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   2397181篇
  免费   182506篇
  国内免费   4100篇
耳鼻咽喉   34485篇
儿科学   72926篇
妇产科学   62965篇
基础医学   335891篇
口腔科学   67767篇
临床医学   216284篇
内科学   471001篇
皮肤病学   48103篇
神经病学   201760篇
特种医学   96272篇
外国民族医学   886篇
外科学   361487篇
综合类   56239篇
现状与发展   1篇
一般理论   977篇
预防医学   191050篇
眼科学   55638篇
药学   178161篇
  56篇
中国医学   4385篇
肿瘤学   127453篇
  2018年   24373篇
  2016年   20784篇
  2015年   23383篇
  2014年   33646篇
  2013年   50964篇
  2012年   68921篇
  2011年   72530篇
  2010年   42597篇
  2009年   40982篇
  2008年   68934篇
  2007年   73322篇
  2006年   74246篇
  2005年   72254篇
  2004年   69545篇
  2003年   67201篇
  2002年   66440篇
  2001年   112631篇
  2000年   116692篇
  1999年   98483篇
  1998年   27940篇
  1997年   25571篇
  1996年   25493篇
  1995年   24651篇
  1994年   23195篇
  1993年   21585篇
  1992年   79498篇
  1991年   76496篇
  1990年   73685篇
  1989年   70952篇
  1988年   65959篇
  1987年   64908篇
  1986年   61447篇
  1985年   58504篇
  1984年   44277篇
  1983年   37712篇
  1982年   22914篇
  1981年   20353篇
  1980年   19058篇
  1979年   41333篇
  1978年   29014篇
  1977年   24371篇
  1976年   22852篇
  1975年   23990篇
  1974年   29670篇
  1973年   28065篇
  1972年   26250篇
  1971年   24170篇
  1970年   22779篇
  1969年   21112篇
  1968年   19160篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.

Aims

Concomitant chemoradiation is the standard of care in patients with inoperable non-small cell lung cancer. The purpose of this study was to analyse the survival outcome and toxicity data of using hypofractionated chemoradiation.

Materials and methods

One hundred patients were treated from June 2011 to November 2016. Treatment consisted of 55 Gy in 20 daily fractions concurrently with split-dose cisplatin vinorelbine chemotherapy over 4 weeks followed by two cycles of cisplatin vinorelbine only. Survival was estimated using Kaplan–Meier and Cox regression was carried out for known prognostic factors. A systematic search of literature was conducted using Medline, Embase and Cochrane databases and relevant references included.

Results

In total, 97% of patients completed radiotherapy and 73% of patients completed all four cycles of chemotherapy. One patient died of a cardiac event during consolidative chemotherapy. There were two cases of grade 4 toxicities (one sepsis, one renal impairment). Grade 3 toxicities included nausea/vomiting (17%), oesophagitis (15%), infection with neutropenia (12%) and pneumonitis (4%). Clinical benefit was seen in 86%. Two-year progression-free survival and overall survival rates were 49% and 58%, respectively. The median progression-free survival and overall survival were 23.4 and 43.4 months, respectively. The only significant prognostic factor was the number of chemotherapy cycles received (P = 0.02). The systematic review identified 13 relevant studies; a variety of regimens were assessed with variable reporting of outcomes and toxicity but with overall an improvement in survival over time.

Conclusion

Our experience compared with the original phase II trial showed improved treatment completion rates and survival with acceptable morbidity. With appropriate patient selection this regimen is an effective treatment option for locally advanced non-small cell lung cancer. This study helps to benchmark efficacy and toxicity rates while considering the addition of new agents to hypofractionated concurrent chemoradiotherapy. The agreement of a standard regimen for assessment in future trials would be beneficial.  相似文献   
2.

Background

The randomized EXCEL (Evaluation of XIENCE versus Coronary Artery Bypass Surgery for Effectiveness of Left Main Revascularization) trial reported a similar rate of the 3-year composite primary endpoint of death, myocardial infarction (MI), or stroke in patients with left main coronary artery disease (LMCAD) and site-assessed low or intermediate SYNTAX scores treated with percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG). Whether these results are consistent in high-risk patients with diabetes, who have fared relatively better with CABG in most prior trials, is unknown.

