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   331篇
  免费   26篇
  国内免费   31篇
儿科学   26篇
妇产科学   6篇
基础医学   15篇
口腔科学   13篇
临床医学   78篇
内科学   62篇
皮肤病学   1篇
神经病学   20篇
特种医学   55篇
外科学   18篇
综合类   19篇
预防医学   16篇
眼科学   4篇
药学   42篇
中国医学   1篇
肿瘤学   12篇
  2023年   1篇
  2022年   2篇
  2021年   1篇
  2020年   1篇
  2019年   3篇
  2018年   7篇
  2017年   5篇
  2016年   3篇
  2015年   4篇
  2014年   10篇
  2013年   17篇
  2012年   10篇
  2011年   9篇
  2010年   9篇
  2009年   15篇
  2008年   13篇
  2007年   22篇
  2006年   18篇
  2005年   13篇
  2004年   4篇
  2003年   6篇
  2002年   4篇
  2001年   5篇
  2000年   4篇
  1999年   14篇
  1998年   12篇
  1997年   18篇
  1996年   15篇
  1995年   13篇
  1994年   19篇
  1993年   14篇
  1992年   9篇
  1991年   8篇
  1990年   4篇
  1989年   11篇
  1988年   6篇
  1987年   10篇
  1986年   5篇
  1985年   6篇
  1984年   4篇
  1983年   3篇
  1982年   3篇
  1981年   10篇
  1980年   3篇
  1979年   2篇
  1977年   3篇
  1976年   3篇
  1975年   5篇
  1963年   2篇
排序方式: 共有388条查询结果,搜索用时 15 毫秒
11.
12.
背景: 不同地区骨峰值和标准差不同,对骨质疏松诊断率有较大影响。探讨建立一完整数据库为中国人骨质疏松诊断准确性提供依据。 目的:探讨青年人腰椎骨密度和标准差正常参考值影响骨质疏松症检出率的程度。 设计、时间及地点:调查分析,于1997-01/1999-12分别在北京、上海、广州、南京、嘉兴和成都市完成。 对象:采用前瞻性及回顾性方法对全国6个中心骨密度参考数据库中11 418人进行调查统计分析;男3 666人,女7 752人;年龄20岁~90岁;分别来自北京(2 385人)、广州(1 178人)、上海(1 404人)、南京(2 938人)、成都(1 425人)、嘉兴(2 088人),受试者来源于社区调查、健康体检和健康志愿者。 方法:用GE-Lunar公司的DXA仪测量骨密度,调查全国6个中心11 418人L2~L4腰椎后前位和髋部骨密度,建立了骨密度参考数据库。6个中心的仪器内部精度0.3%~0.7%,仪器间的精度1.1%。 主要观察指标:①6个中心不同年龄组腰椎骨密度分布。②青年人群骨密度及其标准差值对骨质疏松症检出率的影响。 结果:中国汉族女性以腰椎进行骨质疏松症诊断的青年人群的骨密度和标准差值,6个中心,最大差值分别为0.098 g/cm2和0.027 g/cm2。用6个中心及总体各自的青年人平均骨密度和标准差值为参考标准,对同一人群计算T-score和获得的骨质疏松症检出率不相同;发现青年人平均骨密度每变化0.01 g/cm2,则骨质疏松症检出率变化1.6%(呈正相关),其标准差值每变化 0.01 g/cm2,则骨质疏松症检出率变化4%(呈负相关)。 结论:青年人平均骨密度和标准差值不同引起骨质疏松症检出率也不相同。为了让不同中心的骨质疏松症检出率有可比性,建议同一个类型的骨密度仪,同一个种族,同一个地区用一个设计较完善大样本的参考数据库,以其青年人正常参考值计算T-score。  相似文献   
13.
14.
