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   19367篇
  免费   1802篇
  国内免费   46篇
耳鼻咽喉   152篇
儿科学   574篇
妇产科学   427篇
基础医学   2795篇
口腔科学   411篇
临床医学   2290篇
内科学   4082篇
皮肤病学   474篇
神经病学   1457篇
特种医学   616篇
外科学   3147篇
综合类   535篇
一般理论   10篇
预防医学   1649篇
眼科学   261篇
药学   1313篇
  1篇
中国医学   83篇
肿瘤学   938篇
  2021年   234篇
  2020年   177篇
  2019年   259篇
  2018年   255篇
  2017年   251篇
  2016年   264篇
  2015年   300篇
  2014年   419篇
  2013年   576篇
  2012年   911篇
  2011年   854篇
  2010年   483篇
  2009年   485篇
  2008年   781篇
  2007年   834篇
  2006年   827篇
  2005年   813篇
  2004年   758篇
  2003年   724篇
  2002年   669篇
  2001年   578篇
  2000年   672篇
  1999年   547篇
  1998年   271篇
  1997年   259篇
  1996年   242篇
  1995年   204篇
  1994年   212篇
  1993年   201篇
  1992年   500篇
  1991年   476篇
  1990年   416篇
  1989年   425篇
  1988年   416篇
  1987年   395篇
  1986年   381篇
  1985年   340篇
  1984年   334篇
  1983年   239篇
  1982年   154篇
  1981年   165篇
  1980年   147篇
  1979年   265篇
  1978年   166篇
  1977年   135篇
  1976年   142篇
  1974年   169篇
  1973年   165篇
  1972年   158篇
  1971年   125篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
‘Wandering’ is one of the most troublesome of behavioural problems in dementia. The term ‘wandering’ covers many different types of behaviour. We examined the hypothesis that the different types of wandering behaviour seen in dementia from a scale using data collected on 83 elderly subjects suffering from either Alzheimer's disease or multiinfarct dementia. We reject the scaling hypothesis. Our data suggest that there are three main categories of wandering behaviour, and that one of these categories is usefully divided into four subcategories.  相似文献   
62.
Two experiments were conducted in which the acute effects of inhaled methanol on serum hormones associated with reproductive function in the male rat were evaluated. In the first experiment, rats exposed to methanol (0, 200, 5000 and 10,000 ppm) for 6 h were killed at the end of the exposure period (6 h) or the following morning (24 h). Also, because the process of exposure itself could modify neuroendocrine function, the effect of the handling associated with placing the rat in the exposure chamber was evaluated further by dividing the exposed animals into acclimated (2 weeks of prior handling) and non-acclimated groups. At 6 h, an effect of prior handling was noted in the sham-exposed rats, with serum luteinizing hormone (LH) of the non-acclimated group being greater than that of the acclimated group. Serum LH concentrations were altered by methanol exposure, but the direction of change and the exposure level at which an effect was noted differed between the acclimated and non-acclimated rats. Methanol (5000 ppm) reduced serum LH in the non-acclimated animals, while 10,000 ppm increased LH in the acclimated rats. Follicle stimulating hormone (FSH) and testosterone were unchanged by methanol in rats killed at 6 h. Thus, this experiment did not confirm earlier reports that exposure to 200 ppm for 6 h reduced serum testosterone. At 24 h, an effect of prior handling was still present in the hormonal measures, with serum and interstitial fluid testosterone concentrations being greater in the non-acclimated rats. Also, there was a dose x handling interaction with methanol exposure inducing an increase in serum testosterone in the non-acclimated rats (up to 5000 ppm) and a decrease in the acclimated rats (up to 10,000 ppm). In the second experiment, groups of acclimated and non-acclimated rats were exposed to 0 or 5000 ppm methanol for 1, 2 and 6 h and killed immediately after removal from the chamber. Serum LH, testosterone and FSH values were not different in sham- vs methanol-exposed rats at any time point. As in experiment 1, an effect of prior handling was noted. In general, the concentrations of these hormones and serum prolactin in the non-acclimated rats were greater than those observed for acclimated rats. Methanol exposure resulted in increased prolactin concentrations under both handling conditions.(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   
63.
