全文获取类型
收费全文 | 574篇 |
免费 | 26篇 |
国内免费 | 6篇 |
专业分类
化学 | 424篇 |
晶体学 | 8篇 |
力学 | 31篇 |
数学 | 59篇 |
物理学 | 84篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 13篇 |
2021年 | 21篇 |
2020年 | 14篇 |
2019年 | 15篇 |
2018年 | 18篇 |
2017年 | 12篇 |
2016年 | 17篇 |
2015年 | 15篇 |
2014年 | 25篇 |
2013年 | 40篇 |
2012年 | 53篇 |
2011年 | 37篇 |
2010年 | 27篇 |
2009年 | 31篇 |
2008年 | 29篇 |
2007年 | 37篇 |
2006年 | 25篇 |
2005年 | 31篇 |
2004年 | 24篇 |
2003年 | 25篇 |
2002年 | 25篇 |
2001年 | 7篇 |
2000年 | 15篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 11篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1979年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有606条查询结果,搜索用时 15 毫秒
61.
Masood A. Khan Dennis G. Tuck Michael J. Taylor D. A. Rogers 《Journal of chemical crystallography》1986,16(6):895-905
The crystal structures of the gallium(II) complexes (Ph3PH)2Ga2X6 (X=Cl, Br, I) have been determined. The anions are Ga-Ga bonded species, with staggered ethane conformations; the length of the Ga-Ga bond increases only slightly along the series I>Br>Cl, although there are significant changes in the Ga-Ga stretching force constant in the order Cl>Br>I. The vibrational spectra and derived force constants are discussed, as is the splitting of thev(P-H) [andv(P-D)] mode of the cation which is related to disorder in the structure of the neighboring Ga2X6
2– anions. 相似文献
62.
Boron nitride nanotubes (BNNTs) are semiconductors with a wide band gap. In comparison with carbon nanotubes (CNTs), BNNTs have higher chemical stability, excellent mechanical properties and higher thermal conductivity. In this paper, we study the effect of diameters and substituting B and N atoms of various zigzag BNNTs with Al, on structural and electronic properties of BNNTs in solid state using the density functional theory method. The results of calculations of density of states and band structure (band) showed that the band gap between the valence and conduction level increases as a result of the enhancement of tube diameter of BNNTs. Finally, the results showed that the electronic properties of the pristine BNNTs can be improved by doping Al atom in the zigzag configuration of tubes. 相似文献
63.
Saqib Ali Syed Usman Ahmad Saira Shahzadi Sadiq‐ur‐Rehman Masood Parvez Muhammad Mazhar 《应用有机金属化学》2005,19(1):201-201
Me2Sn(S2CN(CH2)5)Cl contains five‐coordinated tin with a bidentate dithiocarbamate ligand spanning equatorial and axial positions in a distorted trigonal bipyramidal geometry. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
64.
Alexander S. Konev Alexander F. Khlebnikov Kourosch Abbaspour Tehrani 《Journal of fluorine chemistry》2007,128(2):114-119
β-Lactams bearing a Ph2CF substituent at the C(4)-atom were synthesized from N-alkyl-2-fluoro-3,3-diphenylaziridines. The transformation was realized using SbF3-mediated isomerization of the monofluoroaziridines to fluorinated aldimines, followed by Staudinger reaction with ketenes. It was shown that this reaction sequence can be performed as a one-pot procedure. 相似文献
65.
66.
Groux LF Weiss T Reddy DN Chase PA Piers WE Ziegler T Parvez M Benet-Buchholz J 《Journal of the American Chemical Society》2005,127(6):1854-1869
The reactions of a series of Pd(II) methyl compounds of general formula LPd(NCCH(3))CH(3), where L is a bulky phenoxydiazene or phenoxyaldimine ligand with the polar olefin acrylonitrile (AN), are reported. The compounds react with an excess of AN to give the products of 2,1 insertion into the Pd-Me bond, yielding dimers and/or trimers which feature bridging alpha-cyano groups. The reactions were studied by low temperature (1)H NMR spectroscopy, revealing an initial formation of compounds featuring N-bound AN, which isomerized to an (unobserved) pi-bound species that rapidly underwent 2,1 insertion into the Pd-Me bond. Intermediate oligomeric complexes retaining a Pd-Me function were observed at low [AN] in these reactions. Under pseudo first-order conditions, k(obs) values of 8.5 x 10(-5) to 2.68 x 10(-3) M(-1) (-22 degrees C to 10 degrees C, 100 equiv of AN) and activation parameters of DeltaH++ = 14.4(5) kcal mol(-1) and DeltaS++ = -19(5) eu were obtained in one case. Comparison of the overall rates of insertion between two LPd(NCCH(3))CH(3), differing in the overall charge on the supporting ligand L, showed that the complex bearing a negatively charged ligand reacts with AN twice as fast as one with no anionic charge. The rates of insertion in both of these complexes are significantly faster than reported rates for analogous reactions in cationic Pd(II) derivatives, indicating that increasing the negative charge on the complex enhances the rate of AN insertion. These results provide fundamental mechanistic insights into a crucial reaction for incorporation of polar comonomers into alpha olefins via a coordination polymerization mechanism. 相似文献
67.
Reactions of nitrosobenzene and N,N'-diethyl-4-nitrosoaniline with [Cu(CH3CN)4]PF6 produce novel homoleptic Cu(I)-nitrosoarene complexes, [Cu(ArNO)3]PF6, 1 (Ar = Ph) and 2 (Ar = 4-Et2NC6H4NO). The X-ray structure of 2 reveals that the copper is coordinated in a severely distorted trigonal planar geometry to the N-atom of the nitrosoarene ligand. Reactions of the PhNO complex 1 with olefins and an olefin/diene mixture provide evidence for its role as an intermediate and possibly the active nitrogen transfer agent in the Cu-catalyzed allylic amination of olefins by aryl hydroxylamines. 相似文献
68.
Lewis SP Henderson LD Chandler BD Parvez M Piers WE Collins S 《Journal of the American Chemical Society》2005,127(1):46-47
Lewis acidic, chelating diborane 1 forms stable oxonium acids 2 in the presence of excess MeOH or water. Diborane 1 is shown to be an effective co-initiator for the suspension polymerization of isobutene in aqueous media at sufficiently low temperatures. Poly(isobutene) or butyl rubber is obtained at moderate to high conversion and with Mw < 200 K and PDI approximately 2 under these conditions. 相似文献
69.
Létant SE Kane SR Hart BR Hadi MZ Cheng TC Rastogi VK Reynolds JG 《Chemical communications (Cambridge, England)》2005,(7):851-853
We report on the immobilization of an OPAA enzyme on luminescent porous silicon devices, and on the utilization of this new platform to hydrolyze p-nitrophenyl-soman. 相似文献
70.
Ly HV Forster TD Maley D Parvez M Roesler R 《Chemical communications (Cambridge, England)》2005,(35):4468-4470
A heterocyclic cyclopentadienyl analog containing only one carbon atom in the ring was prepared and a polymeric lithiocene and a monomeric zincocene containing this novel ligand have been isolated and crystallographically characterized. 相似文献