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   41821篇
  免费   4588篇
  国内免费   836篇
耳鼻咽喉   302篇
儿科学   875篇
妇产科学   547篇
基础医学   3132篇
口腔科学   1495篇
临床医学   4089篇
内科学   5311篇
皮肤病学   466篇
神经病学   3258篇
特种医学   1260篇
外国民族医学   3篇
外科学   3350篇
综合类   4740篇
现状与发展   5篇
一般理论   2篇
预防医学   7132篇
眼科学   566篇
药学   3279篇
  25篇
中国医学   4409篇
肿瘤学   2999篇
  2024年   37篇
  2023年   929篇
  2022年   911篇
  2021年   1636篇
  2020年   1739篇
  2019年   1699篇
  2018年   1691篇
  2017年   1615篇
  2016年   1473篇
  2015年   1316篇
  2014年   3103篇
  2013年   3141篇
  2012年   2507篇
  2011年   2673篇
  2010年   2041篇
  2009年   1958篇
  2008年   2214篇
  2007年   2277篇
  2006年   2037篇
  2005年   1708篇
  2004年   1404篇
  2003年   1340篇
  2002年   1029篇
  2001年   957篇
  2000年   753篇
  1999年   648篇
  1998年   447篇
  1997年   466篇
  1996年   357篇
  1995年   412篇
  1994年   358篇
  1993年   297篇
  1992年   297篇
  1991年   261篇
  1990年   221篇
  1989年   204篇
  1988年   194篇
  1987年   155篇
  1986年   123篇
  1985年   114篇
  1984年   101篇
  1983年   67篇
  1982年   65篇
  1981年   61篇
  1980年   57篇
  1979年   33篇
  1978年   29篇
  1977年   26篇
  1976年   18篇
  1975年   19篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
42.
43.
Purpose: Although hyperhomocysteinemia (Hhcy) is a risk factor for cerebral infarction, its effect on recurrent cerebral infarction is less-defined. We aimed to investigate the association of Hhcy and increased risk of recurrent cerebral infarct.

Materials and methods: From 2011 to 2013, we recruited 231 primary cerebral infarct patients that were divided to a Hhcy group (n?=?105) and a control group (n?=?126) according to plasma homocysteinemia (Hcy) levels exceeding 15?μmol/L. In this prospective study, risk factors such as gender, age, blood lipid and glucose levels, history of diabetes, high blood pressure, smoking habits and plasma Hhcy levels were determined. A three-year follow-up compared differences in cerebral infarction recurrence rates. Statistical analyses identified whether plasma Hhcy levels were an independent risk factor for recurrent cerebral infarction.

Results: Triglyceride and low-density lipoprotein (LDL) levels in the Hhcy group were significantly higher than controls, and cerebral infarct recurrence rates in the Hhcy group exceeded control subject rates through the three-year follow-up (p?=?.021, p?=?.036 and p?=?.025). Cox proportional hazards modeling showed that elevated Hhcy levels (hazard ratio [HR]?=?3.062, p?<?.001), increased age (HR?=?1.069, p?<?.01), circulating triglyceride levels (HR?=?1.686, p?=?.048), and relative National Institutes of Health Stroke (NIHSS) score (HR?=?1.068, p?=?.016) were risk factors for recurrent cerebral infarction.

Conclusions: Level of Hhcy was a risk factor for recurrent cerebral infarction. Further, particular demographic and clinical outcomes including age, relative NIHSS scores, and circulating triglyceride levels were markedly associated with the occurrence of cerebral infarction.  相似文献   