Objectives

In this pre-specified subgroup analysis from the EXCEL trial, the authors sought to examine the effect of diabetes in patients with LMCAD treated with PCI versus CABG.

Methods

Patients (N = 1,905) with LMCAD and site-assessed low or intermediate CAD complexity (SYNTAX scores ≤32) were randomized 1:1 to PCI with everolimus-eluting stents versus CABG, stratified by the presence of diabetes. The primary endpoint was the rate of a composite of all-cause death, stroke, or MI at 3 years. Outcomes were examined in patients with (n = 554) and without (n = 1,350) diabetes.

Results

The 3-year composite primary endpoint was significantly higher in diabetic compared with nondiabetic patients (20.0% vs. 12.9%; p < 0.001). The rate of the 3-year primary endpoint was similar after treatment with PCI and CABG in diabetic patients (20.7% vs. 19.3%, respectively; hazard ratio: 1.03; 95% confidence interval: 0.71 to 1.50; p = 0.87) and nondiabetic patients (12.9% vs. 12.9%, respectively; hazard ratio: 0.98; 95% confidence interval: 0.73 to 1.32; p = 0.89). All-cause death at 3 years occurred in 13.6% of PCI and 9.0% of CABG patients (p = 0.046), although no significant interaction was present between diabetes status and treatment for all-cause death (p = 0.22) or other endpoints, including the 3-year primary endpoint (p = 0.82) or the major secondary endpoints of death, MI, or stroke at 30 days (p = 0.61) or death, MI, stroke, or ischemia-driven revascularization at 3 years (p = 0.65).

Conclusions

In the EXCEL trial, the relative 30-day and 3-year outcomes of PCI with everolimus-eluting stents versus CABG were consistent in diabetic and nondiabetic patients with LMCAD and site-assessed low or intermediate SYNTAX scores.(Evaluation of XIENCE versus Coronary Artery Bypass Surgery for Effectiveness of Left Main Revascularization [EXCEL]; NCT01205776)  相似文献   
3.
Our knowledge of the radiological spectrum of myelin oligodendrocyte glycoprotein antibody associated disease (MOGAD) is growing rapidly. An update on the radiological features of the disease, and its evolution is thus necessary. Magnetic resonance imaging (MRI) has an increasingly important role in the differential diagnosis of MOGAD particularly from aquaporin-4 antibody-positive neuromyelitis optica spectrum disorder (AQP4-NMOSD), and multiple sclerosis (MS). Differentiating these conditions is of prime importance because the management is different between the three inflammatory diseases, and thus could prevent further attack-related disability. Therefore, identifying the MRI features suggestive of MOGAD has diagnostic and prognostic implications. We herein review optic nerve, spinal cord and the brain MRI findings from MOGAD adult patients, and compare them to AQP4-NMOSD and MS.  相似文献   
4.

Background

Klippel-Trénaunay syndrome (KTS) is a severe vascular malformation that can lead to hypertrophic osteoarthritis. Total knee arthroplasty (TKA) performed in extremities affected with KTS is challenging given the high-risk vascular considerations and occasionally poor bone quality.

Methods

We identified 12 patients with KTS who underwent TKA between 1998 and 2017. There were 7 men, mean age 42 years, and mean follow-up was 7 years. Before arthroplasty, 2 patients (17%) had preoperative sclerotherapy. Preoperative vascular studies were done for 9 patients (75%) and included magnetic resonance imaging (n = 7), magnetic resonance angiography (n = 1), and computed tomography angiography (n = 1). A preoperative blood conservation protocol was used for all operations and included the use of tranexamic acid (TXA) in later years. Posterior-stabilized TKA was used in 10 cases and cruciate-retaining TKA was used in 2 cases.

