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   4539篇
  免费   982篇
  国内免费   59篇
耳鼻咽喉   66篇
儿科学   136篇
妇产科学   85篇
基础医学   85篇
口腔科学   17篇
临床医学   1144篇
内科学   1468篇
皮肤病学   232篇
神经病学   542篇
特种医学   121篇
外科学   1014篇
综合类   9篇
预防医学   231篇
眼科学   160篇
药学   47篇
中国医学   2篇
肿瘤学   221篇
  2024年   20篇
  2023年   255篇
  2022年   33篇
  2021年   110篇
  2020年   156篇
  2019年   50篇
  2018年   242篇
  2017年   257篇
  2016年   254篇
  2015年   241篇
  2014年   335篇
  2013年   370篇
  2012年   140篇
  2011年   145篇
  2010年   287篇
  2009年   386篇
  2008年   167篇
  2007年   64篇
  2006年   126篇
  2005年   58篇
  2004年   50篇
  2003年   41篇
  2002年   63篇
  2001年   92篇
  2000年   39篇
  1999年   75篇
  1998年   89篇
  1997年   147篇
  1996年   133篇
  1995年   125篇
  1994年   97篇
  1993年   91篇
  1992年   80篇
  1991年   44篇
  1990年   31篇
  1989年   39篇
  1988年   42篇
  1987年   37篇
  1986年   34篇
  1985年   32篇
  1984年   32篇
  1983年   29篇
  1982年   32篇
  1981年   21篇
  1980年   38篇
  1978年   19篇
  1973年   21篇
  1960年   21篇
  1955年   20篇
  1954年   19篇
排序方式: 共有5580条查询结果,搜索用时 15 毫秒
101.
Generic active pharmaceutical ingredients (APIs) have been commonly used in Brazil, since 1999, but most of them are synthetic and small molecules. Recently, a large number of generic enoxaparins were introduced into the market raising concerns related to product-to-product interchangeability, efficiency, and drug counterfeiting. These drugs are produced from biological sources and their production involves complex procedures and purification processes. The present article evaluates several generic enoxaparins, structurally and pharmacologically, and compares them with the branded products. Structural analysis showed that the generic products are, indeed, quite similar to the branded products, however, this similarity cannot be extended to their pharmacological activities. The results showed that generic products must go through extensive structural, pharmacological, and clinical evaluation in order to assess their quality, efficacy and, ultimately, avoid drug counterfeiting before clinical use. Variation was also observed between the branded products, showing that such drugs must be at constant surveillance.  相似文献   
102.
Chronic immune thrombocytopenia (ITP) carries a poor prognosis in the elderly patients. Increasing evidence proposes that a subgroup of patients with chronic ITP may be more susceptible to ischemic stroke. An 84-year-old Caucasian man with multiple ischemic stroke risk factors presented with acute onset of slurred speech, confusion, and unsteady gait. Physical examination and neurologic imaging were consistent with a new left thalamic infarct. Platelet counts ranged between 40 000 × 10(9)/L and 65 000 × 10(9) /L. Antiplatelet therapy for his newly acquired stroke was not initiated considering his low platelet counts and for mildly symptomatic thrombocytopenia, and the patient was discharged home. Both hematologic and neurologic guidelines for the management of chronic ITP and stroke have contradictory goals. Although anticoagulation is mandated in acute stroke, ITP causes low platelet counts that increase bleeding complications.  相似文献   
103.
Patients with end-stage renal disease (ESRD) are known to have an elevation of a variety of abnormal thrombotic and inflammatory markers associated with high cardiovascular mortality. Vascular endothelial growth factor (VEGF) is also dysregulated in ESRD but not much is known about the serum levels of VEGF in patients with ESRD. Published reports suggest that elevated levels of VEGF may be protective to the kidney during periods of acute injury and may maintain local glomerular function. Impaired production of VEGF may lead to proteinuria, hypertension, and thrombotic microangiopathy. However, its role in chronic kidney disease or ESRD remains undefined. In our study, we analyzed blood samples of 52 patients with ESRD on stable hemodialysis regimen and measured predialysis serum levels of VEGF and compared these with blood samples obtained from 50 healthy volunteers in order to study differences between baseline levels of VEGF and also attempted to determine its role in ESRD-related cardiovascular mortality.  相似文献   
104.
