全文获取类型
收费全文 | 10826篇 |
免费 | 2285篇 |
国内免费 | 837篇 |
专业分类
化学 | 1352篇 |
晶体学 | 151篇 |
力学 | 1101篇 |
综合类 | 55篇 |
数学 | 367篇 |
物理学 | 6291篇 |
无线电 | 4631篇 |
出版年
2024年 | 31篇 |
2023年 | 96篇 |
2022年 | 154篇 |
2021年 | 157篇 |
2020年 | 244篇 |
2019年 | 209篇 |
2018年 | 186篇 |
2017年 | 248篇 |
2016年 | 301篇 |
2015年 | 337篇 |
2014年 | 622篇 |
2013年 | 542篇 |
2012年 | 612篇 |
2011年 | 875篇 |
2010年 | 646篇 |
2009年 | 769篇 |
2008年 | 810篇 |
2007年 | 864篇 |
2006年 | 862篇 |
2005年 | 639篇 |
2004年 | 607篇 |
2003年 | 545篇 |
2002年 | 459篇 |
2001年 | 460篇 |
2000年 | 376篇 |
1999年 | 372篇 |
1998年 | 355篇 |
1997年 | 294篇 |
1996年 | 234篇 |
1995年 | 203篇 |
1994年 | 175篇 |
1993年 | 148篇 |
1992年 | 118篇 |
1991年 | 85篇 |
1990年 | 81篇 |
1989年 | 56篇 |
1988年 | 48篇 |
1987年 | 23篇 |
1986年 | 12篇 |
1985年 | 13篇 |
1984年 | 18篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1966年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 750 毫秒
1.
Textured surface is commonly used to enhance the efficiency of silicon solar cells by reducing the overall reflectance and improving the light scattering. In this study, a comparison between isotropic and anisotropic etching methods was investigated. The deep funnel shaped structures with high aspect ratio are proposed for better light trapping with low reflectance in crystalline silicon solar cells. The anisotropic metal assisted chemical etching (MACE) was used to form the funnel shaped structures with various aspect ratios. The funnel shaped structures showed an average reflectance of 14.75% while it was 15.77% for the pillar shaped structures. The average reflectance was further reduced to 9.49% using deep funnel shaped structures with an aspect ratio of 1:1.18. The deep funnel shaped structures with high aspect ratios can be employed for high performance of crystalline silicon solar cells. 相似文献
2.
We use photoluminescence to observe light-induced degradation in silicon in real time. Numerical simulations are used to match our results and lifetime decay data from the literature with theoretical models for the generation of the light-induced boron–oxygen defects. It is found that the existing model of the slowly generated defect SRC, where its saturated concentration is a function of the majority carrier concentration, does not explain certain results in both p- and n-type samples. A new model is proposed in which the saturated SRC concentration is controlled by the total hole concentration under illumination. 相似文献
3.
提供了一种简便易行的靶面激光光斑尺寸原位测量的方法。从高斯光束的横向光强分布特性出发,建立了激光烧蚀斑半径与辐照激光能量、光斑尺寸、烧蚀阈值间的关系式,模拟分析发现辐照激光光斑尺寸对烧蚀斑半径随辐照能量变化曲线有较大影响。对于脉宽为2 ms,波长为1064 nm的激光,实验测量了不同能量激光辐照下相纸烧蚀斑半径,并用推导出的关系式拟合测量数据,获得了靶面处光斑尺寸和样品烧蚀阈值。同时,也测量了不同位置处的光斑尺寸和样品烧蚀阈值,对高斯光束束腰位置和样品烧蚀阈值的光斑尺寸效应进行了验证。研究结果表明该技术结果可靠,简单高效。该技术可以为高能激光与固体物质相互作用的基础研究和激光加工等应用领域中实现简单方便地测量靶面光斑尺寸提供帮助。 相似文献
4.
5.
6.
1 Introduction High power laser diode arrays (LDA) have many advan- tages such as small volume, long working life, high slope efficiency and high optical density, so they have many applications in medical treatment, material pro- cessing, and for the pumping source of solid laser and etc. But unfortunately, the LDA can not be easy to use directly in these fields because of their poor beam quality and extremely asymmetric divergent beams (!x≈ 5°~10°and !y≈20°~35°, for example), so it … 相似文献
7.
A simple template‐free high‐temperature evaporation method was developed for the growth of crystalline Si microtubes for the first time. As‐grown Si microtubes were characterized using X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and room‐temperature photoluminescence. The lengths of the Si tubes can reach several hundreds of micrometers; some of them have lengths on the order of millimeters. Each tube has a uniform outer diameter along its entire length, and the typical outer diameter is ≈ 2–3 μm. Most of the tubes have a wall thickness of ≈ 400–500 nm, though a considerable number of them exhibit a very thin wall thickness of ≈ 50 nm. Room‐temperature photoluminescence measurement shows the as‐synthesized Si microtubes have two strong emission peaks centered at ≈ 589 nm and ≈ 617 nm and a weak emission peak centered at ≈ 455 nm. A possible mechanism for the formation of these Si tubes is proposed. We believe that the present discovery of the crystalline Si microtubes will promote further experimental studies on their physical properties and smart applications. 相似文献
8.
9.
10.
入射光的偏振和强度对分光镜透/反比的影响 总被引:3,自引:0,他引:3
采用能量流分析法推导了一束线偏振光经分光镜分光形成透射/反射光的能量表达式。分别讨论了入射光强度不变而偏振方向变化以及二者同时变化对分光镜透/反比的影响。通过旋转主光路中的偏振片来模拟入射光的偏振方向和强度变化,实验验证了分光比的变化规律。 相似文献