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   11987篇
  免费   1412篇
  国内免费   264篇
耳鼻咽喉   56篇
儿科学   184篇
妇产科学   121篇
基础医学   1476篇
口腔科学   255篇
临床医学   1009篇
内科学   2360篇
皮肤病学   139篇
神经病学   740篇
特种医学   260篇
外国民族医学   2篇
外科学   504篇
综合类   1177篇
一般理论   3篇
预防医学   3251篇
眼科学   193篇
药学   1128篇
  2篇
中国医学   163篇
肿瘤学   640篇
  2024年   33篇
  2023年   254篇
  2022年   475篇
  2021年   614篇
  2020年   504篇
  2019年   478篇
  2018年   423篇
  2017年   481篇
  2016年   450篇
  2015年   553篇
  2014年   809篇
  2013年   973篇
  2012年   750篇
  2011年   796篇
  2010年   643篇
  2009年   618篇
  2008年   599篇
  2007年   640篇
  2006年   532篇
  2005年   405篇
  2004年   372篇
  2003年   294篇
  2002年   268篇
  2001年   254篇
  2000年   196篇
  1999年   149篇
  1998年   135篇
  1997年   129篇
  1996年   124篇
  1995年   90篇
  1994年   77篇
  1993年   67篇
  1992年   77篇
  1991年   67篇
  1990年   44篇
  1989年   32篇
  1988年   38篇
  1987年   26篇
  1986年   28篇
  1985年   35篇
  1984年   20篇
  1983年   17篇
  1982年   15篇
  1981年   20篇
  1980年   19篇
  1979年   11篇
  1978年   6篇
  1977年   14篇
  1976年   3篇
  1969年   2篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
52.
ABSTRACT

