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101.
《Analytical letters》2012,45(6):1183-1191
Abstract

A study of the enhancement effect on the fluorescence intensity of the Eu3+–-thenoyltrifluoroacetone (TTA)–-cetyltri–-methylammonium bromide (CTMAB) and the Dy3+ pyrocatechol–-3,5-disulphonic acid (Tiron) systems by Y3+has been carried out. In the presence of yttrium the fluorescence intensity of the systems was enhanced by a factor of about 100 and 15, respectively. The fluorescence intensity was a linear function of the concentration of europium or dysprosium in the range 1.0 × 10?10–-1.0 × 10?8mol dm?3 and 8.0 × 10?8–-9.0 × 10?6mol dm?3, respectively. The detection limit was 1.0 × 10?11mol dm?3 and 1.0 × 10?10mol dm?3, respectively. The standard addition method was used for the determination of europium or dysprosium in rare earth oxides and gave satisfactory results. The mechanism of enhanced fluorescence was proposed.  相似文献   
102.
High-resolution (0.001 cm−1) coherent anti-Stokes Raman scattering (CARS) was used to observe the Q-branch structure of the IR-inactive ν1 symmetric stretching mode of 32S16O3 and its various 18O isotopomers. The ν1 spectrum of 32S16O3 reveals two intense Q-branches in the region 1065–1067 cm−1, with surprisingly complex vibrational–rotational structure not resolved in earlier studies. Efforts to simulate this with a simple Fermi-resonance model involving ν1 and 2ν4 states do not reproduce the spectral detail, nor do they yield reasonable spectroscopic parameters. A more subtle combination of Fermi resonance and indirect Coriolis interactions with nearby states, 2ν4(1=0, ±2), ν24(1=±1), 2ν2(1=0), is suspected and a determination of the location of these coupled states by high-resolution infrared measurements is under way. At medium resolution (0.125 cm−1), the infrared spectra reveal Q-branch features from which approximate band origins are estimated for the ν2, ν3, and ν4 fundamental modes of 32S18O3, 32S18O216O, and 32S18O16O2. These and literature data for 32S16O3 are used to calculate force constants for SO3 and a comparison is made with similar values for SO2 and SO. The frequencies and force constants are in excellent agreement with those obtained by Martin in a recent ab initio calculation.  相似文献   
103.
The thermal behaviour of CrO3 on heating up to 600°C in dynamic atmospheres of air, N2 and H2 was examined by thermogravimetry (TG), differential thermal analysis (DTA), IR spectroscopy and diffuse reflectance spectroscopy (DRS). The results revealed three major thermal events, depending to different extents on the surrounding atmosphere: (i) melting of CrO3 near 215°C (independent of the atmosphere), (ii) decomposition into Cr2(CrO4)3 at 340–360°C (insignificantly dependent), and (iii) decomposition of the chromate into Cr2O3 at 415–490°C (significantly dependent). The decomposition CrO3 → Cr2(CrO4)3 is largely thermal and involves exothermic deoxygenation and polymerization reactions, whereas the decomposition Cr2(CrO4)3 → Cr2O3 involves endothermic reductive deoxygenation reactions in air (or N2) which are greatly accelerated and rendered exothermic in the presence of H2. TG measurements as a function of heating rate (2–50°C min−1) demonstrated the acceleratory role of H2, which extended to the formation of Cr(II) species. This could sustain a mechanism whereby H2 molecules are considered to chemisorb dissociatively, and then spillover to induce the reduction. DTA measurements as a function of the heating rate (2–50°C min−1) helped in the derivation of non-isothermal kinetic parameters strongly supportive of the mechanism envisaged. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
104.
High-quality and crack-free Y2O3 single crystals containing low concentrations of Tm3+, Tb3+ and Yb3+ were obtained. The crystals were grown in the form of monocrystalline fibers by using a floating zone method with laser heating (laser-heated pedestal growth).  相似文献   
105.
采用光催化法对造纸废水的处理进行了研究.探讨了光催化反应机理,比较了光催化剂的活性顺序,讨论了复相光催化剂的组成、用量、试液pH值、光照时间与COD、色度去除率的关系.实验结果表明:采用WO3/α-Fe2O3/W为复相光催化剂,其组成为WO3:α-Fe2O3:W=75:24:1,当其用量为0.500g、pH=6.5、光照22h,造纸废水的COD和色度去除率分别达到68.3%和71.2%.  相似文献   
106.
