全文获取类型
收费全文 | 9890篇 |
免费 | 212篇 |
国内免费 | 257篇 |
专业分类
化学 | 1500篇 |
晶体学 | 76篇 |
力学 | 74篇 |
综合类 | 32篇 |
数学 | 7696篇 |
物理学 | 981篇 |
出版年
2023年 | 33篇 |
2022年 | 94篇 |
2021年 | 58篇 |
2020年 | 70篇 |
2019年 | 235篇 |
2018年 | 242篇 |
2017年 | 151篇 |
2016年 | 124篇 |
2015年 | 134篇 |
2014年 | 275篇 |
2013年 | 600篇 |
2012年 | 314篇 |
2011年 | 690篇 |
2010年 | 482篇 |
2009年 | 609篇 |
2008年 | 704篇 |
2007年 | 721篇 |
2006年 | 589篇 |
2005年 | 439篇 |
2004年 | 361篇 |
2003年 | 324篇 |
2002年 | 249篇 |
2001年 | 217篇 |
2000年 | 209篇 |
1999年 | 216篇 |
1998年 | 215篇 |
1997年 | 164篇 |
1996年 | 237篇 |
1995年 | 242篇 |
1994年 | 202篇 |
1993年 | 167篇 |
1992年 | 128篇 |
1991年 | 89篇 |
1990年 | 99篇 |
1989年 | 70篇 |
1988年 | 53篇 |
1987年 | 67篇 |
1986年 | 32篇 |
1985年 | 83篇 |
1984年 | 55篇 |
1983年 | 44篇 |
1982年 | 60篇 |
1981年 | 52篇 |
1980年 | 32篇 |
1979年 | 14篇 |
1978年 | 27篇 |
1977年 | 28篇 |
1976年 | 25篇 |
1975年 | 12篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
The TiO2(110) surfaces were observed by a Scanning Tunneling Microscope (STM). We found two types of bright p(1×1)-type rows on the p(1×2) surface. One p(1×1)-type formed independently and corresponds to the bridging oxygen rows. The second p(1×1)-type appeared in a bright grouping, forming narrow rows, and corresponds to the five-fold titanium rows. The above results suggest the following two conclusions. First, the density of state (DOS) on the bridging oxygen rows becomes higher than that on the five-fold titanium atom rows when a bridging oxygen row exists independently on the p(1×2) surface. Second, the bright rows on a TiO2(110)-p(1×1) surface correspond to the five-fold titanium atom rows. The results further show the validity of DOS calculations on the TiO2(110)-p(1×1) surface by Diebold et al. [Phys. Rev. Lett. 77 (1996) 1322]. The difference of width for Ti2O3 unit rows on the p(1×2) and p(1×3) surfaces in STM images are also discussed. 相似文献
102.
We introduce triplet spaces for symmetric relations with defect index (1, 1) in a Pontryagin space. Representations of Pontryagin spaces by spaces of vector-valued analytic functions are investigated. These concepts are used to study 2×2-matrix valued analytic functions which satisfy a certain kernel condition. 相似文献
103.
Helge Glöckner 《manuscripta mathematica》1998,97(2):205-215
Let G be a p-adic Lie group. Then G is a locally compact, totally disconnected group, to which Willis [14] associates its scale function G : G→ℕ. We show that s can be computed on the Lie algebra level. The image of s consists of powers of p. If G is a linear algebraic group over ℚ
p
, s(x)=s(h) is determined by the semisimple part h of x∈G. For every finite extension K of ℚ
p
, the scale functions of G and H:=G(K) are related by s
H
∣
G
=s
G
[
K
:ℚ
p
]. More generally, we clarify the relations between the scale function of
a p-adic Lie group and the scale functions of its closed subgroups and Hausdorff quotients.
Received: 20 February 1997; Revised version: 18 May 1998 相似文献
104.
