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   69515篇
  免费   4054篇
  国内免费   2778篇
耳鼻咽喉   44篇
儿科学   818篇
妇产科学   268篇
基础医学   3798篇
口腔科学   158篇
临床医学   10788篇
内科学   15185篇
皮肤病学   93篇
神经病学   10639篇
特种医学   2937篇
外国民族医学   1篇
外科学   2733篇
综合类   14993篇
现状与发展   1篇
预防医学   2357篇
眼科学   126篇
药学   7159篇
  87篇
中国医学   3958篇
肿瘤学   204篇
  2024年   90篇
  2023年   699篇
  2022年   1253篇
  2021年   2198篇
  2020年   2153篇
  2019年   1658篇
  2018年   1705篇
  2017年   1882篇
  2016年   2102篇
  2015年   2192篇
  2014年   4555篇
  2013年   4451篇
  2012年   4316篇
  2011年   4564篇
  2010年   3856篇
  2009年   3557篇
  2008年   3648篇
  2007年   3730篇
  2006年   3658篇
  2005年   3140篇
  2004年   2577篇
  2003年   2350篇
  2002年   2056篇
  2001年   1899篇
  2000年   1662篇
  1999年   1414篇
  1998年   1124篇
  1997年   1072篇
  1996年   816篇
  1995年   703篇
  1994年   690篇
  1993年   545篇
  1992年   479篇
  1991年   452篇
  1990年   369篇
  1989年   345篇
  1988年   300篇
  1987年   278篇
  1986年   247篇
  1985年   307篇
  1984年   255篇
  1983年   181篇
  1982年   182篇
  1981年   188篇
  1980年   128篇
  1979年   97篇
  1978年   71篇
  1977年   43篇
  1976年   39篇
  1975年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
空腹血糖——急性心肌梗死患者早期死亡的独立预测因子   总被引:2,自引:0,他引:2  
目的研究急性心肌梗死(AMI)患者空腹血糖的预后价值。方法本研究入选257例无糖尿病病史AMI患者。测量患者入院时血糖(AG)和禁食至少8h后的血糖(FG)。随访患者30d,分析AG和FG与患者预后之间的关系。结果共24(9.3%)例无糖尿病病史患者在AMI后30d内死亡。FG正常组死亡2例(1.5%),FG升高者的第一、第二、第三个三分位数组分别死亡4例(9.8%)、5例(12.2%)、13例(31%)。和FG正常组患者相比,校正后的30d死亡的相对危险比(OR)随FG三分位数的增加而增加,第一、第二和第三个三分位数组分别为:2.5(95%CI,0.71~8.5;P=0.011),8.6(95%CI,3.2~23.5;P=0.0005),12.7(95%CI,4.5~36.4;P<0.0003)。同FG和AG都正常的患者相比,AG升高FG正常预测患者30d死亡的OR为0.69(95%CI,0.25~3.80;P=0.59);AG正常FG升高者为3.6(95%CI,2.1~11.5;P=0.04);FG和AG都升高者为10.6(95%CI,4.3~25.6;P<0.0001)。镶嵌模型的比较显示AG并不能增加FG模型预测30d死亡(2=5.2,3df,P=0.20)或预测30d死亡和心力衰竭(2=4.8,3df,P=0.31)的价值。相反,FG却能增加AG模型预测30d死亡(2=24.5,3df,P=0.0001)或预测30d死亡和心力衰竭(2=24.7,3df,P=0.0001)的价值。结论无糖尿病病史AMI患者30d死亡率随AG和FG浓度的增加而增加,FG比AG的预测价值更大。  相似文献   
103.
肥胖类型与脑卒中亚型的相关性研究   总被引:1,自引:0,他引:1  
目的探讨肥胖类型与脑卒中亚型的相关性。方法将573例急性脑卒中患者分为脑出血组126例,脑梗死组447例,脑梗死组再分为脑血栓形成组(215例)和腔隙性脑梗死组(232例),另外选择277例无脑卒中者为对照组。测量腰围、臀围和体重,计算体重指数和腰臀比(WHR),分析肥胖参数与脑卒中各亚组的关系。结果脑卒中各亚组与对照组肥胖发生率差异无显著性意义(P>0.05);各组WHR明显大于对照组(P<0.05)。WHR增大明显增加脑卒中各亚组的危险性(P<0.05);女性腹围增大患腔隙性脑梗死危险性升高(P<0.05);男性体重增加患脑出血的危险性升高(P<0.01)。结论腹型肥胖是脑出血、脑血栓形成和腔隙性脑梗死的危险因素之一。  相似文献   
104.
