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   4072921篇
  免费   302682篇
  国内免费   10232篇
耳鼻咽喉   57537篇
儿科学   130399篇
妇产科学   111156篇
基础医学   568630篇
口腔科学   117006篇
临床医学   375367篇
内科学   789925篇
皮肤病学   91276篇
神经病学   338157篇
特种医学   158615篇
外国民族医学   1438篇
外科学   610210篇
综合类   91193篇
现状与发展   6篇
一般理论   1721篇
预防医学   325395篇
眼科学   94706篇
药学   301328篇
  12篇
中国医学   7990篇
肿瘤学   213768篇
  2018年   43707篇
  2017年   33608篇
  2016年   38191篇
  2015年   43089篇
  2014年   60673篇
  2013年   92099篇
  2012年   122391篇
  2011年   129875篇
  2010年   77879篇
  2009年   74455篇
  2008年   121871篇
  2007年   129456篇
  2006年   131201篇
  2005年   126850篇
  2004年   122244篇
  2003年   117849篇
  2002年   114682篇
  2001年   187059篇
  2000年   192544篇
  1999年   163311篇
  1998年   48490篇
  1997年   43268篇
  1996年   42906篇
  1995年   41620篇
  1994年   38636篇
  1993年   36151篇
  1992年   129757篇
  1991年   125527篇
  1990年   121334篇
  1989年   117245篇
  1988年   108362篇
  1987年   106746篇
  1986年   100819篇
  1985年   96584篇
  1984年   72642篇
  1983年   62033篇
  1982年   37358篇
  1981年   33618篇
  1979年   66754篇
  1978年   47236篇
  1977年   40023篇
  1976年   37493篇
  1975年   39597篇
  1974年   47990篇
  1973年   45811篇
  1972年   43108篇
  1971年   39923篇
  1970年   37310篇
  1969年   35275篇
  1968年   32452篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
AimsSelf-expanding metal stents provide rapid improvement of dysphagia in oesophageal cancer but are associated with complications. The aim of the present study was to test the effectiveness of an alternative treatment of combining biodegradable stents with radiotherapy.Materials and methodsA Simon two-stage single-arm prospective phase II trial design was used to determine the efficacy of biodegradable stents plus radiotherapy in patients with dysphagia caused by oesophagus cancer who were unsuitable for radical treatment. Fourteen patients were recruited and data from 12 were included in the final analyses.ResultsFive of 12 patients met the primary end point: one stent-related patient death; four further interventions for dysphagia within 16 weeks of stenting (41.7%, 95% confidence interval 15.2–72.3%). The median time to a 10-point deterioration of quality of life was 2.7 weeks. Nine patients died within 52 weeks of registration. The median time to death from any cause was 15.0 weeks (95% confidence interval 9.6–not reached).ConclusionThe high re-intervention observed, which met the pre-defined early stopping criteria, meant that the suggested alternative treatment was not sufficiently effective to be considered for a larger scale trial design. Further work is needed to define the place of biodegradable stents in the management of malignant oesophageal strictures.  相似文献   
42.
ABSTRACT

Expeditious linkage and consistent engagement in medical care is important for people with HIV’s (PWH) health. One theory on fostering linkage and engagement involves HIV status disclosure to mobilize social support. To assess disclosure and social support’s association with linkage and engagement, we conducted a qualitative study sampling black and Latino men who have sex with men (MSM of color) in the U.S. Participants' narratives presented mixed results. For instance, several participants who reported delaying, inconsistent access, or detachment from care also reported disclosing for support purposes, yet sporadic engagement suggests that their disclosure or any subsequent social support have not assisted. The findings contribute to the literature that questions disclosure and social support’s influence on care engagement, especially when decontextualized from circumstances and intentions. Our findings suggest the mechanics of disclosure and social support require planned implementation if intending to affect outcomes, especially among MSM of color. From the findings, we explore steps that may bolster interventions seeking to anchor medical care engagement.  相似文献   
43.

