adopts an unordered structure in water, buffer, and in the presence of monomeric cationic and noncharged amphiphiles. However, it forms a stable alpha-helix in 2,2,2-trifluoroethanol (TFE) and in micellar solutions of anionic, cationic as well as nonionic amphiphiles, whereas only in sodium dodecyl sulfonate solutions the alpha-helical structure can also be found below the critical micellar concentration (cmc). The amphiphilic molecule NK-2 is surface active and forms a Gibbs monolayer at the air-buffer interface. In contrast, no adsorption was observed if NK-2 is dissolved in water. During the adsorption process in buffer solutions, NK-2 undergoes a conformational transition from random coil in bulk to alpha-helix at the interface. This change of the peptide's secondary structure is known to be associated with its antimicrobial activity. A comparison of the experimental IRRA spectra with the simulated spectra indicates that the adsorbed NK-2 alpha-helix lies flat at the interface. This is confirmed by XR measurements which show that the thickness of the NK-2 layer is approximately 17 A, which is the average diameter of a alpha-helix, indicating that only a monomolecular adsorption layer is formed. 相似文献
27.
Pena V Hothorn M Eberth A Kaschau N Parret A Gremer L Bonneau F Ahmadian MR Scheffzek K 《EMBO reports》2008,9(4):350-355
The brain-specific synaptic guanosine triphosphatase (GTPase)-activating protein (SynGAP) is important in synaptic plasticity. It shows dual specificity for the small guanine nucleotide-binding proteins Rap and Ras. Here, we show that RapGAP activity of SynGAP requires its C2 domain. In contrast to the isolated GAP domain, which does not show any detectable RapGAP activity, a fragment comprising the C2 and GAP domains (C2-GAP) stimulates the intrinsic GTPase reaction of Rap by approximately 1 x 10(4). The C2-GAP crystal structure, complemented by modelling and biochemical analyses, favours a concerted movement of the C2 domain towards the switch II region of Rap to assist in GTPase stimulation. Our data support a catalytic mechanism similar to that of canonical RasGAPs and distinct from the canonical RapGAPs. SynGAP presents the first example, to our knowledge, of a GAP that uses a second domain for catalytic activity, thus pointing to a new function of C2 domains. 相似文献
28.
Andreas Weihe Janina Apitz Frank Pohlheim Annabel Salinas-Hartwig Thomas Börner 《Molecular genetics and genomics : MGG》2009,282(6):587-593
Plastidial (pt) and mitochondrial (mt) genes usually show maternal inheritance. Non-Mendelian, biparental inheritance of plastids
was first described by Baur (Z Indukt Abstamm Vererbungslehre 1:330–351, 1909) for crosses between Pelargonium cultivars. We have analyzed the inheritance of pt and mtDNA by examining the progeny from reciprocal crosses of Pelargonium
zonale and P. inquinans using nucleotide sequence polymorphisms of selected pt and mt genes. Sequence analysis of the progeny revealed biparental
inheritance of both pt and mtDNA. Hybrid plants exhibited variegation: our data demonstrate that the inquinans chloroplasts, but not the zonale chloroplasts bleach out, presumably due to incompatibility of the former with the hybrid nuclear genome. Different distribution
of maternal and paternal sequences could be observed in different sectors of the same leaf, in different leaves of the same
plant, and in different plants indicating random segregation and sorting-out of maternal and paternal plastids and mitochondria
in the hybrids. The substantial transmission of both maternal and paternal mitochondria to the progeny turns Pelargonium into a particular interesting subject for studies on the inheritance, segregation and recombination of mt genes. 相似文献
29.
Burkitt Wright EM Spencer HL Daly SB Manson FD Zeef LA Urquhart J Zoppi N Bonshek R Tosounidis I Mohan M Madden C Dodds A Chandler KE Banka S Au L Clayton-Smith J Khan N Biesecker LG Wilson M Rohrbach M Colombi M Giunta C Black GC 《American journal of human genetics》2011,(6):50-777
Extreme corneal fragility and thinning, which have a high risk of catastrophic spontaneous rupture, are the cardinal features of brittle cornea syndrome (BCS), an autosomal-recessive generalized connective tissue disorder. Enucleation is frequently the only management option for this condition, resulting in blindness and psychosocial distress. Even when the cornea remains grossly intact, visual function could also be impaired by a high degree of myopia and keratoconus. Deafness is another common feature and results in combined sensory deprivation. Using autozygosity mapping, we identified mutations in PRDM5 in families with BCS. We demonstrate that regulation of expression of extracellular matrix components, particularly fibrillar collagens, by PRDM5 is a key molecular mechanism that underlies corneal fragility in BCS and controls normal corneal development and maintenance. ZNF469, encoding a zinc finger protein of hitherto undefined function, has been identified as a quantitative trait locus for central corneal thickness, and mutations in this gene have been demonstrated in Tunisian Jewish and Palestinian kindreds with BCS. We show that ZNF469 and PRDM5, two genes that when mutated cause BCS, participate in the same regulatory pathway. 相似文献
30.
Emma?M.M. Burkitt?Wright Helen?L. Spencer Sarah?B. Daly Forbes?D.C. Manson Leo?A.H. Zeef Jill Urquhart Nicoletta Zoppi Richard Bonshek Ioannis Tosounidis Meyyammai Mohan Colm Madden Annabel Dodds Kate?E. Chandler Siddharth Banka Leon Au Jill Clayton-Smith Naz Khan Leslie?G. Biesecker Meredith Wilson Marianne Rohrbach Marina Colombi Cecilia Giunta Graeme?C.M. Black 《American journal of human genetics》2011,89(2):346