全文获取类型
收费全文 | 163篇 |
免费 | 2篇 |
专业分类
化学 | 117篇 |
晶体学 | 5篇 |
力学 | 1篇 |
数学 | 11篇 |
物理学 | 31篇 |
出版年
2023年 | 4篇 |
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 2篇 |
2013年 | 10篇 |
2012年 | 5篇 |
2011年 | 12篇 |
2010年 | 8篇 |
2009年 | 6篇 |
2008年 | 12篇 |
2007年 | 17篇 |
2006年 | 10篇 |
2005年 | 8篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 1篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1988年 | 1篇 |
1985年 | 2篇 |
1981年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有165条查询结果,搜索用时 15 毫秒
71.
Y. Luspin D. De Sousa Meneses P. Simon G. Hauret 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(2):215-221
The elastic properties of Cs3H
(
SeO4
)
2
are investigated by Brillouin spectroscopy in the temperature range 20-220 covering the two transitions III II and II I occurring at and , respectively. Phase I is known to be a protonic conductive one. Discontinuities of elastic constants are generally observed
at both transitions, implying first orderness. In phases II and I, a slight broadening of the Brillouin lines is detected.
The results are discussed in comparison with compounds of the families XHSeO4 (X
=
NH4, Rb and Cs) and CsH2BO4 (B
=
As and P) which also undergo a transition to a superionic phase. In the conductive phase, it appears that the lattice anharmonicity
is weaker in Cs3H
(
SeO4
)
2
than in these other compounds.
Received 16 October 1998 相似文献
72.
Martin Messerschmidt Liane Häußler Brigitte Voit Tilo Krause Wolf-Dieter Habicher 《Macromolecular Symposia》2004,210(1):111-120
Nitroxide mediated free radical polymerization (NMRP) was used for the preparation of orthogonally protected block copolymers based on para-hydroxystyrene. The polymers have a low polydispersity and an active chain end. By a series of polymer analogous reactions, a partly deprotected block copolymer was synthesized consisting of a block with unprotected phenolic OH groups and a further block which is protected by the thermolabile Boc group. 相似文献
73.
Doris Pospiech Liane Hußler Kathrin Eckstein Dieter Jehnichen Antje Gottwald Petra Ptschke 《Macromolecular Symposia》2000,149(1):219-224
One mechanism for compatibilization of immiscible polymer blends is adding block copolymers (BCP) that consist of segments chemically comparable to the parent homopolymers in the blend. BCP do both, emulsify the disperse phase to give smaller particles as well as increase the interfacial adhesion between the phases. The influence of segmented BCP in blends of immiscible high‐performance polymers was investigated systematically by variation of the flexibility of the BCP segments. It was shown that the stiffness of the second segment in polysulfone (PSU) block copolymers as well as the PSU segment molecular weight determine the intermixing between the BCP and the PSU matrix. 相似文献
74.
75.
Yusen Qiao Haolin Yin Liane M. Moreau Rulin Feng Robert F. Higgins Brian C. Manor Patrick J. Carroll Corwin H. Booth Jochen Autschbach Eric J. Schelter 《Chemical science》2021,12(10):3558
A series of cerium(iv) mixed-ligand guanidinate–amide complexes, {[(Me3Si)2NC(NiPr)2]xCeIV[N(SiMe3)2]3−x}+ (x = 0–3), was prepared by chemical oxidation of the corresponding cerium(iii) complexes, where x = 1 and 2 represent novel complexes. The Ce(iv) complexes exhibited a range of intense colors, including red, black, cyan, and green. Notably, increasing the number of the guanidinate ligands from zero to three resulted in significant redshift of the absorption bands from 503 nm (2.48 eV) to 785 nm (1.58 eV) in THF. X-ray absorption near edge structure (XANES) spectra indicated increasing f occupancy (nf) with more guanidinate ligands, and revealed the multiconfigurational ground states for all Ce(iv) complexes. Cyclic voltammetry experiments demonstrated less stabilization of the Ce(iv) oxidation state with more guanidinate ligands. Moreover, the Ce(iv) tris(guanidinate) complex exhibited temperature independent paramagnetism (TIP) arising from the small energy gap between the ground- and excited states with considerable magnetic moments. Computational analysis suggested that the origin of the low energy absorption bands was a charge transfer between guanidinate π orbitals that were close in energy to the unoccupied Ce 4f orbitals. However, the incorporation of sterically hindered guanidinate ligands inhibited optimal overlaps between Ce 5d and ligand N 2p orbitals. As a result, there was an overall decrease of ligand-to-metal donation and a less stabilized Ce(iv) oxidation state, while at the same time, more of the donated electron density ended up in the 4f shell. The results indicate that incorporating guanidinate ligands into Ce(iv) complexes gives rise to intense charge transfer bands and noteworthy electronic structures, providing insights into the stabilization of tetravalent lanthanide oxidation states.A series of cerium(iv) mixed-ligand guanidinate-amide complexes, {[(Me3Si)2NC(NiPr)2]xCeIV[N(SiMe3)2]3−x}+ (x = 0−3), was prepared by chemical oxidation and studied spectroscopically and computationally, revealing trends in 4f/5d orbital occupancies. 相似文献
76.
