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   3317篇
  免费   367篇
  国内免费   38篇
耳鼻咽喉   11篇
儿科学   100篇
妇产科学   151篇
基础医学   437篇
口腔科学   53篇
临床医学   377篇
内科学   719篇
皮肤病学   25篇
神经病学   323篇
特种医学   138篇
外科学   419篇
综合类   88篇
预防医学   347篇
眼科学   58篇
药学   254篇
中国医学   18篇
肿瘤学   204篇
  2023年   29篇
  2022年   23篇
  2021年   83篇
  2020年   57篇
  2019年   81篇
  2018年   90篇
  2017年   69篇
  2016年   85篇
  2015年   110篇
  2014年   128篇
  2013年   153篇
  2012年   201篇
  2011年   223篇
  2010年   129篇
  2009年   137篇
  2008年   171篇
  2007年   175篇
  2006年   172篇
  2005年   186篇
  2004年   149篇
  2003年   138篇
  2002年   123篇
  2001年   58篇
  2000年   52篇
  1999年   58篇
  1998年   34篇
  1997年   34篇
  1996年   34篇
  1995年   24篇
  1994年   18篇
  1993年   30篇
  1992年   50篇
  1991年   45篇
  1990年   49篇
  1989年   40篇
  1988年   32篇
  1987年   40篇
  1986年   40篇
  1985年   42篇
  1984年   38篇
  1983年   18篇
  1982年   17篇
  1981年   16篇
  1980年   19篇
  1979年   24篇
  1978年   28篇
  1977年   15篇
  1975年   13篇
  1974年   19篇
  1971年   15篇
排序方式: 共有3722条查询结果,搜索用时 15 毫秒
81.
82.
BackgroundConventional catheter ablation involves prolonged exposure to ionizing radiation, potentially leading to detrimental health effects. Minimal fluoroscopy (MF) represents a safer alternative, which should be explored. Data on the safety and efficacy of this technique are limited.HypothesisOur hypothesis is that MF is of equal efficacy and safety to conventional catheter ablation with the use of fluoroscopy by performing a meta‐analysis of both randomized controlled trials (RCTs) and real‐world registry studies.MethodsPubmed and Embase were searched from their inception to July 2020 for RCTs, cohort and observational studies that assessed the outcomes of catheter ablation using a MF technique versus the conventional approach.ResultsFifteen studies involving 3795 patients were included in this meta‐analysis. There was a significant reduction in fluoroscopy and procedural time with no difference in acute success (odds ratio [OR]:0.74, 95% CI: 0.50–1.10, p = .14), long‐term success (OR:0.92, 95% CI: 0.65–1.31, p = .38), arrhythmia recurrence (OR:1.24, 95% CI: 0.75–2.06, p = .97) or rate of complications. (OR:0.83, 95% CI: 0.46–1.48, p = .65). Additionally sub‐group analysis for those undergoing catheter ablation for atrial fibrillation (AF) did not demonstrate a difference in success or complication rates (OR:0.86, 95% CI: 0.30–2.42, p = .77). Multivariate meta‐regression did not identify the presence of moderator variables.ConclusionThis updated meta‐analysis demonstrated an overall reduction in procedural and fluoroscopy time for those undergoing a minimal fluoroscopic approach. There was no significant difference in either acute or chronic success rates or complications between a MF approach and conventional approach for the management of all arrhythmias including those undergoing catheter ablation for AF.  相似文献   
83.
Given the recognition that sleep may influence obesity risk, there is increasing interest in measuring sleep parameters within obesity studies. The goal of the current analyses was to determine whether the SenseWear® Pro3 Armband (armband), typically used to assess physical activity, is reliable at assessing sleep parameters. The armband was compared with the AMI Motionlogger® (actigraph), a validated activity monitor for sleep assessment, and with polysomnography, the gold standard for assessing sleep. Participants were 20 adolescents (mean age = 15.5 years) with a mean body mass index percentile of 63.7. All participants wore the armband and actigraph on their non‐dominant arm while in‐lab during a nocturnal polysomnographic recording (600 min). Epoch‐by‐epoch sleep/wake data and concordance of sleep parameters were examined. No significant sleep parameter differences were found between the armband and polysomnography; the actigraph tended to overestimate sleep and underestimate wake compared with polysomnography. Both devices showed high sleep sensitivity, but lower wake detection rates. Bland–Altman plots showed large individual differences in armband sleep parameter concordance rates. The armband did well estimating sleep overall, with group results more similar to polysomnography than the actigraph; however, the armband was less accurate at an individual level than the actigraph.  相似文献   
84.
Conjugation of ubiquitin to proteins is activated during spermatogenesis. Ubiquitination is mediated by ubiquitin-activating enzyme (E1), ubiquitin-conjugating enzymes (UBCs or E2s), and ubiquitin protein ligases (E3s). Since we previously showed that the activated ubiquitination is UBC4 dependent, we characterized Rat100, a UBC4-dependent E3 expressed in the testis. Analysis of expressed sequence tag sequences and immunoblotting showed that Rat100 is actually a 300-kDa protein expressed mainly in the brain and testis and is similar to the human E3 identified by differential display (EDD) protein and the Drosophila hyperplastic discs gene, mutants of which cause a defect in spermatogenesis. Rat100 is induced during postnatal development of the rat testis, peaking at d 25. It is localized only in germ cells and is highly expressed in spermatocytes, moderately in round and slightly in elongating spermatids. In contrast to UBC4 whose removal from a testis extract abrogates much of the conjugation activity, immmunodepletion of Rat100 from the extracts had little effect. Rat100 therefore has a limited subset of substrates, some of which appear associated with the E3 as the immunoprecipitate containing Rat100 supported incorporation of (125)I-ubiquitin into high molecular weight proteins. Thus, Rat100 is the homolog of human EDD and likely of Drosophila hyperplastic discs. This homology, together with our results, suggests that induction of this E3 results in ubiquitination of specific substrates, some of which are important in male germ cell development.  相似文献   
85.
Follicular lymphoma international prognostic index   总被引:14,自引:14,他引:14       下载免费PDF全文
The prognosis of follicular lymphomas (FL) is heterogeneous and numerous treatments may be proposed. A validated prognostic index (PI) would help in evaluating and choosing these treatments. Characteristics at diagnosis were collected from 4167 patients with FL diagnosed between 1985 and 1992. Univariate and multivariate analyses were used to propose a PI. This index was then tested on 919 patients. Five adverse prognostic factors were selected: age (> 60 years vs 60 years), Ann Arbor stage (III-IV vs I-II), hemoglobin level (< 120 g/L vs 120 g/L), number of nodal areas (> 4 vs 4), and serum LDH level (above normal vs normal or below). Three risk groups were defined: low risk (0-1 adverse factor, 36% of patients), intermediate risk (2 factors, 37% of patients, hazard ratio [HR] of 2.3), and poor risk ( 3 adverse factors, 27% of patients, HR = 4.3). This Follicular Lymphoma International Prognostic Index (FLIPI) appeared more discriminant than the International Prognostic Index proposed for aggressive non-Hodgkin lymphomas. Results were very similar in the confirmation group. The FLIPI may be used for improving treatment choices, comparing clinical trials, and designing studies to evaluate new treatments.   相似文献   
86.
87.
Next‐generation sequencing has aided characterization of genomic variation. While whole‐genome sequencing may capture all possible mutations, whole‐exome sequencing remains cost‐effective and captures most phenotype‐altering mutations. Initial strategies for exome enrichment utilized a hybridization‐based capture approach. Recently, amplicon‐based methods were designed to simplify preparation and utilize smaller DNA inputs. We evaluated two hybridization capture‐based and two amplicon‐based whole‐exome sequencing approaches, utilizing both Illumina and Ion Torrent sequencers, comparing on‐target alignment, uniformity, and variant calling. While the amplicon methods had higher on‐target rates, the hybridization capture‐based approaches demonstrated better uniformity. All methods identified many of the same single‐nucleotide variants, but each amplicon‐based method missed variants detected by the other three methods and reported additional variants discordant with all three other technologies. Many of these potential false positives or negatives appear to result from limited coverage, low variant frequency, vicinity to read starts/ends, or the need for platform‐specific variant calling algorithms. All methods demonstrated effective copy‐number variant calling when evaluated against a single‐nucleotide polymorphism array. This study illustrates some differences between whole‐exome sequencing approaches, highlights the need for selecting appropriate variant calling based on capture method, and will aid laboratories in selecting their preferred approach.  相似文献   
88.
89.
90.

