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   89487篇
  免费   8798篇
  国内免费   7290篇
耳鼻咽喉   653篇
儿科学   826篇
妇产科学   985篇
基础医学   10687篇
口腔科学   1597篇
临床医学   12968篇
内科学   13126篇
皮肤病学   722篇
神经病学   5294篇
特种医学   3157篇
外国民族医学   56篇
外科学   8287篇
综合类   15326篇
现状与发展   22篇
一般理论   13篇
预防医学   5795篇
眼科学   2945篇
药学   9235篇
  102篇
中国医学   5834篇
肿瘤学   7945篇
  2024年   313篇
  2023年   1522篇
  2022年   4288篇
  2021年   5182篇
  2020年   3938篇
  2019年   3223篇
  2018年   3425篇
  2017年   2871篇
  2016年   2820篇
  2015年   4291篇
  2014年   5277篇
  2013年   4459篇
  2012年   6559篇
  2011年   7604篇
  2010年   4565篇
  2009年   3580篇
  2008年   4581篇
  2007年   4443篇
  2006年   4622篇
  2005年   4648篇
  2004年   2736篇
  2003年   2662篇
  2002年   2220篇
  2001年   1935篇
  2000年   2057篇
  1999年   2159篇
  1998年   1442篇
  1997年   1366篇
  1996年   1099篇
  1995年   1016篇
  1994年   841篇
  1993年   533篇
  1992年   601篇
  1991年   509篇
  1990年   465篇
  1989年   420篇
  1988年   347篇
  1987年   296篇
  1986年   228篇
  1985年   178篇
  1984年   81篇
  1983年   50篇
  1982年   41篇
  1981年   36篇
  1980年   24篇
  1979年   21篇
  1964年   1篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
961.
962.

Purpose

Cystatin C has been proposed as a surrogate marker of kidney function. The elderly population accounts for the largest proportion of chronic kidney disease (CKD) patients. The aim of this study was to assess the diagnostic value of serum cystatin C and compare the applicability of cystatin C-based equations with serum creatinine (Scr)-based equations for estimating glomerular filtration rate (GFR).

Methods

The estimated GFR (eGFR) values from six cystatin C-based equations (Tan, MacIsaac, Ma, Stevens1-3) and three Scr-based equations (CG, MDRD, CKD-EPI) were compared with the reference GFR (rGFR) values from 99mTc-DTPA renal dynamic imaging method.

Results

A total of 110 elderly Chinese (60?C92?year, 71.05?±?7.62?year) were enrolled. Cystatin C had better diagnostic value than Scr (relationship coefficient with rGFR: cystatin C ?0.847 vs. Scr ?0.729, P?<?0.01; sensitivity: cystatin C 0.90 vs. Scr 0.55, P?<?0.01; AUCROC: cystatin C 0.857 vs. Scr 0.757, P?<?0.01). All the equations predicted GFR more accurately for rGFR????60?ml/min/1.73?m2 than for rGFR?<?60?ml/min/1.73?m2. Most equations had acceptable accuracy. The cystatin C-based equations deviated from rGFR by ?12.78?ml/min/1.73?m2 to ?2.12?ml/min/1.73?m2, with accuracy varying from 64.6 to 82.7?%. The Scr-based equations deviated from rGFR by ?5.37?ml/min/1.73?m2 to ?0.68?ml/min/1.73?m2, with accuracy varying from 77.3 to 79.1?%. The CKD-EPI, MacIsaac and Ma equations predicted no bias with rGFR (P?>?0.05), with higher accuracy and lower deviation in the total group. The MacIsaac, CKD-EPI and Stevens3 equations could be optimal for those with normal and mildly impaired kidney function, whereas the Ma equation for those with CKD.

