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   5160篇
  免费   256篇
  国内免费   180篇
耳鼻咽喉   94篇
儿科学   37篇
妇产科学   48篇
基础医学   866篇
口腔科学   108篇
临床医学   567篇
内科学   995篇
皮肤病学   111篇
神经病学   455篇
特种医学   325篇
外科学   713篇
综合类   41篇
预防医学   205篇
眼科学   56篇
药学   504篇
中国医学   76篇
肿瘤学   395篇
  2024年   2篇
  2023年   45篇
  2022年   169篇
  2021年   241篇
  2020年   109篇
  2019年   121篇
  2018年   152篇
  2017年   122篇
  2016年   192篇
  2015年   336篇
  2014年   345篇
  2013年   386篇
  2012年   562篇
  2011年   535篇
  2010年   260篇
  2009年   242篇
  2008年   326篇
  2007年   345篇
  2006年   235篇
  2005年   174篇
  2004年   109篇
  2003年   99篇
  2002年   89篇
  2001年   83篇
  2000年   75篇
  1999年   48篇
  1998年   37篇
  1997年   29篇
  1996年   19篇
  1995年   15篇
  1994年   10篇
  1993年   14篇
  1992年   18篇
  1991年   6篇
  1990年   6篇
  1989年   14篇
  1988年   8篇
  1987年   7篇
  1986年   2篇
  1985年   4篇
  1984年   2篇
  1983年   1篇
  1980年   1篇
  1977年   1篇
排序方式: 共有5596条查询结果,搜索用时 0 毫秒
21.
End-stage renal disease (ESRD) caused by diabetic nephropathy is increasing throughout the world. The survival of diabetic patients treated by transplantation has improved nowadays. Although recent studies have demonstrated preemptive kidney transplantation to be associated with better graft survival in CKD patients, the effect of pre-transplantation dialysis on graft outcomes among diabetic ESRD patients is unclear. This analysis summarized our experience with preemptive kidney transplantation in diabetic ESRD patients by retrospectively comparing 70 such patients transplanted between 1995 and 2009. These 70 patients were divided into two groups: 30 patients underwent preemptive and the other 40 transplantation after maintenance hemodialysis or peritoneal dialysis. We compared graft survivals, acute rejection episodes, postoperative complications, and delayed graft function rates. The 10-year patient survival of 100% in the preemptive group was similar to that of the nonpreemptive group (85%, P = .11). But the 10 year graft survival was higher among the preemptive than the nonpreemptive group (100% vs 75%, P = .02). Pre-transplantation modality did not affect graft survival. Therefore, preemptive kidney transplantation should be applied to eligible patients with diabetic ESRD.  相似文献   
22.

Objective  

We compared the electrode positions of subthalamic nucleus (STN) deep brain stimulation (DBS) estimated at the immediate postoperative period with those estimated 6 months after surgery.  相似文献   
23.

Background

Few studies assessing the functional change of each kidney following warm ischaemia after partial nephrectomy are available.

Objectives

Our aim was to identify the effects of the warm ischaemic time (WIT) on renal function after partial nephrectomy under the pneumoperitoneum.

Design, setting, and participants

Forty-four consecutive patients who underwent laparoscopic partial nephrectomy (LPN) or robot-assisted partial nephrectomy (RAPN) from June 2008 to May 2009 for a single cT1 renal tumour were included in this prospective protocol.

Measurements

Technetium Tc 99m-diethylenetriaminepentaacetic acid (Tc 99m-DTPA) renal scintigraphy was used to determine the glomerular filtration rate (GFR) of both kidneys and each kidney individually. Tc 99m-DTPA GFR was performed preoperatively and 3 mo postoperatively. In addition, we analysed Tc 99m-DTPA scintigraphy GFR regionally in the healthy areas of the affected kidney.

Results and limitations

Patients with WIT >28 min had a significantly greater decrease in the GFR of the affected kidney (p = 0.031). The GFR of the affected kidney showed a significant decrease perioperatively (46.4 ± 14.3 to 37.9 ± 11.9 ml/min per 1.73 m2; p = 0.003). The functional change of the nonaffected kidney showed an increasing trend (47.5 ± 13.8 to 51.4 ± 14.3 ml/min per 1.73 m2), although it was not statistically significant (p = 0.103). Regional Tc 99m-DTPA GFR of both affected kidney and nonaffected kidney showed no significant differences perioperatively (6.3 ± 1.8 to 6.1 ± 1.9 ml/min per 1.73 m2; p = 0.641; 6.6 ± 1.9 to 7.1 ± 2.0 ml/min per 1.73 m2; p = 0.200). On multivariate analysis, preoperative GFR, resected volume of marginal healthy tissue, and WIT were independent predictors for functional reduction of the affected kidney (p < 0.05). The study was limited by small numbers and short follow-up periods.

Conclusions

Stationary overall renal function after LPN or RAPN is masked possibly by functional compensation of the contralateral healthy kidney. The damage of the affected kidney estimated by scintigraphy occurs when WIT exceeds 28 min during partial nephrectomy under the pneumoperitoneum.  相似文献   
24.

