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   4435篇
  免费   269篇
  国内免费   107篇
耳鼻咽喉   51篇
儿科学   94篇
妇产科学   65篇
基础医学   581篇
口腔科学   224篇
临床医学   367篇
内科学   609篇
皮肤病学   69篇
神经病学   439篇
特种医学   156篇
外科学   431篇
综合类   506篇
预防医学   312篇
眼科学   127篇
药学   374篇
中国医学   218篇
肿瘤学   188篇
  2023年   62篇
  2022年   89篇
  2021年   176篇
  2020年   112篇
  2019年   108篇
  2018年   125篇
  2017年   128篇
  2016年   122篇
  2015年   108篇
  2014年   229篇
  2013年   291篇
  2012年   234篇
  2011年   218篇
  2010年   175篇
  2009年   179篇
  2008年   179篇
  2007年   159篇
  2006年   168篇
  2005年   124篇
  2004年   139篇
  2003年   114篇
  2002年   93篇
  2001年   99篇
  2000年   71篇
  1999年   81篇
  1998年   79篇
  1997年   81篇
  1996年   49篇
  1995年   53篇
  1994年   46篇
  1993年   62篇
  1992年   63篇
  1991年   47篇
  1990年   66篇
  1989年   54篇
  1988年   57篇
  1987年   42篇
  1986年   38篇
  1985年   71篇
  1984年   64篇
  1983年   36篇
  1982年   51篇
  1981年   52篇
  1980年   48篇
  1979年   34篇
  1978年   28篇
  1977年   22篇
  1976年   30篇
  1975年   15篇
  1974年   8篇
排序方式: 共有4811条查询结果,搜索用时 15 毫秒
61.
The age‐dependent penetrance of organ manifestations in Marfan syndrome (MFS) is not known. The aims of this follow‐up study were to explore how clinical features change over a 10‐year period in the same Norwegian MFS cohort. In 2003–2004, we investigated 105 adults for all manifestations in the 1996 Ghent nosology. Ten years later, we performed follow‐up investigations of the survivors (n = 48) who consented. Forty‐six fulfilled the revised Ghent criteria. Median age: females 51 years, range 32–80 years; males 45 years, range 30–67 years. New aortic root dilatation was detected in patients up to 70 years. Ascending aortic pathology was diagnosed in 93 versus 72% at baseline. Sixty‐five percent had undergone aortic surgery compared to 39% at baseline. Pulmonary trunk mean diameter had increased significantly compared to baseline. From inclusion to follow‐up, two patients (three eyes) developed ectopia lentis, four developed dural ectasia, four developed scoliosis, three developed incisional or recurrent herniae, and 14 developed hindfoot deformity. No changes were found regarding protrusio acetabuli, spontaneous pneumothorax, or striae atrophicae. The study confirms that knowledge of incidence and progression of organ manifestations throughout life is important for diagnosis, treatment, and follow‐up of patients with verified or suspected MFS.  相似文献   
62.
A within-subjects design was used to assess age changes in cerebellar Purkinje neurons. Four groups of naive male Sprague-Dawley rats, aged 3, 10, 20, and 28 months, underwent single cell recording for electrophysiological assessment of Purkinje cell firing patterns, followed by perfusion for glyoxylic acid induced catecholamine fluorescence. Cerebellar sections were photographed first by fluorescence microscope for catecholamines, and 2–3 weeks later for quantification of lipofuscin autofluorescence. Finally, these same tissues were treated with cresyl violet and photographed a third time to permit quantitative estimates of age changes in the number of Nissl staining Purkinje neurons. Electrophysiological studies revealed significant effects of age on a number of Purkinje cell firing parameters: in particular, increasing numbers of aberrant, very slow-firing cells were encountered in older animals. These cells showed normal climbing fiber mediated burst activity, but spontaneous simple spike firing rates 3–5 times less than normal. Rats exhibiting the highest numbers of such abnormal cells also exhibited the poorest Nissl staining. Conversely, good Nissl staining of Purkinje neurons in an old rat was a reliable predictor of relatively normal Purkinje cell firing. Lipofuscin was found to accumulate measurably in Purkinje neurons by 20 months of age, and to increase significantly thereafter. Deposition of the substance occurred almost exclusively at the apical pole of the soma. Our data suggest, however, that accumulation of lipofuscin in Purkinje neurons, as well as its reported accumulation in the inferior olive, is not a primary cause of electrophysiological dysfunction. There was no apparent age change in glyoxylic acid induced catecholamine fluorescence nor, in separate pharmacological studies, could any senescent alteration in cerebellar catecholamine levels be found.  相似文献   
63.
