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   2384022篇
  免费   173198篇
  国内免费   3502篇
耳鼻咽喉   32333篇
儿科学   76562篇
妇产科学   63257篇
基础医学   352486篇
口腔科学   64479篇
临床医学   213615篇
内科学   465677篇
皮肤病学   52227篇
神经病学   187775篇
特种医学   89214篇
外国民族医学   489篇
外科学   360233篇
综合类   47665篇
现状与发展   12篇
一般理论   848篇
预防医学   183840篇
眼科学   54730篇
药学   177546篇
  11篇
中国医学   4701篇
肿瘤学   133022篇
  2021年   19639篇
  2019年   20049篇
  2018年   27688篇
  2017年   20861篇
  2016年   23318篇
  2015年   26283篇
  2014年   36926篇
  2013年   54931篇
  2012年   76228篇
  2011年   81052篇
  2010年   47984篇
  2009年   45308篇
  2008年   76051篇
  2007年   81025篇
  2006年   81829篇
  2005年   79364篇
  2004年   75991篇
  2003年   73233篇
  2002年   70920篇
  2001年   109983篇
  2000年   112637篇
  1999年   94669篇
  1998年   27482篇
  1997年   24054篇
  1996年   24399篇
  1995年   23024篇
  1994年   21187篇
  1993年   19973篇
  1992年   72766篇
  1991年   70805篇
  1990年   69017篇
  1989年   66333篇
  1988年   60906篇
  1987年   59678篇
  1986年   55807篇
  1985年   53520篇
  1984年   39666篇
  1983年   33680篇
  1982年   20027篇
  1979年   36111篇
  1978年   25852篇
  1977年   21402篇
  1976年   20458篇
  1975年   21987篇
  1974年   26309篇
  1973年   24954篇
  1972年   23332篇
  1971年   22188篇
  1970年   20383篇
  1969年   19460篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Ureteroscopic pyelolysis for pelviureteric junction obstruction   总被引:8,自引:0,他引:8  
The development of endourological techniques for the treatment of upper urinary tract disease has concentrated mainly on the endoscopic treatment of upper urinary tract stones. The relief of pelviureteric junction obstruction (PUJ) by percutaneous pyelolysis has recently been reported and the use of the flexible uretero-pyeloscope has also been described. We describe the use of a rigid uretero-renoscopy to relieve strictures causing secondary pelviureteric junction obstruction in two cases.  相似文献   
992.
Assessment of completeness of vagotomy has always been an irksome and time-consuming affair. The commonly employed test of insulin-induced hypoglycaemia (Hollander) is tedious, risky and associated with practical limitations and theoretical objections, which have resulted in its being replaced by the modified sham feed technique in some centres. The postprandial alkaline tide is attributed to HCO3- release consequent to H+ secretion. Any procedure which reduces acid secretion is expected to affect the postprandial urinary pH. This study was performed to evaluate the effect of vagotomy on the postprandial alkaline tide by measuring prevagotomy and postvagotomy fasting and postprandial urinary pH. The results show that postprandial urinary pH falls after vagotomy and this method may be used to assess the completeness of vagotomy. The proposed test is convenient and may be used as a screening method in the assessment of vagotomy and other acid reducing operative procedures, if further validated, by comparison with already established tests.  相似文献   
993.
Pure motor hemiplegia (PMH) is, in most cases, caused by a lacunar infarction. However, pure motor monoparesis (PMM), i.e., isolated motor involvement with spasticity in one limb, has drawn little attention. We studied prospectively 5 patients with PMM and found that it was always due to a mass lesion in the contralateral superficial cerebral hemisphere. Our observation suggests that PMM should not be regarded as simply a variant of PMH.  相似文献   
994.
The purpose of the study was to compare an interview measure of quality of object relations to questionnaire and interview measures of recent interpersonal functioning with respect to the prediction of therapeutic alliance and psychotherapy outcome. The sample consisted of 64 patients who had received approximately 20 sessions of short-term individual psychotherapy within a controlled, clinical-trial investigation. Ratings of therapeutic alliance were provided independently by the patient and the therapist after each session. Outcome measures, which were provided by three sources (patient, therapist, and independent assessor), covered the areas of interpersonal functioning, psychiatric symptomatology, self-esteem, and life satisfaction. Quality of object relations, which characterizes the patient's lifelong pattern of relationships, was the best predictor. It was significantly related to patient-rated and therapist-rated therapeutic alliance and to patient improvement of both general symptomatology and specific target problems. The study also replicated previous studies that have reported significant relationships between therapeutic alliance and therapy outcome. The advantages of pretherapy predictors of therapy outcome, such as quality of object relations, are discussed.  相似文献   
995.
996.
Reports of plasma concentrations of antidepressants and their metabolites in patients with reduced renal function have been reviewed. The consequences of alteration of various pharmacokinetic factors on drug and metabolite concentrations have been compared with the observed data. Concentrations of drugs that are more than 95 percent metabolized are not altered by decreased renal function. Concentrations of drugs that are mostly excreted unchanged in urine are greatly increased in patients with reduced renal function. Concentrations of metabolites that account for 10 percent or more of the dose of a parent drug in urine are usually increased. In general, the observations can be explained without hypothesizing an effect of reduced renal function on clearance by metabolism.  相似文献   
997.
Regulatory control of indoor Rn   总被引:2,自引:0,他引:2  
Regulation of indoor Rn is explored in the context of cost-effectiveness of regulatory action. Evaluation of cost (i.e., mitigation expenses) and benefits (i.e., savings associated with medical expenses and lost productivity related to lung cancer) at various action levels indicate that regulatory programs would be economically inefficient and unreasonable if standards were established at or below the current EPA action guide (150 Bq m-3 or less). For the approximately 95% of U.S. homes with Rn levels near or below 150 Bq m-3, government programs should continue to focus on public information and consumer protection. For the small number of homes with high Rn levels, government programs should focus on identifying high risk homes and encouraging homeowners to reduce Rn levels. Because of the potential for substantial risk reduction, such efforts would be cost-effective in these homes.  相似文献   
998.
Multiple-compartment models employed in the analysis of trace element transport in animals are often based on linear differential equations which relate the rate of change of contaminant (or contaminant concentration) in each compartment to the amount of contaminant (or contaminant concentration) in every other compartment in the system. This has the serious disadvantage of mixing intrinsic physiological properties with the geometry of the animal. The basic equations on which the model presented here is developed are derived from the actual physical process under way and are capable of separating intrinsic physiological properties from geometry. It is thus expected that rate coefficients determined through this model will be applicable to a wider category of physiologically similar animals. A specific application of the model for the study of contamination of sheep--or indeed for any ruminant--is presented, and the temporal evolution of contaminant concentration in the various compartments of the animal is calculated. The application of this model to a system of compartments with changing geometry is also presented.  相似文献   
999.
1000.
For monitoring the changes in intracellular free Ca2+ concentration ([Ca2+]i), we developed a simple system combining a fluorescence microscope, an image intensifier, a video-camera, a cathode ray tube display and a photodiode, employing quin2 as a Ca2+ indicator. We recorded increases of the fluorescence intensity due to [Ca2+]i rises, when high K+ medium, neurotransmitter and Ca2+ ionophore were applied to the single cells of nervous system origin in culture. The present system is capable of simultaneous detection of the [Ca2+]i changes from multiple separate cells.  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