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   2393篇
  免费   158篇
  国内免费   19篇
耳鼻咽喉   15篇
儿科学   42篇
妇产科学   18篇
基础医学   261篇
口腔科学   51篇
临床医学   198篇
内科学   620篇
皮肤病学   52篇
神经病学   219篇
特种医学   124篇
外科学   456篇
综合类   8篇
一般理论   1篇
预防医学   149篇
眼科学   59篇
药学   137篇
中国医学   8篇
肿瘤学   152篇
  2023年   34篇
  2022年   111篇
  2021年   174篇
  2020年   79篇
  2019年   108篇
  2018年   96篇
  2017年   79篇
  2016年   96篇
  2015年   99篇
  2014年   120篇
  2013年   154篇
  2012年   205篇
  2011年   205篇
  2010年   124篇
  2009年   102篇
  2008年   130篇
  2007年   131篇
  2006年   122篇
  2005年   105篇
  2004年   91篇
  2003年   69篇
  2002年   47篇
  2001年   11篇
  2000年   17篇
  1999年   4篇
  1998年   9篇
  1997年   10篇
  1995年   2篇
  1994年   2篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1982年   1篇
  1980年   2篇
  1979年   3篇
  1978年   2篇
  1976年   1篇
  1975年   2篇
  1974年   1篇
  1973年   2篇
  1971年   3篇
  1969年   3篇
  1967年   2篇
  1965年   1篇
  1964年   1篇
  1960年   1篇
  1942年   1篇
排序方式: 共有2570条查询结果,搜索用时 15 毫秒
1.

Background

Available models for predicting lymph node invasion (LNI) in prostate cancer (PCa) patients undergoing radical prostatectomy (RP) might not be applicable to men diagnosed via magnetic resonance imaging (MRI)-targeted biopsies.

Objective

To assess the accuracy of available tools to predict LNI and to develop a novel model for men diagnosed via MRI-targeted biopsies.

Design, setting, and participants

A total of 497 patients diagnosed via MRI-targeted biopsies and treated with RP and extended pelvic lymph node dissection (ePLND) at five institutions were retrospectively identified.

Outcome measurements and statistical analyses

Three available models predicting LNI were evaluated using the area under the receiver operating characteristic curve (AUC), calibration plots, and decision curve analyses. A nomogram predicting LNI was developed and internally validated.

Results and limitations

Overall, 62 patients (12.5%) had LNI. The median number of nodes removed was 15. The AUC for the Briganti 2012, Briganti 2017, and MSKCC nomograms was 82%, 82%, and 81%, respectively, and their calibration characteristics were suboptimal. A model including PSA, clinical stage and maximum diameter of the index lesion on multiparametric MRI (mpMRI), grade group on targeted biopsy, and the presence of clinically significant PCa on concomitant systematic biopsy had an AUC of 86% and represented the basis for a coefficient-based nomogram. This tool exhibited a higher AUC and higher net benefit compared to available models developed using standard biopsies. Using a cutoff of 7%, 244 ePLNDs (57%) would be spared and a lower number of LNIs would be missed compared to available nomograms (1.6% vs 4.6% vs 4.5% vs 4.2% for the new nomogram vs Briganti 2012 vs Briganti 2017 vs MSKCC).

Conclusions

Available models predicting LNI are characterized by suboptimal accuracy and clinical net benefit for patients diagnosed via MRI-targeted biopsies. A novel nomogram including mpMRI and MRI-targeted biopsy data should be used to identify candidates for ePLND in this setting.

