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   1980篇
  免费   162篇
  国内免费   18篇
耳鼻咽喉   21篇
儿科学   61篇
妇产科学   54篇
基础医学   243篇
口腔科学   88篇
临床医学   198篇
内科学   392篇
皮肤病学   81篇
神经病学   110篇
特种医学   61篇
外国民族医学   3篇
外科学   276篇
综合类   64篇
一般理论   1篇
预防医学   113篇
眼科学   40篇
药学   241篇
中国医学   7篇
肿瘤学   106篇
  2024年   3篇
  2023年   53篇
  2022年   89篇
  2021年   170篇
  2020年   100篇
  2019年   135篇
  2018年   145篇
  2017年   93篇
  2016年   95篇
  2015年   109篇
  2014年   85篇
  2013年   120篇
  2012年   165篇
  2011年   139篇
  2010年   98篇
  2009年   59篇
  2008年   102篇
  2007年   77篇
  2006年   74篇
  2005年   57篇
  2004年   37篇
  2003年   31篇
  2002年   38篇
  2001年   19篇
  2000年   8篇
  1999年   8篇
  1998年   4篇
  1997年   7篇
  1996年   3篇
  1995年   6篇
  1994年   2篇
  1993年   1篇
  1992年   2篇
  1991年   2篇
  1990年   6篇
  1989年   2篇
  1988年   1篇
  1987年   3篇
  1986年   1篇
  1985年   2篇
  1983年   2篇
  1981年   1篇
  1974年   1篇
  1969年   1篇
  1968年   1篇
  1967年   1篇
  1940年   2篇
排序方式: 共有2160条查询结果,搜索用时 906 毫秒
41.
Twenty-one patients undergoing coronary artery bypass grafting were prospectively evaluated by conventional selective coronary angiography and electron-beam computed tomography. Eighty bypass grafts (60 saphenous vein and 20 left or right internal mammary artery) were evaluated for patency. The sensitivity and specificity of electron-beam computed tomography were 72% and 100%, respectively; positive and negative predictive values were 100% and 92.5%, respectively. Sensitivity and specificity according to coronary region were: left anterior descending artery, 33% and 100%; diagonal artery, 67% and 100%; circumflex artery, 75% and 100%; right coronary artery, 100% and 100%. Electron-beam computed tomography is relatively accurate and a promising tool for noninvasive evaluation of graft patency after coronary artery bypass graft surgery.  相似文献   
42.

Objectives

To assess safety, efficacy and follow-up results of transcatheter closure of ventricular septal defect (VSD) using Nit-Occlud_ Lê VSD Coil (pfm medical, KÖln, Germany).

Background

Transcatheter VSD closure has achieved encouraging results but more follow-up studies are needed.

Patients and methods

Between January 2012 and December 2013 in the cardiology department, Tanta University Hospital, Tanta, Egypt, 80 patients underwent percutaneous VSD closure using Nit-Occlud_ Lê VSD Coil. Early and mid- term follow-up was done for 3 years, follow-up was concluded in 2016.

Results

The mean age of patients was 5.34?±?3 years, and their mean weight was 17.24?±?8.17 kg. Overall, 77 of 80 patients had perimembranous VSD with aneurysmal tissue; eight had multiple right ventricular exits, 14 had deficient aortic rim, two had high outlet muscular, and one had Gerbode defect. The procedure was successful in 98.75% of patients, and was aborted in one patient because of the development of complete heart block and the coil had to be removed. The mean procedure time was 104.98?±?9.50 minutes. The mean fluoroscopy time was 30.58?±?2.79 minutes. The immediate complete occlusion rate was 62%, which increased to 82.3% on the second day, and 94.9% by the 3rd month, and 97.5% by 1 year. There was a significant decrease in mitral incompetence after 6 months of follow-up (p?=?0.002), and only one patient had trivial aortic incompetence prior to the procedure that remained the same during follow-up period.

