全文获取类型
收费全文 | 82112篇 |
免费 | 431篇 |
国内免费 | 396篇 |
专业分类
化学 | 26914篇 |
晶体学 | 807篇 |
力学 | 6838篇 |
数学 | 32499篇 |
物理学 | 15881篇 |
出版年
2022年 | 100篇 |
2021年 | 120篇 |
2020年 | 70篇 |
2019年 | 91篇 |
2018年 | 10459篇 |
2017年 | 10292篇 |
2016年 | 6218篇 |
2015年 | 936篇 |
2014年 | 432篇 |
2013年 | 548篇 |
2012年 | 4035篇 |
2011年 | 10759篇 |
2010年 | 5802篇 |
2009年 | 6204篇 |
2008年 | 6829篇 |
2007年 | 8999篇 |
2006年 | 442篇 |
2005年 | 1542篇 |
2004年 | 1724篇 |
2003年 | 2132篇 |
2002年 | 1150篇 |
2001年 | 292篇 |
2000年 | 344篇 |
1999年 | 202篇 |
1998年 | 230篇 |
1997年 | 186篇 |
1996年 | 260篇 |
1995年 | 171篇 |
1994年 | 128篇 |
1993年 | 132篇 |
1992年 | 78篇 |
1991年 | 95篇 |
1990年 | 80篇 |
1989年 | 97篇 |
1988年 | 84篇 |
1987年 | 81篇 |
1986年 | 75篇 |
1985年 | 75篇 |
1984年 | 81篇 |
1983年 | 54篇 |
1982年 | 65篇 |
1981年 | 69篇 |
1980年 | 69篇 |
1979年 | 65篇 |
1978年 | 54篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Onofrio Mario Di Vincenzo Plamen Koshlukov Roberto La Scala 《Advances in Applied Mathematics》2006,37(4):541
In this paper we describe completely the involutions of the first kind of the algebra UTn(F) of n×n upper triangular matrices. Every such involution can be extended uniquely to an involution on the full matrix algebra. We describe the equivalence classes of involutions on the upper triangular matrices. There are two distinct classes for UTn(F) when n is even and a single class in the odd case.Furthermore we consider the algebra UT2(F) of the 2×2 upper triangular matrices over an infinite field F of characteristic different from 2. For every involution *, we describe the *-polynomial identities for this algebra. We exhibit bases of the corresponding ideals of identities with involution, and compute the Hilbert (or Poincaré) series and the codimension sequences of the respective relatively free algebras.Then we consider the *-polynomial identities for the algebra UT3(F) over a field of characteristic zero. We describe a finite generating set of the ideal of *-identities for this algebra. These generators are quite a few, and their degrees are relatively large. It seems to us that the problem of describing the *-identities for the algebra UTn(F) of the n×n upper triangular matrices may be much more complicated than in the case of ordinary polynomial identities. 相似文献
103.
Ying Zhang Gang Hu Shigang Chen H.A. Cerdeira 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):381-384
A method of controlling global stochasticity in Hamiltonian systems by applying nonlinear perturbation is proposed. With the
well-known standard map we demonstrate that this control method can convert global stochasticity into regular motion in a
wide chaotic region for arbitrary initial condition, in which the control signal remains very weak after a few kicks. The
system in which chaos has been controlled approximates to the original Hamiltonian system, and this approach appears robust
against small external noise. The mechanism underlying this high control efficiency is intuitively explained.
Received 15 January 2002 Published online 6 June 2002 相似文献
104.
105.
Joseph Shipman 《Mathematical Intelligencer》2007,29(4):9-14
Theorems 2 and 3 establish the minimum algebraic conditions necessary for a field to be algebraically closed, and they can
therefore be said to “optimize” the Fundamental Theorem of Algebra. But each specific“degree implication” is a first-order
consequence of the axioms for fields, and could have been discovered two centuries ago; the existence of these finitary relationships
appears to have been unsuspected by practically everyone, with one important exception. 相似文献
106.
Ling-yan Tang Song-he Song 《应用数学学报(英文版)》2007,23(2):303-310
In this paper,we use Daubechies scaling functions as test functions for the Galerkin method,and discuss Wavelet-Galerkin solutions for the Hamilton-Jacobi equations.It can be proved that the schemesare TVD schemes.Numerical tests indicate that the schemes are suitable for the Hamilton-Jacobi equations.Furthermore,they have high-order accuracy in smooth regions and good resolution of singularities. 相似文献
107.
Luca Lambertini Raimondello Orsini 《Central European Journal of Operations Research》2007,15(1):105-117
We reconsider the role of network externalities in a dynamic spatial monopoly where the firm must invest in order to accumulate
capacity, while consumers may have either linear or quadratic preferences. We (1) characterise saddle point equilibria, (2)
prove that the extent of market coverage is increasing in the network effect and (3) unlike the existing static literature
on the same problem, the monopolist may not make introductory price offers. Then, we briefly deal with the socially optimal
solution, showing that, in general, a planner would serve more consumers than a profit-seeking monopolist.
相似文献
108.
This paper reports positive results from an application of one type of group support system (GSS) to a training application. Reviews of the findings of other trials of GSS have been mixed, and inconclusive. We describe the results of a series of seven training sessions in a field-based application of group process support. The subjects were professionals working in various agencies concerned with the welfare of older people. A ‘low-profile’ type of group support system, based on wireless handsets, was used. This design enabled responses from each participant to be input and displayed anonymously. Each session was aimed at stimulating a dialogue focused on the reasons for differences of judgement, as displayed on a single projected feedback screen. Changes of individual judgements were recorded for subsequent analysis and comparison with already known ‘expert judgements’. Frequent changes of judgement were recorded. A significant proportion of these were related to an improvement, which could not be explained as simply the result of conforming behaviour. We propose that the mode of operation and design of a ‘low-profile’ GSS have the potential to create a learning environment by reducing personal anxieties while encouraging group-based learning with focussed conversation. We conclude that this type of GSS design is particularly suited to ‘selective’-type tasks in groups. 相似文献
109.
Hans Weber 《Order》2007,24(4):249-276
We study lattice theoretical properties of lattices of uniformities such as modularity, distributive laws and the existence
of (relative) complements. For this the concepts of permutable uniformities (see Definition 3.1) and independent uniformities
(see Definition 4.1) are important. Moreover, we show that e.g. the lattice of all lattice uniformities on a lattice L is a closed sublattice of the lattice of all uniformities on L. 相似文献
110.
Bernardo Lafuerza-Guillén Donal O’regan Reza Saadati 《Proceedings Mathematical Sciences》2007,117(1):61-70
We introduce the concept of quotient in PN spaces and give some examples. We prove some theorems with regard to the completeness
of a quotient. 相似文献