全文获取类型
收费全文 | 8863篇 |
免费 | 1151篇 |
国内免费 | 718篇 |
专业分类
化学 | 3256篇 |
晶体学 | 37篇 |
力学 | 1399篇 |
综合类 | 172篇 |
数学 | 1489篇 |
物理学 | 4379篇 |
出版年
2024年 | 16篇 |
2023年 | 75篇 |
2022年 | 189篇 |
2021年 | 193篇 |
2020年 | 206篇 |
2019年 | 198篇 |
2018年 | 203篇 |
2017年 | 283篇 |
2016年 | 317篇 |
2015年 | 332篇 |
2014年 | 414篇 |
2013年 | 654篇 |
2012年 | 494篇 |
2011年 | 539篇 |
2010年 | 413篇 |
2009年 | 492篇 |
2008年 | 519篇 |
2007年 | 571篇 |
2006年 | 449篇 |
2005年 | 457篇 |
2004年 | 455篇 |
2003年 | 397篇 |
2002年 | 359篇 |
2001年 | 251篇 |
2000年 | 259篇 |
1999年 | 222篇 |
1998年 | 240篇 |
1997年 | 210篇 |
1996年 | 154篇 |
1995年 | 150篇 |
1994年 | 116篇 |
1993年 | 108篇 |
1992年 | 91篇 |
1991年 | 72篇 |
1990年 | 70篇 |
1989年 | 66篇 |
1988年 | 57篇 |
1987年 | 55篇 |
1986年 | 42篇 |
1985年 | 47篇 |
1984年 | 43篇 |
1983年 | 13篇 |
1982年 | 43篇 |
1981年 | 47篇 |
1980年 | 23篇 |
1979年 | 22篇 |
1978年 | 25篇 |
1977年 | 18篇 |
1976年 | 21篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
A. V. Sokolov 《Russian Chemical Bulletin》1992,41(10):1750-1755
The concept of the apparent electronegativity of a reaction site has been introduced. This has been used to develop a new scheme for calculating the relative rate constants of addition of radicals with different structures to vinyl monomers. The parameters of the scheme are given for 40 reagents. The results of a comparison of calculated and literature rate constants of addition are presented.Institute of Nonaqueous Solution Chemistry, Russian Academy of Sciences, 150003 Ivanovo. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2238–2245, October, 1992. 相似文献
72.
Jerzy Cioslowski 《Theoretical chemistry accounts》1992,81(4-5):319-327
Summary A new index, called the differential density matrix overlap (DDMO), is proposed for assessment of the electron correlation effects in atoms and molecules. DDMO can be easily calculated as the negative value of the correlation energy derivative with respect to the relative position of the occupied and virtual orbitals. DDMO is transparent to physical interpretation. It can serve as a tool for analyzing the accuracy of approximate electron correlation methods and the validity of the Hartree-Fock wavefunction as the zeroth-order approximation. The properties of DDMO are discussed using test calculations on 11 atoms and molecules as an example. 相似文献
73.
We investigate a multicomponent anisotropic liquid system. The first spatial moment of the direct correlation function is taken into account to obtain asymptotic expressions for the pairwise correlation functions. In this approximation, we obtain the pairwise correlation functions that describe the system behavior not only in the critical-state neighborhood but also in the noncritical domain. We show that the critical parameters for the anisotropic system differ from those for the isotropic system. 相似文献
74.
Z.J. Liu H.H. Long W.C. Ye X.X. Zou Z.L. Qin E.P. Li J.S. Chen 《Journal of magnetism and magnetic materials》2006
In this paper, specific issues related to high-density perpendicular magnetic recording processes, such as transition noise properties and cross-track correlation lengths, were investigated with the help of micromagnetic analysis. The effects of media parameters were taken into consideration, including intergranular exchange coupling, and exchange distribution, irregular grain shapes, magnetization saturation distribution, and anisotropy distribution. The micromagnetic simulation results showed that the effect of anisotropy distribution on transition noise is more significant than magnetization saturation distribution, and it is crucial to reduce this effect to achieve a high signal-to-noise ratio. Additionally, a new method to further estimate the partial erasure threshold was proposed to approximate the partial erasure effects, and the relation between the microtrack jitter and total track jitter was investigated. 相似文献
75.
相关系数与相关性度量 总被引:2,自引:0,他引:2
研究了度量相关性的两个主要工具:线性相关系数和尾部相关系数.线性相关系数反映了变量间的线性相关性,这对于一般的椭圆型分布是合适的.但如果随机变量具有不对称的尾部变化特征时,要用尾部相关系数描述它们之间的相关性.通过相关函数C opu la,对沪深股市的尾部相关系数进行了定量分析.结果表明:沪深股市具有较强的相关性. 相似文献
76.
以山区高空间分辨率的DEM数据为主要数据源,在提取纬度、坡度、坡向等相应的地形要素栅格数据的基础上,利用GIS技术对山区可照时间的空间分布进行了模拟,实现了山区可照时间空间分布规律的可视化表达,分析了山区可照时间的空间分布特征,对于山区的农业、林业和生态环境等方面的研究具有重要意义. 相似文献
77.
In this paper we derive a priori and a posteriori error estimates for cell centered finite volume approximations of nonlinear conservation laws on polygonal bounded domains. Numerical experiments show the applicability of the a posteriori result for the derivation of local adaptive solution strategies.
78.
Analytical approach is presented to the isoperimetric type problems of finding convex figures separated by current hyperplanes. 相似文献
79.
Applied Biochemistry and Biotechnology - 相似文献
80.
S.K. Mahapatra B.K. Dandapat 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,102(2):277-292
The current study addresses the mathematical modeling aspects of coupled conductive and radiative heat transfer in the presence of absorbing, emitting and isotropic scattering gray medium within two-dimensional square enclosure. A blended method where the concepts of modified differential approximation employed by combining discrete ordinate method and spherical harmonics method, has been developed for modeling the radiative transport equation. The gray participating medium is bounded by isothermal walls of two-dimensional enclosure which are considered to be opaque, diffuse and gray. The effect of various influencing parameters i.e., radiation-conduction parameter, surface emissivity, single scattering albedo and optical thickness has been illustrated. The adaptability of the present method has also been addressed. 相似文献