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   211826篇
  免费   19968篇
  国内免费   13892篇
耳鼻咽喉   2271篇
儿科学   2921篇
妇产科学   1808篇
基础医学   19565篇
口腔科学   3646篇
临床医学   25450篇
内科学   26548篇
皮肤病学   2452篇
神经病学   8875篇
特种医学   8232篇
外国民族医学   78篇
外科学   22759篇
综合类   44959篇
现状与发展   64篇
一般理论   14篇
预防医学   18175篇
眼科学   4473篇
药学   22232篇
  252篇
中国医学   15737篇
肿瘤学   15175篇
  2024年   806篇
  2023年   2925篇
  2022年   7527篇
  2021年   9931篇
  2020年   7943篇
  2019年   6061篇
  2018年   6493篇
  2017年   6599篇
  2016年   6164篇
  2015年   9941篇
  2014年   12117篇
  2013年   12892篇
  2012年   18628篇
  2011年   19857篇
  2010年   14980篇
  2009年   12465篇
  2008年   14081篇
  2007年   13289篇
  2006年   12442篇
  2005年   10506篇
  2004年   7573篇
  2003年   7065篇
  2002年   5727篇
  2001年   4171篇
  2000年   3254篇
  1999年   2433篇
  1998年   1392篇
  1997年   1321篇
  1996年   1072篇
  1995年   976篇
  1994年   745篇
  1993年   486篇
  1992年   519篇
  1991年   451篇
  1990年   406篇
  1989年   322篇
  1988年   276篇
  1987年   269篇
  1986年   211篇
  1985年   177篇
  1984年   133篇
  1983年   96篇
  1982年   84篇
  1981年   89篇
  1980年   68篇
  1979年   87篇
  1978年   64篇
  1977年   54篇
  1974年   61篇
  1973年   64篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The chick chorioallantoic membrane was used to determine whether the carotid atherosclerotic plaque stimulates angiogenesis. Carotid endarterectomy specimens (1 mm3) with fibromuscular plaque (n = 8) and complicated plaque (n = 11) were implanted on the membrane on day nine of incubation and the response evaluated on day 11. Following fixation in situ with 10% formalin the angiogenic response was evaluated by: (1) examining whole membrane mounts, (2) quantitatively from a vascular density index and (3) from a histological study. Unmanipulated chorioallantoic membrane (n = 11) and plaque boiled prior to implantation (n = 6) served as controls. The vascularity of whole mounts of both fibromuscular and complicated plaque was greater than the controls. Vessel density of the membrane was estimated by counting the number of vessels intersecting four concentric circles (144.5 mm total circumference) placed on the formalin fixed membrane. The vascular density index due to the fibromuscular plaque (390.6 +/- 8.3) and complicated plaque (391.0 +/- 14.9) were similar (P greater than 0.9) but were significantly greater (P less than 0.001) than the unmanipulated membrane (327.9 +/- 5.6) or after treatment with the boiled plaque (283.8 +/- 15.6). Transforming growth factor beta 1 confirmed the validity of the experimental model to study angiogenesis. The histology of the chorioallantoic membrane due to either type of plaque was similar. Numerous vessels surrounded the plaque, and intraplaque vessels containing nucleated chick erythrocytes were observed. Although scattered vessels surrounded the boiled plaque, intraplaque vessels were not observed. This study demonstrates that the atherosclerotic plaque has angiogenic properties that may account for the increase in vasa vasorum that is associated with the plaque.  相似文献   
82.
The role of human spumaretrovirus (HSRV) infections in the pathogenesis of multiple sclerosis (MS) was investigated with recombinant HSRV env-specific enzyme-linked immunosorbent assay. The presence of HSRV antibodies was determined in pairs of serum and cerebrospinal fluid (CSF) samples from 60 MS patients. In 7 of these patients serial serum and CSF samples were obtained in relation to the clinical activity of the disease during a period of 2 years. No increased antibody reactivity was demonstrable in the MS population compared with 14 aseptic meningitis patients, 50 blood donors and 16 healthy controls. Slightly elevated levels of antibodies were demonstrable in serum and/or CSF in 4 MS patients but also in 1 patient with aseptic meningitis, 1 blood donor and 1 child. No marked serum or CSF HSRV antibody fluctuation was observed in the MS patients followed longitudinally. Thus, this study does not support the involvement of HSRV in the pathogenesis of MS.  相似文献   
83.