以某生物安全实验室典型核心工作间为例,阐述了其负荷情况。并结合笔者单位近两年检测的28个生物安全三级实验室项目中的98间核心工作间,分析了换气次数的分布频次与室内洁净度的关系,探讨了高等级生物安全实验室的节能措施。  相似文献   
64.
正常人人迎寸口脉动相关性的季节观察   总被引:1,自引:0,他引:1  
目的 进行正常人人迎寸口脉动相关性的季节观察。方法 借助经颅多普勒血流检测仪(简称TCD)分别于1月中旬(冬季)、7月中旬(夏季)检测随机选择的62例正常人的迎脉寸口脉搏情况,并分不同性别、不同年龄比较分析了人迎脉,寸口脉的变化。结果 ①正常人人迎脉与寸口脉的血流速度无明显差异(P>0.05),在不同了组、不同年龄组、不同性别组中均是如此;②下人冬季的寸口脉的血流速度 较夏季稍大;正常人夏季的人迎脉的血流速度较冬季稍大,但均无显著性差异(P>0.05);③正常人冬季寸口脉的血汉速度稍大于人迎脉的血流速度 ,人迎的血流速度稍大于寸口脉的血流速度,在不同性别组中是如此,在不同年龄组中基本如此,唯60-75岁组夏季的寸口脉反而稍大于人迎脉。结论 初步建立了正常人不同季节人迎脉、寸口脉脉动及其相关性的TCD指标。  相似文献   
65.
目的:探究小檗碱对慢性萎缩性胃炎(CAG)的改善作用及其作用机制。方法:将SD大鼠随机分为对照组、模型组、小檗碱低剂量组、小檗碱中剂量组、小檗碱高剂量组和DUSP19组,每组9只。除对照组外均构建CAG模型,小檗碱低、中、高剂量分别灌胃给与25、50、100 mg/kg的小檗碱,DUSP19组灌胃给与100 mg/kg的小檗碱和尾静脉注射JAK激酶2/信号转导及转录激活因子3(JAK2/STAT3)通路激活剂DUSP19 100 μmol/L。苏木精-伊红(HE)染色法检测病理学变化;蛋白质印迹法检测JAK2/STAT3信号通路及凋亡相关蛋白表达;酶联免疫吸附试验(ELISA)检测血清相关因子表达水平;原位末端转移酶标记技术(TUNEL)检测胃黏膜细胞凋亡。结果:与模型组比较,小檗碱观察组磷酸化JAK2(p-JAK2)、磷酸化JAK3(p-JAK3)、胃动素(MTL)、肿瘤坏死因子-α(TNF-α)、白细胞介素6(IL-6)、白细胞介素-1β(IL-1β)、前列腺素E2(PGE2)、内皮素(ET)、B淋巴细胞瘤-2相关X蛋白(Bax)、裂解胱天蛋白酶3(Cl-caspase-3)、裂解胱天蛋白酶9(Cl-caspase-9)水平及细胞凋亡率显著降低(P<0.05),胃泌素(GAS)、分泌型免疫球蛋白A(sIgA)、谷胱甘肽(GSH)、B淋巴细胞瘤-2(Bcl-2)水平显著升高(P<0.05);JAK2/STAT3通路激活剂DUSP19可显著扭转小檗碱对上述指标的影响(P<0.05),且HE结果显示小檗碱可显著改善CAG大鼠胃组织病理病变。结论:小檗碱可通过JAK2/STAT3信号通路抑制细胞凋亡和炎症反应减轻大鼠慢性萎缩性胃炎。  相似文献   
66.
