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   8543篇
  免费   376篇
  国内免费   59篇
耳鼻咽喉   88篇
儿科学   77篇
妇产科学   65篇
基础医学   993篇
口腔科学   284篇
临床医学   702篇
内科学   1818篇
皮肤病学   271篇
神经病学   556篇
特种医学   454篇
外科学   1613篇
综合类   50篇
一般理论   1篇
预防医学   384篇
眼科学   75篇
药学   688篇
中国医学   28篇
肿瘤学   831篇
  2023年   40篇
  2022年   88篇
  2021年   149篇
  2020年   89篇
  2019年   120篇
  2018年   162篇
  2017年   106篇
  2016年   143篇
  2015年   140篇
  2014年   186篇
  2013年   227篇
  2012年   385篇
  2011年   436篇
  2010年   252篇
  2009年   180篇
  2008年   345篇
  2007年   371篇
  2006年   361篇
  2005年   350篇
  2004年   351篇
  2003年   352篇
  2002年   320篇
  2001年   296篇
  2000年   313篇
  1999年   299篇
  1998年   128篇
  1997年   70篇
  1996年   66篇
  1995年   79篇
  1994年   69篇
  1993年   49篇
  1992年   217篇
  1991年   198篇
  1990年   217篇
  1989年   220篇
  1988年   176篇
  1987年   193篇
  1986年   161篇
  1985年   154篇
  1984年   101篇
  1983年   83篇
  1981年   50篇
  1979年   94篇
  1978年   41篇
  1977年   52篇
  1974年   47篇
  1972年   39篇
  1971年   40篇
  1969年   45篇
  1968年   40篇
排序方式: 共有8978条查询结果,搜索用时 15 毫秒
991.

Background  

Assessing indications for adjuvant chemotherapy (CT) in patients with hormone receptor (HR)-positive/human epidermal receptor 2 (HER2)-negative breast cancer remains a challenge for oncologists. In this study, we evaluated whether forkhead-box protein A1 (FOXA1) expression was a prognostic and predictive marker for HR-positive breast cancer.  相似文献   
992.

