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   30985篇
  免费   1575篇
  国内免费   491篇
耳鼻咽喉   122篇
儿科学   658篇
妇产科学   402篇
基础医学   3539篇
口腔科学   187篇
临床医学   4351篇
内科学   4152篇
皮肤病学   137篇
神经病学   1246篇
特种医学   924篇
外科学   2929篇
综合类   5518篇
预防医学   3300篇
眼科学   105篇
药学   3212篇
  15篇
中国医学   1852篇
肿瘤学   402篇
  2023年   331篇
  2022年   724篇
  2021年   1044篇
  2020年   922篇
  2019年   697篇
  2018年   716篇
  2017年   754篇
  2016年   846篇
  2015年   882篇
  2014年   2041篇
  2013年   2077篇
  2012年   1892篇
  2011年   2029篇
  2010年   1572篇
  2009年   1491篇
  2008年   1417篇
  2007年   1393篇
  2006年   1334篇
  2005年   1101篇
  2004年   941篇
  2003年   843篇
  2002年   717篇
  2001年   654篇
  2000年   644篇
  1999年   526篇
  1998年   449篇
  1997年   436篇
  1996年   371篇
  1995年   370篇
  1994年   334篇
  1993年   313篇
  1992年   276篇
  1991年   243篇
  1990年   222篇
  1989年   188篇
  1988年   212篇
  1987年   196篇
  1986年   151篇
  1985年   175篇
  1984年   205篇
  1983年   123篇
  1982年   159篇
  1981年   137篇
  1980年   135篇
  1979年   108篇
  1978年   100篇
  1977年   91篇
  1976年   68篇
  1975年   60篇
  1973年   82篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
ABX MICROS 60-OT型血细胞分析仪的性能评价   总被引:1,自引:0,他引:1  
目的 评价ABXMICROS 60 -OT(以下简称ABX -60 )血细胞分析仪的分析性能 ,推广临床应用。 方法 用EDTA -K2静脉抗凝血标本连续测定和每天随机插入常规标本测定及稀释法分别测定ABX -60的精密度 ,携带污染率和线性性能 ,并与COULTERJT -IR结果进行比较。 结果 ABX -60的批内和批间精密度的变异系数均 <5 ,病人标本测定携带污染率均≤ 0 4% ,对白细胞、红细胞、血红蛋白、血小板测定结果与COULTERJT -IR比较有良好的相关性。 结论 ABX -60是一种较为理想的中档血细胞分析仪 ,适合中心型单位使用。  相似文献   
82.
Computed duplex sonography was used to examine the renal arteries in 36 hypertensive children and adolescents (ages 4–17 years) with arterial hypertension of either renal or non-renal origin. Time-averaged flow velocities, maximum blood flow velocities as well as absolute renal blood flow and renal blood flow per gram kidney weight were measured. Normal flow velocities and normal to elevated renal blood flow volume was found in patients with acute glomerulonephritis and those with signs of chronic glomerulonephritis onset. Patients having advanced stages of chronic glomerulonephritis, on the other hand, were characterized by lower levels of all parameters. Unilateral renal artery stenosis was diagnosed correctly in four patients, although one intra-renal artery stenosis escaped imaging. Scarred kidneys exhibited low-normal or reduced flow velocities and renal blood flow volumes corresponded roughly to kidney size and preservation of normal kidney structure. Hypertension in some patients with normal kidneys showed a tendency to cause higher renal blood flow without consistent acceleration of blood flow velocities. We conclude that duplex sonography is a suitable primary diagnostic tool in measuring blood flow velocities and absolute renal blood flow volume in hypertensive children, thus facilitating the choice of the next diagnostic step.  相似文献   
83.
Formation of intrachondral vessels (cartilage canals) in the proximal femoral epiphysis was studied in 13- to 22-week-old human fetuses using a corrosion casting technique and scanning electron microscopy. Several successive morphological stages of angiogenesis occurring inside the hyaline cartilage were distinguished. The process of cartilage vascularization starts with the formation of hairpin loops sent off from the perichondrial vascular network into the adjacent cartilage. A capillary glomerulus is then formed at the leading end, and the entire vascular unit grows in length, assuming a mushroom-like shape. Its further elongation is accompanied by a backward expansion of the capillary network which surrounds a pair of main vessels (arteriole and venule) like a manchette. The subsequent branching of such primary vascular units proceeds according to the same morphological patterns. The resulting tree-like vascular formations become interconnected via their lateral branches. This study clearly supports the invasion theory of cartilage canal formation.  相似文献   
84.
本文用生物伯德图分析了血压稳定性。按照经典的控制理论,讨论了生物系统的稳定性,提出了血压控制的数学模型。根据生物特点,建立了生物伯德图的表达式。作为系统稳定性的指标,增益裕量和相位裕量可以用作图法求得,也可以用计算机求解。实验结果与理论分析能很好地符合。  相似文献   
85.
心脏病患者血清七种元素含量与血压及生化指标的关系   总被引:31,自引:0,他引:31  
我们检测了心脏病患者血清微量元素Zn、Cu、Fe和常量元素K、Na、Ca、Mg的含量,并与血压及生化指标作相关分析。结果发现心脏病患者K和Ca/Mg显著低于对照组,而Na、Mg、Zn、Fe和Na/K、Zn/Cu则显著高于对照组。K、Ca/Mg与血压呈负相关,而Na、Zn、Fe、Zn/Cu和Na/K与血压呈正相关;Fe与红细胞压积(Hct)呈正相关;Zn/Cu与Hct、甘油三酯、极低密度脂蛋白均呈正相关,而与高密度脂蛋白呈负相关。  相似文献   
86.
