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   14487篇
  免费   916篇
  国内免费   244篇
耳鼻咽喉   307篇
儿科学   172篇
妇产科学   177篇
基础医学   2352篇
口腔科学   233篇
临床医学   1084篇
内科学   2915篇
皮肤病学   673篇
神经病学   1130篇
特种医学   1065篇
外科学   1864篇
综合类   68篇
一般理论   2篇
预防医学   474篇
眼科学   397篇
药学   1174篇
中国医学   187篇
肿瘤学   1373篇
  2024年   11篇
  2023年   125篇
  2022年   385篇
  2021年   540篇
  2020年   325篇
  2019年   444篇
  2018年   497篇
  2017年   404篇
  2016年   627篇
  2015年   869篇
  2014年   979篇
  2013年   1064篇
  2012年   1481篇
  2011年   1355篇
  2010年   917篇
  2009年   722篇
  2008年   794篇
  2007年   790篇
  2006年   684篇
  2005年   624篇
  2004年   449篇
  2003年   381篇
  2002年   347篇
  2001年   100篇
  2000年   63篇
  1999年   64篇
  1998年   78篇
  1997年   69篇
  1996年   53篇
  1995年   51篇
  1994年   31篇
  1993年   32篇
  1992年   27篇
  1991年   22篇
  1990年   27篇
  1989年   25篇
  1988年   26篇
  1987年   33篇
  1986年   14篇
  1985年   10篇
  1984年   15篇
  1983年   8篇
  1982年   10篇
  1981年   12篇
  1980年   9篇
  1979年   5篇
  1978年   8篇
  1977年   8篇
  1973年   5篇
  1967年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
p53 and p21 genetic polymorphisms and susceptibility to endometrial cancer   总被引:5,自引:0,他引:5  
OBJECTIVE: Recently, there has been considerable interest in the association of specific cancers with single nucleotide polymorphisms (SNPs). In this regard, genetic polymorphism at codon 72 (CCC/proline to CGC/arginine [Pro(72)Arg]) of the p53 gene is one of the most frequently studied subjects. An association between endometrial cancer and the polymorphism at codon 31 (AGC/serine to AGA/arginine [Ser(31)Arg]) of the p21 gene, which is known to be a downstream mediator of p53, has also been reported. METHODS: The authors designed a hospital-based case-control study of 95 endometrial cancer patients and 285 non-cancer controls. For the determination of p53 and p21 polymorphism, allele-specific polymerase chain reaction (PCR) and PCR-restriction fragment length polymorphism assay was applied, respectively. RESULTS: We found statistically significant differences in the frequency of the p53 and p21 genotypes between these two groups (P < 0.001), respectively. The p53 genotypes containing the Pro allele were significantly associated with endometrial cancer with an odds ratio (OR) of 3.56 (95% confidence interval [CI] 2.10-6.04). Also, homozygous carriers of the p21 Ser allele showed a substantially increased risk of developing endometrial cancer (OR 2.68, 95% CI 1.59-4.51) as compared to homozygous and heterozygous carriers of the Arg allele. In addition, the combination of the pro allele containing genotypes of p53 and the Ser homozygous genotype of p21 posed a remarkably increased risk (OR 9.55, 95% CI 4.30-21.24) of endometrial cancer development. These significant differences were maintained throughout the groups after they were stratified by menopausal status. CONCLUSIONS: These data suggest that there is a significant association between the genetic polymorphisms of p53, p21, and specific combinations of the at-risk genotypes of these genes and the risk of developing endometrial cancer in Korean women.  相似文献   
992.
