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   3104篇
  免费   164篇
  国内免费   98篇
耳鼻咽喉   10篇
儿科学   26篇
妇产科学   31篇
基础医学   609篇
口腔科学   63篇
临床医学   656篇
内科学   361篇
皮肤病学   18篇
神经病学   86篇
特种医学   95篇
外国民族医学   1篇
外科学   142篇
综合类   417篇
预防医学   417篇
眼科学   13篇
药学   171篇
  4篇
中国医学   48篇
肿瘤学   198篇
  2024年   3篇
  2023年   18篇
  2022年   63篇
  2021年   97篇
  2020年   130篇
  2019年   57篇
  2018年   87篇
  2017年   77篇
  2016年   106篇
  2015年   130篇
  2014年   250篇
  2013年   213篇
  2012年   285篇
  2011年   331篇
  2010年   201篇
  2009年   234篇
  2008年   246篇
  2007年   237篇
  2006年   176篇
  2005年   130篇
  2004年   73篇
  2003年   66篇
  2002年   20篇
  2001年   13篇
  2000年   10篇
  1999年   8篇
  1998年   7篇
  1997年   6篇
  1996年   3篇
  1995年   10篇
  1994年   5篇
  1993年   2篇
  1992年   3篇
  1991年   2篇
  1990年   5篇
  1989年   7篇
  1988年   2篇
  1987年   2篇
  1986年   5篇
  1985年   5篇
  1984年   5篇
  1983年   6篇
  1982年   5篇
  1981年   11篇
  1980年   5篇
  1979年   3篇
  1978年   3篇
  1977年   1篇
  1975年   2篇
排序方式: 共有3366条查询结果,搜索用时 15 毫秒
11.
An interactive, minicomputer system has been constructed for analyzing dynamic phenomena recorded on movie film in a developmental biology laboratory. The minicomputer interfaces a stop-motion, variable speed projector, a digitizing pen, and real-time graphics display equipment. An analyst uses the pen to digitize features in a film, e.g. by following a cell. A computer-generated animation portraying all data entered is superimposed on the film image and synchronized with it. Noteworthy system features include: image overlays on a large screen, data entry with the projector running, large data capacity, computer control of the projector, and convenient data entry tools.  相似文献   
12.
为了建立一种能广泛应用于临床快速、简便、灵敏度和特异性较好的风疹病毒(RV)定量诊断方法。针对RV基因保守序列设计两对引物和一条荧光双标记探针。将PCR扩增所得到的产物片段克隆,作为定量检测的标准品,进行Real-time PCR检测,绘制标准曲线。将此方法和ELISA试剂盒平行检测50份孕妇血清,评估两种方法检出阳性率的差异显著性。Real-time PCR法能较好地检出RVcDNA载量。曲线的相关系数(r)为0.998,可检测线性范围大约在103~109copies/μl,灵敏度接近103copies/μl;批间、批内CV值分别为3.36%、0.94%;也有较好的特异性。与经典的ELISA方法相比,有显著性差异。Real-time PCR方法操作简单、快速,并能避免PCR后处理导致的假阳性污染,实现实时定量。此方法对RV感染的临床诊断和疗效判断等方面有较大的指导意义。  相似文献   
13.
目的:探讨脂血、高胆红素和溶血标本对乙肝病毒DNA(HBVDNA)荧光定量测定结果的影响。方法:将乙肝大三阳高脂血和非脂血、溶血血清和未溶血血清同时作HBVDNA荧光定量检测;将HBVDNA阴性黄疸血清和HBVDNA阴性正常血清与来自同一份乙肝大三阳血清混合,在相同条件下进行HBVDNA荧光定量。结果:乙肝大三阳溶血与未溶血样本HBVDNA含量都在同一数量级。乙肝大三阳高脂血的HBVDNA含量明显低于对照标本。高黄疸血清、正常对照血清与相同的HBVDNA阳性模板组合后所测得的HBVDNA结果无差异。结论:脂血对HBVD-NA定量测定有严重干扰;溶血样本、高胆红素样本对HBVDNA测定结果无影响。  相似文献   
14.
Dynamic behavior of leukocytes in the microcirculation of solid tumor tissue was visualized using a fluorescent labeling technique combined with the use of a real-time confocal laser-scanning microscope (CLSM) system. Colon tumor cells (RCN-9) were inoculated into the peritoneal cavity of male Fischer 344 rats. Tumor-free rats were similarly injected with physiological saline (intraperitoneally). Ten days after tumor inoculation, the mesentery was exteriorized and subjected to vital microscopic observation under the CLSM system. Leukocytes were labeled with rhodamine 6G (100 g kg–1, intravenously), and their behavior within the microvessels (10–30 m in diameter) was analyzed both in the solid tumor tissues and the normal mesentery. Wall shear rate was calculated from the measured values of vessel diameter and erythrocyte flow velocity. In tumor microvasculature of tumor-bearing rats, the centerline erythrocyte velocity (0.73 ± 0.58 mm s–1, mean±standard deviation) and wall shear rate (210 ± 151 s–1 were significantly lower than those of the tumor-free rats (1.27 ± 0.83 mm s, 344 ± 236 s–1, respectively). Despite such reduced flow conditions, flux of the rolling leukocytes as well as density of the adhered leukocytes both decreased significantly in tumor microvasculature as compared with normal controls. The methods developed in this work show promise in improving our understanding of tumor biology and pathophysiology. © 1998 Biomedical Engineering Society. PAC98: 8722Fy, 8745Hw, 8745Ft, 8764-t, 4262Be  相似文献   
15.
