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81.
Shubina LK Kalinovsky AI Makarieva TN Fedorov SN Dyshlovoy SA Dmitrenok PS Kapustina II Mollo E Utkina NK Krasokhin VB Denisenko VA Stonik VA 《Natural product communications》2012,7(4):487-490
Three new sulfated meroterpenoids containing sesquiterpene and hydroquinone moieties, namely siphonodictyal A sulfate (1), akadisulfate A (2) and akadisulfate B (3), along with the known siphonodictyal B3 and bis(sulfato)-cyclosiphonodictyol A were isolated from the sponge Aka coralliphaga. Their structures were elucidated on the basis of spectroscopic data. Akadisulfate B and siphonodictyal B3 showed a radical-scavenging activity comparable with that of the known lipophylic antioxidant BHT. 相似文献
82.
D. R. Atanasov N. Winckler D. Balabanski L. Batist F. Bosch D. Boutin C. Brandau C. Dimopoulou H. G. Essel T. Faestermann H. Geissel I. Hachiuma S. Hess T. Izumikawa P. Kienle R. Kn?bel C. Kozhuharov J. Kurcewicz N. Kuzminchuk S. A. Litvinov Yu. A. Litvinov R. S. Mao R. M?rtin M. Mazzocco G. Münzenberg K. Namihira F. Nolden T. Ohtsubo Z. Patyk R. Reuschl M. S. Sanjari C. Scheidenberger D. Shubina U. Spillmann M. Steck Th. St?hlker B. Sun T. Suzuki M. Trassinelli I. I. Tupitsyn H. Weick M. Winkler D. F. A. Winters T. Yamaguchi 《The European Physical Journal A - Hadrons and Nuclei》2012,48(2):1-6
The half-lives of fully ionized and hydrogen-like (H-like) 122I ions have been measured in a heavy-ion storage ring. The $ \beta^{+}_{}$ -decay constants for both charge states and the electron capture (EC) decay constant of H-like ions have been determined. The EC-decay constant in H-like 122I ions $\ensuremath \lambda^{\text{H-like}}_{\rm EC}=7.35(33)\cdot10^{-4}{\,\mbox{s}}^{-1}$ is, within the uncertainty, the same as the one in neutral atoms. This result is in agreement with the estimates of recent theoretical considerations on the EC-decay of few-electron ions that explicitly take into account the conservation of the total angular momentum of the nucleus plus lepton(s) system and its projections. No firm confirmation could be concluded from our results on the predicted effect that allowed Gamow-Teller transitions become forbidden if the initial and final total angular momenta are not equal.-1 相似文献
83.
The reaction between aquacobalamin, Cbl(H2O), and NO was studied at low pH. As previously reported, the final product of the reaction is the same as that obtained in the reaction of NO and reduced Cbl(H2O), viz. Cbl(NO-). Nevertheless, this reductive nitrosylation is preceded by a faster reaction (accompanied by small absorbance changes) that depends on the HNO2 concentration but not on the NO concentration. Kinetic and UV-vis spectroscopic data show that Cbl(NO2-) is generated during this reaction. Spectroscopic data show that the dimethylbenzimidazole group trans to the NO2- ligand is protonated and partially dechelated at pH 1, by which a reaction with NO is induced. DFT calculations were performed to compare the ability of NO and NO2- to bind to cobalamin and their influence on the stability of the dimethylbenzimidazole group. The reductive nitrosylation reaction shows a quadratic dependence on the HNO2 concentration and an inverse dependence on the NO concentration. It also strongly depends on pH and is no longer observed at pH > 4. On the basis of earlier work performed on a series of Co(III) porphyrins, a mechanism is proposed that can quantitatively account for the HNO2 and NO dependencies. The reductive nitrosylation reaction is practically dominated by a back reaction, i.e., the reaction between Cbl(NO-) and HNO2, which accounts for the strange NO and HNO2 concentration dependencies observed. 相似文献
84.
A. A. Toporov T. V. Shubina S. V. Ivanov S. V. Sorokin A. V. Lebedev P. S. Kop’ev G. R. Pozina P. Bergman B. Monemar 《Physics of the Solid State》1998,40(5):770-771
The low-temperature photoluminescence spectrum and the recombination dynamics of localized excitons have been studied in a
short-period superlattice of CdSe/ZnSe submonolayers. As distinct from structures with isolated submonolayers, which exhibit
one narrow photoluminescence peak, the photoluminescence and photoluminescence excitation spectra of a superlattice have two
peaks, separated by ∼50 meV. The amount of splitting, as well as the temporal characteristics of the damping of the photoluminescence,
are interpreted in terms of a model of a disordered superlattice of extended islands, sited randomly in the submonolayers
making up the superlattice.
