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   2257篇
  免费   123篇
  国内免费   40篇
耳鼻咽喉   8篇
儿科学   20篇
妇产科学   13篇
基础医学   253篇
口腔科学   20篇
临床医学   127篇
内科学   830篇
皮肤病学   55篇
神经病学   134篇
特种医学   104篇
外科学   382篇
综合类   3篇
预防医学   27篇
眼科学   61篇
药学   106篇
中国医学   7篇
肿瘤学   270篇
  2023年   17篇
  2022年   23篇
  2021年   40篇
  2020年   40篇
  2019年   60篇
  2018年   59篇
  2017年   52篇
  2016年   61篇
  2015年   62篇
  2014年   78篇
  2013年   101篇
  2012年   145篇
  2011年   151篇
  2010年   111篇
  2009年   81篇
  2008年   156篇
  2007年   138篇
  2006年   159篇
  2005年   166篇
  2004年   147篇
  2003年   130篇
  2002年   120篇
  2001年   21篇
  2000年   19篇
  1999年   20篇
  1998年   28篇
  1997年   33篇
  1996年   29篇
  1995年   19篇
  1994年   20篇
  1993年   23篇
  1992年   16篇
  1991年   21篇
  1990年   13篇
  1989年   6篇
  1988年   8篇
  1987年   5篇
  1986年   7篇
  1984年   6篇
  1983年   4篇
  1982年   4篇
  1981年   7篇
  1980年   2篇
  1979年   3篇
  1978年   1篇
  1976年   1篇
  1975年   2篇
  1974年   1篇
  1970年   1篇
  1964年   1篇
排序方式: 共有2420条查询结果,搜索用时 15 毫秒
91.
Recent reports have raised concerns over the feasibility of differentiating bone marrow cells (BMCs) into functional hepatocytes. Such augmentation is considered necessary for potential clinical use of these cells in liver diseases. The present investigation was designed to determine the kinetics of transplanted BMCs and evaluate the effects of repeated bone marrow transplantation (BMT) in rat models of CCl(4)-induced liver damage. The early kinetics of transplanted BMCs was evaluated with a charge-coupled-device (CCD) camera using BMCs obtained from green fluorescent protein (GFP) transgenic (Tg) rats and followed up with in vivo imaging system (IVIS) using BMCs obtained from firefly luciferase (luc) Tg rats. We used a portal infusion system for repeated BMT. BMCs were transplanted via a peripheral vein or the portal vein (PV) once or repeatedly using this system. The results revealed that BMCs accumulated more in the damaged liver than in the intact liver. In the experimental group receiving repeated BMT via the PV, the liver fibrosis was milder than that in the group not receiving BMT, and large clusters of albumin-producing cells were detected by albumin staining. The injected BMCs were shown to accumulate in the damaged liver. This strategy of repeated BMT has potential clinical use in enhancing the number of albumin-producing cells and suppressing liver fibrosis. This combination of beneficial effects may contribute to the benefits of cell transplantation therapy. Demonstration of the benefits of BMT in this study may be expected to have great significance for clinical trials.  相似文献   
92.
93.
BackgroundSevere chondral lesions and varus knee alignment are associated with poor outcomes following transtibial pullout repair for medial meniscus posterior root tears and meniscus tear is strongly associated with body mass index. The prognostic factors in well-aligned knees (femorotibial angle < 180°) with mild chondral lesions are unknown. Therefore, we investigated the prognostic factors in these patients. We hypothesized that high body mass index would lead to poor clinical outcomes following pullout repair of medial meniscus posterior root tears.MethodsWe retrospectively reviewed the files of 28 patients who had undergone pullout repair of medial meniscus posterior root tears between October 2016 and December 2017. We recorded the baseline characteristics (age, gender, height, weight, and body mass index) and the time between injury and surgery. We recorded the International Knee Documentation Committee scores, Knee injury and Osteoarthritis Outcome Scores, and pain visual analog scale scores. Using magnetic resonance imaging preoperatively and 1 year after surgery, we measured the medial meniscus body width and absolute and relative medial meniscus extrusion. Pearson correlation and multivariate linear regression analyses were used to assess potential associations between these factors and clinical outcomes.ResultsAge positively correlated (coefficient = 0.49, P < 0.01) and body mass index negatively correlated with the postoperative International Knee Documentation Committee score (coefficient = ?0.64, P < 0.01). In multivariate linear regression analysis, body mass index was a significant factor leading to poor postoperative International Knee Documentation Committee score (R2 = 0.29, P < 0.05).ConclusionsBody mass index > 30 kg/m2 is a risk factor for unfavorable clinical outcomes following pullout repair of medial meniscus posterior root tears in well-aligned knees.Level of evidenceIII, Comparative retrospective study.  相似文献   
94.
