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   37485篇
  免费   1949篇
  国内免费   812篇
耳鼻咽喉   137篇
儿科学   737篇
妇产科学   459篇
基础医学   4351篇
口腔科学   255篇
临床医学   5119篇
内科学   4599篇
皮肤病学   184篇
神经病学   1400篇
特种医学   1092篇
外科学   3331篇
综合类   7125篇
预防医学   4253篇
眼科学   175篇
药学   4097篇
  24篇
中国医学   2376篇
肿瘤学   532篇
  2024年   71篇
  2023年   426篇
  2022年   910篇
  2021年   1325篇
  2020年   1176篇
  2019年   928篇
  2018年   928篇
  2017年   980篇
  2016年   1010篇
  2015年   1093篇
  2014年   2516篇
  2013年   2497篇
  2012年   2418篇
  2011年   2509篇
  2010年   1950篇
  2009年   1818篇
  2008年   1752篇
  2007年   1735篇
  2006年   1681篇
  2005年   1382篇
  2004年   1157篇
  2003年   1005篇
  2002年   860篇
  2001年   771篇
  2000年   723篇
  1999年   600篇
  1998年   511篇
  1997年   495篇
  1996年   425篇
  1995年   409篇
  1994年   386篇
  1993年   349篇
  1992年   296篇
  1991年   267篇
  1990年   252篇
  1989年   211篇
  1988年   238篇
  1987年   217篇
  1986年   171篇
  1985年   207篇
  1984年   233篇
  1983年   136篇
  1982年   178篇
  1981年   157篇
  1980年   151篇
  1979年   113篇
  1978年   108篇
  1977年   90篇
  1976年   71篇
  1973年   83篇
排序方式: 共有10000条查询结果,搜索用时 28 毫秒
101.
Summary Biopsy specimens from the skin and subcutaneous fat tissue of four cases with neonatal subcutaneous fat necrosis were made and investigated by light and electron microscopy at 2, 4, and 6 weeks, and 5 months (Case 2) from the onset of the disease. Three stages of ultrastructural change of fat cells were observed. The evolution of crystal formation in the fat cells was seen and phagocytosis of crystals and fat droplets by macrophages and foreign-body giant cells was also noted. In the light microscope accumulation of calcium concretions in the spaces between and inside the fat cells was found. In the electron microscope we detected foci of highly electrondense granules, which were similar in distribution and structure to calcium salts stained with the von Kossa method. Changes in small and medium size blood vessels were observed.This work was written during a stay supported by Max-Planck-Gesellschaft from Dec. 1. 1973 to March 31. 1975 in the Max-Planck-Institut für Klinische und Physiologische Forschung (W.G. Kerckhoff-Institut), Bad Nauheim, West Germany (Director: Prof. Dr. Wolfgang Schaper)  相似文献   
102.
Summary Cardiovascular and sympathetic nervous system effects of the mixed 2-adrenoceptor and imidazoline receptor agonist rilmenidine were studied in conscious rabbits chronically instrumented for the recording of the firing rate of renal sympathetic fibers. Separate experiments were carried out on pithed rabbits with electrically stimulated (2 Hz) sympathetic outflow. Drugs were administered intravenously in a cumulative manner.In conscious rabbits, rilmenidine 0.1, 0.3 and 1.0 mg kg–1 dose-dependently lowered blood pressure, renal sympathetic nerve activity, heart rate and the plasma concentration of noradrenaline and adrenaline. The effect on blood pressure and plasma catecholamines was maximal after 0.3 mg kg–1 whereas heart rate and renal sympathetic nerve activity decreased further after rilmenidine 1.0 mg kg–1. Yohimbine 0.1 and 0.5 mg kg–1, when injected subsequently, attenuated and at the higher dose abolished all effects of rilmenidine. The effects of rilmenidine were also antagonized by the 2-adrenoceptor antagonist 2-(2,3-dihydro-2-methoxy-1,4-benzodioxin-2-yl)-4,5-dihydro-1H-imidazole HCl (RX821002; 0.1 and 0.5 mg kg–1). Yohimbine 0.1 and 0.5 mg kg–1 did not attenuate or attenuated only slightly the decrease of heart rate and renal sympathetic nerve activity produced by infusion of vasopressin. In pithed rabbits with electrically-stimulated sympathetic outflow, yohimbine 0.1 submaximally and yohimbine 0.5 mg kg–1 maximally increased the plasma noradrenaline concentration.The experiments show by direct measurement of sympathetic nerve firing and plasma catecholamines that rilmenidine causes sympathoinhibition in conscious rabbits, presumably through central sites of action. The antagonism by yohimbine, at doses which are selective for 2-adrenoceptors (vs. imidazoline receptors), demonstrates the involvement of 2-adrenoceptors in the sympatho-inhibition.Correspondence to: B. Szabo at the above address  相似文献   
103.
