全文获取类型
收费全文 | 7899篇 |
免费 | 260篇 |
国内免费 | 61篇 |
专业分类
化学 | 5236篇 |
晶体学 | 41篇 |
力学 | 277篇 |
数学 | 1593篇 |
物理学 | 1073篇 |
出版年
2023年 | 47篇 |
2022年 | 69篇 |
2021年 | 187篇 |
2020年 | 155篇 |
2019年 | 162篇 |
2018年 | 139篇 |
2017年 | 114篇 |
2016年 | 276篇 |
2015年 | 234篇 |
2014年 | 240篇 |
2013年 | 443篇 |
2012年 | 530篇 |
2011年 | 594篇 |
2010年 | 361篇 |
2009年 | 352篇 |
2008年 | 517篇 |
2007年 | 485篇 |
2006年 | 486篇 |
2005年 | 411篇 |
2004年 | 352篇 |
2003年 | 279篇 |
2002年 | 292篇 |
2001年 | 99篇 |
2000年 | 73篇 |
1999年 | 67篇 |
1998年 | 79篇 |
1997年 | 87篇 |
1996年 | 98篇 |
1995年 | 58篇 |
1994年 | 79篇 |
1993年 | 55篇 |
1992年 | 56篇 |
1991年 | 43篇 |
1990年 | 53篇 |
1989年 | 48篇 |
1988年 | 39篇 |
1987年 | 40篇 |
1986年 | 29篇 |
1985年 | 44篇 |
1984年 | 61篇 |
1983年 | 39篇 |
1982年 | 45篇 |
1981年 | 31篇 |
1980年 | 40篇 |
1979年 | 29篇 |
1978年 | 30篇 |
1977年 | 27篇 |
1976年 | 14篇 |
1974年 | 15篇 |
1973年 | 14篇 |
排序方式: 共有8220条查询结果,搜索用时 568 毫秒
941.
Summary Analytic equations of the multiconfigurational SCF (MCSCF) response theory are combined with the finite-field (FF) approach to compute static and frequency dependent electric and magnetic properties of the Argon atom. A complete active space (CAS SCF) function including the 3s, 3p, 3d, 4s and 4p orbitals in the active space and a large (17s 13p 7d 5f 3g) basis set are employed. This permits an accurate determination of various linear and non-linear response properties such as e.g. electric dipole polarisability and second hyperpolarisability, Verdet constant, magnetisability and second hyperpolarisability. The results, both for the static values and for the frequency dependence of these properties, compare well with other most recent experimental and theoretical data.Dedicated to Jan Linderberg on the occasion of his 60th birthday 相似文献
942.
943.
On Metastability in FPU 总被引:1,自引:0,他引:1
We present an analytical study of the Fermi–Pasta–Ulam (FPU) α–model with periodic boundary conditions. We analyze the dynamics corresponding to initial data with one low frequency Fourier
mode excited. We show that, correspondingly, a pair of KdV equations constitute the resonant normal form of the system. We
also use such a normal form in order to prove the existence of a metastability phenomenon. More precisely, we show that the
time average of the modal energy spectrum rapidly attains a well defined distribution corresponding to a packet of low frequencies
modes. Subsequently, the distribution remains unchanged up to the time scales of validity of our approximation. The phenomenon
is controlled by the specific energy. 相似文献
944.
945.
We study the analytic singularities of viscosity solutions of equations of eikonal type and obtain that the analytic singular
support of these functions has an analytic stratification. The singular support can be identified with the cut locus of the
distance to the boundary of an open set, when the interior is equipped with a degenerate Riemannian metric. We apply the result
to elliptic equations as well as to model operators of Grušin type. 相似文献
946.
947.
J. Lub D. J. Broer M. E. Martinez Antonio G. N. Mol 《Liquid crystals》1998,24(3):375-379
A nematic liquid crystal material containing a mercapto group and an olefinic group was synthesized. Photopolymerization of this compound in the liquid crystalline state resulted in a liquid crystalline main chain polymer which showed a relatively high birefringence. Due to scattering, the material had a low transmission at ambient temperatures. 相似文献
948.
949.
Simona Bronco Giambattista Consiglio Silvia Di Benedetto Matthias Fehr Felix Spindler Antonio Togni 《Helvetica chimica acta》1995,78(4):883-886
Cationic Pd-complexes modified by dicyclohexyl{(R)-1-[(S)-2-(diphenylphosphino)ferrocenyl]ethyl}phosphine ( 1a ) give very active catalytic systems for the regioregular isotactic specific copolymerization of propene with CO. Other alk-1-enes also give stereoregular and regioregular copolymers, even if with lower productivity. The copolymers are isolated as poly(4-alkyl-tetrahydrofuran-2,2,5,5-tetrayl-2-oxy-2-methylenes) B in the solid state and give the isomeric poly(2-alkyl-1-oxopropane-1,3-diyls) A by dissolution in (CF3)2CHOH. Solid polymer A (R = Et) is formed back at least partially when the dissolved material is reprecipitated from MeOH. The use of the related (ferrocenyl)diphosphine ligands 1b ? e and 2 as the catalyst modifier shows that the presence of both elements of chirality and of large substituents on the P-atoms of the ligand is necessary to achieve good stereocontrol, and that the large difference in basicity between the two P-atoms is probably the reason for the good catalytic activity. 相似文献
950.