目的:对比观察骨髓间充质干细胞移植前后脑梗死大鼠脑电图的变化。方法:实验于2002-09/12在解放军第三军医大学中心实验室及西南医院神经内科肌电图室完成。①实验分组:选取清洁级健康成年Wistar大鼠15只,随机数字表法分为干细胞移植组、模型对照组、假手术组,5只/组。②实验方法:另取2只健康幼年Wistar大鼠用于骨髓间充质干细胞的提取,联合采用密度梯度离心及贴壁法分离培养大鼠骨髓间充质干细胞,选取生长良好的1~3代细胞用于移植实验。干细胞移植组、模型对照组大鼠建立大脑中动脉栓塞模型。假手术组仅分离颈总动脉、颈外动脉和颈内动脉,不予结扎和放置线栓。造模后1周,干细胞移植组、假手术组大鼠行细胞移植,在立体定向仪定位下于脑梗死区(壳核)直接注射骨髓间充质干细胞悬液5μL,细胞浓度1×104μL-1,移植坐标为前囟前1.0mm,右旁开3.0mm,硬膜下5.0mm。模型对照组大鼠于相同部位注射等量不含细胞的磷酸盐缓冲液。③实验评估:采用脑电图机分别于造模前、造模后1周(移植前)、细胞移植后4周对各组大鼠进行脑电图检测。结果:15只大鼠均进入结果分析。①造模前基本节律为8~11Hz、15~30μV的α波,间或少量θ波,双侧对称。②造模后1周,假手术组异常率为0;模型对照组20%(1/5)轻度异常,80%(4/5)中度异常;干细胞移植组20%(1/5)轻度异常,60%(3/5)中度异常,20%(1/5)重度异常。③细胞移植后4周,假手术组脑电图恢复正常;模型对照组随术后时间的延长慢波有所减少,但仍可见到δ波、棘波、棘慢波的发放,至细胞移植后4周60%(3/5)轻度异常,40%(2/5)中度异常;干细胞移植组术后局限性慢波逐渐减少,基本节律全部恢复为α波,不对称的情况明显好转,至细胞移植后4周60%(3/5)轻度异常,以病灶侧局限性θ波较多为主,另外40%(2/5)基本正常。结论:动物实验显示骨髓间充质干细胞移植对脑梗死大鼠的脑电图背景节律有改善作用,一定程度上促进了神经系统功能的恢复。  相似文献   
15.
A collection of 3069 human sera collected in the area of the municipality of Modena, Emilia Romagna, Italy, was retrospectively investigated for specific antibodies against Usutu (USUV) and West Nile viruses (WNV). All the samples resulting positive using a preliminary screening test were analyzed with the plaque reduction neutralization test. Overall, 24 sera were confirmed as positive for USUV (0.78%) and 13 for WNV (0.42%). The results suggest that in 2012, USUV was circulating more than WNV in North‐eastern Italy.  相似文献   
16.
Patients with disorders of sex development (DSD), especially those with gonadal dysgenesis and hypovirilization, are at risk of developing the so-called type II germ cell tumors (GCTs). Both carcinoma in situ and gonadoblastoma (GB) can be the precursor lesion, resulting in a seminomatous or non-seminomatous invasive cancer. SRY mutations residing in the HMG domain are found in 10–15% of 46,XY gonadal dysgenesis cases. This domain contains two nuclear localization signals (NLSs). In this study, we report a unique case of a phenotypical normal woman, diagnosed as a patient with 46,XY gonadal dysgenesis, with an NLS missense mutation, on the basis of the histological diagnosis of a unilateral GB. The normal role of SRY in gonadal development is the upregulation of SOX9 expression. The premalignant lesion of the initially removed gonad was positive for OCT3/4, TSPY and stem cell factor in germ cells, and for FOXL2 in the stromal component (ie, granulosa cells), but not for SOX9. On the basis of these findings, prophylactical gonadectomy of the other gonad was performed, also showing a GB lesion positive for both FOXL2 (ovary) and SOX9 (testis). The identified W70L mutation in the SRY gene resulted in a 50% reduction in the nuclear accumulation of the mutant protein compared with wild type. This likely explains the diminished SOX9 expression, and therefore the lack of proper Sertoli cell differentiation during development. This case shows the value of the proper diagnosis of human GCTs in identification of patients with DSD, which allows subsequent early diagnosis and prevention of the development of an invasive cancer, likely to be treated by chemotherapy at young age.  相似文献   
17.
