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   3962篇
  免费   299篇
  国内免费   53篇
耳鼻咽喉   12篇
儿科学   74篇
妇产科学   76篇
基础医学   404篇
口腔科学   40篇
临床医学   622篇
内科学   771篇
皮肤病学   91篇
神经病学   420篇
特种医学   122篇
外科学   509篇
综合类   100篇
一般理论   4篇
预防医学   545篇
眼科学   56篇
药学   269篇
中国医学   9篇
肿瘤学   190篇
  2023年   37篇
  2022年   21篇
  2021年   61篇
  2020年   44篇
  2019年   65篇
  2018年   81篇
  2017年   72篇
  2016年   85篇
  2015年   114篇
  2014年   142篇
  2013年   189篇
  2012年   285篇
  2011年   296篇
  2010年   179篇
  2009年   179篇
  2008年   257篇
  2007年   251篇
  2006年   253篇
  2005年   221篇
  2004年   195篇
  2003年   179篇
  2002年   161篇
  2001年   57篇
  2000年   47篇
  1999年   67篇
  1998年   56篇
  1997年   37篇
  1996年   43篇
  1995年   43篇
  1994年   28篇
  1993年   29篇
  1992年   39篇
  1991年   29篇
  1990年   24篇
  1989年   33篇
  1988年   30篇
  1987年   33篇
  1986年   40篇
  1985年   29篇
  1984年   17篇
  1983年   18篇
  1982年   19篇
  1981年   19篇
  1980年   21篇
  1979年   19篇
  1977年   18篇
  1976年   18篇
  1975年   10篇
  1968年   10篇
  1966年   10篇
排序方式: 共有4314条查询结果,搜索用时 0 毫秒
51.
Current data and guidelines recommend treating abnormal blood lipids (ABL) to goal. This is a complex process and requires involvement from various healthcare professionals with a wide range of expertise. The model of a multidisciplinary case management approach for patients with ABL is well documented and described. This collaborative approach encompasses primary and secondary prevention across the lifespan, incorporates nutritional and exercise management as a significant component, defines the importance and indications for pharmacological therapy, and emphasizes the importance of adherence. Use of this collaborative approach for the treatment of ABL ultimately will improve cardiovascular and cerebrovascular morbidity and mortality.  相似文献   
52.
AIMS: T-box factors Tbx2 and Tbx3 play key roles in the development of the cardiac conduction system, atrioventricular canal, and outflow tract of the heart. They regulate the gap-junction-encoding gene Connexin43 (Cx43) and other genes critical for heart development and function. Discovering protein partners of Tbx2 and Tbx3 will shed light on the mechanisms by which these factors regulate these gene programs. METHODS AND RESULTS: Employing an yeast 2-hybrid screen and subsequent in vitro pull-down experiments we demonstrate that muscle segment homeobox genes Msx1 and Msx2 are able to bind the cardiac T-box proteins Tbx2, Tbx3, and Tbx5. This interaction, as that of the related Nkx2.5 protein, is supported by the T-box and homeodomain alone. Overlapping spatiotemporal expression patterns of Msx1 and Msx2 together with the T-box genes during cardiac development in mouse and chicken underscore the biological significance of this interaction. We demonstrate that Msx proteins together with Tbx2 and Tbx3 suppress Cx43 promoter activity and down regulate Cx43 gene activity in a rat heart-derived cell line. Using chromatin immunoprecipitation analysis we demonstrate that Msx1 can bind the Cx43 promoter at a conserved binding site located in close proximity to a previously defined T-box binding site, and that the activity of Msx proteins on this promoter appears dependent in the presence of Tbx3. CONCLUSION: Msx1 and Msx2 can function in concert with the T-box proteins to suppress Cx43 and other working myocardial genes.  相似文献   
53.
RATIONALE: High-resolution computed tomography (HRCT) is an integral aspect of the evaluation of patients with suspected idiopathic pulmonary fibrosis (IPF). However, few studies have evaluated its use in a large cohort. OBJECTIVES: To describe HRCT features in patients with mild to moderate IPF, compare diagnostic evaluations by a radiology core (three thoracic radiologists) with those by study-site radiologists, correlate baseline clinical and physiologic variables with HRCT findings, and evaluate their association with mortality. METHODS: We assessed HRCT scans from patients with IPF (n = 315) enrolled in a randomized controlled study evaluating IFN-gamma1b. MEASUREMENTS AND MAIN RESULTS: There was concordance between study-site and core radiologists regarding the diagnosis of IPF in 86% of cases. Diffusing capacity of carbon monoxide (DLCO) was the physiologic characteristic most highly correlated with HRCT findings. Multivariate analysis identified three independent predictors of mortality: a higher extent of fibrosis score increased the risk of death (p < 0.0001), whereas a higher percent-predicted DLCO (p = 0.004) and treatment assignment to IFN-gamma1b rather than placebo (p = 0.04) reduced the risk of death. CONCLUSIONS: A study-site diagnosis of IPF on HRCT was regularly confirmed by core radiologists. Extent of reticulation and honeycombing on HRCT is an important independent predictor of mortality in patients with IPF.  相似文献   
54.
Twenty patients with anemia and massive splenomegaly were studied in order to elucidate the mechanism by which splenomegaly results in plasma volume expansion. In 18 patients, increased plasma volume accounted for most of the anemia. Fourteen patients had an exaggerated renin response to standing, mean 1967 +/- 613 (SE) ng angiotensin ll/100 ml plasma (p less than 0.05). The mean resting forearm blood flow was increased 3.47 +/- 0.32 (SE) ml/100 ml forearm tissue (p less than 0.001). The venous capacitance was normal, as contrasted to a marked decrease in venous capacitance in patients with anemia of comparable degree without splenomegaly. Cardiac indices were increased in 10 of 11 patients (range 4.1-8.1 liters/min/sq m). In nine of ten patients oxygen consumption was increased (range 147-231 ml/min/sq m). Splenectomy was performed on 14 patients. Splenic blood flow was elevated in four of four patients (range 750-2000 ml/min). Splenic A-V oxygen difference was exaggerated in seven of seven patients and in three of three patients splenic indocyanine-green dye dilution curve failed to show an early peak suggestive of A-V shunting in the spleen. Free portal pressure was elevated in 12 of 12 patients and decreased immediately after splenectomy. The intravascular albumin mass decreased in ten patients, was unchanged in three at 2-4 mo after splenectomy, and was accompanied by a rise in the plasma albumin concentration in nine. These data suggest that a flow-induced portal hypertension with expansion of the portal vascular space is an important early hemodynamic change. This finding, together with a decreased peripheral resistance, probably results in a decrease in effective intravascular volume, resulting in stimulation of the renin-angiotensin-aldosterone system and other renal hemodynamic changes necessary for salt and water retention. Splenectomy usually accomplishes a complete reversal of these abnormalities and correction of the anemia.  相似文献   
55.
56.
57.
Peripheral arterial disease: identification and implications   总被引:12,自引:0,他引:12  
Peripheral arterial disease (PAD) is most commonly a manifestation of systemic atherosclerosis in which the arterial lumen of the lower extremities becomes progressively occluded by atherosclerotic plaque. Patients with PAD are at triple the risk of all-cause mortality and at more than 6 times the risk of death from coronary heart disease as those without the disease, yet PAD is probably the most underdiagnosed and least aggressively managed atherosclerotic disease. In the diagnosis of PAD, a detailed history and physical examination are extremely important, although limited by a lack of consistent sensitivity and specificity. Other office-based noninvasive tests, including the ankle-brachial index, can be easily performed to confirm the diagnosis and help stratify the risk. The ankle-brachial index correlates well with disease severity and functional symptoms and can also be used to assess disease progression and to predict cardiovascular and cerebrovascular mortality. Once diagnosed, risk factor modification, symptomatic relief, and secondary prevention strategies with antiplatelet agents form the core of medical management of PAD.  相似文献   
58.
Modest dietary restriction (DR) prolongs life in a wide range of organisms, spanning single-celled yeast to mammals. Here, we report the use of recent techniques in nutrition research to quantify the detailed relationship between diet, nutrient intake, lifespan, and reproduction in Drosophila melanogaster. Caloric restriction (CR) was not responsible for extending lifespan in our experimental flies. Response surfaces for lifespan and fecundity were maximized at different protein-carbohydrate intakes, with longevity highest at a protein-to-carbohydrate ratio of 1:16 and egg-laying rate maximized at 1:2. Lifetime egg production, the measure closest to fitness, was maximized at an intermediate P:C ratio of 1:4. Flies offered a choice of complementary foods regulated intake to maximize lifetime egg production. The results indicate a role for both direct costs of reproduction and other deleterious consequences of ingesting high levels of protein. We unite a body of apparently conflicting work within a common framework and provide a platform for studying aging in all organisms.  相似文献   
59.

