首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   308篇
  免费   32篇
  340篇
  2024年   2篇
  2022年   5篇
  2021年   3篇
  2020年   4篇
  2019年   3篇
  2018年   6篇
  2017年   7篇
  2016年   16篇
  2015年   34篇
  2014年   21篇
  2013年   24篇
  2012年   22篇
  2011年   22篇
  2010年   9篇
  2009年   23篇
  2008年   24篇
  2007年   14篇
  2006年   16篇
  2005年   10篇
  2004年   9篇
  2003年   11篇
  2002年   9篇
  2001年   5篇
  2000年   4篇
  1999年   8篇
  1998年   4篇
  1997年   2篇
  1996年   1篇
  1994年   3篇
  1993年   1篇
  1992年   4篇
  1991年   1篇
  1990年   1篇
  1987年   1篇
  1984年   2篇
  1983年   2篇
  1982年   2篇
  1981年   2篇
  1980年   1篇
  1975年   1篇
  1973年   1篇
排序方式: 共有340条查询结果,搜索用时 15 毫秒
91.
S Shin  E Park  DH Lee  KJ Lee  JH Heo  HS Nam 《PloS one》2012,7(7):e41544

Background

The pronator drift test is widely used to detect mild arm weakness. We developed an application that runs on a handheld device to objectify the pronator drift test and investigated its feasibility in stroke patients.

Methods

The iPronator application, which uses the built-in accelerometer in handheld devices, was developed. We enrolled acute ischemic stroke patients (n = 10) with mild arm weakness and healthy controls (n = 10) to validate the iPronator. In addition to conventional neurological examinations, the degree of average, maximum, and oscillation in drift and pronation were measured and compared using the iPronator. Follow-up tests using the iPronator were also conducted in the patient group one week later.

Results

There was a strong correlation between the average degree of pronation and drift measured by the iPronator (r = 0.741, p<0.001). The degrees of average and maximum in pronation were greater in the patient group than in the control group [in average, 28.9°, interquartile range (IQR) 18.7–40.3 vs. 3.8° (IQR 0.3–7.5), p<0.001], in maximum, 33.0° (IQR 24.0–52.1) vs. 6.2° (IQR 1.4–9.4), p<0.001]. The degree of oscillation in pronation was not different between the groups (p = 0.166). In drift, the degrees of average, maximum, and oscillation were greater in the patient group. In stroke patients, a follow-up study at one week revealed improvements in the degrees of pronation and drift compared with baseline parameters.

