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   1881337篇
  免费   138714篇
  国内免费   4332篇
耳鼻咽喉   25144篇
儿科学   59901篇
妇产科学   53066篇
基础医学   264483篇
口腔科学   54218篇
临床医学   165147篇
内科学   368177篇
皮肤病学   38402篇
神经病学   153458篇
特种医学   73475篇
外国民族医学   490篇
外科学   283831篇
综合类   46974篇
现状与发展   5篇
一般理论   841篇
预防医学   146313篇
眼科学   42466篇
药学   141534篇
  48篇
中国医学   3952篇
肿瘤学   102458篇
  2018年   19353篇
  2017年   15207篇
  2016年   16622篇
  2015年   19390篇
  2014年   27077篇
  2013年   40566篇
  2012年   55757篇
  2011年   59244篇
  2010年   34763篇
  2009年   32860篇
  2008年   56644篇
  2007年   59853篇
  2006年   60189篇
  2005年   58870篇
  2004年   57734篇
  2003年   54973篇
  2002年   53538篇
  2001年   82218篇
  2000年   84551篇
  1999年   72310篇
  1998年   21535篇
  1997年   19432篇
  1996年   18797篇
  1995年   18242篇
  1994年   17083篇
  1993年   16163篇
  1992年   59277篇
  1991年   57698篇
  1990年   56167篇
  1989年   54414篇
  1988年   50732篇
  1987年   49975篇
  1986年   47606篇
  1985年   46100篇
  1984年   34895篇
  1983年   30217篇
  1982年   18438篇
  1981年   16446篇
  1980年   15465篇
  1979年   32703篇
  1978年   22829篇
  1977年   19371篇
  1976年   18136篇
  1975年   19166篇
  1974年   23197篇
  1973年   22402篇
  1972年   20422篇
  1971年   19142篇
  1970年   17568篇
  1969年   16480篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
21.

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   
22.

Background

Highly cross-linked polyethylene (HXLPE) liners in total hip arthroplasty (THA) have demonstrated decreased wear rates, resilience to cup orientation, and reduced osteolysis compared to conventional polyethylene. Sequential irradiation and annealing below the melting temperature is unique compared to most HXLPE which is irradiated and remelted. This study purpose is to provide minimum 5-year femoral head penetration rates of sequentially annealed HXLPE in primary THA.

Methods

A retrospective review of a prospectively collected database identified 198 consecutive, cementless primary THAs utilizing sequentially annealed HXLPE (X3; Stryker, Mahwah, NJ). Operative technique was standardized. Radiographs were analyzed utilizing the Martell method with minimum 5-year and 1-year radiographs as baseline to minimize the initial bedding-in period.

Results

Seventy-seven hips with minimum 5-year follow-up were analyzed. Mean steady state linear and volumetric head penetration rates were 0.095 mm/y and 76 mm3/y, respectively. Volumetric head penetration was significantly less for 32-mm compared to 36-mm (P = .028). In addition, less head penetration was observed for ceramic 32-mm heads at nearly half the rate compared to cobalt-chromium 36-mm heads (P ≥ .092). No correlations existed between penetration rates and age, body mass index, University of California Los Angeles Activity Level, polyethylene thickness, cup inclination, or anteversion (P ≥ .10). No radiographic osteolysis was observed.

Conclusion

Surprisingly, linear head penetration rates of sequentially annealed HXLPE were nearly identical to the osteolysis threshold for conventional polyethylene and greater than reports of irradiated and remelted HXLPE. Furthermore, these data corroborate reports that HXLPE is resilient to cup orientation and demographic variables. Longer term follow-up is recommended.  相似文献   
23.
24.
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   
25.

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   
26.
27.

Background

Pulmonary hypertension (PH) is a comorbidity associated with interstitial lung disease (ILD). The purpose of this study was to evaluate the influence of PH on intrahospital mortality in lung transplantation (LT) for ILD.

Methods

We conducted a retrospective cohort study of 66 patients who underwent LT for ILD at the 12 de Octubre University Hospital (Madrid, Spain) from October 2008 to June 2014. PH was defined as mean pulmonary arterial pressure (mPAP) ≥25 mmHg on right-sided heart catheterization and intrahospital mortality as any death taken place after the transplantation of patients not being discharged.