Increased incidences of childhood acute leukaemia were noted among survivors of the atomic bombings of Hiroshima and Nagasaki. In Western societies, Childhood Acute Lymphoblastic Leukaemia has a distinct epidemiology peaking at 3 years old. Exposure to ionising radiation is an established hazard but it is difficult to gauge the precise risk of less than 100 mSv. Since 1983 significant leukaemia incidences have been reported among families residing near nuclear installations. The target cells (naïve neonatal lymphocytes) get exposed to multiple xenobiotic challenges and undergo extraordinary proliferation and physiological somatic genetic change. Population movements and ionising radiation are considered taking account of updated understanding of radiation biology, cancer cytogenetics and immunological diversity. Double Strand Breaks in DNA arise through metabolic generation of Reactive Oxygen Species, and nearly always are repaired; but mis-repairs can be oncogenic. Recombinant Activating Gene enzymes in rapidly dividing perinatal pre-B lymphocytes being primed for antibody diversity are targeted to Signal Sequences in the Immunoglobulin genes. off target pseudo-sequences may allow RAG enzymes to create autosomal DSBs which, when mis-repaired, become translocated oncogenes. Immunogens acting by chance at crucial stages may facilitate this. In such circumstances, oncogenic DSBs from ionising radiation are less likely to be significant.  相似文献   
53.
This program is acceptable for 24 hours of Prescribed credit by the American Academy of Family Physicians and 24 hours of Category 1 credit toward the Physician's Recognition Award of the American Medical Association. If movies are viewed, additional credits are available. Further information and registration and hotel reservation forms can be secured by writing to: Interstate Postgraduate Medical Association, PO Box 1109, Madison, WI 53701.  相似文献   
54.
Piperazine‐based ‘party pills’ containing 1‐benzylpiperazine (BZP) and 1‐(m‐trifluorophenylmethylphenyl)piperazine (TFMPP) have become increasingly popular in New Zealand and many other countries. The aim of this study was to collect data on the population prevalence and related harm from legal party pill use in New Zealand. A national household sample of 2010 people aged 13–45 years old was collected using a computer‐assisted telephone interviewing (CATI) facility. Twenty per cent of the sample had tried legal party pills and 15% had used them in the previous year. Approximately 40% of males aged 18–24 years old had used legal party pills in the past year. While most users reported fairly minor problems from use, such as insomnia (50% of last year users), some users reported potentially more serious physical problems, such as ‘vomiting’ (12%), ‘inability to urinate’ (10%), ‘chest pains’ (4%) and ‘seizures’ (0.8%). Users also reported a range of psychological problems from use such as visual hallucinations (9%), paranoia (8%) and depression (8%). Two per cent of last year users were classified as dependent on legal party pills using a short dependency scale. The extent of harms and incidences of more serious problems, suggest that stricter regulation of the sale and use of legal party pills in New Zealand may be appropriate.  相似文献   
55.
背景 两条目患者健康问卷抑郁量表(PHQ-2)作为一个简短有效的抑郁筛查工具在国外及国内广泛应用,国外主要应用在12岁以上患者的抑郁筛查(证据B级),国内主要应用在特定人群抑郁的流行病学调查,而关于一般人群的调查较少。目的 了解体检人群抑郁状况,分析抑郁状态的影响因素。方法 采用整群抽样的方法,抽取2016年4月在香港大学深圳医院体检中心的体检者(≥18岁)为调查对象,以体检者的一般信息及PHQ-2中文版(PHQ-2-C)为调查工具,收集体检者的性别、年龄、受教育程度、婚姻状态、健康状态自评、运动习惯、吸烟习惯、饮酒习惯、总体睡眠质量及女性体检者妊娠次数、生育情况、避孕方式、妇科疾病等情况。采用多因素Logistic回归分析探讨抑郁发生的影响因素。结果 共回收问卷6 560份,其中有效问卷6 518份,问卷有效回收率为99.36%,抑郁状况阳性率为3.84%(250/6 518)。不同性别、年龄、婚姻状况、健康状态自评、运动习惯、吸烟习惯、总体睡眠质量的体检者抑郁情况不同,差异均有统计学意义(P<0.05)。多因素Logistic回归分析结果显示,性别、年龄、婚姻状况、健康状态自评、运动习惯、吸烟习惯、总体睡眠质量是抑郁发生的影响因素(P<0.05)。不同生育情况、避孕方式、妇科疾病女性体检者抑郁情况比较,差异均有统计学意义(P<0.05)。结论 综合医院体检人群抑郁状况阳性率为3.84%,且女性高于男性。低龄、分居/离婚/丧偶、健康状态自评差、没有/甚少运动习惯、经常吸烟、总体睡眠质量不好是体检人群有抑郁状况的危险因素。而生育情况、避孕方式、妇科疾病会影响女性的抑郁情况。  相似文献   
56.
目的 了解新型冠状病毒肺炎流行期间德阳市民众掌握相关知识的情况、行为变化及心理状态,为政府和个体采取有效的措施提供科学依据。方法 采用网上问卷的方式调查德阳地区民众1 380人,利用SPSS 23.0软件进行统计分析。结果 人们由传统的电视、广播、报纸等途径获得相关知识发展为以电视、网络、微信、抖音等获得;除了通风及抢购口罩和消毒液以外,普遍大众都持积极行为表现,尤其是大专及以上文化程度者明显高于高中及以下文化程度者,差异有统计学意义(P<0.01);人们心理状态方面:感到恐惧和悲观失望者大专及以上学历低于高中及以下学历;担心传染、担心家人健康、心情压抑、易怒发脾气者大专及以上学历均高于高中及以下学历,差异有统计学意义(P<0.05);居民产生恐惧心理的主要原因有7项,其中传染性强、潜伏期长且具传染性、疑似病例增多、药品及防护物质缺乏等项目上大专及以上学历者所占比例均高于高中及以下学历者,差异有统计学意义(P<0.05)。结论 疫情期间,德阳民众普遍存在恐慌、焦虑、悲观等心理状态,应采取有针对性的健康教育策略和措施,对有效预防控制疾病传播非常重要,同时还要注重防止因疫情引起的心理疾病发生。  相似文献   
57.
浙江省流动人口血吸虫感染情况抽样调查及分析   总被引:3,自引:0,他引:3  
目的了解浙江省流动人口血吸虫感染情况,为制订血吸虫病防治策略提供科学依据。方法采用分层整群随机抽样法抽取19个县129个村,各调查县收集流动人口基本信息,调查来自血吸虫病疫情未控制县和疫情回升县人口与流动人口的构成比。各调查村抽取来自上述疫区人群中6~65岁流动人口100人,进行问卷调查和间接红细胞凝集试验(IHA)检查。IHA阳性者再以尼龙绢集卵孵化结合沉渣镜检法检查粪便。采用SPSS13.0统计软件对调查数据进行处理和分析。结果共收集流动人群信息3357420人,其中来自疫情未控制和疫情回升县人数303219人,占9.03%。IHA检查13898人,阳性率为2.06%(286/13898)。对276例血清学阳性者进行粪检,查出病原学阳性者7例,阳性率为2.52%(7/276)。根据来自疫区流动人群构成比及血清学、病原学调查结果推算血吸虫病血清学阳性人数约为3.35万人,病原学阳性人数约为845人。结论浙江省有血吸虫病患者输入,存在m吸虫病重新传播流行威胁。  相似文献   
58.

Summary

The prevalence of forearm fractures increased with increasing degree of urbanization for both genders in the population-based study “Cohort Norway” with more than 180,000 participants. The differences were not explained by available risk factors. Prospective studies with information on bone mineral density and falls are warranted.

Introduction

The purpose was to investigate urban-rural gradients in self-reported forearm fractures and assess the contribution of possible explanatory factors.

Methods

“Cohort Norway” comprises ten population-based surveys inviting 309,742 individuals age 20 years and older. All 181,891 participants underwent a standardized examination and answered 50 common questions, including one concerning former forearm fractures. Based on the home-addresses, participants were divided into three population density groups: cities, densely populated areas and sparsely populated areas. Analyses were limited to 149,725 participants 30 years or over with valid information on exposure and outcome. Of these, 21,627 reported having suffered a forearm fracture.