Introduction  

Prediction of lymph node metastasis in early gastric cancer (EGC) is very important to decide treatment strategies preoperatively. The aim of this study was to evaluate factors that predict the presence of lymph node metastasis and to indentify the differences between mucosal and submucosal gastric cancers.  相似文献   
25.

Objective:

This study aims to analyze the clinical characteristics and diagnostic features of ovarian fibromas and to evaluate the efficacy and safety of laparoscopic surgery for ovarian fibromas.

Methods:

We reviewed the records of 47 consecutive women who underwent laparoscopic or laparotomic surgeries and whose final histopathological diagnoses were ovarian fibroma, cellular fibroma, or fibrothecoma from January 1999 to August 2010.

Results:

During the study period, 49 tumors were removed from 47 women including 27 ovarian fibromas, 19 fibrothecomas, and 3 cellular fibromas. The preoperative diagnoses were ovarian fibroma in 25 women (53.2%) and uterine myoma in 16 women (34.0%). A high serum CA 125 level (>35U/mL) was observed in 15 women, and serum CA 125 level was significantly higher in women with ascites (P=<0.001). The tumors were removed surgically in all women, using the laparotomic approach in 16 women (34.0%) and the laparoscopic approach in 31 women (66.0%). The laparoscopic surgery had the advantages of shorter hospital stay and faster return of bowel activities compared to laparotomy.

Conclusions:

Ovarian fibromas are often misdiagnosed as uterine myomas, and sometimes mistaken for a malignant tumor of the ovary preoperatively. Laparoscopic surgery can be an effective and safe surgical approach for managing ovarian fibromas.  相似文献   
26.
Background We assessed whether new parameter that considers both tumor volume change and necrosis rate predicts metastasis-free survival of localized osteosarcoma patients. We also evaluated relationship between tumor volume change and necrosis rate or metastasis-free survival. Methods We retrospectively reviewed 151 patients with stage II osteosarcoma who were treated with surgery and neoadjuvant chemotherapy. The tumor volume change was measured and calculated based on pre- and postchemotherapy magnetic resonance images. The mean metastasis-free interval was 83.1 months. We calculated adjusted tumor necrosis rate as following formula: 100–(100–necrosis rate) × postchemotherapy/prechemotherapy tumor volume. Survival and logistic regression analyses were used to evaluate the correlation among size parameters, tumor necrosis rate and survival. Results The 5-year metastasis-free survival rate of 151 patients was 71.4% (95% CI, 67.7–75.1%). American Joint Committee on Cancer (AJCC) stage IIB (RR 2.27; 95% CI, 1.11–4.62; P = 0.025) and poor adjusted tumor necrosis rate (RR 2.02; 95% CI, 1.05–3.89; P = 0.035) independently correlated with metastasis-free survival period. Further, tumor volume change independently correlated with necrosis rate. Decreased tumor volume could predict good response, with sensitivity of 80.2%, specificity of 68.6%, and positive predictive value (PPV) of 74.7%. Increased or stable tumor volume could predict poor response, with sensitivity of 68.6%, specificity of 80.2%, and PPV of 75.0 %. Conclusion The necrosis rate adjusted by the tumor volume change is an independent prognostic factor in osteosarcoma. This adjusted tumor necrosis rate may serve as a basis for risk-adapted therapy in combination with other prognostic factors.  相似文献   
27.
BACKGROUND CONTEXT: A relationship between degenerative changes of the intervertebral disc and biomechanical functions of the lumbar spine has been suggested. However, the exact relationship between the grade of disc degeneration and the flexibility of the motion segment is not known. PURPOSE: To investigate the relationship between degenerative grades of the intervertebral disc and three-dimensional (3-D) biomechanical characteristics of the motion segment under multidirectional loading conditions. STUDY DESIGN/SETTING: A biomechanical and imaging study of human cadaveric spinal motion segments. METHODS: One hundred fourteen lumbar motion segments from T12-L1 to L5-S1 taken from 47 fresh cadaver spines (average age at death, 68 years; range, 39 to 87 years) were used in this study. The severity of degeneration (grades I to V according to Thomson's system) was determined using magnetic resonance (MR) images and cryomicrotome sections. Pure unconstrained moments with dead weights were applied to the motion segments in six load steps. The directions of loading included flexion, extension, right and left axial rotation, and right and left lateral bending. RESULTS: When the MR images were graded, 2 segments had grade I disc degeneration; 45, grade II; 20, grade III; 26, grade IV; and 21, grade V. When the cryomicrotome sections were graded, 14 segments had grade I disc degeneration; 31, grade II; 22, grade III; 26, grade IV; and 21, grade V. Segments from the upper lumbar levels (T12-L1 to L3-4) tended to have greater rotational movement in flexion, extension, and axial rotation with disc degeneration up to grade IV, whereas the motion decreased when the disc degenerated to grade V. In the lower lumbar spine at L4-5 and L5-S1, motion in axial rotation and lateral bending was increased in grade III. CONCLUSIONS: These results suggest that kinematic properties of the lumbar spine are related to disc degeneration. Greater motion generally was found with disc degeneration, particularly in grades III and IV, in which radial tears of the annulus fibrosus are found. Disc space collapse and osteophyte formation as found in grade V resulted in stabilization of the motion segments.  相似文献   
28.
Jeon DH  Oh K  Oh BC  Nam DH  Kim CH  Park HB  Cho J  Lee JR  Lee DS  Lee G 《Xenotransplantation》2007,14(3):236-242
BACKGROUND: Effective intervention achieved by manipulating cell-mediated xenogeneic immune responses would critically increase the clinical feasibility of xenotransplantation as immediate hyperacute rejections become controllable through genetic modulations of donor organs. Endogenous negative regulatory signals like the programmed death 1 (PD-1)-programmed death ligand 1 (PD-L1) system are candidate targets for the control of cell-mediated xenogeneic immune response. METHODS: A porcine PD-L1 molecule was cloned using RACE (rapid amplification of cDNA ends) technology based on the human PD-L1 sequence. The functional effects of cloned porcine PD-L1 were tested on human CD4(+) T cell activation using porcine PD-L1-transfected bystander cells. Cellular proliferation was monitored by [3H] thymidine incorporation, and human T cell apoptosis was measured by flow cytometry. RESULTS: Porcine PD-L1 (GenBank accession number AY837780) was found to have 73.8% sequence homology with human PD-L1 and to contain two immunoglobulin domains in its extracellular region. Moreover, porcine PD-L1 expressed on Chinese hamster ovary (CHO) cells inhibited human CD4(+) T cell proliferation stimulated with anti-CD3 only or anti-CD3 plus anti-CD28. Percentages of apoptotic activated human T cells increased by over 30% in the presence of porcine PD-L1/CHO cells, and the addition of recombinant human PD-1-Fc fusion proteins during human T cell activation reversed the inhibitory effects of porcine PD-L1. CONCLUSIONS: Cloned porcine PD-L1 showed high sequence homology with human PD-L1 and a similar molecular structure. Moreover, porcine PD-L1 inhibited human CD4(+) T cell activation in human PD-1-dependent manner, and this involved activated T cell apoptosis. The authors suggest that PD-1-PD-L1 might play an important endogenous immune regulatory role during xenogeneic transplantation, and that the effective application of this system would improve transplanted xenogeneic organ survival.  相似文献   
29.
BACKGROUND AND OBJECTIVES: This study examined the effect of lumbar flexion on the extent of the epidural block during lumbar epidural anesthesia. METHODS: The epidural catheter was introduced at the L3-4 interspace with the patient in the lateral decubitus position with the surgical side down. After administering a test drug (3 mL of 2% lidocaine and 15 mug of epinephrine), the patients were randomly allocated to 1 of 2 groups: Group F (n = 16, lumbar spine flexed) and Group N (n = 17, lumbar spine in the neutral position). In both groups, 2% lidocaine (16 mL) mixed with sodium bicarbonate (2 mL) was administered through the epidural catheter while the patient maintained the lateral decubitus position with the lumbar spine either flexed or in the neutral position. All the patients maintained their respective positions for 5 minutes and were subsequently turned to the supine position. The pinprick block level and the degree of motor blockade were assessed every 10 minutes for 60 minutes after administering the local anesthetics. A 2-dermatomal difference in uppermost block between groups was determined to be clinically significant. RESULTS: The median difference between groups in the uppermost pinprick block level was only 1.5 dermatomes and it did not satisfy our criteria for clinical significance. There were no significant differences between the 2 groups in the lowermost pinprick block level and the degree of motor block. CONCLUSIONS: Lumbar flexion has no clinically relevant effect on sensory spread during epidural anesthesia.  相似文献   
30.

Introduction

Various surgical treatments such as extension block pinning have been proposed for acute bony mallet finger. We evaluated the clinical results of tension wire fixation technique for the treatment of nonunion of mallet fracture after failed mallet finger surgery.

Materials and methods

Nine male patients were treated with open tension wire fixation for chronic nonunion of mallet fracture after extension block pinning surgery failed. The mean age was 29.3 years (range 18–47). We assessed bone union in simple radiographs. Crawford’s and Bischoff functional score was used to assess the functional outcome.

Results

The mean follow-up period was 45.8 months (range 18–74). Clinical and radiographic bone unions were achieved in eight of nine patients with average time of 31 days (range 23–41). Mean extension lag at final follow-up was 7° (range 0–25). Four patients showed excellent, three patients showed good and two patients showed fair results on the Crawford’s score scale. With Bischoff functional score, all patients were categorized as excellent.

Conclusions

Tension wire fixation can be a good second-line reconstructive surgery for the treatment of mallet fracture after extension block failed, so that patients can avoid arthrodesis or complex tendon transfer as a salvage procedure.  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