Conclusion

Using Nit-Occlud_ Lê VSD-Coil to close VSD is safe and feasible in VSDs with various morphology.  相似文献   
43.
ObjectiveThe purpose of this study was to investigate the effects of ischemic pressure (IP) vs postisometric relaxation (PIR) on rhomboid-muscle latent trigger points (LTrPs).MethodsForty-five participants with rhomboid-muscle LTrPs were randomly assigned into 3 groups and received 3 weeks of treatment—group A: IP and traditional treatment (infrared radiation, ultrasonic therapy, and transcutaneous electrical nerve stimulation); group B: PIR and traditional treatment; and group C: traditional treatment. Shoulder pain and disability, neck pain and disability, and pressure pain threshold (PPT) of 3 points on each side were measured before and after treatment.ResultsMultivariate analysis of variance indicated a statistically significant Group × Time interaction (P = .005). The PPT for the right lower point was increased in group A more than in groups B or C. Neck pain was reduced in group B more than in group C. Moreover, shoulder and neck disability were reduced in both groups A and B more than in group C. The PPTs of the left lower and middle points were increased in group B compared with groups A and C. The PPT of the left upper point was increased in group A more than in group C. There were significant changes in all outcomes in the 2 experimental groups (P < .05). No changes were found in the control group except in pain intensity, shoulder disability, and PPT of the left lower point.ConclusionThis study found that IP may be more effective than PIR regarding PPT, but both techniques showed changes in the treatment of rhomboid-muscle LTrPs.  相似文献   
44.
Gut microbiota consists of 1010 bacteria per gram of stool. Many antibiotic regimens induce a reduction in both the diversity and the abundance of the gut flora. We analyzed one stool sample collected from a patient treated for drug-resistant Mycobacterium tuberculosis and who ultimately died from pneumonia due to a Streptococcus pneumoniae 10 months later. We performed microscopic observation, used 70 culture conditions (microbial culturomics) with identification by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) and 16S rRNA amplification and sequencing, pyrosequencing, and 18S rRNA amplification and clone sequencing. Electron and optical microscopic observations revealed the presence of yeast, but no bacterial species were observed. By culture, only 39 bacterial species were identified, including one new species, as well as three species that have not been previously observed in the human gut. The pyrosequencing showed only 18 phylotypes, detecting a lower number of bacterial species than the culture techniques. Only two phylotypes overlapped with culturomics. In contrast, an amount of chloroplasts was found. Additionally, specific molecular eukaryote detection found three fungal species. We recovered, for the first time, more cultivable than non-cultivable bacterial species in a patient with a low bacterial load in the gut, demonstrating the depth bias of pyrosequencing. We propose that the desertification of gut microbiota in this patient is a reflection of the total body microbiota and may have contributed to the invasive infection of S. pneumoniae. This finding suggests that caution should be applied when treating patients with broad-spectrum antibiotics, and preventive measures should be taken in order to avoid invasive infection.  相似文献   
45.
46.
IntroductionCurcumin therapeutic applications are constrained by its prominent metabolic instability as well as inadequate absorption and bioavailability. The current study was designed to enhance the curcumin bioavailability by exploiting nanoparticles.Material and methodsEleven groups of mice were divided into: normal and nanoparticle control groups, a hepatocellular carcinoma (HCC) group induced by diethylnitrosamine (DEN), 2 groups treated with DEN plus a high dose/low dose of free curcumin, 2 groups treated with a high dose/low dose of free curcumin, 2 groups treated with DEN plus a high dose/low dose of nanoparticulate curcumin, and 2 groups treated with a high dose/low dose of nanoparticulate curcumin.ResultsDEN administration significantly increased liver enzymes, vascular endothelial growth factor, tumor necrosis factor-α, α-fetoprotein, malondialdehyde, and nucelar factor-κB. Also, it decreased serum albumin and tissue antioxidant activities and caused severe histological changes in hepatic tissue. Oral treatment of DEN-injected mice with either a high dose of free curcumin or the tested doses of nanoparticulate curcumin resulted in a significant improvement of all the tested parameters.ConclusionsAlthough the two tested doses of nanoparticulate curcumin were much lower than free curcumin, both doses were effective in preventing HCC development while the low dose of free curcumin was hardly effective. Hence, we conclude that nanoparticles enhance the bioavailability of curcumin.  相似文献   
47.
In this study, an electrochemical DNA biosensor was developed based on the fabrication of silicon nanowires/platinum nanoparticles (SiNWs/PtNPs) on a screen-printed carbon electrode (SPCE) for the detection of Sus scrofa mitochondrial DNA (mtDNA) in food utilizing a new hybrid indicator, ferrocenylnaphthalene diimide (FND). The morphology and elemental composition of the SiNWs/PtNPs-modified SPCE was analyzed by field emission scanning electron microscopy (FESEM) combined with energy dispersive X-ray spectroscopy (EDX). Cyclic voltammetry (CV) was used to study the electrical contact between the PtNPs and the screen-printed working electrode through SiNWs, while electrochemical impedance spectroscopy (EIS) was used to measure the charge transfer resistance of the modified electrode. The results clearly showed that the SiNWs/PtNPs were successfully coated onto the electrode and the effective surface area for the SiNWs/PtNPs-modified SPCE was increased 16.8 times as compared with that of the bare SPCE. Differential pulse voltammetry used for the detection of porcine DNA with FND as an intercalator confirmed its specific binding to the double-stranded DNA (dsDNA) sequences. The developed biosensor showed a selective response towards complementary target DNA and was able to distinguish non-complementary and mismatched DNA oligonucleotides. The SiNWs/PtNPs-modified SPCE that was fortified with DNA hybridization demonstrated good linearity in the range of 3 × 10−9 M to 3 × 10−5 M (R2 = 0.96) with a detection limit of 2.4 × 10−9 M. A cross-reactivity study against various types of meat and processed food showed good reliability for porcine samples.

