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   1133228篇
  免费   77329篇
  国内免费   1463篇
耳鼻咽喉   15873篇
儿科学   36274篇
妇产科学   29993篇
基础医学   161618篇
口腔科学   31028篇
临床医学   102511篇
内科学   214411篇
皮肤病学   25180篇
神经病学   86403篇
特种医学   44812篇
外国民族医学   202篇
外科学   171412篇
综合类   22793篇
现状与发展   1篇
一般理论   308篇
预防医学   80475篇
眼科学   25555篇
药学   90676篇
  25篇
中国医学   2875篇
肿瘤学   69595篇
  2021年   8638篇
  2019年   8782篇
  2018年   12435篇
  2017年   9704篇
  2016年   11058篇
  2015年   12315篇
  2014年   16799篇
  2013年   24403篇
  2012年   33747篇
  2011年   35511篇
  2010年   20774篇
  2009年   19469篇
  2008年   32878篇
  2007年   35042篇
  2006年   35630篇
  2005年   33966篇
  2004年   32498篇
  2003年   31112篇
  2002年   30055篇
  2001年   61385篇
  2000年   62880篇
  1999年   52186篇
  1998年   13194篇
  1997年   11607篇
  1996年   11528篇
  1995年   10831篇
  1994年   9844篇
  1993年   9315篇
  1992年   38798篇
  1991年   37242篇
  1990年   36677篇
  1989年   35171篇
  1988年   31699篇
  1987年   30810篇
  1986年   29006篇
  1985年   27290篇
  1984年   19886篇
  1983年   16736篇
  1982年   9278篇
  1979年   17607篇
  1978年   11852篇
  1977年   10608篇
  1976年   9208篇
  1975年   10378篇
  1974年   12033篇
  1973年   11627篇
  1972年   11106篇
  1971年   10406篇
  1970年   9527篇
  1969年   9211篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Abstract

Background: Increasing access to buprenorphine treatment is a critical tool for addressing the opioid epidemic in the United States. In 2016, a federal policy change allowed physicians who meet specific requirements to treat up to 275 concurrent buprenorphine patients. This study examines state-level measures of buprenorphine treatment supply over 21?months since this policy change and estimates associations between the supply of 275-patient waivers and state characteristics. Methods: Monthly state-level measures of the number of physicians holding the 275-patient waiver per 100,000 residents were constructed from September 2016 to May 2018 using the Drug Enforcement Agency’s Controlled Substance Act database. State characteristics were obtained from publicly available sources. Mixed-effects regression models were estimated to examine change over time. Results: During the 21-month period, the number of physicians waivered to treat 275 patients increased from 153 to 4009 physicians. The mean supply of 275-patient physicians per 100,000 state residents significantly increased from 0.07 (SD?=?0.21) in September 2016 to 1.43 (SD?=?1.08) in May 2018 (t?=??9.84, df?=?50, P?<?.001). The final mixed-effects regression model indicated that Census division and the preexisting supply of 100-patient waivered physicians were correlated with the rate of growth in 275-patient waivers over the study period. Conclusions: Although uptake of the 275-patient waiver has exceeded initial projections, growth is uneven across the United States. Unequal patterns of growth pose a challenge to efforts to increase treatment availability as a means of addressing the opioid epidemic.  相似文献   
42.
Abstract

Cardiac troponins (cTn) are currently the standard of care for the diagnosis of acute coronary syndromes (ACS) in patients presenting to the emergency department (ED) with chest pain (CP). However, their plasma kinetics necessitate a prolonged ED stay or overnight hospital admission, especially in those presenting early after CP onset. Moreover, ruling out ACS in low-risk patients requires prolonged ED observation or overnight hospital admission to allow serial measurements of c-Tn, adding cost. Heart-type fatty acid-binding protein (H-FABP) is a novel marker of myocardial injury with putative advantages over cTn. Being present in abundance in the myocellular cytoplasm, it is released rapidly (<1?h) after the onset of myocardial injury and could potentially play an important role in both earlier diagnosis of high-risk patients presenting early after CP onset, as well as in risk-stratifying low-risk patients rapidly. Like cTn, H-FABP also has a potential role as a prognostic marker in other conditions where the myocardial injury occurs, such as acute congestive heart failure (CHF) and acute pulmonary embolism (PE). This review provides an overview of the evidence examining the role of H-FABP in early diagnosis and risk stratification of patients with CP and in non-ACS conditions associated with myocardial injury.
  • Key messages
  • Heart-type fatty acid-binding protein is a biomarker that is elevated early in myocardial injury

