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   39631篇
  免费   3489篇
  国内免费   790篇
耳鼻咽喉   170篇
儿科学   846篇
妇产科学   1832篇
基础医学   1940篇
口腔科学   293篇
临床医学   12980篇
内科学   6282篇
皮肤病学   441篇
神经病学   1610篇
特种医学   2413篇
外国民族医学   6篇
外科学   3804篇
综合类   5883篇
现状与发展   3篇
预防医学   1432篇
眼科学   635篇
药学   1623篇
  48篇
中国医学   392篇
肿瘤学   1277篇
  2024年   69篇
  2023年   555篇
  2022年   966篇
  2021年   1314篇
  2020年   1653篇
  2019年   1453篇
  2018年   1467篇
  2017年   1477篇
  2016年   1455篇
  2015年   1490篇
  2014年   2670篇
  2013年   2655篇
  2012年   2092篇
  2011年   2343篇
  2010年   1919篇
  2009年   1871篇
  2008年   1953篇
  2007年   2085篇
  2006年   1879篇
  2005年   1671篇
  2004年   1446篇
  2003年   1211篇
  2002年   1038篇
  2001年   991篇
  2000年   783篇
  1999年   748篇
  1998年   617篇
  1997年   608篇
  1996年   533篇
  1995年   476篇
  1994年   392篇
  1993年   328篇
  1992年   284篇
  1991年   256篇
  1990年   197篇
  1989年   128篇
  1988年   132篇
  1987年   100篇
  1986年   106篇
  1985年   132篇
  1984年   97篇
  1983年   44篇
  1982年   73篇
  1981年   47篇
  1980年   32篇
  1979年   27篇
  1978年   19篇
  1977年   10篇
  1976年   10篇
  1973年   4篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
OBJECTIVE: To compare the outcome of urgent haemorrhoidectomy with conservative treatment for prolapsed thrombosed internal haemorrhoids. METHODS: A prospective randomised study of 50 patients with prolapsed thrombosed internal haemorrhoids was carried out using clinical and ultrasonic outcome measures. Peri-operative bed occupancy and the presence of symptoms at 6 and 24 months were compared. Endoanal ultrasonic scanning was carried out to investigate anal sphincter integrity in those patients willing to be studied. RESULTS: The median length of hospital stay for the group treated conservatively; 2 nights (range 1-9 nights) was significantly shorter than for the group treated by urgent haemorrhoidectomy; 4 nights (range 1-12 nights, P < 0.01). There was no difference between treatment groups in the number of patients with symptoms at six or 24 months. Urgent haemorrhoidectomy was associated with a significantly higher incidence of endosonographically detected anal sphincter damage in 18 patients: 66%vs 0% (P = 0.009). CONCLUSION: Conservative treatment for prolapsed thrombosed internal haemorrhoids is associated with shorter in patient stay and less anal sphincter damage compared with operative treatment.  相似文献   
112.
目的 探讨冠状动脉瘘的影像特征、鉴别诊断及彩色多普勒超声在飞行员改装体检中的医学鉴定价值.方法 分析1例飞行员左冠状动脉-肺动脉瘘超声图像特征并复习相关文献.探讨应用彩色多普勒超声检查在飞行员改装体检中的必要性.结果 彩色多普勒超声显示心底部心肌间走行迂曲的异常血流束,经主肺动脉外侧壁注入肺动脉内.超声诊断:左冠状动脉-肺动脉瘘.飞行结论:改装并原机种飞行不合格结论彩色多普勒超声检查能清晰显示冠状动脉瘘,并能追踪观察其走行、部位、内径和大小,超声诊断与冠状动脉造影结果相符.冠状动脉瘘早期无特异性临床表现,彩色多普勒超声心动图诊断冠状动脉瘘直接、安全、快捷,具有重要的临床价值,是明确诊断的首选方法.  相似文献   
113.