A new algorithmic-based digital filter processing system for real-time continuous blood pressure (BP) measurement and analysis in freely-moving conscious rats has been developed. Real-time recognition of BP waveforms, real-time noise rejection and determination of representative waveform indexes (WIs) at indicated time points using digital filters and Smirnov's rejection test were realized with this system. Digital filters were applied for two different purposes: waveform segmentation and smoothing the calculations of representative WIs. Smirnov's rejection test was used for real-time noise rejection and yielded an accurate rejection rate of 99.99%. The result was that the digital filter processing and Smirnov's rejection test realized accurate real-time BP measurement and analysis in freely-moving conscious rats using a personal computer.  相似文献   
16.
Correlation of MRT imaging with real-time axiography of TMJ clicks   总被引:2,自引:0,他引:2  
There is a series of tools useful for gathering diagnostic information on patients with temporomandibular joint disorders. Tracings of the joint movement (axiography) provide useful information about the motion of the joints. Since the availability of electronic axiographic tracers, the movement of the condyles can be resolved with high resolution both in space and in time. In order to obtain information about the anatomical relation of the joint surfaces and the disc, magnetic resonance tomography imaging (MRI) is routinely carried out. It is common practice to take MR images of the joints with the mouth closed and fully open. In order to correlate the MR images with the axiographic tracings, a series of images can provide much more information. In this study we examined patients with distinct temporomandibular joint (TMJ) clicks. In one case, the click occurs once a day, while in the other case the click happens every time the mouth is opened. In order to obtain information about both motion and anatomical relation of the TMJ at and around the position where the clicks occur, we recorded a series of MRI scans with the mouth gradually opened and before and after joint clicks. Real-time axiographic tracings during the click were taken with an optimized system where the polar moments were reduced as much as possible to follow the movement during the click. These tracings were correlated with the MRI scans to determine the exact internal conditions of the TMJ and the changes during the click. In particular cases, the additional information provided by this procedure can be useful in deciding whether and which therapeutic intervention is advisable.  相似文献   
17.
Victoria JG  Robinson WE 《Virology》2005,338(2):281-291
Vif is dispensable for simian immunodeficiency virus (SIV) replication in some cells, termed permissive (i.e., CEM-SS), but not in others, termed non-permissive (i.e., H9, CEMx174, and peripheral blood lymphocytes). Non-permissive cells express the RNA editing enzyme, APOBEC3G. To determine whether vif mRNA could be alternatively spliced, a mutation altering the putative vif splice acceptor site (SA1) was introduced into SIV(mac239) (SIV(Deltavif-SA)). Despite three consensus splice acceptor sites nearby SA1, SIV(Deltavif-SA) did not efficiently generate alternatively spliced vif mRNA. SIV(Deltavif-SA) was growth attenuated in CEMx174 and H9 cells but not in CEM-SS cells. Following SIV(Deltavif-SA), but not SIV(mac239), infection in either H9 or CEMx174 cells viral cDNA contained numerous G to A mutations; no such differences were observed in CEM-SS cells. This pattern is consistent with mutations generated by APOBEC3G in the absence of Vif. Therefore, efficient splicing of SIV vif mRNA is tightly controlled and requires the SA1 site.  相似文献   
18.
基于经验模式分解的心电特征提取算法   总被引:1,自引:0,他引:1  
本研究应用基于经验模式分解的心电特征提取方法,利用第一本征模函数(intrinsic mode function,IMF)分量对QRS波进行定位,并通过减少分解层数、筛选次数、处理区域等策略实现了快速算法。利用MIT-BIT心律失常数据库的数据进行算法测试,取得较高的检测率,检测速度也有明显提高。实验结果表明,经验模式分解算法在QRS波定位中具有相当的优越性,临床应用中取得了良好的检测效果。  相似文献   
19.
Analyzing the status of T-cell receptor (TCR) gene rearrangements has been an essential part of deciphering the stages of thymocyte development, understanding the β vs. γδ lineage decision, and characterizing T-cell leukemias. Methods such as PCR and quantitative Southern blotting provide useful information, but also have significant shortcomings such as lack of quantitation in the case of PCR and technical challenges in the case of Southern blotting. Here we describe a real-time PCR method that overcomes many of these shortcomings. This new method shows comparable results for the fraction of unrearranged TCRγ and TCRβ genes in human thymocytes and peripheral blood T cells as Southern blotting, and has the advantages of being simple to perform, highly quantitative, and requiring nanogram quantities of DNA. We also describe a real-time PCR method to quantitate T-cell receptor excision circles formed during TCRβ rearrangements.  相似文献   
20.
二尖瓣环的非平面特性对二尖瓣返流的超声诊断和二尖瓣环成形术的合理设计具有重要意义.基于心脏的实时三维超声图像,我们研究了一种对二尖瓣环三维重建及运动分析的方法.首先通过人机交互方式提取出二尖瓣环的特征点,并根据位置关系对特征点排序,然后利用非均匀有理B样条曲线建立二尖瓣环三维形态模型,并编程实现二尖瓣环的动态显示和运动分析.通过对20组病例分析,初步证明此方法所建模型较准确反映患者的二尖瓣环的运动,能满足二尖瓣环三维可视化和分析研究的需要.  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