全文获取类型
收费全文 | 369篇 |
免费 | 13篇 |
国内免费 | 1篇 |
专业分类
化学 | 291篇 |
晶体学 | 11篇 |
力学 | 2篇 |
数学 | 24篇 |
物理学 | 55篇 |
出版年
2023年 | 4篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 16篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2016年 | 5篇 |
2015年 | 7篇 |
2014年 | 3篇 |
2013年 | 37篇 |
2012年 | 22篇 |
2011年 | 20篇 |
2010年 | 12篇 |
2009年 | 7篇 |
2008年 | 14篇 |
2007年 | 23篇 |
2006年 | 15篇 |
2005年 | 24篇 |
2004年 | 19篇 |
2003年 | 17篇 |
2002年 | 18篇 |
2001年 | 4篇 |
2000年 | 11篇 |
1999年 | 10篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 10篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 1篇 |
1973年 | 3篇 |
1969年 | 2篇 |
1968年 | 3篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1962年 | 1篇 |
1954年 | 1篇 |
1927年 | 1篇 |
排序方式: 共有383条查询结果,搜索用时 15 毫秒
1.
Pennington DA Coles SJ Hursthouse MB Bochmann M Lancaster SJ 《Chemical communications (Cambridge, England)》2005,(25):3150-3152
The mono(salicylaldiminato) complexes Ti{3-tBu-2-(O)C6H3CH=N(R)}Cl3(THF)(where R = C6H5, C6F5) react with the metallated pyrrolylaldiminato ligand, K[2-(C6H5NCH)C4H3N], to afford the first examples of hybrid salicylaldiminato-ligated octahedral titanium complexes; the pre-catalysts give from very high to extremely high ethene polymerisation productivities when activated with MAO. 相似文献
2.
Birch SJ Boss SR Cole SC Coles MP Haigh R Hitchcock PB Wheatley AE 《Dalton transactions (Cambridge, England : 2003)》2004,(21):3568-3574
Dimethylzinc reacts with an excess of N-2-pyridylaniline 6 to give the homoleptic species, Zn[PhN(2-C(5)H(4)N)](2) 8. Single crystal X-ray diffraction reveals a solid-state dimer based on an 8-membered (NCNZn)(2) core motif. Zn[CyN(2-C(5)H(4)N)]Me (Cy =c-C(6)H(11)) 10, prepared by the combination of ZnMe(2) with the corresponding cyclohexyl-substituted pyridylamine, is also dimeric in the solid state but reveals a central (ZnN)(2) metallacycle. Employment of (p-Tol)NH(2-C(5)H(4)N)(p-Tol = 4-MeC(6)H(4)) 11 yielded the tris(zinc) adduct Zn(3)[(p-Tol)N(2-C(5)H(4)N)](4)Me(2) 12, which incorporates a central chiral molecule of 'Zn[(p-Tol)N(2-C(5)H(4)N)](2)' 12a, that bridges two 'Zn[(p-Tol)N(2-C(5)H(4)N)]Me' 12b units. A similar trimetallic structure is noted when the pyridylaniline substrate 11 is replaced with the bicyclic guanidine 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hppH), affording Zn(3)(hpp)(4)Me(2) 13. Spectroscopic studies point to retention of the solid-state structure of in hydrocarbon solution. Reaction of 13 with dimesityl borinic acid, Mes(2)BOH (Mes = mesityl), affords Zn(3)(hpp)(4)(OBMes(2))(2) 14 in which the trimetallic core is retained. This reactivity is in contrast to the closely related reaction of dimeric Zn[Me(2)NC[N(i)Pr](2)]Me 15 with Mes(2)BOH, which yielded Zn[Me(2)NC[N(i)Pr](2)][OBMes(2)].Me(2)NC[N(i)Pr][NH(i)Pr] 16 as a result of protonation at the guanidine ligand in addition to the Zn-Me bond. 相似文献
3.
