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   14428篇
  免费   857篇
  国内免费   222篇
耳鼻咽喉   345篇
儿科学   138篇
妇产科学   265篇
基础医学   2209篇
口腔科学   183篇
临床医学   1055篇
内科学   3106篇
皮肤病学   397篇
神经病学   1152篇
特种医学   1035篇
外科学   1890篇
综合类   52篇
一般理论   4篇
预防医学   319篇
眼科学   207篇
药学   1370篇
中国医学   193篇
肿瘤学   1587篇
  2023年   112篇
  2022年   351篇
  2021年   527篇
  2020年   281篇
  2019年   379篇
  2018年   448篇
  2017年   384篇
  2016年   574篇
  2015年   782篇
  2014年   839篇
  2013年   925篇
  2012年   1422篇
  2011年   1377篇
  2010年   889篇
  2009年   658篇
  2008年   894篇
  2007年   831篇
  2006年   698篇
  2005年   628篇
  2004年   532篇
  2003年   422篇
  2002年   352篇
  2001年   178篇
  2000年   175篇
  1999年   142篇
  1998年   77篇
  1997年   51篇
  1996年   43篇
  1995年   30篇
  1994年   22篇
  1993年   19篇
  1992年   37篇
  1991年   47篇
  1990年   38篇
  1989年   37篇
  1988年   26篇
  1987年   44篇
  1986年   21篇
  1985年   33篇
  1984年   17篇
  1983年   16篇
  1982年   9篇
  1979年   12篇
  1978年   13篇
  1976年   9篇
  1974年   8篇
  1973年   8篇
  1971年   9篇
  1969年   12篇
  1968年   10篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
101.

Purpose

The purpose of this study was to evaluate the prognostic value of metabolic tumor volume (MTV) measured by 18F-fluorodeoxyglucose positron emission tomography-computed tomography (FDG-PET/CT) in patients with diffuse large B-cell lymphoma (DLBCL) treated with rituximab-containing immunochemotherapy.

Methods

Patients with newly diagnosed DLBCL who underwent pre-treatment torso FDG-PET/CT scan taken within 10 days before treatment were included. MTV was defined as the volume of hypermetabolic tissue with a standardized uptake value (SUV) greater than a threshold value of 2.5 and calculated using volume viewer software. Association of MTV with patient characteristics and survival were compared.

Results

A total of 96 patients were evaluated. During a median follow-up period of 27.8 months, 3-year event-free survival (EFS) and overall survival was 69.5 % and 72.9 %, respectively. The Ann Arbor staging showed a limitation of prognosis because there was no difference of EFS between patients with Ann Arbor stage II and those with stage III. On the contrary, among patients with Ann Arbor stage II or III disease (n?=?53), the higher MTV group showed significantly inferior EFS compared with the lower MTV group.

Conclusions

In the current study, we identified the pre-treatment MTV measured by FDG-PET/CT as a potential predictor of survival in patients with DLBCL treated with rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone (R-CHOP), at least in Ann Arbor stage II and III disease.  相似文献   
102.

Purpose

The purpose of this study was to identify the frequency and possible cause of diffuse intrathoracic uptake on post-therapy I-131 scans in thyroid cancer patients.

Methods

We retrospectively reviewed 781 post-therapy scans of 755 thyroid cancer patients who underwent total thyroidectomy and radioactive iodine therapy between January and December 2010. Diffuse intrathoracic uptake on post-therapy scans was examined, and clinical patient characteristics including sex, age, regimen for thyroid-stimulating hormone (TSH) stimulation (thyroid hormone withdrawal or recombinant human TSH injection), TSH, thyroglobulin (Tg) and anti-thyroglobulin antibody (anti-Tg Ab) levels, therapeutic dose of radioactive iodine therapy and prior history of radioactive iodine therapy were recorded.Scan findings were correlated with chest CT, chest radiographs, laboratory tests and/or clinical status. Diffuse intrathoracic uptake without evidence of pathologic condition was categorized as indeterminate. The association between clinical characteristics and intrathoracic uptake were analyzed for negative intrathoracic uptake and indeterminate uptake groups.

