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   233篇
  免费   25篇
  2021年   3篇
  2020年   4篇
  2019年   3篇
  2018年   7篇
  2017年   7篇
  2016年   5篇
  2015年   12篇
  2014年   8篇
  2013年   7篇
  2012年   15篇
  2011年   12篇
  2010年   14篇
  2009年   9篇
  2008年   13篇
  2007年   13篇
  2006年   17篇
  2005年   8篇
  2004年   10篇
  2003年   8篇
  2002年   3篇
  2001年   7篇
  2000年   2篇
  1999年   4篇
  1998年   7篇
  1997年   2篇
  1994年   3篇
  1992年   6篇
  1991年   7篇
  1990年   2篇
  1989年   2篇
  1987年   2篇
  1985年   3篇
  1984年   3篇
  1982年   4篇
  1981年   3篇
  1980年   2篇
  1979年   2篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1970年   1篇
  1969年   1篇
  1965年   2篇
  1959年   1篇
  1956年   1篇
  1951年   1篇
  1925年   1篇
  1924年   2篇
  1923年   1篇
排序方式: 共有258条查询结果,搜索用时 265 毫秒
51.
The records of 1,020 major facial fractures were reviewed, and it was found that the occurrence of life-threatening associated injuries was highly predictable on the basis of the pattern of facial fractures and the circumstances of the injury. Certain groups of patients have a high probability of associated serious injuries of the central nervous system, the trunk, or the extremities. Probably these patients should be primarily under the care of a surgeon who is capable of the diagnosis and emergency therapy of these associated injuries, as well as the facial injuries, so that appropriate priorities can be established and put in effect.  相似文献   
52.
53.
We review the history and current efforts to assess and improve health care in the United States. This process has involved a host of government agencies and commissions, professional organizations, insurance underwriters, corporations, and more recently, market forces. Traditional approaches to quality control have stressed case-by-case analysis and identifying outliers. Newer approaches include creating practice guidelines and profiles of hospitals and physicians. The joint goals of quality improvement and cost control can best be realized if institutions and practitioners embrace these new approaches and use them to enhance their performances.  相似文献   
54.
The detection of the activities of pathogen-encoded virulence factors by the innate immune system has emerged as a new paradigm of pathogen recognition. Much remains to be determined with regard to the molecular and cellular components contributing to this defense mechanism in mammals and importance during infection. Here, we reveal the central role of the IL-1β signaling axis and Gr1+ cells in controlling the Escherichia coli burden in the blood in response to the sensing of the Rho GTPase-activating toxin CNF1. Consistently, this innate immune response is abrogated in caspase-1/11-impaired mice or following the treatment of infected mice with an IL-1β antagonist. In vitro experiments further revealed the synergistic effects of CNF1 and LPS in promoting the maturation/secretion of IL-1β and establishing the roles of Rac, ASC and caspase-1 in this pathway. Furthermore, we found that the α-hemolysin toxin inhibits IL-1β secretion without affecting the recruitment of Gr1+ cells. Here, we report the first example of anti-virulence-triggered immunity counteracted by a pore-forming toxin during bacteremia.  相似文献   
55.
Hypokalemic periodic paralysis type 2 (hypoPP2) is an inherited skeletal muscle disorder caused by missense mutations in the SCN4A gene encoding the alpha subunit of the skeletal muscle Na+ channel (Nav1.4). All hypoPP2 mutations reported so far target an arginine residue of the voltage sensor S4 of domain II (R672/G/H/S). We identified a novel hypoPP2 mutation that neutralizes an arginine residue in DIII-S4 (R1132Q), and studied its functional consequences in HEK cells transfected with the human SCN4A cDNA. Whole-cell current recordings revealed an enhancement of both fast and slow inactivation, as well as a depolarizing shift of the activation curve. The unitary Na+ conductance remained normal in R1132Q and in R672S mutants, and cannot therefore account for the reduction of Na+ current presumed in hypoPP2. Altogether, our results provide a clear evidence for the role of R1132 in channel activation and inactivation, and confirm loss of function effects of hypoPP2 mutations leading to muscle hypoexcitability.  相似文献   
56.
Plant disjunctions have provided one of the most intriguing distribution patterns historically addressed by biogeographers. Carex sect. Spirostachyae (Cyperaceae) displays an interesting pattern of disjunction to evaluate these scenarios, with species occurring in the main continental landmasses and in oceanic islands of the two hemispheres. Internal transcribed spacer and 5'-trnK intron plastid gene sequences were analyzed to determine (1) the times of diversification using penalized likelihood, and (2) reconstructions of the regions using maximum likelihood and Bayesian approaches of origin of sect. Spirostachyae and internal main lineages. The times for the diversification of sect. Spirostachyae are dated to between the end of the Eocene and the Oligocene, whereas the two main lineages are dated to between the end of the Oligocene and the beginning of Miocene. The phylogenetic analyses reveal a Mediterranean-Eurasian center of differentiation for sect. Spirostachyae and subsection Spirostachyae, whereas no clear, single ancestral area could be inferred for subsection Elatae. Both long-distance dispersal and ecological vicariance appear to have been involved in the evolutionary history of the disjunct distribution of the main lineages of sect. Spirostachyae. These organisms appear to have a special ability to colonize remote areas (through transoceanic and interhemispherical colonizations), but special long-distance dispersal mechanisms are not evident.  相似文献   
57.
Oligomeris linifolia constitutes one of the few examples of intercontinental disjunctions at the species level between the arid regions of the Old World and SW North America. The status of the American populations has been obscure, with some authors considering the populations to be introduced, whereas others believe them to be native. To clarify these conflicting opinions, we performed phylogeographic analyses using nuclear ribosomal ITS and plastid trnL-F and rps16 sequences to infer the origin of the disjunct American populations. Two independent molecular clock approaches based on ITS and cpDNA sequences (rbcL, matK, trnL-F) were used to estimate a divergence time of O. linifolia. Low levels of sequence divergence and estimates of relatively recent splits of Oligomeris lineages disagree with the vicariance hypotheses traditionally suggested to account for New-Old World disjunctions. In addition, significant genetic differentiation of American populations does not indicate a recent anthropogenic introduction. Morphological uniformity and the sharing of haplotypes between disjunct populations, together with the molecular clock results, suggest that a long-distance dispersal event from the Old Word to SW North America may have taken place during the Quaternary, in spite of limited dispersal mechanisms in Oligomeris.  相似文献   
58.
The subgenus Xiphium is one of the six infrageneric divisions of the genus Iris. Chromosome numbers of six of the seven Xiphium species are known. Here the aim was to infer genetic and phylogenetic relationships based on chromosome numbers, chromosome markers and plastid sequences. Chromosomal locations of 5S and 45S rDNA loci were determined in 19 populations of the 7 species by fluorescence in situ hybridization (FISH). Additionally, the trnLtrnF plastid spacer was sequenced and a phylogenetic analysis performed. Based on chromosome markers, subgenus Xiphium species were classified into four groups that differed in the number and locations of both types of nrDNA: (1) I. tingitana (2n = 28), I. filifolia (2n = 30, 34) and I. xiphium (2n = 34), (2) I. juncea (2n = 32) and I. boissieri (2n = 36), (3) I. serotina (2n = 34) and (4) I. latifolia (2n = 42). Although the trnLtrnF phylogeny was not fully resolved, the sequence analysis showed a well-supported subgroup of I. filifolia, I. tingitana and I. xiphium, as well as I. juncea. FISH physical maps of the Iris subgenus Xiphium taxa are species dependent. I. filifolia, I. tingitana and I. xiphium are very closely related species and share cytogenetic characteristics. Disploidy appears to have been central in the evolution of this subgenus, given a series of chromosome numbers (2n = 28, 30, 32, 34, 36, 42) and our phylogenetic results. Clear differences were found among European and African populations of I. filifolia. A different taxonomic treatment of I. filifolia is supported for populations on both sides of the Strait of Gibraltar.  相似文献   
59.

