全文获取类型
收费全文 | 3284篇 |
免费 | 492篇 |
国内免费 | 200篇 |
专业分类
化学 | 777篇 |
晶体学 | 73篇 |
力学 | 1146篇 |
综合类 | 35篇 |
数学 | 428篇 |
物理学 | 1517篇 |
出版年
2024年 | 5篇 |
2023年 | 27篇 |
2022年 | 57篇 |
2021年 | 68篇 |
2020年 | 74篇 |
2019年 | 75篇 |
2018年 | 70篇 |
2017年 | 82篇 |
2016年 | 89篇 |
2015年 | 57篇 |
2014年 | 136篇 |
2013年 | 238篇 |
2012年 | 177篇 |
2011年 | 185篇 |
2010年 | 165篇 |
2009年 | 213篇 |
2008年 | 229篇 |
2007年 | 222篇 |
2006年 | 235篇 |
2005年 | 210篇 |
2004年 | 212篇 |
2003年 | 170篇 |
2002年 | 132篇 |
2001年 | 112篇 |
2000年 | 101篇 |
1999年 | 95篇 |
1998年 | 101篇 |
1997年 | 79篇 |
1996年 | 52篇 |
1995年 | 56篇 |
1994年 | 39篇 |
1993年 | 24篇 |
1992年 | 30篇 |
1991年 | 26篇 |
1990年 | 27篇 |
1989年 | 17篇 |
1988年 | 17篇 |
1987年 | 16篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1973年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有3976条查询结果,搜索用时 15 毫秒
31.
We construct a model of a shell with piezoelectric elements (patches) that take into account the mutual influence of deformations and electric fields. Coupled problems for the shell with piezoelectric patches and an acoustic field, are studied and results on the existence and the uniqueness are obtained. For this system we consider an optimal control problem on noise attenuation and obtain results on the existence, the uniqueness, necessary and sufficient conditions of optimality. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
32.
The enthalpies and free energies of proton affinity (PA) were calculated by the PM3 method for 27 thiophenoxide anions. For thiophenols, linear correlation has been found between the PAs and the values of pK
a
measured by different authors in aqueous acetone, aqueous ethanol, and methanol media. The dependences found permit one to predict a priori the protolytic properties of thiophenols. The differential effects of aqueous ethanol media with different ethanol contents on thiophenol acidity were evaluated based on quantum-chemical data.Original Russian Text Copyright © 2004 by A. N. Pankratov and A. V. Shalabai__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 800–806, September–October, 2004. 相似文献
33.
34.
We study a system of quasilinear equations describing one-dimensional flow of a viscous compressible heat-conducting medium with a nonmonotone state function and mass force. The large-time behavior of solutions is considered for arbitrarily large initial data. In spite of possible nonuniqueness and discontinuity of the stationary solution, we prove L2-stabilization for the stress and heat flux as t → ∞ along with corresponding global energy estimates for them. The new method of proof utilizes a combination of energy type equalities for the stress and heat flux. Consequently, H1-stabilization of the velocity and temperature along with global estimates for their derivatives are valid as well. 相似文献
35.
E. G. Tsymbarevich 《Journal of Applied Spectroscopy》2004,71(4):539-545
The propagation of radiation in a three-dimensional, inhomogeneous, stochastic, scattering medium and in an equivalent homogeneous medium has been investigated by the small-angle iteration method. The statistical structure of the scattering parameters of a three-dimensional medium has been described within the framework of the two-dimensional Poisson process and the binary Markov process. The analytical data obtained point to the fact that the three-dimensional inhomogeneity of a stochastic medium significantly influences the radiation transfer in it. 相似文献
36.
Anshu Dandia Kapil Arya Meha Sati Pritima Sarawgi 《Journal of fluorine chemistry》2004,125(9):1273-1277
Reasonable pure fluorinated s-triazines were synthesized in quantitative yield (96-99%) in 2-3 min in aqueous medium under microwaves, by reaction of fluorinated anilines and aqueous formaldehyde. All synthesized compounds have been screened in vitro for their antifungal activity against Rhizoctonia solani, Fusarium oxysporum, and Collectotrichum capsici. 相似文献
37.
Precipitate-forming chemical reactions have been studied in chemically cross-linked poly(vinyl alcohol) gel medium. One of the reactive components was incorporated into the gel, the other was allowed to diffuse into it. Depending on the experimental conditions the reaction-diffusion process often results in patterns of different type. Experiments performed in tubes and in thin layers were carried out in order to investigate the effects of various factors (cross-linking density, swelling degree as well as the concentrations of the outer and inner electrolytes) on the morphologies of the precipitate patterns. It was found that precipitation occurs not only in the Liesegang bands, but also between bands. Beside Liesegang-type structures, tree-like patterns have been observed, showing a characteristic periodicity in the density profile obtained by digitalized image analyses. 相似文献
38.
本文主要论述了0.5MeV,单能垂直入射的电子束在三种不同密度的氟化氪准分子激光介质中的能量沉积。计算是采用Monte Carlo方法的MCSED程序,光轴方向采用周期性边界条件,因此能够给出平行于和垂直于电子束入射方向的沉积能量的空间分布。本文给出了在三种不同密度下的出射电子的角分布。用该程序对垂直入射的,初始能量为1MeV的电子在半无限大Al靶中的沉积能量的计算结果与ONETRAN程序的结果及实验结果的比较表明MCSED程序的计算结果是可靠的。 相似文献
39.
40.
S. Fumeron P. Ben-Abdallah 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,97(2):195-208
The aim of this paper is to present several features of the couplings occurring between radiative transfer and the kinetics of a moving dielectric. After determining how the velocity field affects the apparent thermo-optical properties of matter, the energy transport problem is investigated in instationary regime and the general form of transient radiative transfer equation inside a moving medium is built. Then, the model is applied to the particular case of turbulent flows: a system of two equations for mean and fluctuating radiative energies is presented, and the resolution of this system is finally carried out. 相似文献