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排序方式: 共有141条查询结果,搜索用时 390 毫秒
31.
32.
33.
P. C. Mandal D. K. Bardhan S. N. Bhattacharyya 《Journal of Radioanalytical and Nuclear Chemistry》1995,191(2):349-359
Reactions of carbonate radical (CO3
–), generated by photolysis or by radiolysis of a carbonate solution with nickel(II)-iminodiacetate (Ni(II)IDA) were studied at pH 10.5 and ionic strength (I)==0.2 mol·dm–3. The stable product arising from the ligand degradation in the complex is mainly glyxalic acid. Time-resolved spectroscopy and transient kinetics were studied using flash photolysis. From the kinetic data it was suggested that the carbonate radical initially reacts with Ni(III)IDA with a rate constant (2.4±0.4)·106 dm3·mol–1·s–1 to form a Ni(II)IDA species which, however, undergoes a first-order transformation (k=2.7·102·s–1) to give a radical intermediate of the type Ni(II)RNHCHCO
2
–
) which rapidly forms an adduct containing a Ni–C bond. This adduct decays very slowly to give rise to glyoxalic acid. From a consideration of equilibrium between Ni(II)IDA and Ni(III)IDA, the one electron reduction potential for the Ni(III)IDA/Ni(II)IDA couple was determined to be 1.467 V. 相似文献
34.
P. C. Mandal D. K. Bardhan S. N. Bhattacharyya 《Journal of Radioanalytical and Nuclear Chemistry》1992,166(2):87-96
Reactions of carbonate (CO
3
–·
) and bicarbonate (HCO
3
·
) radicals generated by photolysis of a carbonate or bicarbonate solution at pH 11.2 and 8.5, respectively, with Co(II) complexes of iminodiacetic acid (IDA) and ethylenediaminetetraacetic acid (EDTA) have been studied. The rate constants for the reactions were in the order of 106–107 dm3mol–1s–1. From the time-resolved spectroscopy of the products formed after reaction of CO
3·
–·
or HCO
3
·
, it is observed that CO
3
–·
or HCO
3
·
oxidize the metal center to its higher oxidation state. 相似文献
35.
Krishna Bardhan Sailes Mukhopadhyay Satya. R. Chatterjee 《Journal of polymer science. Part A, Polymer chemistry》1977,15(1):141-148
Acrylamide was grafted onto methyl cellulose backbone by using potassium persulfate as initiator in aqueous solution, and variables affecting the copolymerization were studied. It was found that efficiency of grafting was maximum at an initiator concentration of 3.7 × 10?4 mole/l. Grafting was found to increase steadily with increase in monomer/polymer ratio and with temperature up to 40°C. 相似文献
36.
Sujata Roy 《Tetrahedron letters》2005,46(8):1325-1328
The reaction of 2-iodo- and 2-bromoindoles with silver nitrite in aqueous acetone affords the corresponding 2-nitroindoles in modest to good yields. 相似文献
37.
It was previously reported that methyl oleanonate (5) and lanost-8-en-3-one (10) give predominantly [3,2-c]isoxazoles. On the contrary, we have confirmed that both compounds 5 and 10 do not give [3,2-c]isoxazoles but rather afford regioselectively [2,3-d]isoxazoles in good yields. Consequently, a new lanostane triterpenoid with a cyano-enone functionality in ring A was synthesized in two steps from the corresponding [2,3-d]isoxazole, which is interesting from the perspective of biological activity because lanosterol is the biogenetic precursor of steroids. 相似文献
38.
39.
Phase pure, stable nanocrystalline brushite particles with average diameter in the range of 23–87 nm were obtained by the
reverse microemulsion technique employing a mixture of surfactants (Aliquat 336 & Tween 80) as template directing agents,
and calcium nitrate tetrahydrate and biammonium hydrogen phosphate as precursors. Particle sizes and morphologies were tuned
by adjusting the reaction parameters, precursor concentration and temperature. FTIR, TEM, and XRD were used to characterize
morphological changes of as synthesized nanoparticles. FTIR and XRD analyses confirmed the formation of brushite nanoparticles.
Variations in the reaction temperature resulted in changes in the particle morphology and distribution. At high temperatures
(60°C), the sample exhibited high monodispersity and spherical morphology with the average grain size of 42 nm. At low temperatures
(6°C), nanoflakes were formed. The results suggest that a reverse microemulsion system provides facile media for control of
the phase and morphology of nanoscale calcium phosphate biominerals. A mechanism providing an insight into the formation of
brushite particles has also been proposed. 相似文献
40.
Agrawal SK Sanabria-DeLong N Bhatia SK Tew GN Bhatia SR 《Langmuir : the ACS journal of surfaces and colloids》2010,26(22):17330-17338
We report the energetics of association in polymeric gels with two types of junction points: crystalline hydrophobic junctions and polymer-nanoparticle junctions. Time-temperature superposition (TTS) of small-amplitude oscillatory rheological measurements was used to probe crystalline poly(L-lactide) (PLLA)-based gels with and without added laponite nanoparticles. For associative polymer gels, the activation energy derived from the TTS shift factors is generally accepted as the associative strength or energy needed to break a junction point. Our systems were found to obey TTS over a wide temperature range of 15-70 °C. For systems with no added nanoparticles, two distinct behaviors were seen, with a transition occurring at a temperature close to the glass transition temperature of PLLA, T(g). Above T(g), the activation energy was similar to the PLLA crystallization enthalpy, suggesting that the activation energy is related to the energy needed to pull a PLLA chain out of the crystalline domain. Below T(g), the activation energy is expected to be the energy required to increase mobility of the polymer chains and soften the glassy regions of the PLLA core. Similar behavior was seen in the nanocomposite gels with added laponite; however, the added clay appears to reduce the average value of the activation enthalpy. This confirms our SAXS results and suggests that laponite particles are participating in the network structure. 相似文献