血浆同型半胱氨酸水平与动脉粥样硬化和脑梗死的关系   总被引:1,自引:1,他引:0  
目的 探讨血浆同型半胱氨酸(Hcy)水平与颈动脉粥样硬化和脑梗死关系.方法 2005-05~2006-02收治的91例脑梗死住院患者被列入研究对象.根据病灶大小分3组大片梗死21例,小片梗死44例,腔隙性梗死26例.根据颈动脉彩超检测结果将研究对象分为颈动脉斑块组34例,无颈动脉斑块组57例.全部患者测定血浆Hcy、血清叶酸、VitB12水平.分析血浆Hcy水平与脑梗死的危险因素、病灶大小、颈动脉粥样硬化斑块及血清叶酸、VitB12的关系.结果 血浆Hcy水平(1)与高血压、糖尿病、血脂、性别、年龄各指标无明显相关关系.(2)与脑梗死病灶大小无关.(3)与颈动脉粥样硬化斑块有关,有斑块34例,血浆Hcy(20.73±9.31)μmol/L,无斑块57例,血浆Hcy (15.46±11.4) μmol/L,前者高于后者(P<0.05).(4)与血清叶酸、VitB12水平呈负相关(r1s=-0.264,r2s=-0.16,P<0.05).结论 血浆Hcy水平与脑梗死病灶大小无关;Hcy水平升高与颈动脉粥样硬化斑块密切相关;与血清叶酸、VitB12水平呈负相关.高血浆Hcy血症可能是颈动脉粥样硬化的危险因素,但与脑梗死关系不明确.  相似文献   
105.
106.
目的我们应用平衡法门控心血池显像技术对不同Killip分级的前壁心肌梗死患者进行左室总体和局部收缩和舒张功能参数的对比分析。方法对照组15例(G0),前壁心肌梗死KillipⅠ级17例(G1),前壁心肌梗死KillipⅡⅢ级12例(G2)。利用平衡法门控心血池显像技术评价3组的左室总体和局部的收缩与舒张功能。结果①左室整体收缩功能,在LVEF,ESC 2个参数中,G1比G0有显著差异(P<0.05),G2分别比G1和G0有显著差异(P<0.05)。在PER、1/3EF、1/3ER 3个参数中,G2分别比G1和G0显著下降(P<0.05)。②左室总体舒张功能,在PFR、1/3FF、1/3FR、EDC中,G1比G0有显著差异(P<0.05),G2分别比G1和G0有显著差异(P<0.05)。③左室局部收缩功能,在以LVREF为参数时,G1在4个节段比G0显著差异(P<0.05),G2在所有6个节段中比G1和G0均显著下降(P<0.05)。④左室局部舒张功能,在以LVR1/3FF为参数时,G1在4个节段比G0显著下降(P<0.05),G2在所有6个节段比G0和G1均显著下降(P<0.05)。结论前壁心肌梗死后出现心功能受损或心力衰竭的主要原因为左室重构。  相似文献   
107.
Objectives To investigate the relationship of the GPIa C807T dimorphism to the risk of myocardial infarction (MI) in Chinese. Methods We did a case-control study including 100 patients and 110 controls with same race. An allele-specific polymerase chain reaction (PCR) was used for genotyping of C807T polymorphism. Results An apparent association was found between the T807 allele and MI among individuals younger than the mean age of 60 years (odds ratio,2.49; 95% confidence interval, 1.08 ~ 6.22 ). The T807 allele remained an independent risk factor for MI when age, sex, smoking, hypertension, diabetes, bodymass index, LDL-cholesterol and HDL-cholesterol were adjusted by logistic regression. Conclusions GPⅠa T807 appears to be an independent risk factor for MI.  相似文献   
108.
109.
表皮生长因子对大鼠脑梗死后神经功能恢复的影响   总被引:2,自引:0,他引:2  
目的 观察表皮生长因子(EGF)对大鼠脑梗死后神经功能恢复的影响。方法 采用肾血管性高血压大鼠制作一侧大脑中动脉皮层支闭塞(MCAO)模型。MCAO术后24 h,32只大鼠侧脑室注入10μl EGF(100μg/L),连续2d,共2μg(EGF组);32只大鼠只注入不含EGF的等量溶液(对照组)。MCAO术后1、2、3和4w,行Bederson神经功能评分后,免疫印迹检测双侧大脑半球生长相关蛋白(GAP43)、突触囊泡蛋白(SYN)和胶质原纤维酸性蛋白(GFAP)的表达。结果 与同期对照组相比,EGF组大鼠在MCAO术后1、2w神经运动功能恢复更好,脑梗死灶同侧半球GAP43、SYN和GFAP有更早期和更高表达(P<0.05)。结论 GAP43、SYN和GFAP等蛋白的早期高峰表达可能与EGF引起的早期神经可塑性改善有关。  相似文献   
110.
