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   2562篇
  免费   93篇
  国内免费   11篇
耳鼻咽喉   12篇
儿科学   73篇
妇产科学   17篇
基础医学   302篇
口腔科学   45篇
临床医学   137篇
内科学   749篇
皮肤病学   216篇
神经病学   178篇
特种医学   136篇
外科学   282篇
综合类   2篇
预防医学   82篇
眼科学   64篇
药学   137篇
中国医学   2篇
肿瘤学   232篇
  2023年   16篇
  2022年   18篇
  2021年   39篇
  2020年   19篇
  2019年   34篇
  2018年   34篇
  2017年   28篇
  2016年   33篇
  2015年   39篇
  2014年   49篇
  2013年   65篇
  2012年   122篇
  2011年   153篇
  2010年   89篇
  2009年   80篇
  2008年   147篇
  2007年   173篇
  2006年   181篇
  2005年   190篇
  2004年   189篇
  2003年   200篇
  2002年   197篇
  2001年   32篇
  2000年   24篇
  1999年   41篇
  1998年   52篇
  1997年   50篇
  1996年   46篇
  1995年   51篇
  1994年   32篇
  1993年   29篇
  1992年   21篇
  1991年   15篇
  1990年   18篇
  1989年   16篇
  1988年   16篇
  1987年   16篇
  1986年   9篇
  1985年   13篇
  1984年   10篇
  1983年   12篇
  1982年   11篇
  1981年   6篇
  1980年   10篇
  1979年   5篇
  1978年   4篇
  1977年   9篇
  1976年   4篇
  1975年   4篇
  1974年   4篇
排序方式: 共有2666条查询结果,搜索用时 421 毫秒
91.
GeroScience - The rs1333049 (G/C) polymorphism located on chromosome 9p21.3 is a candidate to influence extreme longevity owing to its association with age-related diseases, notably coronary artery...  相似文献   
92.
93.
Annals of Nuclear Medicine - This study aimed to evaluate the accuracy of six threshold-based segmentation methods with different target-to-background ratios (TBR), images with different voxel...  相似文献   
94.
95.
This study sought to demonstrate the feasibility of estimating the source strength during implantation in brachytherapy. The requirement for measuring the strengths of the linked sources was investigated. The utilized sources were 125I with air kerma strengths of 8.38–8.63 U (μGy m2 h–1). Measurements were performed with a plastic scintillator (80 mm × 50 mm × 20 mm in thickness). For a source-to-source distance of 10.5 mm and at source speeds of up to 200 mm s–1, a counting time of 10 ms and a detector-to-needle distance of 5 mm were found to be the appropriate measurement conditions. The combined standard uncertainty (CSU) with the coverage factor of 1 (k = 1) was ∼15% when using a grid to decrease the interference by the neighboring sources. Without the grid, the CSU (k = 1) was ∼5%, and an 8% overestimation due to the neighboring sources was found to potentially cause additional uncertainty. In order to improve the accuracy in estimating source strength, it is recommended that the measurment conditions should be optimized by considering the tradeoff between the overestimation due to the neighboring sources and the intensity of the measured value, which influences the random error.  相似文献   
96.
This report describes an orthognathic surgical case employing horseshoe Le Fort I osteotomy (HLFO) combined with mid-alveolar osteotomy and bilateral sagittal split ramus osteotomy (BSSRO) for a patient with severe unilateral scissor bite and bimaxillary protrusion. A female patient (aged 26 years, 2 months) presented with a chief complaint of dysmasesis caused by scissor bite on the right side. The clinical examination revealed difficulty in lip closure and a convex profile. Overerupted right maxillary premolars and molars and lingual tipping of the right mandibular premolars and molars were indicated before treatment. After 3 months of presurgical orthodontic treatment, two-jaw surgery involving a combination of HLFO with mid-alveolar osteotomy and BSSRO was performed. A good interdigitation in the right side was established by superior-posterior-medial movement of the dento-alveolar segment of the maxilla. Next, both the maxilla and mandible were moved superiorly and posteriorly to correct the improper lip protrusion, thereby improving the patient''s profile. Our results suggest that this new orthognathic surgery technique—achieved by combining HLFO with mid-alveolar osteotomy and BSSRO—is effective for adult patients exhibiting severe unilateral scissor bite and bimaxillary protrusion.  相似文献   
97.