Conclusion

Cystatin C is a promising kidney function marker. However, not all cystatin C-based equations could be superior to the Scr-equations.  相似文献   
963.
This study investigated the comparative ability of bone marrow and skeletal muscle derived stromal cells (BMSCs and SMSCs) to express a tenocyte phenotype, and whether this expression could be augmented by growth and differentiation factor‐5 (GDF‐5). Tissue harvest was performed on the hind limbs of seven dogs. Stromal cells were isolated via serial expansion in culture. After four passages, tenogenesis was induced using either ascorbic acid alone or in conjunction with GDF‐5. CD44, tenomodulin, collagen I, and collagen III expression levels were compared for each culture condition at 7 and 14 days following induction. Immunohistochemistry (IHC) was performed to evaluate cell morphology and production of tenomodulin and collagen I. SMSCs and BMSCs were successfully isolated in culture. Following tenocytic induction, SMSCs demonstrated an increased mean relative expression of tenomodulin, collagen I, and collagen III at 14 days. BMSCs only showed increased mean relative expression of collagen I, and collagen III at 14 days. IHC revealed positive staining for tenomodulin and collagen I at 14 days for both cell types. The morphology of skeletal muscle derived stromal cells at 14 days had an organized appearance in contrast to the haphazard arrangement of the bone marrow derived cells. GDF‐5 did not affect gene expression, cell staining, or cell morphology significantly. Stromal cells from either bone marrow or skeletal muscle can be induced to increase expression of matrix genes; however, based on expression of tenomodulin and cell culture morphology SMSCs may be a more ideal candidate for tenocytic differentiation. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1710–1718, 2012  相似文献   
964.
Objective: To explore the clinical characteristics of osteonecrosis of the femoral head (ONFH) induced by steroids. Methods: From January 2000 to October 2009, 497 hips in 270 cases of ONFH induced by steroids were studied. A questionnaire was administered when the patients were admitted; the questions concerned the underlying disease, duration of steroid usage, total dosage of steroid, incubation period (time interval between commencement of steroid therapy and onset of pain), severity of pain, location of initial complaint, primary diagnosis, time lag from onset of pain to final diagnosis and physical signs when admitted. The correlations between pain and Association Research Circulation Osseous (ARCO) stage, bone marrow edema (BME) and lesion size were analyzed. Results: The median of time between commencing steroid medication and developing ONFH for the 269 cases was 18 months (range, 2–384 months). 78.82% cases presented with pain within three years of steroid initiation, only 10.41% patients first complained of pain six or more years after commencing steroid therapy. Fifty‐six cases (20.82%) were misdiagnosed, lumbar disorders being the most frequent misdiagnoses. 79.29% of symptomatic hips presented with abnormal physical tests. Of 420 symptomatic hips, 166 hips were type C1, 223 hips type C2; 299 hips had collapsed; and there was BME in 209 hips. Conclusion: Most patients with ONFH induced by steroids complained of pain within 3 years of commencing steroid therapy. Pain was associated with lesion size, collapse and BME. Atypical location of pain, failure to perform a physical examination and MRI findings were the main causes of misdiagnoses.  相似文献   
965.
Objective: To determine the efficacy of imaging patients in a state of traction (“traction imaging”) for selection of upper and lower vertebrae to undergo instrumentation (UIV and LIV, respectively) to correct moderate to severe, rigid scoliosis. Methods: Twenty‐seven patients aged 11–21 years (average, 15.5 years) who had been treated at our institution for scoliosis of the thoracic spine between 2004 and 2008 were retrospectively analyzed. All patients were treated with the third multiple hook‐screw and rod instrumentation system. Standardized radiographic measurements (anteroposterior, sagittal, bending, fulcrum, traction) were taken and Cobb's angles, apical vertebra translation (AVT), and traction‐stable vertebrae determined. Results: All patients were followed for 6–36 months (average, 14.7 months). The Cobb's angles under preoperative vertical traction correlated positively with those measured postoperatively in standing anteroposterior film (P < 0.01). Preoperative AVT under vertical traction was significantly different from that measured postoperatively in standing anteroposterior film (P < 0.01). The traction radiography‐determined UIV slant angles were significantly different from those preoperatively without traction and the postoperative values, whereas traction radiography‐determined LIV values were not significantly different from those found preoperatively without traction (P > 0.05). Conclusions: Traction radiographic imaging is an effective, feasible preoperative assessment for determining which vertebrae are stable, designing the surgical strategy and choosing the UIV and LIV for correcting moderate to severe, rigid scoliosis.  相似文献   
