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131.
Nature of Noncovalent Carbon‐Bonding Interactions Derived from Experimental Charge‐Density Analysis 下载免费PDF全文
In an effort to better understand the nature of noncovalent carbon‐bonding interactions, we undertook accurate high‐resolution X‐ray diffraction analysis of single crystals of 1,1,2,2‐tetracyanocyclopropane. We selected this compound to study the fundamental characteristics of carbon‐bonding interactions, because it provides accessible σ holes. The study required extremely accurate experimental diffraction data, because the interaction of interest is weak. The electron‐density distribution around the carbon nuclei, as shown by the experimental maps of the electrophilic bowl defined by a (CN)2C?C(CN)2 unit, was assigned as the origin of the interaction. This fact was also evidenced by plotting the Δ2ρ(r) distribution. Taken together, the obtained results clearly indicate that noncovalent carbon bonding can be explained as an interaction between confronted oppositely polarized regions. The interaction is, thus electrophilic–nucleophilic (electrostatic) in nature and unambiguously considered as attractive. 相似文献
132.
We report a quasi‐classical trajectory study of the S + HO2 reaction using a previously reported global potential energy surface for the ground electronic state of HSO2. Zero‐point energy leakage is approximately accounted for by using the vibrational energy quantum mechanical threshold method. Calculations are carried out both for specific ro‐vibrational states of the reactants and thermalized ones, with rate constants being reported as a function of temperature. The results suggest that the title reaction is capture type, with OH and SO showing as the most favorable products. The internal energy distribution of such products and the reaction mechanism are also investigated. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 533–540, 2008 相似文献
133.
David Qui?onero Antonio Frontera Carolina Garau Pablo Ballester Antoni Costa Pere M Deyà 《Chemphyschem》2006,7(12):2487-2491
The interplay between three important noncovalent interactions involving aromatic rings is studied by means of high level ab initio calculations. They demonstrate that very strong synergic effects are present in complexes where either cation–π or anion–π and π‐‐π interactions coexist. These strong synergic effects have been studied using the “atoms in molecules” theory and the physical nature of the interactions investigated by means of the molecular interaction potential with polarization (MIPp). 相似文献
134.
Ballester L Gil AM Gutiérrez A Perpiñán MF Azcondo MT Sánchez AE Marzin C Tarrago G Bellitto C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(11):2539-2548
The compounds [Cu(Tz)-(MeOH)2](TCNQ)2 (1), [Ni(Tz)-(MeOH)2](TCNQ)2 (2), [Cu(Tz)2]-(TCNQ)7 (3) and [Ni(Tz)2](TCNQ)7 (4) (Tz = 2,7,12,17-tetramethyl-1,6,11,16-tetraazaporphyrinogen) were obtained by metathesis reaction of [M(Tz)](ClO4)2 with LiTCNQ and Et3NH(TCNQ)2, respectively. They were characterized by a combination of spectroscopic and physical methods. Compound 1 crystallizes in the monoclinic space group P2(1)/n with a = 8.310(2), b = 25.180(4), c = 20.727(4) A, beta = 93.58(2) degrees; Z = 4. Compound 3 crystallizes in the triclinic space group P1 with a = 11.244(1), b = 16.700(1), c = 17.321(1) A, a = 113.47(1), beta = 108.52(1), gamma = 96.12(1) degrees; Z = 2. The asymmetric unit of the compound 1 is formed by cationic [Cu(Tz)(MeOH)2]2+ and by two crystallographically non equivalent TCNQ.- anions; these anions form dimeric units by overlap of the pi clouds. The dimers form hydrogen bonds with the metal-lomacrocyclic cation through the methanol ligands. According to this structure the compound is paramagnetic and behaves as an insulator in the temperature range studied. The paramagnetism arises only from the metal-complex moieties. Compound 3 shows an unprecedented structure due to the steric requirements of the macrocycle that favors the stacking of the TCNQ groups. The structure consists of infinite stacks of TCNQ units separated by the metal-macrocyclic units; there are seven TCNQ molecules per formula unit, one of which is formally mono-anionic, while the other six bear one half of an electron per molecule. The copper is six-coordinate in a very distorted octahedral environment. The Tz ligand is located in the equatorial plane and the apical nitrogens of the nitrile groups of two TCNQ molecules complete the coordination around the copper. The compound is a semiconductor and its magnetic behavior can be explained by the sum of the Curie contribution of the metal complex and the contribution arising from the magnetic-exchange interactions of the spins located on the TCNQ units. The latter is found to be typical of one-dimensional antiferromagnetic distorted chains of S = 1/2 spins and can be fitted according to a one-dimensional Heisenberg antiferromagnetic model. 相似文献
135.