Results

At final follow-up, 2 patients (17%) had undergone revision surgery: 1 for infection and 1 for tibial loosening with subsequent arthrofibrosis. Knee Society Scores (36-83, P < .0001) and functional scores (48-84, P = .0007) significantly increased between the preoperative and postoperative period. Likewise at last follow-up, the mean knee range of motion significantly increased (82°-104°, P = .04). Median blood loss for patients who received TXA was 200 mL compared to 275 mL in patients who did not receive TXA (P = .66). Likewise there was no difference (P = .5) in the proportion of patients who required a transfusion between those who received TXA (2/6, 33%) and those who did not (3/6, 50%).

Conclusion

In this small series, TKA can lead to significant clinical improvement for patients with KTS. Modern blood management techniques and a careful multidisciplinary care approach render TKA a reasonable option for select patients with KTS.

Level of Evidence

Level IV case series, therapeutic.  相似文献   
5.
6.

Introduction

The aim of this study was to evaluate the root canal shaping effect of instruments manufactured from nickel titanium, M-Wire, and Gold wire with different glide path preparation techniques.

Methods

One hundred thirty-five mesiobuccal canals of extracted human maxillary molars were randomly divided into 3 equal groups (N = 45) for glide path preparation with K-files (KF) (Dentsply Sirona, Ballaigues, Switzerland), One G (OG) files (Micro-Mega, Besançon, France), and ProGlider (PG) files (Dentsply Sirona). Specimens of each glide path group were further divided equally into 3 groups for instrumentation with ProTaper Next (PTN, Dentsply Sirona), One Shape (OS, Micro-Mega), and WaveOne Gold (WOG, Dentsply Sirona) systems (n = 15). Micro–computed tomographic imaging was used to scan teeth before instrumentation and after shaping to compare centering ratio and canal transportation values at the apical, midroot, and coronal levels and the overall changes in canal volume. Data sets were statistically analyzed (analysis of variance and Kruskal-Wallis H tests).

Results

The centering ratios for all groups were statistically similar at all levels. Apical canal transportation was significantly high for K/OS and K/PTN (P = .003). Midroot canal transportation was significantly high for K/PTN, K/OS, and OG/OS (P = .0003). Coronal canal transportation was significantly high for K/PTN and K/OS (P = .011). The highest change in canal volume was observed with all PTN groups and the lowest with PG/WOG (P = .06).

Conclusions

WOG manufactured from Gold wire combined with PG showed better root canal shaping ability and removed less dentin from the canal walls. The nickel-titanium (OS) and M-Wire (PTN) instruments used in combination with KF significantly transported more canals. PTN removed the most dentin from the canal walls regardless of the GPP technique.  相似文献   
7.

Background and Aims

Diet is known to play a decisive role in the development of coronary heart disease (CHD). One factor believed to decrease lifetime risk of CHD is the consumption of omega-3 fatty acids. Yet, conclusive evidence regarding the potential cardioprotective effects of fatty acids is far from being reached. The present study aimed to provide further evidence on the association of serum fatty acid profiles with CHD risk.

Methods and Results

The CARdio-vascular Disease, Living and Ageing in Halle study (CARLA study) is an observational cohort study comprising an older adult's general population with a high level of cardiovascular risk factors. In a matched case–control design the serum fatty acid concentrations of 73 subjects with an incident fatal or nonfatal CHD event were compared to 146 controls matched for sex and age. Our data show that the participants of the CARLA study are underserved in unsaturated fatty acids with respect to current dietary recommendations. In addition, the ratio of omega-6 to omega-3 fatty acids was determined to be 8:1 which underlines the consumption of a Western-style diet enriched in omega-6 fatty acids. There were no significant differences in fatty acid patterns between cases and controls. Thus, no clear association of particular serum fatty acid levels with cardiovascular risk was found.

Conclusion

Our results support the conclusion that in populations with a homogenous low level of omega-3 polyunsaturated fatty acids consumption, serum fatty acid levels are not associated with CHD risk.  相似文献   
8.

Objective

This study assessed the association between the timing of first epinephrine administration (EA) and the neurological outcomes following out-of-hospital cardiac arrests (OHCAs) with both initial shockable and non-shockable rhythms.

