全文获取类型
收费全文 | 1884篇 |
免费 | 48篇 |
国内免费 | 6篇 |
专业分类
化学 | 1182篇 |
晶体学 | 9篇 |
力学 | 45篇 |
数学 | 228篇 |
物理学 | 474篇 |
出版年
2022年 | 10篇 |
2021年 | 16篇 |
2020年 | 20篇 |
2019年 | 23篇 |
2017年 | 14篇 |
2016年 | 35篇 |
2015年 | 29篇 |
2014年 | 25篇 |
2013年 | 76篇 |
2012年 | 75篇 |
2011年 | 84篇 |
2010年 | 40篇 |
2009年 | 37篇 |
2008年 | 85篇 |
2007年 | 86篇 |
2006年 | 76篇 |
2005年 | 87篇 |
2004年 | 86篇 |
2003年 | 66篇 |
2002年 | 63篇 |
2001年 | 47篇 |
2000年 | 47篇 |
1999年 | 33篇 |
1998年 | 29篇 |
1997年 | 19篇 |
1996年 | 39篇 |
1995年 | 32篇 |
1994年 | 22篇 |
1993年 | 26篇 |
1992年 | 40篇 |
1991年 | 23篇 |
1990年 | 17篇 |
1989年 | 17篇 |
1988年 | 32篇 |
1987年 | 22篇 |
1986年 | 19篇 |
1985年 | 28篇 |
1984年 | 19篇 |
1983年 | 29篇 |
1982年 | 35篇 |
1981年 | 27篇 |
1980年 | 24篇 |
1979年 | 26篇 |
1978年 | 20篇 |
1977年 | 20篇 |
1976年 | 27篇 |
1975年 | 25篇 |
1974年 | 21篇 |
1973年 | 16篇 |
1970年 | 14篇 |
排序方式: 共有1938条查询结果,搜索用时 15 毫秒
41.
Abe K Akagi T Anthony PL Antonov R Arnold RG Averett T Band HR Bauer JM Borel H Bosted PE Breton V Button-Shafer J Chen JP Chupp TE Clendenin J Comptour C Coulter KP Court G Crabb D Daoudi M Day D Dietrich FS Dunne J Dutz H Erbacher R Fellbaum J Feltham A Fonvieille H Frlez E Garvey D Gearhart R Gomez J Grenier P Griffioen KA Hoibraten S Hughes EW Hyde-Wright C Johnson JR Kawall D Klein A Kuhn SE Kuriki M Lindgren R Liu TJ Lombard-Nelsen RM Marroncle J Maruyama T Maruyama XK McCarthy J Meyer W 《Physical review letters》1995,74(3):346-350
42.
43.
44.
45.
The PH bond of dialkylphosphites (dimethylphosphite, 5,5-dimethyl-1,3-dioxa-2-phosphorinane and 4,4,5,5-tetramethyl-1,3-dioxa-2-phospholane) oxidatively adds to irClL2(L = PPh3, AsPh3) and IrCl(PMe2Ph)3 generated in situ to give six-coordinate hydrido(dialkylphosphonato)iridium(III) complexes, e.g. IrHClL2[{(MeO)2-PO}2H] and IrHCl(PMe2Ph)3[PO(OMe)2]. Addition of triphenylphosphine to a solution containing [IrCl(C8H14)2]2 and dimethylphosphite in a 1:2 mol ratio gives a five-coordinate hydrido (dimethylphosphonato)iridium(III) complex IrHCl(PPh3)2{PO(OMe)2}, from which six-coordinate pyridine and acetylacetonato complexes IrHCl(PPh3)2(C5H5N){PO(OMe)2} and IrH(PPh3)2(acac){PO(OMe)2} can be obtained. The ligand arrangements in the various complexes are inferred from IR, 1H and 31P NMR data. 相似文献
46.
J. A. Moore T. D. Mitchell 《Journal of polymer science. Part A, Polymer chemistry》1983,21(5):1305-1314
Polyenaminoesters were prepared by condensation of succinyl succinic ester (SSE) and p-bis-carbomethoxy diacetyl benzene (CDB) with 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane. Conditions of solvent and temperature were discovered which yielded soluble polymer from SSE after heat treatment. CDB yields only tough, rubbery, insoluble products. 相似文献
47.