966.
 目的 观察降钙素基因相关肽(calcitonin-gene-related peptide,CGRP)对人脐静脉血管内皮细胞(human umbilical vein endothelial cells,HUVECs)的成血管作用,初步探讨其在骨组织工程中的应用价值。方法 体外分离获取HUVECs,采用细胞免疫荧光检测其CGRP受体1的表达。体外成管实验检测CGRP的成血管作用,ELISA法检测CGRP直接作用于HUVECs时血管内皮生长因子(vascular endothelial growth factor, VEGF)的分泌水平。Q-PCR检测CGRP刺激HUVECs不同时间点VEGF、VEGF受体1(FLT1)、VEGF 受体2(KDR)及CGRP受体1 mRNA的表达,Western blot检测HUVECs不同时间点FLT1、KDR的蛋白表达。结果 细胞免疫荧光显示HUVECs表达CGRP受体1,体外成管实验显示CGRP有明显的成血管作用。ELISA显示CGRP能明显促进HUVEC分泌VEGF。Q-PCR结果显示不同浓度组CGRP受体1 mRNA的表达较对照组增高,且在第10天最为明显;Q-PCR及Western blot结果显示不同浓度组FLT1、KDR mRNA和蛋白的表达在各时间点较对照组均增高。结论 CGRP能明显促进HUVECs的体外生成血管,可能与其促进VEGF分泌,增强HUVECs的FLT1与KDR表达有关;同时,CGRP受体表达也增加,可进一步增强CGRP的促血管生成作用。  相似文献   
967.
ObjectivesTo study the underlying alteration in the expression of epithelial markers involved in epithelial-mesenchymal transition (EMT), and elucidate the potential mechanism(s) for Tβ4-induced EMT-like phenotypic changes in bladder cancer cells.Materials and methodsAll tissue samples in this study were obtained from clinical patients of the Union Hospital of Tongji Medical College, and were confirmed by surgery and pathology. Of these, normal bladder tissues (control), primary urothelial carcinoma of different grades (Stage pTa, Stage pT3), bladder paracancerous tissues, accompanied with 2 bladder cancer cell lines (BIU-87 and T24), were divided into 6 groups. Quantitative RT-PCR, Western blotting, and immunohistochemical study of adhesion molecules Tβ4, ILK, E-cadherin, and β-catenin involved in EMT were carried out. A lentiviral gene transferring vector containing the RNA polymerase III-dependent U6 promoter to express short hairpin RNA (shRNA) directed against Tβ4 was also applied. In the present study, all agents were evaluated using commercial kits.ResultsA strong correlation between the expression levels of Tβ4, ILK, E-cadherin, and β-catenin was found in the bladder transitional cell carcinoma (TCC) patients. In the BIU-87 and T24 bladder cancer cells overexpressing Tβ4, which were accompanied by a loss of E-cadherin as well as a cytosolic accumulation of β-catenin, up-regulation of ILK was also revealed. The inhibition of the Tβ4 expression with lentiviral shRNA vector could raise EMT-like phenotypic changes, significantly depressed motility, and subsequent invasiveness of bladder cancer cells.ConclusionsOur results imply that the Tβ4 is likely to play a crucial role in EMT progression, and that inhibition of the Tβ4 expression or interactions with other genes should be novel therapeutic targets for bladder cancers with high invasive and metastatic potential.  相似文献   
968.
We studied the efficacy of culture-specific antibiotic therapy for chronic bacterial prostatitis (CBP) patients with or without prostatic calculi. This study included 101 patients (21–62 years old) who met the consensus criteria for CBP (National Institutes of Health category II). According to the results of transrectal ultrasonography (TRUS), all patients were divided into two groups: Group 1, CBP with prostatic calculi, n=39; Group 2, CBP without prostatic calculi, n=62. All patients received optimal antimicrobial therapy for 4 weeks and followed up for a minimum of 3 months (range: 3–8 months). In addition to expressed prostatic secretions (EPS) and urine culture, all patients were asked to complete the National Institutes of Health Chronic Prostatitis Symptom Index (NIH-CPSI) and the subjective global assessment (SGA). The microbiological eradication rate at the end of treatment were 32/39 (82.1%) and 54/62 (87.1%), while the rates for continued eradication at the end of study were 17/39 (43.6%) and 45/62 (72.6%) in Group 1 and Group 2 (P<0.01), respectively. We observed a decrease in the total NIH-CPSI score median values from 24 to 19 in Group 1 and from 24 to 11 in Group 2. The pain subscore (P<0.01), urinary sunscore (P<0.05) and quality of life (QoL; P<0.05) as well as the total NIH-CPSI score (P<0.01) were significantly improved after antimicrobial treatment in Group 2 compared to Group 1. Response, defined as a decrease of the NIH-CPSI total score by at least 50%, was seen in Group 1 versus Group 2 in 38.5% and 58.1% (P<0.01), respectively. Our results showed that prostatic calculi influence the antimicrobial efficacy in men with CBP. There was a noticeable decrease in the cure rate of CBP patients with prostatic calculi due to relapse after antimicrobial therapy.  相似文献   
969.
目的 探讨完全腹腔镜下巨脾切除联合贲门周围血管离断术治疗肝硬化门静脉高压症的可行性、有效性和安全性.方法 对26例患者行巨脾切除联合贲门周围血管离断术,其中16例行完全腹腔镜下二级脾蒂离断法脾切除联合贲门周围血管离断术,10例行传统开腹手术.比较两组的手术时间、术中出血量、术后并发症发生率、术后外周血血小板数值及术后住院时间等.结果 腹腔镜组成功完成手术12例,中转开腹4例.腹腔镜组与开腹组平均手术时间分别为(315±77) min和(291±31)min,两组相比差异无统计学意义,t=0.892,P=0.384;术中平均出血量分别为(409±216) ml和(980±402) ml,两组相比差异有统计学意义,t=4.105,P<0.01;术后并发症发生率分别为17%和30%,两组相比差异无统计学意义,x2=0.064,P=0.525;术后平均住院时间分别为(10±3)d和(17±8)d,两组相比差异有统计学意义,t=2.539,P<0.01.结论 完全腹腔镜下巨脾切除联合贲门周围血管离断术安全、可行、有效,具有出血少、痛苦小、术后住院时间短的优点,是一种值得推广的微创手术.  相似文献   
970.
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