Purpose To determine whether fibril length is correlated with graft healing as well as cellular and capillary ingrowth in a canine carotid implantation model.Methods Expanded polytetrafluoroethylene (ePTFE) vascular grafts with three different fibril lengths (30, 60, and 90µm) were implanted into the carotid artery in dogs. They were retrieved 4 weeks later, and subjected to histomorphometric analysis.Results Endothelial healing was best in the 60-µm grafts. Not only cellular ingrowth but also capillary ingrowth was most evident in the 60-µm grafts, followed by the 90-µm grafts and then the 30-µm grafts.Conclusion Better endothelial healing of ePTFE vascular grafts is correlated with more cellular and capillary ingrowth, but more cellular and capillary ingrowth is not correlated with longer fibril length or higher air porosity.  相似文献   
95.
Groove pancreatic carcinomas: radiological and pathological findings   总被引:4,自引:0,他引:4  
The aim of this study was to clarify the characteristics of pancreatic head carcinomas mainly invading the groove between the duodenum and the pancreatic head. Nine patients with pathologically proven pancreatic head carcinomas underwent thin-slice dynamic CT, MR imaging, duodenal endoscopy, and angiography (seven patients). Plate-like masses within the groove region were seen in all cases, which showed hypointensity on T1-weighted images and slight hyperintensity on T2-weighted MR images. The masses appeared hypovascular in the early phase and delayed enhancement in the late phase of dynamic CT and MR imaging. On MR cholangiopancreatography, stenosis of intrapancreatic common bile duct was seen in all patients, whereas stenosis of the main pancreatic duct was seen in only three cases. Endoscopy revealed luminal narrowing of the duodenum in all patients, and duodenal mucosal biopsy demonstrated adenocarcinoma in seven patients. Abdominal arteriography showed serrated encasement of peripancreatic arteries in seven patients who received angiographic examinations. The CT and MR imaging findings of groove pancreatic carcinomas resemble those of groove pancreatitis. Differential diagnosis may be achieved by the pathological diagnosis of a biopsy specimen of the duodenal mucosa and arterial encasement on arteriography.  相似文献   
96.
PURPOSE: To analyze local recurrence-free rates and risk factors for recurrence following percutaneous radiofrequency ablation (RFA) or transcatheter arterial chemoembolization (TACE) for hypervascular hepatocellular carcinoma (HCC). METHODS: One hundred and nine nodules treated by RFA and 173 nodules treated by TACE were included. Hypovascular nodules were excluded from this study. Overall local recurrence-free rates of each treatment group were calculated using the Kaplan-Meier method. The independent risk factors of local recurrence and the hazard ratios were analyzed using Cox's proportional-hazards regression model. Based on the results of multivariate analyses, we classified HCC nodules into four subgroups: central nodules < or =2 cm or >2 cm and peripheral nodules < or =2 cm or >2 cm. The local recurrence-free rates of these subgroups for each treatment were also calculated. RESULTS: The overall local recurrence-free rate was significantly higher in the RFA group than in the TACE group (p = 0.013). The 24-month local recurrence-free rates in the RFA and TACE groups were 60.0% and 48.9%, respectively. In the RFA group, the only significant risk factor for recurrence was tumor size >2 cm in greatest dimension. In the TACE group, a central location was the only significant risk factor for recurrence. In central nodules that were < or =2 cm, the local recurrence-free rate was significantly higher in the RFA group than in the TACE group (p < 0.001). In the remaining three groups, there was no significant difference in local recurrence-free rate between the two treatment methods. CONCLUSION: A tumor diameter of >2 cm was the only independent risk factor for local recurrence in RFA treatment, and a central location was the only independent risk factor in TACE treatment. Central lesions measuring < or =2 cm should be treated by RFA.  相似文献   
97.
BACKGROUND: The relationship between ascites, as detected by preoperative computed tomography (CT), and peritoneal metastasis of gastric cancer requires clarification because of its likely significance for clinical outcome. METHODS: A retrospective analysis of 293 patients with advanced gastric cancer investigated the association between preoperative CT findings of ascites and surgical findings of peritoneal washing cytology and peritoneal metastasis. RESULTS: Forty-five of 293 patients (15%) presented with ascites on preoperative CT. Positive ascites on CT predicted the presence of free tumor cells with 40% sensitivity and 97% specificity, and peritoneal metastasis with 51% sensitivity and 97% specificity. Ascites on CT was an independent prognostic factor by univariate (P < .001) and multivariate (relative risk, 2.03; 95% confidence interval, 1.39-2.96; P < .001) analyses. The median survival time was 6.0 months in patients with positive ascites on CT. CONCLUSIONS: The presence of ascites on CT suggests the presence of peritoneal metastasis and indicates a poor prognosis. The presence of peritoneal metastasis should be confirmed by diagnostic laparoscopy in gastric cancer patients with ascites.  相似文献   
98.

