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   12113篇
  免费   943篇
  国内免费   430篇
耳鼻咽喉   114篇
儿科学   377篇
妇产科学   510篇
基础医学   919篇
口腔科学   239篇
临床医学   1304篇
内科学   656篇
皮肤病学   58篇
神经病学   638篇
特种医学   234篇
外科学   847篇
综合类   1765篇
预防医学   2197篇
眼科学   54篇
药学   1910篇
  16篇
中国医学   1510篇
肿瘤学   138篇
  2024年   34篇
  2023年   193篇
  2022年   347篇
  2021年   646篇
  2020年   479篇
  2019年   424篇
  2018年   417篇
  2017年   466篇
  2016年   511篇
  2015年   475篇
  2014年   947篇
  2013年   1125篇
  2012年   867篇
  2011年   915篇
  2010年   700篇
  2009年   621篇
  2008年   627篇
  2007年   582篇
  2006年   465篇
  2005年   392篇
  2004年   326篇
  2003年   298篇
  2002年   204篇
  2001年   178篇
  2000年   175篇
  1999年   127篇
  1998年   126篇
  1997年   96篇
  1996年   72篇
  1995年   70篇
  1994年   73篇
  1993年   59篇
  1992年   66篇
  1991年   46篇
  1990年   42篇
  1989年   48篇
  1988年   27篇
  1987年   40篇
  1986年   15篇
  1985年   28篇
  1984年   25篇
  1983年   15篇
  1982年   22篇
  1981年   15篇
  1980年   16篇
  1979年   9篇
  1978年   9篇
  1977年   9篇
  1976年   7篇
  1973年   4篇
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
71.
The majority of winter-type seasonal affective disorder (SAD) patients complain of hypersomnia and daytime drowsiness. As human sleep is regulated by the interaction of circadian, ultradian and homeostatic processes, sleep disturbances may be caused by either one of these factors. The present study focuses on homeostatic and ultradian aspects of sleep regulation in SAD. Sleep was recorded polysomnographically in seven SAD patients and matched controls subjected to a 120-h forced desynchrony protocol. In time isolation, subjects were exposed to six 20-h days, each comprising a 6.5-h period for sleep. Patients participated while being depressed, while remitted after light therapy and in summer. Controls were studied in winter and in summer. In each condition, the data of each subject were averaged across all recordings. Thus, the influence of the effects of the circadian pacemaker on sleep was excluded mathematically. The comparison of patients with controls and with themselves in the various conditions revealed no abnormalities in homeostatic parameters: sleep stage variables, relative power spectra and time courses of power in various frequency bands across the first three non-rapid eye movement-rapid eye movement (NREM-REM) cycles showed no differences. The data suggest that homeostatic processes are not involved in the disturbance of sleep in SAD.  相似文献   
72.
Research has shown that male homosexuality tends to cluster in families and that homosexual males have, on average, a greater number of older brothers than do heterosexual males. This study investigated whether the former, between-families effect and the latter, within-families effect are additive. The subjects were 717 full siblings over age 40 reported by 343 heterosexual and homosexual male probands examined in Southern Ontario in 1994–1995. The sibling's history of legal marriage or cohabitation in a heterosexual relationship was taken as a proxy variable for sexual orientation. There were no significant findings for the female siblings. As expected, the never-married male siblings were more likely to come from the sibships of the homosexual probands, and they had a greater average number of older brothers. A bootstrapped logistic regression analysis showed that an additive model best explained the male siblings' data. The results suggest that the familial aggregation of male homosexuality cannot be explained by the birth order effect and that older brothers and family membership reflect separate influences on sexual orientation or sexual orientation-correlated behavior.  相似文献   
73.
介绍了一种新型生物组织微阵列芯片自动制备仪的研制。分析了组织微阵列制备过程中的操作任务和实现目标,进行了制备仪的结构设计和各功能模块研究开发。制备仪从结构上分为蜡块承载定位模块和三工位操作模块,控制系统的组成有操作空间精密定位子系统,组织蜡块图像识别子系统,蜡块打孔填埋作业子系统等。研制成功的制备仪样机具备了图像自动识别、精密定位、自动打孔填埋等功能,实现了生物组织微阵列芯片的自动化制备。  相似文献   
74.
颈椎钩突邻近结构薄层断面与MRI对照研究   总被引:1,自引:1,他引:1  
目的阐明颈椎钩突在薄层断面和MRI断面图像上与周围结构的毗邻关系,为颈椎退行性疾病提供影像学诊断依据。方法选取5例中国数字化可视人体(CVH)数据集中C3-C7椎体上缘清楚显示钩突的薄层断面图像,观察并测量钩突与邻近的椎动脉和颈神经的位置关系,选择对应平面的MRI断面图像对照分析。结果CVH数据集的薄层断面清晰显示颈椎钩突及其周围结构,在断面上测量并得出钩突与颈神经、钩突与椎动脉的距离的平均值,MRI清楚显示颈椎钩突及其邻近结构。结论将CVH数据集中的颈椎钩突平面的薄层断面与对应的MRI图像进行对照研究,可为颈椎病的影像学诊断和治疗提供形态学参考。  相似文献   
75.