Objective : To report the agreement between gray‐scale intravascular ultrasound (GS‐IVUS) and optical coherence tomography (OCT) in assessing the bioresorbable vascular scaffolds (BVS) structures and their respective reproducibility. Background : BVS are composed of an erodible polymer. Ultrasound and light signals backscattered from polymeric material differs from metallic stents using GS‐IVUS and OCT. Methods : Forty‐five patients included in the ABSORB trial were treated with a 3.0 × 18 mm BVS and imaged with GS‐IVUS 20 MHz and OCT post‐implantation. Qualitative (ISA, side‐branch struts, protrusion, and dissections) and quantitative (number of struts, lumen, and scaffold area) measurements were assessed by two investigators. The agreement and the inter‐ and intraobserver reproducibility were investigated using the kappa (κ) and the interclass correlation coefficient (ICC). Results : GS‐IVUS and OCT agreement was predominantly poor at a lesion, frame, and strut level analysis (κ and ICC <0.4) for qualitative measurements. GS‐IVUS demonstrated a reduced ability to detect cross‐sections with ISA (4.5% vs. 20.6%), side‐branch (SB) struts (6.3% vs. 7.8%), protrusions (3.2% vs. 9.6%), and dissections (0.2% vs. 9.0%) compared with OCT. GS‐IVUS reproducibility was poor–moderate (κ and ICC <0.6) except for ISA and SB‐struts (κ and ICC between 0.2 and 0.75). OCT showed an excellent reproducibility (κ and ICC > 0.75) except for the assessment of tissue protrusion (κ and ICC between 0.47 and 0.94). GS‐IVUS reproducibility was poor–moderate (ICC ≤ 0.5) in assessing the number of struts but excellent with OCT (ICC > 0.85). The reproducibility to assess lumen and scaffold areas was excellent using both techniques (ICC > 0.85). Conclusions : GS‐IVUS has a poor capacity to detect qualitative findings post‐BVS implantation and its reproducibility is low compared with OCT. The use of GS‐IVUS should be limited when assessing lumen and scaffold areas. © 2011 Wiley Periodicals, Inc.  相似文献   
105.
Introduction : An optimal fluoroscopic working view projection (OP) with all three aortic sinuses aligned is crucial during trans‐catheter aortic valve implantation (TAVI). The aim of this study was to identify simple reference projection angles, which would act as a starting point for the operator to help determine OP for patients undergoing TAVI. Methods : During the period under consideration, 50 patients underwent TAVI. Procedural data and outcomes were collected prospectively on a dedicated database. Optimal angiographic deployment angles were achieved for all patients by starting in an anteroposterior caudal 15 degrees projection and then adjusting according to the initial image, with multiple small volume contrast injections undertaken to determine when all three aortic cusps were aligned (OP). Results : OP angles for the 50 cases were plotted on a graph. After normality testing confirmed that all angles were normally distributed, regression analysis enabled a regression line to be calculated. The equation for the regression line was defined as cranial/caudal intercept ?16.4 ± 1.5 (SE of the coefficient), P < 0.0001, slope of regression line LAO/RAO + 0.53 ± 0.1 (SE of the coefficient SE), P < 0.0001). Conclusions : As the regression line and its equation represents an acceptable estimate of the true relationship between Cranial/Caudal and LAO/RAO, to determine OP while remaining close to the regression line we suggest starting in LAO = 8.9, Caudal = ?11.4 (which represent the mean values of these two variables), and then increasing the caudal angle by approximately 0.5 degrees for every increase of 1 degree of the LAO angle or decreasing the caudal angle by 0.53 degrees for every decrease of 1 degree in LAO until all three aortic sinuses are in line which represents OP. © 2012 Wiley Periodicals, Inc.  相似文献   
106.
The scaphoid is the common carpal bone to be fractured. Proper clinical and radiological evaluation is required to establish it's diagnosis. The management of acute fractures includes conservative treatment with cast in minimally displaced to open reduction and internal fixation in case of displaced ones. The established nonunion requires open reduction, bone grafting and internal fixation.  相似文献   
107.

