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   2293篇
  免费   123篇
  国内免费   14篇
耳鼻咽喉   28篇
儿科学   90篇
妇产科学   29篇
基础医学   268篇
口腔科学   224篇
临床医学   175篇
内科学   497篇
皮肤病学   36篇
神经病学   143篇
特种医学   253篇
外科学   208篇
综合类   65篇
预防医学   170篇
眼科学   60篇
药学   109篇
中国医学   21篇
肿瘤学   54篇
  2023年   5篇
  2022年   26篇
  2021年   39篇
  2020年   27篇
  2019年   35篇
  2018年   34篇
  2017年   38篇
  2016年   34篇
  2015年   45篇
  2014年   83篇
  2013年   128篇
  2012年   122篇
  2011年   116篇
  2010年   84篇
  2009年   102篇
  2008年   132篇
  2007年   131篇
  2006年   110篇
  2005年   93篇
  2004年   77篇
  2003年   52篇
  2002年   55篇
  2001年   50篇
  2000年   47篇
  1999年   36篇
  1998年   88篇
  1997年   58篇
  1996年   65篇
  1995年   48篇
  1994年   50篇
  1993年   44篇
  1992年   26篇
  1991年   20篇
  1990年   22篇
  1989年   46篇
  1988年   31篇
  1987年   32篇
  1986年   22篇
  1985年   13篇
  1984年   17篇
  1983年   16篇
  1982年   15篇
  1981年   21篇
  1980年   13篇
  1979年   9篇
  1978年   10篇
  1977年   17篇
  1976年   9篇
  1975年   13篇
  1966年   4篇
排序方式: 共有2430条查询结果,搜索用时 15 毫秒
71.
ObjectiveThe aim of the study was to evaluate the effect of topical fluoride gel NaF 2% application on antioxidant parameters of whole saliva from children.DesignThe saliva mechanically stimulated with parafilm was collected from 25 children (6–12 years) attending the Clinic of Paediatric Dentistry of Universidade Cruzeiro do Sul, São Paulo, Brazil, before (control group) and immediately after application of neutral fluoride gel NaF 2% (fluoride-gel group), according to the Standards for Research Using Human Subjects, Resolution 196/96 of the USA National Health Council of 10/10/1996. Afterwards, pre-post ferric-reducing antioxidant power (FRAP), trolox-equivalent antioxidant capacity (TEAC), uric acid, reduced/oxidised glutathione content (GSH/GSSG) and total peroxidase activity (TPO) were evaluated in whole saliva of both groups.ResultsAll non-enzymatic antioxidant parameters were augmented by fluoride-gel NaF 2% application, whereas a notable reduction (31%) of peroxidase activity was concomitantly observed in the children's saliva (p  0.05). Nevertheless, the reducing power of saliva was kept unaltered under these circumstances (p  0.05).ConclusionsDespite the reduced activity of peroxidase (an important antimicrobial and antioxidant enzyme), the topical fluoride gel NaF 2% favourably stimulated the release of non-enzymatic antioxidant components of saliva, sustaining the reducing power of saliva and the natural defences of the oral cavity.  相似文献   
72.

Introduction

Acute pulmonary thromboembolism (APT) is a critical condition associated with acute pulmonary hypertension. Recent studies suggest that oxidative stress and hemolysis contribute to APT-induced pulmonary hypertension, possibly as a result of increased nitric oxide (NO) consumption. We hypothesized that the antioxidant tempol could attenuate APT-induced hemolysis, and therefore attenuate APT-induced increases in plasma NO consumption.

Materials and Methods

APT was induced in anesthetized sheep with autologous blood clots. The hemodynamic effects of tempol infused at 1.0 mg/kg/min 30 min after APT were determined. Hemodynamic measurements were carried out every 15 min. To assess oxidative stress, serum 8-isoprostanes levels were measured by ELISA. Plasma cell-free hemoglobin concentrations and NO consumption by plasma samples were determined. An in vitro oxidative AAPH-induced hemolysis assay was used to further validate the in vivo effects of tempol.

Results

APT caused pulmonary hypertension, and increased pulmonary vascular resistance in proportion with the increases in 8-isoprostanes, plasma cell-free hemoglobin concentrations, and NO consumption by plasma (all P < 0.05). Tempol attenuated the hemodynamic alterations by approximately 15-20% and blunted APT-induced increases in 8-isoprostanes, in cell-free hemoglobin concentrations, and the increases in NO consumption by plasma (P < 0.05). Tempol dose-dependently attenuated AAPH-induced in vitro hemolysis (P < 0.05).

