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   704854篇
  免费   49964篇
  国内免费   1297篇
耳鼻咽喉   9184篇
儿科学   23351篇
妇产科学   17633篇
基础医学   110446篇
口腔科学   19979篇
临床医学   63733篇
内科学   134217篇
皮肤病学   16158篇
神经病学   49465篇
特种医学   25741篇
外国民族医学   76篇
外科学   104513篇
综合类   14824篇
现状与发展   2篇
一般理论   160篇
预防医学   51365篇
眼科学   16305篇
药学   53949篇
  3篇
中国医学   2356篇
肿瘤学   42655篇
  2019年   5446篇
  2018年   7868篇
  2017年   6111篇
  2016年   6826篇
  2015年   7560篇
  2014年   10277篇
  2013年   15393篇
  2012年   20525篇
  2011年   21524篇
  2010年   12744篇
  2009年   11958篇
  2008年   20026篇
  2007年   21566篇
  2006年   21928篇
  2005年   20461篇
  2004年   20015篇
  2003年   18964篇
  2002年   18467篇
  2001年   36336篇
  2000年   36915篇
  1999年   30393篇
  1998年   7883篇
  1997年   6666篇
  1996年   6973篇
  1995年   6633篇
  1994年   6103篇
  1993年   5595篇
  1992年   22973篇
  1991年   22936篇
  1990年   22317篇
  1989年   22082篇
  1988年   20042篇
  1987年   19423篇
  1986年   18475篇
  1985年   17314篇
  1984年   12699篇
  1983年   10743篇
  1982年   5923篇
  1979年   11520篇
  1978年   8129篇
  1977年   6838篇
  1976年   6600篇
  1975年   7274篇
  1974年   8499篇
  1973年   8143篇
  1972年   7660篇
  1971年   7130篇
  1970年   6879篇
  1969年   6307篇
  1968年   5781篇
排序方式: 共有10000条查询结果,搜索用时 771 毫秒
961.
A structured discourse strategy, employing child echoic imitations and adult expansion, was used to teach 5 autistic children two-term semantic relations. The 5 male preschoolers in late Stage I of linguistic development were exposed systematically to two-term semantic relations in a structured dialogue with a clinician. A combined multiple baseline and AB(A) design was used to examine the relationship between the clinician expansions and the children's subsequent spontaneous imitations and spontaneous productions. The results showed that an increase in modeling and expansion was related to an increase in the children's initial spontaneous imitations of two-term relations. Further, following the increase in spontaneous imitations, spontaneous productions of the two-term relations increased and were maintained, whereas spontaneous imitations subsequently decreased.  相似文献   
962.
963.
Sixty children aged 5-13 years with moderately severe asthma took part in a double-blind, placebo-controlled trial of ketotifen. The design incorporated a 22 week study period, the addition of ketotifen or placebo to the current medication, and a controlled withdrawal of the regular therapy. Children receiving ketotifen showed significantly lower mean numbers of asthma attacks and less absence from school. The addition of ketotifen to existing treatment was associated with marginally significant changes in rates of day and night wheezing. In the second phase of study, additional therapy was withdrawn from both the ketotifen and placebo groups which resulted in a high (percentage) withdrawal. Children receiving ketotifen did not have a significantly lower failure rate than those given placebo.  相似文献   
964.
Nasal Cytogram is a simple, economical and reliable investigation. Although its utility was recognised as early s1927, it has not gained much popularity. Here an attempt is madeto assess the efficacy of nasal cytology in the light of histology, to diagnose various nasal conditions.127 cases of common rhinological problem were studied at Govt. Medical College, Nagpur. This investigation was found to be simple, reliable & economical.  相似文献   
965.
966.
967.
