全文获取类型
收费全文 | 38886篇 |
免费 | 3119篇 |
国内免费 | 1463篇 |
专业分类
化学 | 26662篇 |
晶体学 | 424篇 |
力学 | 1512篇 |
综合类 | 67篇 |
数学 | 4130篇 |
物理学 | 10673篇 |
出版年
2023年 | 435篇 |
2022年 | 795篇 |
2021年 | 1091篇 |
2020年 | 1102篇 |
2019年 | 1020篇 |
2018年 | 895篇 |
2017年 | 791篇 |
2016年 | 1396篇 |
2015年 | 1310篇 |
2014年 | 1587篇 |
2013年 | 2554篇 |
2012年 | 2992篇 |
2011年 | 3230篇 |
2010年 | 2053篇 |
2009年 | 1932篇 |
2008年 | 2610篇 |
2007年 | 2309篇 |
2006年 | 2220篇 |
2005年 | 1962篇 |
2004年 | 1678篇 |
2003年 | 1361篇 |
2002年 | 1304篇 |
2001年 | 872篇 |
2000年 | 793篇 |
1999年 | 635篇 |
1998年 | 409篇 |
1997年 | 359篇 |
1996年 | 478篇 |
1995年 | 361篇 |
1994年 | 344篇 |
1993年 | 336篇 |
1992年 | 277篇 |
1991年 | 224篇 |
1990年 | 215篇 |
1989年 | 173篇 |
1988年 | 134篇 |
1987年 | 126篇 |
1986年 | 98篇 |
1985年 | 127篇 |
1984年 | 93篇 |
1983年 | 61篇 |
1982年 | 84篇 |
1981年 | 87篇 |
1980年 | 49篇 |
1979年 | 60篇 |
1978年 | 54篇 |
1977年 | 48篇 |
1976年 | 52篇 |
1975年 | 50篇 |
1974年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
41.
42.
43.
Jong Uhn Kim 《Transactions of the American Mathematical Society》2002,354(3):1117-1135
In this paper we discuss an initial-boundary value problem for a stochastic nonlinear equation arising in one-dimensional viscoelasticity. We propose to use a new direct method to obtain a solution. This method is expected to be applicable to a broad class of nonlinear stochastic partial differential equations.
44.
This paper reports that the growth of RuOx(110) thin layer growth on Ru(0001)
has been investigated by means of scanning tunnelling microscope (STM). The STM
images showed a domain structure with three rotational domains of RuOx(110)
rotated by an angle of 120℃.
The as-grown RuOx(110) thin layer is expanded from the bulk-truncated
RuOx(110) due to the large mismatch between RuOx(110) and the
Ru(0001) substrate. The results also indicate that growth of RuOx(110)
thin layer on the Ru(0001) substrate by oxidation tends first to formation
of the Ru-O (oxygen) chains in the [001] direction of RuOx(110). 相似文献
45.
Gauss periods give an exponentiation algorithm that is fast for many finite fields but slow for many other fields. The current paper presents a different method for construction of elements that yield a fast exponentiation algorithm for finite fields where the Gauss period method is slow or does not work. The basic idea is to use elements of low multiplicative order and search for primitive elements that are binomial or trinomial of these elements. Computational experiments indicate that such primitive elements exist, and it is shown that they can be exponentiated fast. 相似文献
46.
Neodymium-substituted Bi4Ti3O12 (BNdT) thin films were prepared by a chemical solution deposition technique on platinum- coated silicon substrates. All of
the samples were annealed at the relatively low temperature of 600 °C by a rapid thermal annealing process in different atmospheres,
such as O2, air, and nitrogen, and vacuum. Irrespective of different annealing atmospheres, all of the BNdT thin films exhibit good
ferroelectric properties, such as a saturated hysteresis loop, good fatigue endurance, and low leakage current density. A
large remanent polarization (Pr) of ∼48 μC/cm2 with an electric field of 240 kV/cm was observed from the BNdT thin film annealed in O2 atmosphere. The BNdT thin films annealed in nitrogen and vacuum, at reduced oxygen partial pressures, exhibit smaller Pr than that annealed in oxygen. The difference of Pr of the BNdT thin films annealed in different atmospheres may originate from differences in the grain sizes and the number
of oxygen vacancies.
PACS 77.55.+f; 77.80.-e; 77.80.Fm; 81.15.-z 相似文献
47.
就一般非完整约束系统,从约束方程满足的变分恒等式出发,利用增广位形流形上的向量场定义三类非自由变分,即非完整变分:vakonomic变分、Hlder变分、Suslov变分,并讨论它们之间的关系以及它们成为自由变分的充要条件.利用非完整变分以及相应的积分变分原理建立两类动力学方程:vakonomic方程和Routh方程或Chaplygin方程.通过vakonomic方程分别与Routh方程和Chaplygin方程比较,得到它们具有共同解的两类充分必要条件.这些条件并不是约束的可积性条件.
关键词:
非完整约束
非完整变分
Chetaev条件
vakonomic动力学 相似文献
48.
49.
K. C. Shin 《Communications in Mathematical Physics》2002,229(3):543-564
We study the eigenvalue problem with the boundary conditions that decays to zero as z tends to infinity along the rays , where is a real polynomial and . We prove that if for some we have for all , then the eigenvalues are all positive real. We then sharpen this to a larger class of polynomial potentials.
In particular, this implies that the eigenvalues are all positive real for the potentials when with , and with the boundary conditions that decays to zero as z tends to infinity along the positive and negative real axes. This verifies a conjecture of Bessis and Zinn-Justin.
Received: 16 January 2002 / Accepted: 1 May 2002 Published online: 6 August 2002 相似文献
50.
Taekyun Kim 《Journal of Mathematical Analysis and Applications》2002,273(1):236-242
The purpose of this paper is to give a proof of Kummer type congruence for the q-Bernoulli numbers of higher order, which is an answer to a part of the problem in a previous publication (see Indian J. Pure Appl. Math. 32 (2001) 1565-1570). 相似文献