全文获取类型
收费全文 | 20232篇 |
免费 | 1382篇 |
国内免费 | 2883篇 |
专业分类
化学 | 15729篇 |
晶体学 | 133篇 |
力学 | 698篇 |
综合类 | 177篇 |
数学 | 4815篇 |
物理学 | 2945篇 |
出版年
2024年 | 31篇 |
2023年 | 291篇 |
2022年 | 946篇 |
2021年 | 1083篇 |
2020年 | 1063篇 |
2019年 | 884篇 |
2018年 | 839篇 |
2017年 | 855篇 |
2016年 | 950篇 |
2015年 | 850篇 |
2014年 | 1056篇 |
2013年 | 2193篇 |
2012年 | 1349篇 |
2011年 | 1175篇 |
2010年 | 856篇 |
2009年 | 1250篇 |
2008年 | 1237篇 |
2007年 | 1073篇 |
2006年 | 880篇 |
2005年 | 804篇 |
2004年 | 651篇 |
2003年 | 504篇 |
2002年 | 658篇 |
2001年 | 296篇 |
2000年 | 346篇 |
1999年 | 341篇 |
1998年 | 285篇 |
1997年 | 248篇 |
1996年 | 229篇 |
1995年 | 186篇 |
1994年 | 162篇 |
1993年 | 129篇 |
1992年 | 108篇 |
1991年 | 87篇 |
1990年 | 53篇 |
1989年 | 83篇 |
1988年 | 56篇 |
1987年 | 32篇 |
1986年 | 33篇 |
1985年 | 57篇 |
1984年 | 67篇 |
1983年 | 30篇 |
1982年 | 42篇 |
1981年 | 31篇 |
1980年 | 25篇 |
1979年 | 24篇 |
1978年 | 17篇 |
1977年 | 10篇 |
1976年 | 13篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 771 毫秒
91.
Considering external electric field as well as third- and fourth-order phonon anharmonic interaction terms in the pseudospin-lattice
coupled mode (PLCM) model Hamiltonian for KDP-type ferroelectrics, expressions for field-dependent shift, width, renormalized
soft mode frequency, Curie temperature, dielectric constant and dielectric loss are evaluated. For the calculation, method
of statistical double-time temperature-dependent Green’s function has been used. By fitting model values of physical quantities,
temperature and electric field dependences of soft mode frequency, dielectric constant and loss have been calculated which
compare well with experimental results of Baumgartner [8] and Choi and Lockwood [9]. Both dielectric constant and loss decrease
with electric field. 相似文献
92.
Xi Nian FANG Jian Hua WANG 《数学学报(英文版)》2006,22(6):1819-1824
In this paper, we study the extension of isometries between the unit spheres of normed space E and C(Ω). We obtain that any surjective isometry between the unit spheres of normed space E and C(Ω) can be extended to be a linear isometry on the whole space E and give an affirmative answer to the corresponding Tingley's problem (where Ω be a compact metric space). 相似文献
93.
Summary The modifications induced by a magnetic field of arbitrary direction and intermediate strength (i.e not larger than 2.35·105 tesla, the ?atomic tesla?) on the lowest singlet and triplet energy states of the hydrogen molecule are studied. Using a
linear combination of products of field-modified atomic orbitals, it is found that increasing the field strength the depth
of the singlet energy well increases and the equilibrium internuclear distance decreases, yielding more rigid and localized
nuclear vibrations. For sufficiently strong fields perpendicular to the internuclear axis, the triplet state exhibits a bonding
behaviour. An explanation of the above results is given in terms of the field-modified electronic-charge distributions in
the internuclear region.
Based on the thesis submitted by S. Basile to the University of Palermo for graduation in Physics. 相似文献
94.
I. P. Rochev 《Mathematical Notes》2007,81(1-2):247-259
We consider generalizations of Pólya’s theorem to the case of entire functions taking algebraic values at natural or integer points. 相似文献
95.
Sándor Csörgő 《Acta Appl Math》2007,96(1-3):159-174
We consider the generalized convolution powers G
α
*u
(x) of an arbitrary semistable distribution function G
α
(x) of exponent α∈(0,2), and prove that for all j, k∈{0,1,2,…} and u>0 the derivatives G
α
(k,j)(x;u)=∂
k+j
G
α
*u
(x)/∂
x
k
∂
u
j
, x∈ℝ, are of bounded variation on the whole real line ℝ. The proof, along with an integral recursion in j, is new even in the special case of stable laws, and the result provides a framework for possible asymptotic expansions in
merge theorems from the domain of geometric partial attraction of semistable laws.
An erratum to this article can be found at 相似文献
96.
We study GaN/AlN Quantum Dot (QD) superlattices utilizing the STREL environment which allows the building of atomistic models, relaxation of the structures, the calculation of the electronic states and optical transitions and the visualization of the results. The forces are calculated using an appropriate Keating or Stillinger–Weber interatomic potential model and the electronic states and optical transitions using a tight-binding formulation which is economical and produces realistic electronic properties. The relaxed structure has strains mainly in the GaN region which are compressive and small tensile strains in the AlN region, mainly below the QD. In the calculation of the electronic states and of the optical transitions the strains are included realistically at the atomistic level. The study of the wavefunctions close to the fundamental gap show how these strains influence the form and spatial extent of the wavefunction. Very close to the fundamental gap the valence and some conduction states are confined in the QD and have considerable oscillator strength. 相似文献
97.
We show that the algorithm presented in an earlier paper by Studniarski (Numer. Math., 55:685–693, 1989) can be applied, after only a small modification, to approximate numerically Clarke’s subgradients of semismooth functions
of two variables. Results of computational testing of this modified algorithm are also reported.
相似文献
98.
在s波超导体绝缘层dx2-y2波超导体结(sId)中,考虑到结界面粗糙散射,运用BogoliubovdeGennes(BdG)方程和FurusakiTsukada(FT)电流公式,计算超导结中的准粒子传输系数和直流Josephson电流.结果表明:sId超导结的直流Josephson电流随温度以及结两侧的相位差变化的关系曲线强烈地依赖于d波超导体的晶轴方位;结界面的粗糙散射对Josephson电流有抑制作用
关键词:
s/I/d超导结
dx2-y2波超导体
直流Josephson电流 相似文献
99.
I. V. Ukrainets L. V. Sidorenko O. V. Gorokhova N. A. Jaradat 《Chemistry of Heterocyclic Compounds》2006,42(4):475-487
Various methods of synthesizing amides of 2-hydroxy-4-imino-1,4-dihydroquinoline-3-carboxylic acids have been studied. Results
of investigations on the antitubercular and antiinflammatory activity of the obtained compounds are discussed.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 542–555, April, 2006. 相似文献
100.
Two matrix approximation problems are considered: approximation of a rectangular complex matrix by subunitary matrices with
respect to unitarily invariant norms and a minimal rank approximation with respect to the spectral norm. A characterization
of a subunitary approximant of a square matrix with respect to the Schatten norms, given by Maher, is extended to the case
of rectangular matrices and arbitrary unitarily invariant norms. Iterative methods, based on the family of Gander methods
and on Higham’s scaled method for polar decomposition of a matrix, are proposed for computing subunitary and minimal rank
approximants. Properties of Gander methods are investigated in details.
AMS subject classification (2000) 65F30, 15A18 相似文献