Hill M, Finning K, Martin P, Hogg J, Meaney C, Norbury G, Daniels G, Chitty LS. Non‐invasive prenatal determination of fetal sex: translating research into clinical practice. The effectiveness and clinical utility of non‐invasive prenatal diagnosis (NIPD) for fetal sex determination using cell‐free fetal DNA (cffDNA) was assessed by undertaking a prospective national audit of UK testing. NIPD was performed using real‐time polymerase chain reaction analysis of the DYS14 or SRY gene in cffDNA extracted from maternal plasma. All cases referred for fetal sex determination from 1 April 2006 to 31 March 2009 were ascertained from two laboratories offering the test. Fetal gender determined by NIPD was compared with that based on ultrasound, invasive test or phenotype at birth. Indication and rate of invasive testing was ascertained. In the first year, results were issued in 150/161 pregnancies tested. Of the 135 with outcome data, results were concordant in 130/135 [96.3% (95% CI 91.6–98.8%)]. Reporting criteria were changed and in the subsequent 511 pregnancies the concordancy rate increased to 401/403 [99.5% (95% CI 98.2–99.9%)]. Over the 3 years only 32.9% (174/528) underwent invasive testing. NIPD for fetal sex determination using cffDNA is highly accurate when performed in National Health Service laboratories if stringent reporting criteria are applied. Parents should be advised of the small risk of discordant results and possible need for repeat testing to resolve inconclusive results.  相似文献   
18.
刘文英  周炜  盛龙生  安登魁 《药学学报》1988,23(12):933-937
本文采用Waters ILC-1离子液相色谱仪,IC-PAK A50×4.6mm色谱柱,pH6.61×10-3mol/L邻苯二甲酸溶液为流动相,430型电导检测器检测,由外标法和外标单点校正法同时测定了葡萄糖酸钙及其杂质(Cl-,SO42-)的含量。方法简便、快速,测定结果与中国药典法一致。外标法和外标单点校正法测定Cl-,SO42-的平均回收率为100.8%和100.2%,相关系数分别为0.9951(n=8)和0.9961(n=8)。  相似文献   
19.
The aim of this study was to determine the association of benign recurrent vertigo (BRV) and migraine, using standardized questionnaire-based interview of 208 patients with BRV recruited through a University Neurotology clinic. Of 208 patients with BRV, 180 (87%) met the International Classification of Headache Disorders 2004 criteria for migraine: 112 migraine with aura (62%) and 68 without aura (38%). Twenty-eight (13%) did not meet criteria for migraine. Among patients with migraine, 70% experienced headache, one or more auras, photophobia, or auditory symptoms with some or all of their vertigo attacks, meeting the criteria for definite migrainous vertigo. Thirty per cent never experienced migraine symptoms concurrent with vertigo attacks. These met criteria for probable migrainous vertigo. Among patients without migraine, 21% experienced either photophobia or auditory symptoms with some or all of their vertigo attacks; 79% experienced only isolated vertigo. The age of onset and duration of vertigo attacks did not differ significantly between patients with (34 ± 1.2 years) and patients without migraine (31 ± 3.0 years). In patients with migraine, the age of onset of migraine headache preceded the onset of vertigo attacks by an average of 14 years and aura preceded vertigo by 8 years. The most frequent duration of vertigo attacks was between 1 h and 1 day. Benign recurrent vertigo is highly associated with migraine, but a high proportion of patients with BRV and migraine never have migraine symptoms during their vertigo attacks. Other features such as age of onset and duration of vertigo are similar between patients with or without migraine.  相似文献   
20.

Background  

Studies on the impact of the 'obesogenic' environment have often used non-theoretical approaches. In this journal's debate and in other papers authors have argued the necessity of formulating conceptual models for differentiating the causal role of environmental influences on behavior.  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