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31.
L-histidine substitutes cyano groups of K4Fe (CN)6 at pH 7·0 on irradiation with ultraviolet light. The reaction follows first order kinetics with reference to K4Fe(CN)6 and zero order with reference to histidine. The kinetic data shows the primary process to be aquation of Fe(CN) 6 4? while the final product is formed through a rapid dark reaction of histidine with Fe(CN)4 (H2O) 2 2? to give the product K2Fe(CN)2(histidine)2. The final product has been subjected to chemical and infrared spectral analysis.  相似文献   
32.
Summary The kinetics of the OsVIII-catalysed oxidation of glycols by alkaline hexacyanoferrate(III) ion exhibits zerothorder dependence in [Fe(CN) 6 3– ] and first-order dependence in [OsO4]. The order with respect to glycols is less than unity, whereas the rate dependence on [OH] is a combination of two rate constants; one independent of and the other first-order in [OH]. These observations are commensurate with a mechanism in which two complexes, [OsO4(H2O)G] and [OsO4(OH)G]2–, are formed either from [OsO4(H2O)(OH)] or [OsO4(OH)2]2– and the glycol GH, or by [OsO4(H2O)2] and [OsO4(H2O)(OH)] and the glycolate ion, G, which is in equilibrium with the glycol GH through the reaction between GH and OH. Hence there is an ambiguity about the true path for the formation of the two OsVIII-glycol complexes. A reversal in the reactivity order of glycols in the two rate-determining steps, despite the common attack of OH ion on the two species of OsVIII-complexes, indicates that the two complexes are structurally different because S changes from the negative (corresponding to k11) to positive (related to k2).  相似文献   
33.
Propargyloxycarbonyl chloride, 1, has been used to protect the hydroxyl and amino functionalities of amino alcohols and aminophenols in one pot using triethylamine or pyridine as a base. The increased reactivity of benzyltriethylammonium tetrathiomolybdate, 2, toward propargyl carbonates over propargyl carbamates is studied in detail and has been exploited further to develop an orthogonal protection strategy for the hydroxyl and amino functionalities. For example, 2-amino-1-butanol, 6a, was treated with 1 to get the N,O-diPoc compound 7a in 90% yield, which when treated with 1.1 equiv of 2 at room temperature removes the Poc group attached to oxygen while leaving the one attached to nitrogen intact to yield compound 8a in 85% yield. This particular observation offers a new protecting strategy where an amine and an alcohol group can be protected simultaneously in one pot, and in a later synthetic step, if the alcohol group has to be deprotected selectively, it can be achieved with 1 equiv of 2.  相似文献   
34.
The molecular box [CpCo(CN)3]4[Cp*Ru]4 (Co4Ru4) reacts readily with a variety of monocations to form M⊂Co4Ru4+ (M=K+, Cs+, Rb+). Ion competition experiments, monitored by ESI-MS, show that the molecular box binds the smaller K+ more rapidly than Cs+, but that thermodynamically Co4Ru4 prefers the larger ion. The rates of ion-insertion for K+ and Cs+ into Co4Ru4 were found to qualitatively follow second order kinetics with K+, 300 M−1 s−1 and Cs+, 36 M−1 s−1. The ratio kK/kCs qualitatively matched the ESI-MS results from ion competition experiments. The rates of ion-insertion into Co4Ru4 were found to depend on the counter anions. In particular, RbBF4 reacted with Co4Ru4 more slowly than did RbOTf. The slower rates allowed us to establish second order kinetics. 1H NMR studies reveal that the Cp signal for Co4Ru4 is very sensitive to the presence of entering ions, e.g., Rb+, whereas the corresponding Cp signal for Rb⊂Co4Ru4+ was insensitive to the presence of Rb+. The molecular structures of [Co4Ru4] · 6MeCN, [K⊂Co4Ru4]BF4 · 7MeCN, [Cs⊂Co4Ru4]BF4 · 6MeCN and [Tl⊂Co4Ru4]BF4 · 6MeCN, determined by X-ray diffraction, showed that although the compounds crystallized in the same space group I23, a correlation exists between the Ru-N/Co-C bond distances and the size of the interstitial ion.  相似文献   
35.