OBJECTIVES: The aim of this study was to determine whether GSTM1 or GSTT1 might be associated with risk of cervical cancer development in Korean women. The multiplicative interaction of GSTM1 and GSTT1 genotype with p21, p53 polymorphism, and HPV genotype was also investigated. METHODS: From 1997 to 1999, uterine cervical carcinoma was diagnosed in 215 Korean women at the Department of Obstetrics and Gynecology of Seoul National University Hospital. None of the women in the control groups (n = 98) had any evidence of cervical lesions, which were confirmed by Pap smear. Finally, 81 cases and 86 controls were genotyped for p21, p53, and GSTM1 and T1 and HPV infection. A multiplex PCR method was used for the genotyping of GSTM1 and GSTT1; direct sequencing for p53 codon 72, high-risk HPV, and PCR-RFLP (BsmAI) for p21 codon. The unconditional logistic regression analysis was used to calculate ORs and 95% CI. RESULTS: Although the GSTM1 and GSTT1 genotype was not significantly associated with cervical cancer development for all women, the GSTM1 null genotype was significantly associated with an increased risk of cervical cancer development in women with high-risk HPV infection (OR = 2.9, 95% CI: 1.0-8.2). Although the frequency of overall GSTT1 null genotype was significantly lower in cervical carcinoma patients with high-risk HPV infection (OR = 0.3, 95% CI: 0.1-1.0), almost 2-fold increased risk was observed among women with GSTT1 null and Arg/Arg genotype (OR = 1.9, 95% CI: 0.7-5.4). Although the cervical cancer risk was 3.3-fold increased in women with null and Arg/Arg genotype compared to women with GSTM1 present and p21 Ser-containing genotype, there was no significant multiplicative interaction between GSTM1 and p21 (P for interaction = 0.785) or p53 (P for interaction = 0.815). CONCLUSIONS: These findings suggest that the risk of cervical cancer may be related to GSTM1 genotype in women with high-risk HPV infection and that there is a possible gene-gene interaction in the incidence of cervical cancer.  相似文献   
993.
Kim TS  Sun K  Lee KB  Lee HW  Baek KJ  Park SY  Son HS  Kim KT  Kim HM 《Artificial organs》2004,28(12):1106-1109
Nonpulsatile blood pumps are mainly used in extracorporeal life support systems. Although pulsating blood flow is known to be physiological, a pulsatile pump is not commonly applied in a circuit with a membrane oxygenator because of damage to the blood cells. The hypothesis that the placement of a pressure-relieving compliance chamber in a circuit might reduce blood cell trauma was tested. An extracorporeal life support circuit was constructed in an acute lung injury model of dogs by oleic acid infusion. The animals were divided into three groups. In group I (n = 6) a nonpulsatile centrifugal pump was used as a control. In group II (n = 4) a single-pulsatile pump was used, and in group III (n = 6) a single-pulsatile pump equipped with a compliance chamber was used. Pump flow was maintained at 1.8-2.0 L/min for 2 h. Hemodynamics and blood gas analyses indicated that the pulsatile groups II and III had better results than the nonpulsatile group I. The plasma-free hemoglobin level, which indicates blood cell trauma, was the lowest in group I and the highest in group II but was significantly decreased in group III. A pressure-relieving compliance chamber could significantly reduce high circuit pressures and blood cell trauma.  相似文献   
994.
OBJECTIVE: The purpose of this study was to describe the CT and radiographic features of gastrointestinal stromal tumors of the duodenum. CONCLUSION: Gastrointestinal stromal tumors of the duodenum appear on barium studies as extrinsically compressing or submucosal masses with or without ulceration. These tumors usually appear on contrast-enhanced CT as well-defined masses with an exoenteric growth pattern and relatively good heterogeneous enhancement.  相似文献   
995.
OBJECTIVE: The purpose of this study was to evaluate whether mangafodipir trisodium (MnDPDP)-enhanced MRI improves the detection and characterization of small ( 2.0 cm). The differences between MnDPDP-enhanced MRI and helical CT with regard to the detection rates for hepatic lesions and metastases and with regard to the false-positive rates for hepatic metastases were analyzed using the McNemar test. The performances of MnDPDP-enhanced MRI and helical CT in indicating metastases of focal liver lesions were analyzed using receiver operating characteristic curves. RESULTS: No statistically significant differences were seen between MnDPDP-enhanced MRI and helical CT in the detection of all hepatic lesions (p = 0.383) and small lesions (p = 0.210). However, concerning the differentiation between benign and metastatic lesions, MnDPDP-enhanced MRI was superior to helical CT both for all hepatic lesions (p = 0.023) and for small lesions (p = 0.015), and remained better when the analyses were restricted to patients with histopathologic confirmation (p = 0.023 for both). MnDPDP-enhanced MRI changed the diagnosis of hepatic metastasis in nine (13.0%) of 69 patients. Of 12 metastases that were found on MnDPDP-enhanced MRI and missed on helical CT, 11 lesions (91.7%) were small. MnDPDP-enhanced MRI showed a significantly greater detection rate than helical CT for small hepatic metastases (p = 0.022). MnDPDP-enhanced MRI was better when the analyses were restricted to patients with histopathologic confirmation (p = 0.043). CONCLUSION: Although MnDPDP-enhanced MRI is equal to helical CT in detection of both all hepatic lesions and small lesions in patients with colorectal carcinoma, it is superior to CT in characterization of the lesions.  相似文献   
996.
