全文获取类型
收费全文 | 107309篇 |
免费 | 8496篇 |
国内免费 | 8066篇 |
专业分类
化学 | 33248篇 |
晶体学 | 2166篇 |
力学 | 4799篇 |
综合类 | 562篇 |
数学 | 34640篇 |
物理学 | 48456篇 |
出版年
2023年 | 470篇 |
2022年 | 801篇 |
2021年 | 797篇 |
2020年 | 1340篇 |
2019年 | 1739篇 |
2018年 | 1678篇 |
2017年 | 1321篇 |
2016年 | 1172篇 |
2015年 | 1116篇 |
2014年 | 2258篇 |
2013年 | 3604篇 |
2012年 | 2281篇 |
2011年 | 3422篇 |
2010年 | 3729篇 |
2009年 | 8496篇 |
2008年 | 9765篇 |
2007年 | 8308篇 |
2006年 | 7266篇 |
2005年 | 5200篇 |
2004年 | 4803篇 |
2003年 | 4953篇 |
2002年 | 6153篇 |
2001年 | 4536篇 |
2000年 | 4208篇 |
1999年 | 4009篇 |
1998年 | 3339篇 |
1997年 | 2490篇 |
1996年 | 2230篇 |
1995年 | 2623篇 |
1994年 | 2579篇 |
1993年 | 1996篇 |
1992年 | 1456篇 |
1991年 | 1111篇 |
1990年 | 944篇 |
1989年 | 886篇 |
1988年 | 786篇 |
1987年 | 645篇 |
1986年 | 404篇 |
1985年 | 1191篇 |
1984年 | 845篇 |
1983年 | 634篇 |
1982年 | 769篇 |
1981年 | 881篇 |
1980年 | 795篇 |
1979年 | 610篇 |
1978年 | 640篇 |
1977年 | 569篇 |
1976年 | 578篇 |
1974年 | 372篇 |
1973年 | 474篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
J. E. Fischer E. Werwa P. A. Heiney 《Applied Physics A: Materials Science & Processing》1993,56(3):193-196
We have used both reflection-geometry and grazing-incidence-geometry X-ray scattering to study thin films of C60 evaporated onto mica substrates via a hot-wall technique. The growth mode yields close-packed C60 planes, which are parallel to the substrate surface and which exhibit out-of-plane correlation lengths of 850 Å. In the film plane the C60 is at best pseudo-epitaxial, with a 0.9° distribution of crystallite orientations, a 450 Å in-plane correlation length, and a 3.7% lattice mismatch, better than obtained by other thin film techniques but far from the accepted definition of single crystal thin film epitaxy. 相似文献
62.
本文研究作为双层桥模型的梁方程耦合系统,利用Leray-Schauder不动点定理,得到了一个关于这种系统的解的存在性定理,它类似于McKenna和Walter文2中关于吊桥方程的一个定理。 相似文献
63.
64.
65.
V. Palyok I.A. Szabó D.L. Beke A. Kikineshi 《Applied Physics A: Materials Science & Processing》2002,74(5):683-687
Surface relief formation at holographic recording on amorphous selenium films was demonstrated and investigated. The presence
of this optical phase modulation component is essential for ensuring significant, stable and erasable optical recording in
a-Se films at 290–320 K temperatures, where conventional photodarkening was known as insignificant and unstable. Photocrystallization
can only be observed in super-exposed a-Se films at the given experimental conditions of hologram recording. Erasing behavior
of surface relief gratings under heat treatment was also investigated in order to reveal further details of the mechanism.
Photoinduced structural transformations within the amorphous phase, connected to local ordering under the condition of light-induced
fluidity, are proposed as an explanation for the relief formation and erasing. The observed reversible optical recording process
may be useful for the various optoelectronic applications of photoconductive a-Se layers.
Received: 12 June 2000 / Accepted: 6 June 2001 / Published online: 30 August 2001 相似文献
66.
67.
Surface texturing has been recognized as an effective means to improve the tribological performances of sliding surfaces. Usually, generation additional hydrodynamic pressure to increase the load carrying capacity is regarded as the most significant effect of surface texture. In the case of silicon carbide sliding against identical material in water, the experimental results indicate that surface texture is also helpful to improve the running-in progress to smooth the contact surfaces, showing another reason to result in low friction. Based on the consideration of enhancing the generation of hydrodynamic pressure and improving running-in progress, a surface texture pattern, which was combined with large (circle, 350 μm in diameter) and small (rectangular, 40 μm in length) dimples, was designed to maximize the texture effect on the load carrying capacity of SiC surfaces sliding in water. The friction coefficient of such textured surface was evaluated and compared with that of untextured and those only with large or small dimples only. The friction reduction mechanisms of the patterns with different dimples in size are discussed. 相似文献
68.
Rajiv Manohar G. Tripathi A.K. Srivastava A.K. Prajapati 《Journal of Physics and Chemistry of Solids》2006,67(11):2300-2304
Dielectric properties of polymer-liquid crystal mixture, having constituent polymer, poly-butyl methacrylate (PBMA) and liquid crystal, cholesteryl nonanoate, are reported as a function of frequency and temperature. The measurement has been done in a temperature range of 300-375 K and frequency range of 100 Hz-10 MHz. The dielectric permittivity and dielectric loss shows significant changes with the addition of polymer molecules in liquid crystal. The significant feature of composite formation is that the pure liquid crystal and polymer do not show dielectric relaxation in the frequency range covered, while the composite shows relaxation peak at a particular frequency. The optical transmittance of pure liquid crystal and composite has also been measured and compared. 相似文献
69.
Lin Surong 《Annals of Differential Equations》2006,22(4):517-523
The singularly perturbed boundary value problem for nonlinear higher order ordinary differential equation involving two small parameters has been considered. Under appropriate assumptions, for the three cases:ε/μ2→0(μ→0),μ2/ε→0 (ε→0) andε=μ2, the uniformly valid asymptotic solution is obtained by using the expansion method of two small parameters and the theory of differential inequality. 相似文献
70.
Mark L. Agranovsky E. K. Narayanan 《Proceedings of the American Mathematical Society》2006,134(7):2117-2123
A test for a function to be a solution of an elliptic PDE is given in terms of extensions, as solutions, from the boundaries inside the domains belonging to an isotopic family. It generalizes a result of Ehrenpreis for spheres moved along a straight line.