全文获取类型
收费全文 | 1842篇 |
免费 | 117篇 |
国内免费 | 22篇 |
专业分类
耳鼻咽喉 | 6篇 |
儿科学 | 81篇 |
妇产科学 | 30篇 |
基础医学 | 192篇 |
口腔科学 | 67篇 |
临床医学 | 164篇 |
内科学 | 319篇 |
皮肤病学 | 36篇 |
神经病学 | 64篇 |
特种医学 | 349篇 |
外科学 | 323篇 |
综合类 | 33篇 |
一般理论 | 2篇 |
预防医学 | 138篇 |
眼科学 | 12篇 |
药学 | 68篇 |
中国医学 | 1篇 |
肿瘤学 | 96篇 |
出版年
2021年 | 24篇 |
2020年 | 18篇 |
2019年 | 19篇 |
2018年 | 35篇 |
2017年 | 18篇 |
2016年 | 24篇 |
2015年 | 21篇 |
2014年 | 46篇 |
2013年 | 40篇 |
2012年 | 45篇 |
2011年 | 65篇 |
2010年 | 56篇 |
2009年 | 39篇 |
2008年 | 38篇 |
2007年 | 57篇 |
2006年 | 50篇 |
2005年 | 55篇 |
2004年 | 45篇 |
2003年 | 39篇 |
2002年 | 38篇 |
2001年 | 40篇 |
2000年 | 39篇 |
1999年 | 39篇 |
1998年 | 53篇 |
1997年 | 52篇 |
1996年 | 71篇 |
1995年 | 54篇 |
1994年 | 47篇 |
1993年 | 49篇 |
1992年 | 29篇 |
1991年 | 37篇 |
1990年 | 25篇 |
1989年 | 51篇 |
1988年 | 55篇 |
1987年 | 42篇 |
1986年 | 38篇 |
1985年 | 67篇 |
1984年 | 26篇 |
1983年 | 40篇 |
1982年 | 33篇 |
1981年 | 30篇 |
1980年 | 17篇 |
1979年 | 20篇 |
1978年 | 15篇 |
1977年 | 39篇 |
1976年 | 31篇 |
1975年 | 21篇 |
1973年 | 11篇 |
1971年 | 9篇 |
1967年 | 16篇 |
排序方式: 共有1981条查询结果,搜索用时 15 毫秒
1.
2.
Monaural loudness balances were performed by eight normal-hearing subjects to determine the effect of click repetition rate on loudness sensation. Click trains of 500 msec duration were matched in loudness to a standard 500 msec 1000 Hz tone burst presented at three reference loudness levels (70, 80, and 90 phons). Click trains were presented at repetition rates of 11, 31, 51, and 91 clicks per sec. It was found that click trains at faster repetition rates required lower intensities for judgments of equal loudness sensation. This finding was attributed to the process of temporal loudness summation. The magnitude and nature of the temporal summation process as well as the influence of the reference loudness level are discussed. 相似文献
3.
INTRODUCTION: Barrett's esophagus, a syndrome in which the squamous mucosa that normally lines the distal esophagus is replaced with columnar epithelium, is found in a small percentage of patients presenting with gastroesophageal reflux disease (GERD). The columnar epithelium may be protective, guarding people afflicted with Barrett's esophagus from experiencing symptoms related to acid reflux. The purpose of this study was to investigate whether people with Barrett's esophagus subjectively experience fewer symptoms or symptoms of decreased severity, despite sustaining greater acid exposure, than those with GERD but without Barrett's syndrome. METHODS: We conducted a chart review of patients with GERD. Criteria for inclusion in the study were esophagogastroscopy, motility testing and a 24-hour pH study. Fifty-eight patients (29 men, 29 women) fulfilled these criteria. The diagnosis of GERD was based on an abnormal 24-hour pH study (DeMeester score). Of these 58 patients, 21 (14 men, 7 women) were found to have histologically confirmed Barrett's esophagus. A questionnaire to assess the key symptoms of GERD was administered, with a severity score ranging from 0 to 3 (3 being the most severe) for each symptom. RESULTS: Patients with Barrett's esophagus experienced symptoms significantly less severe (p < 0.01) than those with GERD. Patients with Barrett's esophagus also had a greater degree of acid exposure as identified by higher DeMeester scores (p = 0.056), longer episodes of acid exposure, a greater number of long episodes (> 5 min) of acid exposure (p = 0.033) and an increased percentage of time when their pH was less than 4. Patients with Barrett's esophagus had decreased resting lower esophageal sphincter tone, and number and amplitude of peristaltic contractions. CONCLUSIONS: For patients with Barrett's esophagus, the columnar epithelium may serve a protective function in guarding against symptoms of acid reflux. This has implications for the diagnosis and management of this condition. 相似文献
4.