The effect of calcium-balanced heparin (471896, CIBA CORNING) on blood gas and electrolyte analysis was evaluated, by comparing with that of sodium heparin (Na heparin). One ml of whole blood was collected into a syringe, which contained calcium-balance heparin (Ca balanced heparin) or Na heparin. 122 pairs of blood samples obtained from 15 patients were analyzed for Na, K, ionized calcium (Ca(++)), total hemoglobin, pH, P(CO)(2), and P(O)(2) by an automatic blood gas and electrolyte analyzer, CIBA CORNING model 288. There was a significant difference ( P < 0.05) in pH, P(CO)(2), Na, and Ca(++) between the two different groups. Ca(++) concentration was significantly less in Na heparin group than in Ca balanced heparin group, probably due to more chelation of Ca(++) by Na heparin than Ca balanced heparin. The present study suggests that the Ca balanced heparin has minimal effect on the blood gas and electrolyte analysis, and is a suitable anticoagulant for the Ca(++) measurement.  相似文献   
104.
目的 为探讨血液病鼻衄的理想处理方法。方法 对23例治疗组患者采用浸有凝血酶2000Iu/ml的明胶海绵局部敷贴出血点,3~4日后用烧伤膏创面换药;34例对照组采用凡士林纱条填塞止血。结果 治疗组有效率86.9%,显效率69.7%;对照组分别是58.5%和35.3%。两种方法有显著性差异(P〈0.01)。结论 用凝血酶敷贴出血点及创面烧伤膏换药是治疗血液病鼻衄一种安全、有效的方法。  相似文献   
105.
本文通过临床常用的HCT、FIb、ESR与血流变中全血粘度、血浆粘度和红细胞聚集性之间相关性的实验对照观察、理论分析 ,认为血细胞比容 ,血沉和纤维蛋白原检测反映血液浓度、粘度、聚集、凝血状态是有一定相关价值。因此 ,再配合临床必要的生化实验 ,如血糖、血脂等检测采用微机对检测数据处理对心脑血管疾病的预测、疗效观察具有更实用的价值  相似文献   
106.
妇科术后硬膜外腔注射吗啡镇痛效果观察   总被引:1,自引:0,他引:1  
对妇科术后硬膜外腔注射吗啡镇痛效果进行观察分析探讨。对3a来我院使用术后硬膜外腔注射吗啡镇痛效果进行评定,对血压、脉博等情况观察进行总结分析。结果:硬膜外腔注射吗啡术后镇痛效果优85.6%,良6.8%。副作用有血压下降达27.8%、恶心呕吐15.5%,头晕23.0%。  相似文献   
107.