用免疫组织化学ABC法,研究了降钙素基因相关肽(CGRP)免疫反应神经纤维在大鼠胆总管末端与十二指肠连接处的分布。大鼠的胆总管末端有较丰富的CGRP免疫反应神经纤维,它们多呈串珠(膨体)状,少数为无膨体的细长纤维。CGRP-IR纤维主要分布肌层及血管周围,在神经纤维的附近可见到含CGRP-IR阳性颗粒的肥大细胞。本实验为神经免疫调节机制的研究提供了形态学依据。  相似文献   
84.
前列腺素E1对大鼠肝脏缺血再灌注损伤的保护作用   总被引:2,自引:0,他引:2  
目的 探讨前列腺素E1(PGE1)对肝脏 因再灌注损伤的保护作用。方法 制作常温下大鼠部分肝叶缺血再灌注模型,于缺血前经门静脉给予PGE1,45min后恢复血流灌注,并于1h后取门静脉血测定血清谷草转氨酶(GOT)、谷丙转氨酶(GPT)、乳酸脱氢酶(LDH)、肿瘤坏死因子-α(TNF-α)及内皮素1(ET-1),同时取缺血肝叶行病理组织学检查。结果 缺血再灌注组GOT、GPT、LDH及TNF-α和ET-1均明显高于正常对照组,PGE1组则明显低于缺血再灌注组。PGE1组的肝脏病理组织学改变明显轻于缺血再灌注组,并接近正常对照组。结论 PGE1对肝缺血再灌注具有保护作用。  相似文献   
85.
In a prospective multicenter study of 1,052 patients with clinical signs of a scaphoid fracture, mammo-graphic films and fine intensifying screens were used at the radiographic examination. 5 standardized projections including 3 special projections focused on the scaphoid were taken. 150 fractures were diagnosed at the first examination but in 10 cases the fracture was first diagnosed at a second radiographic examination after 10-14 days.

The second examination still seems mandatory despite the use of high quality radiographs with optimal spatial resolution and contrast, and the value of supplementary special projections.  相似文献   
86.
目的 了解血胱蛋白酶抑制剂 (cystatin)C和内生肌酐清除率 (Ccr)与肾脏病理变化的关系。 方法 选择 1999年 1月~ 2 0 0 3年 2月因各种肾脏疾病收治入院行肾穿刺活检术的患儿共 12 4例 ,入院后查血cys tatinC和Ccr ,并行肾穿刺活检术以了解肾脏病理变化 ,然后通过相关及多元线性回归分析了解血cystatinC和Ccr与肾脏病理变化的关系。结果 血cystatinC与肾脏病理变化的复相关系数 (R) =0 .6 91(P <0 .0 1) ,血cys tatinC与肾脏病理变化之间存在直线关系 ,其回归方程为Y =0 .6 0 5 +0 .30 7X1+0 .4 93X2 (F =5 5 .18,P <0 .0 1)。Ccr与肾脏病理变化的R =0 .4 0 5 (P <0 .0 1) ,Ccr与肾脏病理变化之间亦存在直线关系 (F =11.89,P<0 .0 1)。结论 血cystatinC比Ccr更能反映肾脏病理变化的严重程度。血cystatinC和Ccr均与肾间质的变化密切相关 ,尤以血cystatinC更敏感。因此 ,血cystatinC可作为判断肾脏疾病预后的重要参考指标 ,以及时了解肾脏病理变化采取有效的治疗。  相似文献   
87.
