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991.
[reaction: see text] A short-step synthesis of versatile chiral building blocks for triazole antifungal agents such as ZD0870 and Sch45450 was developed via catalytic enantioselective cyanosilylation of electron-deficient ketones as the key step. High enantioselectivity was produced using a catalyst prepared from Gd(HMDS)(3) and ligand 5 in a 2:3 ratio. This new catalyst preparation method was superior to the previous method using Gd(O(i)Pr)(3) as a metal source. A rationale for the difference is proposed on the basis of structural studies of the catalyst complexes using ESI-MS. 相似文献
992.
Liquid crystal properties of new ionic liquid crystal compounds having a 1,3-dioxane ring 总被引:1,自引:0,他引:1
Yuichiro Haramoto Tomomi Miyashita Masato Nanasawa Yoshio Aoki Hiroyuki Nohira 《Liquid crystals》2002,29(1):87-90
New pyridinium type chiral ionic liquid crystal materials having a 1,3-dioxane ring in the central core, (+)- N -2-methylbutyl-4-(5-alkyl-1,3-dioxan-2-yl)pyridinium bromides ( 6 ), were synthesized. Mixture A was made by adding 5.9 wt % of compound 6-3 to the ferroelectric liquid crystal mixture Merck 4655-100; its phase transitions and some liquid crystal properties were measured. In spite of a large decrease of P s for mixture A, its response time A was the same as that of Merck 4655-100. The dielectric constants perpendicular to the molecular axis for the smectic C* and smectic A phases were measured for the mixture and Merck 4655-100: in the smectic C phase, these dielectric constants were almost the same (4.5~5.5), but in the smectic A phase, the perpendicular dielectric constant of the mixture was 47.0 and that of Merck 4655-100 was 4.5. 相似文献
993.
Cellulose β-ketoesters having long alkyl or alkenyl chains were prepared by homogeneous reactions with alkyl or alkenyl ketene dimmers (OKD or AKD), and were characterized by X-ray diffractometory, differential scanning calorimetry, optical microscopy with cross polarizers and others. The Cellulose/OKD and AKD β-ketoesters with degrees of substitution (DS) of more than 1.5 were gummy solid at room temperature and had birefringence due to liquid crystalline structures in wide temperature range. The liquid crystalline/isotropic phase transition points were 150–175 °C, depending on the DS and substituents introduced into cellulose hydroxyls. X-ray diffraction patterns indicated that cellulose backbones had disordered structures at room temperature, while alkyl chains in the substituents formed ordered or crystalline domains in the cellulose β-ketoesters. Films of the cellulose/AKD β-ketoesters prepared by casting their chloroform solutions on glass plates had highly hydrophobic nature, and contact angles of water droplet on the films were more than 90°. The water-contact angles on the films decreased to some extent just after heating of the films at 105 °C, whereas they were gradually recovered to the initial values by conditioning at ambient temperature. 相似文献
994.
The reaction of (η5-C5H4Me)4Fe4(HCCH)2 (1) with 1 equiv. of N-bromosuccinimide (NBS) gives the one-electron oxidized form in 83% yield. Further treatment of [1]+ with NBS results in the stepwise bromination of four acetylenic protons to give [(η5-C5H4Me)4Fe4(HCCH)(HCCBr)]+ ([2]+), [(η5-C5H4Me)4Fe4(HCCBr)2]+ ([3a]+), [(η5-C5H4Me)4Fe4(HCCBr)(BrCCBr)]+ ([4]+), and [(η5-C5H4Me)4Fe4(BrCCBr)2]+ ([5]+) in moderate yields, with the isomer of [3a]+, [(η5-C5H4Me)4Fe4(HCCH)(BrCCBr)]+ ([3b]+), formed as a minor product. These compounds are characterized by analytical and spectroscopic techniques, and the molecular structures of [2](PF6), [4](TFPB), and [5](TFPB) are established by X-ray diffraction analysis [TFPB = tetrakis{bis(3,5-trifluoromethyl)phenyl}borate]. The compounds are confirmed to retain the butterfly core of four iron atoms as in [1](TFPB). The bromoacetylene part in [2]+ exhibits high reactivity toward various nucleophiles: Cluster[2]+ is moisture-sensitive and is converted to a mixture of [(η5-C5H4Me)4Fe4(HCCH)(μ3-CH)(μ3-CO)]+ ([6]+) and [1]+. Reactions of [2]+ with ZnR2 (R = Me, Et) give [(η5-C5H4Me)4Fe4(HCCH)(HCC-R)]+ in good yields (R = Me ([9]+, 88%), Et ([10]+, 91%)). Accordingly, treatment of [2]+ with HC CMgBr and LiSpTol leads to the introduction of the ethynyl and thiolate groups to give [(η5-C5H4Me)4Fe4(HCCH)(HCC-CCH)]+ ([11]+, 95%) and [(η5-C5H4Me)4Fe4(HCCH)(HCC-SpTol)]+ ([12]+, 78%), respectively. Substitution of the bromo group in [2]+ with pyridine affords [(η5-C5H4Me)4Fe4(HCCH)(HCC-Py)]2+ ([13]2+) in 90% yield. The reaction with 4,4′-bipyridyl (bpy) requires the severer conditions (70 °C, 2 days), probably due to the relative low basicity of bpy, giving [(η5-C5H4Me)4Fe4(HCCH)(HCC-bpy)]2+ ([14]2+) in 54% yield. The substitution reaction with 4,4′-bipyridyl is strongly accelerated by treatment with silver salt to give [14]2+ in 90% yield. The products derived from [2]+ and nucleophiles are unequivocally determined by elemental, spectroscopic, and X-ray diffraction analyses. 相似文献
995.