OBJECTIVE: Although it is a rare condition, pigmented villonodular synovitis (PVNS) may involve temporomandibular joint (TMJ). The purpose of this study was to describe magnetic resonance (MR) findings of PVNS of the TMJ. METHODS AND MATERIAL: Between April 1992 and August 2000, four patients (two men and two women, 22-58-year-old) who had histologically proven diagnoses of PVNS in their TMJ were found in our institution. Their MR findings were reviewed retrospectively, and were correlated with pathologic findings. RESULTS: In all four patients, MR images invariably showed profound hypointensity on both T1- and T2-weighted sequences. This finding was seen diffusely and homogeneously throughout the lesion, and was considered to be due to paramagnetic effect attributed to heavy hemosiderin pigmentation, which was revealed by histopathological examination. MR images also showed aggressive nature of the lesions with adjacent skull base destruction and intracranial extension in two of them. CONCLUSION: As is the case in the other anatomic site, PVNS of the TMJ can be confidently diagnosed on MR imaging on the basis of the presence of hemosiderin. MR imaging also plays a pivotal role in surgical planning by precise and detailed localization of the lesion.  相似文献   
997.
PURPOSE: To evaluate the efficacy of percutaneous image-guided sclerotherapy of lymphangiomas with use of acetic acid. MATERIALS AND METHODS: Twelve patients with lymphangiomas were treated with acetic acid as the sclerosant. There were eight male patients and four female patients, ranging in age from 1 to 29 years (mean, 11 years). The lymphangiomas were located at the neck (n = 5), upper extremity (n = 3), axilla (n = 1), cervicomediastinum (n = 1), anterior chest wall (n = 1), and retroperitoneum (n = 1). Two patients had recurrent lymphangiomas after surgery and two patients had undergone failed sclerotherapy with another sclerosant. The acetic acid used as the sclerosant was 40%-50% in concentration, and the amounts used ranged from 2 mL to 70 mL (mean, 11.3 mL), which was equivalent to 4.6%-50% (mean, 30.6%) of the aspirated lymphatics. All procedures were performed under ultrasonographic and fluoroscopic guidance. The sclerosant was removed after sclerotherapy. All patients except one underwent one treatment session. RESULTS: Complete resolution of the lymphangioma was achieved in eight patients (66.7%), good resolution (>50% reduction) was achieved in three (25.0%), and poor resolution (<50% reduction) was seen in one (8.3%). Complications encountered included pneumonitis adjacent to the lymphangioma (n = 1), pain (n = 2), hematuria (n = 1), and tingling sensation in the forearm (n = 1). CONCLUSION: Percutaneous sclerotherapy of the lymphangiomas with use of acetic acid is an effective method without serious complications.  相似文献   
998.
