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   6718篇
  免费   304篇
  国内免费   26篇
耳鼻咽喉   59篇
儿科学   142篇
妇产科学   112篇
基础医学   803篇
口腔科学   95篇
临床医学   757篇
内科学   1744篇
皮肤病学   186篇
神经病学   564篇
特种医学   93篇
外科学   935篇
综合类   38篇
一般理论   2篇
预防医学   548篇
眼科学   106篇
药学   465篇
中国医学   20篇
肿瘤学   379篇
  2024年   4篇
  2023年   41篇
  2022年   28篇
  2021年   169篇
  2020年   96篇
  2019年   192篇
  2018年   301篇
  2017年   164篇
  2016年   176篇
  2015年   206篇
  2014年   183篇
  2013年   298篇
  2012年   592篇
  2011年   635篇
  2010年   309篇
  2009年   222篇
  2008年   513篇
  2007年   528篇
  2006年   479篇
  2005年   458篇
  2004年   413篇
  2003年   406篇
  2002年   372篇
  2001年   22篇
  2000年   20篇
  1999年   19篇
  1998年   34篇
  1997年   18篇
  1996年   17篇
  1995年   13篇
  1994年   8篇
  1993年   16篇
  1992年   13篇
  1991年   8篇
  1990年   5篇
  1988年   3篇
  1987年   6篇
  1986年   5篇
  1985年   5篇
  1984年   5篇
  1983年   3篇
  1982年   11篇
  1981年   7篇
  1980年   6篇
  1979年   2篇
  1977年   3篇
  1976年   2篇
  1975年   2篇
  1973年   2篇
  1970年   2篇
排序方式: 共有7048条查询结果,搜索用时 15 毫秒
81.
82.
Aim: The Child Pugh and MELD are good methods for predicting mortality in patients with chronic liver disease. We investigated their performance as risk factors for failure to control bleeding, in-hospital overall mortality and death related to esophageal variceal bleeding episodes. Methods: From a previous collected database, 212 cirrhotic patients with variceal bleeding admitted to our hospital were studied. The predictive capability of Child Pugh and MELD scores were compared using c statistics. Results: The Child-Pugh and MELD scores showed marginal capability for predicting failure to control bleeding (the area under receiver operating characteristics curve (AUROC) values were < 0.70 for both). The AUROC values for predicting inhospital overall mortality of Child-Pugh and MELD score were similar: 0.809 (CI 95%, 0.710 - 0.907) and 0.88 (CI 95% 0.77-0.99,) respectively. There was no significant difference between them (p > 0.05). The AU-ROC value of MELD for predicting mortality related to variceal bleeding was higher than the Child-Pugh score: 0.905 (CI 95% 0.801-1.00) vs 0.794 (CI 95% 0.676 - 0.913) respectively (p < 0.05). Conclusions: MELD and Child-Pugh were not efficacious scores for predicting failure to control bleeding. The Child-Pugh and MELD scores had similar capability for predicting in-hospital overall mortality. Nevertheless, MELD was significantly better than Child-Pugh score for predicting in-hospital mortality related to variceal bleeding.  相似文献   
83.

Introduction and objectives

To assess the validity of the original low-risk SCORE function without and with high-density lipoprotein cholesterol and SCORE calibrated to the Spanish population.

Methods

Pooled analysis with individual data from 12 Spanish population-based cohort studies. We included 30 919 individuals aged 40 to 64 years with no history of cardiovascular disease at baseline, who were followed up for 10 years for the causes of death included in the SCORE project. The validity of the risk functions was analyzed with the area under the ROC curve (discrimination) and the Hosmer-Lemeshow test (calibration), respectively.

Results

Follow-up comprised 286 105 persons/y. Ten-year cardiovascular mortality was 0.6%. The ratio between estimated/observed cases ranged from 9.1, 6.5, and 9.1 in men and 3.3, 1.3, and 1.9 in women with original low-risk SCORE risk function without and with high-density lipoprotein cholesterol and calibrated SCORE, respectively; differences were statistically significant with the Hosmer-Lemeshow test between predicted and observed mortality with SCORE (P < .001 in both sexes and with all functions). The area under the ROC curve with the original SCORE was 0.68 in men and 0.69 in women.