Background

Colonoscopy is associated with multiple adverse outcomes. With an aging population undergoing colorectal cancer screening, few modalities exist to assess the patient risk prior to colonoscopy. Frailty, the age-related decline in reserve and function across multiple organ systems, predicts poor surgical outcomes, but its role in endoscopy is unclear.

Aims

This prospective cohort study assesses the efficacy of frailty in predicting acute colonoscopy outcomes.

Methods

Participants aged ≥?50 years undergoing screening colonoscopy at a tertiary care center were recruited over 2 months ending in July 2017. Frailty was assessed using a validated 20-s upper-extremity frailty test, which measures the capacity of muscle performance. Demographic data, American Society of Anesthesiologists (ASA) status, and Charlson comorbidity index (CCI) were evaluated. Procedure-related adverse events and cardiopulmonary changes during and in the immediate post-procedure period were recorded. Adverse events were stratified into minor and major events. Chi-square and ANCOVA models were used in the analysis.

Results

Ninety-nine adults (mean age 62.8 years) were enrolled, among which 49 were non-frail and 50 were pre-frail/frail; 50 were female. Overall, 55 participants experienced a total of 87 adverse events. Frailty and ASA status were significantly associated with colonoscopy adverse events (p?=?0.01 and p?=?0.02, respectively). Age and CCI did not predict colonoscopy outcomes.

Conclusions

Compared to age and CCI, frailty status better predicts colonoscopy outcomes in older adults. Among adults undergoing colonoscopy, routine frailty screening should be considered for risk stratification. Additional prospective studies evaluating frailty measurements in endoscopy will further clarify its role in forecasting adverse events.
  相似文献   
60.
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