全文获取类型
收费全文 | 5143篇 |
免费 | 66篇 |
国内免费 | 11篇 |
专业分类
化学 | 3680篇 |
晶体学 | 13篇 |
力学 | 63篇 |
数学 | 691篇 |
物理学 | 773篇 |
出版年
2016年 | 55篇 |
2015年 | 61篇 |
2014年 | 63篇 |
2013年 | 128篇 |
2012年 | 120篇 |
2011年 | 149篇 |
2010年 | 109篇 |
2009年 | 99篇 |
2008年 | 140篇 |
2007年 | 183篇 |
2006年 | 136篇 |
2005年 | 145篇 |
2004年 | 160篇 |
2003年 | 121篇 |
2002年 | 139篇 |
2001年 | 85篇 |
2000年 | 116篇 |
1999年 | 90篇 |
1998年 | 68篇 |
1997年 | 77篇 |
1996年 | 72篇 |
1995年 | 71篇 |
1994年 | 67篇 |
1993年 | 78篇 |
1992年 | 78篇 |
1991年 | 54篇 |
1990年 | 42篇 |
1989年 | 45篇 |
1988年 | 53篇 |
1987年 | 56篇 |
1986年 | 71篇 |
1985年 | 84篇 |
1984年 | 52篇 |
1982年 | 55篇 |
1981年 | 75篇 |
1980年 | 57篇 |
1979年 | 66篇 |
1978年 | 60篇 |
1977年 | 55篇 |
1976年 | 51篇 |
1975年 | 45篇 |
1974年 | 55篇 |
1972年 | 42篇 |
1965年 | 49篇 |
1964年 | 100篇 |
1963年 | 136篇 |
1962年 | 169篇 |
1961年 | 154篇 |
1960年 | 150篇 |
1958年 | 51篇 |
排序方式: 共有5220条查询结果,搜索用时 93 毫秒
1.
2.
3.
We study conditions on the matrix mask of a vector subdivision scheme ensuring that certain polynomial input vectors yield polynomial output again. The conditions are in terms of a recurrence formula for the vectors which determine the structure of polynomial input with this property. From this recurrence, we obtain an algorithm to determine polynomial input of maximal degree. The algorithm can be used in the design of masks to achieve a high order of polynomial reproduction. 相似文献
4.
Julien Ferrari Christian Terreaux Tibor Kurtn Attila Szikszai‐Kiss Sndor Antus JeromeD. Msonthi Kurt Hostettmann 《Helvetica chimica acta》2003,86(8):2768-2778
Investigation of the methanol extract of the roots of Gnidia involucrata (Thymelaeaceae) led to the isolation and characterization of two new 3,8″‐biflavonoid diastereoisomers, named GB‐4 ( 6a ) and GB‐4a ( 6b ). Their absolute configurations were determined in mixture by on‐line LC/CD measurements, which also allowed the revision of absolute configurations of the biflavanoids GB‐1 and GB‐2, and the configurational assignment of GB‐3. 相似文献
5.
Kurt Majewski 《Queueing Systems》2005,50(2-3):199-230
We consider multiclass feedforward queueing networks under first in first out and priority service disciplines driven by long-range dependent arrival and service time processes. We show that in critical loading the normalized workload, queue length and sojourn time processes can converge to a multi-dimensional reflected fractional Brownian motion. This weak heavy traffic approximation is deduced from a deterministic pathwise approximation of the network behavior close to constant critical load in terms of the solution of a Skorokhod problem. Since we model the doubly infinite time interval, our results directly cover the stationary case.AMS subject classification: primary 90B15, secondary 60K25, 68M20 相似文献
6.
Mathematical Methods of Operations Research - 相似文献
7.
T. N. Mamedov V. N. Duginov A. V. Stoykov I. L. Chaplygin D. Herlach U. Zimmermann V. N. Gorelkin J. Major M. Schefzik 《JETP Letters》1998,68(1):64-70
The residual polarization of negative muons in crystal silicon samples with phosphorus (P: 1.6×1013 cm−3) and antimony (Sb: 2×1018 cm−3) impurities is investigated. The measurements are made in a 1000 G magnetic field oriented in a direction transverse to the
muon spin in the temperature range 4–300 K. The relaxation rate and shift of the precession frequency in the silicon sample
with the phosphorus impurity are measured more accurately than previously. It is found that in antimony-doped silicon the
acceptor center
μ
A1 at temperatures below 30 K can be in both ionized and neutral states. The experimental data are interpreted on the basis
of spin-lattice relaxation of the magnetic moment of an acceptor center, formation of acceptor-donor pairs, and recombination
of charge carriers at the acceptor. Preliminary measurements showed a nonzero residual polarization of negative muons in germanium.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 1, 61–66 (10 July 1998) 相似文献
8.
Kurt M. Anstreicher 《Mathematical Programming》1997,76(1):245-263
We consider the construction of small step path following algorithms using volumetric, and mixed volumetric-logarithmic, barriers.
We establish quadratic convergence of a volumetric centering measure using pure Newton steps, enabling us to use relatively
standard proof techniques for several subsequently needed results. Using a mixed volumetric-logarithmic barrier we obtain
an O(n
1/4
m
1/4
L) iteration algorithm for linear programs withn variables andm inequality constraints, providing an alternative derivation for results first obtained by Vaidya and Atkinson. In addition,
we show that the same iteration complexity can be attained while holding the work per iteration to O(n
2
m), as opposed to O(nm
2), operations, by avoiding use of the true Hessian of the volumetric barrier. Our analysis also provides a simplified proof
of self-concordancy of the volumetric and mixed volumetric-logarithmic barriers, originally due to Nesterov and Nemirovskii.
This paper was first presented at the 1994 Faculty Research Seminar “Optimization in Theory and Practice”, at the University
of Iowa Center for Advanced Studies. 相似文献
9.
Alexander Zimmermann 《Algebras and Representation Theory》2004,7(1):19-34
In an earlier paper, Raphaël Rouquier and the author introduced the group of self-equivalences of a derived category. In the case of a Brauer tree algebra, we determined a nontrivial homomorphism of the Artin braid group to this group of self-equivalences. The class of Brauer tree algebras include blocks of finite group rings over a large enough field with cyclic defect groups. In the present paper we give an integral version of this homomorphism. Moreover, we identify some interesting arithmetic subgroups with natural groups of self-equivalences of the derived category. 相似文献
10.
The synthesis of a specific isotopomer, C6D4H(ortho)-H(ortho)D4C6 of biphenyl is reported. The intramolecular dipolar coupling of the protons leads to a well-resolved single-crystal proton
nuclear magnetic resonance (NMR) spectrum and allows one to study the dynamics of the phenyl rings in a unique way. At room
temperature and above, the most conspicuous dynamical mode consists of 180° ring flips. The present data together with previous
measurements of the total flip rate allow us to conclude that the rings flip almost exclusively independently of each other.
Between the incommensurate (IC) phase transition of biphenyl at 38 K andT=250 K, the prominent namical mode consists of oscillatory twists ϕ(t) of the two rings. The data allow us to infer the mean square, (φ2), of these twists. (φ2) is found to grow linearly withT for 50<T<200 K. From the slope of (φ2) vs.T the frequency (the wave number[(v)\tilde]\tilde v) is derived. The result is[(v)\tilde] = 20\tilde v = 20 cm−1. ForT<38 K, the spectra give direct evidence of the IC phase transition and its nature (stripelike rather than quiltlike). The
temperature dependence of the magnitude of the order parameter of the IC phase is obtained. 相似文献