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   1674913篇
  免费   128165篇
  国内免费   2979篇
耳鼻咽喉   24419篇
儿科学   46071篇
妇产科学   45268篇
基础医学   240465篇
口腔科学   50865篇
临床医学   146335篇
内科学   322954篇
皮肤病学   34231篇
神经病学   132193篇
特种医学   66578篇
外国民族医学   246篇
外科学   268374篇
综合类   39787篇
现状与发展   3篇
一般理论   475篇
预防医学   121617篇
眼科学   39495篇
药学   128497篇
  3篇
中国医学   3444篇
肿瘤学   94737篇
  2018年   15217篇
  2016年   13254篇
  2015年   15371篇
  2014年   21491篇
  2013年   32094篇
  2012年   43698篇
  2011年   45711篇
  2010年   26927篇
  2009年   25521篇
  2008年   44004篇
  2007年   47009篇
  2006年   47666篇
  2005年   46217篇
  2004年   45092篇
  2003年   43433篇
  2002年   42233篇
  2001年   82916篇
  2000年   85382篇
  1999年   71654篇
  1998年   18695篇
  1997年   16764篇
  1996年   16766篇
  1995年   15755篇
  1994年   14799篇
  1993年   13741篇
  1992年   57346篇
  1991年   55455篇
  1990年   54091篇
  1989年   52653篇
  1988年   48666篇
  1987年   47604篇
  1986年   44712篇
  1985年   43114篇
  1984年   32023篇
  1983年   27291篇
  1982年   15673篇
  1981年   14063篇
  1979年   30564篇
  1978年   21281篇
  1977年   18111篇
  1976年   16189篇
  1975年   17734篇
  1974年   21827篇
  1973年   20790篇
  1972年   19747篇
  1971年   18541篇
  1970年   17676篇
  1969年   17029篇
  1968年   15330篇
  1967年   14043篇
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
971.
1. Rhesus monkeys were equipped with a novel intracerebroventricular (i.c.v.) cannula system and trained to respond under operant schedules of food presentation or termination of stimuli associated with the delivery of shock (escape). 2. CRH decreased food-maintained behavior in a dose-related manner over the range of (0.3-10 micrograms/kg) but did not affect escape responding, demonstrating a selective effect on food-maintained responding. 3. This selective effect was related to the tendency for responding to stop after delivery of a food pellet when higher doses of CRH were given, consistent with the notion that a conditioned aversion to food was established in the presence of CRH. 4. This may suggest that in hyperaroused clinical states such as depression and anorexia nervosa, focus is shifted away from appetitive tasks as a result of increased levels of CRH.  相似文献   
972.
A girl of 14 year is presented with a distal spinal muscular atrophy (SMA) with autosomal recessive inheritance. The technical findings are in agreement with the diagnosis. Light microscopical examination of sural nerve biopsy, including teased fiber studies and morphometry, showed no abnormalities. Electron microscopical investigation however demonstrated axonal pathology. The question arises if distal SMA is a distal axonopathy mainly of motor nerves, but to some extent also of sensory nerves.  相似文献   
973.
Summary The prevalence of smoking, hypertension and diabetes mellitus was assessed in 221 patients suffering from internal carotid stenosis and compared with the prevalences in two sex- and age-matched control groups composed of subjects having normal Doppler findings and from non-neurological outpatients. Of the subjects with carotid stenosis 27.6% were hypertensive smokers in comparison with 9.5% and 17.2% in the two control groups. The difference of the stenosis cohort from the two control groups was significant (P<0.01 and P=0.016 respectively). There was no statistically significant differences between the occurrence of diabetes and hypertension in non-smokers and patients who smoked. In 394 investigated patients suffering from carotid stenosis or occlusion an obstruction index, based on the Doppler shift frequency, was calculated. This index was lowest in the normotentive non-smokers. It was only insignificantly higher in the hypertensive non-smokers but significantly so in the normotensive smokers. The index was highest in the hypertensive non-smokers. It was concluded that cigarette smoking, especially if associated with hypertension, is a determinant risk factor for carotid stenosis and occlusion.  相似文献   
974.
The Flinders Sensitive Line (FSL) of rats has been selectively bred to have increased sensitivity to cholinergic agonists. However, these rats exhibit altered responsiveness to a number of noncholinergic agents, such as apomorphine, buspirone and ethanol. This study compared the FSL and control Flinders Resistant Line (FRL) rats in terms of their hyperthermic response to the phencyclidine (PCP) receptor agonist, MK-801 (0.2 mg/kg SC) and their MK-801 binding characteristics. We have found that FSL rats react with a delayed hyperthermia, having a significantly lower hyperthermia for the first 120 min of observation. Thereafter the response does not differ in FSL and FRL rats. Both groups had similar affinities and numbers of [3H]MK-801 binding sites in the hippocampus/cerebral cortex. Pretreatment with scopolamine (1 mg/kg SC) failed to affect MK-801-induced hyperthermia in either line of rats. These findings suggest that selective breeding of FSL rats attenuated the secondary mechanisms involved in the PCP receptor-mediated hyperthermic response. However, by itself cholinergic supersensitivity does not appear to be a major factor in the blunted responsiveness of FSL rats to MK-801.  相似文献   
975.
976.
32nd Annual Meeting of the Scandinavian Society for Psychopharmacology Copenhagen, Denmark April 10–12, 1991 Abstracts  相似文献   
977.
Synaptic contacts between growth hormone-releasing hormone (GHRH)- and somatostatin-containing neurons were demonstrated in the rat hypothalamus by a double-staining immunocytochemical method at the electron microscopic level. Somatostatin-immunoreactive nerve terminals synapse on GHRH-positive dendrites and cell bodies in the arcuate nucleus. A fine network of GHRH-immunopositive nerve terminals was observed at the light microscopic level in the rostral part of the periventricular nucleus and in the dorsal part of the arcuate nucleus around somatostatin-containing neuronal elements. With the electron microscope synaptic contact between GHRH-containing nerve terminals and somatostatin-containing dendrites are demonstrated. The reciprocal innervation between GHRH- and somatostatin-containing neurons that project to the median eminence and regulate growth hormone secretion must allow them to coordinate their activities.  相似文献   
978.
The hyperventilation syndrome is present in as many as 50% of patients with non-cardiac chest pain. This study evaluated a behavioral treatment of this disorder in three adult females. They had long histories of chest pain and were documented to be free of coronary artery disease. Each subject met the DSM-III-R diagnostic criteria for an anxiety disorder. Following treatment, all subjects showed a marked decrease in the frequency and intensity of chest pain episodes and in the frequency of shortness of breath episodes. Two subjects maintained their progress at one-year follow-up. The results lend support to the efficacy of controlled breathing and relaxation training for the treatment of hyperventilation-related chest pain and to the inclusion of a hyperventilation provocation test in the diagnosis of the syndrome as well as its role in changing cognitions regarding cardiac status. Also discussed is the rationale for treating hyperventilation related chest pain in a medical care setting.  相似文献   
979.
Sixty chronic alcoholic patients, aged 35.6 +/- 0.7 years and an average alcoholic history of 9.3 +/- 0.5 years were examined. Atrial fibrillation was detected at 24 h ECG monitoring in 2 (3.45%) patients, and paroxysms of atrial fibrillation or flutter were detected by intracardiac electrophysiologic investigation in 6 (22.2%). Fourteen (44.8%) patients with alcoholic heart damage demonstrated atrial vulnerability, indicative of a predisposition to atrial fibrillation even at earlier stages of alcoholic heart damage.  相似文献   
980.
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