Conclusions

Our findings are consistent with the idea that antioxidant properties of tempol decrease APT-induced hemolysis and nitric oxide consumption, thus attenuating APT-induced pulmonary hypertension.  相似文献   
73.
Mowat–Wilson syndrome (MWS) is a rare genetic condition where variable and multiple congenital anomalies including Hirschsprung's disease, intellectual disability, and prominent facial features are present. At molecular level, MWS is characterized by many different described mutations in the zinc finger E-box protein 2 (ZEB2) gene, ultimately leading to loss of gene function. This report is the first to describe the association of MWS with two different asynchronous malignant brain tumors (medulloblastoma and glioblastoma) occurring in a child.  相似文献   
74.
Although long known and the most prevalent movement disorder, pathophysiology of essential tremor (ET) remains controversial. The most accepted hypothesis is that it is caused by a dysfunction of the olivocerebellar system. Vilela Filho et al. [2001; Stereotact Funct Neurosurg 77:149–150], however, reported a patient with unilateral hand ET that was completely relieved after a stroke restricted to the contralateral posterior putamen and suggested that ET could be the clinical manifestation of posterior putamen hyperactivity. The present study was designed to evaluate this hypothesis in the most often used model of ET, harmaline‐induced tremor in rats. Fifty‐four male Wistar rats were randomly distributed into three groups: experimental (EG), surgical control (SCG), and pharmacological control (PCG) groups. EG animals underwent stereotactic unilateral posterior striatotomy. SCG rats underwent sham lesion at the same target. PCG served exclusively as controls for harmaline effects. All animals received, postoperatively, intraperitoneal harmaline, and the induced tremor was video‐recorded for later evaluation by a blind observer. Thirteen animals were excluded from the study. Limb tremor was reduced ipsilaterally to the operation in 20 of 21 rats of EG and in two of nine of SCG, being asymmetric in one of 10 of PCG rats. Comparisons between EG × SCG and EG × PCG were statistically significant, but not between SCG × PCG. Limb tremor reduction was greater in anterior than in posterior paws. Lateral lesions yielded better results than medial lesions. These results suggest that the posterior striatum is involved with harmaline‐induced tremor in rats and support the hypothesis presented. © 2013 Wiley Periodicals, Inc.  相似文献   
75.
Peri-implantitis is a pathology that has been described in many clinical studies and case reports. However, it is still not clear how the roles of its etiologic agents work. This article is based on a review of the literature and a case report. It aims to offer data related to the factors that cause this pathology, and to analyze how these factors interact, leading to the contamination of the peri-implant tissue.  相似文献   
76.
Autosomal dominant polycystic kidney disease (ADPKD), a genetic disease caused by mutations in PKD1 or PKD2 genes, is associated with a high prevalence of nephrolithiasis. The underlying mechanisms may encompass structural abnormalities resulting from cyst growth, urinary metabolic abnormalities or both. An increased frequency of hypocitraturia has been described in ADPKD even in the absence of nephrolithiasis, suggesting that metabolic alterations may be associated with ADPKD per se. We aimed to investigate whether non-cystic Pkd1-haploinsufficient (Pkd1 +/?) and/or nestin-Cre Pkd1-targeted cystic (Pkd1 cond/cond:Nestincre) mouse models develop urinary metabolic abnormalities potentially related to nephrolithiasis in ADPKD. 24-h urine samples were collected during three non-consecutive days from 10–12 and 18–20 week-old animals. At 10–12 weeks of age, urinary oxalate, calcium, magnesium, citrate and uric acid did not differ between test and their respective control groups. At 18–20 weeks, Pkd1 +/? showed slightly but significantly higher urinary uric acid vs. controls while cystic animals did not. The absence of hypocitraturia, hyperoxaluria and hyperuricosuria in the cystic model at both ages and the finding of hyperuricosuria in the 18–20 week-old animals suggest that anatomic cystic distortions per se do not generate the metabolic disturbances described in human ADPKD-related nephrolithiasis, while Pkd1 haploinsufficiency may contribute to this phenotype in this animal model.  相似文献   
77.
Background

Remote monitoring (RM) of cardiac implantable electronic devices (CIEDs) is standard of care. However, it is underutilized. In July 2012, our institution began providing cell phone adapters (CPAs) to patients free of charge following CIED implantation to improve remote transmission (RT) adherence.

Methods

Patients in our institution’s RM database from January 1, 2010, thru June 30, 2015, were retrospectively reviewed. There were 2157 eligible patients. Remote transmission proportion (RTP) and time to transmission (TT) were compared pre- and post-implementation of free CPA. Chi-squared analysis and Kruskal-Wallis tests were performed to compare RTP and TT.

