全文获取类型
收费全文 | 619篇 |
免费 | 38篇 |
国内免费 | 39篇 |
专业分类
耳鼻咽喉 | 3篇 |
儿科学 | 18篇 |
妇产科学 | 3篇 |
基础医学 | 47篇 |
口腔科学 | 58篇 |
临床医学 | 85篇 |
内科学 | 74篇 |
皮肤病学 | 1篇 |
神经病学 | 35篇 |
特种医学 | 103篇 |
外科学 | 24篇 |
综合类 | 16篇 |
预防医学 | 42篇 |
眼科学 | 136篇 |
药学 | 43篇 |
肿瘤学 | 8篇 |
出版年
2023年 | 6篇 |
2022年 | 5篇 |
2020年 | 7篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 9篇 |
2016年 | 5篇 |
2015年 | 12篇 |
2014年 | 15篇 |
2013年 | 13篇 |
2012年 | 11篇 |
2011年 | 22篇 |
2010年 | 7篇 |
2009年 | 11篇 |
2008年 | 17篇 |
2007年 | 31篇 |
2006年 | 22篇 |
2005年 | 38篇 |
2004年 | 16篇 |
2003年 | 16篇 |
2002年 | 29篇 |
2001年 | 12篇 |
2000年 | 18篇 |
1999年 | 7篇 |
1998年 | 23篇 |
1997年 | 14篇 |
1996年 | 15篇 |
1995年 | 21篇 |
1994年 | 9篇 |
1993年 | 23篇 |
1992年 | 23篇 |
1991年 | 22篇 |
1990年 | 21篇 |
1989年 | 40篇 |
1988年 | 16篇 |
1987年 | 24篇 |
1986年 | 21篇 |
1985年 | 12篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 4篇 |
1981年 | 11篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1972年 | 3篇 |
1967年 | 2篇 |
排序方式: 共有696条查询结果,搜索用时 15 毫秒
691.
692.
Optical models of the human eye have been used in visual science for purposes such as providing a framework for explaining optical phenomena in vision, for predicting how refraction and aberrations are affected by change in ocular biometry and as computational tools for exploring the limitations imposed on vision by the optical system of the eye. We address the issue of what is understood by optical model eyes, discussing the ‘encyclopaedia’ and ‘toy train’ approaches to modelling. An extensive list of purposes of models is provided. We discuss many of the theoretical types of optical models (also schematic eyes) of varying anatomical accuracy, including single, three and four refracting surface variants. We cover the models with lens structure in the form of nested shells and gradient index. Many optical eye models give accurate predictions only for small angles and small fields of view. If aberrations and image quality are important to consider, such ‘paraxial’ model eyes must be replaced by ‘finite model’ eyes incorporating features such as aspheric surfaces, tilts and decentrations, wavelength‐dependent media and curved retinas. Many optical model eyes are population averages and must become adaptable to account for age, gender, ethnicity, refractive error and accommodation. They can also be customised for the individual when extensive ocular biometry and optical performance data are available. We consider which optical model should be used for a particular purpose, adhering to the principle that the best model is the simplest fit for the task. We provide a glimpse into the future of optical models of the human eye. This review is interwoven with historical developments, highlighting the important people who have contributed so richly to our understanding of visual optics. 相似文献
693.
694.
Purpose
To give an overview of the misconceptions and potential artefacts associated with measuring peripheral refractive error and eye length, the use of these measures to determine the retinal shape and their links to myopia development. Several issues were identified: the relationship between peripheral refractive error and myopia development, inferring the retinal shape from peripheral refraction or eye length patterns, artefacts and accuracy when measuring peripheral eye length using an optical biometer.Methods
A theory was developed to investigate the influence of artefacts in measuring peripheral eye length and on using peripheral eye length to make inferences about retinal shape.Results
When determining peripheral axial length, disregarding the need to realign instruments with mounted targets can lead to incorrect field angles and positions of mounted targets by more than 10% for targets placed close to the eye. Peripheral eye length is not a good indicator of the effects of myopia or of treatment for myopia development because eyes of different lengths but with the same retinal shape would be interpreted as having different retinal shapes; the measurement leads to overestimates of changes in retinal curvature as myopia increases. Determining peripheral eye length as a function of estimated retinal height rather than field angle will halve the magnitude of the artefact. The artefact resulting from the peripheral use of biometers with an on-axis calibration is modest and can be ignored.Conclusion
There are significant issues with peripheral measurements of the refractive error and eye length that must be considered when interpreting these data for myopia research. Some of these issues can be mitigated, while others require further investigation. 相似文献695.
Dinesh Kaphle Katrina L. Schmid Marwan Suheimat Scott A. Read David A. Atchison 《Ophthalmic & physiological optics》2023,43(3):311-318
Purpose
Eye length increases during accommodation, both on-axis and in the periphery. The aim of this study was to determine whether the peripheral choroid thins with accommodation and to determine the relationship with eye length changes measured at the same location.Methods
Subjects included 53 young adults in good ocular and general health, with 19 emmetropes and 34 myopes. Measurements from the right eye were made for 0 D and 6 D accommodation stimuli for ±30° horizontal visual field/retinal locations in 10° steps. Valid eye length and choroidal thickness measurements were obtained for 37 and 47 participants, respectively, and both measures were taken for 31 participants. 2.5% phenylephrine was instilled to dilate the pupils. Participants turned their eyes, without head movement, to fixate targets and to make the target ‘as clear as possible’ during measurements. Correction was made for the influence of lens thickness changing at different peripheral angles. Choroidal thickness was measured with a spectral-domain-Optical Coherence Tomographer. For peripheral images, the internal cross target on the capture screen was moved from the centre to 17.25° nasal/temporal positions.Results
In accordance with previous literature, eye length increased with accommodation. The greatest change (mean ± SD) of 41 ± 17 μm occurred at the centre, with a mean change across the locations of 33 μm. There were no significant differences between emmetropes and myopes. Choroidal thickness decreased with accommodation, with changes being about two-thirds of those occurring for eye length. The greatest change of −30 ± 1 μm occurred at the centre, with a mean change of −21 μm. Greater choroidal thinning occurred for myopes than for emmetropes (23 ± 11 vs. 17 ± 8 μm, p = 0.02).Conclusions
With accommodation, eye length increased and the choroid thinned, at both central and peripheral positions. Choroidal thinning accounted for approximately 60% of the eye length increase across the horizontal ±30°. 相似文献696.
Flavien Coukan Keitumetse-Kabelo Murray Vasiliki Papageorgiou Adam Lound John Saunders Christina Atchison Helen Ward 《HIV medicine》2023,24(8):893-913