Introduction

The human monoclonal antibody adalimumab is known to induce an anti-globulin response in some adalimumab-treated patients. Antibodies against adalimumab (AAA) are associated with non-response to treatment. Immunoglobulins, such as adalimumab, carry allotypes which represent slight differences in the amino acid sequences of the constant chains of an IgG molecule. Immunoglobulins with particular IgG (Gm) allotypes are racially distributed and could be immunogenic for individuals who do not express these allotypes. Therefore, we investigated whether a mismatch in IgG allotypes between adalimumab and IgG in adalimumab-treated patients is associated with the development of AAA.

Methods

This cohort study consisted of 250 adalimumab-treated rheumatoid arthritis (RA) patients. IgG allotypes were determined for adalimumab and for all patients. Anti-idiotype antibodies against adalimumab were measured with a regular radio immunoassay (RIA), and a newly developed bridging enzyme linked immunosorbent assay (ELISA) was used to measure anti-allotype antibodies against adalimumab. The association between AAA and the G1m3 and the G1m17 allotypes was determined. For differences between groups we used the independent or paired samples t-test, Mann-Whitney test or Chi square/Fisher's exact test as appropriate. To investigate the influence of confounders on the presence or absence of AAA a multiple logistic regression-analysis was used.

Results

Adalimumab carries the G1m17 allotype. No anti-allotype antibodies against adalimumab were detected. Thirty-nine out of 249 patients had anti-idiotype antibodies against adalimumab (16%). IgG allotypes of RA patients were associated with the frequency of AAA: patients homozygous for G1m17 had the highest frequency of AAA (41%), patients homozygous for G1m3 the lowest frequency (10%), and heterozygous patients' AAA frequency was 14% (P = 0.0001).

Conclusions

An allotype mismatch between adalimumab and IgG in adalimumab-treated patients did not lead to a higher frequency of AAA. On the contrary, patients who carried the same IgG allotype as present on the adalimumab IgG molecule, had the highest frequency of anti-adalimumab antibodies compared to patients whose IgG allotype differed from adalimumab. This suggests that the allotype of adalimumab may not be highly immunogenic. Furthermore, patients carrying the G1m17-allotype might be more prone to antibody responses.  相似文献   
60.

Background  

The identification of biologically interesting genes in a temporal expression profiling dataset is challenging and complicated by high levels of experimental noise. Most statistical methods used in the literature do not fully exploit the temporal ordering in the dataset and are not suited to the case where temporal profiles are measured for a number of different biological conditions. We present a statistical test that makes explicit use of the temporal order in the data by fitting polynomial functions to the temporal profile of each gene and for each biological condition. A Hotelling T 2-statistic is derived to detect the genes for which the parameters of these polynomials are significantly different from each other.  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