Methods

This was a post-hoc analysis of a multicenter prospective cohort study (SOS-KANTO 2012), which registered OHCA patients in the Kanto region of Japan from January 2012 to March 2013. We included consecutive adult OHCA patients who received epinephrine. The primary result included 1-month favorable neurological outcomes defined as cerebral performance category (CPC) 1 or 2. Secondary results included 1-month survival and return of spontaneous circulation (ROSC) after arrival at the hospital. Multivariable logistic regression analysis determined the association between delay per minute of the time from call to first EA in both pre- or in-hospital settings and outcomes.

Results

Of the 16,452 patients, 9344 were eligible for our analyses. In univariable analysis, the delay in EA was associated with decreased favorable neurological outcomes only when the initial rhythm was a non-shockable rhythm. In multivariable analyses, delay in EA was associated with decreased ROSC (adjusted odds ratio [OR] for one minute delay, 0.97; 95% confidence interval [CI], 0.96–0.98) and 1-month survival (adjusted OR, 0.95; 95% CI, 0.92–0.97) when the initial rhythm was a non-shockable rhythm, whereas during a shockable rhythm, delay in EA was not associated with decreased ROSC and 1-month survival.

Conclusions

While assessing the effectiveness of epinephrine for OHCA, we should consider the time-limited effects of epinephrine. Additionally, consideration of early EA based on the pathophysiology is needed.  相似文献   
9.
Perinatal hypoxic-ischemic encephalopathy is a leading cause of neonatal death and disability.Therapeutic hypothermia significantly reduces death and major disability associated with hypoxic-ischemic encephalopathy;however,many infants still experience lifelong disabilities to movement,sensation and cognition.Clinical guidelines,based on strong clinical and preclinical evidence,recommend therapeutic hypothermia should be started within 6 hours of birth and continued for a period of 72 hours,with a target brain temperature of 33.5 ±0.5℃ for infants with moderate to severe hypoxic-ischemic encephalopathy.The clinical guidelines also recommend that infants be re warmed at a rate of 0.5℃ per hour,but this is not based on strong evidence.There are no randomized controlled trials investigating the optimal rate of rewarming after therapeutic hypothermia for infants with hypoxic-ischemic encephalopathy.Preclinical studies of rewarming are conflicting and results were confounded by treatment with sub-optimal durations of hypothermia.In this review,we evaluate the evidence for the optimal start time,duration and depth of hypothermia,and whether the rate of rewarming after treatment affects brain injury and neurological outcomes.  相似文献   
10.

Background and aim

The associations of long-term exposure to particulate matter <10 μm in size (PM10), nitrogen dioxide (NO2), carbon monoxide (CO), sulfur dioxide (SO2), and ozone (O3) with cardiometabolic diseases (CMD) remain uncertain in the Korean population. Therefore, we sought to examine the associations between PM10, NO2, CO, SO2, and O3 and CMD using data collected from the Korean Community Health Survey.

Methods and results

We selected 100,867 adults aged 19 years or older who had lived in the same domicile for ≥10 years and surveyed them to collect data on socioeconomic characteristics; health-related behaviors; obesity; and physician-diagnosed CMD history, including hypertension, diabetes mellitus, dyslipidemia, stroke, myocardial infarction, and ischemic heart disease. We calculated interquartile ranges for PM10, NO2, CO, SO2, and O3 from the 10 year average concentrations (2003–2012). Hypertension, diabetes mellitus, and dyslipidemia were positively associated with PM10, NO2, CO, SO2, and O3 after adjusting for confounding factors. Obesity was positively associated with PM10, NO2, SO2, and O3. On the other hand, we found no associations between stroke, myocardial infarction, and ischemic heart disease and exposure to PM10, NO2, CO, SO2, and O3 in these subjects. In subjects aged ≥65 years, the risk of dyslipidemia was markedly increased under exposure to NO2 and CO compared to subjects aged <65 years. The risk of obesity was also significantly increased under exposure to PM10 and NO2. However, sex differences in these associations were not found.

Conclusion

Long-term exposure to PM10, NO2, CO, SO2, and O3 may be a risk factor of CMD in Korean adults.  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