  • The routine use in the emergency department complements the use of troponins in ruling out acute coronary syndromes in patients presenting early with chest pain

  • It also is useful in risk stratifying patients with other conditions such as heart failure and acute pulmonary embolism.

  相似文献   
43.

Background

There is continued debate regarding retention versus sacrificing of the posterior cruciate ligament (PCL) in total knee arthroplasty (TKA). We sought to determine if there was a difference in range of motion (ROM) after TKA between patients with PCL sacrifice versus PCL retention when using a highly congruent polyethylene insert.

Methods

We conducted an Institutional Review Board approved retrospective study of consecutive patients receiving TKA using the same implant with a highly congruent polyethylene component implanted by one surgeon from November 2013 to January 2016. Patients were placed in 2 groups based on whether the PCL was intact or released at the time of surgery. Patient charts were reviewed for age, body mass index, PCL status at surgery (incompetent, kept intact, or released), and preoperative/postoperative knee ROM.

Results

Both groups were similar in average age (60.5 vs 60.6, respectively) and body mass index (33.3 vs 32.6, respectively). Postoperative tibial slope (5.5° PCL release, 6.6° PCL retained, P = .028) was the only alignment variable reaching significance; all other alignment and motion variables were similar.

Conclusion

Results indicate that the PCL can be successfully retained with the use of a congruent bearing design, with no evident limitation in postoperative ROM or loss of stability due to the bearing in comparison to patients who undergo PCL release.  相似文献   
44.
45.

Background

Physicians treating nonvalvular atrial fibrillation (AF) assess stroke and bleeding risks when deciding on anticoagulation. The agreement between empirical and physician-estimated risks is unclear. Furthermore, the association between patient and physician sex and anticoagulation decision-making is uncertain.

Methods

We pooled data from 2 national primary care physician chart audit databases of patients with AF (Facilitating Review and Education to Optimize Stroke Prevention in Atrial Fibrillation and Coordinated National Network to Engage Physicians in the Care and Treatment of Patients with Atrial Fibrillation Chart Audit) with a combined 1035 physicians (133 female, 902 male) and 10,927 patients (4567 female and 6360 male).

Results

Male physicians underestimated stroke risk in female patients and overestimated risk in male patients. Female physicians estimated stroke risk well in female patients but underestimated the risk in male patients. Risk of bleeding was underestimated in all. Despite differences in risk assessment by physician and patient sex, > 90% of patients received anticoagulation across all subgroups. There was modest agreement between physician estimated and calculated (ie, CHADS2 score) stroke risk: Kappa scores were 0.41 (0.35-0.47) for female physicians and 0.34 (0.32-0.36) for male physicians.

Conclusions

Our study is the first to examine the association between patient and physician sex influences and stroke and bleeding risk estimation in AF. Although there were differences in agreement between physician estimated stroke risk and calculated CHADS2 scores, these differences were small and unlikely to affect clinical practice; further, despite any perceived differences in the accuracy of risk assessment by sex, most patients received anticoagulation.  相似文献   
46.

Background and aims

It is not known whether non alcoholic fatty liver disease (NAFLD) is a risk factor for diabetes in non obese, non centrally-obese subjects. Our aim was to investigate relationships between fatty liver, insulin resistance and a biomarker score for liver fibrosis with incident diabetes at follow up, in subjects who were neither obese nor centrally-obese.

