首页 | 官方网站   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   3214篇
  免费   274篇
  国内免费   23篇
医药卫生   3511篇
  2023年   14篇
  2022年   20篇
  2021年   73篇
  2020年   40篇
  2019年   59篇
  2018年   59篇
  2017年   52篇
  2016年   61篇
  2015年   72篇
  2014年   101篇
  2013年   128篇
  2012年   199篇
  2011年   197篇
  2010年   101篇
  2009年   107篇
  2008年   154篇
  2007年   183篇
  2006年   185篇
  2005年   187篇
  2004年   166篇
  2003年   174篇
  2002年   146篇
  2001年   146篇
  2000年   114篇
  1999年   100篇
  1998年   28篇
  1997年   14篇
  1996年   26篇
  1995年   23篇
  1994年   13篇
  1993年   15篇
  1992年   68篇
  1991年   52篇
  1990年   37篇
  1989年   40篇
  1988年   40篇
  1987年   49篇
  1986年   42篇
  1985年   30篇
  1984年   25篇
  1983年   19篇
  1982年   14篇
  1981年   17篇
  1980年   14篇
  1979年   15篇
  1978年   14篇
  1977年   11篇
  1976年   15篇
  1974年   12篇
  1973年   10篇
排序方式: 共有3511条查询结果,搜索用时 46 毫秒
61.
62.
OBJECTIVES: The objective of this study was to determine whether diastolic dysfunction is associated with increased risk of nonvalvular atrial fibrillation (NVAF) in older adults with no history of atrial arrhythmia. BACKGROUND: Few data exist regarding the relationship between diastolic function and NVAF. METHODS: The clinical and echocardiographic characteristics of patients age > or =65 years who had an echocardiogram performed between 1990 and 1998 were reviewed. Exclusion criteria were history of atrial arrhythmia, stroke, valvular or congenital heart disease, or pacemaker implantation. Patients were followed up in their medical records to the last clinical visit or death for documentation of first AF. RESULTS: Of 840 patients (39% men; mean [+/- SD] age, 75 +/- 7 years), 80 (9.5%) developed NVAF over a mean (+/- SD) follow-up of 4.1 +/- 2.7 years. Abnormal relaxation, pseudonormal, and restrictive left ventricular diastolic filling were associated with hazard ratios of 3.33 (95% confidence interval [CI], 1.5 to 7.4; p = 0.003), 4.84 (95% CI, 2.05 to 11.4; p < 0.001), and 5.26 (95% CI, 2.3 to 12.03; p < 0.001), respectively, when compared with normal diastolic function. After a number of adjustments, diastolic function profile remained incremental to history of congestive heart failure and previous myocardial infarction for prediction of NVAF. Age-adjusted Kaplan-Meier five-year risks of NVAF were 1%, 12%, 14%, and 21% for normal, abnormal relaxation, pseudonormal, and restrictive diastolic filling, respectively. CONCLUSIONS; The presence and severity of diastolic dysfunction are independently predictive of first documented NVAF in the elderly.  相似文献   
63.
64.
Thioredoxin and glutaredoxin may be important in regulating cell metabolism by mediating interchanges between sulfhydryl and disulfide groups. Components of the thioredoxin/glutaredoxin system from cultured HeLa cells have been partially purified and characterized by using Escherichia coli adenosine 3'-phosphate 5'-phosphosulfate reductase, a thioredoxin/glutaredoxin-dependent enzyme on the pathway of sulfate reduction, as an assay system. In HeLa cells, a NADPH-thioredoxin reductase and three heat-labile proteins (designated PI, PII, and PIII) that have thioredoxin- or glutaredoxin-like properties are found. Both PI and PIII have molecular masses of approximately 12,000 daltons and are readily reduced by their homologous HeLa thioredoxin reductase. However, only PI can be reduced efficiently by the glutathione system and neither PI nor PIII has inherent glutathione-disulfide oxidoreductase activity. PII has a molecular mass of greater than 30,000 daltons and appears to be associated with a reductase activity. The HeLa NADPH-thioredoxin reductase has been purified to near homogeneity and found to be a 116,000-dalton flavoprotein composed of two 58,000-dalton subunits. The HeLa enzyme has low species and substrate specificity and can reduce HeLa PI and PIII, E. coli thioredoxin and glutaredoxin, and the disulfide bond in 5,5'-dithiobis(2-nitrobenzoic acid). The exact in vivo roles of the HeLa thioredoxin/glutaredoxin system remain to be determined.  相似文献   
65.
A prospective study was undertaken to identify clinical, radiographical, haematological and biochemical profiles of severe acute respiratory syndrome (SARS) patients. A prediction rule, which demarcates low from high risk patients for SARS in an outbreak situation was developed. A total of 295 patients with unexplained respiratory illnesses, admitted to Queen Mary Hospital, Hong Kong SAR, China, in March to July 2003, were evaluated for clinical, radiological, haematological and alanine transaminase (ALT) data daily for 3 days after hospitalisation. In total, 44 cases were subsequently confirmed to have SARS by RT-PCR (68.2%) and serology (100%). The scoring system of attributing 11, 10, 3, 3 and 3 points to the presence of independent risk factors, namely: epidemiological link, radiographical deterioration, myalgia, lymphopenia and elevated ALT respectively, generated high and low-risk (total score 11-30 and 0-10, respectively) groups for SARS. The sensitivity and specificity of this prediction rule in positively identifying a SARS patient were 97.7 and 81.3%, respectively. The positive and negative predictive values were 47.8 and 99.5%, respectively. The prediction rule appears to be helpful in assessing suspected patients with severe acute respiratory syndrome at the bedside, and should be further validated in other severe acute respiratory syndrome cohorts.  相似文献   
66.