Claus Hadenfeldt Hans-Ulrich Terschüren Wolfgang Hnle Liane Schrder Hans Georg Von Schnering 《无机化学与普通化学杂志》1993,619(5):843-848
Chemistry and Structural Chemistry of Phosphides and Polyphosphides. 58. Tetrabariumtriphosphide, Ba4P3: Preparation and Crystal Structure Ba4P3 is obtained from the elements in the molar ratio 4:3 or by reaction of Ba3P2 and Ba5P4 in the molar ratio 1:1 (steel ampoules with inner corundum crucibles; 1 490 K). The greyish black, easily hydrolysing compound crystallizes in a new structure type oP56. The structure shows two crystallographically independent dumbbells P24? (d(P? P) = 225 and 232 pm) and isolated ions P3? corresponding to (Ba2+)8(P24?)4(P3?)4. The partial structure of the Ba atoms forms a complex network of trigonal prisms with tetrahedral and square pyramidal holes, as well as polyhedra with 14 faces (CN 10) which are icosahedron derivatives. The P3? anions center trigonal prisms and the 14 face polyhedron. The P-atoms of the P24? dumbbells center neighboring trigonal prisms with common square faces. (Pbam (no. 55); a = 1 325.4(2) pm, b = 1 256.2(2) pm, c = 1 127.3 pm; Z = 8). 相似文献
77.
Electron-beam-irradiated poly(3-hydroxybutyrate) was used as a nucleating agent for poly(3-hydroxybutyrate) in a melt-spinning process. Molecular data and thermal properties of the irradiated samples were determined. The thermal properties of the nucleated melts were determined to assess the influence of the nucleation agents, and then spinning tests were carried out. Thermal and textile properties of the spun fibers were also determined. Estimations of the improvement of the crystallization in the spinline and of the inhibition of secondary crystallization in the fibers from the use of the described blood-compatible nucleation agents are given. 相似文献
78.
Sida Wang Phil Liebing Felix Engelhardt Liane Hilfert Sabine Busse Rüdiger Goldhahn Frank T. Edelmann 《无机化学与普通化学杂志》2023,649(1):e202200289
The current library of amidinate ligands has been extended by the synthesis of two novel dimethylamino-substituted alkynylamidinate anions of the composition [Me2N−CH2−C≡C−C(NR)2]− (R = iPr, cyclohexyl (Cy)). The unsolvated lithium derivatives Li[Me2N−CH2−C≡C−C(NR)2] ( 1 : R = iPr, 2 : R = Cy) were obtained in good yields by treatment of in situ-prepared Me2N−CH2−C≡C−Li with the respective carbodiimides, R−N=C=N−R. Recrystallization of 1 and 2 from THF afforded the crystalline THF adducts Li[Me2N−CH2−C≡C−C(NR)2] ⋅ nTHF ( 1 a : R = iPr, n=1; 2 a : R = Cy, n=1.5). Precursor 2 was subsequently used to study initial complexation reactions with selected di- and trivalent transition metals. The dark red homoleptic vanadium(III) tris(alkynylamidinate) complex V[Me2N−CH2−C≡C−C(NCy)2]3 ( 3 ) was prepared by reaction of VCl3(THF)3 with 3 equiv. of 2 (75 % yield). A salt-metathesis reaction of 2 with anhydrous FeCl2 in a molar ratio of 2 : 1 afforded the dinuclear homoleptic iron(II) alkynylamidinate complex Fe2[Me2N−CH2−C≡C−C(NCy)2]4 ( 4 ) in 69 % isolated yield. Similarly, treatment of Mo2(OAc)4 with 3 or 4 equiv. of 2 provided the dinuclear, heteroleptic molybdenum(II) amidinate complex Mo2(OAc)[Me2N−CH2−C≡C−C(NCy)2]3 ( 5 ; yellow crystals, 50 % isolated yield). The cyclohexyl-substituted title compounds 2 a , 4 , and 5 were structurally characterized through single-crystal X-ray diffraction studies. 相似文献
79.
We consider a zero-surface-tension two-dimensional Hele–Shaw flow in an infinite wedge. There exists a self-similar interface evolution in this wedge, an analogue of the famous Saffman–Taylor finger in a channel, exact shape of which has been given by Kadanoff. One of the main features of this evolution is its infinite time of existence and stability for the Hadamard ill-posed problem. We derive several exact solutions existing infinitely by generalizing and perturbing the one given by Kadanoff. 相似文献
80.
Liane Gabora 《Physics of life reviews》2010,7(2):182-183