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   41490篇
  免费   3278篇
  国内免费   944篇
耳鼻咽喉   91篇
儿科学   966篇
妇产科学   304篇
基础医学   4568篇
口腔科学   449篇
临床医学   6016篇
内科学   11677篇
皮肤病学   298篇
神经病学   1713篇
特种医学   1747篇
外国民族医学   4篇
外科学   4425篇
综合类   4616篇
现状与发展   3篇
预防医学   1484篇
眼科学   143篇
药学   4010篇
  24篇
中国医学   1235篇
肿瘤学   1939篇
  2023年   672篇
  2022年   999篇
  2021年   1531篇
  2020年   1634篇
  2019年   1715篇
  2018年   1665篇
  2017年   1328篇
  2016年   1266篇
  2015年   1460篇
  2014年   2595篇
  2013年   3019篇
  2012年   1997篇
  2011年   2376篇
  2010年   1713篇
  2009年   1816篇
  2008年   1806篇
  2007年   1839篇
  2006年   1702篇
  2005年   1540篇
  2004年   1346篇
  2003年   1152篇
  2002年   917篇
  2001年   932篇
  2000年   739篇
  1999年   755篇
  1998年   650篇
  1997年   648篇
  1996年   506篇
  1995年   523篇
  1994年   489篇
  1993年   401篇
  1992年   356篇
  1991年   341篇
  1990年   321篇
  1989年   214篇
  1988年   217篇
  1987年   214篇
  1986年   179篇
  1985年   297篇
  1984年   336篇
  1983年   197篇
  1982年   205篇
  1981年   217篇
  1980年   163篇
  1979年   136篇
  1978年   108篇
  1977年   92篇
  1976年   91篇
  1975年   75篇
  1974年   72篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
目的观察心脏临时起搏对严重心率缓慢患者血液净化的作用。方法7例因各种病因引起的急慢性肾功能衰竭患者伴严重心率缓慢时,经右颈内静脉、左锁骨下静脉途径穿刺置管行气囊电极床边紧急心脏临时起搏,支持血液净化。结果7例中5例行右颈内静脉置管,2例行左锁骨下静脉置管,起搏均成功,效果肯定,起搏时间2~16天,支持血液净化共32次,其中连续性静脉血液滤过(CVVH)2次,8例次行血液透析滤过(HDF),22例次行常规血透(HD),未发现心脏穿孔、气胸、血胸,1例发生导管感染。1例扩张型心肌病患者因低血压心力衰竭不能控制自动出院,其余6例均抢救成功。结论球囊电极床边心脏临时起搏,操作简便快捷,安全有效,可以提高严重心动过缓合并有肾功能不全的重危患者的抢救成功率。  相似文献   
992.
AIMS: Ischaemic heart disease is the leading cause of mortality and morbidity in patients with end-stage renal disease (ESRD) and after renal transplantation. However, the optimal non-invasive test for coronary artery disease (CAD) diagnosis in this population has yet to be established. The aim of this study was to assess the diagnostic accuracy of dobutamine stress echocardiography (DSE) and baseline plasma cardiac troponin T (cTnT) for detecting significant CAD and predicting adverse cardiac events in patients referred for renal transplantation. METHODS: Coronary angiography, DSE, and baseline cTnT measurements were performed in 118 consecutive patients (mean age 52+/-12 years, 75 male) with ESRD (mean creatinine 608+/-272 micromol/L) referred for renal transplantation. The mean follow-up period was 1.32+/-0.48 years. Significant CAD was defined as a reduction in luminal diameter >70% by visual estimation in at least one major epicardial vessel. An abnormal DSE result defined as the development of a new regional wall motion abnormality in one or more normal resting segments or a deterioration of wall motion in one or more resting hypokinetic segments. A baseline cTnT>0.1 microg/L was taken as positive. RESULTS: Significant CAD in at least one vessel was present in 35 patients (30%). The number of patients with significant 3 vessel and 2 vessel disease was 6 and 7, respectively. An abnormal DSE result was present in 36 (31%) patients. Thirty-one (26%) had cTnT>0.1 microg/L. Sixty-four (54%) patients were on dialysis and 46 (39%) were diabetic. The sensitivity, specificity, positive and negative predictive values for DSE in detecting significant coronary artery disease were 88%, 94%, 86% and 95%, respectively. The same values for a raised cTnT were 54%, 62%, 40% and 74%, respectively. The combination of an abnormal DSE result and raised cTnT gave values of 61%, 91%, 76%, and 80%, respectively. Over the follow-up period, mortality was significantly higher in those with a raised baseline cTnT but not those with an abnormal DSE result or significant CAD. CONCLUSION: DSE is an accurate technique for the detection of significant CAD in renal transplant candidates. An elevated cTnT does not predict significant CAD in this population and when used in conjunction with DSE, reduces the sensitivity of the combined tests. cTnT is an important marker of prognosis in renal transplant candidates.  相似文献   
993.
