全文获取类型
收费全文 | 143篇 |
免费 | 6篇 |
国内免费 | 1篇 |
专业分类
化学 | 93篇 |
晶体学 | 1篇 |
力学 | 9篇 |
数学 | 23篇 |
物理学 | 24篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 7篇 |
2014年 | 4篇 |
2013年 | 8篇 |
2012年 | 7篇 |
2011年 | 10篇 |
2010年 | 3篇 |
2009年 | 10篇 |
2008年 | 7篇 |
2007年 | 10篇 |
2006年 | 6篇 |
2005年 | 8篇 |
2004年 | 3篇 |
2003年 | 5篇 |
2002年 | 2篇 |
2001年 | 5篇 |
2000年 | 9篇 |
1999年 | 1篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1987年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有150条查询结果,搜索用时 15 毫秒
51.
Jorge J. Carbó Dr. Noelia Martínez‐Espada Miguel Mena Dr. Marta E. G. Mosquera Dr. Josep‐M. Poblet Prof. Carlos Yélamos Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(43):11619-11631
The Lewis base behavior of μ3‐nitrido ligands of the polynuclear titanium complexes [{Ti(η5‐C5Me5)(μ‐NH)}3(μ3‐N)] ( 1 ) and [{Ti(η5‐C5Me5)}4(μ3‐N)4] ( 2 ) to MX Lewis acids has been observed for the first time. Complex 1 entraps one equivalent of copper(I ) halide or copper(I ) trifluoromethanesulfonate through the basal NH imido groups to give cube‐type adducts [XCu{(μ3‐NH)3Ti3(η5‐C5Me5)3(μ3‐N)}] (X=Cl ( 3 ), Br ( 4 ), I ( 5 ), OSO2CF3 ( 6 )). However, the treatment of 1 with an excess (≥2 equiv) of copper reagents afforded complexes [XCu{(μ3‐NH)3Ti3(η5‐C5Me5)3(μ4‐N)(CuX)}] (X=Cl ( 7 ), Br ( 8 ), I ( 9 ), OSO2CF3 ( 10 )) by incorporation of an additional CuX fragment at the μ3‐N nitrido apical group. Similarly, the tetranuclear cube‐type nitrido derivative 2 is capable of incorporating one, two, or up to three CuX units at the μ3‐N ligands to give complexes [{Ti(η5‐C5Me5)}4(μ3‐N)4?n{(μ4‐N)CuX}n] (X=Br ( 11 ), n=1; X=Cl ( 12 ), n=2; X=OSO2CF3 ( 13 ), n=3). Compound 2 also reacts with silver(I ) trifluoromethanesulfonate (≥1 equiv) to give the adduct [{Ti(η5‐C5Me5)}4(μ3‐N)3{(μ4‐N)AgOSO2CF3}] ( 14 ). X‐ray crystal structure determinations have been performed for complexes 8 – 13 . Density functional theory calculations have been carried out to understand the nature and strength of the interactions of [{Ti(η5‐C5H5)(μ‐NH)}3(μ3‐N)] ( 1′ ) and [{Ti(η5‐C5H5)}4(μ3‐N)4] ( 2′ ) model complexes with copper and silver MX fragments. Although coordination through the three basal NH imido groups is thermodynamically preferred in the case of 1′ , in both complexes the μ3‐nitrido groups act as two‐electron donor Lewis bases to the appropriate Lewis acids. 相似文献
52.
We prove that weakly compact operators on a non-reflexive normed space cannot be bijective. We also show that, in the above result, bijectivity cannot be relaxed to surjectivity. Finally, we study the behaviour of surjective weakly compact operators on a non-reflexive normed space, when they are perturbed by small scalar multiples of the identity, and derive from this study the recent result of Spurný [A note on compact operators on normed linear spaces, Expo. Math. 25 (2007) 261–263] that compact operators on an infinite-dimensional normed space cannot be surjective. 相似文献
53.
