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   12942篇
  免费   641篇
  国内免费   32篇
耳鼻咽喉   171篇
儿科学   377篇
妇产科学   352篇
基础医学   1616篇
口腔科学   304篇
临床医学   758篇
内科学   3504篇
皮肤病学   407篇
神经病学   859篇
特种医学   198篇
外科学   1709篇
综合类   133篇
一般理论   2篇
预防医学   1390篇
眼科学   232篇
药学   887篇
中国医学   79篇
肿瘤学   637篇
  2023年   87篇
  2022年   81篇
  2021年   282篇
  2020年   150篇
  2019年   342篇
  2018年   509篇
  2017年   289篇
  2016年   304篇
  2015年   283篇
  2014年   368篇
  2013年   534篇
  2012年   880篇
  2011年   942篇
  2010年   508篇
  2009年   360篇
  2008年   788篇
  2007年   818篇
  2006年   852篇
  2005年   806篇
  2004年   737篇
  2003年   712篇
  2002年   655篇
  2001年   379篇
  2000年   457篇
  1999年   328篇
  1998年   72篇
  1997年   55篇
  1996年   41篇
  1995年   29篇
  1994年   33篇
  1993年   34篇
  1992年   104篇
  1991年   88篇
  1990年   102篇
  1989年   70篇
  1988年   59篇
  1987年   63篇
  1986年   62篇
  1985年   46篇
  1984年   24篇
  1983年   28篇
  1982年   17篇
  1980年   14篇
  1979年   14篇
  1978年   18篇
  1976年   14篇
  1974年   14篇
  1973年   16篇
  1971年   20篇
  1969年   18篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
241.
INTRODUCTION AND OBJECTIVES: Previous studies angiotensin-converting enzyme gene insertion/deletion polymorphism ACE (I/D), angiotensinogen gene polymorphism, and angiotensin II AT1 receptor polymorphism in relation to coronary heart disease controversial results. This study was designed to analyze the association between these gene polymorphisms and the first coronary event in individuals residing on Grand Canary Island, Spain. PATIENTS AND METHOD: Case-control study. Case subjects (n = 304) were recruited at the first coronary event; age-matched controls (n = 315) were randomly selected from the Grand Canary population. Participants were examined for the usual risk factors. Blood samples were obtained for biochemical analyses and DNA extraction. Genotyping was performed by PCR and restriction analysis. RESULTS: Neither ACE (I/D) nor AT1 receptor polymorphism was associated with coronary heart disease, whereas the frequency distribution of AGT M235T genotypes among patients and control subjects (TT: 29% and 19%; MT: 48% and 50%; MM: 22% and 31%, respectively) was statistically different (p = 0.003). Multiple logistic regression analysis identified the TT genotype of the angiotensinogen gene (OR = 1.9; 95% CI 1.1-3.4), diabetes (OR = 4.4; 95% CI 2.0-9.4) and hypertension (OR = 2.1; 95% CI 1.3-3.3) as risk factors predicting the coronary event. CONCLUSIONS: Our results provide no evidence of an association between ACE (I/D) or AT1 receptor polymorphism and coronary heart disease. However, homozygosity for the T allele of the angiotensinogen gene, diabetes and hypertension independently place individuals at higher risk of experiencing a coronary event on Grand Canary Island.  相似文献   
242.
243.
Increased risk of tuberculosis in patients with rheumatoid arthritis   总被引:6,自引:0,他引:6  
OBJECTIVE: To quantify the risk of tuberculosis (TB) in an unselected sample of patients with rheumatoid arthritis (RA) compared to the risk in the general population. METHODS: The incidence of TB in the general population of Spain was obtained from the National Network of Epidemiological Surveillance reports. The incidence of TB was ascertained from a cohort of 788 patients with RA selected randomly from the registries of 34 participating centers throughout Spain. A patient was considered a TB case only if information about disease symptoms, microorganism identification, and TB treatment were confirmed in the clinical records. The relative risk of TB in RA was calculated by dividing the standardized mean incidence of TB from 1990 to 2000 in the RA cohort by the mean incidence of TB in Spain during the same years. RESULTS: The mean incidence of TB in the general population of Spain from 1990 to 2000 was 23 cases per 100,000. Seven cases of TB were identified in the RA cohort, yielding a mean annual incidence (1990-2000) of 134/100,000 patients. The incidence risk ratio of pulmonary TB in patients with RA compared to the general population is 3.68 (95% CI 2.36-5.92). CONCLUSION: We found a 4-fold increased risk of TB infection in patients diagnosed with RA. These results might help to interpret the magnitude of the problem attributable to the introduction of new therapies in RA.  相似文献   
244.
245.
Powdered infant formula is not sterile and may be intrinsically contaminated with pathogens, such as Salmonella enterica, that can cause serious illness in infants. In recent years, at least 6 outbreaks of Salmonella infection in infants that have been linked to the consumption of powdered infant formula have been reported. Many of these outbreaks were identified because the Salmonella strains were unique in some way (e.g., a rare serotype) and a well-established Salmonella surveillance network, supported by laboratories capable of serotyping isolates, was in place. Another common feature of the outbreaks was the low level of salmonellae detected in the implicated formula (salmonellae may be missed in routine testing). These outbreaks likely represent only a small proportion of the actual number of Salmonella infections in infants that have been linked to powdered infant formula. Managing this problem requires a multidimensional approach in which manufacturers, regulators, and caregivers to infants can all play a role.  相似文献   
246.