Objectives

This study is to present the diagnostic values of the novel sonographic visualization of the inferoposterior thoracic wall (VIP) and boomerang signs in detecting right pleural effusion by sonologists with little to no experience in ultrasound.

Methods

A prospective analysis of a convenience sample of patients who were assessed by junior intensive care physicians was performed. The patients all underwent computed tomography (CT) of the chest or abdomen with lung bases as part of their care regardless of indication; the results were interpreted by radiologists and were considered the gold standard. Sonography was performed to assess for the presence of the VIP and boomerang signs. Sonographic and chest radiographic findings were compared against CT results.

Results

73 patients were enrolled. The sensitivity and specificity for the VIP sign were 0.85 (95% confidence interval [CI], 0.67–0.94) and 0.86 (95% CI, 0.70–0.95). The sensitivity and specificity for the boomerang sign were 0.78 (95% CI, 0.60–0.90) and 0.87 (95% CI, 0.71–0.95). However, the sensitivity and specificity for the traditional approach of detecting an anechoic collection above the diaphragm to indicate pleural effusion were only 0.54 (95% CI, 0.37–0.71) and 0.86 (95% CI, 0.80–0.99).

Conclusions

Despite inexperience in sonography, the novel VIP and boomerang signs show high diagnostic values in detecting right pleural effusion compared to the traditional methods.  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