María García‐Castro Dr. Avelino Martín Dr. Miguel Mena Dr. Carlos Yélamos Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(29):7180-7191
Several heterometallic nitrido complexes were prepared by reaction of the imido–nitrido titanium complex [{Ti(η5‐C5Me5)(μ‐NH)}3(μ3‐N)] ( 1 ) with amido derivatives of Group 13–15 elements. Treatment of 1 with bis(trimethylsilyl)amido [M{N(SiMe3)2}3] derivatives of aluminum, gallium, or indium in toluene at 150–190 °C affords the single‐cube amidoaluminum complex [{(Me3Si)2N}Al{(μ3‐N)2(μ3‐NH)Ti3(η5‐C5Me5)3(μ3‐N)}] ( 2 ) or the corner‐shared double‐cube compounds [M(μ3‐N)3(μ3‐NH)3{Ti3(η5‐C5Me5)3(μ3‐N)}2] [M=Ga ( 3 ), In ( 4 )]. Complexes 3 and 4 were also obtained by treatment of 1 with the trialkyl derivatives [M(CH2SiMe3)3] (M=Ga, In) at high temperatures. The analogous reaction of 1 with [{Ga(NMe2)3}2] at 110 °C leads to [{Ga(μ3‐N)2(μ3‐NH)Ti3(η5‐C5Me5)3(μ3‐N)}2] ( 5 ), in which two [GaTi3N4] cube‐type moieties are linked through a gallium–gallium bond. Complex 1 reacts with one equivalent of germanium, tin, or lead bis(trimethylsilyl)amido derivatives [M{N(SiMe3)2}2] in toluene at room temperature to give cube‐type complexes [M{(μ3‐N)2(μ3‐NH)Ti3(η5‐C5Me5)3(μ3‐N)}] [M=Ge ( 6 ), Sn ( 7 ), Pb ( 8 )]. Monitoring the reaction of 1 with [Sn{N(SiMe3)2}2] and [Sn(C5H5)2] by NMR spectroscopy allows the identification of intermediates [RSn{(μ3‐N)(μ3‐NH)2Ti3(η5‐C5Me5)3(μ3‐N)}] [R=N(SiMe3)2 ( 9 ), C5H5 ( 10 )] in the formation of 7 . Addition of one equivalent of the metalloligand 1 to a solution of lead derivative 8 or the treatment of 1 with a half equivalent of [Pb{N(SiMe3)2}2] afford the corner‐shared double‐cube compound [Pb(μ3‐N)2(μ3‐NH)4{Ti3(η5‐C5Me5)3(μ3‐N)}2] ( 11 ). Analogous antimony and bismuth derivatives [M(μ3‐N)3(μ3‐NH)3{Ti3(η5‐C5Me5)3(μ3‐N)}2] [M=Sb ( 12 ), Bi ( 13 )] were obtained through the reaction of 1 with the tris(dimethylamido) reagents [M(NMe2)3]. Treatment of 1 with [AlCl2{N(SiMe3)2}(OEt2)] affords the precipitation of the singular aluminum–titanium square‐pyramidal aggregate [{{(Me3Si)2N}Cl3Al2}(μ3‐N)(μ3‐NH)2{Ti3(η5‐C5Me5)3(μ‐Cl)(μ3‐N)}] ( 14 ). The X‐ray crystal structures of 5 , 11 , 13 , 14 , and [AlCl{N(SiMe3)2}2] were determined. 相似文献
54.
In this work, the rectilinear Poiseuille flow of a complex liquid flowing in a vibrating pipe is analyzed. The pipe wall performs
oscillations of small amplitude that can be adequately represented by a weakly stochastic process, for which a quasi-static
perturbation solution scheme is suggested. The flow is analyzed using the Bautista–Manero–Puig constitutive equation, consisting
on the upper-convected Maxwell equation coupled to a kinetic equation to account for the breakdown and reformation of the
fluid structure. A drastic enhancement of the volumetric flow is predicted in the region where the fluid experiences pronounced
shear-thinning. Finally, flow enhancement is predicted using experimental data reported elsewhere for wormlike micellar solutions
of cetyl trimethyl ammonium tosilate. 相似文献
55.
C. Ortiz E. Mena M. Sabido J. Socorro 《International Journal of Theoretical Physics》2008,47(5):1240-1251
Using the WKB-like and Hamilton procedures classical solutions to commutative and noncommutative cosmology are found. This
is carried out in the Bianchi type I cosmological model coupled to barotropic perfect fluid and cosmological constant. Noncommutativity
is achieved by modifying the symplectic structure considering that minisuperspace variables do not commute, using a deformation
between all the minisuperspace variables. It is shown that the anisotropic parameter β
±nc
for some value in the Λ cosmological term and noncommutative θ parameter, present a dynamical isotropization until a critical cosmic time t
c
. After this time the effects of minisuperspace noncommutativity in the isotropization seem to disappear. 相似文献
56.
57.
