全文获取类型
收费全文 | 845篇 |
免费 | 86篇 |
国内免费 | 65篇 |
专业分类
儿科学 | 1篇 |
基础医学 | 111篇 |
口腔科学 | 4篇 |
临床医学 | 28篇 |
内科学 | 43篇 |
皮肤病学 | 7篇 |
神经病学 | 60篇 |
特种医学 | 30篇 |
外科学 | 11篇 |
综合类 | 109篇 |
预防医学 | 49篇 |
眼科学 | 11篇 |
药学 | 246篇 |
中国医学 | 273篇 |
肿瘤学 | 13篇 |
出版年
2024年 | 7篇 |
2023年 | 25篇 |
2022年 | 52篇 |
2021年 | 61篇 |
2020年 | 42篇 |
2019年 | 43篇 |
2018年 | 41篇 |
2017年 | 67篇 |
2016年 | 45篇 |
2015年 | 56篇 |
2014年 | 53篇 |
2013年 | 76篇 |
2012年 | 74篇 |
2011年 | 53篇 |
2010年 | 31篇 |
2009年 | 38篇 |
2008年 | 38篇 |
2007年 | 36篇 |
2006年 | 27篇 |
2005年 | 27篇 |
2004年 | 19篇 |
2003年 | 12篇 |
2002年 | 9篇 |
2001年 | 1篇 |
2000年 | 13篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有996条查询结果,搜索用时 15 毫秒
1.
2.
目的 分析山医群体中国地鼠E家系的遗传纯度。方法 应用经过筛选的 3 1条随机引物对中国地鼠E家系 12只个体基因组DNA进行RAPD扩增 ,计算近交个体间的相似系数。结果 所有样品的相似系数0 943 1到 0 9978之间变动 ,平均相似系数为 0 9749,聚类分析得到了这些个体的同源树资料。结论 山医群体E家系有较高的遗传纯度 相似文献
3.
基于组合不变量配准的数字减影算法 总被引:2,自引:1,他引:1
在现代医学中,DSA是X光片血管可视化技术的重要组成部分之一,在DSA中图像配准对消除运动伪影起着关键作用。运用一种基于组合不变量的相似度测量的模板匹配和弹性TPS算法配准减影方法,并根据实际情况有所改进。经过试验证明这种方法可以自动并有效地去除运动伪影,其速度和血管图像质量均比较理想。 相似文献
4.
S T Flock S L Jacques B C Wilson W M Star M J van Gemert 《Lasers in surgery and medicine》1992,12(5):510-519
Intralipid is an intravenous nutrient consisting of an emulsion of phospholipid micelles and water. Because Intralipid is turbid and has no strong absorption bands in the visible region of the electromagnetic spectrum, and is readily available and relatively inexpensive, it is often used as a tissue simulating phantom medium in light dosimetry experiments. In order to assist investigators requiring a controllable medium that over a finite range of wavelengths is optically equivalent to tissue, we have compiled previously published values of the optical interaction coefficients of Intralipid, most of which were measured at a wavelength of 633 nm. We have extended the measurements of the absorption and reduced scattering coefficients from 460 to 690 nm and the total attenuation coefficient from 500 to 890 nm. These measurements show that, for stock 10% Intralipid, the absorption coefficient varies from 0.015 to 0.001 cm-1 between 460 and 690 nm, the reduced scattering coefficient varies from 92 to 50 cm-1 between 460 and 690 nm, the total attenuation coefficient varies from 575 to 150 cm-1 between 500 and 890 nm, and the average cosine of scatter varies from 0.87 to 0.82 between 460 and 690 nm. With these data, we discuss the design of an optically tissue-equivalent phantom consisting of Intralipid and black India ink. 相似文献
5.
Daniel R. Einstein Blazej Neradilak Nayak Pollisar Kevin R. Minard Chris Wallis Michelle Fanucchi James P. Carson Andrew P. Kuprat Senthil Kabilan Richard E. Jacob Richard A. Corley 《Anatomical record (Hoboken, N.J. : 2007)》2008,291(12):1628-1648
We present the results of an automated analysis of the morphometry of the pulmonary airway trees of the Sprague–Dawley rat. Our work is motivated by a need to inform lower‐dimensional mathematical models to prescribe realistic boundary conditions for multiscale hybrid models of rat lung mechanics. Silicone casts were made from three age‐matched, male Sprague–Dawley rats, immersed in a gel containing a contrast agent and subsequently imaged with magnetic resonance (MR). From a segmentation of this data, we extracted a connected graph, representing the airway centerline. Segment statistics (lengths and diameters) were derived from this graph. To validate this MR imaging/digital analysis method, airway segment measurements were compared with nearly 1,000 measurements collected by hand using an optical microscope from one of the rat lung casts. To evaluate the reproducibility of the MR imaging/digital analysis method, two lung casts were each imaged three times with randomized orientations in the MR bore. Diameters and lengths of randomly selected airways were compared among each of the repeated imaging datasets to estimate the variability. Finally, we analyzed the morphometry of the airway tree by assembling individual airway segments into structures that span multiple generations, which we call branches. We show that branches not segments are the fundamental repeating unit in the rat lung and develop simple mathematical relationships describing these structures for the entire lung. Our analysis shows that airway diameters and lengths have both a deterministic and stochastic character. Anat Rec, 2008. © 2008 Wiley‐Liss, Inc. 相似文献
6.