SEC-MALS analysis of cellouronic acid prepared from regenerated cellulose by TEMPO-mediated oxidation 总被引:1,自引:0,他引:1
Izumi Shibata Masahiro Yanagisawa Tsuguyuki Saito Akira Isogai 《Cellulose (London, England)》2006,13(1):73-80
The 4-amino-2,2,6,6-tetramethylpiperidine-1-oxy radical (4-amino-TEMPO)-mediated oxidation was applied to regenerated cellulose,
and the obtained cellouronic acid was analyzed by size-exclusion chromatography attached with a multi-angle laser light scattering
detector (SEC-MALS). Although the cellouronic acid filtered with the usual 0.1 μm membrane gave a bimodal SEC-elution pattern,
the high-molecular-mass fraction was removed by micro filtration of the cellouronic acid solution with a 0.02 μm membrane.
It is likely, therefore, that some colloidal particles formed from regenerated cellulose by the TEMPO-mediated oxidation are
present as incompletely oxidized residues in the cellouronic acid sample and behave as the high-molecular-mass fraction in
the SEC elution pattern. Then, the SEC-MALS analysis was applied to the 0.02 μm membrane-filtered cellouronic acid, and the
accurate DPw value of 36 was obtained for cellouronic acid. This DPw value was far lower than that of carboxymethyl cellulose,
hydroxypropyl cellulose or alginic acid, resulting from significant depolymerization of cellulose chains during the TEMPO-mediated
oxidation. Because the value of DPw 36 for cellouronic acid is close to the leveling-off DP (about 40) of regenerated celluloses
obtained by the dilute and heterogeneous acid hydrolysis, the DPw value of cellouronic acid must reflect the solid-state structure
of the original regenerated cellulose used in the TEMPO-mediated oxidation. 相似文献
996.
Various silica nanotubes and nanocapsules have been prepared successfully, possessing unique silica walls of selective H2 permeation and encapsulate group 8-10 metal particles inside and exhibit a marked stabilization effect of H2 and CO over the metals in the network of silica wall and inside nanoscale cavities. 相似文献
997.
Photocatalytic property and electronic structure of triple-layered perovskite tantalates, MCa2Ta3O10 (M = Cs, Na, H, and C6H13NH3) 总被引:2,自引:0,他引:2
Machida M Mitsuyama T Ikeue K Matsushima S Arai M 《The journal of physical chemistry. B》2005,109(16):7801-7806
The Dion-Jacobson series of triple-layered perovskite tantalates (MCa2Ta3O10, M = Cs, Na, H, and C6H13NH3) were synthesized to evaluate their photocatalytic activity for overall water splitting to evolve H2/O2 under UV irradiation. The photocatalytic activity was susceptible to the hydration of interlayer space. The hydrous Na phase exhibited much higher activity (H2: 308 micromol.h(-1)) compared to the anhydrous Cs phase (24 micromol.h(-1)) and the hydrous H phase (22 micromol.h(-1)) in the presence of 0.5 wt % Ni impregnated. H2O/D2O isotopic experiment suggested that the hydrated interlayer plays as an active site for water splitting, where the high mobility of water molecule in the interlayer should correlate with the total photocatalytic activity. The FLAPW electronic structure calculation demonstrated that the terminating oxygen site, O4, which faces to the interlayer space, contributes largely to the top of the valence band. Judging from comparison with the double-layered tantalates, MLaTa2O7, in our previous study, the contribution of terminating oxygen site to the band structure is supposed to depend on the number of perovskite layers. 相似文献
998.
The acyclic asymmetric induction is described which involves heteroconjugate addition of MeLi to α-hydroxy hetero-olefins and concomitant intramolecular silicon-migration to produce α,α-sulfonyl-dianion of the adduct being of utility for the second CC bond formation in one pot. It also contains the first chemical proof of the regiochemical assignment to the hetero-olefins. 相似文献
999.
Hiroyoshi Kamogawa Yoko Takayanagi Masato Nanasawa 《Journal of polymer science. Part A, Polymer chemistry》1981,19(11):2947-2953
2,4-Dihydroxy-4′-vinylbenzophenone (I) and its 4-alkyl ethers (II), Me, Et, n-Bu, n-Oct, and n-dodecyl, were prepared in three steps by Hoesch synthesis, starting with p-(2-bromoethyl) benzonitrile and resorcinol and its monoalkyl ethers. I and its precursor 2,4-dihydroxy-4′-(2-bromoethyl) benzophenone were also converted into their 4-alkyl ethers with alkyl halides in dimethylformamide (DMF) in the presence of sodium hydrogen carbonate. Copolymerizations of I and II with styrene took place smoothly with satisfactory conversions to yield copolymers with ε-values around 104 L/mol cm?1 per benzophenone unit over the ultraviolet (UV) range of 235–340nm. 相似文献
1000.
Jun Segawa Masahiko Kitano Kenji Kazuno Masami Tsuda Ichiro Shirahase Masakuni Ozaki Masato Matsuda Masahiro Kise 《Journal of heterocyclic chemistry》1992,29(5):1117-1123
A series of 8-substituted-7-fluoro-5-oxo-5H-thiazolo[3,2-a]quinoline-4-carboxylic acids was prepared and evaluated for antibacterial activity. These compounds were synthesized from ethyl 2-mercaptoquinoline-3-carboxylates 17 which were obtained from anilines 11 by a route involving an intramolecular cyclization reaction. 相似文献