García-Castro M Martín A Mena M Pérez-Redondo A Yélamos C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(3):647-651
Treatment of [(Ti(eta5-C5Me5)(mu-NH))3(mu3-N)] with alkali metal bis(trimethylsilyl)amido reagents in toluene afforded the complexes [M(mu3-N)(mu3-NH)2[Ti3(mu5-C5Me5)3(mu3-N)]]2 (M = Li (2), Na, (3), K (4)). The molecular structures of 2 and 3 have been determined by X-ray crystallographic studies and show two azaheterometallocubane cores [MTi3N4] linked by metal-nitrogen bonds. Reaction of the lithium derivative 2 with chlorotrimethylsilane or trimethyltin chloride in toluene gave the incomplete cube nitrido complexes [Ti3(eta5-C5Me5)3(mu-NH)2(mu-NMMe3)(mu3-N)] (M = Si (5), Sn (6)). A similar reaction with indium(I) or thallium(I) chlorides yielded cube-type derivatives [M(mu3-N)(mu3-NH)2[Ti(eta5-C5Me5)3(mu3-N)] (M=In (7), Tl (8)). 相似文献
58.
Egea Gonzalez FJ Mena Granero A Glass CR Garrido Frenich A Martinez Vidal JL 《Rapid communications in mass spectrometry : RCM》2004,18(5):537-543
A multiresidue method for determining more than 70 pesticides in air has been validated using a single injection with gas chromatography/tandem mass spectrometry (GC/MS/MS). The method validation considered both stages of sampling and analysis. The sampling method, based on active sampling using sorption in sorbent cartidges, was validated by generating standard atmospheres. Performance parameters of the method were evaluated, with a reduction in the limits of quantification by injecting a higher volume of sample extract, and increase of selectivity by the use of MS/MS detection mode. The method was based on solid-phase extraction, which permits a degree of automation. The best adsorbents were found to be Chromosorb 106 and Tenax TA. The retention capacity of these sampling sorbents allows up to 1440 L of air to be sampled without any breakthrough for most of the compounds. Data were generated for assessing the potential exposure of bystanders. The application of the method to the analysis of the air in urban locations near agricultural areas showed that pesticides were present in most of the samples. 相似文献
59.
Freitag K Gracia J Martín A Mena M Poblet JM Sarasa JP Yélamos C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(17):3645-3651
Treatment of [[Ti(eta5-C5Me5)(mu-NH)]3(mu3-N)] (1) with the diolefin complexes [[MCl(cod)]2] (M = Rh, Ir; cod = 1,5-cyclooctadiene) in toluene afforded the ionic complexes [M-(cod)(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)]Cl [M = Rh (2), Ir (3)]. Reaction of complexes 2 and 3 with [Ag(BPh4)] in dichloromethane leads to anion metathesis and formation of the analogous ionic derivatives [M(cod)(mu3-NH)3Ti3-(eta5-C5Me5)3(mu3-N)][BPh4] [M = Rh (4), Ir (5)]. An X-ray crystal structure determination for 5 reveals a cube-type core [IrTi3N4] for the cationic fragment, in which 1 coordinates in a tripodal fashion to the iridium atom. Reaction of the diolefin complexes [[MCl(cod))2] (M = Rh, Ir) and [[RhCl(C2H4)2]2] with the lithium derivative [[Li(mu3-NH)2(mu3-N)-Ti3(eta5-C5Me5)3(mu3-N)]2] x C7H8 (6 C7H8) in toluene gave the neutral cube-type complexes [M(cod)(mu-NH)2(mu3-N)Ti3-(eta5-C5Me5)3(mu3-N)] [M = Rh (7), Ir (8)] and [Rh(C2H4)2(mu3-NH)2(mu3-N)Ti3(eta5-C5Me5)3(mu3-N)] (9), respectively. Density functional theory calculations have been carried out on the ionic and neutral azaheterometallocubane complexes to understand their electronic structures. 相似文献
60.
González-del Moral O Martín A Mena M Morales-Varela Mdel C Santamaría C 《Chemical communications (Cambridge, England)》2005,(29):3682-3684
Treatment of the mu3-ethylidyne complex [{TiCp*(mu-O)}3(mu3-CMe)](1), (Cp*=eta5-C5Me5) with alkali metal amides leads to the oxoheterometallocubane derivatives [M(mu3-O)3{(TiCp*)3(mu3-CCH2)}] [M = Li (2), Na (3), K (4), Rb (5), Cs (6)] containing the naked carbanion mu3-CCH2-; the addition of triphenylmethanol and tert-butanol to the compounds 2-6 gives rise to the oxoderivatives [{TiCp*(mu-O)}3(mu-CHMe)(OCR3)][R = Me (7), Ph (8)] which show a mu-ethylidene bridge on the surface model Ti3O3. 相似文献