全文获取类型
收费全文 | 16558篇 |
免费 | 1584篇 |
国内免费 | 432篇 |
专业分类
耳鼻咽喉 | 113篇 |
儿科学 | 152篇 |
妇产科学 | 104篇 |
基础医学 | 2500篇 |
口腔科学 | 424篇 |
临床医学 | 2128篇 |
内科学 | 1014篇 |
皮肤病学 | 263篇 |
神经病学 | 2134篇 |
特种医学 | 3297篇 |
外国民族医学 | 8篇 |
外科学 | 1023篇 |
综合类 | 2027篇 |
预防医学 | 1336篇 |
眼科学 | 337篇 |
药学 | 485篇 |
12篇 | |
中国医学 | 225篇 |
肿瘤学 | 992篇 |
出版年
2024年 | 34篇 |
2023年 | 226篇 |
2022年 | 461篇 |
2021年 | 656篇 |
2020年 | 644篇 |
2019年 | 553篇 |
2018年 | 545篇 |
2017年 | 644篇 |
2016年 | 690篇 |
2015年 | 667篇 |
2014年 | 1131篇 |
2013年 | 1107篇 |
2012年 | 1048篇 |
2011年 | 1095篇 |
2010年 | 896篇 |
2009年 | 865篇 |
2008年 | 1011篇 |
2007年 | 915篇 |
2006年 | 806篇 |
2005年 | 701篇 |
2004年 | 586篇 |
2003年 | 474篇 |
2002年 | 448篇 |
2001年 | 318篇 |
2000年 | 277篇 |
1999年 | 226篇 |
1998年 | 228篇 |
1997年 | 206篇 |
1996年 | 193篇 |
1995年 | 178篇 |
1994年 | 132篇 |
1993年 | 107篇 |
1992年 | 71篇 |
1991年 | 60篇 |
1990年 | 39篇 |
1989年 | 50篇 |
1988年 | 37篇 |
1987年 | 30篇 |
1986年 | 33篇 |
1985年 | 38篇 |
1984年 | 25篇 |
1983年 | 19篇 |
1982年 | 15篇 |
1981年 | 20篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
41.
介绍了一种简单有效的维纳滤波器设计过程,并采用该过程对数字化X射线影像进行滤波,试验表明:维纳滤波器能在去除图像噪声的同时较好地保留图像细节,具有实际应用价值。 相似文献
42.
生理影像是功能性医学影像的一个重要分支,也是临床医学工程的一个极其重要的研究和应用领域。多年来,作者及其研究生与临床医务人员相结合,在电生理影像和热生理影像的信息获取和数字化处理技术方面进行了大量及深入的研究,提出了一种体内热估计(ITE)新技术。本文重点介绍热生理影像信息在妇女乳腺癌诊断中的应用。通过对约五千例妇女乳腺病筛选的结果,表明了生理影像信息处理及ITE技术在临床医学上的应用价值。 相似文献
43.
44.
Leonardo Bonilha MD PhD Paulien M. de Vries Diana J. Vincent MD PhD Chris Rorden MD PhD Paul S. Morgan Mark W. Hurd PhD Nada Besenski MD Kenneth J. Bergmann MD Vanessa K. Hinson MD PhD 《Movement disorders》2007,22(8):1110-1116
We investigated whether structural white matter abnormalities, in the form of disruption of axonal coherence and integrity as measured with diffusion tensor imaging (DTI), constitute an underlying pathological mechanism of idiopathic dystonia (ID), independent of genotype status. We studied seven subjects with ID: all had cervical dystonia as their main symptom (one patient also had spasmodic dysphonia and two patients had concurrent generalized dystonia, both DYT1‐negative). We compared DTI MR images of patients with 10 controls, evaluating differences in mean diffusivity (MD) and fractional anisotropy (FA). ID was associated with increased FA values in the thalamus and adjacent white matter, and in the white matter underlying the middle frontal gyrus. ID was also associated with increase in MD in adjacent white matter to the pallidum and putamen bilaterally, left caudate, and in subcortical hemispheric regions, including the postcentral gyrus. Abnormal FA and MD in patients with ID indicate that abnormal axonal coherence and integrity contribute to the pathophysiology of dystonia. These findings suggest that ID is not only a functional disorder, but also associated with structural brain changes. Impaired connectivity and disrupted flow of information may contribute to the impairment of motor planning and regulation in dystonia. © 2006 Movement Disorder Society 相似文献
45.
