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101.
102.
Koskiniemi H Metsä-Ketelä M Dobritzsch D Kallio P Korhonen H Mäntsälä P Schneider G Niemi J 《Journal of molecular biology》2007,372(3):633-648
Angucyclines are aromatic polyketides produced in Streptomycetes via complex enzymatic biosynthetic pathways. PgaE and CabE from S. sp PGA64 and S. sp. H021 are two related homo-dimeric FAD and NADPH dependent aromatic hydroxylases involved in the early steps of the angucycline core modification. Here we report the three-dimensional structures of these two enzymes determined by X-ray crystallography using multiple anomalous diffraction and molecular replacement, respectively, to resolutions of 1.8 A and 2.7 A. The enzyme subunits are built up of three domains, a FAD binding domain, a domain involved in substrate binding and a C-terminal thioredoxin-like domain of unknown function. The structure analysis identifies PgaE and CabE as members of the para-hydroxybenzoate hydroxylase (pHBH) fold family of aromatic hydroxylases. In contrast to phenol hydroxylase and 3-hydroxybenzoate hydroxylase that utilize the C-terminal domain for dimer formation, this domain is not part of the subunit-subunit interface in PgaE and CabE. Instead, dimer assembly occurs through interactions of their FAD binding domains. FAD is bound non-covalently in the "in"-conformation. The active sites in the two enzymes differ significantly from those of other aromatic hydroxylases. The volumes of the active site are significantly larger, as expected in view of the voluminous tetracyclic angucycline substrates. The structures further suggest that substrate binding and catalysis may involve dynamic rearrangements of the middle domain relative to the other two domains. Site-directed mutagenesis studies of putative catalytic groups in the active site of PgaE argue against enzyme-catalyzed substrate deprotonation as a step in catalysis. This is in contrast to pHBH, where deprotonation/protonation of the substrate has been suggested as an essential part of the enzymatic mechanism. 相似文献
103.
G. J. King F. H. Alston L. M. Brown E. Chevreau K. M. Evans F. Dunemann J. Janse F. Laurens J. R. Lynn C. Maliepaard A. G. Manganaris P. Roche H. Schmidt S. Tartarini J. Verhaegh R. Vrielink 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1998,96(5):699-708
Apple scab, caused by the fungus Venturia inaequalis (Cke.) Wint., is an important disease in commercial apple production. A mapping population of 155 individuals, derived from
a cross between the apple varieties ‘Prima’ (resistant)בFiesta’ (susceptible), was scored for response to the disease in
replicated field and glasshouse trials throughout Europe. Twenty data sets were selected and cluster analysis was used to
form a consensus score for the population fitting a 1 : 1 segregation ratio of resistance:susceptibility. The progeny were
scored with molecular markers. A detailed map covering 54 cM of the ‘Prima’ linkage group containing the Vf gene for scab resistance was constructed using 24 molecular markers linked to the resistance gene. One isoenzyme marker (Pgm-1), six RFLP markers and 17 RAPD markers formed a linkage group with the consensus measure of resistance to scab. Four marker
bridges were established with the corresponding ‘Fiesta’ linkage group with additional markers (one isozyme, one RFLP, three
RAPD and one AFLP). A low chi-square value indicated a good fit of the marker ordering, which was in close agreement with
previously reported linkage positions for some of the markers and Vf. Differences were observed in the ability of different scoring methods to resolve susceptible and resistant classes. The
results obtained for the consensus classification of resistance to scab for the population may suggest the presence of virulent
inocula at some sites, which could overcome the Vf gene for resistance. The consequences of relying on individual scoring occasions for studying Vf scab resistance are discussed in the context of linkage analysis, conventional breeding selection, and marker-assisted selection.
Received: 23 July 1997 / Accepted: 31 October 1997 相似文献
104.
Manning L Laman M Edoni H Mueller I Karunajeewa HA Smith D Hwaiwhanje I Siba PM Davis TM 《PLoS neglected tropical diseases》2011,5(1):e932
Introduction
Subacute sclerosing panencephalitis (SSPE) is a late, rare and usually fatal complication of measles infection. Although a very high incidence of SSPE in Papua New Guinea (PNG) was first recognized 20 years ago, estimated measles vaccine coverage has remained at ≤70% since and a large measles epidemic occurred in 2002. We report a series of 22 SSPE cases presenting between November 2007 and July 2009 in Madang Province, PNG, including localized clusters with the highest ever reported annual incidence.Methodology/Principal Findings
As part of a prospective observational study of severe childhood illness at Modilon Hospital, the provincial referral center, children presenting with evidence of meningo-encephalitis were assessed in detail including lumbar puncture in most cases. A diagnosis of SSPE was based on clinical features and presence of measles-specific IgG in cerebrospinal fluid and/or plasma. The estimated annual SSPE incidence in Madang province was 54/million population aged <20 years, but four sub-districts had an incidence >100/million/year. The distribution of year of birth of the 22 children with SSPE closely matched the reported annual measles incidence in PNG, including a peak in 2002.Conclusions/Significance
SSPE follows measles infections in very young PNG children. Because PNG children have known low seroconversion rates to the first measles vaccine given at 6 months of age, efforts such as supplementary measles immunisation programs should continue in order to reduce the pool of non-immune people surrounding the youngest and most vulnerable members of PNG communities. 相似文献105.