The aim of this study was to evaluate the role of osteopontin (OPN) in cyclosporine (CsA) nephrotoxicity of the human kidney. Renal biopsy samples obtained before and after 1–2 years of CsA treatment were evaluated in 18 children (2.2–13.0 years, 14 males, 4 females) diagnosed with minimal change nephrotic syndrome. The changes in tubular OPN expression between pre- and post-treatment samples were correlated with interstitial macrophage infiltration, transforming growth factor- (TGF-) expression, interstitial fibrosis, and microvascular density. OPN, TGF-, CD68, and CD34 positivity were quantitatively assessed by immunohistochemical staining. Light microscopy showed that interstitial fibrosis developed in two-thirds of patients after CsA treatment. However, CD68-positive macrophages infiltrated minimally in fibrotic areas and were found in only one-third of patients. OPN expression was significantly increased in the glomerular mesangium (P=0.001) and tubules (P=0.025) after CsA treatment, whereas the number of CD34-positive peritubular capillaries decreased (P=0.022). An inverse relationship was observed between tubular OPN expression and microvascular density (r=–0.644). However, tubular OPN expression was not related to proteinuria, interstitial fibrosis, or interstitial or tubular TGF- expression. This study indicates that increased OPN expression may be related to microvascular injury in human CsA nephrotoxicity. It also shows that OPN expression may be used as an early but non-specific marker of CsA toxicity before the manifestation of interstitial fibrosis.  相似文献   
999.
Introduction Adduction of the ipsilateral hip joint is necessary to facilitate closed hip nailing for trochanteric fracture. Even though positioning the patient supine with the perineal post against the ipsilateral medial thigh can change the course of the neurovascular structure in the proximal thigh, there have been no reports regarding the position of the femoral artery in the hip nailing position.Materials and methods We studied the position of the superficial femoral artery in 59 thighs using color-flow duplex scanning method in three hip nailing positions.Results The mean of the distance between the superficial femoral artery and the femur in 48 normal limbs was 20.28 mm in neutral position (D1), 11.85 mm in 20o adduction (D2), and 9.53 mm in 20o adduction plus 20o internal rotation of the foot plate (D3). The distances D2 and D3 were always shorter than D1 (p<0.001). D3 was less than 10 mm in 30 of the normal limbs (62.5%) and less than 5 mm in 4 (8%). In 11 patients who sustained a trochanteric fracture, the mean of D1, D2, and D3 in the injured limbs was 25.28 mm, 17.98 mm, and 14.38 mm, respectively. The mid-thigh circumference and D3 of the injured limbs were always greater than those of the normal limbs (p<0.001). However, D3 of both sides was less than 10 mm in 3 patients.Conclusion To lessen the vascular injury during hip nailing, we recommend that the limb be placed in neutral position during preparation of the interlocking holes.  相似文献   
1000.
Delayed hemorrhage after pancreaticoduodenectomy   总被引:11,自引:0,他引:11  
BACKGROUND: Postoperative hemorrhage, particularly delayed hemorrhage after pancreaticoduodenectomy, is a serious complication and one of the most common causes of mortality after pancreaticoduodenectomy. STUDY DESIGN: The medical records of 500 patients who underwent pancreaticoduodenectomy between October 1994 and December 2002 were analyzed with regard to postoperative hemorrhagic complications. Delayed hemorrhage was defined as bleeding at the operation site after 5 or more postoperative days. RESULTS: Delayed hemorrhage occurred in 22 patients (4.4%), with a median time of 13 days (range 7 to 32 days) after pancreaticoduodenectomy, and developed more frequently (9/77 versus 13/423, p = 0.003) in patients with preceding intraabdominal complications such as pancreatic fistula, bile fistula, and intraabdominal abscess. In 17 of these 22 patients, angiography and laparotomy revealed bleeding foci at 14 arterial and 3 anastomotic sites. In nine patients, hemorrhage developed from pseudoaneurysms of the major arteries around the pancreaticojejunostomy. Hemostatis was attempted by transcatheter arterial embolization in 14 patients and with laparotomy in 4 patients. Four of 14 patients who received transcatheter arterial embolization eventually required laparotomy. Overall, 4 of the 22 delayed hemorrhage patients died (18.2%) of complications related to massive bleeding or transcatheter arterial embolization. CONCLUSIONS: Delayed hemorrhage after pancreaticoduodenectomy is associated with a high mortality. Intraabdominal complications after pancreaticoduodenectomy should be evaluated properly and guidelines for the diagnosis and treatment of delayed hemorrhage should be established in advance. Clinicians must be alert to the possibility of pseudoaneurysm hemorrhage.  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