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   4849篇
  免费   398篇
  国内免费   6篇
耳鼻咽喉   12篇
儿科学   157篇
妇产科学   173篇
基础医学   736篇
口腔科学   54篇
临床医学   584篇
内科学   843篇
皮肤病学   115篇
神经病学   446篇
特种医学   101篇
外科学   323篇
综合类   58篇
一般理论   6篇
预防医学   633篇
眼科学   69篇
药学   527篇
中国医学   3篇
肿瘤学   413篇
  2023年   40篇
  2022年   62篇
  2021年   102篇
  2020年   74篇
  2019年   129篇
  2018年   124篇
  2017年   97篇
  2016年   146篇
  2015年   121篇
  2014年   206篇
  2013年   267篇
  2012年   387篇
  2011年   356篇
  2010年   187篇
  2009年   188篇
  2008年   292篇
  2007年   359篇
  2006年   306篇
  2005年   313篇
  2004年   290篇
  2003年   229篇
  2002年   275篇
  2001年   48篇
  2000年   37篇
  1999年   48篇
  1998年   63篇
  1997年   43篇
  1996年   47篇
  1995年   33篇
  1994年   35篇
  1993年   33篇
  1992年   13篇
  1991年   25篇
  1990年   14篇
  1989年   18篇
  1988年   14篇
  1987年   19篇
  1986年   10篇
  1985年   15篇
  1984年   9篇
  1983年   10篇
  1982年   20篇
  1981年   15篇
  1980年   15篇
  1978年   9篇
  1977年   9篇
  1975年   8篇
  1974年   10篇
  1973年   11篇
  1971年   8篇
排序方式: 共有5253条查询结果,搜索用时 0 毫秒
101.
102.
ABSTRACT: BACKGROUND: According to the UK Adult Dental Health Survey (2009) 15% of adults aged 65-74, 30% aged 75-84 and 47% aged >85 years are edentulous and require complete dentures. Patients' quality of life and nutrition status are affected by poor dentures. The quality of the dental impression is the most important issue for improving the fit and comfort of new dentures. There is paucity of RCT evidence for which impression material is best for complete dentures construction. This study aims to compare two impression materials for effectiveness and cost effectiveness. METHODS: IMPROVDENT is a double-blind crossover trial comparing the use of alginate and silicone, two commonly used denture impression materials, in terms of patient preference and cost-effectiveness. Eighty five edentulous patients will be recruited and provided with two sets of dentures, similar in all aspects except for the impression material used (alginate or silicone). Patients will try both sets of dentures for a two-week period, unadjusted, to become accustomed to the feel of the new dentures (habituation period). Patients will then wear each set of dentures for a period of 8 weeks (in random order) during which time the dentures will be adjusted for optimum comfort. Finally, patients will be given both sets of dentures for a further two weeks to wear whichever denture they prefer (confirmation period). Patients will be asked about quality of life and to rate dentures on function and comfort at the end of each trial period and asked which set they prefer at the end of the habituation period (unadjusted denture preference) and confirmation period (adjusted denture preference). A health economic evaluation will estimate incremental cost-effectiveness ratios of producing dentures from the two materials. A qualitative study will investigate the impact of dentures on behaviour and quality of life. Funding: IMPROVDENT is funded by NIHR RfPB (PB-PG-0408-16300). DISCUSSION: This trial aims to provide evidence on the costs and quality of dentures cast from two different commonly used impression materials; the intention is to significantly impact on the quality of denture production within NHS dentistry. Trial Registration ISRCTN Register: ISRCTN01528038 UKCRN Portfolio ID: 8305.  相似文献   
103.
104.

Background

Prospective data on cardiac iron removal are limited beyond one year and longer-term studies are, therefore, important.

Design and Methods

Seventy-one patients in the EPIC cardiac substudy elected to continue into the 3rd year, allowing cardiac iron removal to be analyzed over three years.

Results

Mean deferasirox dose during year 3 was 33.6±9.8 mg/kg per day. Myocardial T2*, assessed by cardiovascular magnetic resonance, significantly increased from 12.0 ms ±39.1% at baseline to 17.1 ms ±62.0% at end of study (P<0.001), corresponding to a decrease in cardiac iron concentration (based on ad hoc analysis of T2*) from 2.43±1.2 mg Fe/g dry weight (dw) at baseline to 1.80 ±1.4 mg Fe/g dw at end of study (P<0.001). After three years, 68.1% of patients with baseline T2* 10 to <20 ms normalized (≥20 ms) and 50.0% of patients with baseline T2* >5 to <10 ms improved to 10 to <20 ms. There was no significant variation in left ventricular ejection fraction over the three years. No deaths occurred and the most common investigator-assessed drug-related adverse event in year 3 was increased serum creatinine (n=9, 12.7%).

Conclusions

Three years of deferasirox treatment along with a clinically manageable safety profile significantly reduced cardiac iron overload versus baseline and normalized T2* in 68.1% (32 of 47) of patients with T2* 10 to <20 ms.  相似文献   
105.
Objective: The purpose of this study was to examine ethnic variation in the relationship between individual socio-demographic factors, parental educational level, and late-life depressive symptoms in older African Americans and Caribbean Blacks.

