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   14029篇
  免费   1948篇
  国内免费   593篇
耳鼻咽喉   138篇
儿科学   190篇
妇产科学   51篇
基础医学   1090篇
口腔科学   319篇
临床医学   1801篇
内科学   2548篇
皮肤病学   34篇
神经病学   4005篇
特种医学   720篇
外科学   1085篇
综合类   1489篇
预防医学   863篇
眼科学   150篇
药学   836篇
  14篇
中国医学   974篇
肿瘤学   263篇
  2024年   60篇
  2023年   343篇
  2022年   564篇
  2021年   925篇
  2020年   818篇
  2019年   750篇
  2018年   630篇
  2017年   728篇
  2016年   737篇
  2015年   673篇
  2014年   1025篇
  2013年   1272篇
  2012年   837篇
  2011年   891篇
  2010年   698篇
  2009年   643篇
  2008年   567篇
  2007年   612篇
  2006年   554篇
  2005年   436篇
  2004年   419篇
  2003年   383篇
  2002年   347篇
  2001年   272篇
  2000年   177篇
  1999年   137篇
  1998年   189篇
  1997年   146篇
  1996年   128篇
  1995年   93篇
  1994年   94篇
  1993年   47篇
  1992年   54篇
  1991年   40篇
  1990年   30篇
  1989年   32篇
  1988年   29篇
  1987年   22篇
  1986年   31篇
  1985年   22篇
  1984年   15篇
  1983年   19篇
  1982年   16篇
  1981年   13篇
  1980年   13篇
  1979年   9篇
  1978年   8篇
  1977年   7篇
  1976年   4篇
  1974年   4篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
BACKGROUND AND AIMS: Functional gastrointestinal disorders are diagnosed by the presence of a characteristic set of symptoms. Aims of this study were to validate the Rome symptom criteria by factor analysis and to determine whether symptoms cluster in the same way in different cultures. METHODS: One thousand forty-one gastroenterology clinic patients in the US (response rate 53%) and 228 family members accompanying clinic patients in Italy (84%) completed a previously validated symptom questionnaire. Factor analysis identified clusters of symptoms which are highly correlated with each other, and these were compared to the Rome diagnostic criteria. RESULTS: In the US, 13 factors were identified. The irritable bowel factor was composed of three core symptoms corresponding to the Rome II classification system. Two dyspepsia factors were identified which correspond to the ulcer- and motility-like subtypes proposed in the Rome I classification system. All symptoms of constipation formed a single cluster as proposed in the Rome II classification system. Symptom clusters in the US agreed well with symptom clusters identified in Italian subjects. CONCLUSIONS: Empirically derived symptom clusters agree in most respects with the Rome II classification system and support their validity. These symptom clusters are independent of cultural differences in diet and behaviour.  相似文献   
52.
替勃龙改善绝经期功能性消化不良症状   总被引:2,自引:0,他引:2  
目的 :探讨替勃龙能否改善绝经期功能性消化不良患者临床症状及其相关机制。方法 :14 3例绝经期功能性消化不良患者随机分成 3组 ,分别给予替勃龙、西沙必利及替勃龙 +西沙必利 ,治疗 4周 ,观察治疗前后各组患者上腹胀痛、餐后胀满、早饱、暖气等临床症状积分的变化。在随机分成的 3组中再随机各抽出 2 0例患者治疗前后测定胃 30min排空率及胃半排空时间 ,观察治疗前后胃动力的变化。结果 :3组药物治疗后 2周和 4周上腹胀痛、餐后胀满症状积分均明显下降。西沙必利治疗后 2周和 4周对早饱、暖气症状无明显缓解 ,替勃龙及替勃龙 +西沙必利则对所观察的所有症状均有明显缓解 ,替勃龙改善早饱和嗳气症状优于西沙必利 ,但与西沙必利合用无增强效应。 3种药物治疗后 ,胃 30min排空率均明显增加、胃半排空时间缩短 ,与治疗前比较有显著差异 (P <0 .0 5 ) ,但 3种治疗方案之间无显著性差异 (P >0 .0 5 )。结论 :替勃龙能通过增强胃动力 ,明显改善部分绝经期功能性消化不良患者的临床症状 ,疗效优于促动力药。  相似文献   
53.