Conclusions

All versions of the SCORE functions available in Spain significantly overestimate the cardiovascular mortality observed in the Spanish population. Despite the acceptable discrimination capacity, prediction of the number of fatal cardiovascular events (calibration) was significantly inaccurate.Full English text available from:www.revespcardiol.org/en  相似文献   
84.
The effect of antimicrobials on SOS-mediated mutagenesis induction depends on the bacterial species and the antimicrobial group. In this work, we studied the effect of different families of antimicrobial agents used in clinical therapy against Acinetobacter baumannii in the induction of mutagenesis in this multiresistant Gram-negative pathogen. The data showed that ciprofloxacin and tetracycline induce SOS-mediated mutagenesis, whereas colistin and meropenem, which are extensively used in clinical therapy, do not.  相似文献   
85.
The main purpose of the present meta-analysis was to examine the criterion-related validity of the 20-m shuttle run test for estimating cardiorespiratory fitness. Relevant studies were searched from twelve electronic databases up to December 2014, as well as from several alternative modes of searching. The Hunter-Schmidt’s psychometric meta-analysis approach was conducted to estimate the population criterion-related validity of the 20-m shuttle run test. From 57 studies that were included in the present meta-analysis, a total of 78 correlation values were analyzed. The overall results showed that the performance score of the 20-m shuttle run test had a moderate-to-high criterion-related validity for estimating maximum oxygen uptake (rp = 0.66-0.84), being higher when other variables (e.g. sex, age or body mass) were used (rp = 0.78-0.95). The present meta-analysis also showed that the criterion-related validity of Léger’s protocol was statistically higher for adults (rp = 0.94, 0.87-1.00) than for children (rp = 0.78, 0.72-0.85). However, sex and maximum oxygen uptake level do not seem to affect the criterion-related validity values. When an individual’s maximum oxygen uptake attained during a laboratory-based test is not feasible, the 20-m shuttle run test seems to be a useful alternative for estimating cardiorespiratory fitness. In adults the performance score only seems to be a strong estimator of cardiorespiratory fitness, in contrast among children the performance score should be combined with other variables. Nevertheless, as in the application of any physical fitness field test, evaluators must be aware that the performance score of the 20-m shuttle run test is simply an estimation and not a direct measure of cardiorespiratory fitness.