Introduction

The influence that different concentrations of labour epidural local anesthetic have on assisted vaginal delivery (AVD) and many obstetric outcomes and side effects is uncertain. The purpose of this meta-analysis was to determine whether local anesthetics utilized at low concentrations (LCs) during labour are associated with a decreased incidence of AVD when compared with high concentrations (HCs).

Methods

We searched PubMed, Ovid EMBASE, Ovid MEDLINE, CINAHL, Scopus, clinicaltrials.gov, and Cochrane databases for randomized controlled trials of labouring patients that compared LCs (defined as ≤ 0.1% epidural bupivacaine or ≤ 0.17% ropivacaine) of epidural local anesthetic with HCs for maintenance of analgesia. The primary outcome was AVD and secondary outcomes included Cesarean delivery, duration of labour, analgesia, side effects (nausea and vomiting, motor block, hypotension, pruritus, and urinary retention), and neonatal outcomes. The odds ratios (OR) or weighted mean differences (WMD) and 95% confidence intervals (CI) were calculated using random effects modelling. An OR < 1 or a WMD < 0 favoured LCs.

Results

Eleven studies met our criteria (eight bupivacaine and three ropivacaine studies), providing 1,145 patients in the LCs group and 852 patients in the HCs group for analysis of the primary outcome. Low concentrations were associated with a reduction in the incidence of AVD (OR = 0.70; 95% CI 0.56 to 0.86; P < 0.001). There was no difference in the incidence of Cesarean delivery (OR 1.05; 95% CI 0.82 to 1.33; P = 0.7). The LCs group had less motor block (OR 3.9; 95% CI 1.59 to 9.55; P = 0.003), greater ambulation (OR 2.8; 95% CI 1.1 to 7.14; P = 0.03), less urinary retention (OR 0.42; 95% CI 0.23 to 0.73; P = 0.002), and a shorter second stage of labour (WMD ?14.03; 95% CI ?27.52 to ?0.55; P = 0.04) compared with the HCs group. There were no differences between groups in pain scores, maternal nausea and vomiting, hypotension, fetal heart rate abnormalities, five-minute Apgar scores, and need for neonatal resuscitation. One-minute Apgar scores < 7 favoured the HCs group (OR 1.53; 95% CI 1.07 to 2.21; P = 0.02), and there was more pruritus in the LCs group (OR 3.36; 95% CI 1.00 to 11.31; P = 0.05).

Conclusion

When compared with HCs of local anesthetics, the use of LCs for labour epidural analgesia reduces the incidence of AVD. This may be due to a reduction in the amount of local anesthetic used and the subsequent decrease in motor blockade. We therefore recommend the use of LCs of local anesthetics for epidural analgesia to optimize obstetric outcome.  相似文献   
108.

Purpose

Our objective was to develop and evaluate a Generic Integrated Objective Structured Assessment Tool (GIOSAT) to integrate Medical Expert and intrinsic (non-medical expert) CanMEDS competencies with non-technical skills for crisis simulation.

Methods

An assessment tool was designed and piloted using two pediatric anesthesia scenarios (laryngospasm and hyperkalemia). Following revision of the tool, we used previously recorded videos of anesthesia residents (n = 50) who managed one of two intraoperative advanced cardiac life support (ACLS) scenarios (ventricular tachycardia or ventricular fibrillation). Four independent trained raters, blinded to the residents’ level of training, analyzed the video recordings using the GIOSAT scale. Inter-rater reliability was calculated using intraclass correlations (ICCs) for single raters (single measure) and the average of the four raters (average measure), and construct validity was investigated by correlating GIOSAT scores with postgraduate year of residency (PGY).

