全文获取类型
收费全文 | 56171篇 |
免费 | 4063篇 |
国内免费 | 3866篇 |
专业分类
化学 | 23581篇 |
晶体学 | 169篇 |
力学 | 2412篇 |
综合类 | 1117篇 |
数学 | 22331篇 |
物理学 | 14490篇 |
出版年
2023年 | 461篇 |
2022年 | 1925篇 |
2021年 | 1745篇 |
2020年 | 1070篇 |
2019年 | 1194篇 |
2018年 | 995篇 |
2017年 | 1127篇 |
2016年 | 1373篇 |
2015年 | 1318篇 |
2014年 | 2055篇 |
2013年 | 3331篇 |
2012年 | 2309篇 |
2011年 | 2726篇 |
2010年 | 2495篇 |
2009年 | 3221篇 |
2008年 | 3353篇 |
2007年 | 3533篇 |
2006年 | 2840篇 |
2005年 | 2218篇 |
2004年 | 1886篇 |
2003年 | 1881篇 |
2002年 | 4250篇 |
2001年 | 1917篇 |
2000年 | 1420篇 |
1999年 | 1205篇 |
1998年 | 1152篇 |
1997年 | 947篇 |
1996年 | 866篇 |
1995年 | 730篇 |
1994年 | 692篇 |
1993年 | 675篇 |
1992年 | 646篇 |
1991年 | 442篇 |
1990年 | 425篇 |
1989年 | 339篇 |
1988年 | 348篇 |
1987年 | 269篇 |
1986年 | 274篇 |
1985年 | 397篇 |
1984年 | 300篇 |
1983年 | 203篇 |
1982年 | 363篇 |
1981年 | 526篇 |
1980年 | 469篇 |
1979年 | 513篇 |
1978年 | 415篇 |
1977年 | 310篇 |
1976年 | 268篇 |
1974年 | 118篇 |
1973年 | 210篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
Lisa Lorentzen 《Numerical Algorithms》1995,10(1):69-111
Over the last 20 years a large number of algorithms has been published to improve the speed and domain of convergence of continued fractions. In this survey we show that these algorithms are strongly related. Actually, they essentially boil down to two main principles.We also prove some results on asymptotic expansions of tail values of limit periodic continued fractions.Dedicated to Luigi Gatteschi on his seventieth birthdayThis research was partially supported by The Norwegian Research Council and by the HMC project ROLLS, under contract CHRX-CT93-0416. 相似文献
4.
本文利用统计计量学方法对山西省农民家庭消费水平和消费结构的变化及原因进行了实证分析。建立了山西省农民人均消费的消费函数和山西省农民总消费支出与食品、衣着、住房、日用品、燃料及文化生活服务支出的关系模型,并通过模型分析解释了农民的消费结构,也为决策者提供一些有效的参考资料。 相似文献
5.
We employ a first-principles plane wave method with the
relativistic analytic pseudopotential of Hartwigsen, Goedecker and Hutter
(HGH) scheme in the frame of DFT to calculate
the equilibrium lattice parameters and the thermodynamic properties of
AlB2 compound with hcp structure. The obtained lattice parameters are in
good agreement with the available experimental data and those calculated by
others. Through the quasi-harmonic Debye model, obtained successfully are
the dependences of the
normalized lattice parameters a/a0 and c/c0 on pressure P, the normalized
primitive cell volume V/V0 on pressure P, the variation of the thermal
expansion α with pressure P and temperature T, as well as the Debye
temperature \ThetaD and the heat capacity CV on pressure P and
temperature T. 相似文献
6.
A.-S. F. Obada M. Darwish H. H. Salah 《International Journal of Theoretical Physics》2002,41(9):1755-1768
In this paper a new state called odd-excited binomial state (OEBS) is introduced. It interpolates between the odd number state and the odd-excited coherent state. We discuss some statistical properties, such as the Glauber second-order correlation function and squeezing phenomenon (normal and amplitude-squared squeezing) for this state. The quasiprobability distribution functions (Husimi Q-function and Wigner W-function) are also examined. 相似文献
7.
Shougo Higashi 《Surface science》2006,600(3):591-597
We have studied the individual adsorption of Mn and Bi, and their coadsorption on Cu(0 0 1) by low-energy electron diffraction (LEED). For Mn, we have determined the c(2 × 2) structure formed at 300 K, whose structure had been determined by several methods. We reconfirmed by a tensor LEED analysis that it is a substitutional structure and that a previously reported large corrugation (0.30 Å) between substitutional Mn and remaining surface Cu atoms coincides perfectly with the present value. In the individual adsorption of Bi, we have found a c(4 × 2) structure, which is formed by cooling below ∼250 K a surface prepared by Bi deposition of ∼0.25 ML coverage at 300 K where streaky half-order LEED spots appear. The c(4 × 2) structure has been determined by the tensor LEED analysis at 130 K and it is a substitutional structure. In the coadsorption, we found a c(6 × 4) structure, which has been determined by the tensor LEED analysis. It is very similar to the previously determined structure of the c(6 × 4) formed by coadsorption of Mg and Bi, and embedded MnBi4 clusters are arranged in the top Cu layer instead of MgBi4. Large lateral displacements of Bi atoms in the c(6 × 4)-(Mn + Bi) suggest that the Mn atoms undergo the size-enhancement caused by their large magnetic moment. 相似文献
8.
Necessary conditions for the Gâteaux differentiability of the distance function to a set are considered. A series of characterizing results is obtained. 相似文献
9.
Eva Lesanska 《Applications of Mathematics》2002,47(5):411-426
The problem is to determine nonsensitiveness regions for threshold ellipsoids within a regular mixed linear model. 相似文献
10.
Camillo Costantini 《Topology and its Applications》2006,153(7):1056-1078
For X a metrizable space and (Y,ρ) a metric space, with Y pathwise connected, we compute the density of (C(X,(Y,ρ)),σ)—the space of all continuous functions from X to (Y,ρ), endowed with the supremum metric σ. Also, for (X,d) a metric space and (Y,‖⋅‖) a normed space, we compute the density of (UC((X,d),(Y,ρ)),σ) (the space of all uniformly continuous functions from (X,d) to (Y,ρ), where ρ is the metric induced on Y by ‖⋅‖). We also prove that the latter result extends only partially to the case where (Y,ρ) is an arbitrary pathwise connected metric space.To carry such an investigation out, the notions of generalized compact and generalized totally bounded metric space, introduced by the author and A. Barbati in a former paper, turn out to play a crucial rôle. Moreover, we show that the first-mentioned concept provides a precise characterization of those metrizable spaces which attain their extent. 相似文献