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441.
Chandrasekhar V Athimoolam A Reddy ND Nagendran S Steiner A Zacchini S Butcher R 《Inorganic chemistry》2003,42(1):51-59
The reaction of the dicarbaphosphazene, [NC(NMe(2))](2)[NPCl(2)] (2), with the sodium salt of 4-hydroxy-4'-vinylbiphenyl afforded the vinyl group containing monomer [NC(NMe(2))](2)[NP(Cl)(O-C(6)H(4)-p-C(6)H(4)-p-CH=CH(2))] (3). Replacement of the lone chlorine atom of 3 by oxygen nucleophiles gave [NC(NMe(2))](2)[NP(OR)(O-C(6)H(4)-p-C(6)H(4)-p-CH=CH(2))] [R = CH(2)CF(3) (4); C(6)H(5) (5); C(6)H(4)-m-CH(3) (6); C(6)H(4)-p-Br(7)]. The X-ray crystal structures of 3-7 reveal that all the cyclodicarbaphosphazenes have a planar N(3)PC(2) ring; the ring carbons are completely planar, while the geometry around phosphorus is pseudotetrahedral. The presence of weak intermolecular hydrogen bonding [C-H---X(Cl or Br), C-H---N, or C-H---pi] interactions in 3-7 leads to the formation of polymeric architectures in the solid-state. The monomers 4-7 can be polymerized by a free-radical initiator to afford the corresponding air-stable homopolymers 8-11. These have moderate molecular weights with polydispersity indices ranging from 1.33 to 1.58. All of these polymers have high glass transition temperatures and have excellent thermal stability. 相似文献
442.
B. Parthasarathi Chandrasekhar Ursula Schmid Rudolf Schmid Heinz Heimgartner Hans Schmid 《Helvetica chimica acta》1975,58(4):1191-1200
2,2-Dimethyl-3-dimethylamino-2H-azirine ( 1 ) reacts with the formyl-cycloalkanones 4 – 8 in boiling benzene to give the 1:1 adducts 13 – 17 in 60–99% yield (Table). These adducts are N′-[(2-oxo-cycloalkylidene)-methyl] derivatives of 2-amino-N, N-dimethylisobutyramide. The reaction mechanism (Scheme 6) is analogous to the mechanism of the reaction of 1 with carboxylic acids and cyclic enolisable 1,3-diketones [1]. Sulfinic acids and 1 undergo a similar reaction at ?15° to yield 2-sulfinamido-N, N-dimethylisobutyramides (Schemes 4 and 7), while sulfonic acids and the azirine 1 lead to a dimeric salt of type 20 , which with sodium hydroxide gives the dihydropyrazine 21 (Scheme 5). 相似文献
443.
N. Chandrasekhar R. N. Bhave B. S. M. Rao 《Journal of Radioanalytical and Nuclear Chemistry》1985,93(2):73-80
Reactions of recoil38Cl atoms with CCl4 and C6H5Cl have been studied in presence of various high electron density scavengers. Relative reactivities of recoil38Cl towards the two components of these mixtures are determined using the model proposed by Urch. 相似文献
444.
Chandrasekhar V Nagarajan L Gopal K Baskar V Kögerler P 《Dalton transactions (Cambridge, England : 2003)》2005,(19):3143-3145
The synthesis and structure of a novel decanuclear copper(II) cage is reported. The assembly of the cage is facilitated by the cumulative coordinative interaction of tert-butyl phosphonate, 2-pyridylpyrazole and hydroxide ligands with copper(II) ions. Magnetic studies of this decanuclear copper(II) cage indicate complex antiferromagnetic behaviour. 相似文献
445.
Prem K. Mehrotra Jayaraman Chandrasekhar Periakaruppan T. Manoharan Sankaran Subramanian 《Theoretical chemistry accounts》1976,41(3):243-256
The Roby version of the NDDO MO method has been analysed by performing extensive calculations on several molecular systems employing a minimum basis set of STO-3G functions. The effect of using uniform scale factors and those derived from theS-expansion technique, for electron repulsion integrals has also been studied. At the all-electron level, the method, with all its refinements, does not appear promising. The all-valence NDDO MO method after correction byS-expansion, however, yields results which are in good agreement withab initio results. The performance of this scheme is comparable to that of the simplifiedab initio method of Brown and Roby. 相似文献
446.
U. Seshachalam D. V. L. Narasimha Rao B. Haribabu K. B. Chandrasekhar 《Chromatographia》2007,65(5-6):355-358
A forced degradation study was successfully applied for the development of a stability-indicating assay method for the determination
of atazanavir in presence of its degradation products. The method was developed and optimized by analyzing the forcefully
degraded samples. Degradation of the drug was done under acidic, alkaline, oxidative, photolytic and thermal stress conditions.
The proposed method was able to resolve all of the possible degradation products formed during the stress studies. The major
impurities are generated in acidic and alkaline conditions. The product was found stable under thermal, photolytic and oxidative
conditions. The developed method was validated for determination of atazanavir, and the method was found to be equality applicable
to study the impurities formed during routine and forced degradation of atazanavir. 相似文献
447.
A. Singh B. M. Rao G. R. Deshpande S. Sangaraju M. K. Srinivasu M. Lalitha Devi P. V. V. Satyanarayana K. B. Chandrasekhar 《Chromatographia》2007,65(3-4):191-196
A simple and rapid reversed-phase liquid chromatographic method was developed for the related substances determination and
quantitative evaluation of ziprasidone hydrochloride, which is used as an antipsychotic agent. Forced degradation studies
were performed on bulk sample of ziprasidone hydrochloride using acid, base, oxidative hydrolysis, thermal stress and photolytic
degradation. Mild degradation of the drug substance was observed during thermal stress and considerable degradation observed
during base hydrolysis. The chromatographic method was fine tuned using the samples generated from forced degradation studies.
Good resolution between the peaks corresponds to synthetic impurities and degradation products from the analyte were achieved
on YMC Pack Pro C18 column using the mobile phase consists of a mixture of 0.05% v/v of phosphoric acid in water and acetonitrile. The stressed test solutions were assayed against the qualified working standard
of ziprasidone hydrochloride and the mass balance in each case was close to 99.7% indicating that the developed method was
stability-indicating. Validation of the developed method was carried out as per ICH requirements. 相似文献
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