Background

Radiation therapy (RT) is the common treatment for painful vertebral bone metastases without paralysis by malignant spinal cord compression. However, no studies have focused on the time course of pain after RT. Then, we investigated the change of pain after RT for painful vertebral bone metastases without paralysis.

Methods

Participants included 101 patients who received RT for painful vertebral bone metastases without paralysis in our institution between 2012 and 2016. All patients received RT and pain response was evaluated by Numeric Rating Scale (NRS). Follow-up assessments were performed just before the start of RT and every month for six months after RT. Pain response was classified as complete response (CR), partial response (PR), pain progression (PP), and indeterminate response (IR) based on the response criteria of International Bone Metastases Consensus Working Party. Responders were classified as either CR or PR, and non-responders as either PP or IR.

Results

Median NRS scores for pain were 5 before RT, decreasing to 0 by one month after RT and remaining zero until last follow-up, representing a significant decrease over time (P < 0.001). The rate of responders at each month from one to six months was 93, 96, 95, 100, 98, and 96%, respectively. Multivariate analysis revealed that Spinal Instability Neoplastic Score (SINS) was the only risk factor for response to RT at one month. At one month pain disappeared in 88% of the patients with spinal stability (SINS < 7), although pain disappeared 58% of the patients with spinal instability (SINS ≥ 7), which was significant (P = 0.002).

Conclusions

Pain decreased significantly over time and 93% of patients were classified as responders as early as one month after RT in patients with painful vertebral bone metastases without paralysis. Pretreatment SINS could be a predictor of pain response to RT.  相似文献   
99.
The infrapatellar fat pad (IFP) contains nerve fiber endings and is considered to play an important role in the perception of knee pain. However, it is unclear whether and to what degree prolonged pain influences the nociceptive role of the IFP. To answer this question, we established a novel rat model of knee pain in which inflammation is restricted to the IFP. Rats received a single intra-IFP injection of monoiodoacetic acid (MIA) (0.2 mg/10 µL or 1.0 mg/10 µL) in the left knee and a phosphate-buffered saline (10 µL) injection in the right knee as a control. Pain-avoidance behavior and histological changes of the knee joint were measured at multiple time points up to 28 days after MIA injection. Histological analysis showed a transient inflammatory response in the IFP body in the 0.2-mg model, whereas prolonged inflammation followed by fibrotic changes was observed in the 1.0-mg model. Subtle histological alterations were observed in the articular cartilage and IFP surface regardless of the dose. The pain-avoidance behavior test indicated the development of prolonged knee pain throughout the experimental period in the 1.0-mg group. Histological assessments showed a significant increase in calcitonin gene-related peptide (CGRP)-positive nerve fiber endings inside IFPs with fibrosis in newly vascularized surrounding regions. These data suggest that irreversible fibrotic changes in the IFP induce the formation of new vessels and CGRP-positive nerve fiber endings that associate prolonged pain in the joint.  相似文献   
100.

Background

A complete discoid lateral meniscus (DLM) has a high risk of horizontal tear. However, cellular phenotypes and extracellular matrix organizations in complete DLMs are still unclear. The aim of this study was to investigate histological and cellular biological characteristics in both the intercondylar and central regions of complete DLM.

Materials and methods

Meniscal samples were obtained from the intercondylar and central regions of complete DLM (n = 6). Blood vessels and aggregated cell ratio were measured in each region. Depositions of type I/II collagens and safranin O-stained proteoglycans in the extracellular matrix were assessed. Experiments in gene expression, morphology, proliferation, and effect of mechanical stretch were performed using cultured cells derived from each region.

Results

Blood vessel counts were significantly higher in the intercondylar region than in the central region. The ratio of aggregated cells was lower in the intercondylar region than in the central region. Deposition of type I collagen was comparable for both regions. The central region contained a larger quantity of type II collagen and safranin O staining density compared with the intercondylar region. Proliferation of the fibroblastic intercondylar cells was not affected by 5%-stretching. However, stretching treatments decreased relative proliferation of the chondrocytic central cells.

Conclusions

This study demonstrated that the central region of complete DLM had different cellular properties and collagen components compared with the intercondylar region. Our results suggest that the central region of complete DLM may have a low healing potential like the inner avascular region of the meniscus.  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