Results

We retrospectively analyzed data of 66 patients; they were stratified by the presence or absence of PH before LT. Twenty-seven patients (41%) had PH. The PH group had a lower diffusing capacity of carbon monoxide (DLCO), carbon monoxide transfer coefficient (KCO), and 6-minute walk distance test (6MWT) and a higher total lung capacity (TLC), modified medical research council dyspnea scale (mMRC), and lung allocation score (LAS) than the non-PH group. Patients with PH more often underwent double lung transplantation (DLT; 59%) than single lung transplantation (SLT).Intrahospital mortality was 13% (9/66). No significant differences were observed in Kaplan-Meier survival curves for the PH and non-PH groups with a median survival time of 46 days versus 33 days (IQR 26–74; log-rank P = .056); however, the postoperative length of stay in the hospital was greater in the PH group.

Conclusions

In our cohort, pulmonary hypertension was not related to early mortality in lung transplantation recipients for interstitial lung diseases.  相似文献   
28.

Statement of problem

Polymeric material for 3-dimensional printing can be used to fabricate occlusal devices. However, information about fracture resistance and wear is scarce.

Purpose

The purpose of this in vitro study was to investigate the fracture resistance and 2-body wear of 3-dimensional–printed (3DP) (FotoDent splint; Dreve Dentamid GmbH), milled polymethylmethacrylate (CAM) (Temp Basic; Transpa 95H16, Zirkonzahn GmbH), and conventionally fabricated polymethylmethacrylate (CAST) (Castdon; Dreve Dentamid GmbH) occlusal devices.

Material and Methods

A total of 96 occlusal devices were prepared according to the 3 different manufacturing techniques 3DP, CAM, and CAST (n=32). For each manufacturing technique, specimens were further divided into initial fracture resistance tests (n=16) and artificial aging in the mastication simulator (50 N, 37°C) with 2-body wear followed by fracture resistance tests (n=16). The fracture resistance was determined using a universal testing machine (1 mm/min). The wear was measured after 20?000 and 120?000 mastication cycles with the replica technique, mapped with a laser scanner, and quantified in R software. Data were analyzed using a 2-way ANOVA followed by a 1-way ANOVA with Scheffé or Games-Howell post hoc tests, repeated measures ANOVA with corrected Greenhouse-Geisser P values, and the Levene, Mann-Whitney, and paired t tests (α=.05).

Results

CAM presented higher initial fracture resistance than 3DP or CAST (P<.001). After mastication simulation, CAM followed by 3DP showed higher fracture resistance than CAST (P<.001). Mastication simulation decreased the fracture resistance for CAM and CAST (P<.001) but not for 3DP (P=.78). Three-dimensional–printed occlusal devices showed the highest material volume loss, followed by CAM and the lowest in CAST (P<.001).

Conclusions

Three-dimensional–printed occlusal devices showed lower wear resistance and lower fracture resistance than those milled or conventionally fabricated. Therefore, only short-term application in the mouth is recommended. Further developments of occlusal device material for 3-dimensional printing are necessary.  相似文献   
29.

Background

Spontaneous spinal and intracranial subdural hematomas are rarely reported, especially occurring simultaneously. Anticoagulation use has been associated with spontaneous hemorrhages. Prompt diagnosis is required to prevent permanent neurological sequelae. In this case report, we describe a spontaneous spinal and intracranial subdural hematoma in a woman taking warfarin and initially presenting with severe vaginal pain.

Case Report

A 42-year-old woman who had a history of mechanical valve replacement and was therefore taking warfarin, came to an emergency department for relief of severe vaginal pain. Mild concurrent lumbar pain increased concern about spinal pathology, so magnetic resonance imaging of her spine was performed. It revealed a subdural hematoma extending from L1–S1 with arachnoiditis, which suggested intracranial pathology, though the patient had no complaint of a headache. Computed tomography of her brain demonstrated a large right subdural hemorrhage with midline shift. Subsequent imaging revealed no aneurysm or source of the intracranial bleeding. We concluded that the patient experienced spontaneous anticoagulation-related intracranial hemorrhage resulting in lumbar subdural hematoma and arachnoiditis with referred vaginal pain.

Why Should an Emergency Physician Be Aware of This?

Pelvic, vaginal, or perineal pain may be the presenting symptom in patients with lower spinal pathology. It is important to consider causes other than gynecological ones in the differential diagnosis of these patients, as well as to be cognizant of the relationship between spinal and intracranial subdural hemorrhages. In patients with back pain or radiating lumbar pain, especially coupled with neurological effects, clinicians should consider spinal subdural hemorrhage and arachnoiditis to expedite imaging studies and treatment of these rare entities.  相似文献   
30.
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