大于胎龄儿脐血脂联素水平测定及其临床意义研究   总被引:1,自引:0,他引:1  
目的探讨血脂联素水平与大于胎龄儿发生的关系。方法研究对象为大于胎龄儿和适于胎龄儿各30例。应用酶联免疫吸附法(ELISA)测定脐血和产妇血脂联素浓度,用免疫比浊法测定甘油三酯(TG)、总胆固醇(TCH)、低密度脂蛋白-胆固醇(LDL-c)、高密度脂蛋白-胆固醇(HDL-c)的水平;并分析脐血脂联素水平与母血脂联素、新生儿性别、出生体重、体重指数、胎盘重量和血脂水平的相关性。结果①大于胎龄儿脐血浆脂联素水平低于适于胎龄儿,差异有非常显著性(P<0.01=;大于胎龄儿血TG、TCH、LDL-c、HDL-c的水平与适于胎龄儿比较差异均无显著性(P>0.05)。②大于胎龄儿血浆脂联素水平与新生儿出生体重、BM I、胎盘重量、脐血TG水平均呈显著负相关(r分别=-0.848、-0.785、-0.835,P均<0.001=,与母血脂联素水平、新生儿身长、孕前和分娩时产妇体重及其BM I、其它脐血脂成分无相关性(P>0.05)。母血脂联素水平与上述因素无相关性(P>0.05)③大于胎龄儿男婴和女婴脐血浆脂联素、血脂各成分水平比较差异均无显著性(P>0.05)。结论血脂联素水平的变化与大于胎龄儿的发生有关,测定脐血脂联素水平有助于判断大于胎龄儿的发展趋势,为早期预防糖尿病、心血管疾病等多种肥胖相关性疾病的发生开拓新的思路。  相似文献   
76.
Summary Fibroblast are responsable for the synthesis of the structural proteins of the connective tissue. A further property of these cells, their migratory ability, could be analyzed in the last years. A special form of migration is chemotaxis, which can be quantitatively measured in a modified Boyden chamber in-vitro. Using this method chemoattractive substances could be characterized, which are able to stimulate fibroblasts and tumorcells to chemotactic migration. Furthermore it could be proved, that benign and transformed cell lines react in a different manner towards these chemoattractive substances. The in-vitro results allow some hypotheses about both fibroblast migration in wound healing or chronic inflammation, and the mechanisms of tumor cell evasion in the tumor surrounding tissue or the metastasizing process in other organs.

Abkürzungen PDGF platelet derived growth factor - LTB4 Leukotrien B 4 Mit Unterstützung der Deutschen Forschungsgemeinschaft Me 766/1–3  相似文献   
77.
The caudate lobe of the liver   总被引:3,自引:0,他引:3  
Summary The caudate lobe of the liver is an independent segment straddling the right and left lobes of the liver. It is divided into 2 parts, right and left, indicated eternally by the caudate and papillary processes. It is now possible to unvestigate it by ultrasonography and computed tomography, allowing its surgical excision for tumoral disease of the superior biliary confluence.
Le lobe caudé du foie

Résumé Le lobe caudé du foie est un secteur indépendant à cheval sur les foies droit et gauche. Il est séparé en 2 parties droites et gauches, marquées extérieurement par les processus caudé et papillaire. Son exploration est actuellement possible (échographie et tomodensitométrie), ce qui autorise son exérèse chirurgicale (pathologie tumorale du confluent biliaire supérieur).
  相似文献   
78.
79.
目的探讨环氧化物酶-2(cyclooxygenase type 2,COX-2)及Ⅰ型前列腺素合成酶(membrane associated prostaglandin E-1,mPGES-1)在人颈动脉粥样硬化斑块中的表达变化及作用机制。方法收集24例人颈动脉粥样硬化斑块标本和10例肠系膜动脉标本做对照组,应用免疫组织化学及逆转录PCR方法测定COX-2及mPGES-1mRNA表达水平,Western印记方法检测COX-2及mPGES-1的蛋白表达水平。比较不同程度动脉粥样硬化组织间COX-2、mPGES-1 mRNA表达水平及蛋白表达水平。结果颈动脉粥样硬化斑块组的免疫组织化学染色检测COX-2和mPGES-1呈阳性表达,斑块组COX-2 mRNA和mPGES-1 mRNA表达与对照组相比上调,差异有统计学意义(P<0.05);COX-2及mPGES-1 mRNA上调水平相关(P<0.05);颈动脉粥样硬化斑块的COX-2蛋白表达上调水平与对照组相比差异有统计学意义(P<0.05);颈动脉粥样硬化斑块COX-2、mPGES-1 mRNA及蛋白表达水平与病理损害程度有关,差异有统计学意义(P<0.05)。结论COX-2及mPGES-1基因表达水平上调可能是进展性动脉粥样硬化损害的关键因素。  相似文献   
80.
BACKGROUND: The Shipman Inquiry recommended mortality rate monitoring if it could be 'shown to be workable' in detecting a future mass murderer in general practice. AIM: To examine the effectiveness of cumulative sum (CUSUM) charts, cross-sectional Shewhart charts, and exponentially-weighted, moving-average control charts in mortality monitoring at practice level. DESIGN OF STUDY: Analysis of Scottish routine general practice data combined with estimation of control chart effectiveness in detecting a 'murderer' in a simulated dataset. METHOD: Practice stability was calculated from routine data to determine feasible lengths of monitoring. A simulated dataset of 405,000 'patients' was created, registered with 75 'practices' whose underlying mortality rates varied with the same distribution as case-mix-adjusted mortality in all Scottish practices. The sensitivity of each chart to detect five and 10 excess deaths was examined in repeated simulations. The sensitivity of control charts to excess deaths in simulated data, and the number of alarm signals when control charts were applied to routine data were estimated. RESULTS: Practice instability limited the length of monitoring and modelling was consequently restricted to a 3-year period. Monitoring mortality over 3 years, CUSUM charts were most sensitive but only reliably achieved >50% successful detection for 10 excess deaths per year and generated multiple false alarms (>15%). CONCLUSION: At best, mortality monitoring can act as a backstop to detect a particularly prolific serial killer when other means of detection have failed. Policy should focus on changes likely to improve detection of individual murders, such as reform of death certification and the coroner system.  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