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   23899篇
  免费   1612篇
  国内免费   600篇
耳鼻咽喉   538篇
儿科学   141篇
妇产科学   253篇
基础医学   1747篇
口腔科学   1894篇
临床医学   1530篇
内科学   2413篇
皮肤病学   1553篇
神经病学   670篇
特种医学   870篇
外国民族医学   1篇
外科学   4621篇
综合类   2887篇
现状与发展   1篇
预防医学   602篇
眼科学   3716篇
药学   1509篇
  9篇
中国医学   518篇
肿瘤学   638篇
  2024年   77篇
  2023年   381篇
  2022年   793篇
  2021年   990篇
  2020年   790篇
  2019年   859篇
  2018年   823篇
  2017年   796篇
  2016年   795篇
  2015年   746篇
  2014年   1306篇
  2013年   1460篇
  2012年   1085篇
  2011年   1259篇
  2010年   1060篇
  2009年   1080篇
  2008年   1074篇
  2007年   1072篇
  2006年   947篇
  2005年   884篇
  2004年   802篇
  2003年   696篇
  2002年   593篇
  2001年   592篇
  2000年   481篇
  1999年   405篇
  1998年   401篇
  1997年   385篇
  1996年   327篇
  1995年   304篇
  1994年   292篇
  1993年   268篇
  1992年   247篇
  1991年   239篇
  1990年   195篇
  1989年   167篇
  1988年   153篇
  1987年   155篇
  1986年   137篇
  1985年   200篇
  1984年   186篇
  1983年   118篇
  1982年   111篇
  1981年   94篇
  1980年   78篇
  1979年   45篇
  1978年   54篇
  1977年   33篇
  1976年   26篇
  1974年   18篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
目的比较IQ200全自动尿液分析仪与人工镜检法检测尿中红细胞的结果。方法用IQ200全自动尿液分析仪与人工镜检法对100份尿标本平行测定并观察草酸钙和霉菌孢子对尿中红细胞检测结果的影响。结果草酸钙和霉菌孢子可影响IQ200全自动尿液分析仪对尿中红细胞的测定结果。结论对IQ200全自动尿液分析仪检测出的高红细胞值,建议用人工镜检法确认,避免出现检测误差。  相似文献   
52.
53.
合成了四种结构类型的苯并恶唑化合物共15个:测试了它们的红外吸收光谱,以及它们在DMF中的紫外吸收、荧光发射和激光发射光谱。苯基取代物的荧光量子产率在0.64~0.66,无激光性能。其余的化合物荧光量子产率都大于0.70,在最大吸收波长下的激光转换效率为2.5~5.9%。  相似文献   
54.
The present trial was designed to evaluate clinical scores (single observer) of sodium lauryl sulphate (SLS)-induced skin irritation in a group of subjects (n = 10) over a 10-day period along with various skin function parameters. In order to avoid significant variations due to secondary phenomena, the following parameters were recorded with non-invasive instruments in this order: skin capacitance (C1; arbitrary units; CM420 Corneometer), transepidermal water loss (TEWL; g/m2.h; Evaporimeter) and laser Doppler flowmetry (CBFV: cutaneous blood flow values; Periflux). All examinations were performed during winter on reclined relaxed subjects present for at least 10 min in a test room with controlled temperature and relative humidity (t degrees: 19.5-20.7 degrees C and RH: 47.3-60.3%). The analysis of differential data (delta = value at tx-value before test; 2-way ANOVA) was made on single parameters as a function of site (volar forearm versus neck) and time (from 24 h after 48-h occlusion with 5% SLS up to 10 days later). The profile of erythema scores over time differed between neck and forearm, but the delta CBFV readings with the laser Doppler instrument did not detect significant site-time interactions. Roughness (blind evaluation with palpating finger) and capacitance readings (delta C1) showed significant differences between sites, but the profile over time was similar in both locations. delta TEWL did not differ according to anatomical location. The reason for different erythema scores on neck and forearm might be related to inherent regional variation of optical properties of the skin or to a substantial contribution of SLS-induced roughness to the readings of erythema.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
55.
Prostatectomy by transurethral balloon Laserthermia (PROSTA-LASE?) was performed in a canine model. This balloon device monitored by transrectal ultrasound can cylindrically irradiate with a laser beam. The treatment was performed in 8 canines using 15 watts for 20 minutes at 60°C at a 5 mm depth of the prostate from the urethral surface. Immediately following the laser therapy, an area of coagulation necrosis was observed around the urethra to a depth of 4–5 mm from the surface. After 1 week, cavitation formation was seen in 3 or 4 canines by ultrasound, and the urethral reepithelialization was shown in 1 of 2 canines. After 2 weeks, cavitation formation was observed in both canines, and the urethra was completely reepithelialized in one canine. There was no tissue damage in the bladder neck of urethral sphincter and no urinary incontinence in any animal. This system is thought to be simple and, satisfactorily performed, is an effective transurethral prostatectomy. © 1994 Wiley-Liss, Inc.  相似文献   
56.
