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   1249226篇
  免费   74712篇
  国内免费   1979篇
耳鼻咽喉   17425篇
儿科学   39132篇
妇产科学   31835篇
基础医学   174848篇
口腔科学   32979篇
临床医学   111838篇
内科学   239130篇
皮肤病学   27081篇
神经病学   98229篇
特种医学   48589篇
外国民族医学   214篇
外科学   187291篇
综合类   23862篇
现状与发展   4篇
一般理论   459篇
预防医学   87378篇
眼科学   28990篇
药学   96747篇
  35篇
中国医学   2996篇
肿瘤学   76855篇
  2021年   10326篇
  2019年   10728篇
  2018年   14408篇
  2017年   11215篇
  2016年   12748篇
  2015年   14444篇
  2014年   19919篇
  2013年   29523篇
  2012年   40754篇
  2011年   43299篇
  2010年   25228篇
  2009年   23608篇
  2008年   40387篇
  2007年   43234篇
  2006年   43445篇
  2005年   42103篇
  2004年   40351篇
  2003年   38626篇
  2002年   37281篇
  2001年   61425篇
  2000年   62548篇
  1999年   52445篇
  1998年   14655篇
  1997年   12924篇
  1996年   12667篇
  1995年   11848篇
  1994年   10698篇
  1993年   10133篇
  1992年   38782篇
  1991年   37188篇
  1990年   36564篇
  1989年   35070篇
  1988年   31664篇
  1987年   30676篇
  1986年   29019篇
  1985年   27332篇
  1984年   20330篇
  1983年   17220篇
  1982年   10379篇
  1979年   17782篇
  1978年   12270篇
  1977年   11006篇
  1976年   9526篇
  1975年   10605篇
  1974年   12217篇
  1973年   11725篇
  1972年   11115篇
  1971年   10352篇
  1970年   9466篇
  1969年   9131篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
A heterocentric aplanatic contact of one piece has been designed for optimal efficiency of laser surgery for ALT and YLT in the angle of the anterior chamber.  相似文献   
994.
Since more than a century ago, temperatures above 40 degrees C have been known to be effective in cancer treatment. Since that time numerous studies have documented that hyperthermia alone causes tumor regression and that the therapeutic effect depends on the amount and duration of heat delivered to a malignant tumor. However, after it was shown that heat combined with irradiation or chemotherapy potentiates the effect of hyperthermia, both thermoradiotherapy and thermochemotherapy were applied in experimental and clinical studies in several medical specialties. In ophthalmic oncology both retinoblastoma and uveal melanoma are treated by irradiation combined with local hyperthermia. In the present paper the use of ultrasound and microwave energy as locally applicable heat sources in intraocular malignancies is described and their suitability discussed. As is the case with malignant skin tumors and malignant tumors of the gastrointestinal and urogenital systems, malignant ocular tumors are accessible to externally applied heat and can thus be treated well by ultrasound and microwave hyperthermia. On the basis of experimental and clinical results gained with both ultrasound and microwave energy the advantages and drawbacks of these two technical modalities in intraocular tumor therapy are pointed out.  相似文献   
995.
Two methods of measuring lacrimation with a cotton thread and fluorescein have been described hitherto. Method 3 is intended for testing lacrimal flow in wearers of soft contact lenses. Fluorescent paper can be used to facilitate the measuring procedure. The method has been shown to be reliable in numerous control tests on subjects with normal eyes and in comparisons with the authors' methods 1 and 2. With the test, values of less than 5 mm indicate severe lacrimal deficiencies.  相似文献   
996.
Recently introduced prosthetic socket designs for the above-knee amputee (AKA) feature a narrow medial-lateral dimension and emphasize maintenance of the residual limb in full physiologic adduction. Quantitative data on the effect of frontal plane limb position on the isometric hip abductor strength of ten otherwise healthy AKAs were obtained in the standing position. Residual limb isometric and isokinetic abductor strength was also measured and compared with that of the intact limb and with that of ten healthy age-, sex-, and height-matched control subjects using an identical technique. The testing hardware consisted of a modified Cybex II Isokinetic Dynamometer with a custom-made pelvis and trunk stabilizing device. Anthropometric measurements were taken. Results showed an essentially linear increase in residual limb abduction strength with progressive adduction from 30 degrees abduction to 16 degrees adduction. The average increase in abduction torque was .97% (range .29 to 1.5) of the peak neutral position strength per degree of change in femur angle when corrected for the effect of gravity. Similar strength increases with adduction of the femur were found for intact and control limbs. Mean residual limb isometric abduction torque measured 30% less than the intact limb value (p = .0018). The difference between the intact and the control limb mean isometric abduction torques was less than 1%. Isokinetic testing was technically more difficult than isometric testing but revealed similar weakness of the residual limb abductors when compared to the intact and control limbs.  相似文献   
997.