Ballester L Gil AM Gutiérrez A Perpiñán MF Azcondo MT Sánchez AE Coronado E Gómez-García CJ 《Inorganic chemistry》2000,39(13):2837-2842
New derivatives of formula [M(dieneN4)](TCNQ)3, M = Ni or Cu and dieneN4 = cis- or trans-hexamethyltetraazacyclotetradecadiene, have been obtained. The TCNQ units show electronic delocalization and formation of 1D stacks, with no direct interactions with the metal cations. The stack is not uniform and can be seen as formed by trimeric dianions (TCNQ)3(2-). The electronic delocalization favors the conductivity in these materials, which behave as good semiconductors. The crystal structures of the trans derivatives have been solved: [Ni(transdieneN4)](TCNQ)3, triclinic, P-1, a = 8.809(2) A, b = 10.896(2) A, c = 13.727(2) A, alpha = 103.04(1) degrees, beta = 101.23(2) degrees, gamma = 109.37(2) degrees, Z = 1; [Cu(trans-dieneN4)](TCNQ)3: triclinic, P-1, a = 7.872(1) A, b = 9.840(1) A, c = 14.819(1) A, alpha = 92.32(1) degrees, beta = 95.05(1) degrees, gamma = 95.66(1) degrees, Z = 1. 相似文献
136.
137.
Mayer RS Henning W Holzmann R Simon RS Delagrange H Lefèvre F Matulewicz T Merrouch R Mittig W Ostendorf RW Schutz Y Berg FD Kühn W Metag V Novotny R Pfeiffer M Boonstra AL Löhner H Venema LB Wilschut HW Ardouin D Dabrowski H Erazmus B Lebrun C Sézac L Ballester F Casal E Díaz J Ferrero JL Marqués M Martínez G Nifenecker H Fornal B Freindl L Sujkowski Z 《Physical review letters》1993,70(7):904-907
138.
Loreto Ballester Oscar Esteban Angel Gutierrez Maria Felisa Perpi an
Caridad Ruiz-Valero
Enrique Gutierrez-PueblaMaria Jesus Gonzalez
《Polyhedron》1992,11(24):3173-3182The complexes [Ru(S,S)2(PPh3)2] [S,S = EtCOCS2−, (CH2)4NCS2−] react with a variety of tertiary phosphines with the substitution of triphenylphosphine and the formation of [Ru(S,S)2(PR3)2]. The reaction occurs with the formation ofthe cis isomer, except for the complex with PMe2Ph that gives rise to the trans isomer as the crystal structure shows. The effect of the different phosphines on the ruthenium complex is analysed in terms of the spectroscopic and electrochemical properties of the isolated compounds. The cyclic voltammetric studies of the cis complexes show that isomerization to the trans isomer occurs on oxidation. This isomerization is not observed in the trans-[Ru(S,S)2(PMe2Ph)2] complexes that give rise to stable trans-ruthenium(II)/ruthenium(III) couples. In a similar way the diphosphine complexes afford a quasi-reversible cis-ruthenium(II)/ruthenium(III) process. 相似文献
139.
M. Ballester J. Veciana J. Riera J. Castañer C. Rovira O. Armet 《Tetrahedron letters》1982,23(48):5075-5078
The first examples of the influence of the free radical character on the reactivity of a non-radical substituent in the radical molecule (reverse effect) are reported. They include thermolysis, reductive dimerization and bromination, involving radicals related to perchlorotriphenylmethyl. 相似文献
140.