Fiz. Tverd. Tela (St. Petersburg) 40, 837–838 (May 1998) 相似文献
85.
Larisa K. Shubina Oleg S. Radchenko Sophia A. Kolesnikova Ann Bode Valentin A. Stonik 《Tetrahedron letters》2005,46(4):559-562
Two new diprenylquinones, glabruquinone A (desmethylubiquinone Q2) having cancer preventive properties and its minor isomer Glabruquinone B were isolated from the ascidian Aplidium glabrum. Their structures have been elucidated by NMR and mass spectra and confirmed by synthesis. 相似文献
86.
Béthegnies A Kirkina VA Filippov OA Daran JC Belkova NV Shubina E Polic R 《Inorganic chemistry》2011,50(24):12539-12552
The RhCl(3)·3H(2)O/PPh(3)/nBu(4)PI catalytic system for the hydroamination of ethylene by aniline is shown to be thermally stable by a recycle experiment and by a kinetic profile study. The hypothesis of the reduction under catalytic conditions to a Rh(I) species is supported by the observation of a high catalytic activity for complex [RhI(PPh(3))(2)](2). New solution equilibrium studies on [RhX(PPh(3))(2)](2) (X = Cl, I) in the presence of ligands of relevance to the catalytic reaction (PPh(3), C(2)H(4), PhNH(2), X(-), and the model Et(2)NH amine) are reported. Complex [RhCl(PPh(3))(2)](2) shows broadening of the (31)P NMR signal upon addition of PhNH(2), indicating rapid equilibrium with a less thermodynamically stable adduct. The reaction with Et(2)NH gives extensive conversion into cis-RhCl(PPh(3))(2)(NHEt(2)), which is however in equilibrium with the starting material and free Et(2)NH. Excess NHEt(2) yields a H-bonded adduct cis-RhCl(PPh(3))(2)(Et(2)NH)···NHEt(2), in equilibrium with the precursors, as shown by IR spectroscopy. The iodide analogue [RhI(PPh(3))(2)](2) shows less pronounced reactions (no change with PhNH(2), less extensive addition of Et(2)NH with formation of cis-RhI(PPh(3))(2)(NHEt(2)), less extensive reaction of the latter with additional Et(2)NH to yield cis-RhI(PPh(3))(2)(Et(2)NH)···NHEt(2). The two [RhX(PPh(3))(2)](2) compounds do not show any evidence for addition of the corresponding X(-) to yield a putative [RhX(2)(PPh(3))(2)](-) adduct. The product of C(2)H(4) addition to [RhI(PPh(3))(2)](2), trans-RhI(PPh(3))(2)(C(2)H(4)), has been characterized in solution. Treatment of the RhCl(3)·3H(2)O/PPh(3)/nBu(4)PI/PhNH(2) mixture under catalytic conditions yields mostly [RhCl(PPh(3))(2)](2), and no significant halide exchange, demonstrating that the promoting effect of iodide must take place at the level of high energy catalytic intermediates. The equilibria have also been investigated at the computational level by DFT with treatment at the full QM level including solvation effects. The calculations confirm that the bridge splitting reaction is slightly less favorable for the iodido derivative. Overall, the study confirms the active role of rhodium(I) species in ethylene hydroamination catalyzed by RhCl(3)·3H(2)O/PPh(3)/nBu(4)PI and suggest that the catalyst resting state is [RhCl(PPh(3))(2)](2) or its C(2)H(4) adduct, RhCl(PPh(3))(2)(C(2)H(4)), under high ethylene pressure. 相似文献
87.
88.
Background
Our previous work described the neural processes of motor response inhibition during a stop signal task (SST). Employing the race model, we computed the stop signal reaction time (SSRT) to index individuals' ability in inhibitory control. The pre-supplementary motor area (preSMA), which shows greater activity in individuals with short as compared to those with long SSRT, plays a role in mediating response inhibition. In contrast, the right inferior prefrontal cortex (rIFC) showed greater activity during stop success as compared to stop error. Here we further pursued this functional differentiation of preSMA and rIFC on the basis of an intra-subject approach. 相似文献89.
The advantages of relative analytical methods over absolute methods for calculating element concentrations have been demonstrated. A procedure for the neutron activation analysis of samples of unknown composition was proposed based on the numerical simulation of the gamma spectra of test samples. 相似文献
90.
N. L. Komissarova I. S. Belostotskaya O. V. Shubina V. V. Ershov V. N. Voznesenskii I. I. Chervin 《Russian Chemical Bulletin》1988,37(9):1966-1966
Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, p. 2186, September, 1988. 相似文献