A sensitive method for the detection and quantitation of lysergic acid diethylamide (LSD) in urine was developed. After initial solvent extraction, the compound was further purified by liquid-liquid extraction or by solid-phase extraction. The trimethylsilyl derivative of LSD was detected by gas chromatography-mass spectrometry (GC-MS) operated in the electron-impact mode with selected-ion monitoring. The presence of LSD was confirmed by comparing retention times and relative abundances of ions of unknowns with that of a standard. The recovery of this procedure was greater than 89%. The intra-run and inter-run coefficients of variation were less than 5% and less than 7%, respectively. This procedure allows detection of LSD concentrations as low as 29 pg/ml. Quantitation of LSD was linear over the concentration range 50-2000 pg/ml. 相似文献
48.
Vyskocil S Meca L Tislerová I Císarová I Polásek M Harutyunyan SR Belokon YN Stead RM Farrugia L Lockhart SC Mitchell WL Kocovský P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(20):4633-4648
The title binaphthyls 19 and 26, which are the positional isomers of 2-methoxy-2'-(diphenylphosphino)-1,1'-binaphthyl (MOP, 19) and 2-amino-2'-hydroxy-1,1'-binaphthyl (NOBIN, 26), have been synthesized by Suzuki coupling as the key step (10 + 15-->18), followed by functional group transformations, involving C-P and C-N bond formation (18-->19 and 18-->23). Racemic intermediate 22 was resolved by co-crystallization with N-benzylcinchonidinium chloride and the absolute configuration determined by X-ray crystallography. These novel binaphthyls are configurationally stable and, as such, potentially usable as chiral ligands in asymmetric reactions. Michael addition of the glycine-derived enolate 40 to methyl acrylate, carried out in the presence of (R)-(-)-27 as the chiral phase-transfer catalyst, afforded L-glutamic acid (S)-(+)-43 of 92% ee (after hydrolysis of the primary product). 相似文献
49.
We investigate the static and dynamic behaviors of a Br adlayer electrochemically deposited onto single-crystal Ag(100) using an off-lattice model of the adlayer. Unlike previous studies using a lattice-gas model, the off-lattice model allows adparticles to be located at any position within a two-dimensional approximation to the substrate. Interactions with the substrate are approximated by a corrugation potential. Using density functional theory (DFT) to calculate surface binding energies, a sinusoidal approximation to the corrugation potential is constructed. A variety of techniques, including Monte Carlo and Langevin simulations, are used to study the behavior of the adlayer. The lateral root-mean-square (rms) deviation of the adparticles from the binding sites is presented along with equilibrium coverage isotherms, and the thermally activated Arrhenius barrier-hopping model used in previous dynamic Monte Carlo simulations is tested. 相似文献
50.
Molecular mechanics and dynamics calculations have been used in conjunction with experimental data to study the effects of amine ligand bulk on the formation of both guanine and methionine complexes with platinum diamine compounds. The AMBER force field has been supplemented with previous modifications [Yao; et al. Inorg. Chem. 1994, 33, 6061-6077. Cerasino; et al. Inorg. Chem. 1997, 36, 6070-6079] and has been further modified to include parameters for platinum bound to the sulfur atom of methionine. Molecular mechanics calculations with this modified AMBER force field have suggested that a platinum complex with two sulfur-bound methionine ligands and a bulky diamine ligand (N,N,N',N'-tetramethylethylenediamine, Me(4)en) would have severe interligand clashes; such interligand clashes are less pronounced in bis(9-ethylguanine) complexes. Consistent with these observations, NMR studies with [Pt(Me(4)en)(D(2)O)(2)](2+) have indicated that guanine 5'-monophosphate reacts in a 2:1 guanine:platinum ratio while both methionine and N-acetylmethionine react with only a 1:1 stoichiometry. Methionine forms a chelate via the sulfur and nitrogen atoms whereas N-acetylmethionine forms a chelate via the sulfur and oxygen atoms. The oxygen of the latter chelate can be displaced by the addition of guanosine 5'-monophosphate, although complete displacement of the N-acetylmethionine was not observed. 相似文献