A novel series of complexes of the type [M(TML)X2]; where TML is a tetradentate macrocyclic ligand; M = Co(II), Ni(II), Cu(II) or Zn(II); X = Cl, CH3COO or NO 3 have been synthesized by template condensation of benzil and thiocarbohydrazide in the presence of divalent metal salts in methanolic medium. The complexes have been characterized with the help of elemental analyses, conductance measurements, molecular weight determination, magnetic measurements, electronic, NMR, infrared and far infrared spectral studies. Electronic spectra along with magnetic moments suggest the six coordinate octahedral geometry for these complexes. The low value of molar conductance indicates them to be non-electrolytes. The biological activities of metal complexes have been tested in vitro against a number of pathogenic bacteria to assess their inhibiting potential.  相似文献   
36.
JPC – Journal of Planar Chromatography – Modern TLC - A normal-phase high-performance thin-layer chromatographic (HPTLC) method has been established for quantitative estimation of...  相似文献   
37.
Ramesh A  Rama Mohan K  Seshaiah K 《Talanta》2002,57(2):243-252
Preconcentration of Cd(II), Cu(II), Mn(II), Ni(II), Pb(II) and Zn(II) in saline matrices on Amberlite XAD-4 resins coated with ammonium pyrrolidine dithiocarbamate (APDC) and piperidine dithiocarbamate (pipDTC) and subsequent determination by inductively coupled plasma atomic emission spectrometry were studied. Parameters such as effect of pH, effect of HNO(3) concentration on elution of metals from resin were studied. The results show that Amberlite XAD-4 coated with APDC was more efficient in the recovery of metal ions compared with Amberlite XAD-4 coated with pipDTC, in the concentration range of 0.1-200 mug l(-1), for 1 g of Amberlite XAD-4 coated resin. The detection limits for Cd(II), Cu(II), Mn(II), Ni(II), Pb(II), Zn(II) are 0.1, 0.4, 0.3, 0.4, 0.6, 0.5 mug l(-1), respectively, for resin coated with APDC and 0.7, 1.0, 0.8, 0.9, 1.7 and 1.2 mug l(-1) for resin coated with pipDTC. The effect of diverse ions on the determination of aforesaid metals was studied. The method was applied for the determination of trace metal ions in artificial sea water and natural water samples. The results were compared with extraction AAS method.  相似文献   
38.
A short and efficient synthesis of homopentafluorophenylalanine (6) from oxazolidine aldehyde 1 in 57% overall yield and in > 98% ee is described. The enantiomeric excess of the product was determined by 19F NMR analysis of the coupling product derived from 5 and L-Ser(O-t-Bu)-OCH3, by comparison to a dipeptide obtained from racemic 5.  相似文献   
39.
Mild, efficient and eco-friendly oxidation of 17alpha-methylandrostan-3beta-17beta-diol (1) has been studied with three different reagents viz. pentavalent iodine reagent 2-iodoxy benzoic acid (IBX) in DMSO at 65 degrees C, sodium hypochlorite and H2O2/Na2WO4 under phase transfer conditions to give 17beta-hydroxy-17alpha-methylandrostan-3-one (mestanolone 2), a drug intermediate as oxidized product. The H2O2/Na2WO4/PTC gave mestanolone in high yield and purity whereas sodium hypochlorite/PTC system yielded some chlorinated material along with the mestanolone. However, 1 with 2.5 equivalent of IBX gave 17beta-hydroxy-17alpha-methyl-Delta1-androsten-3-one (3) under the similar reaction conditions in good yield and single step reaction.  相似文献   
40.
Carotenogenesis of the lactose-negative yeast Rhodotorula rubra GED5 was studied by cocultivation with Kluyveromyces lactis MP11 in whey ultrafiltrate (WU) (35, 50, and 70 g of lactose/L). Maximum yields of cell mass (24.3 g/L) and carotenoids (10.2 mg/L of culture fluid or 0.421 μ g/g of dry cells) were obtained by growing the microbial association in WU (50 g of lactose/L) in a fermentor with an airflow rate of 0.8 L/(L·min), agitation of 220 rpm, and temperature of 30°C. The identified carotenoid pigments—β-carotene, torulene, and torularhodin—reached maximum concentrations (133, 26.9, and 222.3 μg/g of dry cells, respectively) on d 5 for torulene and d 6 for β-carotene and torularhodin.  相似文献   
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