Perfusion is a crucial physiological parameter for tissue function. To obtain perfusion-weighted images and consequently to measure cerebral blood flow (CBF), a newly developed flow-sensitive alternating inversion recovery (FAIR) technique was used. Dependency of FAIR signal on inversion times (TI) was examined; signal is predominantly located in large vessels at short TI, whereas it is diffused into gray matter areas at longer TI. CBF of gray matter areas in the human brain is 71 ± 15 SD ml/100 g/min (n = 6). In fMRI studies, micro- and macrovessel inflow contributions can be obtained by adjusting TIs. Signal changes in large vessel areas including the scalp were seen during finger opposition at a TI of 0.4 s; however, these were not observed at a longer TI of 1.4 s. To compare with commonly used BOLD and slice selective inversion recovery techniques, FAIR and BOLD images were acquired at the same time during unilateral finger opposition. Generally, activation sites determined by three techniques are consistent. However, activation of some areas can be detected only by FAIR, not by BOLD, suggesting that the oxygen consumption increase couples with the CBF change completely. Relative and absolute CBF changes in the contralateral motor cortex are 53 ± 17% SD (n = 9) and 27 ± 11 SD ml/100 g/min (n = 9), respectively.  相似文献   
54.
BACKGROUND: It has been established that individuals who score high on measures of psychopathy demonstrate difficulty when performing tasks requiring the interpretation of other's emotional states. The aim of this study was to elucidate the relation of emotion and cognition to individual differences on a standard psychopathy personality inventory (PPI) among a nonpsychiatric population. METHODS: Twenty participants completed the PPI. Following survey completion, a mean split of their scores on the emotional-interpersonal factor was performed, and participants were placed into a high or low group. Functional magnetic resonance imaging data were collected while participants performed a recognition task that required attention be given to either the affect or identity of target stimuli. RESULTS: No significant behavioral differences were found. In response to the affect recognition task, significant differences between high- and low-scoring subjects were observed in several subregions of the frontal cortex, as well as the amygdala. No significant differences were found between the groups in response to the identity recognition condition. CONCLUSIONS: Results indicate that participants scoring high on the PPI, although not behaviorally distinct, demonstrate a significantly different pattern of neural activity (as measured by blood oxygen level-dependent contrast)in response to tasks that require affective processing. The results suggest a unique neural signature associated with personality differences in a nonpsychiatric population.  相似文献   
55.
Functional decline in frail community-dwelling stroke patients   总被引:1,自引:0,他引:1  
Patients who suffer a stroke event are at high risk of functional decline after the post-acute rehabilitation period. The aim of the present study was the evaluation of factors associated with functional decline in a large sample of older patients with stroke living in the community. The study population consisted of all patients admitted to home care programs after a post-acute rehabilitation program--with at least 1 year of follow-up--in twenty-two Italian Home Health Agencies from 2000 to 2002 (n=1338). For the present study we selected 355 (26%) patients with diagnosis of stroke. After 1 year of in-home care program, 149 out of 355 stroke survivors (42%) had presented a worsening in the activities of daily living (ADL) scale score. In the final adjusted model, patients with cognitive impairment (OR 2.59, 95% CI, 1.45-4.64), pressure ulcer (OR 2.74, 95% CI, 1.45-5.18), urinary incontinence (OR 1.64, 95% CI, 1.01-3.29), or hearing impairment (OR 1.83, 95% CI, 1.02-3.29) were more likely to significantly decline in physical functioning after a period of 1 year in-home care program. Our study documents that functional decline of stroke patients was largely dependent on specific subjects' clinical characteristics. Three of four concomitant disabling conditions associated in our sample with functional decline--pressure ulcer, urinary incontinence, hearing--can be prevented and eventually treated or modified. Appropriate post-acute rehabilitation programs and adequate home care interventions focused on the prevention and treatment of these conditions might be correlated to better outcomes in older post-stroke patients.  相似文献   
56.