Prevalence of fatty liver in Japanese children and relationship to obesity   总被引:32,自引:0,他引:32  
The prevalence of fatty liver in children is unknown and its relationship to obesity is poorly defined. The present study of 810 northern Japanese children (4–12 years old) determined the prevalence of fatty liver in the pediatric population and its relationship to obesity. Diagnosis of fatty liver was based on established real-time ultrasonographic criteria. The overall prevalence of fatty liver was 2.6% and was higher for boys (3.4%) than for girls (1.8%), although not statistically significant (P=0.15). Fatty liver was found in children as young as 6 years of age. There was no significant association between the prevalence of fatty liver and height (physical growth). There was a strong positive correlation between fatty liver prevalence and established obesity indices: Rohrer's index-2 linear trend =59.2,P<0.0001; body mass index-2 linear trend =91.6,P<0.0001; and age-gender-adjusted Japanese standard index of weight for height-2 linear trend =93.2,P<0.0001. However, direct measurement of abdominal subcutaneous fat thickness by ultrasonography was the best predictor of fatty liver: 2 linear trend =159,P<0.0001. These results indicate that fatty liver may develop very early in life, and there is a direct relationship between degree of obesity and fatty liver in children.  相似文献   
98.
Objective: Gastric cancer (GC) and adenoma (GA) are reported to be related to atrophic gastritis, in which the serum pepsinogen (PG) I level and the PGI/PGII ratio (I/II ratio) are reduced. To verify that the finding of a low PG level increases the risk for GC and GA, we investigated the correlation between low PG levels and the prevalence of GC and GA in individuals.
Methods: The 2,039 subjects (734 Japanese men, mean age 68.5 yr, and 1,305 women, mean age 66.7 yr), selected from among 10,996 local residents who underwent health check-ups based on reductions in their serum PG levels, underwent upper gastrointestinal endoscopy.
Results: Gastrointestinal endoscopy detected 21 GCs and 15 GAs. The prevalence of GC was higher than that in the residents without low serum PG. The percentage of early stage of GC (90%) was significantly higher than that of GC detected in unscreened residents (56.9%). The prevalence of GC in men was closely and significantly correlated with the I/II ratio (  r = 0.935  ,   p = 0.0063  ), whereas there was less correlation with age (  r = 0.842  ,   p = 0.0734  ). The prevalence of GA was also closely and significantly correlated with the I/II ratio in men (  r = 0.881  ,   p = 0.0203  ), but not with age (  r = 0.163  ,   p = 0.7928  ). In women the prevalence of GC (r 5 0.744,   p = 0.090  ) and GA (  r = 0.678  ,   p = 0.1392  ) did not correlate as strongly with the I/II ratio, although the highest prevalence was seen in the group with the lowest I/II ratio.
Conclusion: Our study verified that a low I/II ratio signifies a high risk for GC and GA and that measuring serum PG levels can be used as a screening method for GC and GA.  相似文献   
99.
Pleomorphic xanthoastrocytomas (PXAs) are rare low-grade astrocytic tumors that typically present as superficial nodular cystic tumors of the cerebrum attached to the leptomeninx. Histologically, they are pleomorphic, hypercellular glial neoplasms. Despite the presence of microscopic pleomorphism, patients’ postoperative prognosis is generally good. Anaplastic PXAs (APXAs) have a high mitotic index and patients with APXAs have a worse prognosis than patients with PXAs. Here, we report an autopsy case of APXA initially diagnosed as PXA. After gross total resection, the tumor recurred and was diagnosed as an APXA; thereafter, the patient died. An autopsy revealed that the tumor had relapsed at the primary site and had spread to the leptomeningeal space while concurrently invading the cerebrum including the periventricular area forming multifocal lesions. The histological findings of the autopsy were similar to those for epithelioid glioblastoma (EGBM) and small cell glioblastoma (SCGBM). In particular, the periventricular area with multifocal lesions was composed of SCGBM-like cells. It has been shown that multifocal lesions are frequently identified in patients with SCGBM. This is the first histopathologically confirmed case of APXA-related tumor presenting with periventricular extension and multifocal lesion formation. The periventricular extension might be a feature of PXAs and APXAs. However, suspected periventricular spread on imaging in past cases of PXAs and APXAs might instead represent the malignant transformation of these tumors to glioblastoma-like high-grade tumors, which often show SCGBM-like histological patterns.  相似文献   
100.
Posterior reversible encephalopathy syndrome (PRES) is a neurological disorder characterized by seizures, altered mental status and visual disorders, along with characteristic radiological findings. It is strongly related to hypertension induced by steroids and other immunosuppressive agents. There are an increasing number of reports regarding PRES arising during the course of chemotherapy for hematological malignancies. To clarify the risk factors for this phenomenon, we retrospectively analyzed pediatric patients undergoing treatment for hematological malignancies. Of 161 patients, six patients (3.7 %) developed PRES with characteristic clinical and radiographic findings. Univariate analysis revealed that tumor lysis syndrome (TLS) was a significant risk factor for the onset of PRES. TLS is a significant risk factor for the development of PRES in pediatric patients receiving chemotherapy for hematological malignancies.  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