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   3488篇
  免费   186篇
  国内免费   10篇
耳鼻咽喉   38篇
儿科学   69篇
妇产科学   43篇
基础医学   393篇
口腔科学   136篇
临床医学   265篇
内科学   855篇
皮肤病学   36篇
神经病学   452篇
特种医学   74篇
外科学   587篇
综合类   18篇
一般理论   1篇
预防医学   272篇
眼科学   63篇
药学   188篇
中国医学   5篇
肿瘤学   189篇
  2024年   5篇
  2023年   30篇
  2022年   67篇
  2021年   122篇
  2020年   75篇
  2019年   105篇
  2018年   108篇
  2017年   71篇
  2016年   110篇
  2015年   83篇
  2014年   154篇
  2013年   154篇
  2012年   278篇
  2011年   286篇
  2010年   155篇
  2009年   146篇
  2008年   211篇
  2007年   227篇
  2006年   211篇
  2005年   220篇
  2004年   165篇
  2003年   151篇
  2002年   143篇
  2001年   64篇
  2000年   39篇
  1999年   39篇
  1998年   20篇
  1997年   26篇
  1996年   22篇
  1995年   9篇
  1994年   8篇
  1993年   8篇
  1992年   13篇
  1991年   14篇
  1990年   15篇
  1989年   10篇
  1988年   11篇
  1987年   6篇
  1986年   15篇
  1984年   9篇
  1983年   9篇
  1982年   8篇
  1980年   5篇
  1979年   4篇
  1978年   11篇
  1977年   5篇
  1976年   8篇
  1969年   5篇
  1968年   3篇
  1965年   3篇
排序方式: 共有3684条查询结果,搜索用时 13 毫秒
71.

Background

The threat of a global pandemic posed by outbreaks of influenza H5N1 (1997) and Severe Acute Respiratory Syndrome (SARS, 2002), both diseases of zoonotic origin, provoked interest in improving early warning systems and reinforced the need for combining data from different sources. It led to the use of search query data from search engines such as Google and Yahoo! as an indicator of when and where influenza was occurring. This methodology has subsequently been extended to other diseases and has led to experimentation with new types of social media for disease surveillance.

Objective

The objective of this scoping review was to formally assess the current state of knowledge regarding the use of search queries and social media for disease surveillance in order to inform future work on early detection and more effective mitigation of the effects of foodborne illness.

Methods

Structured scoping review methods were used to identify, characterize, and evaluate all published primary research, expert review, and commentary articles regarding the use of social media in surveillance of infectious diseases from 2002-2011.

Results

Thirty-two primary research articles and 19 reviews and case studies were identified as relevant. Most relevant citations were peer-reviewed journal articles (29/32, 91%) published in 2010-11 (28/32, 88%) and reported use of a Google program for surveillance of influenza. Only four primary research articles investigated social media in the context of foodborne disease or gastroenteritis. Most authors (21/32 articles, 66%) reported that social media-based surveillance had comparable performance when compared to an existing surveillance program. The most commonly reported strengths of social media surveillance programs included their effectiveness (21/32, 66%) and rapid detection of disease (21/32, 66%). The most commonly reported weaknesses were the potential for false positive (16/32, 50%) and false negative (11/32, 34%) results. Most authors (24/32, 75%) recommended that social media programs should primarily be used to support existing surveillance programs.

Conclusions

The use of search queries and social media for disease surveillance are relatively recent phenomena (first reported in 2006). Both the tools themselves and the methodologies for exploiting them are evolving over time. While their accuracy, speed, and cost compare favorably with existing surveillance systems, the primary challenge is to refine the data signal by reducing surrounding noise. Further developments in digital disease surveillance have the potential to improve sensitivity and specificity, passively through advances in machine learning and actively through engagement of users. Adoption, even as supporting systems for existing surveillance, will entail a high level of familiarity with the tools and collaboration across jurisdictions.  相似文献   
72.
The aim of this study was to compare, by micro‐computed tomography (micro‐CT) analysis, the obturation quality of two filling methods: the single‐cone technique with the bioceramic EndoSequence BC sealer and the continuous wave technique with the resin‐based AH Plus sealer. Twenty mandibular molars were divided into two groups (n = 10) according to the sealer used. Only the mesial roots, which are known to have mostly two canals, were used. The specimens were scanned before and after instrumentation and after obturation. Root canal volume after instrumentation and filling volume were calculated to obtain the percentage volumes of filling, voids and gaps. All specimens presented final volumes that were smaller than the initial volumes (P < 0.05). There was no significant difference between groups for filling volume, voids and gaps (P > 0.05). Using two filling methods, EndoSequence BC and AH Plus promoted a similar root filling quality in mesial roots of mandibular molars. Neither sealer was able to fill the root canal system completely.  相似文献   
73.
Clinical Oral Investigations - The aim of this study was to assess in a multi-modular manner the bone healing 1&nbsp;year post root-end surgery (RES) with leukocyte- and platelet-rich fibrin...  相似文献   
74.
75.

Purpose

The treatment of adult scoliosis is a challenge especially in patients over 50 years old with severe, rigid curves in whom the use of vertebral osteotomies may be necessary to correct the deformity. The aim the study was to analyse the perioperative complications related to vertebral osteotomies in elderly treated for spinal deformity.

Methods

We analysed 72 consecutive cases of kyphoscoliosis, we classify them according to Berjano–Lamartina classification. We divided patients into two groups: we only practised SPO and/or PO in patients that composed group A; we practised also PSO in patients that composed group B. We retrospectively analysed the perioperative complications and radiographical results. Average follow-up was 30 months.

