全文获取类型
收费全文 | 288篇 |
免费 | 78篇 |
国内免费 | 73篇 |
专业分类
化学 | 144篇 |
晶体学 | 13篇 |
力学 | 58篇 |
综合类 | 19篇 |
数学 | 27篇 |
物理学 | 178篇 |
出版年
2024年 | 2篇 |
2023年 | 7篇 |
2022年 | 12篇 |
2021年 | 13篇 |
2020年 | 7篇 |
2019年 | 17篇 |
2018年 | 14篇 |
2017年 | 13篇 |
2016年 | 16篇 |
2015年 | 14篇 |
2014年 | 27篇 |
2013年 | 19篇 |
2012年 | 13篇 |
2011年 | 11篇 |
2010年 | 15篇 |
2009年 | 20篇 |
2008年 | 15篇 |
2007年 | 18篇 |
2006年 | 11篇 |
2005年 | 20篇 |
2004年 | 14篇 |
2003年 | 8篇 |
2002年 | 5篇 |
2001年 | 5篇 |
2000年 | 13篇 |
1999年 | 18篇 |
1998年 | 10篇 |
1997年 | 9篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1963年 | 1篇 |
1960年 | 1篇 |
1958年 | 1篇 |
1957年 | 2篇 |
1956年 | 1篇 |
1954年 | 1篇 |
1953年 | 1篇 |
排序方式: 共有439条查询结果,搜索用时 15 毫秒
101.
102.
5‘—硝基水杨基荧光酮双波长标准加入分光光度法同时测定?… 总被引:6,自引:0,他引:6
在0.3-0.9mol/L硫酸介质中,在溴化十六烷基三甲铵存在下,5’-硝基水杨基荧光酮与锗和钼形成最大吸收波长分别为513和533nm的红色配合物,其吸收光谱严重重叠。基于此,本文采用双波长标准加入法对该混合物的显色体系进行了研究,建立了同时分光光度测定锗和钼的新方法,并与等吸收双波长法作了比较。 相似文献
103.
Visualizations of Light-induced Refractive Index Changes in Photorefractive Crystals Employing Digital Holography 总被引:4,自引:0,他引:4 下载免费PDF全文
We propose a novel approach to visualize the light-induced refractive index changes in photorefractive crystals employing digital holography. The holograms formed in a Mach-Zehnder interferometer are recorded by a two-dimensional CCD camera. From these holograms, the phase differences, which contain the information of the index changes in photorefractive crystals, are determined by utilizing digital holographic interferometry. Then the two-dimensional visualizations of index changes in the crystals can be obtained. This method is successfully demonstrated in LiNbO3:Fe, KNSBN:Ce and SBN:Cr crystals. 相似文献
104.
Experimental Observation on Orientation Relationship between Binary Cd5.7Yb Quasicrystal and its Crystalline Approximant Cd6Yb 下载免费PDF全文
Similarity in the electron diffraction patterns of the Cd5.7 Yb icosahedral quasicrystal and its cubic approximant Cd6 Yb crystal is studied in detail by using transmission electron microscopy. The icosahedral twofold axes are parallel to the cubic (1ττ^2) (τ= 1.618…) or (0 0 1) directions, the icosahedral pseudo-twofold axes are parallel to the cubic (15 21 25) directions, the icosahedral threefold axes are parallel to the cubic 〈1 1 1〉 and the icosahedral fivefold are parallel to the cubic 〈0 1 τ〉 directions. Based on those observations a general stereographic projection is given to illustrate the exact orientation relationship. 相似文献
105.
Holographic storage scheme based on digital signal processing 总被引:2,自引:0,他引:2
In this paper, a holographic storage scheme for multimedia data storage and retrieval based on the digital signal processing (DSP) is designed. A communication model for holographic storage system is obtained on the analogy of traditional communication system. Many characteristics of holographic storage are embodied in the communication model. Then some new methods of DSP including two-dimensional (2-D) shifting interleaving, encoding and decoding of modulation-array (MA) code and method of soft-decision, etc. are proposed and employed in the system. From the results of experiments it can be seen that those measures can effectively reduce the influence of noise. A segment of multimedia data, including video and audio data, is retrieved successfully after holographic storage by using those techniques. 相似文献
106.
107.
Transport of a Brownian particle moving along the axis of a three-dimensional (313) symmetric and periodic tube is investigated in the presence of asymmetric unbiased forces. It is found that in the presence of entropic barrier, the asymmetry of the unbiased forces is a way of inducing a net particle current. The particle current is a peaked function of temperature, which indicates that the thermal noise may facilitate the transport even in the presence of entropic barrier. There exists an optimized radius at the bottleneck at which the particle current takes its maximum value. The current can be influenced by the slope of tube walls and there exists an optimized slope for which the particle current takes its maximum value. 相似文献
108.
Polymer White-Light-Emitting Diodes with High Work Function Cathode Based on a Novel Phosphorescent Chelating Copolymer 下载免费PDF全文
Polymer white-light-emitting diodes are fabricated based on the blend of poly[9,9-di-(2-ethylhexyl)-fluorenyl-2, 7- diyl]-end capped with polysilsesquioxane (PFO) and a chelating copolymer of poly[(9,9-bis(3′-(N,N-dimethylamino) propyl)-2, 7-fluorene-alt-2, 7-(9,9-dioctylfluorene) )-co- [2, 7-(9,9-dioctlyfluorene)-alt-5,5-bis(2-(4-methyl-l-naphtha- lene) pyridine-C^2,N) iridium (III) acethylacetonate]] (PFN-NaIr). The device with the sole aluminium cathode is able to produce a comparably white electroluminescence efficiency of 1.31 cd/A to that of the device using low work function cathodes (such as Ba, Ca, etc.). The CIE coordinates of the white light emission consisting of red, green and blue three components are nearly at (0.34, 0.35). The mechanism of the white light emission from the device with the AI cathode is investigated, which is related to the efficient injection of electrons through the interface of PFN-Nalr/AI. 相似文献
109.
110.