Patient summary

We developed the first nomogram to predict lymph node invasion (LNI) in prostate cancer patients diagnosed via magnetic resonance imaging-targeted biopsy undergoing radical prostatectomy. Adoption of this model to identify candidates for extended pelvic lymph node dissection could avoid up to 60% of these procedures at the cost of missing only 1.6% patients with LNI.  相似文献   
2.
3.
The Spanish registry of alpha-1 antitrypsin deficiency was founded in 1993 and became a member of the International Registry (AIR) in 1999. We describe the updating process following its incorporation into AIR and compare the data collected in the first period (1993–1999) and the second period (1999–2005), during which time patients were included exclusively by internet.The registry included 301 patients during period 1, 69% males and 46% had a history of smoking. Their mean age was 46 years (SD = 13) and 284 (94%) had the ZZ phenotype, 49% received augmentation therapy. During period 2, 161 new cases were included, 63% of whom were males with a mean age of 44 years (SD = 16). A total of 126 (78%) had the ZZ phenotype. Only 12% received augmentation therapy. A total of 462 different patients were included in both periods. Significant differences were observed in the number of cases with the SZ phenotype and the severity of FEV1 impairment between the two periods.Implementation of an internet-based collection of data did not result in a lower rate of reporting to the registry. However, data from a significant number of patient included in period 1 could not be actualized in the new data base.  相似文献   
4.
Studies performed to date have shown that electrical stimulation of the stomach and intestines can create or modulate motility functions in the gastrointestinal (GI) tract. Therefore, electrical stimulation of GI organs may become a valuable alternative to medication and surgical approaches in the treatment of GI motor dysfunctions. However, the mechanisms underlying the effects induced by electrical stimulation of the gut wall are not totally understood, and such knowledge is important for further development of stimulation methods and devices. Presently, it is known that electrical stimulation of GI organs triggers complex reactions comprising excitatory and inhibitory responses of the excitable components performing or controlling motility in the GI tract. I present here a review of what is known of the mechanisms of GI organ stimulation.  相似文献   
5.
Increased risk of Alzheimer's disease (AD) has been associated with polymorphisms in the IL-1 gene cluster, and in particular with the IL-1alpha-889 T/T genotype. However, this association is still unclear, and needs further investigation. In order to clarify the role of these polymorphisms in the complex pathogenesis of AD we examined genotype and haplotype frequencies of the two C-to-T SNPs at position -889 and -551 in the IL-1alpha and IL-1beta genes, respectively, and of the 86 bp VNTR intron-2 polymorphisms in the IL-1Ra gene. The analysis was performed in two genetically and diagnostically distinct groups of sporadic AD from Italy and the USA. In the Italian group a significant association between the IL-1alpha-889 T/T genotype and AD (OR=3.022, 95% CI: 1.001-9.119) was found, whereas no difference was found in the group from the USA. Results were also compared with previously published studies that analyzed the same IL-1 polymorphisms in AD. In both groups, the analysis of the estimated haplotypes shows that AD patients and controls who carry the IL-1beta-511 C allele, were also more frequently carriers of the IL-1Ra 1 allele (haplotypes -C-1). The total frequency of the two -C-1 haplotypes (C-C-1 plus T-C-1) was about one half of the total frequency of the eight estimated haplotypes. This was confirmed by significant linkage disequilibrium between these two loci in both the Italian and USA groups. In the Italian group a weak association of the T-C-2 haplotype with the disease (OR=1.648, 95% CI: 1.519-1.788) was also found, whereas in the USA group no difference was found. Although ours and other published data on different samples of Caucasian and non-Caucasian AD show a great heterogeneity in the frequencies of the IL-1alpha-889, the IL-1beta-511 and the IL-1Ra VNTR gene polymorphisms, we confirm the role of the IL-1alpha-889 T/T genotype as a risk factor for sporadic AD, and show the presence of an allelic association between IL-1beta C and IL-1Ra 1 alleles in both the Italian and the USA groups, confirmed by the presence of significant levels of linkage disequilibrium between these two loci.  相似文献   
6.
Abstract

Context: Africa’s role in the narrative of human evolution is indisputably emphasised in the emergence of Homo sapiens. However, once humans dispersed beyond Africa, the history of those who stayed remains vastly under-studied, lacking the proper attention the birthplace of both modern and archaic humans deserves. The sequencing of Neanderthal and Denisovan genomes has elucidated evidence of admixture between archaic and modern humans outside of Africa, but has not aided efforts in answering whether archaic admixture happened within Africa.

Objectives: This article reviews the state of research for archaic introgression in African populations and discusses recent insights into this topic.

Methods: Gathering published sources and recently released preprints, this review reports on the different methods developed for detecting archaic introgression. Particularly it discusses how relevant these are when implemented on African populations and what findings these studies have shown so far.

Results: Methods for detecting archaic introgression have been predominantly developed and implemented on non-African populations. Recent preprints present new methods considering African populations. While a number of studies using these methods suggest archaic introgression in Africa, without an African archaic genome to validate these results, such findings remain as putative archaic introgression.

Conclusion: In light of the caveats with implementing current archaic introgression detection methods in Africa, we recommend future studies to concentrate on unravelling the complicated demographic history of Africa through means of ancient DNA where possible and through more focused efforts to sequence modern DNA from more representative populations across the African continent.  相似文献   
7.

Objective

To describe the scientific production in medical education in Latin America in Scopus, in the period 2011-2015.

Methods

Bibliometric cross-sectional study. A search of scientific papers for the period 2011-2015 was carried out in Scopus, using terms related to medical education and specifying that at least one author should be affiliated with a Latin American country. Each paper was reviewed to select original papers that have studied medical education topics. Finally, its features were recorded and analysed using Microsoft Excel 2010.

Results

In the period 2011 - 2015, a total of 850 original medical education papers were published with authors from Latin America in Scopus, of which 49.1% had an author from Brazil. The number of publications per year was stationary. The most frequent study population were medical students (54.0%). The most frequent topic was the evaluation of competences (30.7%). Of the papers found, 21.1% were of international collaboration, but there was little (4.1%) collaboration with authors from other Latin American countries.