强噪声对大鼠血液粘度血糖及几种酶的影响   总被引:9,自引:0,他引:9  
本文检测强噪声刺激12小时大鼠血液流变学九项指标,胆碱酯酶和谷丙转氨酶活力及血糖浓度,与对照组比较,其结果显示:(1)低切粘度,红细胞电泳时间和全血还原粘度明显增高(P<0.05;P<0.05和P<0.01);(2)真性和假性胆碱酯酶活力明显增高(二者均P<0.01);(3)血清谷丙转氨酶活力和血清葡萄糖浓度显著增高(P<0.01和P<0.05)。揭示强噪声作用后机体听觉外系统发生明显变化,长期暴露后必将严重损伤全身性调节功能而引起脏器损害与疾病。  相似文献   
87.
Summary The aim of this study was to evaluate the level of physical capacity in a female hospital population of Paris and its suburbs. A total of 1505 women working in the selected departments filled in a questionnaire concerning their working conditions, life habits and health and also attended a medical examination. The effort test performed consisted in flexing the legs 20 times with the chest held straigt, in 40 s. The heart rates were measured for the first, the second and the third minutes of recovery (first 15 s multiplied by 4). The blood pressure was measured just after the heart rate, for the first and the third minute. Recovery indices have been constituted from the results. The respective weights of anthropometric and sociodemographic risk factors for recovery indices were studied in multiple logistic regression models. The classification enables us to consider about 25%–30% of our population as having a satisfactory physical capacity, about 26%–27% as having an acceptable capacit, and about 24%–27% as having a weak capacity. About 21% of the population presented an excessive pressure reaction and 44% a questionable pressure reaction. Our results concerning the level of physical capacity of the female nursing staff should be taken into account especially in the future planning of work loads and architectural choices, which must avoid excessive physical burdens in relation to this level. An improvement in the level of physical capacity could be envisaged as well.  相似文献   
88.
We have previously demonstrated that alcoholics with transitory (< 72 hr) elevations in blood pressure (BP) during withdrawal continue to show residual cardiovascular dysregulation up to 4 weeks of abstinence. The present study replicates and extends these findings. Alcoholic inpatients were divided into three subgroups ( ns = 14) based on BP during the first 72 hr of withdrawal: transitory hypertensives (tHTs; BP > 160/95 mm Hg), transitory borderline hypertensives (tBHs; 140/90 BP < 160/95), and normotensives (NTs; all BPs < 140/90). All patients had normal resting pressures after 72 hr of withdrawal. At 3–4 weeks postadmission, the alcoholics and 14 nonalcoholic controls (CONTs) were tested at rest and during a 5-min handgrip task. The tHTs showed an exaggerated systolic and diastolic BP response to handgrip compared with NTs and CONTs, with tBHs intermediate ( ps < 0.05). Drinking history showed the tHTs had the highest reported level of alcohol consumption and severity of withdrawal symptoms ( ps < 0.05). Regression analyses indicated that consumption of hard liquor was the variable most predictive of admission BPs; further, parental history of hypertension potentiated this relationship for systolic BP. Age and consumption of nicotine and caffeine were not significant predictors of admission BP. The results suggest a persistent cardiovascular dysregulation in alcoholics showing transient hypertensive withdrawal BPs. These alcoholics may be at increased risk for future alcohol-related cardiovascular disorder.  相似文献   
89.
Lens opacity studies were performed using an electronic Lens Opacity Meter (Interzeag Opacity Lensmeter 701) in a population (n = 321) with ischaemic heart disease. These patients are participating in a trial targetting at the reduction of mortality and incidence of myocardial infarction using a cholesterol-lowering drug, simvastatin. A separate study to evaluate the reliability of the method showed good reproducibility. Repeated measurements after a short time-interval (2–10 days) gave statistically lower opacity values either due to a change in lens transparency or perhaps a change in pigment and cell dispersion in the acqueous caused by repeated mydriasis. Lens opacity values showed a highly significant positive correlation to age. Serum cholesterol, systolic blood pressure and smoking habits showed no significant correlations to the levels of lens opacity when adjustments for age were made.Abbreviations HMG-CoA hydroxy-methylglutarylcoenzyme A - 4S Scandinavian Simvastatin Survival Study - LOM lens opacity meter  相似文献   
90.
股骨颈骨折后选择性血管造影评价股骨头血液循环   总被引:13,自引:0,他引:13  
目的 探讨选择性血管造影检查对评价股骨颈骨折后早期股骨头血液循环损伤及影响因素的价值。方法采用选择性旋股动脉及支持带动脉造影(DSA),对9例2~23天内单侧股骨颈骨折患者血管损伤和血液循环改变进行评价。结果髋关节囊内出血2例,骨内出血4例,下、后支持带动脉损伤和血管移位各3例。患髋牵引时,除外下支持带动脉,其他支持带动脉无显影或仅显示起始部主干,相应股骨头颈部几无灌注成像,静脉显影延迟;髋关节维持伸直内旋位或囊内注入生理盐水后造影,所有支持带动脉无明确显影或仅显示其主干,股骨头颈部无灌注、染色,静脉显影延迟。结论选择性旋股内、外侧动脉DSA技术是一项准确评价股骨颈骨折后股骨头血液循环损伤及影响因素的微创性检查方法;股骨头血液循环受髋关节体位、囊内压和牵引等因素影响;牵引可导致或加重股骨颈骨折后股骨头缺血。  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