States of phosphorylation of neurofilament proteins were examined in the perikarya of rat sensory and motor neurons between 3 and 28 d following either a distal transection [6-7 cm from the L4-L5 dorsal root ganglia (DRG)] or a proximal transection (1-2 cm from the L4-L5 DRG) of the sciatic nerve. Paraffin sections of the right (experimental) and left (control) L4 and L5 DRG from animals with unilateral transection of the right distal sciatic nerve were stained immunocytochemically with monoclonal antibodies to phosphorylation-dependent (NF-P), dephosphorylation-dependent (NF-dP), or phosphorylation-independent (NF-ind) epitopes on the largest (NF200), mid-sized (NF150), or smallest (NF68) neurofilament protein subunits. Increased immunoreactivity to NF-P on NF200 and NF150 was detected in experimental DRC at 10 d, peaking by 20 d, and declining to near control levels by 28 d. Conversely, immunoreactivity to NF-dP declined in experimental DRG beginning at 6 d, reaching a maximum decline at 10-16 d, and returning to near control levels by 28 d. Immunocytochemical changes were confirmed with biochemical studies on tissue homogenates that demonstrated an increase of immunoreactivity to NF-P and a decrease of reactivity to NF-dP in the experimental DRG. Changes in immunoreactivities to NF-P and NF-dP were observed only in the perikarya of large neurons and were closely associated with chromatolytic changes in these neurons. Marked enhancement of chromatolysis, as well as the immunoreactivities to NF-P and NF-dP, occurred following a proximal (left side) versus distal (right side) transection in the same animal.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
64.
We studied physical fitness and risk of all-cause and cause-specific mortality in 10,224 men and 3120 women who were given a preventive medical examination. Physical fitness was measured by a maximal treadmill exercise test. Average follow-up was slightly more than 8 years, for a total of 110,482 person-years of observation. There were 240 deaths in men and 43 deaths in women. Age-adjusted all-cause mortality rates declined across physical fitness quintiles from 64.0 per 10,000 person-years in the least-fit men to 18.6 per 10,000 person-years in the most-fit men (slope, -4.5). Corresponding values for women were 39.5 per 10,000 person-years to 8.5 per 10,000 person-years (slope, -5.5). These trends remained after statistical adjustment for age, smoking habit, cholesterol level, systolic blood pressure, fasting blood glucose level, parental history of coronary heart disease, and follow-up interval. Lower mortality rates in higher fitness categories also were seen for cardiovascular disease and cancer of combined sites. Attributable risk estimates for all-cause mortality indicated that low physical fitness was an important risk factor in both men and women. Higher levels of physical fitness appear to delay all-cause mortality primarily due to lowered rates of cardiovascular disease and cancer.  相似文献   
65.
Barrett's oesophagus: a clinical study of 52 patients   总被引:4,自引:0,他引:4  
This paper reports a series of 52 patients with Barrett's (or columnar-lined) oesophagus from one medical unit diagnosed over a six-year period. The commonest associated symptoms were heartburn, regurgitation and dysphagia but 10 patients had no oesophageal symptoms and two had no symptoms at all. Gastrointestinal bleeding (overt or occult) was observed in almost one-third of patients. At diagnosis, 26 patients had oesophagitis, 23 had oesophageal ulceration and 10 had benign oesophageal strictures. An association between oesophageal ulceration and non-steroidal anti-inflammatory drug ingestion was suggested by the data and patients with oesophageal ulceration were significantly older than patients with uncomplicated Barrett's oesophagus. No patient had adenocarcinoma of the oesophagus at diagnosis and neither carcinoma nor dysplasia were seen during a mean period of 16.4 months. However, 17 per cent of patients in the series had malignancies in other sites. Most patients did well on medical treatment and only two were referred for anti-reflux surgery (both for non-healing oesophageal ulcers). Barrett's oesophagus was seen in 10 per cent of patients with gastro-oesophageal reflux at endoscopy. Oesophageal ulceration in patients with Barrett's oesophagus made up 21 per cent of oesophageal ulcers seen and benign oesophageal stricture in patients with Barrett's oesophagus constituted 13 per cent of all benign strictures seen. Barrett's oesophagus is common in our population and despite complications, it can be managed successfully, at least in the short term, by conservative means.  相似文献   
66.