An electrochemical DNA biosensor was developed based on the fabrication of silicon nanowires/platinum nanoparticles on a screen-printed carbon electrode for the detection of Sus scrofa mitochondrial DNA in food.  相似文献   
48.
Aging is an unavoidable fate that afflicts all life, during this process in mammals reactive oxygen species (ROS) are generated which stimulate tyrosinase, elastase and collagenase activities that actively participate in skin aging. Therefore, the maintenance of antioxidant homeostasis is an important anti-aging strategy for skin. Nature has excellent anti-aging remedies that act externally as well as internally to delay the visual signs of aging. In view of this fact, the present study investigates the in vitro anti-aging activity of five medicinal plants belonging to phenolic rich families namely Rosmarinus officinalis, Lavandula officinalis, Matricaria chamomilla, Camellia sinensis and Pelargonium graveolens. The selected plants are those most frequently used in the preparation of ethnomedicinal recipes for the prevention or treatment of aging. The inhibitory effects of the ethanolic and aqueous extracts of the five selected plants on the activity of tyrosinase, elastase, and collagenase enzymes were investigated. Furthermore, the chemical composition of the plants and the antioxidant capacity of their extracts were assessed. The results showed that R. officinalis had the highest total phenolics content which was correlated with its potent antioxidant and anti-aging activities. To pinpoint the active metabolites in the tested extracts, we evaluated the metabolite variations using ultra-performance liquid chromatography coupled with high resolution electrospray ionization-tandem mass spectrometry (UPLC-HR-ESI-MS/MS). Multivariate data analysis (MVDA) revealed that R. officinalis significantly accumulated metabolites from the aromatic diterpenoid, flavonoid and phenolic acid classes. These results indicate that rosemary can be used for further development of topical preparations with anti-aging properties.

Aging is an unavoidable fate that afflicts all life, during this process in mammals, reactive oxygen species (ROS) are generated which stimulate tyrosinase, elastase and collagenase activities that actively participate in skin aging.  相似文献   
49.
50.
Background: The aim of this study is to investigate the protein and gene expression of leptin and visfatin in gingival tissue from patients with chronic periodontitis (CP), patients with CP and type 2 diabetes mellitus (T2DM), and healthy individuals. Methods: The study includes 50 individuals: 10 healthy individuals, 20 patients with CP, and 20 patients with CP and T2DM. Plaque index, gingival index, probing depth, and clinical attachment loss were measured, and gingival biopsies were obtained. Leptin and visfatin protein expression in gingival tissues was determined using enzyme‐linked immunosorbent assay, and messenger RNA (mRNA) expression was measured via real‐time polymerase chain reaction. Results: The highest leptin mRNA and protein expression was observed in the control group and was significantly (P ≤0.05) different from the CP and CP+T2DM groups. Gingival tissues from patients with CP and T2DM had a significant increase in visfatin and a decrease in leptin gene and protein expression (P <0.05) compared with both controls and patients with CP. Conclusion: Expression of leptin and visfatin in the gingival tissues suggests a possible role for these adipokines in the pathogenesis of CP and T2DM.  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