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排序方式: 共有195条查询结果,搜索用时 423 毫秒
51.
52.
Tetsuji Kametani Yasuo Fujimoto Masakatsu Mizushima 《Journal of heterocyclic chemistry》1975,12(6):1271-1273
Reductive cyclization of 1,2,3,4-tetrahydro-6,7-dimethoxy-1-(4,5-dimethoxy-2-nitrophen-ethyl)isoquinoline (V) with triethyl phosphite gave 5,6-dihydro-2,3,9,10-tetramethoxybenzimidazo[2,1-a]isoquinoline (IX), whose structure was identified by the spectroscopic analyses by an alternative synthesis. 相似文献
53.
Takanori Mizushima Kazumi Matsumoto Hironobu Ohkita Noriyoshi Kakuta 《Plasma Chemistry and Plasma Processing》2007,27(1):1-11
Plasma synthesis of ammonia was studied at atmospheric pressure using a dielectric-barrier-discharge-plasma reactor equipped
with a metal-loaded membrane-like alumina tube as a catalyst between the electrodes. Introducing the pure alumina into N2–H2 plasma resulted in an increase in the ammonia yield and the further improvement was achieved by loading the alumina with
Ru, Pt, Ni, and Fe. These results clearly demonstrate the catalytic effects of the alumina and the metals in the plasma reaction.
Temperature-programmed desorption and isotope exchange reaction of nitrogen revealed that plasma-excited N2 molecules were subjected to dissociative adsorptions mainly on the alumina to form atomic N(a) (The suffix “(a)” denotes
adsorbed species) species, which were converted into ammonia by H2 plasma. A role of the metals is considered to be acceleration of ammonia formation by the reaction of the alumina-adsorbed
N(a) atoms with plasma-activated hydrogen species. 相似文献
54.
Takashi Katsu Tomonori Imamura Keiko Komagoe Kazufumi Masuda Tohru Mizushima 《Analytical sciences》2007,23(5):517-522
The changes induced by biologically active substances in the permeability to K+ and calcein of liposomes composed of egg phosphatidylcholine and cholesterol were measured simultaneously in order to rapidly screen the sizes of pores formed in a membrane, using different sized markers. The substances examined in the present study were classified into three types based on differences in the rates at which K+ and calcein were released. The first type released only K+, and included gramicidin A. The second type predominantly released K+, preceding the release of calcein, and included amphotericin B and nystatin. The third type, including antimicrobial peptides, such as gramicidin S, alamethicin, and melittin, and several membrane-active drugs, like celecoxib (non-steroidal anti-inflammatory drug), 1-dodecylazacycloheptan-2-one (named azone; skin permeation enhancer), and chlorpromazine (tranquilizer), caused the release of K+ and calcein simultaneously. Thus, the sizes of pores formed in a liposomal membrane increased in the following order: types one, two, and three. We determined the size more precisely by conducting an osmotic protection experiment, measuring the release of calcein in the presence of osmotic protectants of different sizes. The radii of pores formed by the second type, amphotericin B and nystatin, were 0.36 - 0.46 nm, while the radii of pores formed by the third type were much larger, 0.63 - 0.67 nm or more. The permeability changes induced by substances of the third type are discussed in connection with a transient pore formed in a lipid packing mismatch taking place during the phase transition of dipalmitoylphosphatidylcholine liposomes. 相似文献
55.
Yasunori Ohba Chika Watanabe Shigeaki Nakazawa Seigo Yamauchi 《Applied magnetic resonance》2010,37(1-4):781-794
We reported determination of the loaded quality factor (Q) of highly overcoupled (dielectric, loop-gap, and cavity) resonators used in time-domain electron paramagnetic resonance. We introduced a microwave absorber into resonators and achieved critical-coupling. Due to the deep “Q-dip” of critical-coupling, we can easily determine the loaded Q as low as 10. The loaded Q of resonators with and without the microwave absorber was examined under various overcoupling conditions. We found that the radiation Q (Q r) can be calculated from the loaded Q of the resonator that contains the microwave absorber. We proposed a simple model that represents the loaded Q of the overcoupled resonator in terms of two parameters, Q 0 and Q r. Q 0 is the effective unloaded Q of the resonator determined for the critically coupled resonator without the microwave absorber and is independent of a degree of coupling. The model can be applied to overcoupling in which the coupling parameter (Q 0/Q r) is in the range of 1 to ca. 20. 相似文献
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Thermal decomposition of ammonium uranates precipitated from uranyl nitrate solutions on addition of aqueous ammonium hydroxide under various conditions has been examined by thermogravimetry (TG), differential thermal analysis (DTA), infrared spectroscopy and X-ray diffraction study. The TG curves of all precipitates show the weight-loss corresponding to the calculated value as UO3·NH3·H2O. The DTA curves of the precipitates give the endotherms at about 130, 210 and 590 °C and the exotherms at 340–420 °C. As a result, it is found that ammonium uranates thermally decompose to amorphous UO3 at about 400 °C, and transform to U3O8 via β-UO3. 相似文献
59.
Morita Y Kawai J Fukui K Nakazawa S Sato K Shiomi D Takui T Nakasuji K 《Organic letters》2003,5(18):3289-3291
[structure: see text] Topological symmetry-based extensions of a pi-conjugation network in an odd alternant phenalenyl radical have enabled us to control the spin density distribution systematically. ESR/ENDOR and NICS studies on the topological isomers of oxophenalenoxyl have revealed that the unpaired electron tends to localize in the antiaromatic ring systems. 相似文献
60.
A polymer chain conformation change near the critical point of liquid-liquid phase separation was investigated. Poly(N-isopropylacrylamide) labeled with a small amount of carbazolyl group for a fluorophore (P(NIPA-Cz)) was prepared. A ternary system of P(NIPA-Cz)+cyclohexane+methanol was investigated by the fluorescence spectroscopic technique. A mixed solvent of cyclohexane+methanol (CH/MeOH) shows phase separation at the upper critical solution temperature. Light scattering intensity, fluorescence emission intensity and fluorescence anisotropy ratio, as a function of temperature, were measured with quasi statically approaching to the critical demixing point. The fluorescence intensity of the carbazolyl groups attached to the polymer chain decreases with approaching to the critical temperature. This result suggests that the radius of gyration of the polymer decreases upon approaching to the critical demixing point of the solvent. We discuss the collapse and aggregation processes of the polymer based on the fluorescence quenching method. The rotational diffusion coefficient of carbazolyl groups attached to the polymer chain was estimated by the fluorescence depolarization technique. The rotational motion of carbazolyl groups is slowed down upon approaching the critical point. 相似文献