This correlational and comparative study explored whether self-reports of self-efficacy and dyspnea perceptions predict the perceived level of functional performance in adults who have chronic obstructive pulmonary disease (COPD). The convenience sample included 97 Caucasian men (52) and women (45). Participants had to have a forced expiratory volume in 1 second (FEV1) of less than 70% predicted, and a FEV1/forced vital capacity (FVC) of less than 70%. Participants were recruited from pulmonary function laboratories and from better breather support groups in a Midwestern state. Three standardized, self-report instruments, COPD Self-Efficacy Scale (CSES), the Pulmonary Functional Status and Dyspnea Questionnaire (PFSDQ), and Functional Performance Inventory (FPI) were used to measure the participants' self-report of their perceptions of self-efficacy, dyspnea, and functional performance. Dyspnea predicted 38.1% of the variance in functional performance, with self-efficacy contributing an additional 6.5% to the variance in the total sample. Self-efficacy predicted 36.5% of the variance in functional performance in men, with dyspnea contributing an additional 7.2% to the variance. However, in women, only dyspnea was a significant predictor of functional performance, at 48.5% when both dyspnea and self-efficacy were entered as independent variables. To improve patients' perceptions of functional performance, nurses can use methods such as breathing techniques and upper- and lower-body exercises that increase optimal management of dyspnea. Nurses may increase the self-efficacy of managing dyspnea by helping patients master breathing techniques and exercise through coaching and providing vicarious experiences through patient support groups or pulmonary rehabilitation programs.  相似文献   
57.
Helicobacter pylori has been implicated in a number of upper gastrointestinal illnesses. In a controlled study, we have investigated the relationship between H. pylori infection and gastric emptying of solids in two groups of patients with chronic symptoms of dyspepsia. In the first group, 19 patients with non-ulcer dyspepsia and H. pylori infection underwent a standard test of gastric emptying after ingestion of 500 μCi of Tc-labelled chicken liver. The results were compared to a control group of 16 uninfected volunteers. We also studied a second group of 20 patients with previously diagnosed idiopathic gastroparesis for the prevalence of H. pylori infection and its relationship to symptom severity and rates of gastric emptying. In the first group of patients, the half-time of gastric emptying was significantly less among the infected patients compared to the uninfected volunteers (108 ± 9 vs. 142 ± 14 min, P < 0.05). In the second group of patients with gastroparesis, the prevalence of H. pylori was not significantly different among these patients than among 21 age and sex matched controls (20% vs. 38%, P = 0.32). Gastric emptying was markedly slow in all 20 patients in the second group but less so among the four with H. pylori infection. Symptom scores were no different between infected and uninfected patients. We conclude that H. pylori infection is not associated with abnormally slow gastric emptying. On the contrary, gastric H. pylori infection appears to be associated with mildly accelerated emptying of solids compared to normal controls. Idiopathic gastroparesis and dyspepsia related H. pylori infection are separate but sometimes overlapping disorders.  相似文献   
58.
59.
To assess the effect of stimulus correlated motion on the appearance of functional magnetic resonance images, conventional visual and motor protocols were each performed by four normal volunteers and an image co-registration technique was used to retrospectively monitor subject motion. In three studies synthetic data sets were constructed from single baseline images using the positional information obtained from the co-registration procedure. Cumulative difference images were then created from both the synthetic and functional image sets. Stimulus correlated motion was detected in all eight studies and the synthetic cumulative difference images showed striking similarities to the equivalent functional images in each case.  相似文献   
60.
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