Pharmacokinetics may be utilized as a tool in the drug development process, either with respect to therapeutics or in allowing a drug's disposition characteristics to be defined. If two drugs of the same class have a similar dose-efficacy profile, then the favourable/unfavourable balance of the pharmacokinetic characteristics of the drugs may determine the drug of choice. Pantoprazole, a proton pump inhibitor, appears to meet the above criteria and has been found to exhibit reliable, predictable pharmacokinetic characteristics as opposed to other members of the class. The pharmacokinetics of pantoprazole over a range of intravenous and oral doses are described in healthy volunteers and are compared with values obtained for omeprazole. Studies in patients with severe cirrhosis, renal failure, and in the elderly are also described as well as potential interactions due to food and five other drugs.  相似文献   
998.
Study Objective . To compare the frequency, severity, and time course of venous irritation after administration of a single intravenous dose of phenytoin with an equimolar dose of fosphenytoin, a water-soluble phenytoin prodrug. Design . Randomized, double-blind, two-period, crossover study. Setting . University hospital clinical research unit. Patients . Twelve healthy volunteers within 15% of ideal body weight and with no clinically significant abnormalities on physical examination, medical history, or laboratory assessment. Interventions . Volunteers randomly received a 30-minute infusion of phenytoin sodium 250 mg (250 mg/5 ml) or an equimolar dose of fosphenytoin 375 mg (375 mg/5 ml). Subjects returned for the crossover treatment 14–21 days later. Measurements and Main Results . Subjects assessed venous irritation (pain, burning, itching), and investigators evaluated phlebitis (erythema, swelling, tenderness), induration, exudation, and cording. Phenytoin was associated with a significantly higher degree of pain at the infusion site in all subjects and a significant degree of phlebitis in eight subjects (p<0.05); cording occurred in six subjects. The time course of phenytoin-induced phlebitis was bimodal. Erythema and tenderness were prominent at the end of the infusion and again at 24 hours. Cording was first noted between 24 hours and 1 week after infusion. In contrast, fosphenytoin was associated with mild pain in two subjects, one incident of phlebitis, and no erythema or cording. Conclusions . Fosphenytoin administration resulted in significantly less venous irritation and phlebitis compared with an equimolar dose of phenytoin. The clinical use of this water-soluble phenytoin prodrug should minimize the frequency and severity of infusion-site reactions and should allow convenient, rapid, intravenous administration of drug, undiluted or admixed with intravenous solutions.  相似文献   
999.
1. Global myocariial ischaemia (MI) for periods greater tan 5 min caused an inhibition of phosphatidylinositol specific phospholipase C (PtdIns-PLC) activity. 2. Two min reperfusion following a 20 min MI period, a time point associated with reperfusion-induced arrhythmias, resulted in an activation of PtdIns-PLC activity, dependent on endogenous noradrenaline and mediated via al-adrenoceptors. 3. This 2 min reperfusion response, in contrast to healthy myocardium, resulted in: (i) enhanced PtdIns-PLC activity; (ii) increased sensitivity to endogenous noradrenaline; (iii) rapid increases in inositol(1,4,5)trisphosphate (Ins(1,4,5)P3); and (iv) PLC hydrolysis primarily of PtdIns(4,5)P2, such that the majority of InsP isomers derive from Ins(1,4,5)P3. 4. Together, these data suggest a functional role for Ins(1,4,5)P3 under postischaemic reperfusion conditions, and provide a possible link between al-adrenoceptor stimulation of the PtdIns turnover pathway and reperfusion injury.  相似文献   
1000.
1. Since plasma renin activity is increased in cyclosporin A (CsA)-induced hypertension in the rat, the role of the vascular renin-angiotensin system (RAS) in CsA-induced hypertension was investigated in rat mesenteric resistance vessels. 2. Female Wistar rats received CsA (10 mg/kg per day, s.c.) or vehicle for 30 days. CsA treatment increased tail-cuff systolic blood pressure (CsA treated 135 ± 3 mmHg vs control 125 ± 1 mmHg, P<0.0001). 3. Mesenteric resistance arteries (200–300 μm) were isolated and mounted in a microvessel myograph. Concentration-response curves to tetradecapeptide renin substrate (10-11-10?6 mol/L), angiotensin I (10-l1-10?6 mol/L) and angiotensin II (10-12-10?6 mol/L) showed no differences between CsA-treated and control groups. 4. Mesenteric vascular angiotensin-converting enzyme (ACE) characteristics were determined by radioligand binding. There were no differences in the content or affinity of ACE between CsA-treated and control rats. 5. These results suggest that the mesenteric vascular RAS does not play a major role in CsA-induced hypertension in the rat.  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