全文获取类型
收费全文 | 1588篇 |
免费 | 85篇 |
国内免费 | 11篇 |
专业分类
化学 | 1054篇 |
晶体学 | 6篇 |
力学 | 49篇 |
数学 | 264篇 |
物理学 | 190篇 |
无线电 | 121篇 |
出版年
2023年 | 15篇 |
2022年 | 21篇 |
2021年 | 27篇 |
2020年 | 23篇 |
2019年 | 32篇 |
2018年 | 26篇 |
2017年 | 16篇 |
2016年 | 44篇 |
2015年 | 56篇 |
2014年 | 62篇 |
2013年 | 75篇 |
2012年 | 108篇 |
2011年 | 124篇 |
2010年 | 60篇 |
2009年 | 63篇 |
2008年 | 103篇 |
2007年 | 102篇 |
2006年 | 104篇 |
2005年 | 75篇 |
2004年 | 82篇 |
2003年 | 74篇 |
2002年 | 60篇 |
2001年 | 20篇 |
2000年 | 20篇 |
1999年 | 24篇 |
1998年 | 14篇 |
1997年 | 17篇 |
1996年 | 20篇 |
1995年 | 13篇 |
1994年 | 15篇 |
1993年 | 9篇 |
1992年 | 11篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1989年 | 6篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 13篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 11篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 7篇 |
排序方式: 共有1684条查询结果,搜索用时 93 毫秒
1.
We define admissible quasi-Hopf quantized universal enveloping (QHQUE) algebras by ?-adic valuation conditions. We show that any QHQUE algebra is twist-equivalent to an admissible one. We prove a related statement: any associator is twist-equivalent to a Lie associator. We attach a quantized formal series algebra to each admissible QHQUE algebra and study the resulting Poisson algebras. 相似文献
2.
Peixiang Xing Gilles P. Robertson Michael D. Guiver Serguei D. Mikhailenko Serge Kaliaguine 《Journal of polymer science. Part A, Polymer chemistry》2004,42(12):2866-2876
A series of sulfonated poly(aryl ether ketone)s (SPAEKs) were prepared by aromatic nucleophilic polycondensation of 2,6‐dihydroxynaphthalene with 5,5′‐carbonyl‐bis(2‐fluorobenzenesulfonate) and 4,4′‐difluorobenzophenone. The structure and degree of sulfonation (DS) of the SPAEKs were characterized using 1H NMR spectroscopy. The experimentally observed DS values were close to the expected values derived from the starting material ratios. The thermal stabilities of the SPAEKs were characterized by thermogravimetric analysis, which showed that in acid and sodium salt forms they were thermally stable in air up to about 240 and 380 °C, respectively. Transparent membranes cast from the directly polymerized SPAEKs exhibited good mechanical properties in both dry and hydrated states. The dependence of water uptake and of membrane swelling on the DS at different temperatures was studied. SPAEK membranes with a DS from 0.72 to 1.60 maintained adequate mechanical properties after immersion in water at 80 °C for 24 h. The proton conductivity of SPAEK membranes with different degrees of sulfonation was measured as a function of temperature. The proton conductivity of the SPAEK films increased with increased DS, and the highest room temperature conductivity (4.2 × 10?2 S/cm) was recorded for a SPAEK membrane with a DS of 1.60, which further increased to 1.1 × 10?1 S/cm at 80 °C. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2866–2876, 2004 相似文献
3.
In order to replace silicones in some of their biomedical applications, e.g. syringe lubrication, implants ets., a series of digermoxanes (R1R2R3Ge)2O (R = n–alkyl, aryl) were synthesized. These compounds are thermally stable oils; their viscosities, depending on the nature of substituents, lie in the range 1–72 cPo (mPa s) at 20°C. 相似文献
4.
5.
Anne Boutet De Monvel-Berthier Louis Boutet De Monvel Gilles Lebeau 《Journal d'Analyse Mathématique》1992,58(1):39-60
Sans résumé
Dedicated to Professor Shmuel Agmon 相似文献
6.
Communicated by Charles A. Micchelli. 相似文献
7.
GillesBonnet YuzhongShen 《电信技术》2003,(5):36-38
第二代(2G)移动网络和传统的固定网络都提供了一套相对完整的话音业务。尽管智能网络(IN)技术使电信业务有所增强,但电信业务的发展仍然缓慢,而且样式基本保持不变。下一代网络(NGN)和第三代(3G)移动网络就是为了克服这些局限性而设计的,它们通过重组网络架构将业务同网络分离开来、将信息和电话技术融合起来并引进了会话初始协议(SIP)等开放协议。同时,它们还有望提供满足用户和运营商需求的新的增值业务。这些网络包括满足用户对业务期望所需的所有组成部分。NGN和3G就其服务能力而言有3个主要优点:首先,它们将信息世界和电话世界结… 相似文献
8.
Denis Prat Françoise Benedetti Lahlou Nait Bouda Gilles Franc Girard 《Tetrahedron letters》2004,45(4):765-768
An industrial synthesis of 11β-aryl-estrone derivatives is described, based on the 1,4-addition of the aryl side-chain, as a cuprate, on to a mixture of allylic 5(10) alpha and beta epoxides, followed by hydrolysis and subsequent aromatization. 相似文献
9.
Gilles Carron 《Journal of Functional Analysis》2004,212(1):222-260
We give a formula for the jump at zero of the spectral shift function associated with Schrödinger operator on manifolds with conical ends. We show that, according to its decay, a zero energy resonant state has a non-integer contribution. 相似文献
10.
Quantization consists in studying the L
r
-error induced by the approximation of a random vector X by a vector (quantized version) taking a finite number n of values. We investigate this problem for Gaussian random vectors in an infinite dimensional Banach space and in particular, for Gaussian processes. A precise link proved by Fehringer(4) and Dereich et al.
(3) relates lower and upper bounds for small ball probabilities with upper and lower bounds for the quantization error, respectively. We establish a complete relationship by showing that the same holds for the direction from the quantization error to small ball probabilities. This allows us to compute the exact rate of convergence to zero of the minimal L
r
-quantization error from logarithmic small ball asymptotics and vice versa. 相似文献