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   52061篇
  免费   3831篇
  国内免费   1214篇
耳鼻咽喉   2525篇
儿科学   531篇
妇产科学   332篇
基础医学   2614篇
口腔科学   2170篇
临床医学   4595篇
内科学   2596篇
皮肤病学   208篇
神经病学   1082篇
特种医学   2981篇
外国民族医学   2篇
外科学   19915篇
综合类   7462篇
一般理论   3篇
预防医学   1700篇
眼科学   457篇
药学   2784篇
  61篇
中国医学   1582篇
肿瘤学   3506篇
  2024年   84篇
  2023年   788篇
  2022年   1384篇
  2021年   2043篇
  2020年   2245篇
  2019年   1861篇
  2018年   1786篇
  2017年   1813篇
  2016年   2094篇
  2015年   2012篇
  2014年   4217篇
  2013年   3836篇
  2012年   3430篇
  2011年   3676篇
  2010年   2940篇
  2009年   2927篇
  2008年   2525篇
  2007年   2568篇
  2006年   2263篇
  2005年   1993篇
  2004年   1674篇
  2003年   1284篇
  2002年   1045篇
  2001年   871篇
  2000年   729篇
  1999年   653篇
  1998年   552篇
  1997年   467篇
  1996年   362篇
  1995年   319篇
  1994年   295篇
  1993年   268篇
  1992年   250篇
  1991年   226篇
  1990年   182篇
  1989年   163篇
  1988年   163篇
  1987年   154篇
  1986年   114篇
  1985年   126篇
  1984年   134篇
  1983年   104篇
  1982年   116篇
  1981年   95篇
  1980年   93篇
  1979年   51篇
  1978年   40篇
  1977年   34篇
  1976年   22篇
  1975年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
IntroductionMuch controversy exists over whether to perform lateral neck dissection (LND) on patients with papillary thyroid carcinoma (PTC). This study aimed to build predictive nomograms that could individually estimate lateral neck metastasis (LNM) risk and help determine follow up intensity.Patients and methodsUnifocal PTC patients who underwent LND between April 2012 and August 2014 were identified. Clinical and pathological variables were retrospectively evaluated using univariate and stepwise multivariate logistic regression analysis. Variables that had statistical significance in final multivariate logistic models were chosen to build nomograms, which were further corrected using the bootstrap resampling method.ResultsIn all, 505 PTC patients were eligible for analysis. Among these, 178 patients (35.2%) had lateral neck metastasis. Two nomograms were generated: nomogram (c) and nomogram (c + p). Nomogram (c) incorporated four clinical variables: age, tumor size, tumor site, and extrathyroidal extension (ETE). It had a good discriminative ability, with a C-index of 0.79 (bootstrap-corrected, 0.78). Nomogram (c + p) incorporated two clinical variables and two pathological variables: tumor size, tumor site, extranodal extension (ENE), and number of positive nodes in the central compartment. Nomogram (c + p) showed an excellent discriminative ability, with a C-index of 0.86 (bootstrap-corrected, 0.85).ConclusionTwo predictive nomograms were generated. Nomogram (c) is a clinical model, whereas nomogram (c + p) is a clinicopathological model. Each nomogram incorporates only four variables and can give an accurate estimate of LNM risk in unifocal PTC patients, which may assist clinicians in patient counseling and decision making regarding LND.  相似文献   
52.
53.
Background: Relatively few studies investigated the importance of frailty in radical cystectomy (RC) patients. We tested the ability of frailty, using the Johns Hopkins Adjusted Clinical Groups indicator, to predict early perioperative outcomes after RC.Methods: RC patients were identified within the National Inpatient Sample database (2000–2015). The effect of frailty, age and Charlson Comorbidity Index were tested in five separate multivariable models predicting: (1) complications, (2) failure to rescue (FTR), (3) in-hospital mortality, (4) length of stay (LOS) and (5) total hospital charges (THCs). All models were weighted and adjusted for clustering, as well as all available patient and hospital characteristics.Results: Of 23,967 RC patients, 5833 (24.3%) were frail, 7721 (32.2%) were aged ≥75 years and 2832 (11.8%) had CCI ≥2. Frailty, age ≥75 years and CCI ≥2 were non-overlapping in 86.3% of the cohort. Any two or three of these features were recorded in 12.4 and 1.3%, respectively. Frailty was an independent predictor of all five examined endpoints and the magnitude of its association was stronger or at least equal than that of age ≥75 years and CCI ≥2.Conclusion: Frailty, advanced age and comorbidities represent non-overlapping patients’ characteristics. Of those, frailty represents the most consistent and strongest predictor of early adverse outcomes after RC. Ideally, all three indicators should be considered in retrospective, as well as prospective analyses. Pre-surgical recognition of frail patients should be ideally incorporate in clinical practice in order to address these patients to multimodal pre-habilitation programs that may potentially improve the perioperative prognosis.  相似文献   
54.