Sharing techniques using the upper eyelid to reconstruct the lower one have been criticised for causing distortion of the normal upper lid leading to corneal exposure and possible visual disturbance, and for creating second-rate lids. A modification of previously described tarsoconjunctival flap techniques is described which minimises the known complications of earlier methods. A flap of conjunctiva alone is mobilised from the upper eyelid and covered with a full thickness skin graft. A second minor procedure to divide the flap from its donor site is necessary 2 weeks later. Forty-three patients over a 25-year period have undergone total lower eyelid reconstruction with this modified technique and are reviewed with some illustrative cases. Total or subtotal lower eyelid reconstruction is most commonly performed following tumour resection and only occasionally to correct congenital or traumatic defects. The surgical techniques available still cause controversy (Byrd, 1983). An upper lid sharing technique has been criticised for possibly causing a shortened or distorted normal lid (Mustardé, 1981). A modification of this method is described which has been used for over 25 years and has reduced the morbidity of the procedure, leading to acceptable cosmetic and functional long-term results.  相似文献   
67.
The suction trephine was studied in 31 aphakic and pseudophakic penetrating keratoplasty patients (31 eyes). The postoperative corneal astigmatism averaged 3.9 +/- 2.8 diopters overall. The 15 pseudophakic cases in nonscarred corneas showed a marked reduction in postoperative corneal astigmatism (3.59 diopters) when compared to previous reports. Our results have encouraged us to continue use of the suction trephine in all aphakic or combined keratoplasty procedures.  相似文献   
68.
BACKGROUND: Recent case reports, small series, and uncontrolled, unblinded studies have suggested that tranylcypromine may produce pressor reactions in some patients. However, the physiologic mechanism underlying this cardiovascular change is unknown. METHOD: The authors studied the acute cardiovascular effects of tranylcypromine in 13 patients and attempted to correlate these changes with plasma measures of parent drug, possible pressor metabolites, norepinephrine, and 3-methoxy-4-hydroxyphenylglycol. RESULTS: Significant elevations in supine blood pressure occurred after administration of tranylcypromine and correlated with tranylcypromine dose. Similar changes were not observed in standing blood pressure measurements. In fact, an orthostatic decrease in blood pressure and increase in heart rate were observed. Amphetamine-like metabolites were not found. CONCLUSIONS: The authors speculate on possible mechanisms underlying these opposite cardiovascular effects.  相似文献   
69.
Single lung transplantation (SLT) has been considered physiologically inappropriate for patients with chronic obstructive pulmonary disease (COPD). It has been postulated that the high static compliance and elevated pulmonary vascular resistance of the native lung functioning in parallel with the more normal allografted lung could cause unacceptable ventilation-perfusion mismatching and/or overinflation of the native lung with encroachment on the expansion of the transplanted lung. While some degree of ventilation-perfusion imbalance may be physiologically obligatory after SLT for COPD, a significant disruption in gas exchange may not occur unless a complication, such as rejection or infection, arises in the transplanted lung. A 60-year-old man with COPD who underwent successful SLT is presented and discussed. In spite of scintigraphic evidence of ventilation-perfusion mismatching between the native lung and the allograft during the first six postoperative weeks, the recipient had normal resting gas exchange on room air after the second postoperative week. Fourteen weeks after transplantation, his maximum oxygen uptake was 37.3 percent of the predicted maximal value, and no evidence of ventilatory limitation was detected. His functional status and lifestyle have been markedly improved by SLT. The role of SLT for COPD should be reconsidered. It may be a reasonable transplantation alternative for selected patients with COPD who are not candidates for double lung transplantation (DLT).  相似文献   
70.
Herpes simplex encephalitis may be underdiagnosed in Britain. We report eight patients treated at one hospital over three years. Fever, impaired consciousness or focal neurological signs were seen in all patients at presentation but herpes simplex encephalitis was rarely considered as the initial diagnosis. The electroencephalogram was the only initial investigation that was abnormal in each case and was the most useful test in establishing a clinical diagnosis. The diagnosis was confirmed by laboratory methods in each case. Following acyclovir treatment five patients were able to resume normal activities, one patient has moderate disability and two patients died. Three patients showed clinical evidence of relapse but two improved after further treatment with acyclovir. Herpes simplex encephalitis is a treatable condition and should be considered in all patients presenting with fever and neurological signs. The electroencephalogram is usually abnormal and the changes may be characteristic of the condition.  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