ObjectiveTo check incidence of Asymptomatic Leishmania donovani reporting to Armed Forces Institute of Transfusion Rawalpindi.Material and MethodsTwo thousand (n = 2000) consecutive healthy voluntary blood donors were tested for 18 s rRNA by Real time Polymerase chain reaction. One thousand (n = 1000) subject’s permanent resident of Azad Kashmir along with a thousand (n = 1000) healthy voluntary blood donors from rest of Pakistan were included. The study was carried out over a period of three months Jun – Aug 2020.ResultsTotal of 2000 blood donors were enrolled in the study, all were males with age ranging from 16 to 60 years. Stratification based on residence, 1000 (50 %) resided in the Azad kashmir, 349 (17.45 %) were from Islamabad and Rawalpindi, 541 (27.05 %) from Punjab mainly residing in Lahore and Multan, 110 (5.5 %) were from other cities of Pakistan. Grouping on the basis of age, 55.25 % ( n = 1105) of the donors were 16–25 years old, 19.45 % ( n = 389) were in age range of 26–40 years old, 15.55 % ( n = 311) were 41–50 years old and 9.75 % ( n = 195) 51–60 years old. No donor was diagnosed as an asymptomatic carrier.ConclusionScreening of blood donors for Leishmania donovani is not recommended.  相似文献   
108.
109.
In this study we have investigated the effects of breath holding and of the physical properties of gases on four different respiratory dead spaces (V D): the Fowler, the physiological, the washout and the inert gas dead space. The experiments were performed with dogs which were ventilated artifically with breathing patterns with different post-inspiratory breath holding times (t a) of 0, 0.5, 1.0 and 2.0 s. Tracer amounts of acetone, ether and enflurane were infused continuously into a peripheral vein and a bolus of a mixture of krypton, Freon12 and SF6 was introduced into the peritoneal cavity. After reaching steady state, samples of arterial blood, mixed venous blood and mixed expired air were taken simultaneously. From the partial pressures (P a, P ¯V and P respectively) we determined the excretion (=P/P¯V), retention (R=Pa/P¯V) and the physiological dead space fraction (V D,phys/V T=(1 P/Pa) for each gas, where V T is tidal volume. Further, we recorded the expirograms of the six tracer gases and of CO2 from which the Fowler dead space fractions (V D,Fowler/V T) of the different gases were determined. Also the washout dead space fractions (V D,washout/V T) for He and SF6 were determined as well as the inert gas dead space fraction (V D,MIGET/V T) with the use of the multiple inert gas elimination technique (MIGET).With the exception of V D,phys/V T for SF6, all dead space fractions decreased with increasing t a. V D,phys/V T for the poorly soluble gas SF6 was considerably larger than V D,phys/V T for the remaining gases. For the highly soluble acetone V Fowler/V T was considerably smaller than V D,Fowler/V T for the other gases. V D,washout,SF6/V T was always larger than V D,washout,He/V T and V D,Fowler,SF6/V T. Further, V D,phys/V T was larger than V D,Fowler/V T for SF6 and acetone. However, for gases with intermediate solubility in blood V D,phys/V T tended to be smaller than V D,Fowler/V T. We conclude that the respiratory dead spaces are affected by the breathing pattern and by the physical properties of gases, i.e. their diffusivity in alveolar gas and their solubility in blood or lung tissue.  相似文献   
110.
The present study was conducted to assess the feasibility of laser Doppler velocimetry in young infants, as a prelude to ultimately undertaking such measurements in premature infants. A portable, unidirectional laser Doppler velocimeter was developed based on a Kowa RC-2 hand-held fundus camera. Six infants between 1 and 21 weeks of age were studied. Relative red blood cell velocity (fmax) at the centre of retinal arteries was measured over approximately 10 heart cycles. A pulsatility parameter (P=1–fmax.dia/fmax.sys), a summary index of vascular status, was determined from the average diastolic and systolic values of fmax. Velocity waveforms were obtained in four of the six infants. Arterial pulsatility for the group was 0.63±0.13. Precise non-invasive measurement of arterial red blood cell velocity waveforms in young infants was achieved. The high signal-to-noise ratio and temporal resolution of this data suggest that relative measurements of retinal blood flow may permit assessment of haemodynamic changes in premature infants.  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