Background

Nursing Home Compare (NHC) ratings, created and maintained by Medicare, are used by both hospitals and consumers to aid in the skilled nursing facility (SNF) selection process. To date, no studies have linked NHC ratings to actual episode-based outcomes. The purpose of this study was to evaluate whether NHC ratings are valid predictors of 90-day complications, readmission, and bundle costs for patients discharged to an SNF after primary total joint arthroplasty (TJA).

Methods

All SNF-discharged primary TJA cases in 2017 at a multihospital academic health system were queried. Demographic, psychosocial, and clinical variables were manually extracted from the health record. Medicare NHC ratings were then collected for each SNF. For patients in the Medicare bundle, postacute and total bundle cost was extracted from claims.

Results

Four hundred eighty-eight patients were discharged to a total of 105 unique SNFs. In multivariate analysis, overall NHC rating was not predictive of 90-day readmission/major complications, >75th percentile postacute cost, or 90-day bundle cost exceeding the target price. SNF health inspection and quality measure ratings were also not predictive of 90-day readmission/major complications or bundle performance. A higher SNF staffing rating was independently associated with a decreased odds for >75th percentile 90-day postacute spend (odds ratio, 0.58; P = .01) and a 90-day bundle cost exceeding the target price (odds ratio = 0.69; P = .02) but was similarly not predictive of 90-day readmission/complications.

Conclusion

Results of our study suggest that Medicare's NHC tool is not a useful predictor of 90-day costs, complications, or readmissions for SNFs within our health system.  相似文献   
44.
45.
Nephrolithiasis is a common pathology encountered in the primary care and emergency department (ED) setting. In 2009 alone, there were over one million ED visits related to nephrolithiasis Higa et al. (2017) [1]. Emergent treatment options range from non-invasive pain control and patient education to lithotripsy and other invasive urologic procedures depending on stone location and related pathology. Urethral calculi are estimated to represent 0.3% of all urinary stone diseases Verit et al. (2006) [2]. There are very few case reports documenting distal urethral stone removal in the ED. Here we present a case of distal urethral stone impaction and the removal of this stone by ED providers, leading to expedited care and prevention of consultation and possible admission.  相似文献   
46.

Objective

The frailty index has been linked to adverse outcomes after surgical procedures. In this study, we evaluated the association between frailty index and outcomes after elective lower extremity bypass (LEB) for lower extremity ischemia.

Methods

The American College of Surgeons National Surgical Quality Improvement Program data set (2005-2012) was used to identify patients who underwent elective LEB using diagnostic and procedure Current Procedural Terminology codes. Modified frailty index (mFI) scores, derived from the Canadian Study of Health and Aging, were categorized into three groups: low, medium, and high. Association of mFI with 30-day postoperative death (POD), myocardial infarction (MI), cardiopulmonary events (CPEs), deep tissue surgical site infection (SSI), and graft failure (GF) was evaluated. Both univariate and multivariable regression analyses—adjusted for age, sex, American Society of Anesthesiologists class, body mass index, and creatinine levels—were used to assess the effect of frailty on each outcome.

Results

Of 12,677 patients (mean age, 67.7 ± 11.1 years) identified who underwent elective LEB, POD occurred in 265 (2.1% overall). Postoperative MI, SSI, CPEs, and GF occurred in 1.6%, 2.5%, 3.1%, and 4.3%, respectively. The mean mFI of the entire sample was 0.3 ± 0.1. Adjusted odds ratio for development of any morbidity in the group with the highest mFI was 1.36 (95% confidence interval, 1.08-1.72; P = .010) compared with the low frailty group. Patients with higher mFI were more likely to develop MI and CPEs but not SSI or GF. Univariate and multivariable analyses showed a significantly increased risk of POD among those in the highest mFI tertile. Female sex and age, increased American Society of Anesthesiologists class and creatinine levels, and decreased body mass index independently predicted increased mortality. The addition of categorical mFI improved models with these variables.

Conclusions

Higher mFI is independently associated with higher mortality and morbidity. Preoperative mFI assessment may be considered an additional screening tool for risk stratification among patients undergoing LEB.  相似文献   
47.

Background

We hypothesized that trends in total bilirubin in the context of cholecystitis and symptomatic cholelithiasis could be used to guide testing for the presence of common bile duct stones (CBDS).