Lingual lymph nodes are an inconstant group of in-transit nodes, which are located on the route of lymph drainage from the tongue mucosa to the regional nodes in neck levels I and II. There is growing academic data on the metastatic spread of oral cancer, particularly regarding the spreading of oral tongue squamous cell carcinoma to lingual nodes. These nodes are not currently included in diagnostic and treatment protocols for oral tongue cancer. Combined information on surgical anatomy, clinical observations, means of detection, and prognostic value is presented. Anatomically obtained incidence of lingual nodes ranges from 8.6% to 30.2%. Incidence of lingual lymph node metastasis ranges from 1.3% to 17.1%. It is clear that lymph nodes that bear intervening tissues from the floor of the mouth should be removed to improve loco-regional control. Extended resection volume, which is required for the surgical treatment of lingual node metastasis, cannot be implied to every tongue cancer patient. As these lesions significantly influence prognosis, special efforts of their detection must be made. Reasonably, every tongue cancer patient must be investigated for the existence of lingual lymph node metastasis. Lymphographic tracing methods, which are currently implied for sentinel lymph node biopsies, may improve the detection of lingual lymph nodes.  相似文献   
55.
Background and objective: X-ray repair cross-complementing group1 (XRCC1) is a key protein in base excision repair and closely associated with the coordination of the base excision repair pathway. Many studies have focused on XRCC1 SNPs and have shown an associated between these SNPs and the risk of several types of cancers, including head and neck cancer. There are many single nucleotide polymorphisms XRCC1 gene (SNPs) and the most common SNP that result in amino acid substitutions is exon 10 (Arg399Gln). This study aimed to investigate the association between Arg399Gln SNP and the risk of squamous cell carcinoma of the head and neck. Material and method: Ninety nine patients with squamous cell carcinomas of the head and neck and 89 healthy adult controls were enrolled in this study. The Arg399Gln in XRCC1 allele was genotyped using polymerase chain reaction-restriction fragment length polymorphism method. Results: In the single-locus analyses, Arg399Gln SNP showed a significant association with head and neck cancer risk (p value = 0.016 and odd ratio of 1.8). On the genotype level, we applied three analysis models, namely co-dominant, dominant, and recessive genotypes. Arg/Arg homozygous major genotype was significantly (p value <0.05) associated with head and neck squamous cell carcinoma incidence with odd ratio of 2.23 and 2.24 for the co-dominant and recessive models, respectively. Conclusion: The findings indicated that Arg399Gln allele was associated with squamous cell carcinoma of the head and neck among Jordanian patients. This allele might be used as a genetic biomarker of squamous cell carcinoma of the head and neck.  相似文献   
56.
《Heart rhythm》2022,19(7):1104-1108
  1. Download : Download high-res image (116KB)
  2. Download : Download full-size image
  相似文献   
57.
58.
LC-MS quantification of drug metabolites is sometimes impeded by the availability of internal standards that often requires customized synthesis and/or extensive purification. Although isotopically labeled internal standards are considered ideal for LC-MS/MS based quantification, de novo synthesis using costly isotope-enriched starting materials makes it impractical for early stage of drug discovery. Therefore, quick access to these isotope-enriched compounds without chemical derivatization and purification will greatly facilitate LC-MS/MS based quantification. Herein, we report a novel 18O-labeling technique using metabolizing enzyme carboxylesterase (CES) and its potential application in metabolites quantification study. Substrates of CES typically undergo a two-step oxygen exchange with H218O in the presence of the enzyme, generating singly- and doubly-18O-labeled carboxylic acids; however, unexpected hydrolytic behavior was observed for three of the test compounds – indomethacin, piperacillin and clopidogrel. These unusual observations led to the discovery of several novel hydrolytic mechanisms. Finally, when used as internal standard for LC-MS/MS based quantification, these in situ labeled compounds generated accurate quantitation comparable to the conventional standard curve method. The preliminary results suggest that this method has potential to eliminate laborious chemical synthesis of isotope-labeled internal standards for carboxylic acid-containing compounds, and can be developed to facilitate quantitative analysis in early-stage drug discovery.  相似文献   
59.
60.
《Clinical breast cancer》2020,20(6):454-461
BackgroundCoronavirus disease 2019 (COVID-19) has put a strain on regular healthcare worldwide. In the Netherlands, the national screening programs, including for breast cancer, were halted temporarily. This posed a challenge to breast cancer care, because ∼40% of cases are detected through national screening. Therefore, the aim of the present study was to evaluate the effects of the COVID-19 pandemic on the surgical care of patients with breast cancer in the Netherlands.Materials and MethodsThe present multicenter retrospective cohort study investigated the effects of COVID-19 on patients with breast cancer who had undergone surgery from March 9 to May 17, 2020. The primary endpoints were the number of surgical procedures performed during the study period, tumor characteristics, surgery type, and route of referral. The secondary endpoint was the incidence of postoperative complications during the study period.ResultsA total of 217 consecutive patients with breast cancer requiring surgery were included. We found an overall decrease in the number of patients with breast cancer who were undergoing surgery. The most significant decline was seen in surgery for T1-T2 and N0 tumors. A decline in the number of referrals from both the national screening program and general practitioners was observed. The incidence of postoperative complications remained stable during the study period.ConclusionsThe temporary halt of the national screening program for breast cancer resulted in fewer surgical procedures during the study period and a pronounced decrease in surgery of the lower tumor stages.  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