44.
45.
46.
IntroductionInherited susceptibility to lung cancer risk in never-smokers is poorly understood. The major reason for this gap in knowledge is that this disease is relatively uncommon (except in Asians), making it difficult to assemble an adequate study sample. In this study we conducted a genome-wide association study on the largest, to date, set of European-descent never-smokers with lung cancer.MethodsWe conducted a two-phase (discovery and replication) genome-wide association study in never-smokers of European descent. We further augmented the sample by performing a meta-analysis with never-smokers from the recent OncoArray study, which resulted in a total of 3636 cases and 6295 controls. We also compare our findings with those in smokers with lung cancer.ResultsWe detected three genome-wide statistically significant single nucleotide polymorphisms rs31490 (odds ratio [OR]: 0.769, 95% confidence interval [CI]: 0.722–0.820; p value 5.31 × 10-16), rs380286 (OR: 0.770, 95% CI: 0.723–0.820; p value 4.32 × 10-16), and rs4975616 (OR: 0.778, 95% CI: 0.730–0.829; p value 1.04 × 10-14). All three mapped to Chromosome 5 CLPTM1L-TERT region, previously shown to be associated with lung cancer risk in smokers and in never-smoker Asian women, and risk of other cancers including breast, ovarian, colorectal, and prostate.ConclusionsWe found that genetic susceptibility to lung cancer in never-smokers is associated to genetic variants with pan-cancer risk effects. The comparison with smokers shows that top variants previously shown to be associated with lung cancer risk only confer risk in the presence of tobacco exposure, underscoring the importance of gene-environment interactions in the etiology of this disease.  相似文献   
47.
监测数据统计分析模型在生态学研究中的应用   总被引:1,自引:1,他引:0       下载免费PDF全文
近年来,环境监测、疾病监测等各种监测网络不断健全,监测系统成为开展生态学研究的重要数据来源。监测数据类型包括了横断面数据、时间序列数据和面板数据,涉及暴露、结局和混杂3个维度。针对该数据的信息属性和结构特点,相关统计学方法逐渐发展完善,出现了一些新的方法、模型。基于数据的时空属性,本文对监测数据在生态学研究中常用模型的原理、适用条件及优劣进行了综述。  相似文献   
48.
49.

Purpose

To describe the relationship between psychosocial factors and mental health among housekeepers.

Methods

A cross-sectional study was conducted nearby all the housekeepers of Farhat-Hached teaching hospital of Sousse (Tunisia). After their oral consent, employees completed a self-administrated questionnaire including socio-demographic and lifestyle data, the Job Content Questionnaire (JCQ) evaluating psychological stress at work and the Hopkins Symptoms Checklist (HSCL-25) studying mental health.

Results

Overall, 136 cleaners were enrolled in the study, corresponding to a response rate of 89.5%. The mean age was 41.9 ± 7.7 years. According to the demand control model, 26.5% of the participants were in the situation of job-strain. The study of HSCL-25 scales revealed a positive mental health disorders in 50% of cases. The study of the psychosocial factors revealed a correlation between job-strain and urban origin (P = 0.007), high psychological demand and seniority in the cleaning sector (P = 0.030) and low decision latitude and the night work (P = 0.015). The mental health association were associated with unmarried status (P = 0.006), high psychological demand (P < 0.001), active employees (P = 0.037), and iso-strain (P = 0.013). Mental disorders were associated with a high psychological demand in the presence of a high decision latitude (OR = 9.2 [2.8–30.8]) and a job-strain in the presence of low social support (OR = 3.5 [1.2–10.4]).

Conclusion

Psychosocial factors can deteriorate seriously the mental health of workers. Their identification is the most important step in any efficient preventive strategy.  相似文献   
50.
Objective: Performance validity test (PVT) research studies commonly utilize a known-groups design, but the criterion grouping approaches within the design vary greatly from one study to another. At the present time, it is unclear as to what degree different criterion grouping approaches might impact PVT classification accuracy statistics. Method: To analyze this, the authors used three different criterion grouping approaches to examine how classification accuracy statistics of a PVT (Word Choice Test; WCT) would differ. The three criterion grouping approaches included: (1) failure of 2+ PVTs versus failure of 0 PVTs, (2) failure of 2+ PVTs versus failure of 0–1 PVT, and (3) failure of a stand-alone PVT versus passing of a stand-alone PVT (Test of Memory Malingering). Results: When setting specificity at ≥.90, WCT cutoff scores ranged from 41 to 44 and associated sensitivity values ranged from .64 to .88, depending on the criterion grouping approach that was utilized. Conclusions: When using a stand-alone PVT to define criterion group status, classification accuracy rates of the WCT were higher than expected, likely due to strong correlations between the reference PVT and the WCT. This held true even when considering evidence that this grouping approach results in higher rates of criterion group misclassification. Conversely, when using criterion grouping approaches that utilized failure of 2+ PVTs, accuracy rates were more consistent with expectations. These findings demonstrate that criterion grouping approaches can impact PVT classification accuracy rates and resultant cutoff scores. Strengths, weaknesses, and practical implications of each of the criterion grouping approaches are discussed.  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