全文获取类型
收费全文 | 193篇 |
免费 | 11篇 |
专业分类
化学 | 146篇 |
晶体学 | 4篇 |
力学 | 1篇 |
数学 | 37篇 |
物理学 | 11篇 |
无线电 | 5篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 7篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 9篇 |
2012年 | 17篇 |
2011年 | 16篇 |
2010年 | 11篇 |
2009年 | 8篇 |
2008年 | 12篇 |
2007年 | 14篇 |
2006年 | 14篇 |
2005年 | 9篇 |
2004年 | 5篇 |
2003年 | 10篇 |
2002年 | 7篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1967年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有204条查询结果,搜索用时 140 毫秒
91.
Arturo Oró Fernando Romeo-Gella Dr. Josefina Perles Dr. Jesús M. Fernández-García Prof. Dr. Inés Corral Prof. Dr. Nazario Martín 《Angewandte Chemie (International ed. in English)》2023,62(49):e202312314
The bottom-up synthesis of 3D tetrakis(hexa-peri-hexabenzocoronenyl)methane, “tetrahedraphene”, is reported. This molecular nanographene constituted by four hexa-peri-hexabenzocoronene (HBC) units attached to a central sp3 carbon atom, shows a highly symmetric arrangement of the HBC units disposed in the apex of a tetrahedron. The X-ray crystal structure reveals a tetrahedral symmetry of the molecule and the packing in the crystal is achieved mostly by CH⋅⋅⋅π interactions since the interstitial solvent molecules prevent the π⋅⋅⋅π interactions. In solution, tetrahedraphene shows the same electrochemical and photophysical properties as the hexa-tBu-substituted HBC (tBu-HBC) molecule. However, upon water addition, it undergoes a fluorescence change in solution and in the precipitated solid, showing an aggregation induced emission (AIE) process, probably derived from the restriction in the rotation and/or vibration of the HBCs. Time-Dependent Density Functional Theory (TDDFT) calculations reveal that upon aggregation, the high energy region of the emission band decreases in intensity, whereas the intensity of the red edge emission signal increases and presents a smoother decay, compared to the non-aggregated molecule. All in all, the excellent correlation between our simulations and the experimental findings allows explaining the colour change observed in the different solutions upon increasing the water fraction. 相似文献
92.
Cadierno V Díez J García-Alvarez J Gimeno J Rubio-García J 《Dalton transactions (Cambridge, England : 2003)》2008,(42):5737-5748
The reactivity of complex [Ru(eta(6)-p-cymene)(kappa(3)P,N,O-Ph(2)PCH(2)P{[double bond, length as m-dash]NP([double bond, length as m-dash]O)(OEt)(2)}Ph(2))][SbF(6)](2) towards a variety of mono- and bidentate neutral ligands has been studied, allowing the high-yield synthesis of the novel half-sandwich Ru(ii) derivatives [Ru(eta(6)-p-cymene)(L)(kappa(2)P,O-Ph(2)PCH(2)P{[double bond, length as m-dash]NP([double bond, length as m-dash]O)(OEt)(2)}Ph(2))][SbF(6)](2) (L = N[triple bond, length as m-dash]CMe , N[triple bond, length as m-dash]CEt , PMe(3), PMe(2)Ph , PMePh(2), PPh(3), P(OMe)(3), P(OEt)(3), P(OPh)(3), py , kappa(1)P-dppm , kappa(1)P-dppe ), as well as the octahedral species [Ru(Ninsertion markN)(2)(kappa(2)P,O-Ph(2)PCH(2)P{[double bond, length as m-dash]NP([double bond, length as m-dash]O)(OEt)(2)}Ph(2))][SbF(6)](2) (Ninsertion markN = bipy , phen ). Deprotonation of complexes ,, upon treatment with an excess of NaOH in CH(2)Cl(2), generates the monocationic derivatives [Ru(Ninsertion markN)(2)(kappa(2)P,N-Ph(2)PC(H)[double bond, length as m-dash]P{NP([double bond, length as m-dash]O)(OEt)(2)}Ph(2))][Cl] (Ninsertion markN = bipy , phen ) in which the methanide anion adopts an unprecedented kappa(2)P,N bidentate coordination mode. The structures of compounds , and have been determined by single-crystal X-ray diffraction methods. 相似文献
93.
