全文获取类型
收费全文 | 1648篇 |
免费 | 249篇 |
国内免费 | 49篇 |
专业分类
化学 | 137篇 |
晶体学 | 5篇 |
力学 | 18篇 |
综合类 | 9篇 |
数学 | 31篇 |
物理学 | 1347篇 |
综合类 | 399篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 17篇 |
2021年 | 22篇 |
2020年 | 19篇 |
2019年 | 9篇 |
2018年 | 25篇 |
2017年 | 32篇 |
2016年 | 55篇 |
2015年 | 48篇 |
2014年 | 119篇 |
2013年 | 70篇 |
2012年 | 118篇 |
2011年 | 78篇 |
2010年 | 70篇 |
2009年 | 82篇 |
2008年 | 90篇 |
2007年 | 107篇 |
2006年 | 77篇 |
2005年 | 101篇 |
2004年 | 85篇 |
2003年 | 87篇 |
2002年 | 96篇 |
2001年 | 71篇 |
2000年 | 56篇 |
1999年 | 55篇 |
1998年 | 48篇 |
1997年 | 45篇 |
1996年 | 37篇 |
1995年 | 41篇 |
1994年 | 39篇 |
1993年 | 30篇 |
1992年 | 23篇 |
1991年 | 25篇 |
1990年 | 24篇 |
1989年 | 14篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有1946条查询结果,搜索用时 15 毫秒
101.
102.
用光线矩阵方法推导了光纤-自聚焦棒-反射器在共轴耦合情况下的后向耦合系数;分析了它与耦合系统结构参数之间的关系.用计算机模拟画出了反射器为平面镜的系统的后向耦合系数和后向耦合损耗的曲线分布,计算曲线与实验结果大致符合. 相似文献
103.
固体浸没透镜飞行高度的气浮控制 总被引:3,自引:3,他引:0
采用固体浸没透镜的光存储方法是提高光存储密度的比较实用的近场光存储方法,而严格控制SIL下底面与光存储介质之间的亚波长级距离是此光存储系统正常工作的前提.本文采用电容法测量SIL的飞行高度,采用弹性悬臂将SIL加载在转盘表面上,转盘以不同速度转动时SIL将悬浮在不同的高度.计算机首先采集到SIL的飞行高度信息,再与设定的飞行高度作比较,根据比较结果调整转盘转速,从而达到调整SIL飞行高度的目的.采用此方法,可以动态地将SIL的下底面控制在距高速转动的转盘表面上150~600 nm范围内的一定高度上. 相似文献
104.
105.
《中国物理 B》2021,30(10):104702-104702
Transmission beam can be modulated at the liquid–liquid interface inside an electrowetting liquid lens. The fluctuation characteristics of the interface has a decisive effect on the beam modulation. A closed cylinder in capillary constant scale is analyzed and the natural frequencies of a flat interface are obtained using capillary wave hydrodynamics. Results in modes0 and 1 are in good agreement with previous experiments in the literature. The influences of the radius, the height ratio and the height-to-diameter ratio of a liquid lens on the interface eigenfrequencies are analyzed. 相似文献
106.
廖立新 《吉首大学学报(自然科学版)》2015,36(4):30-32
对传统自准直法的凹透镜焦距测量方法进行了分析,提出改进的自准直测凹透镜焦距方法.将移像屏法改进为移凹透镜法,消除了焦深对实验测量结果的影响.实验结果表明,修正的自准直法测量凹透镜焦距的精确度得到较大提高,平均相对误差减少3.93%,方差减小20.39mm2. 相似文献
107.
Thermal effects are very much influential in high power beam generators. Their impacts on special types of beams such as Helmholtz-Gauss beams have attracted special attentions. This work reports thermal effects on the generation and propagation of Ince-Gaussian beams. The results show considerable beam spot size variations for near fields under various induced heat loads. As Ince-Gaussian beams are directly related to cavity symmetry breaking, the results can greatly help system designers for circumventing these types of symmetry breaks usually encountered in high power lasers. 相似文献
108.
Hui-Chuan Cheng 《Optics Communications》2011,284(8):2118-2121
We report an adaptive mechanical-wetting lens actuated by ferrofluids. The ferrofluids works like a piston to pump liquids in and out from the lens chamber, which in turn reshapes the lens curvature and changes the focal length. Both positive and negative lenses are demonstrated experimentally. The ferrofluid-actuated mechanical-wetting lens exhibits some attractive features, such as high resolution, fast response time, low power consumption, simple structure and electronic control, weak gravity effect, and low cost. Its potential applications in medical imaging, surveillance, and commercial electronics are foreseeable. 相似文献
109.
Wentao Jin 《Optics Communications》2011,284(24):5814-5817
We fabricate three-dimensional nonlinear photonic lattices in iron-doped lithium niobate photorefractive crystal for the first time by a single amplitude mask. The experimental setup of this method is very simple and flexible. The period of the lattices can be dominated easily. We analyze the three-dimensional photonic lattices by plane wave guiding and far field diffraction pattern imaging. The induced photonic lattices can exist stably for a long time in the photorefractive crystal. 相似文献
110.
Autostereoscopic display based on multi-layer lenticular lens 总被引:1,自引:0,他引:1
An autostereoscopic display based on a multi-layer lenticular lens was proposed. The autostereoscopic display is composed of a flat panel display and a multi-layer lenticular lens sheet, which includes a traditional single lenticular lens and an additional transparent layer. The focal length of the multi-layer lenticular lens can be changed by choosing the refractive index of the additional transparent layer to adjust the stereoscopic depth, and it is an easier and much more flexible way than changing lenticular lens's curvature radius. A 22-in. 9-view autostereoscopic display prototype was developed. The image crosstalk of the prototype is very small and it has good presentation to several viewers without wearing eyeglasses. 相似文献