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   4002篇
  免费   375篇
  国内免费   53篇
耳鼻咽喉   33篇
儿科学   151篇
妇产科学   88篇
基础医学   488篇
口腔科学   34篇
临床医学   427篇
内科学   695篇
皮肤病学   59篇
神经病学   248篇
特种医学   374篇
外科学   425篇
综合类   344篇
一般理论   1篇
预防医学   390篇
眼科学   47篇
药学   330篇
  3篇
中国医学   103篇
肿瘤学   190篇
  2022年   32篇
  2021年   62篇
  2020年   57篇
  2019年   42篇
  2018年   40篇
  2017年   65篇
  2016年   44篇
  2015年   67篇
  2014年   86篇
  2013年   114篇
  2012年   173篇
  2011年   189篇
  2010年   139篇
  2009年   140篇
  2008年   193篇
  2007年   201篇
  2006年   178篇
  2005年   172篇
  2004年   114篇
  2003年   116篇
  2002年   103篇
  2001年   120篇
  2000年   115篇
  1999年   97篇
  1998年   82篇
  1997年   66篇
  1996年   76篇
  1995年   57篇
  1994年   58篇
  1993年   54篇
  1992年   60篇
  1991年   71篇
  1990年   76篇
  1989年   78篇
  1988年   74篇
  1987年   74篇
  1986年   49篇
  1985年   56篇
  1984年   58篇
  1983年   28篇
  1981年   22篇
  1980年   30篇
  1979年   30篇
  1977年   23篇
  1959年   41篇
  1958年   66篇
  1957年   75篇
  1956年   73篇
  1955年   83篇
  1954年   51篇
排序方式: 共有4430条查询结果,搜索用时 0 毫秒
1.
目的调查宁波市北仑区0~14岁儿童哮喘发病率、发病规律及危险因素,为制定防治措施提供参考。方法2013年1月-2014年1月,采用整群抽样法抽取北仑区19所学校0~14岁儿童为调查对象进行问卷调查,对筛查出的疑似哮喘儿童进行确诊,并对其人口学特征进行分析,采用logistic回归方程分析危险因素。结果调查收回有效问卷23 781份,共检出哮喘患儿534例,发病率为2.25%,男女发病率比例为1.92:1。其中发病较轻患儿占44.01%,中度占31.46%,重度占24.53%。发病时间以换季、冬季为主,分别占35.96%、32.02%。多因素logistic回归分析显示,呼吸道感染、药物过敏史、家族过敏史和食物过敏史是儿童哮喘发病的危险因素(P<0.05)。结论北仑区儿童哮喘发病率较高,具有性别和季节发病差异,应加大对患病危险因素的宣传,规范标准化治疗方案,减少儿童哮喘疾病的发生。  相似文献   
2.
Reactive oxygen species and human spermatozoa: physiology and pathology   总被引:20,自引:1,他引:19  
The role of reactive oxygen species (ROS) in the pathophysiology of human sperm function has been emphasized in recent years. ROS production in semen has been associated with loss of sperm motility, decreased capacity for sperm–oocyte fusion and loss of fertility. There is a current presumption that the most prolific source of ROS in sperm suspensions is an NADPH oxidase located in leukocytes or in spermatozoa which produces superoxide which is further converted to peroxide by the action of superoxide dismutase. Hydrogen peroxide has been recognized as the most toxic oxidizing species for human spermatozoa, which are very sensitive to lipid peroxidation owing to the high content of polyunsaturated fatty acids in their plasma membrane, though this is not the sole mechanism by which sperm function might be impaired by ROS. Although the excessive production of ROS is detrimental to human spermatozoa, there is a growing body of evidence which suggests that ROS are also involved in the physiological control of some sperm functions. This review focuses on the nature and source of the ROS generated by human spermataozoa as well as their operational mechanisms and their effects, which may be detrimental or beneficial.  相似文献   
3.
The percentage uptake of [123I]metaiodobenzylguanidine (MIBG) by tumors of the paraganglion system is compared with the number of neurosecretory granules (assessed by both light and electron microscopy) in the subsequently resected tumors in six patients. Iodine-123 MIBG was injected intravenously; the tumor uptake of [123I]MIBG varied between 0.001% and 0.14% of the injected dose per gram of tumor tissue at 22 hr. The number of neurosecretory granules in tissue sections was scored on a scale of I-III. A direct proportional correlation was found between the percentage uptake of [123I]MIBG by the tumor and the number of neurosecretory granules in the tissue sections but not with plasma or urinary catecholamines. This technique for imaging reflects the storage status of the tumor better than plasma and urinary catecholamine measurements.  相似文献   
4.
Radiolabelled monoclonal antibodies in oncology. III. Radioimmunotherapy   总被引:1,自引:0,他引:1  
The requirements, problems and progress of radioimmunotherapy in the management of certain malignancies are described. The future prospects using a two- or three-stage approach are promising.  相似文献   
5.
6.
7.
BACKGROUND: Functional neuroimaging studies have detected abnormal limbic and paralimbic activation to emotional probes in posttraumatic stress disorder (PTSD), but few studies have examined neurochemical mechanisms that underlie functional alterations in regional cerebral blood flow. The mu-opioid neurotransmitter system, implicated in responses to stress and suppression of pain, is distributed in and is thought to regulate the function of brain regions that are implicated in affective processing. METHODS: Here we examined the micro-opioid system with positron emission tomography and the micro-opioid receptor-selective radiotracer [11C] carfentanil in 16 male patients with PTSD and two non-PTSD male control groups, with (n = 14) and without combat exposure (n = 15). Differences in micro-opioid receptor binding potential (BP2) were detected within discrete limbic and paralimbic regions. RESULTS: Relative to healthy controls, both trauma-exposed groups had lower micro-opioid receptor BP2 in extended amygdala, nucleus accumbens, and dorsal frontal and insular cortex but had higher BP2 in the orbitofrontal cortex. PTSD patients exhibited reduced BP2 in anterior cingulate cortex compared with both control groups. Micro-opioid receptor BP2 in combat-exposed subjects without PTSD was lower in the amygdala but higher in the orbitofrontal cortex compared with both PTSD patients and healthy controls. CONCLUSIONS: These findings differentiate the general response of the micro-opioid system to trauma from more specific changes associated with PTSD.  相似文献   
8.
9.
目的:探讨大肠癌术后早期肠梗阻的诊断与治疗。方法:回顾分析在肠癌手术412例术后早期肠梗阻29例的临床资料。结果:20例经手术探查发现以机械性梗阻占多数(18/20),手术治愈18例;死亡2例,死亡原因均为延误手术时机造成;非手术治愈9例。结论:大肠癌术后早期肠梗阻虽有梗阻症状,但由于术后诸多因素的影响,大多缺乏典型机械性肠梗阻的临床表现。处理中先进行适当时间的非手术治疗,无缓解者再手术。  相似文献   
10.
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