全文获取类型
收费全文 | 17165篇 |
免费 | 461篇 |
国内免费 | 517篇 |
专业分类
化学 | 2697篇 |
晶体学 | 84篇 |
力学 | 113篇 |
综合类 | 118篇 |
数学 | 13863篇 |
物理学 | 1268篇 |
出版年
2023年 | 43篇 |
2022年 | 174篇 |
2021年 | 139篇 |
2020年 | 114篇 |
2019年 | 368篇 |
2018年 | 423篇 |
2017年 | 204篇 |
2016年 | 178篇 |
2015年 | 214篇 |
2014年 | 448篇 |
2013年 | 1081篇 |
2012年 | 593篇 |
2011年 | 995篇 |
2010年 | 926篇 |
2009年 | 1156篇 |
2008年 | 1175篇 |
2007年 | 1117篇 |
2006年 | 846篇 |
2005年 | 583篇 |
2004年 | 496篇 |
2003年 | 462篇 |
2002年 | 400篇 |
2001年 | 400篇 |
2000年 | 450篇 |
1999年 | 483篇 |
1998年 | 461篇 |
1997年 | 398篇 |
1996年 | 360篇 |
1995年 | 354篇 |
1994年 | 361篇 |
1993年 | 332篇 |
1992年 | 283篇 |
1991年 | 193篇 |
1990年 | 190篇 |
1989年 | 196篇 |
1988年 | 132篇 |
1987年 | 126篇 |
1986年 | 139篇 |
1985年 | 147篇 |
1984年 | 175篇 |
1983年 | 90篇 |
1982年 | 146篇 |
1981年 | 111篇 |
1980年 | 128篇 |
1979年 | 100篇 |
1978年 | 108篇 |
1977年 | 56篇 |
1976年 | 29篇 |
1975年 | 20篇 |
1973年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
We give a new and comparably short proof of Gittins’ index theorem for dynamic allocation problems of the multi-armed bandit type in continuous time under minimal assumptions. This proof gives a complete characterization of optimal allocation strategies as those policies which follow the current leader among the Gittins indices while ensuring that a Gittins index is at an all-time low whenever the associated project is not worked on exclusively. The main tool is a representation property of Gittins index processes which allows us to show that these processes can be chosen to be pathwise lower semi-continuous from the right and quasi-lower semi-continuous from the left. Both regularity properties turn out to be crucial for our characterization and the construction of optimal allocation policies. 相似文献
62.
Christos Kravvaritis Marilena Mitrouli Jennifer Seberry 《Linear and Multilinear Algebra》2007,55(5):471-490
In the present article we concentrate our study on the growth problem for the weighing matrix W(12,11) and show that the unique W(12,11) has three pivot structures. An improved algorithm for extending a k × k (0,+,-) matrix to a W(n,n-1), if possible, has been developed to simplify the proof. For the implementation of the algorithm special emphasis is given to the notions of data structures and parallel processing. 相似文献
63.
Summary The paper addresses the problem of the implementation of nonhomogeneous essential Dirichlet type boundary conditions in thep-version of the finite element method.Partially supported by the Office of Naval Research under Grant N-00014-85-K-0169Research partially supported by the Air Force Office of Scientific Research, Air Force Systems Command, USAF, under Grant Number AFOSR 85-0322 相似文献
64.
We study the multiplicity of critical points for functionals which are only differentiable along some directions. We extend to this class of functionals the three critical point theorem of Pucci and Serrin and we apply it to a one-parameter family of functionals Jλ, λ∈I⊂R. Under suitable assumptions, we locate an open subinterval of values λ in I for which Jλ possesses at least three critical points. Applications to quasilinear boundary value problems are also given. 相似文献
65.
Danny E. Akin W. Herbert Morrison III Luanne L. Rigsby Franklin E. Barton II David S. Himmelsbach Kevin B. Hicks 《Applied biochemistry and biotechnology》2006,129(1-3):104-116
Information is presented on structure, composition, and response to enzymes of corn stover related to barriers for bioconversion
to ethanol. Aromatic compounds occurred in most tissue cell walls. Ferulic acid esterase treatment before cellulase treatment
significantly improved dry weight loss and release of phenolic acids and sugars in most fractions over cellulase alone. Leaf
fractions were considerably higher in dry weight loss and released sugars with esterase treatment, but stem pith cells gave
up the most phenolic acids. Results help identify plant fractions more appropriate for coproducts and bioconversion and those
more suitable as residues for soil erosion control. 相似文献
66.
We consider Sinai’s random walk in random environment. We prove that infinitely often (i.o.) the size of the concentration neighborhood of this random walk is bounded almost surely. We also get that i.o. the maximal distance between two favorite sites is bounded almost surely. 相似文献
67.
Jurie Conradie 《Positivity》2006,10(3):591-606
The possibility of characterizing the Mackey topology of a dual pair of vector spaces as a generalized inductive limit (or
mixed) topology is investigated. Positive answers are given for a wide range of dual pairs of Riesz spaces (vector lattices)
and non-commutative Banach function spaces (or symmetric operator spaces). 相似文献
68.
The large deviation theorems, exponential inequalities and a non-uniform estimate of the Berry–Esséen theorem in a discounted version are proved.Dedicated to Professor Vytautas Statulevičius on the occasion of his 75th birthday. 相似文献
69.
The oxide films formed on AISI 304L stainless steel at 300 °C in the oxidation time range between 2 and 4 h have been studied by photoelectrochemistry. Photocurrents were investigated as a function of the wavelength of the incident light and the electrode potential. The investigation allowed the determination of the semiconductive properties of the oxides. The oxide films showed n-type behaviour. A duplex structure of the oxide films has been suggested on the basis of the photocurrent spectra, with an internal oxide layer having an optical gap (Eg2 = 2.16-2.3 eV) depending on the applied potential and oxidation time, higher to that of the external oxide layer (Eg1 ≈ 1.9 eV). Significant variations in the amplitude of the photocurrent were detected as a function of the applied potential and the oxidation time. 相似文献
70.
Single Qubit and Its Universal Logic Gate Made of a Heisenberg Spin Cluster with Five Particles
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We investigate an anisotropic Heisenberg spin cluster with five particles controlled by a time-dependent magnetic field. With the algebraic dynamical method, we obtain the exact analytical solution to the time dependent Schr6dinger equation. Based on the analytical solution, it is shown that the system can be used as a universal single qubit logic gate controlled by the strength and frequency of the magnetic field, and the six special single qubit logic gates can be realized physically. We also discuss the anti-decoherence property of the qubit and its logic gates resulted from particle coupling effect and collectivity of the cluster. 相似文献