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121.
S. P. Gromov A. I. Vedernikov L. G. Kuz’mina N. A. Lobova S. S. Basok Yu. A. Strelenko M. V. Alfimov 《Russian Chemical Bulletin》2009,58(1):108-114
Due to hydrogen bonding, bis(18-crown-6) stilbene forms 1 : 1, 1 : 2, and 2 : 2 complexes with H3N+(CH2)
n
NH3
+ 2ClO4
− salts (n = 2—10, 12). The length of the polymethylene chain in the diammonium ions affects the phototransformation direction of stilbene
and the composition of the products. In the 2: 2 bispseudosandwich complexes with relatively short alkanediammonium ions (n = 2—4), the stereoselective reaction of [2+2] photocycloaddition proceeds to form mainly the rctt-isomer of the cyclobutane derivative. The structure of rctt-cyclobutane derivative as a complex with H3N+(CH2)4NH3
+2ClO4
- was confirmed by X-ray diffraction analysis. 相似文献
122.
M. K. Pham M. Betti P. P. Povinec V. Alfimov D. Biddulph J. Gastaud W. E. Kieser J. M. López Gutiérrez G. Possnert J. A. Sanchez-Cabeza T. Suzuki 《Journal of Radioanalytical and Nuclear Chemistry》2010,286(1):121-127
A certified reference material designed for the determination of 129I in seawater, IAEA-418 (Mediterranean Sea water) is described and the results of certification are presented. The median of 129I concentration with 95% confidence interval was chosen as the most reliable estimates of the true value. The median, given as the certified value, is 2.28 × 108 atom L?1 (95% confidence interval is (2.16–2.73) 108 atom L?1), or 3.19 × 10?7 Bq L?1 (95% confidence interval is (3.02–3.82) × 10?7 Bq L?1). The material is intended to be used for standardization procedures applied in accelerator mass spectrometric laboratories. It is available in 1 L units and may be ordered via IAEA web side (www.iaea.org). 相似文献
123.
A. V. Odinokov M. V. Bazilevskii N. Kh. Petrov A. K. Chibisov M. V. Alfimov 《High Energy Chemistry》2010,44(5):376-382
A model describing the effect of counterion X− (X = Cl, I) on the deactivation kinetics of the S
1 state of thiacarbocyanine Cy+X− is presented. According to the model, the ion pair Cy+X− in a binary solution is characterized by a distribution function f(r) over interatomic distances r, which depends on the composition of the mixture. The assumption of kinetically independent local states of the ion pair,
which decay with the rate constants k
i(r)(i = 1–4 is the index of the decay channel), is made. The statistic analysis of the experimental data in terms of the model
permitted us to find the functions f(r) and to estimate the parameters of the constants k
i(r). 相似文献
124.
M. V. Rusalov B. M. Uzhinov M. V. Alfimov S. P. Gromov 《Russian Chemical Bulletin》2010,59(6):1207-1216
Spectrophotometry and steady-state fluorimetry were used for the study of complexation of crown-containing butadienyl dyes
with alkali and alkaline earth metal cations in acetonitrile, as well as protonation of these dyes with trifluoroacetic acid.
Complexation of the compounds studied with the metal cations leads to the 1: 1 product, whereas protonation with trifluoroacetic
acid affords the 1: 2 product containing 2 moles of the acid per 1 mole of the dye. Stability constants of the complexes are
varied from 10 to 106 L mol−1, basicity of the crown-containing dyes in the reaction with trifluoroacetic acid increases with the increase in the macrocycle
size. On complexation, the fluorescence spectra are shifted considerably less than the absorption spectra. This indicates
that photorecoordination of the cation in the complex excited molecules occurred. Based on the correlation of the spectral
shifts with the metal cation charge density, three types of complexes differing in the extent of influence of the cation charge
on the spectral shifts can be singled out: “tight”, “loose”, and “solvent-separated”. 相似文献
125.
Artem I. Vedernikov Evgeny N. Ushakov Lyudmila G. Kuz'mina Andrei V. Churakov Yuri A. Strelenko Michael W?rner André M. Braun Judith A. K. Howard Michael V. Alfimov Sergey P. Gromov 《Journal of Physical Organic Chemistry》2010,23(3):195-206
Benzothiazole type butadienyl dyes containing a dithia‐15‐crown‐5 ( 2a ) or dithia‐18‐crown‐6 ether ( 2b ) moieties were synthesized. The structures of dyes 2a , b and their complexes with Ag+ and Pb2+ were studied by an X‐ray crystallography. It was found that the conformations of dithiacrown–ether moieties of dyes 2a , b are unfavorable for complex formation and change significantly upon binding of Ag+ or Pb2+. The complexation of 2a , b with Ag+, Cd2+, Pb2+, and Hg2+ in water–acetonitrile mixtures with different contents of water (PW = 0–75%, v/v) was studied by 1H NMR, UV–Vis spectroscopy, and polarography. In anhydrous acetonitrile, the stability constants of 1:1 complexes change in the sequence Cd2+ < Pb2+ ≤ Ag+ << Hg2+ in the case of 2a and in the sequence Cd2+ < Ag+ < Pb2+ << Hg2+ in the case of 2b . As PW increases, the thermodynamic stability of Ag+ complexes increases. The opposite effect is observed for the complexes with Cd2+, Pb2+, and Hg2+. When PW ~ 50%, the stability constants of complexes with Cd2+ and Pb2+ become too small to be measured. The selectivity of ligands 2a , b toward Hg2+ versus Ag+ is very high at any PW values (selectivity coefficients > 104). The complexation of 2a , b with Hg2+ at PW ≤ 50% is accompanied by a substantial hypsochromic effect. This allows dithiacrown‐containing butadienyl dyes to be used as selective optical molecular sensors for heavy metal ions, in particular, in aqueous solutions. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
126.