Pablo Ríos Hugo Fouilloux Dr. Pietro Vidossich Dr. Josefina Díez Prof. Dr. Agustí Lledós Dr. Salvador Conejero 《Angewandte Chemie (International ed. in English)》2018,57(12):3217-3221
The platinum complex [Pt(ItBuiPr′)(ItBuiPr)][BArF] interacts with tertiary silanes to form stable (<0 °C) mononuclear PtII σ‐SiH complexes [Pt(ItBuiPr′)(ItBuiPr)(η1‐HSiR3)][BArF]. These compounds have been fully characterized, including X‐ray diffraction methods, as the first examples for platinum. DFT calculations (including electronic topological analysis) support the interpretation of the coordination as an unusual η1‐SiH. However, the energies required for achieving a η2‐SiH mode are rather low, and is consistent with the propensity of these derivatives to undergo Si?H cleavage leading to the more stable silyl species [Pt(SiR3)(ItBuiPr)2][BArF] at room temperature. 相似文献
94.
A short proof of the following theorem is given: LetP be a finite partially ordered set. If the maximal number of elements in an independent subset ofP isk, thenP is the union ofk chains. 相似文献
95.
Thek-core of the setS
n
is the intersection of the convex hull of all setsA S with ¦SA¦<-k. The Caratheodory number of thek-core is the smallest integerf (d,k) with the property thatx core
kS, S
n
implies the existence of a subsetT S such thatx corekT and ¦T¦f (d, k). In this paper various properties off(d, k) are established.Research of this author was partially supported by Hungarian National Science Foundation grant no. 1812. 相似文献
96.
María‐Elena Núez Gaytn Sylvain Berns Eduardo Rodríguez de San Miguel Josefina de Gyves 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(8):m414-m417
The title compound, [AuBr(C6H11NS)]n, formed through an AuIIIAuI reduction process, presents a polymeric structure including Au chains with alternating Au—Au distances of 3.0898 (8) and 3.1181 (8) Å. The coordination geometry is best described on the basis of linear [AuBr(C6H11NS)] molecules, which are associated into a one‐dimensional polymer via a common aurophilic interaction. 相似文献
97.
98.
Josefina M. Silveyra Javier A. Moya Victoria J. Cremaschi Du?an Jani?kovi? Peter ?vec 《Hyperfine Interactions》2010,195(1-3):173-177
FINEMET type ribbons (Fe73.5Si13.5Nb3???xMoxB9Cu1, x = 1.5, 2 at.%) were produced by the planar flow casting technique and subsequently heat treated at 823 K to induce nanocrystallization and to optimize its soft magnetic properties. The coercivity, measured by conventional fluxmetric method, resulted in H C?=?0.53 ±0.10 and 0.41±0.05 A/m for x?=?1.5 and 2 respectively. A correlation between magnetic properties and the amorphous and nanocrystalline phases when Nb was partially substituted with Mo was studied by means of Mössbauer spectroscopy and X-ray diffraction. 相似文献
99.
Ana Rosa Lazo Fraga Josefina Calvo Quintana Giovanni Li Destri Nicoletta Giamblanco Roberta Grazia Toro Francesco Punzo 《Journal of Solid State Electrochemistry》2012,16(3):901-909
In this work, we studied an ion-exchange membrane based on an inert polymer skeleton in which it is dispersed and anchored
a molecule with charged groups able to discriminate and bind positive or negatively charged ions present in a sample. In order
to be ready to work, electromembranes need a complex procedure called activation or conditioning. Although most of the known
literature looks at the subject from an electrochemical point of view, we put forward a structural approach. Membrane conditioning,
in fact, is considered a required step to improve sensor performances and to allow the collection of reproducible data. Even
if this operation is carefully followed by all the operators working with sensors equipped with a membrane, it looks like
that a thoroughly explanation of the working mechanism and a detailed balance of cost and gains has still not been carried
out. As a consequence, we suggest a bulk or membrane approach, where the landscape is mainly characterized by the long-range
structure of the membrane itself. Our findings suggest that membrane conditioning has to be carried out carefully and the
advantages of this pre-treatment can be appreciated especially for very low concentration measurements. The need for the conditioning
mainly results from the necessity of a complete permeation of all the different tortuous channels constituting the membrane
itself. 相似文献
100.
Victorio Cadierno Josefina Díez Sergio E. García-Garrido Jos Gimeno Antonio Pizzano 《Polyhedron》2010,29(18):1-3386
A series of cationic rhodium(I) complexes [Rh(diene)(N^N)][BF4] (diene = 1,5-cyclooctadiene (cod), norbornadiene (nbd), tetrafluorobenzobarralene (tfb)), containing the optically pure bis(sulfoximine) ligand 1,2-bis(S-methyl-S-phenylsulfonimidoyl)benzene, have been synthesized and fully characterized. The structure of the R,R enantiomer of the ligand, and that of its cyclooctadiene–Rh(I) complex, were confirmed by means of single-crystal X-ray diffraction techniques. Studies on the catalytic activity of these complexes in acetophenone hydrosilylation and dimethyl itaconate hydrogenation are also reported. 相似文献