BACKGROUND: As a non-invasive technique which can provide comprehensive biological information, 1H-magnetic resonance spectroscopy (1H-MRS) may provide valuable reference data for irreversible recovery or reversible changes in ischemic tissue after stroke. OBJECTIVE: To monitor and evaluate the effect of the urokinase thrombolytic therapy after experimental acute cerebral ischemia by 1H-MRS technology and investigate its adaptability. DESIGN: Randomly controlled animal study. SETTINGS: Shenzhen Hospital of Peking University and National Key Laboratory of Pattern and Atom & Molecular Physics, Wuhan Physics and Mathematics Institute, Chinese Academy of Science. MATERIALS: Eleven healthy adult Sprague-Dawley (SD) rats, weighing 260–300 g and of both genders, were supplied by Experimental Animal Center of Tongji Medical Collage, Huazhong University of Science and Technology [SCXK (e) 2004-007]. 4.7T superconducting nuclear magnetic resonance meter was provided by Brucker Company. METHODS: The experiment was carried out in Shenzhen Hospital of Peking University and National Key Laboratory of Pattern and Atom & Molecular Physics, Wuhan Physics and Mathematics Institute, Chinese Academy of Science from August 2003 to December 2005. ① The rats were randomly divided into 30-minute self-thrombo-embolism group (n =6) and 60-minute self-thrombo-embolism group (n =5). Six rats in 30-minute self-thrombo-embolism group were occluded with clot embolus for 30 minutes and 5 rats in 60-minute self-thrombo-embolism group were occluded for 60 minutes. 10 000 U/kg urokinase was dissolved in 2 mL saline and the operation lasted for 5 minutes. ② 1H-MRS was performed before thrombolysis and at 3 hours and 24 hours after successful embolization. The metabolic changes of N-acetyl-L-aspartic acid (NAA)/phosphocreatine (PCr) + creatine (Cr), choline phosphate (Cho)/PCr+Cr and lactic acid (Lac)/PCr+Cr in the region of interests were analyzed. ③ The T2W image was conducted 24 hours after the thrombolytic therapy with TR=500 ms and TE=25 ms. ④ The subjects were sacrificed immediately after 1H-MRS and the brain tissues were cut into pieces and stained with HE method; in addition, pathological changes were observed under optic microscope. MAIN OUTCOME MEASURES: ① Metabolic changes of NAA/PCr+Cr, Cho/PCr+Cr and Lac/PCr+Cr in the region of interests; ② T2W image at 24 hours after the thrombolysis; ③ pathological observation of brain tissue. RESULTS: Eleven rats were all involved in the final analysis. ① Metabolic changes in the region of interests : In 30-minute self-thrombo-embolism group, the Lac peak emerged immediately after the embolism, but the ischemic zone decreased 3 hours after the thrombolytic therapy (0.252±0.01, 0.603±0.01, P < 0.01). Lac/(PCr+Cr) ratio was 0.290±0.01 at 24 hours after thrombolysis, which was higher than that at 3 hours after thrombolysis (P < 0.01). The NAA/ (PCr+Cr) ratio decreased significantly at 3 hours after the thrombolysis as compared with that before thrombolysis (0.922±0.16, 1.196±0.01, P < 0.05). In 60-minute self-thrombo-embolism group, the Lac/(PCr+Cr) ratio was higher at 3 hours after thrombolysis than that before thrombolysis (0.846±0.12, 0.601±0.11, P < 0.05) and the NAA/(PCr+Cr) decreased at 3 hours after the embolism. Fluctuation of NAA/ (PCr+Cr) ranged from 0.68 to 0.75 before thrombolysis and from 0.71 to 0.75 at 3 hours after thrombolysis. ② T2W image: T2W image showed that 2 subjects in 30-minute self-thrombo-embolism group whose Lac/NAA was higher than 0.7 suffered from intracranial hemorrhage. This meant that the subjects with Lac/NAA > 0.7 were more likely to suffer from intracranial hemorrhage. ③ Histological and morphological examinations: Optic microscope demonstrated that interspace surrounding nerve cells was widened at ischemic center; neurons were swelling; nucleus was stained lightly; pyknosis and mesenchymal edema were mainly observed in lateral cortex of brow and vertex and in lateral part of corpus striatum. CONCLUSION: ①Compound parameters in ischemic area before thrombolysis should be regarded as an important predicting marker for thrombolytic therapy, effect evaluation and termination. ② 1H-MRS combining with other imaging technique is a detecting way for screening cases who are suitable for thrombolytic therapy.  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