Results

Diffuse intrathoracic uptake on post-therapy scans was demonstrated in 39 out of 755 (5.2 %) patients, among which 3 were confirmed as lung metastasis. The 14 patients that showed high Tg or anti-Tg Ab levels were considered to be at risk of having undetected micrometastasis on other imaging modalities. The remaining 22 were indeterminate (2.9 %).Upon comparison of negative intrathoracic uptake and indeterminate uptake groups, TSH stimulation by thyroid hormone withdrawal was shown to be significantly correlated with diffuse intrathoracic uptake (p < 0.05).

Conclusion

The frequency of diffuse intrathoracic uptake on post-therapy scans was 5.2 % and could be seen in thyroid cancer patients with underlying lung metastasis as well as those without definite pathologic condition. In the latter, there was a higher frequency for diffusely increased intrathoracic uptake in those who underwent thyroid hormone withdrawal rather than recombinant human TSH injection.  相似文献   
103.

Objectives

To assess the image quality of ultra-low-dose computed tomography (ULDCT) using sinogram-affirmed iterative reconstruction (SAFIRE) compared to reduced dose CT (RDCT).

Methods

Eighty-one consecutive patients underwent non-enhanced ULDCT using 80 kVp and 30 mAs and contrast-enhanced RDCT using automated tube potential selection and tube current modulation. CT images were reconstructed with SAFIRE. Image noise and subjective image quality of normal structures and various pulmonary lesions were assessed.

Results

The mean effective doses were 0.29?±?0.03 and 2.88?±?1.11 mSv for ULDCT and RDCT, respectively. ULDCT had significantly higher noise (p?<?0.001). Image quality of five normal structures was diagnostic in 91.1 % of ULDCT and 100 % of RDCT. With ULDCT, the frequencies of non-diagnostic image quality were 2.0 (1/50), 4.6 (13/280), 25.5 (14/55), and 40.0 (8/20)% for BMIs of?<?20, 20–25, 25–30, and >30. In the assessment of pulmonary lesions, non-diagnostic image quality was observed for 11.2 % of all lesions, 60.9 % of decreased attenuation (significantly more frequent for upper lung lesions), and 23.5 % of ground-glass nodules.

Conclusion

ULDCT generates diagnostic images in patients with a BMI ≤25, but is of limited use for lesions with decreased attenuation, ground-glass nodules, or those located in the upper lobe.

Key Points

? Iterative reconstruction enables ultra-low-dose CT (ULDCT) with very low radiation doses. ? Image quality of ULDCT depends on the patient body mass index (BMI). ? Selection of kVp and mAs depends on both BMI and lesion type. ? Diagnosis of pulmonary emphysema or ground-glass nodules requires higher radiation doses.  相似文献   
104.

Purpose

The new modality of an integrated positron emission tomography/magnetic resonance imaging (PET/MRI) has recently been introduced but not validated. Our objective was to evaluate clinical performance of 18F-fluoro-2-deoxyglucose (18F-FDG) PET/MRI in patients with head and neck cancer.

Methods

This retrospective study was conducted between January 2013 and February 2013. Ten patients (eight men, two women; mean age, 61.4 ± 13.4 years) with histologically proven head and neck tumors were enrolled. Whole-body PET/MRI and regional positron emission tomography (PET) with dedicated MRI were sequentially obtained. Maximum standardized uptake value (SUVmax), SUVmean, metabolic tumor volume, total lesion glycolysis and contrast enhancement were analyzed. A total of ten whole-body positron emission tomography (PET), ten regional positron emission tomography (PET), ten dedicated MRI and ten regional PET/gadolinium-enhanced T1-weighted (Gd)-MRI images were analyzed for initial staging. Two nuclear medicine physicians analyzed positron emission tomography (PET) and PET/MRI with a consensus. One radiologist analyzed dedicated MRI. The primary lesions and number of metastatic lymph nodes analyzed from each image were compared.

