全文获取类型
收费全文 | 39002篇 |
免费 | 6038篇 |
国内免费 | 5817篇 |
专业分类
化学 | 29063篇 |
晶体学 | 530篇 |
力学 | 2038篇 |
综合类 | 533篇 |
数学 | 4772篇 |
物理学 | 13921篇 |
出版年
2024年 | 83篇 |
2023年 | 474篇 |
2022年 | 1003篇 |
2021年 | 1103篇 |
2020年 | 1245篇 |
2019年 | 1287篇 |
2018年 | 1140篇 |
2017年 | 1084篇 |
2016年 | 1690篇 |
2015年 | 1825篇 |
2014年 | 2221篇 |
2013年 | 2888篇 |
2012年 | 3248篇 |
2011年 | 3459篇 |
2010年 | 2601篇 |
2009年 | 2577篇 |
2008年 | 2948篇 |
2007年 | 2705篇 |
2006年 | 2529篇 |
2005年 | 2125篇 |
2004年 | 1853篇 |
2003年 | 1538篇 |
2002年 | 1774篇 |
2001年 | 1332篇 |
2000年 | 1106篇 |
1999年 | 859篇 |
1998年 | 587篇 |
1997年 | 554篇 |
1996年 | 474篇 |
1995年 | 406篇 |
1994年 | 360篇 |
1993年 | 330篇 |
1992年 | 280篇 |
1991年 | 219篇 |
1990年 | 197篇 |
1989年 | 161篇 |
1988年 | 118篇 |
1987年 | 103篇 |
1986年 | 67篇 |
1985年 | 78篇 |
1984年 | 43篇 |
1983年 | 29篇 |
1982年 | 20篇 |
1981年 | 22篇 |
1980年 | 19篇 |
1979年 | 9篇 |
1978年 | 25篇 |
1977年 | 10篇 |
1976年 | 12篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
141.
Yong Wang 《International Journal of Infrared and Millimeter Waves》1995,16(11):2011-2017
The high frequency scattering of TE wave from a dielectric-coated conducting cylinder is obtained via the geometrical theory of diffraction. The high frequency ray solution is computed numerically by the methods of residue series, Taylor series and stationary phase in shadow, transition and illuminated region, respectively. The numerical results of the high frequency ray solution show good agreement with the eigenfunction results. 相似文献
142.
Yong Nam Choi Shin Ae Kim Sung Kyu Kim Sung Baek Kim Chang-Hee Lee Pavel Mikula 《Pramana》2004,63(1):175-181
In a conventional diffractometer having single monochromator, only one position, parallel position, is used for the diffraction
experiment (i.e. detection) because the resolution property of the other one, anti-parallel position, is very poor. However,
a bent perfect crystal (BPC) monochromator at monochromatic focusing condition can provide a quite flat and equal resolution
property at both parallel and anti-parallel positions and thus one can have a chance to use both sides for the diffraction
experiment. From the data of the FWHM and the Δd/d measured on three diffraction geometries (symmetric, asymmetric compression and asymmetric expansion), we can conclude that
the simultaneous diffraction measurement in both parallel and anti-parallel positions can be achieved. 相似文献
143.
A novel type of corner reflector for the reflection of surface plasmon polariton (SPP) is proposed. The reflector consists
of two layers of compensatory media whose permittivity and permeability take opposite signs to that of the corresponding layer
of the SP waveguide. By rigorously solving Maxwell's equations, the reflected SPP is proved to exist. The transverse wave
vector of the reflected SPP is always antiparallel to that of the incident SPP and no phase retardation is introduced. 相似文献
144.
主要介绍了丝绸之路上多元文化的典型代表——艾德莱斯绸.文章重点介绍了艾德莱斯绸的历史和传说,扎经染色工艺,各类艾德莱斯绸的特点及典型的艾德莱斯绸图案. 相似文献
145.
Mach-Zehnder干涉仪适用于研究气体密度迅速变化的状态。由于气体折射率的变化与其密度的变化成正比,而折射率的变化将使通过气体的光线有不同的光程,因此可通过干涉臂变化对干涉条纹图像效果的影响得到气体密度。实测中,采用图像采集卡和CCD来接收Mach-Zehnder干涉仪产生的条纹图像,再通过计算机对条纹图像的条纹间距进行处理,从而得到气体密度的变化状态。从光干涉理论出发,对Mach-Zehnder干涉条纹图像特征进行了分析,建立了Mach-Zehnder干涉条纹的数学模型,并根据此模型设计了处理Mach-Zehnder干涉条纹图像的算法。算法包括图像的预处理(即图像的噪声提取)、图像的二值化及图像的细化。 相似文献
146.
Longlan Cui Hong Xu Ping He Keiko Sumitomo Yoshinori Yamaguchi Hongchen Gu 《Journal of polymer science. Part A, Polymer chemistry》2007,45(22):5285-5295
A hybrid emulsion polymerization was formulated for synthesizing Fe3O4/polystyrene composite latex. This system, containing binary droplets that are magnetic (Mag)‐droplets with a diameter of 100–200 nm and styrene (St)‐droplets with a diameter of 3–4 μm, was obtained by mixing Mag‐miniemulsion and St‐macroemulsion. With extremely low surfactants concentration (?critical micelle concentration, CMC), the nucleated loci are selectively controlled in the Mag‐droplets, as the result of smaller droplet size and larger surface ratio. Both water‐soluble potassium persulfate (KPS) and oil‐soluble 2,2′‐azobis(2‐isobutyronitrile) was adopted to initiate the polymerization. In the presence of KPS, magnetic polystyrene latices with particles size of 60–200 nm, narrow size distribution, and high magnetite content (86 wt % measured by TGA) were attained successfully. The synthesized magnetic Fe3O4/polystyrene latices assembled into well‐ordered hexagonal structure in the surface of a carbon supported copper grid. The influence of various parameters on various aspects of the as‐synthesized Fe3O4/polystyrene was investigated in detail: type of initiator on composite morphology, feed ratio of Mag‐miniemulsion and St‐macroemulsion on magnetite content, and hydrophobic agent or amount of surfactant on size and size distribution. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5285–5295, 2007 相似文献
147.
148.
Several functionalized β-diketones and their europium complexes have been synthesized and characterized. The UV-Vis absorption, photoluminescent spectra, thermal and electrochemical properties of these complexes were investigated. The thermal analysis shows that the complexes have good thermal stability. By introducing the number of extended phenyl rings we succeeded in obtaining europium complexes with extremely high photoluminescent quantum yield (PLQY) in solution due to strong site isolation effect. 相似文献
149.
等腰三角形Mindlin板的自由振动分析 总被引:2,自引:0,他引:2
提出了一种新方法来对基于 Mindlin剪切变形理论的等腰三角形板进行自由振动分析 .此方法采用了一种新的基函数并利用 pb-2 Rayleigh-Ritz边界函数得到了一种新型的 Ritz方法 .这种方法的有效性通过收敛性和对比性分析得到了证实 .数值结果表明此方法相当精确有效 . 相似文献
150.
Bing Yong HSIE 《数学学报(英文版)》2006,22(2):507-514
This paper gives a p-adic analogue of the Mackey theory, which relates representations of a group of type G - H × t A to systems of imprimitivity. 相似文献