Methods and results

As many as 70,303 subjects with a body mass index (BMI) < 25 kg/m2 and without diabetes were followed up for a maximum of 7.9 years. At baseline, fatty liver was identified by liver ultrasound, insulin resistance (IR) by homeostatic model assessment of insulin resistance (HOMA-IR) ≥2.0, and central obesity by waist circumference (waist circumference ≥90 cm (men) and ≥85 cm (women). The Fibrosis-4 (FIB-4 score) was used to estimate extent of liver fibrosis. Cox proportional hazards models adjusted for confounders were used to estimate hazard ratios (aHRs) for incident diabetes. As many as 852 incident cases of diabetes occurred during follow up (median [IQR] 3.71 [2.03] years). Mean ± SD BMI was 22.8 ± 1.8 and 21.7 ± 2.0 kg/m2 in subjects with and without diabetes at follow up. In subjects without central obesity and with fatty liver, aHRs (95% CI) for incident diabetes at follow up were 2.17 (1.56, 3.03) for men, and 2.86 (1.50,5.46) for women. Similar aHRs for incident diabetes occurred with fatty liver, IR and the highest quartile of FIB-4 combined, in men; and there was a non significant trend toward increased risk in women.

Conclusions

In normal weight, non-centrally obese subjects NAFLD is an independent risk factor for incident diabetes.  相似文献   
47.
Abstract

Purpose: We aimed to evaluate the construct validity of the Eating Assessment Tool (EAT-10) by determining its dimensionality, rating scale integrity, item-person match, precision and relationship with the degree of airway invasion and functional oral intake.

Methods: We conducted a retrospective analysis of patients’ EAT-10 scores. We used the Rasch rating scale model. We investigated correlations between the EAT-10 and scores on the Penetration-Aspiration Scale (PAS) and Functional Oral Intake Scale (FOIS).

Results: The median score of the EAT-10 from 127 patients was 16 of 40 (range 0–40). Confirmatory factor analysis supported unidimensionality. The 5-point rating scale categories met published criteria. Two items misfit the Rasch model and two other items displayed differential item functioning. Rasch person reliability was 0.79. Our patient cohort was divided into three person-strata. Correlations between the EAT-10 and the PAS and FOIS were weak to moderate in strength (respectively: r?=?0.26, p?=?0.0036; r?=??0.27, p?=?0.0027).

Conclusions: Our analyses identified deficits in the construct validity of the EAT-10 suggestive of a need to improve the EAT-10 to support its frequent use in clinical practice and research.
  • Implications for Rehabilitation
  • Swallowing disorders are associated with severe complications, such as pneumonia and malnutrition, and impose both social and psychological burdens on patients.

  • The Eating Assessment Tool is a self-report instrument developed to estimate initial dysphagia severity and monitor change in patient-reported dysphagia symptoms as a response to treatment.

  • This study shows that the Eating Assessment Tool has deficits in its construct validity and a need to improve the instrument to support its frequent use in clinical practice and research.

  相似文献   
48.
BackgroundThe efficacy of ticagrelor in the long-term post–ST-segment elevation myocardial infarction (STEMI) treated with fibrinolytic therapy remains uncertain.ObjectivesThe purpose of this study was to evaluate the efficacy of ticagrelor when compared with clopidogrel in STEMI patients treated with fibrinolytic therapy.MethodsThis international, multicenter, randomized, open-label with blinded endpoint adjudication trial enrolled 3,799 patients (age <75 years) with STEMI receiving fibrinolytic therapy. Patients were randomized to ticagrelor (180-mg loading dose, 90 mg twice daily thereafter) or clopidogrel (300- to 600-mg loading dose, 75 mg daily thereafter). The key outcomes were cardiovascular mortality, myocardial infarction, or stroke, and the same composite outcome with the addition of severe recurrent ischemia, transient ischemic attack, or other arterial thrombotic events at 12 months.ResultsThe combined outcome of cardiovascular mortality, myocardial infarction, or stroke occurred in 129 of 1,913 patients (6.7%) receiving ticagrelor and in 137 of 1,886 patients (7.3%) receiving clopidogrel (hazard ratio: 0.93; 95% confidence interval: 0.73 to 1.18; p = 0.53). The composite of cardiovascular mortality, myocardial infarction, stroke, severe recurrent ischemia, transient ischemic attack, or other arterial thrombotic events occurred in 153 of 1,913 patients (8.0%) treated with ticagrelor and in 171 of 1,886 patients (9.1%) receiving clopidogrel (hazard ratio: 0.88; 95% confidence interval: 0.71 to 1.09; p = 0.25). The rates of major, fatal, and intracranial bleeding were similar between the ticagrelor and clopidogrel groups.ConclusionAmong patients age <75 years with STEMI, administration of ticagrelor after fibrinolytic therapy did not significantly reduce the frequency of cardiovascular events when compared with clopidogrel. (Ticagrelor in Patients With ST Elevation Myocardial Infarction Treated With Pharmacological Thrombolysis [TREAT]; NCT02298088)  相似文献   
49.