Results

There was a significant increase in RTP (134 [18.4%] vs 99 [54.7%]; p?<?0.001) and decrease in median TT in days (189[110–279] vs 58 [10–149]; p?<?0.001) after CPAs were provided to patients. Caucasian patients were more likely than African Americans and Hispanics to use RM prior to CPAs (p?=?0.04). After the implementation of CPAs, there was a significant increase in RTP for all racial groups (<?0.001) with no difference in RTP among racial groups (p?=?0.18). The RTP for urban residents was significantly greater than non-urban residents with CPAs (p?=?0.008). Patients greater than 70 years of age were significantly less likely to participate in RT before and after CPAs were provided (p?=?0.03, p?=?0.01, respectively).

Conclusions

CPAs significantly improve RTP and reduce median TT for all patients regardless of race, geographic residence, and age (>?70 years old to lesser extent). Broad institution of CPAs following ICD implantation could potentially reduce disparity in RTP and deserves more study.

  相似文献   
78.
八项肝纤维化血清标志物比较研究   总被引:36,自引:0,他引:36  
目的比较血清血小板衍生生长因子-BB(PDGF-BB)、转化生长因子-β1(TGF-B1)、基质金属蛋白酶抑制剂-1(TIMP-1)、基质金属蛋白酶-1(MMP-1)、透明质酸(HA)、Ⅲ型前胶原(PC Ⅲ)、Ⅳ型胶原(C Ⅳ)和层黏连蛋白(LN)及外周血单个核细胞(PBMC)内TIMP-1 mRNA、MMP-1 mRNA在肝纤维化中的诊断价值。方法常规肝穿活检、组织病理学诊断;RT-PCR检测PBMCs中MMP-1 mRNA、TIMP-1 mRNA水平;酶标法检测血清PDGF-BB、TGF-β1、TIMP-1和MMP-1含量;放射免疫法检测血清HA、PC Ⅲ、C-Ⅳ和LN含量。结果经ROC曲线分析,血清PDGF-BB、TIMP-1、HA、PC Ⅲ、C-Ⅳ、LN和TIMP-1 mRNA的AUC分别为0.985、0.726、0.318、0.728、0.727、0.583、0.463、0.876;血清PDGF-BB和PBMCs中TIMP-1 mRNA的灵敏度和特异度分别为90%、95%,73.7%、100%;两者联合检测的灵敏度为97.4%,特异度为95.0%。结论八项指标中,血清PDGF-BB的诊断价值最大。在筛选肝纤维化患者时,以血清PDGF-BB、PBMC中TIMP-1 mRNA联合检测最佳。  相似文献   
79.
Scandella  D; Mattingly  M; de Graaf  S; Fulcher  CA 《Blood》1989,74(5):1618-1626
Human factor VIII(FVIII) inhibitors are pathologic, circulating antibodies that inactivate FVIII. We have examined the location of epitopes on the FVIII protein for inhibitors from hemophilia A and nonhemophilic individuals. The inhibitors were of type I or type II in the kinetics of their inactivation of FVIII. A cDNA clone of human FVIII was used to express defined FVIII protein fragments in Escherichia coli for immunoblotting with inhibitor plasma. An epitope for 18 heavy-chain inhibitors was localized to the aminoterminal 18.3 Kd of the A2 domain. Two of these inhibitors also recognized an epitope located between A1 and A2 domains. Similarly, an epitope for 23 light- chain inhibitors was localized to the C2 domain. Weaker epitopes for 13 of the same inhibitors within the C1 and C2 domains were also observed. Four of the 23 inhibitors in addition bound strongly to the A3 domain. Most inhibitors (22 of 23) were neutralized in vitro only by the FVIII fragments to which they bound on immunoblots; however, one inhibitor that was neutralized by a fragment containing the A1 domain did not bind to it on immunoblots. Conversely, 3 of 3 inhibitors that bound to the A3 domain and 5 of 15 that bound to the A2 domain were not neutralized by the corresponding fragments. The epitope specificity of an inhibitor did not depend on its source or type. Our results show that FVIII inhibitors bind to limited areas within the heavy and light chains of FVIII. Some inhibitor plasmas contain additional antibodies that may not be inhibitory.  相似文献   
80.
Cai  SP; Chang  CA; Zhang  JZ; Saiki  RK; Erlich  HA; Kan  YW 《Blood》1989,73(2):372-374
We used in vitro DNA amplification by the polymerase chain reaction and nonradioactive probes for prenatal diagnosis of beta thalassemia in Chinese from the Guangdong province. Exact molecular diagnoses were made in all 20 fetuses studied over a 6-month period. We conclude that this method of prenatal diagnosis for beta thalassemia is a viable approach in many parts of the world where this disease is common.  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