Idiopathic retroperitoneal fibrosis. A retrospective analysis of 60 cases   总被引:5,自引:0,他引:5  
Sixty patients with idiopathic retroperitoneal fibrosis presenting between 1965 and 1984 are reviewed. Their mean age at presentation was 56 years and the male:female ratio was 3:1. The commonest presenting symptoms were flank and abdominal pain, weight loss, nausea and polyuria. Physical examination was usually normal, expect for the presence of hypertension. Anaemia and elevation of erythrocyte sedimentation rate were usually present. Proteinuria was found in less than a third of patients at presentation and significant bacteriuria was uncommon. The correct diagnosis was made or suspected in very few patients before referral. The cumulative actuarial survival rate was 86% at 1 year and 78% at 2 years. Seventeen patients died; they were significantly older and more uraemic at the time of referral than those who survived. A few patients did well with either corticosteroid therapy or ureterolysis alone. In the majority, both operation and steroid treatment were necessary. In bilateral obstruction with residual function in both kidneys, bilateral ureterolysis proved superior to unilateral operation (each followed by steroid therapy) in conserving renal function. Operation alone or steroid therapy alone should be considered in cases where steroids or surgery respectively present particular hazards. The less traumatic unilateral operation should be considered in poor risk patients and in those whose renal function is absent on one side. In many survivors, disease activity has persisted for many years. Life-long follow-up is recommended.  相似文献   
968.
Interactions of cholecystokinin and glucose in rat pancreatic islets   总被引:1,自引:0,他引:1  
The effects of sulfated cholecystokinin (CCK-8S) and glucose on insulin secretion and polyphosphoinositide (PPI) metabolism were studied in isolated rat islets. Both agonists stimulate PPI hydrolysis, inositol phosphate accumulation, 3H efflux from [3H]inositol-prelabeled tissue, and 45Ca efflux from prelabeled cells. However, the effects of CCK-8S on PPI metabolism are considerably greater than those of glucose. Furthermore, the effects of CCK-8S on PPI and Ca2+ metabolism are observed whether islets are incubated in either 2.75 or 7 mM glucose, but CCK-8S only stimulates insulin secretion (a biphasic response) when the higher glucose concentration is present. Addition of 1 microM forskolin to islets incubated in media containing 2.75 mM glucose does not influence basal insulin secretion but sensitizes the islets to the action of CCK-8S. In the presence of forskolin, CCK-8S induces a very marked first phase but no second phase of insulin secretion. We postulate that CCK-8S acts in this tissue via receptor-linked PPI hydrolysis, leading to an inositol trisphosphate-induced Ca2+ efflux. These receptor-mediated effects of CCK-8S are not altered either by the ambient glucose concentration or the cAMP content of the islets, but these two factors determine the responsiveness of the islets (in terms of insulin secretion) to a given CCK-8S signal.  相似文献   
969.
970.
Electrophysiologic effects of d-sotalol in humans   总被引:1,自引:0,他引:1  
Sotalol is a beta-adrenergic blocking agent that prolongs the duration of the cardiac action potential in humans, without affecting the upstroke velocity of depolarization. The dextrorotatory isomer, d-sotalol, retains these class III effects, but has little beta-blocking activity in vitro. d-Sotalol has not been studied extensively in humans. The electrocardiographic (ECG) and electrophysiologic effects of d- and d,l-sotalol were therefore assessed in a prospective randomized study of 20 patients. Each patient received either d-sotalol (1, 1.5 or 2 mg/kg body weight) or d,l-sotalol (1 mg/kg) by intravenous infusion. The QT and QTc intervals were prolonged and refractoriness increased in the atrium, atrioventricular (AV) node, His-Purkinje system and right ventricle after both d- and d,l-sotalol. After d-sotalol, the increases in both QT and QTc intervals and in atrial and ventricular effective refractory periods were dose dependent. Highly significant linear correlation was demonstrated between the plasma sotalol level and the change in QT (r = 0.86, p = 0.001) and QTc intervals (r = 0.79, p = 0.002), and between the plasma sotalol level and the effective refractory period of the right atrium (r = 0.75, p = 0.005) and ventricle (r = 0.70, p = 0.025). This study confirms that d-sotalol has effects consistent with class III properties. It demonstrates these effects in humans, and suggests that d-sotalol may prove to be a useful antiarrhythmic agent.  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