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   171591篇
  免费   13808篇
  国内免费   5430篇
耳鼻咽喉   1148篇
儿科学   4528篇
妇产科学   1520篇
基础医学   28549篇
口腔科学   2986篇
临床医学   16568篇
内科学   24573篇
皮肤病学   1556篇
神经病学   7369篇
特种医学   3301篇
外国民族医学   22篇
外科学   12763篇
综合类   27195篇
现状与发展   14篇
一般理论   25篇
预防医学   12115篇
眼科学   4193篇
药学   18552篇
  35篇
中国医学   9303篇
肿瘤学   14514篇
  2024年   363篇
  2023年   1986篇
  2022年   4211篇
  2021年   6012篇
  2020年   5365篇
  2019年   5516篇
  2018年   5369篇
  2017年   5425篇
  2016年   5641篇
  2015年   5668篇
  2014年   8844篇
  2013年   10927篇
  2012年   8372篇
  2011年   9573篇
  2010年   8176篇
  2009年   8036篇
  2008年   8096篇
  2007年   9337篇
  2006年   8581篇
  2005年   8450篇
  2004年   7378篇
  2003年   6547篇
  2002年   4932篇
  2001年   4842篇
  2000年   3939篇
  1999年   3683篇
  1998年   2636篇
  1997年   2362篇
  1996年   2403篇
  1995年   2227篇
  1994年   1982篇
  1993年   1776篇
  1992年   1529篇
  1991年   1338篇
  1990年   1134篇
  1989年   1042篇
  1988年   989篇
  1987年   760篇
  1986年   593篇
  1985年   673篇
  1984年   663篇
  1983年   428篇
  1982年   521篇
  1981年   444篇
  1980年   391篇
  1979年   316篇
  1978年   254篇
  1977年   206篇
  1976年   241篇
  1975年   152篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Abstract: The dependence of transient pressure characteristics of a ventricular assist device (VAD) on the compliance of its housing and cannulas was investigated in a mock circulation. The peak rate of change of pressure ( dP/dt max) values was greater in the cannulas than other compartments and was associated with valve closure-induced pressure oscillations. When cannula compliance was increased from 0.0057 to 0.0129 cm3/mm Hg, these values decreased by ˜20%, and outflow cannula pressure oscillation frequency decreased from 17.5 Hz by 35%. This trend was also apparent in the inflow. A VAD housing compliance increase from 0.0162 to 0.0483 cm3/mm Hg caused a dP/dt max decrease of 30% in both the blood chamber and the outflow cannula. The effect of this change on the inflow was weaker implying that housing absorbs the energy associated with outflow deceleration more effectively than the inflow. These findings suggest that increasing VAD housing and cannulas compliance can improve hydrodynamic performance.  相似文献   
22.
This study examined the feasibility of isolating and transferringthe centrosome-containing region of spermatozoa to mature humanoocytes. The findings demonstrate that individual sperm centrosomescan be transferred and are capable of nucleating maternal tubulinto form a well-developed sperm aster in the recipient oocyte.The results are discussed with respect to centrosome functionin early human development and applications in clinical in-vitrofertilization in the treatment of certain forms of male factorinfertility.  相似文献   
23.
用放射配体结合分析法分别测定了正常组、特布他林组、特布他林十曲尼司特组豚鼠的肺组织β受体最大结合力和解离常数,结果显示:给特布他林后豚鼠肺组织β受体发生明显的向下调节.曲尼司特可预防此向下调节的发生.  相似文献   
24.
25.
慢性低氧大鼠肺动脉内皮素mRNA的表达及定位   总被引:1,自引:0,他引:1  
目的:探讨慢性低氧大鼠肺动脉内皮素-1基因表达及分布。方法:采用生物素标记cRNA探针,对Wistar大鼠肺动脉进行原位杂交。结果:低氧1周组及低氧2周组大鼠大部分肺动脉内皮细胞ET-1mRNA表达呈阳性信号,而对照组大鼠仅极少数阳性信号(P<0.01);低氧1周组大鼠部分显示强阳性信号。低氧1周组及低氧2周组大鼠部分肺动脉平滑肌细胞呈现ET-1mRNA表达阳性信号,而对照组大鼠则无阳性信号表达(P<0.01及0.05)。结论:慢性低氧对大鼠肺动脉ET-1分泌的影响是在基因转录水平进行,且主要细胞定位在肺动脉内皮细胞,此外还包括肺动脉平滑肌细胞。  相似文献   
26.
作者将29例子宫内膜异位症(简称异位症)患者的异位和在位内膜进行离体组织孵育,应用放射免疫方法检测孵育液中泌乳素(PRL)含量;同时应用ABC免疫酶标记法确定异位和在位内膜分泌PRL的部位,结果异位和在位内膜离体组织经0~24h孵育,孵育液中PRL含量均显著增加(P<0.05);继续孵育至48h,PRL含量不再增加。但异位内膜分泌PRL的活性低于自身在位内膜。免疫组化PRL检测,异位和在位内膜分别有4和6例呈PRL阳性反应。组织学对照现察,内膜成熟上皮细胞数及前蜕膜细胞数越多者,其相应孵育液中PRL含量越高,免疫组化PRL阳性反应也越强。提示异位内膜PRL分泌特点与其自身在位内膜不完全相同,可能与病理环境有关。  相似文献   
27.