Class I major histocompatibility complex (Mhc) cDNA clones were isolated from axolotl mRNA by polymerase chain reaction (PCR) and by screening a cDNA phage library. The
nucleotide and predicted amino acid sequences show definite similarities to the Mhc class Iα molecules of higher vertebrates.
Most of the amino acids in the peptide binding region that dock peptides at their N and C termini in mammals are conserved.
Several amino acids considered to be important for the interaction of β2-microglobulin with the Mhc α chain are also conserved in the axolotl sequence. The fact that axolotl class I A cDNAs are
ubiquitously expressed and highly polymorphic in the α1 and α2 domains suggests the classical nature of axolotl class I A
genes.
Received: 3 June 1996 / Revised: 14 October 1996 相似文献
106.
Nadhir Yousfi Benoist Pruvot Tatiana Lopez Lea Magadoux Nathalie Franche Laurent Pichon Fran?oise Salvadori Eric Solary Carmen Garrido Véronique Laurens Johanna Chluba 《PloS one》2015,10(3)
To investigate the effect of nitric oxide on tumor development, we established a rat tumor xenograft model in zebrafish embryos. The injected tumor cells formed masses in which nitric oxide production could be detected by the use of the cell-permeant DAF-FM-DA (diaminofluorophore 4-amino-5-methylamino-2’-7’-difluorofluorescein diacetate) and DAR-4M-AM (diaminorhodamine-4M). This method revealed that nitric oxide production could be co-localized with the tumor xenograft in 46% of the embryos. In 85% of these embryos, tumors were vascularized and blood vessels were observed on day 4 post injection. Furthermore, we demonstrated by qRT-PCR that the transplanted glioma cells highly expressed Nos2, Vegfa and Cyclin D1 mRNA. In the xenografted embryos we also found increased zebrafish vegfa expression. Glioma and zebrafish derived Vegfa and tumor Cyclin D1 expression could be down regulated by the nitric oxide scavenger 2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide or CPTIO. We conclude that even if there is a heterogeneous nitric oxide production by the xenografted glioma cells that impacts Vegfa and Cyclin D1 expression levels, our results suggest that reduction of nitric oxide levels by nitric oxide scavenging could be an efficient approach to treat glioma. 相似文献
107.
S. Ben Mahmoud M. Safa El Khawaja S. Poussier L. Maillard M.-H. Laurens L. Koessler S. Naoui H. Vespignani G. Karcher P.-Y. Marie 《Médecine Nucléaire》2008,32(5):291-299
IntroductionWhen ictal and interictal brain SPECT are reconstructed with filtered backprojection (FBP), the noise level of subtraction images is frequently high and requires the use of thresholding methods. The aim of this study was to compare the subtraction images for cerebral SPECT reconstructed either with FBP or with a 3D iterative reconstruction method (OSEM-3D).Material and methodsAfter optimisation of the reconstruction parameters on phantom, the subtraction SPECT images, which were obtained with FBP or with OSEM-3D and coregistered with MRI images, were analyzed in 15 patients with refractory temporal epilepsy.ResultsOn phantom and with the constrain of high enough spatial resolution (full width at half of maximum for a punctual source less than or equal to 11 mm) were reached using: (i) a Butterworth filter with a cut-off frequency of 0.4 Nyquist at order 6 for FBP and (ii) five iterations, 16 subsets and a 9 mm gaussian filter for OSEM-3D. On the subtraction images, which were obtained with these optimal parameters, the temporal foci from patients were smaller with OSEM-3D than with FBP (11 ± 6 cm3 versus 17 ± 10 cm3, P = 0.02), mean voxel activities were equivalent between the two methods within temporal foci (6.30 ± 3.13 counts versus 6.34 ± 4.93 counts) but these activities were dramatically reduced by OSEM-3D within background regions (0.02 ± 0.02 counts versus 0.19 ± 0.12 counts, P < 0.001).ConclusionFor the ictal–interictal subtraction SPECT images, which are obtained in patients with refractory temporal epilepsy, the use of an optimized OSEM-3D method leads to dramatically reduce the volume of temporal foci, as well as the background noise level, two properties that are likely to facilitate the detection and localisation of epilepsy foci. 相似文献
108.