The aim of this work is to provide a combinatorial resolution of the local components of some automorphic forms of a general
linear group in a suitable way to realize them as transfer of packets of local components of square integrable automorphic
forms for classical groups. We obtain explicit transfer for Arthur’s packets. 相似文献
105.
Resistivity and low field ac susceptibility measurements are made on R: 123 superconducting samples with different rare earth elements R. The order parameter dimensionality OPD is deduced from resistivity versus temperature plot using the Aslamazov and Larkin expression, while the analysis of the temperature dependence of ac susceptibility is done employing Beans’ critical state model and with the help of the Ravi expression. With increasing R, the critical temperatures Tc are nearly kept constant (∼90 K), while the crossover temperatures To are shifted to lower values. Moreover, the superconducting order parameter OPD is shifted toward 2D behavior. On the other hand, the values of superconducting volume fraction fg decrease with increasing ac field amplitude Hm for all samples and it is higher in Er: 123 sample than in Nd: 123 sample. Although the values of critical current density Jc at the peak temperature Tm are nearly unchanged with increasing R, the values of Jc(T), at T<Tm and T>Tm, are found to be dependent on the chosen R. The correlation between the above calculated parameters against R is also mentioned. 相似文献
106.
Elói Medina Galego 《Monatshefte für Mathematik》2002,136(2):87-97
We study the relation of to the subspaces and quotients of Banach spaces of continuous vector-valued functions , where K is an arbitrary dispersed compact set. More precisely, we prove that every infinite dimensional closed subspace of totally incomparable to X contains a copy of complemented in . This is a natural continuation of results of Cembranos-Freniche and Lotz-Peck-Porta. We also improve our result when K is homeomorphic to an interval of ordinals. Next we show that complemented subspaces (resp., quotients) of which contain no copy of are isomorphic to complemented subspaces (resp., quotients) of some finite sum of X. As a consequence, we prove that every infinite dimensional quotient of which is quotient incomparable to X, contains a complemented copy of . Finally we present some more geometric properties of spaces.
Received 8 November 2000; in revised form 7 December 2001 相似文献
107.
Smooth Solutions to Optimal Investment Models with Stochastic Volatilities and Portfolio Constraints
Pham 《Applied Mathematics and Optimization》2002,46(1):55-78
Abstract. This paper deals with an extension of Merton's optimal investment problem to a multidimensional model with stochastic volatility
and portfolio constraints. The classical dynamic programming approach leads to a characterization of the value function as
a viscosity solution of the highly nonlinear associated Bellman equation. A logarithmic transformation expresses the value
function in terms of the solution to a semilinear parabolic equation with quadratic growth on the derivative term. Using a
stochastic control representation and some approximations, we prove the existence of a smooth solution to this semilinear
equation. An optimal portfolio is shown to exist, and is expressed in terms of the classical solution to this semilinear equation.
This reduction is useful for studying numerical schemes for both the value function and the optimal portfolio. We illustrate
our results with several examples of stochastic volatility models popular in the financial literature. 相似文献
108.
Sabine Koppelberg 《Order》1989,5(4):393-406
We introduce the class of minimally generated Boolean algebras, i.e. those algebras representable as the union of a continuous well-ordered chain of subalgebras A
1 where A
i+1 is a minimal extension of A
i. Minimally generated algebras are closely related to interval algebras and superatomic algebras. 相似文献
109.
Aiden A. Bruen 《Acta Appl Math》2006,93(1-3):179-196
We survey some applications of finite fields to finite geometries in part A and to combinatorics and error-correcting codes in parts B and C. 相似文献
110.
Moessbauer studies on the effect of substitution with 3% Al, Co, Mn atoms in the intermetallic compound of Hf0.8Ta0.2Fe2 are reported. The Al substitution leads to increase of the FM-AFM transition temperature and to decrease of the AFM-PM transition temperature. The Co substitution leads to disappearance of the FM state, only showing some FM impurity component, while Mn substituted compound indicates coexistence of FM and AFM states at low temperature. The phenomena imply complex itinerant electron properties in these magnetic systems. 相似文献