全文获取类型
收费全文 | 592篇 |
免费 | 11篇 |
国内免费 | 75篇 |
专业分类
化学 | 463篇 |
晶体学 | 6篇 |
力学 | 1篇 |
综合类 | 5篇 |
数学 | 133篇 |
物理学 | 70篇 |
出版年
2024年 | 2篇 |
2023年 | 51篇 |
2022年 | 25篇 |
2021年 | 22篇 |
2020年 | 60篇 |
2019年 | 30篇 |
2018年 | 16篇 |
2017年 | 28篇 |
2016年 | 14篇 |
2015年 | 6篇 |
2014年 | 19篇 |
2013年 | 78篇 |
2012年 | 43篇 |
2011年 | 49篇 |
2010年 | 20篇 |
2009年 | 26篇 |
2008年 | 40篇 |
2007年 | 22篇 |
2006年 | 21篇 |
2005年 | 18篇 |
2004年 | 21篇 |
2003年 | 18篇 |
2002年 | 11篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
排序方式: 共有678条查询结果,搜索用时 16 毫秒
61.
Single-component molecular conductors [M(tmdt)2] (tmdt = trimethylenetetrathiafulvalenedithiolate; M = Ni, Au, Pt, Cu), exhibit a variety of electromagnetic properties, which originate from the differences of the metal’s d-orbitals role in the band structure formation. The [Au(tmdt)2] crystal undergoes an antiferromagnetic transition at 110 K, while maintaining a metallic state at lower temperatures. The Au analog has a high magnetic transition temperature as compared to traditional magnetic molecular conductors due to the strong three-dimensional (3-D) structure and the contribution of the metal d-orbitals. The single-component molecular conductor, [Cu(tmdt)2], with π- and d-like frontier orbitals is isostructural with other metallic [M(tmdt)2] systems (M = Ni, Pt, Au). The Cu(tmdt)2 molecule is planar, which strikingly contrasts the tetrahedral coordination of Cu(dmdt)2 (dmdt = dimethyltetrathiafulvalenedithiolate) with similarly extended TTF type ligands. Interestingly, unlike other [M(tmdt)2] with metallic behavior, [Cu(tmdt)2] shows semiconducting behavior at room temperature (σ(RT) = ∼7 S cm−1). The RT conductivity increased linearly with increased pressure to 110 S cm−1 at 15 kbar despite the compressed pellet sample. The magnetic susceptibility indicates one-dimensional (1-D) Heisenberg behavior with J = 117 cm−1 and shows antiferromagnetic ordering at 13 K. The [Cu(tmdt)2] is a new multi-frontier π-d system, which introduces a d(σ)-type frontier orbital around the Fermi level of the π-like metal bands. 相似文献
62.
63.
En Ju Wang Guang Ying Chen 《中国化学快报》2011,22(7):847-850
The inclusion complex ofβ-cyclodextrin(β-CD) with 4-chlorobenzoic acid was synthesized and its crystal structure was determined by single crystal X-ray diffraction under cryogenic condition.The complex contains twoβ-CDs,two 4-chlorobenzoic acids and twenty-nine water molecules in the asymmetric unit,and can be formulated as 2(C42H70O35)·2(C7H5O2Cl)·29(H2O).In the crystal lattice,twoβ-CDs form a face-to-face dimer jointed together through hydrogen bonding between the secondary hydroxyl groups ofβ-CDs.Two 4-chlorobenzoic acid molecules which contact by C-Cl…πinteractions are included in theβ-CD dimer cavity.Theβ-CD dimers are arranged in brickwork-like pattern along the crystallographic a-axis.The effect of guest molecule length on the inclusion geometry was discussed by comparative study of someβ-CD complexes containing similar guests. 相似文献
64.
主要讨论局部有限维的Hopf π-代数的π-子代数与Hopf π-子代数,分别得到了Hopf π-代数的π-子代数和Hopf π-子代数的一些充分必要条件. 相似文献
65.
赵士银 《纯粹数学与应用数学》2011,27(1):45-50
设H为有限型Hopfπ-代数,研究Hopfπ-代数H上的Hopfπ-模与Hopf π-余代数H *上的Hopfπ-余模之间的对偶关系,得出了Hopfπ-子模与Hopfπ-子 余模之间的充分必要条件,推广了Hopf代数中的相关结论. 相似文献
66.
For a group G,we produce upper and lower bounds for the sum of the entries of the Brauer character table of G and the projective indecomposable character table of G.When G is a π-separable group,we show that the sum of the entries in the table of Isaacs' partial characters is a real number,and we obtain upper and lower bounds for this sum. 相似文献
67.
A novel complex [Zn(FcCOO)2(2,2′-bipy)(H2O)]2·H2O (Fc = (η5-C5H5)Fe(η5-C5H4), 2,2′-bipy = 2,2′-bipyridine) has been synthesized and characterized by elemental analysis, IR and X-ray diffraction. It crystallizes in monoclinic system, space group P21/c with a = 6.8187(4), b = 21.7155(13), c = 19.7411(12) (A), α = 90, β = 97.7420(10), γ = 90°, C64H58Fe4Zn2N4O11, Mr = 1413.28, V = 2896.4(3) (A)3, Dc = 1.620 g/cm3, Z = 2, F(000) = 1444, μ(MoKα) = 1.857 mm-1, R = 0.0523 and wR = 0.0982 for 3219 observed reflections (I > 2σ(I)). Structural analysis shows that the zinc atom is coordinated with three oxygen atoms from two ferrocenemonocarboxylates and one water molecule together with two nitrogen atoms from 2,2′-bipyridine, giving a distorted square-pyramidal coordination geometry. The complex molecules are linked to form an infinite one-dimensional chain by both intermolecular hydrogen bonds and π-π stacking interactions of the bipyridine rings. 相似文献
68.
Yuji Takahashi 《Proceedings of the American Mathematical Society》1996,124(1):193-196
It is shown that Paschke's result cannot be generalized to the [IN]-group setting given by Lau and Paterson. This resolves negatively a problem raised by Lau and Paterson.
69.
We introduce a new spectral sequence called the p-chain spectral sequence which converges to the (co-)homology of a contravariant C-space with coefficients in a covariant C-spectrum for a small category C. It is different from the corresponding Atiyah–Hirzebruch-type spectral sequence. It can be used in combination with the Isomorphism Conjectures of Baum and Connes and Farrell and Jones to compute algebraic K- and L-groups of group rings and topological K-groups of reduced group C*-algebras. 相似文献
70.