全文获取类型
收费全文 | 1911篇 |
免费 | 49篇 |
国内免费 | 222篇 |
专业分类
化学 | 822篇 |
晶体学 | 14篇 |
力学 | 83篇 |
综合类 | 7篇 |
数学 | 831篇 |
物理学 | 425篇 |
出版年
2023年 | 36篇 |
2022年 | 21篇 |
2021年 | 17篇 |
2020年 | 31篇 |
2019年 | 25篇 |
2018年 | 34篇 |
2017年 | 33篇 |
2016年 | 49篇 |
2015年 | 25篇 |
2014年 | 69篇 |
2013年 | 136篇 |
2012年 | 128篇 |
2011年 | 102篇 |
2010年 | 98篇 |
2009年 | 133篇 |
2008年 | 132篇 |
2007年 | 148篇 |
2006年 | 114篇 |
2005年 | 101篇 |
2004年 | 74篇 |
2003年 | 61篇 |
2002年 | 43篇 |
2001年 | 76篇 |
2000年 | 59篇 |
1999年 | 55篇 |
1998年 | 39篇 |
1997年 | 39篇 |
1996年 | 41篇 |
1995年 | 43篇 |
1994年 | 33篇 |
1993年 | 28篇 |
1992年 | 27篇 |
1991年 | 21篇 |
1990年 | 12篇 |
1989年 | 10篇 |
1988年 | 16篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有2182条查询结果,搜索用时 781 毫秒
1.
In this work, a continuum model is presented for size and orientation dependent thermal buckling and post-buckling of anisotropic nanoplates considering surface and bulk residual stresses. The model with von-Karman nonlinear strains and material cubic anisotropy of single crystals contains two parameters that reflect the orientation effects. Using Ritz method, closed form solutions are given for buckling temperature and post-buckling deflections. Regarding self-instability states of nanoplates and their recovering at higher temperatures, an experiment is discussed based on low pressurized membranes to verify the predictions. For simply supported nanoplates, the size effects are lowest when they are aligned in [100] direction. When the edges get clamped, the orientation dependence is ignorable and the behavior becomes symmetric about [510] axis. The surface residual stress makes drastic increase in buckling temperature of thinner nanoplates for which a minimum thickness is pointed to stay far from material softening at higher temperatures. Deflection of [100]-oriented buckled nanoplates is higher than [110] ones but this reverses at higher temperatures. The results for long nanoplates show that the buckling mode numbers are changed by orientation which is verified by FEM. 相似文献
2.
3.
Kai Xu Zhenchang Tang Yan Zhang Wanshu Li Haiou Li Lihui Wang Liming Liu Honghang Wang Feng Chi Xiaowen Zhang 《Current Applied Physics》2019,19(10):1076-1081
Germanium dioxide (GeO2) aqueous solutions are facilely prepared and the corresponding anode buffer layers (ABLs) with solution process are demonstrated. Atomic force microscopy, X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy measurements show that solution-processed GeO2 behaves superior film morphology and enhanced work function. Using GeO2 as ABL of organic light-emitting diodes (OLEDs), the visible device with tris(8-hydroxy-quinolinato)aluminium as emitter gives maximum luminous efficiency of 6.5 cd/A and power efficiency of 3.5 lm/W, the ultraviolet device with 3-(4-biphenyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole as emitter exhibits short-wavelength emission with peak of 376 nm, full-width at half-maximum of 42 nm, maximum radiance of 3.36 mW/cm2 and external quantum efficiency of 1.5%. The performances are almost comparable to the counterparts with poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) as ABL. The current, impedance, phase and capacitance as a function of voltage characteristics elucidate that the GeO2 ABL formed from appropriate concentration of GeO2 aqueous solution favors hole injection enhancement and accordingly promoting device performance. 相似文献
4.
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
5.
6.
Equilibrium Problems with Applications to Eigenvalue Problems 总被引:5,自引:0,他引:5
In this paper, we consider equilibrium problems and introduce the concept of (S)+ condition for bifunctions. Existence results for equilibrium problems with the (S)+ condition are derived. As special cases, we obtain several existence results for the generalized nonlinear variational inequality studied by Ding and Tarafdar (Ref. 1) and the generalized variational inequality studied by Cubiotti and Yao (Ref. 2). Finally, applications to a class of eigenvalue problems are given. 相似文献
7.
James Murdock 《Journal of Differential Equations》2004,205(2):424-465
Hypernormal forms (unique normal forms, simplest normal forms) are investigated both from the standpoint of foundational theory and algorithms suitable for use with computer algebra. The Baider theory of the Campbell-Hausdorff group is refined, by a study of its subgroups, to determine the smallest substages into which the hypernormalization process can be divided. This leads to a linear algebra algorithm to compute the generators needed for each substage with the least amount of work. A concrete interpretation of Jan Sanders’ spectral sequence for hypernormal forms is presented. Examples are given, and a proof is given for a little-known theorem of Belitskii expressing the hypernormal form space (in the inner product style) as the kernel of a higher-order differential operator. 相似文献
8.
9.
Yan Zhibin 《东北数学》1998,(2)
SomeNotesaboutTanaka'sEquationYanZhibin(严质彬)(DepartmentofMathematics,HarbinInstituteofTechnology,Harbin,150001)AbstractLet{Wt... 相似文献
10.
利用Liapunov函数方法,结合积分不等式技巧,分析了时滞细胞神经网络的平衡点存在的唯一性和全局指数稳定性,保证时滞细胞神经网络全局指数稳定的一个新的充分判据被得到.所得判据比已有文献具有更少的限制,为实际应用提供了方便. 相似文献