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641.
A strong post chemiluminescence (PCL) phenomenon was observed when ammonium was injected into the reaction mixture after the finish of CL reaction of N-bromosuccinimide (NBS) and dichlorofluorescein. Based on this, a sensitive flow injection PCL method was established for the determination of ammonium. The possible CL mechanism of the reaction was proposed based on a series of experiments. The PCL intensity responded linearly to the concentration of ammonium in the range 3.0 × 10−11-1.0 × 10−7 g mL−1 with a detection limit of 1 × 10−11 g mL−1. The relative standard deviation (R.S.D.) was 1.4% for 1.0 × 10−9 g mL−1 ammonium (n = 11). This method had been applied to the determination of ammonium in samples of mineral water, tap water and river water. 相似文献
642.
Coordination properties of axially unfixed chiral dipyridine ligands towards metal and ammonium ions
Kiu-Chor ShamChi-Sing Lee Ka-Yee ChanShek-Man Yiu Wing-Tak WongHoi-Lun Kwong 《Polyhedron》2011,30(6):1149-1156
New chiral dipyridine ligands with an axially unfixed 1,1′-biphenyl bridge were prepared via homocoupling of bromophenyl pyridines. The conformeric ratios of the free ligands in solution and their coordination properties towards metal ions were studied by NMR spectroscopy. X-Ray crystallography of the silver(I) and copper(I) complexes showed 1:1 metal to ligand complexes and S planar chirality. Interestingly, the biphenyl ligands show a 1:2 stepwise binding towards most ammonium ions tested with strong fluorescence enhancement, but a selectively 1:1 binding towards l-ornithine methyl ester hydrochloride with no fluorescence enhancement. 相似文献
643.
Carlos M.C. Infante 《Microchemical Journal》2011,98(1):97-102
This paper describes the optimization and use of a Sequential Injection Analysis (SIA) procedure for ammonium determination in waters. Response Surface Methodology (RSM) was used as a tool for optimization of a procedure based on the modified Berthelot reaction. The SIA system was designed to (i) prepare the reaction media by injecting an air-segmented zone containing the reagents in a mixing chamber, (ii) to aspirate the mixture back to the holding coil after homogenization, (iii) drive it to a thermostated reaction coil, where the flow is stopped for a previously established time, and (iv) to pump the mixture toward the detector flow cell for the spectrophotometric measurements. Using a 100 μmol L− 1 ammonium solution, the following factors were considered for optimization: reaction temperature (25 - 45 °C), reaction time (30 - 90 s), hypochlorite concentration (20 - 40 mmol L− 1), nitroprusside concentration (10 - 40 mmol L− 1) and salicylate concentration (0.1 - 0.3 mol L− 1). The proposed system fed the statistical program with absorbance data for fast construction of response surface plots. After optimization of the method, figures of merit were evaluated, as well as the ammonium concentration in some water samples. No evidence of statistical difference was observed in the results obtained by the proposed method in comparison to those obtained by a reference method based on the phenol reaction. 相似文献
644.
Sphere- and pod-like α-Fe2O3 particles have been selectively synthesized using NH3·H2O and NaOH solution to adjust the pH value of the designed synthetic system, respectively. The sphere-like α-Fe2O3 particles with diameter about 25 nm on average were encapsulated into carbon shells to fabricate a novel core-shell composite (α-Fe2O3@C) through the coating experiments. The catalytic performance of the products on the thermal decomposition of ammonium perchlorate (AP) was investigated by thermal gravimetric analyzer (TG) and differential thermal analysis (DTA). The thermal decomposition temperatures of AP in the presence of pod-like α-Fe2O3, sphere-like α-Fe2O3 and α-Fe2O3@C are reduced by 72, 81 and 109 °C, respectively, which show that α-Fe2O3@C core-shell composites have higher catalytic activity than that of α-Fe2O3. 相似文献
645.
Syed Shahed Ali 《中国化学快报》2011,22(7):793-796
Various 2-phenylimidazo[4,5-f][1,10]phenanthrolines were synthesized from potassium ferro-cyanide trihydrate(KFCT) complex catalyzed three component reaction of 1,10-phenanthroiine-5,6-dione,aromatic aldehydes and ammonium acetate at room temperature in excellent isolated yield.This is a simple and straight forward,high yielding,not involving any hazardous or expensive catalyst method. 相似文献
646.
647.