A case series and technique of transradial cardiac catheterization with cardiac biospy are described. Transradial cardiac catheterization is perceived to be limited to arterial procedures. Using the veins of the forearm, we have converted many previous femoral arterial/venous cardiac procedures to a transradial/forearm approach. Retrospective review of patients undergoing transradial procedures with concurrent cardiac biopsies was undertaken. A convenience sample of transfemoral procedures with biopsies performed by the same operator was identified for comparison. Coronary angiography/left heart catheterization was performed using standard transradial/femoral approaches. A 7 Fr introducer sheath was placed via a large median forearm or femoral vein. Right heart catheterization was done using a 120 cm balloon-tipped catheter and endomyocardial biopsy was performed with a 7 Fr biotome. Both groups were then compared for baseline characteristics and procedural events. Transradial (n = 8) and transfemoral (n = 12) procedures were all done for postcardiac transplantation management. There was no crossover between groups. Durations of the radial procedures (median, 73 min; range, 40-95) were similar to transfemoral procedures (median, 68 min; range, 45-105). No procedural complications were reported. Endomyocardial biopsy plays an important role in the diagnosis of transplant rejection and identification of pathological processes that cause myocardial dysfunction. Transradial cardiac catheterization has some clear advantages over a transfemoral approach. Bilateral cardiac catheterization with concurrent cardiac biopsy is technically feasible using a transradial/forearm approach. This approach offers an alternative approach for selected patients in need of cardiac biopsy.  相似文献   
994.
995.
BACKGROUND: The prognostic value of cardiac troponins (cTn) in patients with non-ST-segment elevation acute coronary syndromes (NSTE ACS) and chronic kidney disease (CKD) is debated. HYPOTHESIS: We tested the performance of cTnI and cTnT for risk stratification in patients with CKD and evaluated the prognostic significance of cTnI and cTnT elevations by their magnitude across the range of CKD severity. METHODS: We examined correlations among cTn elevation, CKD, and in-hospital mortality in 31,586 high-risk patients with NSTE ACS included in the Can Rapid Risk Stratification of Unstable Angina Patients Suppress ADverse Outcomes with Early Implementation of the American College of Cardiology/American Heart Association Guidelines initiative (CRUSADE). Cardiac tropinins I and T levels were categorized as ratios of each site's upper limit of normal (ULN) for myocardial necrosis: normal (cTn ratio < or =1 x ULN), mild (cTn ratio > 1-3 x ULN), and major (cTn ratio > 3 x ULN) elevation. Estimated glomerular filtration rate (eGFR) was calculated using the abbreviated Modification of Diet in Renal Disease equation. Stages of CKD were categorized as normal to mild (eGFR > 60 mL/min), moderate (eGFR 30-60 mL/min), or severe (eGFR < 30 mL/min). RESULTS: Mortality increased more steeply across CKD stages (2.0%-12.9%) than across cTn ratio categories (2.7%-5.4%). In normal or mild CKD, mortality was low regardless of cTn elevations. In moderate CKD, mortality increased incrementally with cTnI (3.3% versus 5.4% versus 7.4%) and cTnT (3.7% versus 5.3% versus 7.3%) elevation. Among severe CKD patients, only major cTn elevations further distinguished risk (cTnI: 10.1% versus 9.7% versus 14.6%; cTnT: 7.0% versus 5.7% versus 14.0%). CONCLUSIONS: In patients with CKD, cTnI and cTnT perform equally in differentiating short-term prognosis following NSTE ACS; however, the prognostic impact of cTn is dependent upon the degree of CKD severity.  相似文献   
996.
目的 研究多年来老年心脏病手术及手术后监护时,4种药物多输入多输出滴注用模糊逻辑系统的决策制定的原理及方法。方法 从模糊逻辑原理起到4种药物对老年心脏病6种症状的病理状态及治疗策略加以研究。结果 求得典型的模糊逻辑用语言结构,表层结构及电脑用的深度结构。结论 在模糊逻辑理论的概念基础上,可算得模糊化输出,代入病人症状的主要生理参数MAP,MPAD和CO检测值。应用模糊匹配及准则计算的结果就是4种药物多输入多输出滴注时的决策制定成功。以一种狗实验的结论证明此种模糊决策制定模块确能成功应用于临床。  相似文献   
997.
比较右室双部位 (RV Bi)起搏和双室 (BiV)同步起搏对血液动力学的影响 ,并与右室心尖部 (RVA)、右室流出道 (RVOT)、左室基底部 (LVB)起搏相比较 ,明确双部位起搏是否优于单部位起搏。 15例患者中病窦综合征 8例、Ⅲ度房室阻滞 7例。分别行RVA、RVOT、LVB、RV Bi、BiV起搏 (VVI,6 0~ 90次 /分 ) ,测定心输出量 (CO)和心脏指数(CI)、肺毛细血管嵌顿压 (PCWP)和QRS波时限 (QRSd)。结果 :①与RVA起搏相比 ,RVOT、LVB、RV Bi、BiV起搏CI分别增加了 7.5 %、11.3%、15 .5 %和 17.2 % ,PCWP分别降低了 14.9%、10 .3%、2 1.7%和 2 0 .0 % (P均 <0 .0 1)。②RV Bi、BiV起搏较RVOT、LVB起搏的CO、CI增高而PCWP降低 (P均 <0 .0 5 )。③RV Bi与BiV起搏、RVOT与LVB起搏之间CO、CI和PCWP无显著差异。④RVOT、RV Bi、BiV起搏的QRSd(分别为 12 8± 11,111± 16 ,10 3± 13ms)较RVA起搏 (146± 18ms)时显著缩短 (P≤ 0 .0 0 1) ,而LVB起搏 (142± 15ms)与RVOT、RVA起搏时无显著差异。结论 :RV Bi起搏和BiV同步起搏的急性血液动力学效果无明显差异 ,但双部位起搏的效果明显优于单部位起搏 ;双部位起搏的QRSd也比单部位起搏明显缩短  相似文献   
998.