Dual-energy X-ray absorptiometry (DXA) and quantitative ultrasound (QUS) are the accepted modalities for the evaluation of fracture risk in the clinical setting. However, neither method provides a direct measurement of bone mechanics. In this study, we investigated a prototype device, known as a mechanical response tissue analyzer (MRTA), which provides direct mechanical measurements of mechanical properties of bone. A total of 56 healthy volunteers (20 men and 36 women) between the ages of 18 and 83 were recruited. The MRTA was used to measure the cross-sectional bending stiffness (EI) of the ulna bone. Axial speed of sound (SOS) at the ulna bone was determined by QUS; bone mineral content (BMC) and bone mineral density (BMD) were determined by DXA. Correlations, regression analysis, and analyses of variance (ANOVAs) were used to compare the three modalities. These analyses revealed that although there are strong linear relationships among the data collected by the various technologies, the bone properties reflected by MRTA are not fully explained by DXA and QUS. We conclude that the total information conveyed by MRTA measurements is unique. Further research is needed to delineate the different qualities of bone strength that are captured by MRTA, but not by DXA or QUS.  相似文献   
114.
目的 通过与血管内超声 ( IVUS)相比较 ,探讨压力导丝在评价冠脉内支架置入即刻效果 ,指导优化支架置入中的作用。方法  5 1例患者置入冠脉内支架后先后予血管内超声和压力导丝检测判断是否达到相应的理想支架置入标准。若未达标准 ,则进一步采用更高压力同样球囊或更大球囊再扩张。结果 支架置入后 IVUS判断 3 1例达到标准 ,不需再扩张 ,15例不满意者再扩张支架 ,支架内截面积增加 2 4 .3 % ( P<0 .0 5 ) ,最终 4 1例 ( 89% )得到满意 IVUS,5例因超声导管未跨过支架无超声资料 ;压力导丝检测 3 5例达到标准 ,不需再扩张 ,16例不满意者再扩张支架最终 4 5例 ( 88% )得到满意结果 (心肌部分血流储备 ,FFRmyo>0 .90 )。血管内超声和压力导丝两者在判定理想支架置入方面有很好的相关性 ,符合率达 90 %。以血管内超声检测作金标准 ,应用受试者工作特性曲线 ( ROC)计算心肌部分血流储备 FFRmyo预测理想支架置入的最佳临界点为 0 .90。结论 压力导丝是指导冠脉支架置入更方便、安全的有效手段 ,有广泛推广应用的价值  相似文献   
115.
Summary Seventy-five diabetic and 40 nondiabetic subjects who where suffering from peripheral vascular disease were studied in order to determine whether the degree of the severity of their disease can be better calculated by Doppler ultrasound examinations of the peak velocity than by the systolic pressure of the peripheral bloodstream. In 46 examinations of normal controls the mean value of the peak velocity was 13.3±3.3 cm/s with a standard deviation of 15.4%±13.2% on one day and 16.1%±15.9% on different days. Considering patients with or without diabetes mellitus the velocity was significantly decreased in correlation to an increasing degree of severity of the vascular disease (P<0.001); however, the decrease was lower in diabetic than in nondiabetic subjects (6.9±2.8 vs 4.6±6.2,P<0.05). The systolic pressure hardly decreased, but remained higher in all stages of peripheral vascular disease of diabetics than in the nondiabetic subject (P<0.05 toP<0.005). There was a significant decrease of the systolic pressure only in diabetic subjects with the most advanced degree of the disease, i.e. stage IV (P<0.05).It is concluded from this study that Doppler ultrasound measurements of the peak velocity of the peripheral bloodstream are a useful parameter to calculate the degree of severity of the peripheral vascular disease. In addition, it is concluded than peak velocity is an even better prognostic indicator of peripheral vascular disease than is measurement of the systolic blood pressure at the feet.

Abkürzungen AVK periphere arterielle Verschlußkrankheit - USDI Ultraschall-Doppler-Index - MSBG maximale Blutströmungsgeschwindigkeit - HFV Herzfrequenzvariation  相似文献   
116.
目的探讨二维超声和彩色多普勒血流显像(cDFI)对移植胰腺的功能和术后并发症的监测作用。方法用彩色多普勒超声观察6例移植胰腺的形态和血流动力学变化情况。结果(1)功能正常的移植胰腺在术后形态正常,体积偏大,主胰管内径正常,实质回声较正常胰腺略高,动脉PSV13~64cm/s,R10.44~0.68,P10.67~2.33。(2)2例出现急性排异和1例出现移植胰腺炎的移植胰腺周边出现低或无回声区,实质回声明显减低,分布不均。1例急性重度排异的RI值超过0.9,而另1例急性轻度排异RI值小于0.7。1例移植胰腺炎RI值超过0.9,PI值超过4.0。结论CDFI作为一种无创的检查技术对胰腺移植术后的监测和诊治具有积极意义。  相似文献   
117.
