全文获取类型
收费全文 | 9752篇 |
免费 | 2283篇 |
国内免费 | 571篇 |
专业分类
化学 | 1313篇 |
晶体学 | 47篇 |
力学 | 2509篇 |
综合类 | 122篇 |
数学 | 2345篇 |
物理学 | 6270篇 |
出版年
2024年 | 24篇 |
2023年 | 96篇 |
2022年 | 159篇 |
2021年 | 191篇 |
2020年 | 284篇 |
2019年 | 237篇 |
2018年 | 251篇 |
2017年 | 301篇 |
2016年 | 320篇 |
2015年 | 260篇 |
2014年 | 531篇 |
2013年 | 615篇 |
2012年 | 583篇 |
2011年 | 715篇 |
2010年 | 587篇 |
2009年 | 598篇 |
2008年 | 671篇 |
2007年 | 669篇 |
2006年 | 631篇 |
2005年 | 613篇 |
2004年 | 572篇 |
2003年 | 537篇 |
2002年 | 413篇 |
2001年 | 401篇 |
2000年 | 332篇 |
1999年 | 269篇 |
1998年 | 259篇 |
1997年 | 213篇 |
1996年 | 170篇 |
1995年 | 170篇 |
1994年 | 127篇 |
1993年 | 134篇 |
1992年 | 114篇 |
1991年 | 113篇 |
1990年 | 76篇 |
1989年 | 75篇 |
1988年 | 63篇 |
1987年 | 51篇 |
1986年 | 26篇 |
1985年 | 27篇 |
1984年 | 26篇 |
1983年 | 14篇 |
1982年 | 25篇 |
1981年 | 17篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1973年 | 6篇 |
1971年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
V. K. Sharma 《Pramana》1998,51(6):733-742
The alpha-triton relative wave function with various nucleon exchange contributions and their asymptotic normalization are
considered in the framework of the generator coordinate method (GCM). The asymptotic normalization of relative wave function
provide the estimate of the coupling constant. The relative wave function is also used to obtain7Li-α-t vertex function in the virtual decay of7Li. The extrapolation of vertex function for negative values ofq
2 up to the alpha-triton pole provide the vertex constant, which is compared with the experimentally determined estimates 0.67
FM and 0.72 FM. Our calculated value is 0.656 FM which is in close agreement with the above estimates. 相似文献
942.
证明了在一般不计辐射的冲击波阵面后,存在一个热传导波,它的波速完全和冲击波的一致,但阵面后的温度分布有其自己的规律。 相似文献
943.
考虑了加速电场的高次谐波的影响,解析地分析了电子在驻波腔内的运动过程,给出了电场分布,与数值模拟计算的电场分布比较吻合。讨论了高次谐波对电子束横向运动的影响,利用此解析解可选择高亮度注入器腔的最优电场分布。并得出射频驻波腔内电子束在β趋于1时射频场效应趋于零的结论。 相似文献
944.
Based on the linear viscoelastic differential constitutive law and cable structural model, the coupled longitudinal-transverse
waves that propagate along a viscoelastic cable with small curvature is investigated. A mathematical model is presented that
describes the three-dimensional nonlinear response of a viscoelastic cable. An asymptotic form of this model is obtained for
the linear response of cables having small equilibrium curvature. The spectral relation governing the propagating waves is
derived using transform methods. The spectral relation is employed in deriving a Green's function that is then used to construct
solutions for in-plane response under distributed harmonic excitation. Analysis of forced response reveals the existence of
two types of periodic waves that propagate through the cable, one characterizing extension-comprehensive deformation and the
other characteristic transverse deformation.
Project supported by the National Natural Science Foundation of China (No. 59635140). 相似文献
945.
本文将自耦调压器与升压变压器相结合,设计出了一种1000V可调脉动直流电源,构思独特,可广泛应用于可调高压大功率电源的设计。 相似文献
946.
Shi-Hai Dong 《Foundations of Physics Letters》2002,15(4):385-395
In this letter, by applying a suitable ansatz to the wave functions, the solutions of the D-dimensional radial Schrödinger equation with some anharmonic potentials are obtained. 相似文献
947.
利用表象变换方法,对含逆场算符的J-C模型,分别在相互作用表象中和薛定谔表象中求出了系统的演化波函数,并讨论了失谐量为零时的拉比振动. 相似文献
948.
Distributed point source method (DPSM) is gradually gaining popularity in the field of non-destructive evaluation (NDE). DPSM is a semi-analytical technique that can be used to calculate the ultrasonic fields produced by transducers of finite dimension placed in homogeneous or non-homogeneous media. This technique has been already used to model ultrasonic fields in homogeneous and multi-layered fluid structures. In this paper the method is extended to model the ultrasonic fields generated in both fluid and solid media near a fluid-solid interface when the transducer is placed in the fluid half-space near the interface. Most results in this paper are generated by the newly developed DPSM technique that requires matrix inversion. This technique is identified as the matrix inversion based DPSM technique. Some of these results are compared with the results produced by the Rayleigh-Sommerfield integral based DPSM technique. Theory behind both matrix inversion based and Rayleigh-Sommerfield integral based DPSM techniques is presented in this paper. The matrix inversion based DPSM technique is found to be very efficient for computing the ultrasonic field in non-homogeneous materials. One objective of this study is to model ultrasonic fields in both solids and fluids generated by the leaky Rayleigh wave when finite size transducers are inclined at Rayleigh critical angles. This phenomenon has been correctly modelled by the technique. It should be mentioned here that techniques based on paraxial assumptions fail to model the critical reflection phenomenon. Other advantages of the DPSM technique compared to the currently available techniques for transducer radiation modelling are discussed in the paper under Introduction. 相似文献
949.
We derive a simple expression, which gives an approximate value of the Rayleigh wave velocity in an isotropic solid. This approximation is five times better than that given by Viktorov. The velocity equation can be easily inverted in order to obtain an accurate determination of the elastic constants. This procedure can be worthwhile for elastic microanalysis of bulk materials by scanning acoustic microscopy. 相似文献
950.
This paper deals with the exact boundary controllability and the exact boundary synchronization for a 1-D system of wave equations coupled with velocities. These problems can not be solved directly by the usual HUM method for wave equations, however, by transforming the system into a first order hyperbolic system, the HUM method for 1-D first order hyperbolic systems, established by Li-Lu(2022) and Lu-Li(2022), can be applied to get the corresponding results. 相似文献