Results

We had 50 cases of degenerative segment diseases (DSD) Type III, 13 Type IVa DSD and 9 Type IVb DSD. Mean age was 60.7 years old. Overall complication rate was 22.2 %. In group A, the complication rate was 16.9 % while in group B it was 46.2 %. Mean Cobb primary curve angle was 41.75° with average C7 plumb line (C7PL) of 4.49 cm, residual scoliosis after surgery was 15.41° and average C7PL of 2.08 cm, with statistically significant differences.

Conclusions

Previous studies have shown increased complication rates with vertebral osteotomies in elderly patients, our experience support this evidence. Our study demonstrates a high incidence of intraoperative complication rate in elderly patients underwent a PSO. PSO is a demanding technique to be considered in very selected and motivated patients who must be carefully informed about the risks of the procedure.
  相似文献   
76.
Wegener's granulomatosis (WG) is a systemic necrotizing vasculitis, which could potentially affect any organ system. However, there have only been a few reports on cardiac involvement. We described the echocardiographic findings in nine patients affected by WG. A complete M-mode, two-dimensional, Doppler and color-Doppler transthoracic echocardiogram was performed in nine patients (seven females and two males) affected by WG. In each patient, cardiac abnormality, for example, valvular damage, left ventricular global systolic dysfunction, or pericardial effusion, was detected. In particular, heart valve disease was found in eight patients, and in three cases, aortic valve insufficiency, which was severe enough to require surgical valve replacement, was observed. Cardiac involvement in patients with WG is common. In particular, there is a high frequency of aortic valve abnormalities. Thus, an echocardiographic study should be routinely performed. Received: 21 October 1999 / Accepted: 28 April 2000  相似文献   
77.
78.

Objectives

This study sought to assess whether transradial access (TRA) compared with transfemoral access (TFA) is associated with consistent outcomes in male and female patients with acute coronary syndrome undergoing invasive management.

Background

There are limited and contrasting data about sex disparities for the safety and efficacy of TRA versus TFA for coronary intervention.

Methods

In the MATRIX (Minimizing Adverse Haemorrhagic Events by TRansradial Access Site and Systemic Implementation of angioX) program, 8,404 patients were randomized to TRA or TFA. The 30-day coprimary outcomes were major adverse cardiovascular and cerebrovascular events (MACCE), defined as death, myocardial infarction, or stroke, and net adverse clinical events (NACE), defined as MACCE or major bleeding.

Results

Among 8,404 patients, 2,232 (26.6%) were women and 6,172 (73.4%) were men. MACCE and NACE were not significantly different between men and women after adjustment, but women had higher risk of access site bleeding (male vs. female rate ratio [RR]: 0.64; p = 0.0016), severe bleeding (RR: 0.17; p = 0.0012), and transfusion (RR: 0.56; p = 0.0089). When comparing radial versus femoral, there was no significant interaction for MACCE and NACE stratified by sex (pint = 0.15 and 0.18, respectively), although for both coprimary endpoints the benefit with TRA was relatively greater in women (RR: 0.73; p = 0.019; and RR: 0.73; p = 0.012, respectively). Similarly, there was no significant interaction between male and female patients for the individual endpoints of all-cause death (pint = 0.79), myocardial infarction (pint = 0.25), stroke (pint = 0.18), and Bleeding Academic Research Consortium type 3 or 5 (pint = 0.45).

Conclusions

Women showed a higher risk of severe bleeding and access site complications, and radial access was an effective method to reduce these complications as well as composite ischemic and ischemic or bleeding endpoints.  相似文献   
79.
BACKGROUND: Hepatitis B virus (HBV) immune escape mutants with point mutations within the S gene may arise during the natural course of HBV infection, due to a positive selection pressure exerted by the host immune response. Mutations within the immunodominant B and T cell epitopes of hepatitis B surface antigen (HBsAg) allow the resulting S-mutants to propagate even in the presence of neutralizing anti-HBs antibodies and the HBV-specific T-cell immune response. Aim: To study the antiviral effect of Pegylated-interferon (Peg-IFN) in a patient with chronic hepatitis B carrying unusual S-(and P-) mutants in the presence of anti-HBs antibodies. PATIENTS, METHODS AND RESULTS: We report on a 43-year-old male chronically infected with a genotype A HBV strain, with cocirculation of both HBsAg and anti-HBs antibodies, who received treatment with 120 mug of Peg-IFN for 24 weeks. HBeAg seroconversion and clearance of both HBV DNA by polymerase chain reaction and HBsAg were successfully achieved. Improved histology was observed in a biopsy performed 44 weeks after Peg-IFN therapy was completed. It seems plausible that the ascribed genotype A could have contributed to the effective response to Peg-IFN, even though the treatment was provided only throughout a 24-week period. CONCLUSION: To our knowledge, this is the first report regarding the successful result obtained by using Peg-IFN as a treatment for a chronically HBV-infected patient carrying HBsAg immune escape mutants.  相似文献   
80.
The processes underlying development, refinement, and retention of the intracortical connections critical for the function of the mammalian brain are unknown. Horseradish peroxidase-labeled fibers in mouse somatosensory barrel cortex, which is patterned like the whiskers on the contralateral face from which it receives inputs, were evaluated by automated image analysis. The sensory nerve to the whiskers was sectioned on postnatal day 7, after the whisker map is set. The deprived barrel cortices, examined in adults, showed drastically diminished intracortical projections relative to normal controls, although the map of the whiskers in the cortex was unchanged. This demonstrates anatomically that the normal pattern of intracortical connections, like the normal sensory map, is dependent upon the sensory periphery four synapses away.  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