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31.
The reagent, bismuthiol l, has been successfully utilized for the spectrophotometric determination of palladium. The colour reaction is instantaneous and the system is stable for at least 24 hours in the pH range 6 to 10 but shows no sharp peak of maximum absorption. The system obeys Beer's law at a palladium concentration of 0.8 μg to 8.0 μg per ml at any wavelength between 400 mμ and and 410 mμ giving a sensitivity of 0.08 μg of palladium per cm2 (practical); 0.01 μg of palladium per cm2 (sandell). Ethyl alcohol stabilizes the system against any deviation due to appearance of turbidity. A large excess of the reagent and almost all thc cations and anions, except platinum, gold, copper, chromium, iron, mercury, silver, thallium, uranium, vanadate and cyanide, do not interfere. By applying job's method of continuous variation it was found that the complex contains thc reactants in 1 : 1 ratio and that the average value of the dissociation constant of the complex is 3.2 10-5 at 25°. 相似文献
32.
Nucleophilic substitution of Pd(RaaiR′)Cl2 [(RaaiR′ = 1-alkyl-2-(arylazo)imidazole, p-R-C6H4-N=N-C3H2NN-1-R′; where R = H(a)/ Me(b)/ Cl(c) and R′ = Et(1)/Bz(2)] with 2-Mercaptopyridine (2-SH-Py) in acetonitrile (MeCN) at 298 K, to form [Pd2(2-S-Py)4], has been studied spectrophotometrically under pseudo-first-order conditions and the analyses support the nucleophilic association
path. The reaction follows the rate law, Rate = {k
0 + k [2-SH-Py]
0
2
}[Pd(RaaiR′)Cl2]: first order in Pd(RaaiR′)Cl2 and second order in 2-SH-Py. The rate of the reaction follows the order: Pd(RaaiEt)Cl2
(1) < Pd(RaaiBz)Cl2
(2) and Pd(MeaaiR′)Cl2 (b) < Pd(HaaiR′)Cl2 (a) < Pd(ClaaiR′)Cl2 (c). External addition of Cl− (LiCl) and HCl suppresses the rate (Rate ∝ 1/[Cl−]0 & ∝1/[HCl]0). The reactions have been studied at different temperatures (293–308 K) and activation parameters (Δ‡ H° and Δ ‡ S°) of the reactions were calculated from the Eyring plot and support the proposed mechanism. 相似文献
33.
Summary The reagent 2-mercapto-benzothiazole quantitatively precipitates palladium at a PH 5.6 to 10.2. The red coloured compound, Pd(C7H4NS2)2, is diamagnetic and is stable up to a temperature of 388 C. Palladium is separated from alkalis, alkaline earths, Mg, Fe3+, Cr, Th, Zr, Ti, UO2
2+, Be, rare earths, Ce3+, Ce4+, Zn, Mn, Co, Ni, Pb, Bi, Sb3+, As3+, Sn4+, Tl+, Cu2+, Cd, Ir4+, Rh3+, Ru3+, Os4+, CrO4
2–, MoO4
2–, WO4
2–, VO3
–, PO4
3– and AsO4
3– at apH 6–8 in presence of EDTA and tartaric or citric acid. Besides Pb, Ag and Hg2+ are kept in solution with potassium iodide and Au in a limited quantity forms a soluble complex with thiosulphate. The palladium complex is either weighed after drying and determined gravimetrically or dissolved in an excess of cyanide and determined volumetrically by back titrating the latter with silver nitrate. 相似文献
34.
35.
Thermal [3,3] sigmatropic rearrangement of 6-cyclohex-2-enyloxy-1-methylquinolin-2(1H)-one (3) afforded 5-cyclohex-2-enyl-6-hydroxy-l-methyl-quinolin-2(1H)-one (4) in 86% yield. Compound 4 on treatment with pyridine hydrotribromide in CH2Cl2 gave exclusively non-bridged product 6 (85%) whereas compound 4 by a different route viz., acetylation followed by bromine addition and cyclization gave the bicyclic product 7 (80%). Compound 4 also furnished a bicyclic product 11 (80%) on treatment with cone. H2SO4. 相似文献
36.
6-Alkylpyrano [3,2-c] quinolin-5(2H)-ones(11a-e) were obtained in excellent yields by simply refluxing propynyl and butymyl ethers (6) of 4-hydroxy-1-alkylquinolin-2H-ones (2) in chlorobenzene for 10h, 5-Prop-2-ynyloxy-2H-pyrano [3,2-c] quinoline (12) was also obtained from the thermal rearrangement of 2,4-bis prop-2-ynyloxyquinoline (4). 相似文献
37.
[3,3] Sigmatropic rearrangement of unsymmetrically substituted 1,4-but-2-ynes exhibit preference for rearrangement on the aryloxy prop-2-ynyl moiety to N-methyl-N-pyrimidinyl amino prop-2-ynyl moiety in case of 5-substituted uracils (la-f). 相似文献
38.
3′O-silylated derivatives of 5′-O-DMT-2′deoxynucleoside (2) were synthesized in high yield by reaction of 5′-O-DMT-2′-deoxynucleosides (1) with tert-butyl dimethylsilylchloride using sodium hydride, benzyltriethylammonlum chloride [TEBA] and a catalytic amount of dibenzo-[18]-crown-6 [DB-18-C-6] or 15-crown-5 [15-C-51 under mild reaction conditions. 相似文献
39.
The tin hydride–mediated cyclizations of a number of ethers, sulfides, and sulfones under mild, neutral conditions have been investigated. While the 2-bromobenzyloxy ethers were prepared in 62–65% yields by the alkylation of 4-hydroxy-1-phenyl-1,8-naphthyridin-2(1H)-one with 2-bromobenzyl bromides in refluxing acetone in the presence of anhydrous potassium carbonate, the sulfides were derived from 4-mercapto-1-phenyl-1,8-naphthyridin-2(1H)-one and 2-bromobenzyl bromides in 82–84% yields by a phase-transfer catalysis (PTC) reaction. The corresponding sulfones were prepared by treatment of the sulfides with m-CPBA in refluxing dichloromethane. The ethers, sulfides, and the sulfones were treated with n Bu3SnH-AIBN to give regioselectively 1,8-naphthyridinone-annulated oxygen and sulfur heterocycles in 70–78% yields. 相似文献
40.
A number of ortho -cyclohexenyl phenols 2(a–i) have been cyclised by treatment with one equivalent of m-chloroper-oxybenzoic acid in refluxing benzene for 4 h to furnish linearly fused 1-hydroxy-1,2,3,4,4a,9a-hexahydrodibenzofurans 3(a–i) (70–80%) and bicyclic 3-hydroxy-1,3-ethanochromans 4(a–f) (10–20%). Products 3(a–i) were oxidised with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (excess) in refluxing dry xylene for 6 h to give 2,3-dihydrodibenzofuran-1 (2H)-ones 6(a–i) (85–95%). 相似文献