Key points

  • Overall the 20-m shuttle run test has a moderate-to-high mean criterion-related validity for estimating cardiorespiratory fitness.
  • The criterion-related validity of the 20-m shuttle run test is significantly higher for adults than for children. However, when the performance score is combined with other variables, the criterion-related validity value increases considerably among children.
  • Sex and maximum oxygen uptake level of individuals seem not to affect the criterion-related validity of the 20-m shuttle run test.
  • When individuals’ maximum oxygen uptake attained during a laboratory-based test is not feasible, the 20-m shuttle run test seems to be a useful alternative for estimating cardiorespiratory fitness.
Key words: Maximum oxygen uptake, peak oxygen uptake, PACER, Multistage fitness test, Léger test  相似文献   
86.
87.
To study the possible role of homocysteine in aneurysmatic progression, in 1994, 112 of 141 male patients with abdominal aortic aneurysm (AAA) diagnosed by population screening were interviewed and examined. Creatinine clearance estimated and total plasma homocysteine (P-tHcy) was measured by gas chromatography-mass spectrometry. Of the 112 cases, 99 were followed with annual ultrasonography and blood pressure measurements for 1–5 years (mean 2.5 years). The mean creatinine clearance was 70.8+/-23.1 ml/min, while the mean P-tHcy was 16.0+/-10.6 mmol/l, significantly increased compared with an age- and sex-matched reference population (P<0.01). However, no trend of correlation with AAA size or aneurysmal progression was found concerning creatinine clearance and homocysteine level. There were still no trend after adjustment for age, smoking, diastolic blood pressure, and initial ankle blood pressure index. However, the homocysteine level was positively correlated with decreasing creatinine clearance (r=0.36,P<0.01), and this correlation was still present after the same adjustments. A large proportion of men with AAA have mild hyperhomocysteinemia; this does not influence aneurysmal progression and may be due to coexisting impaired renal function. The finding might explain why prospective and intervention studies cannot prove for certain that hyperhomocysteinemia influences atherosclerotic progression, or that treatment is beneficial.  相似文献   
88.
Highly active antiretroviral therapy has decreased the morbidity and mortality of human immunodeficiency virus (HIV) infection, but latently infected cells remain for prolonged periods. CD4(+) CD45RO(+) T cells are a major latent virus reservoir in HIV-infected persons. Replication-competent, latently HIV-infected T cells can be generated in vitro by infecting peripheral blood mononuclear cells with HIV and then eliminating the HIV-producing cells with an anti-CD25 immunotoxin (IT). The CD25(-) latently infected cells then can be eliminated with an anti-CD45RO IT. This study determined whether this IT also could kill latently infected CD4 T cells from HIV-infected persons with or without detectable plasma viremia. The results show that ex vivo treatment of cells from HIV-positive persons by anti-CD45RO IT reduces the frequency of both productively and latently infected cells. In contrast, CD4(+) CD45RA(+) naive T cells and a proportion of CD4(+) CD45RO(lo) memory T cells are spared.  相似文献   
89.
OBJECTIVE: To analyze the genetic contribution of HLA in development of psoriatic arthritis (PsA) and to study whether MICA is primarily associated with PsA or whether its association is secondary to linkage disequilibrium with centromeric genes, such as MICB, TNFA, or HLA-DRB1. METHODS: DNA samples from 81 Spanish patients with PsA and 110 healthy controls were examined by polymerase chain reaction (PCR) sequence-specific primers to type HLA-Cw and HLA-DRB1, PCR sequence-specific oligonucleotides to determine HLA-B, and PCR restriction fragment length polymorphism for tumor necrosis factor-alpha promoter polymorphisms at positions -238 and -308. Analysis of microsatellite polymorphisms in the transmembrane region of MICA and in intron 1 of MICB was also carried out. RESULTS: HLA-Cw*0602 was significantly increased in PsA [60% vs 17%; p(c) < 0.00002, OR 7.33, etiological fraction (EF) 0.52]. MICA-A9 (60% vs 30%; p(c) = 0.0002, OR 3.57, EF 0.43) and the microsatellite MICB-CA-22 allele (23% vs 7%; p(c) = 0.028, OR 3.9, EF 0.17) were also significantly increased in PsA. MICA-A9 was in linkage disequilibrium with MICB-CA-22 (delta = 0.6). The association of MICA-A9 was independent of MICB-CA-22 and Cw*0602, since it was also associated in MICB-CA-22 negative (p(c) = 0.0015, OR 2.96, EF 0.34) and in Cw*0602 negative patients (p(c) = 0.034, OR 2.83, EF 0.34). TNFA and DRB I alleles were not significantly associated with PsA. CONCLUSION: Cw*0602 and MICA-A9 appear to be the strongest genetic susceptibility factors for PsA. However, MICA-A9 was associated independently of Cw6. HLA-B alleles and MICB-CA22 are associated secondarily to linkage with MICA. TNFA and HLA-DRB1 were not associated with PsA susceptibility, and our data suggest that their reported association may only reflect the linkage disequilibrium with MICA-A9 among the different populations studied.  相似文献   
90.
OBJECTIVES: To understand the role of Gemella species as a pathogen causing extra-abdominal infections in the Hospital General Universitario Gregorio Mara?ón. MATERIALS AND METHODS: Between 1994 and 1998, one or more isolates of Gemella sp. were found in 128 patients. The 113 patients with isolates from nonsignificant specimens or representing intra-abdominal infections were excluded. The clinical records of the remaining 15 patients were reviewed as well as the more recent literature. RESULTS: Mean age of patients was 41 years. The underlying conditions most frequently noted were intravenous drug users (n=6; 3 positive for human immunodeficiency virus), alcoholism (n=2), cardiovascular disease (n=2), chronic lung disease (n=2), diabetes (n=1), kidney transplant (n=1). The extra-abdominal infections were skin and soft tissue abscess (n=5), empyema (n=4), brain abscess (n=2), primary bacteremia (n=1), lung abscess (n=1), septic thrombophlebitis (n=1), complicated urinary tract infection (n=1). The infection was monomicrobial in six and polymicrobial in nine cases. Surgical drainage and betalactam antibiotics were used. The outcome was favorable in almost all cases. CONCLUSIONS: Gemella sp. should be included as a cause of localized soft-tissue abscesses, empyema, and bloodstream infection. No case of infective endocarditis was found. Although it is susceptible to several antibiotics, Gemella sp. requires a careful microbiologic diagnosis and a subtle clinical interpretation.  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