118.
Although observational studies suggest that hyperhomocysteinemia may be a risk factor for coronary allograft vasculopathy (CAV), prospective data on homocysteine-lowering interventions and CAV development are lacking. We, therefore, randomized 44 de novo heart transplant (HT) recipients to 15 mg/day of 5-methyl-tetrahydrofolate (n=22), or standard therapy (control group, n=22) to investigate the effect of homocysteine lowering on the change in coronary intimal hyperplasia during the first 12 months after transplant, as detected by intra-vascular ultrasound (IVUS). Although 12 months after HT, homocysteinemia was lower in folate-treated patients (p<0.001), coronary intimal area increased similarly in the two groups (p>0.4). Conversely, hypercholesterolemia and cytomegalovirus infection were both associated with increased intimal hyperplasia (p<0.04), independently from folate intake. Sub-group analysis revealed that folate therapy reduced intimal hyperplasia in patients with hyperhomocysteinemia before randomization (n=19; p=0.02), but increased intimal hyperplasia in patients with normal homocysteine plasma concentrations (p=0.02). This bimodal effect of folate therapy persisted significantly after adjusting for cytomegalovirus infection and hypercholesterolemia. Despite effective in prevent hyperhomocysteinemia after heart transplantation, folate therapy does not seem to affect early CAV onset. However, sub-group analysis suggests that folate therapy may delay CAV development only in patients with baseline hyperhomocysteinemia, while may favor CAV progression in recipients with normal baseline homocysteinemia.  相似文献   
119.
毕四锐 《心脏杂志》2006,18(2):228-230
目的评价螺内酯联合依那普利治疗老年人扩张型心肌病(DCM)心力衰竭的有效性和安全性。方法以148例老年DCM心力衰竭患者作研究对象,按随机化原则分为观察组(74例)和对照组(74例)。对照组为依那普利,加上基础用药(地高辛、双氢克尿噻);观察组为对照组用药加上螺内酯。治疗6周后复查两组的动态心电图、超声心动图。结果治疗后两组的左室射血分数(LVEF)均有增加,左室收缩末期容积(LVESV)和左室舒张末期容积(LVEDV)均有减少,24 h室性早搏(VA)数也均有减少;观察组与对照组比较,LVEF显著增加。两组均未发现高血钾及肝肾功能损害。结论在老年DCM心力衰竭常规用药的基础上,常规加用螺内酯联合依那普利的治疗有效、安全,可显著改善左室重构和防治猝死。  相似文献   
120.
Objective. The objective of our paper is to show that the spatio-temporal image correlation (STIC) and tomographic ultrasound imaging (TUI) is very convenient and helpful for the fetal screening of complex congenital heart defects (CHD).

Methods. Ultrasound examinations were performed using a Voluson 730 EXPERT or PRO system (GE Medical system, Kretztechnik, Zipf, Austria), and the transabdominal probe (RAB 4-8 MHz or 1-5 MHz) was used to acquire the STIC volumes. Various complex CHD including heterotaxia, ventricular septal defect (VSD), atrio-ventricular septal defect (AVSD), tetralogy of fallot (TOF), transposition of great artery (TGA), hypoplastic left heart syndrome (HLHS) were examined between 20 weeks and 35 weeks. After routine cardiac screening and examination by two-dimensional ultrasound, three- and four-dimensional ultrasound were performed by gray-scaled and color flow mapping. After the examination detailed analysis of CHD were performed by STIC and TUI.

Results. In the case of heterotaxia, STIC and TUI was useful for the detection of stomach and cardiac apex in the different slices. In the case of VSD and AVSD, they were useful for the exact determination of septal defect location. In the cases of TOF, TGA and HLHS, they were helpful for observation of outflow tract and exact diagnosis.

Conclusion. In the screening of complex CHD including heterotaxia, VSD, AVSD, TOF, TGA and HLHS, STIC is very useful and powerful tool.  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