Intensive therapy and autologous blood and marrow transplantation (ABMT) is an established post-remission treatment for acute myeloid leukemia (AML), although its exact role remains controversial and few data are available regarding longer-term outcomes. We examined the long-term outcome of patients with AML transplanted at a single center using uniform intensive therapy consisting of etoposide, melphalan and TBI. In all, 145 patients with AML underwent ABMT: 117 in first remission, 21 in second remission and seven beyond second remission. EFS and OS were significantly predicted by remission status (P<0.0001). For transplantation in first remission, 8 year EFS and OS were 55% (95% CI, 44-64%) and 62% (95% CI, 50-72%), respectively. By multivariate analysis, only age (P=0.04) and cytogenetic risk group (P=0.006) influenced OS. For patients transplanted in second remission, 8 year EFS and OS were 30% (95% CI, 9-55%) and 36% (95% CI, 13-60%), respectively. No pre-transplant variables significantly predicted outcome. None of the seven patients who underwent ABMT beyond second remission or in early relapse were long-term survivors. ABMT can provide long-term antileukemic control for patients with AML in first remission. For patients in second remission approximately 30% can achieve cure with ABMT, and this option may be preferable to alternate donor allogeneic stem cell transplantation.  相似文献   
67.
OBJECTIVES:  Nonalcoholic fatty liver disease (NAFLD) is increasing in prevalence worldwide. This study aimed to validate the NAFLD fibrosis score in the Chinese population.
METHODS:  NAFLD patients were prospectively recruited for liver biopsy and blood tests. The NAFLD fibrosis score was calculated as −1.675 + 0.037 × age (yr) + 0.094 × BMI (kg/m2) + 1.13 × impaired fasting glucose/diabetes (yes = 1, no = 0) + 0.99 × AST/ALT ratio–0.013 × platelet (×109/L)−0.66 × albumin (g/dL). Advanced fibrosis was defined as stage 3 to 4 fibrosis.
RESULTS:  One hundred sixty-two patients (age 46 ± 10 yr, male 59%) were included in the study. Advanced fibrosis was found in 18 (11%) patients. Only 11 of 128 patients with the NAFLD fibrosis score below the proposed low cutoff point (<−1.455) were under-staged, resulting in a high negative predictive value of 91%. Only two patients exceeded the proposed high cutoff point (>0.676), but neither had advanced fibrosis. If the NAFLD fibrosis score was implemented in the Chinese population, 79% of liver biopsies could be avoided.
CONCLUSIONS:  The NAFLD fibrosis score has high negative predictive value in excluding advanced fibrosis in the Chinese population, and can reduce the burden of liver biopsy in the vast majority of cases. Since there were few cases of advanced fibrosis in this cohort, this study had limited power in validating the high cutoff point.  相似文献   
68.
Apelin can improve arterial function by enhancing the expression of endothelial nitric oxide synthase but this effect depends markedly on endothelial integrity. We hypothesized that inflammation influences the potential impact of apelin on arterial function in rheumatoid arthritis (RA). We assessed the associations of apelin concentrations with arterial stiffness (pulse wave velocity), wave reflection (augmentation index, reflected wave pressure, and reflection magnitude), and pressure pulsatility (central systolic pressure (CSP), central pulse pressure (CPP), peripheral pulse pressure (PPP), pulse pressure amplification (PPamp), and forward wave pressure (Pf)) among 170 RA patients without cardiovascular disease. In multivariable regression models, apelin concentrations were not independently associated with arterial function measures (p?≥?0.15) in all patients. Inflammation markers were not consistently associated with apelin levels but joint deformity counts, Disease Activity Score in 28 joints (DAS28), and erythrocyte sedimentation rate (ESR) impacted apelin-pressure pulsatility relations (interaction p?≤?0.05). In stratified analysis, apelin was associated with CSP (partial r?=???0.33, p?=?0.01), CPP (partial r?=???0.26, p?=?0.04), PPamp (partial r?=?0.27, p?=?0.03), and Pf (partial r?=???0.33, p?=?0.01) in patients without but not with joint deformities; apelin was related to CSP (partial r?=???0.24, p?=?0.05) in those with a DAS28 joint <?2.8 (median value) (partial r?=???0.24, p?=?0.05) but not ≥?2.8, and to CSP (partial r?=???0.36, p?=?0.003) in those with an erythrocyte sedimentation rate <?13 mm/h (median value) but not ≥?13 mm/h. Apelin is associated with reduced pressure pulsatility in RA patients without but not with a high inflammatory burden. A loss of apelin protective effects on arterial function may contribute to the link between RA severity and cardiovascular risk.  相似文献   
69.
Introduction: Acquired immunodeficiency syndrome (AIDS) is a kind of acquired disease that breaks down the immune system. Human immunodeficiency virus (HIV) is the causative agent of AIDS. By the end of 2016, there were 36.7 million people living with HIV worldwide. Early diagnosis can alert infected individuals to risk behaviors in order to control HIV transmission. Infected individuals are also benefited from proper treatment and management upon early diagnosis. Thanks to the public awareness of the disease, the annual increase of new HIV infections has been slowly declining over the past decades. The advent of molecular diagnostics has allowed early detection and better management of HIV infected patients.

Areas covered: In this review, the authors summarized and discussed the current and future technologies in molecular diagnosis as well as the biomarkers developed for HIV infection.

Expert Commentary: A simple and rapid detection of viral load is important for patients and doctors to monitor HIV progression and antiretroviral treatment efficiency. In the near future, it is expected that new technologies such as digital PCR and CRISPR-based technology will play more important role in HIV detection and patient management.  相似文献   

70.
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-23

京公网安备 11010802026262号