The effects of combined use of earthworm extract(912)and HpD-laser on the produc-tion of reactive oxygen and the biosynthesis of DNA in S_(180) tumor cells were studied throughchemiluminescence measurement and[~3H]-TdR incorporation assay.The results showed that as com-pared with the control,the intensity of chemiluminescence emitted by tumor cells treatedsimultaneously with 912 and HpD-laser was enhanced more than ten-folds,while that treated with912 or HpD-laser alone was increased only 2~4 folds.The[~3H]-TdR incorporation into tumorcells of the former group was inhibited upto 74.1%,and that of the latter groups decreased onlyby 42.2% and 40.0%,respectively.In accordance with these biochemical changes,the ultrastructuraldamage of tumor cells of the former,combinedly treated group appeared to be the most serious.This suggests an additive effect of 912 with HpD-laser on tumor cells.In addition,if free radicalscavengers,such as catalase and superoxide dismutase,were added to the reaction systembefore chemiluminescence assay,the luminescent enhancement effect mentioned above was dramaticallyalleviated,implying the presence of O_2~ and H_2O_2 in the system.Therefore,as to the toxic effecton tumor cells,912 and HpD-laser are not only additive in efficiency,but also similar in theunderlying mechanism of action.  相似文献   
57.
The exact regional correlation of findings of facial bone scans, planar or SPECT, to dental orthopan X-ray films (OPT) is difficult because of the very different projection techniques. To improve correlative imaging in this regard a projection algorithm was developed that uses SPECT data of the skull for reconstructing an orthopan tomoscintigraphic projection. Fourteen conventional SPECT slices of the upper and lower jaws were obtained during bone scanning. All mandibular slices were superimposed resulting in a horseshoe shaped structure, which was marked by an ROI which was divided into segments. All 14 SPECT slices were then masked by this segmental ROI, thereby marking the teeth-carrying bone in all slices. The information from this horseshoe like ROI is then transformed into lines. Line by line arrangement results in an orthopan projection, the orthopan tomoscintigram. This new display allows 1:1 true scale superimposition with the X-ray OPT and markedly facilitates correlative imaging.  相似文献   
58.
Pulsed Nd-YAG laser irradiation of bacteria has been suggested as a possible means of treating contaminated intra-oral sites although relatively few studies have been conducted. In this investigation, the antimicrobial activity of a pulsed Nd-YAG laser was assessed in vitro for a range of oral bacteria using several pulse energies and exposure durations. Pure cultures of each organism were lased in saline suspensions followed by standard colony counting techniques for test and control samples. Microbial inhibition was found to be organism-dependent and varied with energy dose and pulse energy. For all nine test species 120-mJ laser pulses proved more efficient than 80-mJ pulses, with 99.9% kills compared with around 90% kills after exposure to 1800 pulses. These killing activity levels compare favourably with those achieved with other lasers in vitro.  相似文献   
59.
应用DMSO(Dimethylsulfoxide二甲基亚砜)冷冻割断制样扫描电镜技术首次动态观察了不同感染阶段(postInfection,PI)实验性单纯疱疹病毒性角膜炎(HSK)兔的角膜、三叉神经节(TG)泪腺等组织的病变情况。初步报告并分析了各组织病变的扫描图像结果,并对冷冻割断法观察扫描电镜的原理及优缺点予以讨论,认为该技术应用于眼部单疱病毒感染的研究图像清晰、直观、简便可行,是一种有实用价值的方法。  相似文献   
60.
Erb:YAG and Hol:YAG laser ablation rates of fibrocartilage and nucleus pulposus were measured in vitro simulating clinical conditions. After ablation macroscopic and microscopic appearance of the ablation site was investigated. Hol:YAG and Erb:YAG laser mean ablation rates increased almost linearly with rising energies, showing higher total ablation rates for the Hol:YAG laser due to its higher achievable energy density. At comparable energy densities the Erb:YAG laser appears to be more effective with respect to the corresponding ablation rates. Consequently, the ablational threshold proved to be lower for the Erb:YAG laser. Whereas during Hol:YAG laser ablation, some smoke formation and considerable tissue shrinking occurred, these effects could not be observed during Erb:YAG laser ablation. Consequently macroscopic and microscopic inspection showed some thermal damage after Hol:YAG and only minimal alterations after Erb:YAG laser ablation. Adjacent thermal damage was determined and proved to be lower for the Erb:YAG laser. In our opinion the characteristics of each laser system provide certain advantages for special clinical indications.  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