OBJECTIVE: This study aimed to investigate the rate of occupational sensitization to horse hair in grooms and whether occupational exposure to horse hair increases respiratory and allergic symptoms and affects lung function in grooms or not. METHODS: This is a cross-sectional study. Two hundred grooms were randomly selected among 1000 grooms working in Veliefendi Hippodrome of Istanbul. One hundred and twenty-five subjects agreed to enter the study. Ninety-two workers who worked in the different parts of this hippodrome enrolled as the control group. A detailed questionnaire including respiratory and allergic symptoms was filled in, physical examination, skin prick tests and pulmonary function tests were performed. RESULTS: Sensitization to horse hair was 12.8% in grooms and 4.3% in controls. The difference was statistically significant (P = 0.0035). Asthma was found in 14.4% of the grooms and 5.4% of the controls, allergic rhinitis in 42.4% of the grooms and 18.4% of the controls, allergic conjunctivitis in 35.2% of the grooms and 15.2% of the controls, and allergic skin diseases in 32.8% of the grooms and 13% of the controls. The differences were statistically significant (P = 0.043, P = 0.0002, P = 0.001 and P = 0.0008, respectively). The means of FEV1, FEV1/FVC and FVC parameters were significantly lower in the groom group (P = 0.006, P = 0.001 and P = 0.003, respectively). In the multivariate analysis, being in the groom group and working years were found to be predictive factors for impairments of lung function (P < 0.001 and P = 0.002, respectively). CONCLUSION: Occupational exposure to horse increases the sensitization to horse hair, induces asthma and allergic symptoms and also impairs lung functions.  相似文献   
28.
This paper reports the changes in prolactin levels after 12 spontaneous and 52 induced pregnancies in 54 women with unambiguous hyperprolactinaemia (median plasma prolactin levels 67.5 ng/ml, range 40-400). Twenty-three of the patients showed radiological evidence of prolactinoma. The pregnancies were induced in 37 patients by bromocriptine, in nine by metergoline, in two by lisuride and in four by other treatments. Of the 64 pregnancies, 16 ended in spontaneous abortion, while 48 went to term. Follow-up was continued for at least 6 months after delivery or until the end of lactation. In a control group of 32 hyperprolactinaemic women (median prolactin 70 ng/ml, range 40-400) not wishing to become pregnant, prolactin changes were similarly registered over a mean period of 15 months without any treatment (range 6-38 months). After pregnancy, a significant downward trend of plasma prolactin was observed in the puerperal women with a 'normalization' rate of 17%. No changes were observed in the 32 controls who did not become pregnant.  相似文献   
29.
[目的]观察比较异环磷酰胺(IFO)、顺铂(DDP)、5-氟尿嘧啶(5-Fu)联合方案(IPF方案)与DDP,5-Fu(PF方案)治疗晚期复发鼻咽癌(Ⅲ-Ⅳ期)的近期疗效及毒副反应。[方法]136例均经病理证实为晚期复发鼻咽癌患者,随机分为IPF组69例,PF组67例(对照组)[结果]IPF组和PF组有效率分别为69.56%(48/69)和43.3%(29/67),两组间差异有显著性(X2=8.519,P<0.01)。中位生存期:IPF组16个月(8-34个月),PF组为6.5个月(4-21个月),两组间差异有显著性(X2=22.36,P<0.05)。毒副作用主要为骨髓抑制,Ⅲ-Ⅳ度白细胞下降率IPF组为49.4%,PF组为5.97%,两组差异有显著性(X2=29.54,P<0.01)。Ⅲ-Ⅳ度血小板下降率IPF组为29.18%,PF组为0%(X2=30.29,P<0.01);Ⅲ-Ⅳ度消化道反应两组的发生率分别为15.94%和11.94%(x2=0.234,P>0.01).且以Ⅲ度为主。[结论]以IFO为主的方案联合治疗晚期复发鼻咽癌疗效好,毒副反应能耐受,可作为一线方案。  相似文献   
30.
BACKGROUND: The role of atopy in the evolution to chronic obstructive disease remains controversial. AIM: We aimed to assess the association between individual sensitization to common allergens and lung function. METHOD: We analysed data from 12,687 subjects aged 20 to 44 years, from 34 centres in 15 countries participating in the European Community Respiratory Health Survey (ECRHS). Participants performed a blood test, lung function test, methacholine challenge, and answered an administered questionnaire. The relationships between specific IgE, FEV1 and FEV1/FVC ratio were assessed for each study centre stratified by sex, followed by random effects meta-analysis. RESULTS: Asthmatics sensitized to house dust mite had a lower FEV1 (-119 mL in women and -112 mL in men) and FEV1/FVC ratio (-1.95%, and -2.48%) than asthmatics without sensitization. Asthmatics sensitized to cat had a lower FEV1 (statistically significant for women only) and a lower FEV1/FVC ratio. Asthmatic women sensitized to grass had a lower FEV1 and a lower ratio, and those sensitized to Cladosporium had a lower FEV1. A weak association was found with sensitization to cat and to Cladosporium among non-asthmatic women, which disappeared after adjusting for BHR. CONCLUSION: We conclude that atopy was related to a lower lung function, which was only apparent among asthmatics. This relationship was explained by specific sensitization to cat and to house dust mite, the latter being homogeneous across areas.  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