Background  

BRCA1 and BRCA2 are two major tumor suppressor genes for hereditary breast and ovarian cancer. In sporadic breast cancer, although somatic mutations of these genes are rare, loss of heterozygosity (LOH) at BRCA1 and BRCA2 loci is common.  相似文献   
993.
The prevalence and clinical characteristics of bacterial pneumonia after living donor liver transplantation (LDLT) have not yet been elucidated. We performed a retrospective analysis of 346 LDLT recipients. Fifty patients (14.5%) experienced bacterial pneumonia after LDLT, and they had a higher short-term mortality rate (42.0%) than patients with other types of bacterial infections after LDLT. Gram-negative bacteria accounted for 84.0% of the causative pathogens. A multivariate analysis showed that preoperative diabetes (P < 0.01), United Network for Organ Sharing status 1 or 2A (P < 0.01), and an operative blood loss > 10 L (P = 0.03) were significant risk factors for bacterial pneumonia after LDLT. Post-LDLT pneumonia was associated with the following post-LDLT events: the prolonged use of mechanical ventilation (≥3 days), a prolonged stay in the intensive care unit (≥7 days), the creation of a tracheostomy, primary graft dysfunction, the use of mycophenolate mofetil, and the need for renal replacement therapy. Among patients with bacterial pneumonia, the mortality rate was higher for patients with delayed-onset pneumonia, which occurred at least 10 days after transplantation (n = 15), and it was significantly associated with graft dysfunction. A combination of broad-spectrum antibiotics and aminoglycosides provided cover for most gram-negative bacteria except Stenotrophomonas maltophilia, which was associated with a longer period of mechanical ventilation and was resistant to commonly used broad-spectrum antibiotics. Delayed-onset bacterial pneumonia is a serious type of bacterial infection after LDLT and is frequently associated with graft dysfunction. The multidrug resistance of S. maltophilia is an issue that needs to be addressed. Liver Transpl, 2012. ? 2012 AASLD.  相似文献   
994.
Aims/Introduction: Oral ingestion of carbohydrate triggers secretion of glucagon‐like peptide (GLP)‐1, which inhibits the postprandial rise in blood glucose levels. However, the mechanism of carbohydrate‐induced GLP‐1 secretion from enteroendocrine L cells remains unclear. In the present study, GLP‐1 secretion was examined by meal tolerance tests of healthy Japanese volunteers. Materials and Methods: Twenty‐one healthy Japanese men participated in the study. The meal tolerance test was performed with modified nutrient compositions, with or without pretreatment with the α‐glucosidase inhibitor acarbose, or with substitution of sucrose with an equivalent dose of sweeteners in the meal. Blood concentrations of glucose, insulin, GLP‐1, and apolipoprotein (Apo) B‐48 were measured. Results: GLP‐1 secretion started concomitant with the increase in blood glucose levels 10 min after meal ingestion. Insulin secretion started at 5 min, before the increase in blood glucose levels, reflecting the contribution of direct nutrient stimulation on the former parameter and neural regulation in the latter. Carbohydrate retention in the gut lumen induced by acarbose pretreatment extended postprandial GLP‐1 secretion and negated the increase in serum ApoB‐48 levels. GLP‐1 secretion was markedly decreased by a reduction in the amount of sucrose in the meal and was not restored by an equivalent dose of sweeteners used to compensate for the sweet taste. Conclusions: The results indicate that direct stimulation of L cells with sugar, but not sweetener, is required for carbohydrate‐induced GLP‐1 secretion. In addition, inhibition of digestion of dietary carbohydrate by α‐glucosidase inhibitors may prevent postprandial hyperglycemia by increasing GLP‐1 secretion and by inhibiting glucose absorption. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2011.00163.x, 2011)  相似文献   
995.
A nationwide statistical survey of 4226 dialysis facilities was conducted at the end of 2010, and 4166 facilities (98.6%) responded. The number of new patients introduced into dialysis was 37 512 in 2010. This number has decreased for two consecutive years since it peaked in 2008. The number of patients who died in 2010 was 28 882, which has been increasing every year. The number of patients undergoing dialysis at the end of 2010 was 298 252, which is an increase of 7591 (2.6%) compared with that at the end of 2009. The number of dialysis patients per million at the end of 2010 was 2329.1. The crude death rate of dialysis patients in 2010 was 9.8%, and has been gradually increasing. The mean age of the new patients introduced into dialysis was 67.8 years and the mean age of the entire dialysis patient population was 66.2 years. Regarding the primary disease of the new patients introduced into dialysis, the percentage of patients with diabetic nephropathy was 43.6%, which is a slight decrease from that in the previous year (44.5%). Patients with diabetic nephropathy as the primary disease accounted for 35.9% of the entire dialysis patient population, which approaches the percentage of patients with chronic glomerulonephritis as the primary disease (36.2%). The percentage of patients who had undergone carpal tunnel release surgery (CTx) was 4.3%, which is a slight decrease from that at the end of 1999 (5.5%). The decrease in the percentage of patients who had undergone CTx was significant among the patients with dialysis durations of 20–24 years (1999, 48.0%; 2010, 23.2%). A total weekly Kt/V attributable to peritoneal dialysis and their residual functional kidney was 1.7 or higher for 59.4% of patients who underwent peritoneal dialysis.  相似文献   
996.

Objective

To evaluate the effect of adaptive iterative dose reduction (AIDR) on image noise and image quality as compared with standard filtered back projection (FBP) in 320-detector row CT coronary angiography (CTCA).

Methods

50 patients (14 females, mean age 68±9 years) who underwent CTCA (100 kV or 120 kV, 400–580 mA) within a single heartbeat were enrolled. Studies were reconstructed with FBP and subsequently AIDR. Image noise, vessel contrast and contrast-to-noise ratio (CNR) in the coronary arteries were evaluated. Overall image quality for coronary arteries was assessed using a five-point scale (1, non-diagnostic; 5, excellent).

Results

All the examinations were performed in a single heartbeat. Image noise in the aorta was significantly lower in data sets reconstructed with AIDR than in those reconstructed with FBP (21.4±3.1 HU vs 36.9±4.5 HU; p<0.001). No significant differences were observed between FBP and AIDR for the mean vessel contrast (HU) in the proximal coronary arteries. Consequently, CNRs in the proximal coronary arteries were higher in the AIDR group than in the FBP group (p<0.001). The mean image quality score was improved by AIDR (3.75±0.38 vs 4.24±0.38; p<0.001).