Results

Eight patients were diagnosed with head and neck cancer (one tongue cancer, four tonsillar cancers, one nasopharyngeal cancer and two hypopharyngeal cancers) by histological diagnosis. Two benign tumors (pleomorphic adenoma and Warthin tumor) were diagnosed with surgical operation. Whole-body positron emission tomography (PET) and regional positron emission tomography (PET) attenuated by MRI showed good image quality for the lesion detection. Whole-body positron emission tomography (PET) and regional positron emission tomography (PET) detected ten primary sites and compensated for a missed lesion on dedicated MRI. A discordant number of suspicious lymph node metastases was noted according to the different images; 22, 16, 39 and 40 in the whole-body positron emission tomography (PET) only, dedicated MR, regional positron emission tomography (PET) only and regional PET/Gd-MRI, respectively. There was no distant metastasis based on analysis of whole-body positron emission tomography (PET) and whole-body PET/Dixon-volume interpolated breathhold examination (VIBE) MRI. Regional PET/Gd-MRI combined with whole-body PET/MRI modified staging in three patients. Lesions of primary tumor and suspicious metastasis were well detected on both value of SUVmax and visual analysis. The regional PET/Gd-MRI combined with whole-body PET/MRI showed convenient clinical staging performance compared with positron emission tomography (PET) and MRI alone.

Conclusion

In this preliminary study, PET attenuated by MRI showed good image quality to detect lesions. And whole-body PET/MRI as a single modality was feasible for staging in a clinical setting. Whole-body positron emission tomography (PET), regional positron emission tomography (PET), dedicated MRI and regional PET/Gd-MRI showed discordant results in lesion detection. These discordant results might be synergistic effect for accurate staging.  相似文献   
105.

Background

Endoscopic submucosal dissection (ESD) is an alternative to surgical resection for treating early gastric cancer (EGC). However, there have been limited reports on the long-term outcome of ESD compared to that of surgical resection. The aim of this study was to evaluate the immediate and long-term clinical and oncologic outcomes of ESD compared to surgical resection.

Method

We retrospectively reviewed data of patients in five centers who were treated with ESD or surgical resection for EGC within expanded criteria for ESD from 2006 to 2008.

Result

ESD group had significantly shorter procedure times, shorter fasting period, and shorter hospital stay than the surgical resection group. Immediate complications in the surgical resection group were more common compared to those in the ESD group. Five-year cancer recurrence rate of the ESD group was 12.3 % and significantly higher than 2.1 % of the surgical resection group (P = 0.001). Five-year disease-free survival rate of the surgical resection group was 97 %, which was significantly higher than 85 % of the ESD group (P = 0.001). Metachronous lesions were equally found every year during the follow-up period in the ESD group. Five-year overall survival rates were 100 % for both groups.