The Equal Environments Assumption (EEA) in twin studies of eating pathology was investigated by examining the hypothesis that twin resemblance for eating attitudes and behaviors is affected by their degree of physical similarity. Eating attitudes and behaviors were assessed in 338 female adolescent twin pairs with a revised version of the Eating Disorder Inventory (EDI). General physical similarity as well as body size/shape similarity were assessed using ratings of color photographs, ratings of body shape, and body mass index. All physical similarity assessments were conducted blind to twin zygosity. Significant associations between physical similarity and twin similarity for eating attitudes and behaviors were not found. Mean EDI within-twin pair absolute difference scores did not differ significantly among more versus less physically-similar groups. Additionally, correlation and regression analyses failed to find a significant association between EDI absolute difference scores and physical similarity indices. The current findings provide support for the EEA in twin studies of eating attitudes and behaviors. 相似文献
7.
Four-Dimensional Computerized Tomography (4D-CT) Reconstruction Based on the Similarity Measure of Spatial Adjacent Images 总被引:1,自引:0,他引:1
ZHANG Shu-xu ;ZHOU Ling-hong ;CHEN Guang-jie ;LIN Sheng-qu ;YE Yu-sheng ;ZHANG Hai-nan 《中国生物医学工程学报(英文版)》2008,17(3):106-113
Objective:To investigate the feasibility of a 4D-CT reconstruction method based on the similarity principle of spatial adjacent images and mutual information measure. Methods:A motor driven sinusoidal motion platform made in house was used to create one-dimensional periodical motion that was along the longitudinal axis of the CT couch. The amplitude of sinusoidal motion was set to an amplitude of ±1 cm. The period of the motion was adjustable and set to 3.5 s. Phantom objects of two eggs were placed in a Styrofoam block, which in turn were placed on the motion platform. These objects were used to simulate volumes of interest Undergoing ideal periodic motion. CT data of static phantom were acquired using a multi-slice general electric (GE) LightSpeed 16-slice CT scanner in an axial mode. And the CT data of periodical motion phantom were acquired in an axial and cine-mode scan. A software program was developed by using VC + + and VTK software tools to resort the CT data and reconstruct the 4D-CT. Then all of the CT data with same phase were sorted by the program into the same series based on the similarity principle of spatial adjacent images and mutual information measure among them, and 3D reconstruction of different phase CT data were completed by using the software. Results:All of the CT data were sorted accurately into different series based on the similarity principle of spatial adjacent images and mutual information measures among them. Compared with the unsorted CT data, the motion artifacts in the 3 D reconstruction of sorted CT data were re- duced significantly, and all of the sorted CT series result in a 4D-CT that reflected the characteristic of the periodical motion phantom. Conclusion:Time-resolved 4D-CT reconstruction can be implemented with any general multi-slice CT scanners based on the similarity principle of spatial adjacent images and mutual information measure. The process of the 4D-CT data acquisition and reconstruction were not restricted to the hardware or software of the C 相似文献
8.
本研究提出基于EEG序列模糊相似性指数方法预测癫痫发作.首先,结合复自相关法和Cao法对EEG序列进行了相空间重构;然后,计算相关积分时用Gaussian函数代替Heavyside函数,克服了Heavyside函数的刚性边界问题,使得计算相似性指数更加准确和可靠;最后,分析大鼠癫痫EEG信号,检测癫痫发作前期状态.分析结果表明模糊相似性指数方法能够比动态相似性指数方法获得更长的预测时间和更低的错误预测率. 相似文献
9.
The nature of the relationship between social contact and attitude similarity between twins was investigated using longitudinal
data from a sample of Australian twins. Earlier research has suggested that social attitudes are not explained solely by shared
environment; rather there are both genetic and environmental components that explain variance in social attitudes. Using three
types of analyses we investigated the magnitude of the relationship and the direction of causation between attitude similarity
and social contact. Longitudinal analysis of within-pair variance by level of contact suggests that attitude similarity leads
to contact among the females and that similarity is both genetically and environmentally based. Analyses using a crosslag
regression model suggest that similarity causes contact among MZ females. Biometrical analyses indicate differences in direction
of causation for males and females. Among females, both genetic and shared environmental parameter estimates could be equated
across contact groups, suggesting little relationship between contact and similarity. Among males, findings of smaller estimated
heritability in the high-contact group suggest that similarity causes contact. However, an increased estimate of the contribution
of shared environmental variance in the high-contact males could additionally suggest that contact leads to similarity. 相似文献
10.
目的 建立一测多评(quantitative analysis of multicomponents by single-marker,QAMS)法同时检测盐沙苑子饮片中杨梅素、扁蓄苷、杨梅素-3-O-β-D-葡萄糖苷、毛蕊异黄酮葡萄糖苷、西伯利亚落叶松黄酮、沙苑子苷B、沙苑子苷A、毛蕊异黄酮、芒柄花素、鼠李柠檬素、豆甾醇、胡萝卜苷、β-谷甾醇含量的方法,并采用主成分分析法(principal component analysis,PCA)、正交偏最小二乘法-判别分析(orthogonal partial least squares-discriminant analysis,OPLS-DA)法及熵权逼近理想解排序(entropy weight-technique for order preference by similarity to ideal solution,EW-TOPSIS)法对其质量进行评价。方法 采用Lichrospher C18色谱柱;乙腈-0.2%磷酸水溶液为流动相梯度洗脱。以沙苑子苷A为内参物,建立内参物与其他12个待测成分的相对校正因子(relative co... 相似文献