在pH9.90的Tris-HCl缓冲溶液中,阴离子染料二甲苯兰FF(XCFF)对阳离子表面活性剂溴化十六烷基三甲基铵(CTMAB)与核酸(fsDNA、ctDNA、yRNA)的共振光散射光谱有协同增强作用。考察了影响因素,在优化条件下研究了共振光散射强度与核酸浓度之间的关系,对于fsDNA、ctDNA、yRNA的线性范围分别为0.05—3.0mg/L、0.05—6.0mg/L、0.5—2.0mg/L,检出限分别为24.1、18.4、57.0μg/L。据此建立了一种测定核酸的新方法。 相似文献
648.
Thermal decomposition of a famous high oxidizer ammonium dinitramide (ADN) under high temperatures (2000 and 3000 K) was studied by using the ab initio molecular dynamics method.Two different temperature-dependent initial decomposition mechanisms were observed in the unimolecular decomposition of ADN,which were the intramolecular hydrogen transfer and N-NO2 cleavage in N (NO2)-.They were competitive at 2000 K,whereas the former one was predominant at 3000 K.As for the multimolecular decomposition of ADN,four different initial decomposition reactions that were also temperature-dependent were observed.Apart from the aforementioned mechanisms,another two new reactions were the intermolecular hydrogen transfer and direct N-H cleavage in NH4+.At the temperature of 2000 K,the N-NO2 cleavage competed with the rest three hydrogen-related decomposition reactions,while the direct N-H cleavage in NH4+ was predominant at 3000 K.After the initial decomposition,it was found that the temperature increase could facilitate the decomposition of ADN,and would not change the key decomposition events.ADN decomposed into small molecules by hydrogen-promoted simple,fast and direct chemical bonds cleavage without forming any large intermediates that may impede the decomposition.The main decomposition products at 2000 and 3000 K were the same,which were NH3,NO2,NO,N2O,N2,H2O,and HNO2. 相似文献
649.
Christopher Pohl Maria Rey Detlef Jensen Jutta Kerth 《Journal of chromatography. A》1999,850(1-2):239-245
In ion chromatography, samples of very different ammonium-to-sodium concentration ratios are difficult to quantify since these two cations have similar selectivities for stationary phases containing commonly used sulfonate or carboxylate cation-exchange functional groups. The IonPac CS15 cation-exchange column, with carboxylate and phosphonate functional groups as well as a crown ether group, was developed to address this limitation. Selectivity for the common inorganic cations on this column is different from that of conventional cation-exchange columns in that the separation between sodium and ammonium ions has been greatly increased, allowing for determinations of low levels of one in the presence of high levels of the other with an isocratic eluent. For larger than 4000:1 sodium-to-ammonium concentration ratios, an eluent step change or gradient elution is needed. For moderate ratios, combinations of this column with a carboxylate column, containing no crown ether group, can be used at room temperature with an isocratic eluent containing no organic solvent. 相似文献
650.
Thermal Decomposition and Solution Calorimetry of Ammonium Samarium Bromides The ternary pure phases on the line SmBr3—NH4Br in the thermodynamically equilibrium have been synthesized by solid state reactions and characterized by X‐ray powderdiffraction. The existence of a new phase (NH4)3SmBr6 was demonstrated beside the known phases (NH4)2SmBr5 and NH4Sm2Br7. The decomposition equilibria of the ammonium samarium bromides have been investigated by total pressure measurements and the thermodynamical data of the solid phase complexes derived from the decompostion functions. The standard enthalpies of solution in 4n HBr (aq.) of the ternary phases, SmBr3 and Sm2O3, were measured and on the basis of these values and known data the standard enthalpies of ammonium samarium bromides were derived. The phase diagram is constructed on the basis of DTA measurements. Data from total pressure measurements: ΔH((NH4)3SmBr6, f, 298) = —400, 0 ± 6, 5 kcal/mol S°((NH4)3SmBr6, f, 298) = 146, 9 ± 8 cal/K · mol ΔH((NH4)2SmBr5, f, 298) = —340, 6 ± 5, 0 kcal/mol S°((NH4)2SmBr5, f, 298) = 106, 0 ± 6 cal/K · mol Δ(NH4Sm2Br7, f, 298) = —479, 4 ± 6, 0 kcal/mol S°(NH4Sm2Br7, f, 298) = 119, 5 ± 7 cal/K · mol Data from solution calorimetry: ΔH(SmBr3, f, 298) = —204, 4 ± 1, 8 kcal/mol ΔH((NH4)3SmBr6, f, 298) = —400, 7 ± 3, 2 kcal/mol ΔH((NH4)2SmBr5, f, 298) = —339, 6 ± 2, 6 kcal/mol ΔH(NH4Sm2Br7, f, 298) = —475, 6 ± 4, 4 kcal/mol 相似文献