Conclusion

ESD might be an acceptable and effective treatment for EGC considering overall survival rates with fewer early complication rates and shorter duration of hospital stay compared to surgical resection. However, intensive and persistent endoscopic surveillance should be performed after ESD for early detection of metachronous lesions.
  相似文献   
106.
We investigated the relationship between geriatric nutritional risk index (GNRI) and subpopulation lymphocyte counts (SLCs) in hemodialysis (HD) and peritoneal dialysis (PD) patients and evaluated whether they can be helpful in the diagnosis of malnutrition in these patients. We examined the GNRI and SLCs of 50 HD patients (mean: 55.8?±?12.7 years; 28 men and 22 women) and 16 Continuous Ambulatory Peritoneal Dialysis (CAPD) patients (mean: 49.8?±?14.5 years; 10 men and six women). The GNRI is calculated based on the serum albumin level, dry weight, and ideal body weight and uses the following equation: GNRI?=?[14.89?×?albumin (g/dL)]?+?[41.7?×?(weight/ideal body weight)]. SLCs were evaluated using flow cytometry. T-tests and χ2 tests were performed to compare the two groups. Logistic regression analysis was performed for predicting malnutrition in dialysis patients. The average GNRI value was 100.1?±?8.4 in HD patients and 99.2?±?8.1 in PD patients, and no significant differences in GNRI or SLC were observed between the two groups. SLCs were higher in patients with higher GNRI (GNRI?≥?100) although there was no statistical difference. Logistic regression for predicting malnutrition according to GNRI revealed that age, female sex, and CD19 counts predicted malnutrition in HD and PD patients. These results suggest that GNRI and SLCs (especially CD19 count) may be significant nutritional markers in these patients.  相似文献   
107.
108.
Suh JS  Cho J  Lee SH  Shin KH  Yang WI  Lee JH  Cho JH  Suh KJ  Lee YJ  Ryu KN 《Skeletal radiology》2000,29(12):680-689
Objective. To present the MR and angiographic findings of alveolar soft part sarcoma (ASPS). Design and patients. MR examinations (12 tumors of 10 patients) of ASPS performed at multiple hospitals were retrospectively reviewed. The tumors were found in the thigh (n=4), lower leg (n=4), femur (n=2, local metastasis), scalp (n=1) and arm (n=1). The MR signal characteristics including signal intensity, homogeneity and signal void of lesions and bony invasion including direct invasion or local metastasis were evaluated. Angiographic findings (n=4) and post-embolotherapy follow-up MR imaging (n=2) findings were also assessed. Results. Local bony metastasis was found in two cases. Seven tumors showed heterogeneous high signal intensity on T1- and T2-weighted images with good enhancement. One tumor had a very high signal on T1-weighted images. Eight tumors (67%) showed numerous signal voids in or near the tumors. All four angiographic studies showed numerous enlarged vessels, arteriovenous shunts and delayed washout. Two cases mimicked arteriovenous malformations on angiographic studies but MR images demonstrated solid soft tissue components as well as tortuous vessels. Conclusions. High signal on T1-weighted image and numerous signal voids are highly suggestive of ASPS, although they are not universal as has been suggested and arteriovenous malformation should be included in the differential diagnosis. Local bony metastases in ASPS were seen in two cases and should be carefully investigated. Received: 12 April 2000 Revision requested: 27 June 2000, 8 August 2000 Revision received: 2 August 2000, 21 August 2000 Accepted: 22 August 2000  相似文献   
109.
PURPOSE: To evaluate the effect of uterine fibroid embolization (UFE) on menstruation and ovarian function. METHODS: The authors performed an observational study of UFE for the treatment of symptomatic fibroids. All patients had regular predictable menses before intervention and none had clinical or laboratory findings of menopause. UFE was performed with use of standard methods with 355-700-microm-diameter polyvinyl alcohol (PVA) foam particles. The incidence of ovarian failure was calculated for women younger than 45 years and for those 45 years or older, based on retrospective stratification by age. The authors assessed statistical differences in ovarian failure between the two age groups with use of the X2 test. RESULTS: Sixty-six premenopausal women (age range, 30-55 years) underwent bilateral UFE and were followed for an average of 21 weeks (range, 12-77 weeks). In 56 of 66 (85%) patients, regular menses resumed after an average of 3.5 (range, 1-8) weeks. In 10 of 66 (15%) patients, regular menses did not resume. Clinical and biochemical findings consistent with ovarian failure and presumed menopause were seen in nine of 10 patients without resumption of menses (14% of total patients). Ovarian failure occurred in nine of 21 (43%) women older than 45 years and in none of the 45 women younger than 45 years (P < .05). There were no differences in presenting symptoms, amount of PVA used, or fibroid size between patients who did and did not resume menses. CONCLUSION: The majority of patients undergoing UFE will have resumption of menses, but the incidence of postprocedure ovarian failure is considerably higher than reported to date. Loss of menses induced by UFE is significantly more likely to occur in women older than 45 years.  相似文献   
110.
Comprehensive aortic root and valve repair (CARVAR) surgery using specially designed aortic rings was introduced as a new surgical technique for aortic valve disease. We present five consecutive cases of iatrogenic coronary ostial stenosis after CARVAR surgery in patients with aortic stenosis. The preoperative coronary angiography confirmed that all the patients had normal coronary arteries. They underwent aortic valvuloplasty by aortic leaflet extension and insertion of specially designed inner and outer rings at the level of the sinotubular junction. Within 6 months after surgery, all the patients complained of resting chest pain and dyspnea with changes of electrocardiography. Repeated coronary angiography demonstrated right coronary artery (RCA) ostial stenosis in one patient and left main (LM) ostial stenosis in the other four patients. Intravascular ultrasonography demonstrated severe ostial stenosis and extensive echogenic tissue in the extravascular area. Four patients with LM ostial disease successfully underwent coronary bypass graft surgery, and percutaneous coronary intervention with stenting was performed in one case of RCA ostial stenosis. Because the mechanism of this complication is not fully confirmed, more clinical study is required to confirm the safety issues of CARVAR surgery.  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