Scott Lozanoff Barbara A. Long David L. Singer John J. Deptuch 《Journal of clinical periodontology》1992,19(8):553-559
Deposits of dental plaque or calculus are typically quantified using planimetric techniques. However, error is introduced into a quantitative analysis of plaque deposits using these methods, since they require a significant amount of human intervention. The purpose of this study is to describe and validate a computerized imaging routine which has the potential to objectively identify material on dental roots and measure the area covered by these deposits. Dentiform teeth with simulated plaque were videorecorded. A computer routine was developed based on a flood-fill algorithm which analyzed images of the dentiform teeth and determined the amount of simulated plaque on their root surfaces. Results showed that the dentiform teeth and their simulated plaque patterns are duplicated by the imaging routine in a rapid and reliable fashion. The system shows a high degree of accuracy with an average error factor of only 0.58%. As well, the system enables precise reproducibility with an average error factor of only 0.71%. 相似文献
46.
47.
An image processing system for application to studies of the temporal and spatial parameters of movement during swallowing
and speech is described. Image sequences from videotape are digitized for computerized manipulation and analysis in an attempt
to improve on conventional visual inspection. The system is “interactive” or “event-driven”: after executing a function, the
computer waits for guidance from the user who controls the program through keyboard and mouse input, selecting options from
menus and responding to prompts. The analyst alters image clarity by the application of filters and heightens contrast through
video enhancement. A technique called “remapping” reduces head motion and provides uniform spatial scaling. Animated sequences
of images are used, as opposed to frame-by-frame analysis, to preserve temporal context and increase efficiency of measurement.
Low cost off-the-shelf personal computer hardware is used along with original software tailored to the application. 相似文献
48.
In this paper, a vertical distribution of 137Cs in undisturbed soil was investigated experimentally and theoretically. Soil samples were taken from the surroundings of the city of Kragujevac in central Serbia during spring-summer of 2001. The sampling locations were chosen in such a way that the influence of soil characteristics on depth distribution of 137Cs in soil could be investigated. Activity of 137Cs in soil samples was measured using a HpGe detector and multi-channel analyzer. Based on vertical distribution of 137Cs in soil which was measured for each of 10 locations, the diffusion coefficient of 137Cs in soil was determined. In the next half-century, 137Cs will remain as the source of the exposure. Fifteen years after the Chernobyl accident, and more than 30 years after nuclear probes, the largest activity of 137Cs is still within 10 cm of the upper layer of the soil. This result confirms that the penetration of 137Cs in soil is a very slow process. Experimental results were compared with two different Green functions and no major differences were found between them. While both functions fit experimental data well in the upper layer of soil, the fitting is not so good in deeper layers. Although the curves obtained by these two functions are very close to each other, there are some differences in the values of parameters acquired by them. 相似文献
49.
刘尊年 《菏泽医学专科学校学报》2002,14(4):84-85
目的 探讨血细胞自动计数的方法。方法 采用微机彩色图像处理技术对血液细胞图像进行图像分割和细胞计数。结果 与人工计数相平行 ,相关系数r =0 .96 1~ 0 .997,P >0 .0 5。结论 该方法可行且计数相对精确、迅速、客观 相似文献
50.
A general model is developed for segmenting magnetic resonance images using vector decomposition and probabilfty techniques. Each voxel is assigned fractional volumes of q tissues from p differently weighted images (q ≤ p + 1) in the presence of partial-volume mixing, random noise, and other tissues. Compared wtth the eigenimage method, fewer differently weighted images are needed for segmenting the q tissues, and the contrast-to-noise ratio in the calculated fractional volumes is improved. The model can produce com-posrte tissue-type images similar to that of the probability methods, by comparing the fractional volumes assigned to different tissues on each voxel. A three-tissue (p = 2, q = 3) model is illustrated for segmenting three tissues from dual-echo images. M provides statistical analysis to the algebraic method. A three-compartment phantom is segmented for validation. Two clinical examples are presented. 相似文献