全文获取类型
收费全文 | 417篇 |
免费 | 65篇 |
国内免费 | 38篇 |
专业分类
化学 | 113篇 |
晶体学 | 14篇 |
力学 | 21篇 |
综合类 | 9篇 |
数学 | 162篇 |
物理学 | 201篇 |
出版年
2023年 | 4篇 |
2022年 | 16篇 |
2021年 | 14篇 |
2020年 | 21篇 |
2019年 | 17篇 |
2018年 | 15篇 |
2017年 | 19篇 |
2016年 | 18篇 |
2015年 | 9篇 |
2014年 | 6篇 |
2013年 | 37篇 |
2012年 | 13篇 |
2011年 | 25篇 |
2010年 | 23篇 |
2009年 | 13篇 |
2008年 | 25篇 |
2007年 | 18篇 |
2006年 | 22篇 |
2005年 | 24篇 |
2004年 | 26篇 |
2003年 | 19篇 |
2002年 | 18篇 |
2001年 | 13篇 |
2000年 | 14篇 |
1999年 | 13篇 |
1998年 | 40篇 |
1997年 | 15篇 |
1996年 | 7篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有520条查询结果,搜索用时 15 毫秒
21.
D. E. Daney M. P. Maley H. J. Boenig J. O. Willis J. Y. Coulter L. Gherardi G. Coletta 《Physica C: Superconductivity and its Applications》1998,310(1-4):236-239
We report single-phase AC loss measurements on 8-, 4-, and 3-layer, multi-strand, HTS prototype conductors for power transmission lines. We use both calorimetric and electrical techniques. The agreement between the two techniques suggests that the interlayer current distribution in 1-m long conductors are representative of those in long conductors. The losses for the 8- and 4-layer conductors are in rough agreement, with the 8-layer losses being somewhat lower. The 3-layer conductor losses are substantially higher — probably due to unbalanced azimuthal currents for this configuration. 相似文献
22.
For two covariant differential *-calculi, the twisted cyclic cocycle associated with the volume form is represented in terms of commutators
for some self-adjoint operator
and some *-representation of the underlying *-algebra. 相似文献
23.
Varghese Mathai 《Geometriae Dedicata》2003,99(1):1-15
We outline a twisted analogue of the Mishchenko–Kasparov approach to prove the Novikov conjecture on the homotopy invariance of the higher signatures. Using our approach, we give a new and simple proof of the homotopy invariance of the higher signatures associated to all cohomology classes of the classifying space that belong to the subring of the cohomology ring of the classifying space that is generated by cohomology classes of degree less than or equal to 2, a result that was first established by Connes and Gromov and Moscovici using other methods. A key new ingredient is the construction of a tautological C*
r
(, )-bundle and connection, which can be used to construct a C*
r
(, )-index that lies in the Grothendieck group of C*
r
(, ), where is a multiplier on the discrete group corresponding to a degree 2 cohomology class. We also utilise a main result of Hilsum and Skandalis to establish our theorem. 相似文献
24.
The non-commutative torus C
*(n,) is realized as the C*-algebra of sections of a locally trivial C*-algebra bundle over S with fibres isomorphic to C
*n/S, 1) for a totally skew multiplier 1 on n/S. D. Poguntke [9] proved that A
is stably isomorphic to C(S) C(*( Zn/S, 1) C(S) A Mkl( C) for a simple non-commutative torus A and an integer kl. It is well-known that a stable isomorphism of two separable C*-algebras is equivalent to the existence of equivalence bimodule between them. We construct an A-C(S) A-equivalence bimodule. 相似文献
25.
回顾介绍了葛庭燧院士的生平和他在科学研究、人才培养方面所作出的贡献,展示了他的高尚情操,分析了他取得卓著成就的原因. 相似文献
26.
Demand for increased data storage has resulted in the development of various types of magnetic tapes. To achieve higher recording density, tape manufacturers are developing thin-film tapes, such as advanced metal-evaporated (AME) tape, for use in linear tape drives. In recent studies, these new AME tapes have demonstrated sustainable mechanical durability at low tensions suitable for use in linear tape drives. An evaluation of the magnetic performance of these AME tapes including the impact of tape cupping and initial edge quality was the goal of this study. Head output, dropouts, head–tape interface friction, and lateral tape motion (LTM) were monitored throughout testing. As track widths continue to narrow, LTM has become one of the critical limitations of magnetic performance. To more accurately measure LTM during drive development, a new method involving the output voltage of a head-read element that has been adjusted to be halfway off the recorded track on tape was implemented (LTMM). It is shown that positively cupped AME tapes will result in similar head output and fewer dropouts than the current MP tapes. The negatively cupped AME sample produced the lowest head output data and the highest amount of dropouts of all the tapes evaluated in this investigation. All the tapes evaluated demonstrated similar values of LTM when monitored at the center of the tape. When LTM was monitored at the lower edge of the tape, the positively cupped AME tape with the worst relative edge contour length resulted in the highest LTMM. As found in previous studies, AME tapes produced slightly lower values of coefficient of friction than the MP tapes. From this investigation, positively cupped AME tapes with good initial relative edge contour length are recommended for use in linear tape drives, similar to those used in this study. 相似文献
27.
We prove that a group generated by a twisted subset is finite and its order is bounded by some function depending only on the order of the twisted subset. 相似文献
28.
Ying-bo Han 《高校应用数学学报(英文版)》2008,23(1):65-68
A class of twisted special Lagrangian submanifolds in T*R^n and a kind of austere submanifold from conormal bundle of minimal surface of R^3 are constructed. 相似文献
29.
Koji Kano Ryuhei Nishiyabu 《Journal of inclusion phenomena and macrocyclic chemistry》2002,44(1-4):355-359
A general mechanism for chiral recognition by native and modified cyclodextrins hasbeen proposed by reconsidering the data reported so far. Cyclodextrins in aqueoussolution adopt asymmetrically twisted structures, which seems to be the origin of chiralrecognition. 相似文献
30.
In this paper, we define a P-twisted affine Lie algebra, and construct its realizations by twisted vertex operators. 相似文献