Results

Total GIOSAT scores for the ACLS scenarios had single measure ICCs of 0.62 and average measure ICCs of 0.85. Inter-rater reliability was substantial for both Medical Expert and intrinsic competencies (single measure ICCs 0.69 and 0.62, respectively; average measure ICCs 0.90 and 0.82, respectively). We found significant correlations between PGY level and total GIOSAT score (r = 0.36; P = 0.011) and between PGY level and Medical Expert competencies (r = 0.42; P = 0.003); however, correlations were not found between PGY level and intrinsic CanMEDS competencies (r = 0.24; P = 0.09).

Conclusion

Inter-rater reliability of the total GIOSAT scores using four trained raters was substantial. Significant correlation between PGY and (i) total GIOSAT score and (ii) Medical Expert competencies supports construct validity. Evidence of validity was not obtained for intrinsic CanMEDS competencies.  相似文献   
109.

Background

Previously active in the mid-1990s, the Canadian Airway Focus Group (CAFG) studied the unanticipated difficult airway and made recommendations on management in a 1998 publication. The CAFG has since reconvened to examine more recent scientific literature on airway management. The Focus Group’s mandate for this article was to arrive at updated practice recommendations for management of the unconscious/induced patient in whom difficult or failed tracheal intubation is encountered.

Methods

Nineteen clinicians with backgrounds in anesthesia, emergency medicine, and intensive care joined this iteration of the CAFG. Each member was assigned topics and conducted reviews of Medline, EMBASE, and Cochrane databases. Results were presented and discussed during multiple teleconferences and two face-to-face meetings. When appropriate, evidence- or consensus-based recommendations were made together with assigned levels of evidence modelled after previously published criteria.

Conclusions

The clinician must be aware of the potential for harm to the patient that can occur with multiple attempts at tracheal intubation. This likelihood can be minimized by moving early from an unsuccessful primary intubation technique to an alternative “Plan B” technique if oxygenation by face mask or ventilation using a supraglottic device is non-problematic. Irrespective of the technique(s) used, failure to achieve successful tracheal intubation in a maximum of three attempts defines failed tracheal intubation and signals the need to engage an exit strategy. Failure to oxygenate by face mask or supraglottic device ventilation occurring in conjunction with failed tracheal intubation defines a failed oxygenation, “cannot intubate, cannot oxygenate” situation. Cricothyrotomy must then be undertaken without delay, although if not already tried, an expedited and concurrent attempt can be made to place a supraglottic device.  相似文献   
110.

Background

Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) have been shown to improve survival in selected patients with peritoneal carcinomatosis. We review our institutional experience with the procedure and evaluate the overall survival (OS) and disease-free survival (DFS) rates in 100 consecutive patients.

Methods

Data were prospectively collected from 100 consecutive patients with peritoneal carcinomatosis treated by CRS and HIPEC at the National Cancer Centre Singapore between April 2001 and May 2012. Our primary end points were OS and DFS.

Results

Of the 100 patients, 84 were of Chinese ethnicity, 3 were Malay, 6 were Indian, and 7 were of other ethnicities. Primary tumors were ovarian cancer (n = 39), colorectal cancer (n = 28), primary peritoneal (n = 6), appendiceal cancer (n = 20), and mesothelioma (n = 7). Median follow-up duration was 21 months. At 5 years, the DFS was 26.3 % and OS was 50.9 %. Factors influencing OS and DFS were cytoreductive score, primary cancer, and disease-free interval of more than 12 months on univariate analysis. The only factors that remained significant for prognosis after multivariate analysis were primary cancer and cytoreductive score. Thirty-day morbidity was 56 %, and there were no 30-day mortalities.

Conclusions

CRS and HIPEC can be safely carried out in Asian patients with peritoneal carcinomatosis from ovarian, colorectal, appendiceal, mesothelioma, and primary peritoneal origins. Overall, the ovarian, appendiceal, mesothelioma, and primary peritoneal cancer patients tended to do better than the colorectal patients, but careful patient selection ensuring that optimal cytoreduction can be achieved is essential for the success of this procedure.  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