Xenon trioxide (XeO3) forms adducts with triphenylphosphine oxide, dimethylsulfoxide, pyridine-N-oxide, and acetone by coordination of the ligand oxygen atoms to the XeVI atom of XeO3. The crystalline adducts were characterized by low-temperature, single-crystal X-ray diffraction, and Raman spectroscopy. Unlike solid XeO3, which detonates when mechanically or thermally shocked, solid (C5H5NO)3(XeO3)2, [(C6H5)3PO]2XeO3, and [(CH3)2SO]3(XeO3)2 are insensitive to mechanical shock. The [(CH3)2SO]3(XeO3)2 adduct slowly decomposes over several days to (CH3)2SO2, Xe, and O2. All three complexes undergo rapid deflagration when ignited by a flame. Both [(C6H5)3PO]2XeO3 and (C5H5NO)3(XeO3)2 are room-temperature stable and the [(CH3)2CO]3XeO3 complex dissociates at room temperature to form a stable solution of XeO3 in acetone. The xenon coordination sphere of [(C6H5)3PO]2XeO3, a distorted square-pyramid, provides the first example of a five-coordinate XeO3 complex with only two Xe- - -O adduct bonds. The xenon coordination spheres of the remaining adducts are distorted octahedra, comprised of three Xe- - -O secondary bonds that are approximately trans to the primary Xe−O bonds of XeO3. Quantum-chemical calculations were used to assess the nature of the Xe- - -O adduct bonds, which are described as predominantly electrostatic bonds between the nucleophilic oxygen atoms of the bases and the σ-holes of the electrophilic xenon atoms.  相似文献   
107.
《中国化学快报》2020,31(10):2849-2853
A magnetic mesoporous expanded perlite-based (EPd-APTES@Fe3O4) composite was designed and synthesized as a novel adsorbent for enrichment of rare earth ions in aqueous solution. Effect of various factors including the pH of solution, contact time and adsorbent dosage on the adsorption behaviors of yttrium(III) by the EPd-APTES@Fe3O4 nano-material composites from aqueous solution was investigated. The maximum adsorption capacity of the as-prepared materials for yttrium(III) ions was 383.2 mg/g. Among the various isotherm models, the Freundlich isotherm model could well described for the adsorption of the rare earth ions at pH 5.5 and 298.15 K. The kinetic analysis indicated that the adsorption process followed the pseudo-second order kinetics model, and the rate-determining step might be chemical adsorption. Thermodynamic parameters declared that the adsorption process was endothermic. In addition, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and the quantum chemical calculation indicated that the yttrium(III) ions were captured on the EPd-APTES@Fe3O4 surface mainly by coordination with functional group of -NH2. More importantly, the adsorption-desorption studies indicated that the EPd-APTES@Fe3O4 nano-material composites had a high stability and good recyclability.  相似文献   
108.
本文采用中阶梯光栅光谱仪,直流等离子体光谱法测定高纯(99.99%)氯化镧、氧化钇中稀土杂质元素,由于仪器具有很高的色散率,因而方法具有灵敏度高、干扰少的特点。  相似文献   
109.
We report the results of a wide experimental study of the irreversible modulated microwave absorption as a function of temperature, applied magnetic field and modulation amplitude in the YBa2Cu3Ox single crystals. To analyze the experimental data the model of the microwave power dissipation by the flux lines has been developed taking into account thermal fluctuations, the distributions of currents and vortices over a sample. We have obtained the information about regimes of vortex motion in the different areas of the HT phase diagram and estimated the values of flux flow viscosity and critical current density.  相似文献   
110.
Chemiluminescence has been observed in the reduction of perchloric aqueous solutions of XeO3 with Eu2+ ions, Fast (several seconds) consumption of EuII occurs when the ratio of the initial concentrations of the reactants (Eu2+]0 : [XeO3]0 < 6; however, the chemiluminescence remains sufficiently bright and prolonged (up to –10 min after nearly complete oxidation of EuII to EuIII). The assumption was made that intermediates in the reduction of XeO3 participate in the chemiluminescent stages of the process.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2909–2911, December, 1996.  相似文献   
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