Conclusion

The use of AIDR reduces image noise and improves image quality in 320-detector row CTCA.CT coronary angiography (CTCA) is a robust non-invasive imaging modality with high spatial and temporal resolution that enables accurate diagnosis or exclusion of coronary artery disease [1-4]. However, CTCA usually exposes the patient to a substantial amount of radiation (9.4–21.4 mSv) [5-7]. Therefore, several scanning techniques, such as ECG-based tube current modulation, prospective ECG triggering and reduced tube voltage scanning, have been developed to reduce the patient''s radiation exposure [6-8]. Reductions of the tube current also lead to lower radiation exposure, as the tube current correlates to dose in a linear fashion. However, lower radiation leads to an increase in CT image noise because the current reconstruction method, filtered back projection (FBP), is unable to consistently generate diagnostic-quality images with reduced tube currents [9].Recently, the adaptive iterative dose reduction technique has been developed as a new reconstruction algorithm to improve image noise [10-12], and has already been shown to reduce the radiation dose in clinical practice [13-16]. Adaptive iterative dose reduction (AIDR) developed for CT by Toshiba Medical Systems Corporation is a modified iterative reconstruction technique in which the original high-noise image undergoes a number of reconstructions that reduce image noise until the resultant image displays the desired noise level. This technique is expected to reduce the radiation dose for a similar noise level to FBP.To our knowledge, no study has evaluated the quality of CT images using AIDR. The purpose of this study was to evaluate the effect of AIDR regarding image noise and image quality in comparison with FBP, using the same raw data set for both FBP and AIDR, in 320-detector row CTCA.  相似文献   
997.
998.
Background: Because coronary computed tomography angiography (CCTA) by 320-area detector CT (320-ADCT) can be obtained in a short time, the probability of meeting up with premature contraction (PC) during scanning may be lower in 320-ADCT compared to 64-MDCT. The purpose is to compare the probability of meeting up with PC, scanning time, and image quality in patients with PC between the 2 groups (320-ADCT vs 64-MDCT). Methods: We have never rejected any CCTA examination due to arrhythmias. The 320-ADCT was performed in 2424 consecutive patients to include 70 atrial fibrillations (Afibs) and 64-MDCT in 1905 consecutive patients to include 51 Afibs. After exclusion of the patients with Afibs, we studied the probability of meeting up with PC during scanning and we compared the scanning time, image quality, and reconstruction phase for patients with PC between the 2 groups. Results: The probability of meeting up with PC during scanning in 320-ADCT (2.0%) is significantly lower (P<0.0001) than 64-MDCT (5.6%). For patients with PC, scanning time in 320-ADCT (2.9±0.6 s) was significantly shorter (P<0.0001) than 64-MDCT (9.5±1.9 s) and image quality in 320-ADCT (2.9±0.3 points) was significantly higher (P<0.0001) than 64-MDCT (2.2±0.8 points). CCTA was reconstructed in mid-diastolic phase in 93% of patients with PC using the 320-ADCT with arrhythmia rejection system. Conclusion: The scanning time of 320-ADCT was 1/3 in comparison with that of 64-MDCT, and the probability of meeting up with PC during scanning in 320-ADCT was 1/3 in comparison with that in 64-MDCT.  相似文献   
999.
The international literature shows that HIV-risk behaviour for women mostly occurs in the context of intimate relationships. Power imbalances in the social, economic and cultural spheres put women at risk. This paper addresses the roles of male partners in women's engagement in drug-use behaviour and drug-related HIV-risk behaviour in Indonesia. Data were gathered through in-depth interviews with 19 women who had injected drugs in the previous month in three sites in central Java. Most of the women had male partners who also injected drugs. Results show that male partners play a significant role in the initiation of drug use, the provision of drugs, injecting behaviour and in the constitution of women injectors' social networks. These findings suggest the need to develop couple-based interventions and to facilitate women-only groups as part of HIV prevention.  相似文献   
1000.
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