Methods

A review of adult patients with acute cholecystitis or biliary colic with elevated total bilirubin and at least two levels drawn prior to procedural intervention was performed. Trends of total bilirubin and other serum makers were examined to predict the presence of CBDS.

Results

The total bilirubin level at presentation, average over 24?h and average over 48?h (3.74?mg/dl vs. 2.29?mg/dl, p?=?0.005; 3.72?mg/dl vs. 2.40?mg/dl, p?=?0.009; 2.41?mg/dl vs. 1.47?mg/dl, p?<?0.001) respectively, were all higher in those with CBDS. However, prediction was not improved by following levels over time.

Conclusion

Patients presenting with elevated serum bilirubin, should undergo immediate imaging or procedural intervention rather than obtaining follow-up bilirubin levels.  相似文献   
48.

Background and aims

There is controversy on the potentially benign nature of metabolically healthy obesity (MHO), i.e., obese persons with few or no metabolic abnormalities. So far, associations between MHO and coronary artery calcification (CAC), a measure of subclinical atherosclerosis, have mainly been studied cross-sectionally in Asian populations. We assessed cross-sectional and longitudinal MHO CAC associations in a Caucasian population.

Methods and results

In the Heinz Nixdorf Recall Study, a population-based cohort study in Germany, CAC was assessed by electron-beam tomography at baseline and at 5-year follow-up. For cross-sectional and longitudinal analyses, we included 1585 participants free of coronary heart disease at baseline, with CAC measurements at baseline and at follow-up, and with either normal weight (BMI 18.5–24.9 kg/m2) or obesity (BMI ≥30.0 kg/m2) at baseline. We used four definitions of MHO. In our main analysis, we defined obese persons as metabolically healthy if they met ≤1 of the NCEP ATP III criteria for the definition of the metabolic syndrome – waist circumference was not taken into account because of collinearity with BMI.Persons with MHO had a higher prevalence of CAC than metabolically healthy normal weight (MHNW) persons (prevalence ratio = 1.59 (95% confidence interval 1.38–1.84) for the main analysis). Persons with MHO had slightly larger odds of CAC progression than persons with MHNW (odds ratios ranged from 1.17 (0.69–1.99) to 1.48 (1.02–2.13) depending on MHO definition and statistical approach).

Conclusion

Our analyses on MHO CAC associations add to the evidence that MHO is not a purely benign health condition.  相似文献   
49.

Objective

To compare perioperative and long-term outcomes in patients undergoing hemiarch and aggressive arch replacement for acute type A aortic dissection (ATAAD).

Methods

From 1996 to 2017, we compared outcomes of hemiarch (n = 322) versus aggressive arch replacements (zones 2 and 3 arch replacement with implantation of 2-4 arch branches, n = 150) in ATAAD. Indications for aggressive arch were arch aneurysm >4 cm or intimal tear in the aortic arch that was not resectable by hemiarch replacement, or dissection of arch branches with malperfusion.

Results

Patients in the aggressive arch group were significantly younger (mean age: 57 vs 61 years old) and had significantly longer hypothermic circulatory arrest, cardiopulmonary bypass, and aortic crossclamp times. There were no significant differences in perioperative outcomes between hemiarch and aggressive arch groups, including 30-day mortality (5.3% vs 7.3%, P = .38) and postoperative stroke rate (7% vs 7%, P = .96). Over 15 years, Kaplan–Meier survival was similar between hemiarch and aggressive arch groups (log-rank P = .55, 10-year survival 70% vs 72%). Given death as a competing factor, incidence rates of reoperation over 15 years (2.1% vs 2.0% per year, P = 1) and 10-year cumulative incidence of reoperation (14% vs 12%, P = .89) for arch and distal aorta pathology were similar between the 2 groups.

Conclusions

Both hemiarch and aggressive arch replacement are appropriate approaches for select patients with ATAAD. Aggressive arch replacement should be considered for an arch aneurysm >4 cm or an intimal tear at the arch unable to be resected by hemiarch replacement, or dissection of the arch branches with malperfusion.  相似文献   
50.
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