Method: This cross-sectional study used data from the National Survey of American Life. A subsample of older African Americans (N = 837) and Caribbean Blacks (N = 271) was analyzed using multiple regression analysis.

Results: Findings suggest differences in predictors of depressive symptoms for the two ethnic groups. Among older African Americans, lower educational attainment and lower income were predictive risk factors for higher depressive symptoms. Findings among older Caribbean Blacks suggest that nativity and income were significantly associated with depressive symptoms. This study did not find support for any association between parental education and late-life depressive symptoms.

Conclusion: This study adds new information by considering ethnic variation in an examination of depressive symptoms in older Black Americans. The results contribute to the growing awareness of the older Caribbean Black population in the United States.  相似文献   

106.

Background

Surges in heart rate (HR) and blood pressure (BP) at apnea termination contribute to the hypertension seen in obstructive sleep apnea (OSA). Because childhood OSA prevalence peaks in the preschool years, we aimed to characterize the cardiovascular response to obstructive events in preschool-aged children.

Methods

Clinically referred children aged 3–5 years were grouped by obstructive apnea–hypopnea index (OAHI) into the following: primary snoring (PS) (OAHI ? 1 event/h [n = 21]), mild OSA (OAHI > 1– ? 5 [n = 32]), and moderate to severe (MS) OSA (OAHI > 5 [n = 28]). Beat-to-beat pulse transit time (PTT), an inverse continuous indicator of BP changes, and HR were averaged during the two halves (early and late) and during the peak after (post) each obstructive event and were expressed as percentage change from late- to post-event.

Results

We analyzed 422 events consisting of 55 apneas and 367 hypopneas. A significant post-event increase in HR and fall in PTT occurred in all severity groups (P < .05 for all). A greater response was associated with OSA, nonrapid eye movement sleep (NREM), cortical arousal, hypopneas, and oxygen desaturation (P < .05 for all).

Conclusions

Obstructive events elicit acute cardiovascular changes in preschool children. Such circulatory perturbations have been implicated in the development of hypertension, and our findings complement previous studies to suggest a cumulative impact of snoring on the cardiovascular system from childhood into adulthood.  相似文献   
107.

Background

Recent trials have shown that cytoreductive surgery and heated intraperitoneal chemotherapy (S+HIPEC) for colorectal cancer carcinomatosis (CRC-C) leads to 5-year, disease-free survival rates of more than 30%. Since these data represent a substantial change in the management of CRC-C, the objectives of this study were to determine physicians’ awareness of S+HIPEC for CRC-C and physician characteristics predictive of awareness of S+HIPEC for CRC-C.

Methods

This study was a mailed, cross-sectional survey of general surgeons and medical oncologists in Ontario.

Results

The response rate was 44.0% (214 of 487). Most respondents were men and younger than 50 years. There was an even split between those at academic and community hospitals. Overall, 46% of respondents were aware of S+HIPEC for CRC-C, and multivariate analysis showed that there were no physician characteristics predictive of awareness of S+HIPEC for CRC-C.

Conclusion

Physician awareness of S+HIPEC for CRC-C is low. Therefore, strategies to improve patient and physician knowledge about S+HIPEC for CRC-C are important to ensure appropriate treatment for patients.  相似文献   
108.
109.
110.
Background and Aim: The thiopurines azathioprine and 6‐mercaptopurine are effective in the management of patients with inflammatory bowel disease (IBD) in whom aminosalicylates, antibiotics and corticosteroids have failed to induce or maintain remission. Long‐term use of these agents has been linked to a greatly increased risk of non‐melanoma skin cancer and lymphatic cancer in organ transplant recipients. There is some evidence to suggest that IBD patients receiving thiopurines might be at increased risk of cancer. Our aim was to determine the incidence of cancer in a cohort of patients with IBD managed in our clinic, and to relate this to thiopurine exposure. Methods: We conducted a retrospective study based on the clinical and pathology records of patients attending a specialist IBD clinic at Groote Schuur Hospital, Cape Town, South Africa between 1960 and 2007. Results: We analyzed the records of 1084 patients. A total of 123 subjects (11.5%) had received thiopurine therapy. Cancer was identified in 51 patients (4.7%), including colorectal cancer (15 patients), melanoma (two patients), non‐melanoma skin cancer (seven patients) and non‐Hodgkin's lymphoma (five patients). A diagnosis of non‐melanoma skin cancer was significantly associated with thiopurine exposure (odds ratio 5.0, 95% confidence interval 1.1–22.8). Six of seven non‐melanoma skin cancers occurred in Caucasian patients, with a highly significant association with thiopurine use (odds ratio 12.4, 95% confidence interval 2.3–67.4). Conclusions: Patients with IBD who receive thiopurines are at increased risk of non‐melanoma skin cancer. The risk is highest in Caucasian patients, and is negligible in other groups.  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