The two independent elements of the second-order nonlinear optical susceptibility tensor of a range of contact poled, donor–acceptor substitued side-chain polymers are reported. The susceptibilities were measured by second harmonic generation from thin films, typically less than 0.5 μm thick, at a fundamental wavelength of 1064 nm. The largest value was χ = 2.64 pm/V which is three times greater than the χ value of KDP and was measured in a nitrobenzylidene side chain, polyhydroxystyrene polymer with an eleven unit alkyl chain spacer attaching the side group to the backbone. Typical susceptibility values obtained were χ~0.3 pm/V and X(2)33~1 pm/V. The coherence lengths of the materials, which lay in the range 4–12 μm, were measured at 1064 nm by the maker fringe technique using thick, wedge-shaped samples. 相似文献
4.
P. T. H. Fisk M. J. Sellars M. A. Lawn C. Coles 《Applied physics. B, Lasers and optics》1995,60(6):519-527
A microwave frequency standard based on buffer gas-cooled171Yb+ ions confined in a linear Paul trap has been demonstrated in prototype form. The standard exhibits a fractional frequency instability characterised by an Allan deviation of (y() = 2.9 × 10–13–1/2 for < 2 × 104 s. Factors affecting the stability of the standard have been systematically investigated. 相似文献
5.
6.
7.
8.
The mild (DCM/20 °C), quantitative, regioselective, O-acylative cleavage of tetrahydrofurans using organic acid halides with catalytic Bi(III) halides is reported. X-ray crystallography is used to rationalise the failure of the reaction in the case of certain crowded acid chlorides, and a useful aspect of chemoselectivity is revealed. The synthetic potential of this reaction is illustrated with a highly efficient O-acylative cleavage/intramolecular alkylation approach to tetralins. 相似文献
9.
Pennington DA Clegg W Coles SJ Harrington RW Hursthouse MB Hughes DL Light ME Schormann M Bochmann M Lancaster SJ 《Dalton transactions (Cambridge, England : 2003)》2005,(3):561-571
The silyl ethers 3-But-2-(OSiMe3)C6H3CH=NR (2a-e) have been prepared by deprotonation of the known iminophenols (1a-e) and treatment with SiClMe3 (a, R = C6H5; b, R = 2,6-Pri2C6H3; c, R = 2,4,6-Me3C6H2; d, R = 2-C6H5C6H4; e, R = C6F5). 2a-c react with TiCl4 in hydrocarbon solvents to give the binuclear complexes [Ti{3-But-2-(O)C6H3CH=N(R)}Cl(mu-Cl3)TiCl3] (3a-c). The pentafluorophenyl species 2e reacts with TiCl4 to give the known complex Ti{3-But-2-(O)C6H3CH=N(R)}2Cl2. The mononuclear five-coordinate complex, Ti{3-But-2-(O)C6H3CH=N(2,4,6-Me3C6H2)}Cl3 (4c), was isolated after repeated recrystallisation of 3c. Performing the dehalosilylation reaction in the presence of tetrahydrofuran yields the octahedral, mononuclear complexes Ti{3-But-2-(O)C6H3CH=N(R)}Cl3(THF) (5a-e). The reaction with ZrCl4(THF)2 proceeds similarly to give complexes Zr{3-But-2-(O)C6H3CH=N(R)}Cl3(THF) (6b-e). The crystal structures of 3b, 4c, 5a, 5c, 5e, 6b, 6d, 6e and the salicylaldehyde titanium complex Ti{3-But-2-(O)C6H3CH=O}Cl3(THF) (7) have been determined. Activation of complexes 5a-e and 6b-e with MAO in an ethene saturated toluene solution gives polyethylene with at best high activity depending on the imine substituent. 相似文献
10.
Neil Bricklebank Simon J. Coles Michael B. Hursthouse Peter J. Skabara 《Journal of organometallic chemistry》2005,690(2):328-332
The title compound, Fc2(Ph)PS · I2, has been prepared and characterised in both the solid state and solution. Single crystal X-ray crystallography reveals that the adduct adopts a molecular charge-transfer structure in the solid state. Mössbauer spectroscopy confirms the presence of low spin Fe2+ but also indicates the presence of ca. 24% of an Fe3+ species. The electrochemistry of Fc2(Ph)PS · I2, Fc2(Ph)PS and Fc2(Ph)P has been studied using a combination of cyclic voltammetry and differential pulse voltammetry. The data for Fc2(Ph)PS · I2 show two redox processes, consistent with the sequential oxidation of the ferrocenyl groups to ferrocenium species. 相似文献