Conclusions

Research in medical education in Latin America in the period 2011-2015 is still deficient and stationary. The main topic was the assessment of competences, while the most frequent studied population were medical students. International collaboration was low, and collaboration among Latin American countries was lower than collaboration with countries outside Latin America.  相似文献   
8.
With combination of C and G banding techniques, three morphologically different types of isochromosome for the long arm of X (Xqi) have been identified, i.e. those with one C-band and symmetrical banding patterns of both arms, those with two C-bands and symmetrical banding patterns of two arms, and those with two C-bands but with asymmetrical banding patterns of two arms. The last type is a heterogeneous group with various different asymmetrical patterns. We have studied 6 cases of Xqi with C, G, and Q banding: 3 showed one C-band and symmetrical arms and all these were without 45,X mosaicism; the other 3 cases showed two C-bands, 2 of the cases having symmetrical arms and being mosaic for 45X/46,XXqi/47,XXqiXqi (those 2 were a pair of identical twins). One other had asymmetrical arms and was mosaic for 45,X/46,XXqi. Including our 6 cases, there have been a total of 30 reported cases of Xqi with C and G banding studies. Two-thirds of Xqi's were found to have 2 C-bands and one-third to have 1 C-band. Mosaicism was found in 85% of Xqi's with 2 C-bands and in only 44% of Xqi's with 1 C-band. Apparently, Xqi's with 2 C-bands have a greater tendency for anaphase lag and mitotic nondisjunction. Several possible mechanisms for the formation of the different types of Xqi's are discussed.  相似文献   
9.
BackgroundWe aim to evaluate the impact of multiparametric magnetic resonance imaging and fusion-target biopsy for early reclassification of patients with low-risk Prostate Cancer in a randomized trial.Materials and methodsBetween 2015 and 2018, patients diagnosed with Prostate Cancer after random biopsy fulfilling PRIAS criteria were enrolled and centrally randomized (1:1 ratio) to study group or control group. Patients randomized to study group underwent multiparametric magnetic resonance imaging at 3 months from enrollment: patients with positive findings (PIRADS-v2>2) underwent fusion-target biopsy; patients with negative multiparametric magnetic resonance imaging or confirmed ISUP - Grade Group 1 at fusion-target biopsy were managed according to PRIAS schedule and 12-core random biopsy was performed at 12 months. Patients in control group underwent PRIAS protocol, including a confirmatory 12-core random biopsy at 12 months. Primary endpoint was a reduction of reclassification rate at 12-month random biopsy in study group at least 20% less than controls. Reclassification was defined as biopsy ISUP Grade Group 1 in >2 biopsy cores or disease upgrading.ResultsA total of 124 patients were randomized to study group (n = 62) or control group (n = 62). Around 21 of 62 patients (34%) in study group had a positive multiparametric magnetic resonance imaging, and underwent fusion-target biopsy, with 11 (17.7%) reclassifications. Considering the intention-to-treat population, reclassification rate at 12-month random biopsy was 6.5% for study group and 29% for control group, respectively (P < 0.001).ConclusionsThe early employment of multiparametric magnetic resonance imaging for active surveillance patients enrolled after random biopsy consents to significantly reduce reclassifications at 12-month random biopsy.  相似文献   
10.
BackgroundThe NCCN guidelines recommend active surveillance (AS) as an option for the initial management of cT1a 0-2 cm renal lesions. However, data about comparison between renal cell carcinoma (RCC) 0-2 cm vs. 2.1-4 cm are scarce.MethodsWithin the Surveillance, Epidemiology, and End Results database (2002–2016), 46,630 T1a NanyMany stage patients treated with nephrectomy were identified. Data were tabulated according to histological subtype, tumor grade (low [LG] vs. high [HG]), as well as age category and gender. Additionally, rates of synchronous metastases were quantified.ResultsOverall, 69.3 vs. 74.1% clear cell, 21.4 vs. 17.6% papillary, 6.9 vs. 6.8% chromophobe, 2.0 vs. 1.1% sarcomatoid dedifferentiation, 0.2 vs. 0.2% collecting duct histological subtype were identified for respectively 0-2 cm and 2.1-4 cm RCCs. In both groups, advanced age was associated with higher rate of HG clear cell and HG papillary histological subtype. In 0-2 cm vs. 2.1-4 cm RCCs, 13.8% vs. 20.2% individuals operated on harbored HG tumors and were more prevalent in males. Lower synchronous metastases rates were recorded in 0-2 cm RCC and ranged from 0 in respectively multilocular cystic to 0.9% in HG papillary histological subtype. The highest synchronous metastases rates were recorded in sarcomatoid dedifferentiation histological subtype (13.8% and 9.7%) in both groups.ConclusionsRelative to 2.1-4 cm RCCs, 0-2 cm RCCs harbored lower rates of HG tumors, lower rates of aggressive variant histology and lower rates of synchronous metastases. The indications and demographics of patients selected for AS may be expanded in the future to include younger and healthier patients.  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