目的 :心肌细胞膜上的 β-肾上腺素受体的激活对兴奋 -收缩耦联 (ECC)过程有重要的调节作用。本课题利用异丙肾上腺素 (ISO,1μmol/ L)激活 β-肾上腺素受体从而研究其对源自心肌细胞肌浆网的胞内钙释放 (ECC的重要环节 )和肌浆网内钙容量的影响 ,进而分析钙释放与钙容量之间的关系。方法 :局部场刺激作用于成年大鼠心肌细胞 ,促使后者产生动作电位 ,进而诱发胞内钙瞬变 (ACT) ,由 ACT可估测胞内钙释放。肌浆网内钙容量则由咖啡因 (2 0 m mol/ L)诱发的钙瞬变 (CCT)估测。实验结果均由 Zeiss L SM- 5 10激光共聚焦显微镜系统记录。结果 :ISO作用下的 ACT峰值为 10 .2 9± 0 .35 (n=13)比正常情况下的 5 .74± 0 .2 7(n=18)高 (P<0 .0 1)。 ISO作用下的CCT峰值为 11.2 3± 0 .2 9(n=13)比正常情况下的 7.6 2± 0 .2 4 (n=18)高 (P<0 .0 1)。结论 :ISO可明显地提高心肌细胞内钙释放量和肌浆网内的钙容量。不管有无 ISO存在 ,胞内钙释放量总是只占肌浆网内钙容量的一部分。在正常情况下 ,心肌的钙释放量有较大的储备能力 ,且此储备可因β-肾上腺素受体的激活而动员。  相似文献   
999.
Primary cardiac T-cell lymphoma   总被引:1,自引:0,他引:1  
Primary cardiac lymphoma (PCL), defined as a lymphoma clinically mimicking cardiac disease, with the bulk of the tumor located intrapericardially, is extremely rare in immunocompetent patients. Clinical manifestations vary depending on sites of involvement in the heart and include chest pain, arrhythmias, pericardial effusion, and heart failure. Diagnosis is often difficult and may require invasive procedures; in some cases, diagnosis is not made until autopsy. Histologically, nearly all cases of PCL reported thus far have been of B-cell origin. In this report, we describe a case of PCL of T-cell origin in an adult immunocompetent patient, the second reported in the literature to the best of our knowledge, and provide a brief overview of the features of previously published PCL cases.  相似文献   
1000.
BACKGROUND: The presence of the A1 allele of the dopamine D2 receptor TaqI restriction fragment length polymorphism has been reported to be associated with an earlier age of onset of alcohol dependence as a marker for severity. METHODS: We tested this hypothesis with special regard to the definition of the age of onset of alcoholism in 243 patients with alcohol dependence, according to DSM-IV criteria assessed by the standardized interview Münchner Composite International Diagnostic Interview (M-CIDI), consecutively admitted for detoxification. Additionally, the Addiction Severity Index (ASI) was performed. The TaqIA polymorphism was amplified by polymerase chain reaction (PCR), and the PCR product was digested by the restriction enzyme TaqI. Patients were subsequently divided into an A1 (presence of at least one A1 allele, n = 88) and an A2 group (absence of an A1 allele, n = 155). The following criteria for different definitions of age of onset were used: (1) age of onset of the first occurring symptom necessary for the diagnosis of alcohol dependence according to M-CIDI; (2) age of onset of the last symptom of alcohol dependence according to M-CIDI; (3) age of onset of more than 3 drinking days per week on a regular basis according to ASI; (4) age of onset of more than 3 drinking days-of more than five drinks per drinking day-or at least one binge drinking episode per week on a regular basis according to ASI. RESULTS: The frequency of the A1 allele in our patient sample was 0.208. No statistically significant association between the A1 allele and the age of onset of alcoholism was found. The mean age of onset according to criterion 1 was 30.4 +/- 10.8 years for the A1 group and 30.2 +/- 10.2 years for the A2 group (p = 0.89); for criterion 2, it was 33.3 +/- 10.0 years for the A1 group and 33.9 +/- 10.2 years for the A2 group (p = 0.77); for criterion 3, it was 18.0 +/- 7.5 years for the A1 group and 18.1 +/- 6.1 years for the A2 group (p = 0.92); and for criterion 4, it was 22.3 +/- 9.7 years for the A1 group and 21.8 +/- 8.5 years for the A2 group (p = 0.76). CONCLUSIONS: No association was found between the A1 polymorphism and age at onset of alcohol dependence according to different specified criteria.  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