Anna Rosanas-Urgell Enmoore Lin Laurens Manning Patricia Rarau Moses Laman Nicolas Senn Brian T. Grimberg Livingstone Tavul Danielle I. Stanisic Leanne J. Robinson John J. Aponte Elijah Dabod John C. Reeder Peter Siba Peter A. Zimmerman Timothy M. E. Davis Christopher L. King Pascal Michon Ivo Mueller 《PLoS medicine》2012,9(9)
Background
The erythrocyte polymorphism, Southeast Asian ovalocytosis (SAO) (which results from a 27-base pair deletion in the erythrocyte band 3 gene, SLC4A1Δ27) protects against cerebral malaria caused by Plasmodium falciparum; however, it is unknown whether this polymorphism also protects against P. vivax infection and disease.Methods and Findings
The association between SAO and P. vivax infection was examined through genotyping of 1,975 children enrolled in three independent epidemiological studies conducted in the Madang area of Papua New Guinea. SAO was associated with a statistically significant 46% reduction in the incidence of clinical P. vivax episodes (adjusted incidence rate ratio [IRR] = 0.54, 95% CI 0.40–0.72, p<0.0001) in a cohort of infants aged 3–21 months and a significant 52% reduction in P. vivax (blood-stage) reinfection diagnosed by PCR (95% CI 22–71, p = 0.003) and 55% by light microscopy (95% CI 13–77, p = 0.014), respectively, in a cohort of children aged 5–14 years. SAO was also associated with a reduction in risk of P. vivax parasitaemia in children 3–21 months (1,111/µl versus 636/µl, p = 0.011) and prevalence of P. vivax infections in children 15–21 months (odds ratio [OR] = 0.39, 95% CI 0.23–0.67, p = 0.001). In a case-control study of children aged 0.5–10 years, no child with SAO was found among 27 cases with severe P. vivax or mixed P. falciparum/P. vivax malaria (OR = 0, 95% CI 0–1.56, p = 0.11). SAO was associated with protection against severe P. falciparum malaria (OR = 0.38, 95% CI 0.15–0.87, p = 0.014) but no effect was seen on either the risk of acquiring blood-stage infections or uncomplicated episodes with P. falciparum. Although Duffy antigen receptor expression and function were not affected on SAO erythrocytes compared to non-SAO children, high level (>90% binding inhibition) P. vivax Duffy binding protein–specific binding inhibitory antibodies were observed significantly more often in sera from SAO than non-SAO children (SAO, 22.2%; non-SAO, 6.7%; p = 0.008).Conclusions
In three independent studies, we observed strong associations between SAO and protection against P. vivax malaria by a mechanism that is independent of the Duffy antigen. P. vivax malaria may have contributed to shaping the unique host genetic adaptations to malaria in Asian and Oceanic populations. Please see later in the article for the Editors'' Summary. 相似文献109.
Laurens M. Ni?ns Alexandra Cameron Ellen Van de Poel Margaret Ewen Werner B. F. Brouwer Richard Laing 《PLoS medicine》2010,7(8)
Background
Increasing attention is being paid to the affordability of medicines in low- and middle-income countries (LICs and MICs) where medicines are often highly priced in relation to income levels. The impoverishing effect of medicine purchases can be estimated by determining pre- and postpayment incomes, which are then compared to a poverty line. Here we estimate the impoverishing effects of four medicines in 16 LICs and MICs using the impoverishment method as a metric of affordability.Methods and Findings
Affordability was assessed in terms of the proportion of the population being pushed below US$1.25 or US$2 per day poverty levels because of the purchase of medicines. The prices of salbutamol 100 mcg/dose inhaler, glibenclamide 5 mg cap/tab, atenolol 50 mg cap/tab, and amoxicillin 250 mg cap/tab were obtained from facility-based surveys undertaken using a standard measurement methodology. The World Bank''s World Development Indicators provided household expenditure data and information on income distributions. In the countries studied, purchasing these medicines would impoverish large portions of the population (up to 86%). Originator brand products were less affordable than the lowest-priced generic equivalents. In the Philippines, for example, originator brand atenolol would push an additional 22% of the population below US$1.25 per day, whereas for the lowest priced generic equivalent this demographic shift is 7%. Given related prevalence figures, substantial numbers of people are affected by the unaffordability of medicines.Conclusions
Comparing medicine prices to available income in LICs and MICs shows that medicine purchases by individuals in those countries could lead to the impoverishment of large numbers of people. Action is needed to improve medicine affordability, such as promoting the use of quality assured, low-priced generics, and establishing health insurance systems. Please see later in the article for the Editors'' Summary 相似文献110.
Atrazine, bromacil, and diuron resistance in chlamydomonas: a single non-mendelian genetic locus controls the structure of the thylakoid binding site 总被引:3,自引:2,他引:3 下载免费PDF全文
A series of Chlamydomonas reinhardii mutants were selected for resistance to the herbicides atrazine, bromacil, and diuron. Four of these have reduced herbicide binding to the thylakoid membranes and show the non-Mendelian inheritance pattern characteristic of chloroplast genes. These mutants show a variety of selective alterations in binding of the three herbicides. These changes account for the observed patterns of in vivo cross-resistance. Analyses of chloroplast gene recombination indicate that these four mutations are in the same gene. Overall, the results suggest that this gene codes for a protein component of the herbicide binding site. One of the mutants has slow phototrophic growth and altered electron transport as has been observed in atrazine-resistant higher plant varieties, but the others are normal in these respects. The slow growth characteristic of this mutant seems to be the consequence of the same mutation which confers herbicide resistance.
The mutants isolated also include a large number which achieve resistance by some secondary mechanism. These are all nuclear gene mutations, and represent numerous loci. They also show a variety of patterns of cross-resistance, but the mechanisms behind them have not yet been investigated.
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