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   20037篇
  免费   1170篇
  国内免费   86篇
耳鼻咽喉   82篇
儿科学   459篇
妇产科学   252篇
基础医学   2527篇
口腔科学   749篇
临床医学   1981篇
内科学   4463篇
皮肤病学   399篇
神经病学   2102篇
特种医学   930篇
外科学   3239篇
综合类   115篇
一般理论   4篇
预防医学   1299篇
眼科学   181篇
药学   1354篇
中国医学   26篇
肿瘤学   1131篇
  2023年   148篇
  2022年   163篇
  2021年   402篇
  2020年   298篇
  2019年   429篇
  2018年   492篇
  2017年   476篇
  2016年   449篇
  2015年   520篇
  2014年   697篇
  2013年   1117篇
  2012年   1439篇
  2011年   1381篇
  2010年   855篇
  2009年   810篇
  2008年   1253篇
  2007年   1285篇
  2006年   1250篇
  2005年   1203篇
  2004年   1051篇
  2003年   1053篇
  2002年   974篇
  2001年   213篇
  2000年   151篇
  1999年   195篇
  1998年   206篇
  1997年   233篇
  1996年   155篇
  1995年   152篇
  1994年   154篇
  1993年   144篇
  1992年   125篇
  1991年   127篇
  1990年   114篇
  1989年   108篇
  1988年   96篇
  1987年   87篇
  1986年   90篇
  1985年   93篇
  1984年   81篇
  1983年   88篇
  1982年   84篇
  1981年   78篇
  1980年   61篇
  1979年   73篇
  1978年   72篇
  1977年   66篇
  1976年   55篇
  1975年   58篇
  1973年   47篇
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
1.
Abstract The aim of the present clinical trial was to test tolerability during 2 treatments with EMDOGAIN® in a large number of patients. An open, controlled study design in 10 Swedish specialist clinics was chosen, with a test group of 107 patients treated with EMDOGAIN® in connection with periodontal surgery at 2 surgical test sites per patient. The procedures were performed 2 to 6 weeks apart on one-rooted teeth with at least 4 mm deep intraosseous lesions. A control group of 33 patients underwent flap surgery without EMDOGAIN® at I comparable site. In total 214 test and 33 control surgeries were performed. Serum samples were obtained from test patients for analysis of total and specific antibody levels. 10 of the patients had samples taken before and after the first surgery. 56 other samples were taken after one treatment with EMDOGAIN®, and 63 after 2 treatments. None of the samples, not even from allergy-prone patients after 2 treatments, indicated deviations from established baseline ranges. This indicates that the immunogenic potential of EMDOGAIN® is extremely low when applied in conjunction with periodontal surgery. Comparison between the test and control groups demonstrated the same type and frequency of post-surgical experiences, i.e., reactions caused by the surgical procedure itself. Clinical probing and radiographic evaluation was performed at baseline and 8 months postsurgery. About half of the patients (44 test and 21 control) were also evaluated after 3 years. There was a significant difference between the test and control results at 8 months post surgery. and this difference had increased further at the 3 year follow-up. The 2.5–3 mm increase in attachment and bone level after treatment with EMDOGAIN® was of the same magnitude as seen in the studies with split-mouth design aiming for lest of effectiveness of EMDOGAIN®.  相似文献   
2.
Male Sprague-Dawley rats dosed with N-nitrosodiethylamine (NDEA)24 h after two-thirds partial hepatectomy were treated withthe pyrethroid insecticides fenvalerate, flucythrinate or cypermethrinin the diet: for 20 weeks. Altered hepatic foci were analyzedby quantitative stereology from paraffin-embedded sections stainedfor  相似文献   
3.
4.