Conclusions

The iPronator can reliably detect mild arm weakness of stroke patients and was also useful in detecting functional recovery for one week in patients with acute stroke.  相似文献   
92.
Immunologic abnormalities of natural killer (NK) cells and T cells play a role in the pathogenesis of systemic lupus erythematosus (SLE). CD161 is expressed on most of the NK cells and on some T cells. The quantities of CD161-expressing cells and expression levels of CD161 were analyzed in T cells and NK cells from patients with SLE compared with normal controls. The expression of CD161 on NK cells, NKT cells, CD4+ T cells, and CD8+ T cells in peripheral blood from patients with inactive SLE and active SLE, and from the normal controls group were determined using flow cytometry. The frequency and expression level of CD161 in the lymphocyte subsets and its relationship with the quantity of regulatory T cells, anti-double stranded DNA antibody, and the titer of antinuclear antibody were evaluated. Both the percentages of the CD161+ subpopulation and the mean fluorescence intensities (MFIs) of CD161 in CD8+ T cells and NKT cells decreased significantly in SLE patients compared with normal controls (P < .001). The CD161 expression in CD8+ T cells and NKT cells also decreased in the anti-dsDNA (+) group (P < .05). The counts of Treg cells were lower in SLE patients and were weakly correlated with the percentage of the CD161 subpopulation (r = 0.229, P = .016) and the MFIs of CD161 expression in CD8+ T cells (r = .232, P = .014). The frequencies and levels of CD161 expression on CD8+ T cells and NKT cells were reduced in SLE patients, suggesting that an abnormality of these cells was related to the pathogenesis of SLE.  相似文献   
93.
We describe the construction of a reference genetic linkage map for the Brassica A genome, which will form the backbone for anchoring sequence contigs for the Multinational Brassica rapa Genome Sequencing Project. Seventy-eight doubled haploid lines derived from anther culture of the F1 of a cross between two diverse Chinese cabbage (B. rapa ssp. pekinensis) inbred lines, ‘Chiifu-401-42’ (C) and ‘Kenshin-402-43’ (K) were used to construct the map. The map comprises a total of 556 markers, including 278 AFLP, 235 SSR, 25 RAPD and 18 ESTP, STS and CAPS markers. Ten linkage groups were identified and designated as R1–R10 through alignment and orientation using SSR markers in common with existing B. napus reference linkage maps. The total length of the linkage map was 1,182 cM with an average interval of 2.83 cM between adjacent loci. The length of linkage groups ranged from 81 to 161 cM for R04 and R06, respectively. The use of 235 SSR markers allowed us to align the A-genome chromosomes of B. napus with those of B. rapa ssp. pekinensis. The development of this map is vital to the integration of genome sequence and genetic information and will enable the international research community to share resources and data for the improvement of B. rapa and other cultivated Brassica species. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   
94.
The mechanism by which extracellular metabolites, including redox mediators and quorum-sensing signaling molecules, traffic through the extracellular matrix of biofilms is poorly explored. We hypothesize that functional amyloids, abundant in natural biofilms and possessing hydrophobic domains, retain these metabolites. Using surface plasmon resonance, we demonstrate that the quorum-sensing (QS) molecules, 2-heptyl-3-hydroxy-4(1H)-quinolone and N-(3-oxododecanoyl)-l-homoserine lactone, and the redox mediator pyocyanin bind with transient affinity to functional amyloids from Pseudomonas (Fap). Their high hydrophobicity predisposes them to signal-amyloid interactions, but specific interactions also play a role. Transient interactions allow for rapid association and dissociation kinetics, which make the QS molecules bioavailable and at the same time secure within the extracellular matrix as a consequence of serial bindings. Retention of the QS molecules was confirmed using Pseudomonas aeruginosa PAO1-based 2-heptyl-3-hydroxy-4(1H)-quinolone and N-(3-oxododecanoyl)-l-homoserine lactone reporter assays, showing that Fap fibrils pretreated with the QS molecules activate the reporters even after sequential washes. Pyocyanin retention was validated by electrochemical analysis of pyocyanin-pretreated Fap fibrils subjected to the same washing process. Results suggest that QS molecule-amyloid interactions are probably important in the turbulent environments commonly encountered in natural habitats.  相似文献   
95.
Neisseria meningitidis is a major global pathogen causing invasive disease with a mortality of 5–10%. Most disease in developed countries is caused by serogroup B infection, against which there is no universal vaccine. Opacity-associated adhesin (Opa) proteins are major meningococcal outer membrane proteins, which have shown recent promise as a potential novel vaccine. Immunisation of mice with different Opa variants elicited high levels of meningococcal-specific bactericidal antibodies, demonstrating proof in principle for this approach. Opa proteins are critical in meningococcal pathogenesis, mediating bacterial adherence to host cells, and modulating human cellular immunity via interactions with T cells and neutrophils, although there are conflicting data regarding their effects on CD4+ T cells. We constructed Opa-positive and Opa-negative meningococcal strains to allow further evaluation of Opa as a vaccine component. All four opa genes from N. meningitidis strain H44/76 were sequentially disrupted to construct all possible combinations of N. meningitidis strains deficient in one, two, three, or all four opa genes. The transformations demonstrated that homologous recombination of exogenous DNA into the meningococcal chromosome can occur with as little as 80 bp, and that minor sequence differences are permissible. Anti-Opa bactericidal antibody responses following immunisation of mice with recombinant Opa were specific to the Opa variant used in immunisation. No immunomodulatory effects were observed when Opa was contained within meningococcal outer membrane vesicles (OMVs), compared to Opa-negative OMVs. These observations support the incorporation of Opa in meningococcal vaccines.  相似文献   
96.
97.
98.
Huh JH  Bauer MJ  Hsieh TF  Fischer RL 《Cell》2008,132(5):735-744
Gene imprinting, the differential expression of maternal and paternal alleles, independently evolved in mammals and in flowering plants. A unique feature of flowering plants is a double-fertilization event in which the sperm fertilize not only the egg, which forms the embryo, but also the central cell, which develops into the endosperm (an embryo-supporting tissue). The distinctive mechanisms of gene imprinting in the endosperm, which involve DNA demethylation and histone methylation, begin in the central cell and sperm prior to fertilization. Flowering plants might have coevolved double fertilization and imprinting to prevent parthenogenetic development of the endosperm.  相似文献   
99.
100.
The composition, biomass and cell size of phytoplankton taxonomicgroups were determined in the Hauraki Gulf and adjacent shelfof north-eastern New Zealand. In early spring, on the innershelf, over-winter mixing and upwelling supported a bloom dominatedby large, chain-forming diatoms in a moderately turbulent watercolumn. The bloom declined in late spring because of nutrientlimitation, and the assemblage evolved initially toward smalldiatoms, and eventually to co-occurrence of dinoflagellates,small nanoflagellates and picophytoplankton in early and latesummer. Mid- to outer-shelf biomass was much lower than inshore,and was dominated by small or motile taxa which were probablylimited by grazing and light. In early summer, strong upwellingdisplaced inner shelf phytoplankton to beyond the shelf edge,whilst enriching the shelf with nutrients. However, shelf phytoplanktonbiomass increased only after the relaxation of upwelling. TheHauraki Gulf was strongly stratified from early spring throughlate summer. The flora were seasonally less variable than onthe shelf, with a thecate dinoflagellate-dominated flora inearly spring, replaced post-bloom by the co-occurrence of presumablylow-nutrient-adapted autotrophic and/or heterotrophic dinoflagellates(most of which were non-thecate, and some toxic), nanoflagellatesand picophytoplankton. The succession in floristics was consistentwith a change from an autotrophic toward a heterotrophic ecosystemfrom spring to summer. Implications for secondary production,and vertical and lateral organic carbon export on the shelf,are discussed.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号