Introduction

There is an urgent need for new anti-tuberculosis (TB) drugs and optimization of current TB treatment. Moxifloxacin and linezolid are valuable options for the treatment of drug-resistant TB; however, it is crucial to find a dose at which these drugs not only show high efficacy but also suppress the development of further drug resistance.

Methods

Activity of moxifloxacin and linezolid against Mycobacterium tuberculosis was studied in the hollow-fiber infection model system in log-phase growth under neutral pH and slow growth in an acidic environment. Doses that achieved maximum bacterial kill while suppressing the emergence of drug resistance were determined. Through Monte Carlo simulations the quantitative output of this in vitro study was bridged to the human patient population to inform optimal dosage regimens while accounting for clinical minimum inhibitory concentration (MIC) distributions.

Results and Discussion

Moxifloxacin activity was significantly decreased in an acidified environment. The loss of activity was compensated by accumulation of the drug in TB lung lesions; therefore, moderate efficacy can be expected. Moxifloxacin 800 mg/day is the dose that most likely leads to resistance suppression while exerting maximum bacterial kill. Linezolid demonstrated very good activity even at a reduced pH. Linezolid 900 mg once-daily (QD) is likely to achieve a maximum killing effect and prevent the emergence of drug resistance; 600 mg QD in a robust drug regimen may have similar potential.  相似文献   
50.
Background and purpose — 1 in 5 patients are dissatisfied following unicompartmental or total knee arthroplasty (UKA or TKA). This may be partly explained by failing to return to desired activity post-arthroplasty. To facilitate return to desired activity, a greater understanding of predictors of return to desired activity in UKA and TKA patients is needed. We compared rates of return to desired activity 12 months following UKA vs. TKA, and identified and compared predictors of return to desired activity 12 months following UKA vs. TKA.

Patients and methods — Patients were prospectively recruited from 2 hospitals prior to undergoing UKA or primary TKA. Patients reported preoperatively the activity/activities that were limited due to their knee that they wished to return to after arthroplasty. At 12-months postoperatively, patients reported whether they had returned to these activities (‘return to desired activity’). Preoperative predictors evaluated were age, sex, BMI, education, comorbidities, pain expectations, Oxford Knee Score (OKS), UCLA Activity Score, and EQ-5D. Generalized linear models assessed the relationship between potential predictors and return-to-desired-activity.

Results — The response rate of all patients eligible for 12-month follow-up was 74%. TKA patients (n = 575) were older (mean (SD) 70 (9) vs. 67 (10)) with a greater BMI (31 (6) vs. 30 (5)) than patients undergoing UKA (n = 420). 75% of UKA and 59% of TKA patients returned to desired activity. TKA patients had a greater risk of non-return to desired activity than patients undergoing UKA (risk ratio (95% CI) 1.5 (1.2–1.8)). Predictors of non-return to desired activity following UKA were worse OKS (0.96 (0.93–0.99)), higher BMI (1.04 (1.01–1.08)), and worse expectations (1.9 (1.2–2.8)). Predictors of non-return to desired activity following TKA were worse EQ-5D (0.53 (0.33–0.85)) and worse OKS (0.98 (0.96–1.0)).

Interpretation — UKA patients were more likely to return to desired activity than TKA patients. Predictors of return to desired activity differed following UKA and TKA. Optimizing selection of arthroplasty procedure based on patient characteristics and targeting predictors of poor outcome may facilitate return to desired activity with potential to enhance postoperative satisfaction.  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