Highly nonlinear photonic-crystal fibers for the spectral transformation of Cr: forsterite laser pulses 总被引:1,自引:0,他引:1
A.B. Fedotov E.E. Serebryannikov D.A. Sidorov-Biryukov A.V. Shcherbakov M.V. Alfimov 《Optics Communications》2006,267(2):505-510
We demonstrate novel photonic-crystal fibers (PCFs) fabricated of a highly nonlinear glass. Dispersion profiles and nonlinearity of these fibers are tailored with an array of submicron holes in the fiber core. With the PCF structure designed to provide a nonlinearity on the order of 103 W−1 km−1 at the radiation wavelength of 1 μm and a fundamental-mode dispersion profile with zero group-velocity dispersion around 1.19 μm, unamplified femtosecond Cr: forsterite laser pulses are efficiently frequency-converted into the 540-1000-nm wavelength range through solitonic spectral-transformation mechanisms and four-wave mixing. 相似文献
127.
Cross-phase-modulation-induced instability and efficient parametric frequency conversion of ultrashort light pulses 总被引:1,自引:0,他引:1
E. E. Serebryannikov S. O. Konorov A. A. Ivanov M. V. Fedorov M. V. Alfimov A. M. Zheltikov 《Journal of Experimental and Theoretical Physics》2006,102(5):707-711
We experimentally demonstrate efficient controlled parametric frequency conversion of femtosecond laser pulses through cross-phase-modulation-induced instability in the presence of a copropagating pump field in a fused silica photonic-crystal fiber. The amplitudes and the frequency shifts of sidebands generated in the spectrum of the probe field at the output of the fiber as a result of parametric four-wave mixing are controlled by varying the intensity of the pump field. 相似文献
128.
S. O. Konorov A. A. Ivanov D. A. Akimov A. V. Yakimanskii M. V. Alfimov A. M. Zheltikov 《JETP Letters》2004,80(3):167-171
Third-harmonic and sum-frequency generation in quadratically nonlinear azopolymer films is experimentally studied using femtosecond chromium forsterite laser pulses. A noncollinear geometry of sum-frequency and third-harmonic generation developed and implemented in this work allows the influence of the time ordering of ultrashort laser pump pulses on nonlinear-optical phenomena to be experimentally observed. Femtosecond laser pulses induce transitions of azopolymer molecules to an electronically excited state and produce vibrational wave packets, leading to an asymmetry in the dependence of the efficiency of second-and third-order nonlinear-optical processes on the delay time between the pump pulses. 相似文献
129.
S. P. Gromov A. I. Vedernikov Yu. V. Fedorov O. A. Fedorova E. N. Andryukhina N. E. Shepel' Yu. A. Strelenko D. Johnels U. Edlund J. Saltiel M. V. Alfimov 《Russian Chemical Bulletin》2005,54(7):1569-1579
In the presence of Ba2+ ions, (benzothiazolyl)ethenylbenzocrown ether forms the stable sandwich complex 2L⋅Ba2+ with an unusual structure, in which the benzothiazole fragments are arranged one above the other. Irradiation of the sandwich
complex with visible light induces stereoselective [2+2] cycloaddition giving rise to two “head-to-head” isomers of biscrown-cyclobutane.
The addition of dibasic dicarboxylic acids that additionally stabilize the sandwich complex in a favorable conformation affects
the isomer ratio of the cyclobutanes formed. The conformational equilibria for the sandwich complex and cyclobutanes were
studied by 1H NMR spectroscopy.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1524–1533, July, 2005. 相似文献
130.
D. A. Ivanov N. Kh. Petrov M. V. Alfimov A. I. Vedernikov S. P. Gromov 《High Energy Chemistry》2014,48(4):253-259
Photolysis of aqueous solutions of styryl dye 1 in the presence of cucurbit[8]uril (CB[8]) has been studied by optical spectroscopic methods for the molar ratios n = c CB[8]/c 1 in the range of 0 ≤ n ≤ 6. It has been found that the inclusion complexes (1)2@CB[8] dominate in the solution at n ≤ 0.5, whereas the complexes 1@CB[8] dominate at n ≥ 1. The stability constants have been determined for the 1: 1 (log K 1 = 6.2 (L mol?1)) and 2: 1 (log β = 11.9 (L2 mol?2)) complexes. The fluorescence decay kinetics of dye 1 in the presence of CB[8] is two-exponential, with the average lifetime increasing substantially at n ≥ 1. It has been shown that the system can operate in the cyclic mode as an assembler (or supramolecular catalyst) in the photodimerization reaction of dye 1 to form cyclobutane derivative 2. The stability constant of the complex 2@CB[8] (log K 3 = 5.9 (L mol?1)) and the quantum yield of cycloaddition (? ≈ 0.07 at n ≈ 0.5) have been determined. 相似文献