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   15191篇
  免费   1146篇
  国内免费   119篇
耳鼻咽喉   174篇
儿科学   263篇
妇产科学   109篇
基础医学   1103篇
口腔科学   207篇
临床医学   1033篇
内科学   972篇
皮肤病学   394篇
神经病学   643篇
特种医学   513篇
外科学   631篇
综合类   853篇
现状与发展   1篇
预防医学   7188篇
眼科学   120篇
药学   1788篇
  3篇
中国医学   52篇
肿瘤学   409篇
  2024年   26篇
  2023年   204篇
  2022年   424篇
  2021年   505篇
  2020年   568篇
  2019年   546篇
  2018年   506篇
  2017年   537篇
  2016年   526篇
  2015年   510篇
  2014年   1031篇
  2013年   1416篇
  2012年   982篇
  2011年   1045篇
  2010年   780篇
  2009年   765篇
  2008年   753篇
  2007年   653篇
  2006年   593篇
  2005年   462篇
  2004年   407篇
  2003年   320篇
  2002年   252篇
  2001年   227篇
  2000年   237篇
  1999年   148篇
  1998年   179篇
  1997年   150篇
  1996年   188篇
  1995年   160篇
  1994年   131篇
  1993年   108篇
  1992年   152篇
  1991年   116篇
  1990年   107篇
  1989年   87篇
  1988年   84篇
  1987年   75篇
  1986年   55篇
  1985年   78篇
  1984年   78篇
  1983年   52篇
  1982年   60篇
  1981年   38篇
  1980年   36篇
  1979年   21篇
  1978年   20篇
  1977年   19篇
  1976年   16篇
  1974年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.

Background

We have previously reported that children receive significantly less radiation exposure after abdominal and/or pelvis computed tomography (CT) scanning for acute appendicitis when performed at our children's hospital (CH) rather than at outside hospitals (OH). In this study, we compare the amount of radiation children receive from head CTs for trauma done at OH versus those at our CH.

Methods

A retrospective chart review was performed on all children transferred to our hospital after receiving a head CT for trauma at an OH between July 2012 and December 2012. These children were then blindly case matched based on date, age, and gender to children at our CH.

Results

There were 50 children who underwent head CT scans for trauma at 28 OH. There were 21 females and 29 males in each group. Average age was 7.01 ± 0.5 y at the OH and 7.14 ± 6.07 at our CH (P = 0.92). Average weight was 30.81 ± 4.69 kg at the OH and 32.69 ± 27.21 kg at our CH (P = 0.81). Radiation measures included dose length product (671.21 ± 22.6 mGycm at OH versus 786.28 ± 246.3 mGycm at CH, P = 0.11) and CT dose index (53.4 ± 2.26 mGy at OH versus 49.2 ± 12.94 mGy at CH, P = 0.56).

Conclusions

There is no significant difference between radiation exposure secondary to head CTs for traumatic injuries performed at OH and those at a dedicated CH.  相似文献   
82.
目的:了解一起食源性疾病暴发的原因.方法:采用流行病学调查及实验室分离培养确认致病原.结果:在3份病人肛试子和3份末梢水中检出有致病性大肠埃希氏菌,未检出其它致病菌.一日三餐均饮用该水的教师和家属发病率为66.67%,而在校一日只进一餐的学生发病率为26.23%,前者显著高于后者(χ2=52.63,P<0.01).当地场镇居民只用不饮此水未见发病.结论:通过流行病学调查和实验室病原学检查,证实本起疫情系一起致病性大肠埃希氏菌引起的食源性疾病暴发疫情.  相似文献   
83.
In the experimental study on the electrophysiology and functions of heart in the animal,the thorax should be opened to expose the heart, at the same time natural breathing is maintained instead of artificial breathing. The key procedure of this new method is to avoid injuring the pleural cavity, so pneumothorax can be prevented. By means of this new method some subject studies have been finished.  相似文献   
84.
目的 比较肌松监测下静脉注射罗库溴铵0.9mg/kg后60秒和4个成串刺激(train-of-four,TOF)的T1达到最大抑制程度时的气管插管条件,探讨该药理想的气管插管时机.方法 120例行择期腹腔镜胆囊切除术患者,年龄18岁~60岁,ASA Ⅰ-Ⅱ级,随机均分为两组.分别于静脉注射罗库溴铵0.9 mg/kg后60秒(A组)或T1达到最大抑制程度时(B组)行气管插管.观察并记录两组罗库溴铵起效时间(TOF的T1达到最大抑制程度的时间)、气管插管条件(Cooper's评分)、声门暴露程度(Cormack-Lehane分级)、诱导过程中的心率(heart rate,HR)和收缩压(systolic blood pressuref,SBP)变化以及术后24 h咽喉并发症(喉痛、声嘶等不适).结果 静注罗库溴铵0.9 mg/kg后66.0秒±18.1秒(95%可信区间30.2秒一101.8秒)达到T1最大抑制.B组Cooper's评分和Cormack-Lehane分级均优于A组(P相似文献   
85.
86.
87.
Purpose:?To investigate time exposure dependence of continuous millimeter wave (CW) 99?GHz radiation on Escherichia coli bacterial cell viability and metabolic activity.