The experiments were performed on 34 dogs. The subcutaneous injection of boiled pancreatic juice was established to increase the survival of dogs in acute destructive pancreatitis (p < 0.001) and to decrease the specific volume damage to acinar (p < 0.01) and interstitial (p < 0.05) pancreatic tissue. It was also shown that boiled pancreatic autojuice exerted the therapeutic effect in chronic pancreatitis complicated by pancreatic fistulas. Five peptide components with a molecular mass from 4168 D to 1000 were discovered in the canine boiled pancreatic juice by liquid high pressure chromatography. Fractions with a molecular mass between 2187 and 1348 D were found to correspond to biologically active peptides, in particular to somatostatin. It is assumed that the therapeutic effect of boiled pancreatic juice used in acute pancreatitis may be due to somatostatin. Apparently pancreatic juice may turn an efficient therapeutic agent in acute pancreatitis and pancreatic fistulas.  相似文献   
88.
Background: Despite the fact that obesity is a known risk factor for cardiovascular disease, many studies have failed to demonstrate that obesity is independently associated with an increased risk of cardiovascular morbidity and mortality in nondiabetic patients undergoing coronary artery bypass graft surgery. The authors investigated the influence of obesity on adverse postoperative outcomes in diabetic and nondiabetic patients after primary coronary artery bypass surgery.

Methods: A retrospective cohort study of patients undergoing primary coronary artery bypass surgery (n = 9,862) between January 1995 and December 2004 at the Texas Heart Institute was performed. Diabetic (n = 3,374) and nondiabetic patients (n = 6,488) were classified into five groups, according to their body mass index: normal weight (n = 2,148), overweight (n = 4,257), mild obesity (n = 2,298), moderate obesity (n = 785), or morbid obesity (n = 338). Multivariate, stepwise logistic regression was performed controlling for patient demographics, medical history, and preoperative medications to determine whether obesity was independently associated with an increased risk of adverse postoperative outcomes.

Results: Obesity in nondiabetic patients was not independently associated with an increased risk of adverse postoperative outcomes. In contrast, obesity in diabetic patients was independently associated with a significantly increased risk of postoperative respiratory failure (odds ratio [OR], 2.26; 95% confidence interval [CI], 1.41-3.61; P < 0.001), ventricular tachycardia (OR, 2.27; 95% CI, 1.18-4.35; P < 0.02), atrial fibrillation (OR, 1.56; 95% CI, 1.03-2.38; P < 0.04), atrial flutter (OR, 2.38; 95% CI, 1.29-4.40; P < 0.01), renal insufficiency (OR, 1.66; 95% CI, 1.10-3.41; P < 0.03), and leg wound infection (OR, 5.34; 95% CI, 2.27-12.54; P < 0.001). Obesity in diabetic patients was not independently associated with an increased risk of mortality, stroke, myocardial infarction, sepsis, or sternal wound infection.  相似文献   

89.
目的:通过传染性非典型肺炎(SARS)患者泪液病毒特异性抗体的检测,寻找SARS病毒是否通过泪液或眼结膜传播的理论依据,了解泪液和血液中SARS病毒特异性抗体检测结果的一致性程度。方法:用酶联免疫吸附法(ELISA)检测18例不同病程的SARS患者泪波及血清SARS病毒特异性抗体。结果:18例SARS患者泪液中的特异性IgM类和IgG类抗体均为阴性,而同组患者有13例其血液中的特异性IgM类和IgG类抗体呈阳性。结论:SARS病毒可能不通过泪液或结膜传播。  相似文献   
90.
赵伟  任霖  张卫泽 《宁夏医学杂志》2004,26(11):701-702
目的 比较高血压合并阻塞性睡眠呼吸暂停患者的短期血压变异性。方法 将155例分为对照组、高血压组、高血压合并轻度或中重度阻塞性睡眠呼吸暂停组,EE较患者不同活动状态的短期血压变异性。结果 高血压合并中重度阻塞性睡眠呼吸暂停组患者睡眠期间和早晨血压变异系数分别为:收缩压18.69、21.32;舒张压19.41、23.61,明显高于其他各组。结论 夜间睡眠期间和早晨短期血压变异性增加,是高血压合并中重度阻塞性睡眠呼吸暂停患者夜间和早晨心血管事件发生率增加的重要危险因素。  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