BACKGROUND/PURPOSE: Tattoos have become increasingly popular followed by a growing demand for tattoo removal, and yet there is little knowledge and monitoring of tattoo pigment deposition in skin layers. The purpose of this pilot study is to describe optical coherence tomography image characteristics of intradermal tattoos. METHODS: We included five black tattoos in 3 female volunteers, 39, 35 and 30 years old. In vivo imaging of tattoo pigments in the skin is possible with optical coherence tomography (OCT), a novel non-invasive, in vivo optical imaging technology with a resolution and a penetration in skin high enough for visualization of tattoo pigment in the dermis. RESULTS: In optical coherence tomography images tattoo pigments clusters appear as dark, homogenous vertical columns and structures in the papillary dermis. OCT-scanned normal skin (without tattoos) appeared to be free of this dark structure. CONCLUSION: We have demonstrated that OCT can be used to visualize clusters of light absorbing pigments in a predictable manner.  相似文献   
5.
Magnetic resonance imaging (MRI) of the oropharyngeal region from 20 adult volunteers using four model inhalation devices (varying mouthpiece diameters, airflow resistances) and tidal breathing was carried out. Statistical analysis (convex hull method) selected 12 scans from 80 data sets representing the extremes of all dimensions in the population. Twelve physical mouth-throat models were made by stereolithography using the exact scan data. The aim was to produce models with varying dimensions to span the adult population, and to investigate if oropharyngeal dimensions affected throat retention for different delivery systems. In an in vitro analysis, the models were used to determine the retention effect of the oropharyngeal airspaces when drug aerosols were administered from four inhalation delivery systems: a pressurised metered dose inhaler (pMDI), two different dry powder inhalers (DPIs A and B), and a nebulizer. The aims of this work were to determine the key parameters governing mouth-throat retention and whether retention was dependent on the delivery system used. Characterizing the throat models by measuring 51 different dimensional variables enabled determination of the most influential variables for dose retention for each inhalation delivery system. Throat model retention was found to be dependent on the delivery system (pMDI approximately DPI(A) > DPI(B) > Neb.). The most influential variable was the total throat model volume. Throat models representing high, median, and low oropharyngeal filtration in healthy adults have been identified.  相似文献   
6.
7.
Infrared angiography of the fundus was performed twice on a number of eyes of healthy subjects and glaucoma patients, once when IOP was normal and again when it was increased by around 20 mmHg. The passage of contrast medium through the eye, visible as increasing blackening of the film, was recorded quantitatively by computer-aided image analysis. In both groups there was a considerable diminution of fluorescence, in particular of the choroid; the effect on the central artery and the optic disk was somewhat less pronounced.  相似文献   
8.
9.
The purpose of the present study was to analyse clinically failed and retrieved implants prior to and after cleaning by means of scanning electron microscopy (SEM) and X-ray induced photoelectron spectroscopy (XPS) as compared to unused controls. Six different chemical and physical techniques for cleaning of contaminated titanium implants were evaluated: 1) rinsing in absolute ethanol for 10 min, 2) cleaning in ultrasonic baths containing trichloroethylene (TRI) and absolute ethanol, 10 min in each solution, 3) abrasive cleaning for 30 s, 4) cleaning in supersaturated citric acid for 30 s, 5) cleaning with continuous CO2-laser in dry conditions at 5 W for 10 s, 6) cleaning with continuous CO2-laser in wet conditions (saline) at 5 W for 10 s. SEM of failed implants showed the presence of contaminants of varying sizes and XPS showed almost no titanium but high carbon signals. XPS of unused titanium implants showed lower levels of titanium as previously reported, probably due to contamination of carbon which increased with time in room air. Cleaning of used implants in citric acid followed by rinsing with deionized water for 5 min followed by cleaning in ultrasonic baths with TRI and absolute ethanol gave the best results with regard to macroscopical appearance and surface composition. However, as compared to the unused implants the results from an element composition point of view were still unsatisfactory. It is concluded that further development and testing of techniques for cleaning of organically contaminated titanium is needed.  相似文献   
10.
Perimetry suffers from considerable variability of results. A new technique for estimating individual criterion levels in normal subjects exposes the important role of psychological variables. The analysis depends on features peculiar to acuity perimetry. It can be accommodated in the regular examination. The results can be used to compensate for practice effects in serial examinations and to tighten the range of normal limits. The reduction in variation between normal subjects amounted to 57 per cent.  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