Results

The prevalence of forearm fractures increased with increasing degree of urbanization for both genders. After adjustment for age and explanatory factors, the odds ratio of having sustained a forearm fracture in men living in densely populated areas and in cities were 1.12 (95% CI, 1.04–1.21) and 1.38 (95% CI, 1.30–1.46), respectively, compared to rural areas. Similar odds ratios were observed among women.

Conclusions

Prospective studies are needed to verify whether lower bone mineral density, different lifestyle and/or more falls may explain the higher proportion of self-reported forearm fractures found in urban compared to rural areas.  相似文献   
59.
Activation of spinal N-methyl-D-aspartate (NMDA) receptors and then the nitric oxide and the arachidonic acid pathways is important in pain transmission. This study assessed the effects of the NMDA receptor channel blocker ketamine, the nitric oxide synthase inhibitor L-NAME, and the cyclooxygenase inhibitor ketoprofen in nociceptive transmission using an in vitro neonatal rat spinal cord preparation. Supramaximal electrical stimulation of the dorsal root evoked the A-fibre- and C-fibre-mediated high intensity excitatory postsynaptic potential (EPSP) in the ipsilateral ventral root. Low intensity stimulation evoked the A-fibre-mediated monosynaptic compound action potential (MSR) superimposed on the low intensity EPSP. Both the low intensity EPSP and the high intensity EPSP contain NMDA-receptor-mediated components. Only ketamine and ketoprofen depressed the synaptic responses. Ketamine depressed all three spinal reflexes with IC(50) values (with 95% CI) of 10.80 microM (5.97 to 19.54 microM) for the MSR, 8.29 microM (4.53 to 14.17 microM) for the low intensity EPSP, and 5.35 microM (3.05 to 9.40 microM) for the high intensity EPSP. Ketoprofen depressed the low intensity EPSP and the high intensity EPSP only; IC(50) values (with 95% CI) were 354.5 microM (217.5 to 576.8 microM) and 302.7 microM (174.0 to 526.7 microM), respectively. Reflexes recovered after drug washout. These data demonstrated that ketamine and ketoprofen, but not L-NAME, depressed NMDA-mediated nociceptive transmission in spinal cord preparations from neonatal rats.  相似文献   
60.
目的 研究人胆囊细胞系GBC-SD中侧群细胞(side population cells,SP)的耐药特性,并探讨其耐药机制.方法 利用流式细胞术分选SP、非SP细胞,采用MTT检测2种细胞亚群对5种化疗药物吉西他滨、顺铂、5-氟尿嘧啶、表阿霉素、米托蒽醌的药物敏感性;利用流式细胞术检测吉西他滨处理的人胆囊癌细胞系GBC-SD中SP细胞比例的变化,并通过RT-PCR、Western印迹检测SP、非SP细胞亚群中ABCG2 mRNA和蛋白的表达.结果 吉西他滨、顺铂、5-氟尿嘧啶、米托蒽醌以对胆囊癌细胞系GBC-SD的IC50浓度分别作用SP、非SP细胞亚群1 d后,SP细胞的增殖能力高于非SP细胞,两组之间的差异具有统计学意义(P<0.05),而表阿霉素处理水平的两组间差异无统计学意义(P>0.05);人胆囊癌细胞系GBC-SD经过吉西他滨处理3周后,SP细胞的比例显著升高(8.02%±0.13%比0.62%±0.08%,P<0.05),且SP细胞明显高表达ABCG2基因.结论 人胆囊癌细胞系GBC-SD中SP细胞具有类似干细胞的耐药特性,耐药基因ABCG2高表达是其耐药的重要机制.
Abstract:
Objective To investigate the drug resistance of side population cells in human gallbladder cancer cell line GBC-SD and explore its mechanism. Methods Drug sensitivity assays of 5chemotherapeutic agents were performed on side population cells (SP) and non-SP cells of GBC-SD.GBC-SD was cultured and then treated with the chemotherapeutic agent gemcitabine. The frequency of SP by FACS was measured. RT-PCR and Western blotting were used to detect the expression of AB-CG2 in both the SP and the corresponding non-SP subsets. Results After 1 d treatment with 4 chemotherapeutic agents (gemcitabine, cisplatin, 5-fluorouracil and mitoxantrone) in IC50 concentration to GBC-SD cell line, the reproductive ability of SP was higher than that of non-SP (P<0.05). However, statistical significance was not achieved when compared with epirubicin (P>0.05). The percentage of SP in GBC-SD treated with chemotherapeutic agent gemcitabine after 3 weeks was sharply elevated by FACS (8.02% ±0.13% vs 0.62% ±0.08%, P<0.05), and the expression of ABCG2mRNA and protein were increased in SP as compared with non-SP. Conclusion SP from human gallbladder cancer cell line GBC-SD, like stem cell, showed a heighten resistance to drugs. Increased expression of ABCG2 was largely responsible for the multi-drug resistance.  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