Introduction and objectivesOur objective was to approximate the prevalence of mutations in candidate genes for familial hypercholesterolemia (FH) in a middle-aged Spanish population and to establish the predictive value of criteria for clinical suspicion in the detection of causative mutations.MethodsUnrelated individuals aged ≥ 18 years from the Aragon Workers’ Health Study (AWHS) with high low-density lipoprotein cholesterol (LDL-C) and clinical suspicion of FH (participants with LDL-C concentrations above the 95th percentile, participants with premature cardiovascular disease and/or participants with high LDL-C [130 mg/dL] under statin therapy), assuming that any participant with FH exhibits at leats 1 trait, were selected and the LDLR, APOB, PCSK9, APOE, STAP1 and LDLRAP1 genes were sequenced by next generation sequencing technology.ResultsOf 5400 individuals from the AWHS, 4514 had complete data on lipid levels and lipid-lowering drugs, 255 participants (5.65%) met the criteria for suspicion of FH, 24 of them (9.41%) were diagnosed with hyperlipoproteinemia(a), and 16 (6.27% of those sequenced) were found to carry causative mutations in candidate genes: 12 participants carried 11 different pathogenic LDLR alleles and 4 participants carried 1 pathogenic mutation in PCSK9. LDL-C concentrations > 220 mg/dL and LDL-C > 130 mg/dL despite statin therapy showed the strongest association with the presence of mutations (P = .011).ConclusionsOur results show that the prevalence of FH in Spain is 1:282 and suggest that the combination of high untreated LDL-C and high levels of LDL-C despite statin therapy are the best predictors of a positive FH genetic test.  相似文献   
247.
OBJECTIVE: Upper GI bleeding (UGIB) is a common medical emergency that leads to a high consumption of medical resources and costs. We aimed to analyze the influence of physician specialty on the costs of nonvariceal UGIB care. METHODS: We retrospectively assessed 350 nonvariceal UGIB episodes that were primarily cared for by gastroenterologists (n = 142), internists (n = 67), or surgeons (n = 141). Gastroenterologists followed evidence-based clinical protocols that included early endoscopy and early hospital discharge for uncomplicated bleeding. A risk score system was used to control for severity of illness. Linear regression analyses were performed to find out predictors of costs and the influence of specialist care on length of stay (LOS). RESULTS: The overall mean hospital cost was significantly lower in patients cared for by gastroenterologists (EUR 1,630) than in those managed by internists (EUR 3,745, p < 0.001) or surgeons (EUR 2,513, p < 0.05). The mean LOS was the variable with highest influence on total cost. Patients cared for by gastroenterologists had a mean LOS significantly shorter (7.3 days) than that of those treated by internists (16.2 days, p < 0.001) or surgeons (11 days, p < 0.001). Hospital costs and LOS differences were maintained when adjusting for severity of illness. In caring for low risk patients, nongastroenterologists had a higher probability of having a hospital stay longer than 4 days (odds ratio = 18.4, Cl = 4.6-73.6, p < 0.001). CONCLUSION: The implementation of specific evidence-based protocols by gastroenterologists reduces length of hospital stay and saves medical costs in patients with nonvariceal UGIB, especially those at low risk.  相似文献   
248.
249.
INTRODUCTION AND OBJECTIVES: Some authors have described seasonal variations in the incidence of acute myocardial infarction. The aim of this study was to determine the existence of seasonal rhythms in admissions for acute myocardial infarction to coronary care units, and in mortality, and to analyze the influence of age on environmental factors. PATIENTS AND METHOD: The study included a total of 8400 consecutive patients with acute myocardial infarction admitted to 12 coronary care units in the PRIMVAC registry from January 1995 to December 1999. Seasonal rhythms were analyzed with the time series method and the Cosinor regression equation. The influence of age was analyzed with the chi 2 test. RESULTS: The total number of admissions increased in winter and decreased in summer. The highest peak (acrophase) occurred in winter, with 2183 cases (r2=0.91), specifically in February, with 742 cases (r2=0.66). The age of the patients conditioned seasonal variations (P=.006), and the influence was statistically significant for patients over 65 years of age. Changes in mortality with time did not reach statistical significance. CONCLUSIONS: A seasonal rhythm in admissions for acute myocardial infarction was found, with an increase in winter and a decrease in summer. Age conditioned the effect of environmental factors on acute myocardial infarction, and patients aged 65 years or older were more sensitive to mechanisms that led to increases in admissions in winter.  相似文献   
250.
Background Residual plaque burden after coronary stenting may be visualized by use of intravascular ultrasound. Determinants and implications of residual atherosclerotic plaque burden after coronary stenting are not well established. In particular, the implications of residual plaque burden, after adjusting for confounding factors, are still unknown. Methods Sixty-two consecutive patients (age 56 ± 9 years) undergoing coronary stenting under intravascular ultrasound imaging guidance were prospectively studied. A total of 616 slices were analyzed (every 2 mm of stent length) from motorized pull-back recordings. Residual plaque burden was calculated as residual plaque/vessel area × 100. Results In 565 slices (89%), both residual plaque area and stent area could be measured. Mean residual plaque burden was 46.5% ± 6%. By use of multiple regression analysis, lesion plaque area and reference segment plaque burden were identified as independent predictors of residual plaque burden after stenting. In addition, a significant correlation was found between residual plaque burden and most relevant angiographic parameters at follow-up (including minimal lumen diameter, percent diameter stenosis, and loss index), which persisted after adjustment. Furthermore, stents with a residual plaque burden ≥46% had higher a restenosis rate (relative risk [RR] 4.4, 95% CI 1.09-18.2, P = .03). On logistic regression analysis, residual plaque burden (RR 4.8, 95% CI 4.1-5.6, P = .01) and diabetes (RR 4.3, 95% CI 3.6-5.1, P = .03) emerged as the only independent predictors of restenosis. Conclusions The amount of residual plaque burden after coronary stenting plays an independent role on the late angiographic outcome of these patients. (Am Heart J 2003;145:254-61.)  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