Materials and methods:?Suspensions of E. coli bacterial cells with an optical density of OD660nm?=?0.1 were used for viability tests and OD660nm?=?1.0 for metabolic activity tests. These suspensions were exposed to 99?GHz CW electromagnetic radiation, generated by a Backward Wave Oscillator (BWO) tube base instrument with a horn antenna at the BWO exit, to obtain an almost ideal Gaussian beam. Calculations of the Gaussian beam show that a power of 0.2?mW/cm2 was obtained at the bacterial plane.

Results:?The experimental results show that 1 hour of exposure to 99?GHz CW electromagnetic radiation had no effect on E. coli viability and colony characterisation. In 19?h of radiation, the number of colonies forming units was half order of magnitude higher than the sham-exposed and the control. However, 19?h of exposure did not affect the E. coli metabolic activity.

Conclusions:?Exposure of E. coli to millimeter wave (MW) CW 99?GHz radiation for a short period did not affect the viability of E. coli bacterial cells. However, exposure for 19?h caused a slight proliferation but did not influence the metabolic activities of about 90 biochemical reactions that were examined. Hence, we assume that the slight proliferation (half order of magnitude) after 19?h of exposure dose not have a biological meaning.  相似文献   
88.
Abstract

Background: The majority of day laborers in the USA are Latinos. They are engaged in high-risk occupations and suffer high occupational injury rates.

Objectives: To describe on-the-job injuries reported by Latino day laborers, explore the extent that demographic and occupational factors predict injuries, and whether summative measures for total job types, job conditions, and personal protective equipment (PPE) predict injuries.

Methods: A community survey was conducted with 327 participants at 15 corners in Houston, Texas. Hierarchical and multiple logistic regressions explored predictors of occupational injury odds in the last year.

Results: Thirty-four percent of respondents reported an occupational injury in the previous year. Education, exposure to loud noises, cold temperatures, vibrating machinery, use of hard hats, total number of job conditions, and total PPE significantly predicted injury odds.

Conclusion: Risk for injury among day laborers is not only the product of a specific hazard, but also the result of their exposure to multiple occupational hazards.  相似文献   
89.
Abstract

Objectives: To describe the epidemiological and clinical characteristics of an outbreak of occupational silicosis and the associated working conditions.

Methods: Cases were defined as men working in the stone cutting, shaping, and finishing industry in the province of Cádiz, diagnosed with silicosis between July 2009 and May 2012, and were identified and diagnosed by the department of pulmonology of the University Hospital of Puerto Real (Cádiz). A census of workplaces using quartz conglomerates was carried out to determine total numbers of potentially exposed workers. A patient telephone survey on occupational exposures and a review of medical records for all participants were conducted.

Results: Silicosis was diagnosed in 46 men with a median age of 33 years and a median of 11 years working in the manufacturing of countertops. Of these cases, 91·3% were diagnosed with simple chronic silicosis, with an abnormal high-resolution computerized tomography (HRCT) scan. One patient died during the study period. Employer non-compliance in prevention and control measures was frequently reported, as were environmental and individual protection failures.

Conclusions: The use of new construction materials such as quartz conglomerates has increased silicosis incidence due to intensive occupational exposures, in the context of high demand fuelled by the housing boom. This widespread exposure poses a risk if appropriate preventive measures are not undertaken.  相似文献   
90.
Abstract

Polychlorinated biphenyls (PCBs) are a group of persistent organic pollutants with the ability to cause adverse impacts on human health and the environment. This study describes the indiscriminate use of PCB-contaminated transformer oil as a coolant in informal welding shops in Kalutara, Sri Lanka. Sixty-three welders, one each from a convenience sample of 63 welding workshops participated in the study. We administered a questionnaire and observed work practices. Sixty-two (98%) workplaces used transformer oil as the coolant in the welding equipment, 60 (95%) claiming that it was the only one available. Sixty-two (98%) did not use any protective measures when refilling coolant oil, while none of them safely disposed of the empty coolant oil containers. Only four (6%) were aware of the possible health effects of PCB-contaminated coolant oil. Health and safety measures in the work places studied were very poor. Coolant oil samples from a sub-sample of 30 welding workshops were tested for PCBs; 19 (63%) were positive. PCB-contaminated coolant oil is widely used by the welders in Kalutara without adequate precautions or safety measures.  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