5.
Question: Is gastroesophageal reflux a risk factor for the development of esophageal adenocarcinoma? Design: A case control study. Setting: A population-based study in Sweden between 1994 and 1997. Participants: Cases included all patients with gastric or esophageal adenocarcinoma and half of all patients with esophageal squamous cell cancer, under the age of 80 years and living in Sweden between Dec. 1, 1994, and Dec. 31, 1997. Controls were selected randomly from among persons matched for age (within 10 yr) and sex in the entire Swedish population, through the use of a population register, which is computerized and updated continuously. Assessment of risk factors: Symptomatic reflux was assessed according to the severity of the symptoms (heartburn only, regurgitation only, heartburn and regurgitation combined, nightly symptoms), frequency and duration. Adjustment was made for age, sex, body mass index, smoking history, alcohol ingestion, socioeconomic status, intake of fruit and vegetables, overall energy intake, posture and the degree of physical activity both at work and during leisure. Main outcome measures: Gastric and esophageal adenocarcinoma and esophageal squamous cell cancer. Main results: Among participants with recurrent symptoms of reflux, as compared with those without such symptoms, the odds ratios were 7.7 (95% CI, 5.3–11.4) for development of esophageal adenocarcinoma and 2.0 (95% CI, 1.4–2.9) for adenocarcinoma of the cardia. The more frequent, more severe and longer duration the symptoms of reflux were, the greater was the risk. Among persons with long-standing, severe symptoms of reflux, the odds ratios were 43.5 (95% CI, 18.3–103.5) for development of esophageal adenocarcinoma and 4.4 (95% CI, 1.7–11.0) for adenocarcinoma of the cardia. The risk of esophageal squamous cell carcinoma was not increased with reflux (odds ratio, 1.1; 95% CI, 0.7–1.9). Conclusion: The study identified a strong and probably causal relation between symptomatic reflux as a strong risk factor for esophageal adenocarcinoma and a relatively weak risk factor for adenocarcinoma of the gastric cardia. 相似文献
6.
7.
8.
G. Nikkhah J. C. Tonn O. Hoffmann H. -P. Kraemer J. L. Darling W. Schachenmayr R. Schönmayr 《Journal of neuro-oncology》1992,13(1):13-24
In this study we assessed the influence of patient- and drug-specific parameters in the short-term MTT-chemosensitivity assay in 150 primary cell cultures derived from human brain tumors. In 45 patients the MTT assay was directly compared with the CFA (Colony Forming Assay). Resistance was 10-20% higher in the MTT assay than in the CFA, but there was a good agreement in both assays, that more malignant gliomas had a higher in vitro chemosensitivity against ACNU and BCNU. Overall the results demonstrate, that there is no uniform correlation between the in vitro chemosensitivity and the histopathological classification of the tumors, which corresponds well to the clinical situation. On the basis of this study we suggest prospective clinical trials with the MTT assay in human brain tumors. 相似文献
9.
10.
A randomized controlled trial of electromagnetic therapy in the primary care management of venous leg ulceration 总被引:1,自引:1,他引:0
OBJECTIVE: The aim was to establish the potential efficacy, tolerabilityand side-effect profile of electromagnetic therapy as an adjunctto conventional dressings in the treatment of venous leg ulcers. METHOD: A prospective, randomized, double blind controlled clinicaltrial was carried out in a dedicated leg ulcer clinic basedin one urban general practice. Nineteen patients with leg ulcersof confirmed venous aetiology were assessed. The main outcomemeasures were rate and scale of venous leg ulcer healing, changesin patient-reported pain levels, quality of life, degree ofmobility, side effect profile and acceptability to patientsand staff. RESULTS: Sixty-eight per cent of patients attending this dedicated clinicachieved improvements in the size of their ulcer (4, 21%, healedfully) and in reduced pain levels (P < 0.05) during the trial,despite the chronicity of ulcer histories. Patients treatedwith electromagnetic therapy at 800 Hz were found at day 50to have significantly greater healing (P < 0.05) and paincontrol (P < 0.05) than placebo therapy or treatment with600 Hz. All patients reported improved mobility at the end ofthe study. The electromagnetic therapy was well tolerated bypatients, with no differences between groups in reporting adverseevents, and proved acceptable to staff. CONCLUSION: Despite the small numbers in this pilot study, electromagnetictherapy provided significant gains in the healing of venousleg ulcers and reduction in pain. Keywords. Electromagnetic therapy, RCT, leg ulcers, primary care. 相似文献