A prospective study of biochemical changes after vertical banded gastroplasty for morbid obesity, in 94 patients (10 males and 84 females, ages ranging from 18 to 59 years) has been carried out. Liver function tests and electrolyte estimations were performed preoperatively, during hospitalisation for surgery, at 6 weeks and at 6 months postoperatively, and demonstrated no significant changes in liver function in these patients 6 months after surgery. The study concludes that there is no increase in the risk of liver damage or electrolyte disturbance after vertical gastroplasty, but that there may be subtle hepatic changes present as gall bladder disease developed in 18 patients postoperation (19%).  相似文献   
67.
The forceful and macho look of a prototypical man may not be unduly appealing to others whom he meets. This forceful look might not even appeal to the individual himself. In order to soften this appearance, a series of operative procedures has been devised for use on the craniofacial skeleton. These surgical steps can be done in a single operation or as a series of multiple operative procedures. Moreover, the needs of some patients may require that only special segments of these procedures be performed. This article presents these operative procedures and describes the feasibility with which they can be performed. Complications and unfavorable outcomes, when they occur, are usually related to unrealistic expectations on the part of the patient. The surgical steps routinely performed are those that contour the forehead, orbits, malar eminence, cheeks, chin, angle of the mandible, and larynx. Three categories of patients are described: the female with a male face; the male with a forceful look; and the patient requesting a gender identity change. The psychosocial, psychological, and behavioral problems leading to the decision for surgery will be the basis of final patient selection.Presented at the 9th Congress of the International Society of Aesthetic Plastic Surgery, New York City, October 1987  相似文献   
68.
目的 探讨彩色多普勒超声鉴别诊断结节性甲状腺病变的意义。方法 回顾性分析病理或细胞学证实的结节性甲状腺病变74例二维超声和彩色多普勒超声(CDFI)表现。结果 结节性甲状腺肿、甲状腺腺瘤和腺癌超声和血流图像表现有一定规律性,定位准确,敏感性强。结论 彩色多普勒超声是诊断结节性甲状腺病变首选检查方法。  相似文献   
69.
伴嗜酸性粒细胞增多性血管淋巴样增生的临床病理分析   总被引:6,自引:0,他引:6  
目的:探讨伴嗜酸性粒细胞增多性血管淋巴样增生的临床病理学特征。方法:对我科1950-1999年期间所诊治的伴嗜酸性粒细胞增多性血管淋巴样增生的7名患者的病理标本重新切片,进行病理学上的分析。结果:伴嗜酸性粒细胞增多性血管淋巴样增生在病理学上有其特征,形态学上的改变主要表现在以下3个方面:①真皮内大量毛细血管增生;②血管内皮细胞增生肿大,似“墓碑”状突入血管腔;③病变处有淋巴细胞、嗜酸性粒细胞混合浸润。结论:伴嗜酸性粒细胞增多性血管淋巴样增生是一种良性局限性血管增生,其病因及发病机制尚不清楚。熟悉这一疾病的组织学改变对避免误诊为其他类拟疾病有重要意义。  相似文献   
70.
In a prospective autopsy series of 39 cases of fatal drowning, the detailed dissection of the skeletal muscles of the neck, anterior / posterior trunk and the upper extremities in layers revealed intramuscular hemorrhages of different size and shape in 20 cases (51.3 %). Light microscopy examination showed a premortal (vital/agonal) type of muscular alteration in 7 (50 %) out of 14 macroscopical hemorrhage-positive cases. These hemorrhages and histological muscle alterations are attributed to agonal convulsions, hypercontraction and overexertion of the affected muscle groups. As long as no cutaneous or subcutaneous hematomas above the hemorrhages can be found, these autopsy findings (with special reference to histology) can serve as an additional criterion concerning the differentiation of drowning and another cause of death. Received: 31 July 1998 / Received in revised form: 31 August 1998  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