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991.
Jun Yang Liwei Zhu Jun Zhang Yuanming Zhang Yu Tang 《Reaction Kinetics and Catalysis Letters》2007,91(1):21-28
Nanosized TiO2/SiO2 catalysts prepared by hydrolysis of titanium n-butoxide in microemulsion showed enhanced photocatalytic activity. In the presence of catalyst ME-2 and after 90 min irradiation
by UV light, methylene blue was completely converted evidenced by the absence of its absorption band in the UV-Vis spectra.
This catalyst demonstrated much better degradation ability than P-25 and naked TiO2. 相似文献
992.
The adsorption of methylene blue (MB) onto zirconium phosphate (ZrP) was studied and the adsorption capacity value and isotherms were determined. The adsorption capacity of ZrP was increased after being exposed to gas phase n-butyl amine. The adsorbed MB on ZrP was used as a modifier material in carbon paste electrode (MCPE), which in turn was used in voltammetric investigations and flow injection (FI) amperometric determination of ascorbic acid (AA). A quasi-reversible electrode reaction of adsorbed MB was exhibited. A home made flow-through electrochemical cell with a suitable transparent window for irradiation of the electrode surface was constructed and used for amperometric FI studies. The photoamperometric-FI conditions were optimised as 1.5 mL min−1 flow rate, a 25 cm transmission tubing length, a 100 μL injection volume, and a constant applied potential of +100 mV versus SCE. The calibration curve for AA was linear over the concentration range from 1.0 × 10−6 to 4.0 × 10−5 M. The relative standard deviation of four replicate injections of 3.0 × 10−5 M AA was 1.2%. The results obtained for AA determination in pharmaceutical products are in good agreement with those obtained using the procedure involving the reaction between triiodide and AA. 相似文献
993.
A simple and rapid spectrophotometric method is proposed for the determination of transparent exopolymer particles (TEP) in freshwater samples. In this method, TEP reacts with excess of alcian blue solution yielding a low solubility dye-TEP complex. After centrifugation, the concentration of the remaining dye in the supernatant was determined at 602 nm and its concentration was related to the concentration of TEP in freshwater. The effect of alcian blue concentration from 1.5×10−3 to 9.0×10−3% (m/v), solution pH from 2.5 to 6.9 and stirring time from 20 to 120 s on the analytical curve was investigated. Under the optimum conditions established, such as alcian blue concentration of 3.0×10−3% (m/v); pH of 4.0 (0.2 mol l−1 acetate buffer solution) and stirring time of 1 min, the analytical curve was linear from 0.50 to 10 μg ml−1 (A=0.34−0.037[GX]; r2=0.9999; where A is the absorbance and [GX] the gum xanthan concentration in μg ml−1) with a detection limit of 0.10 μg ml−1. The recovery of TEP (as gum xanthan) for two samples ranged from 95.3 to 108 and the relative standard deviations (R.S.D.s) were lower than 0.8% for gum xanthan solutions at concentrations of 1.0 and 1.5 μg ml−1 (n=8). The results obtained for TEP in freshwater samples using the proposed spectrophotometric method and those obtained using a literature method are in agreement at the 95% confidence level and within an acceptable range of error. 相似文献
994.
An electrochemical adsorptive stripping approach is presented for the trace measurement of copper in some real samples. The method is based on the reduction of Cu2+ at pH 5.5 calcein blue (CB) containing solution at ?250 mV (vs. Ag/AgCl), adsorption of Cu? CB complex on hanging mercury drop electrode (HMDE) and the voltammetric determination by further reduction to Cu+ at HMDE. Experimental optimum conditions were determined in the fundamental studies. At the experimental optimum conditions the adsorbed complex of Cu2+ and calcein blue gives a well defined cathodic stripping peak current at ?0.135 V, which has been used for the determination of copper in the concentration range of 0.02 to 15 ng/mL with accumulation time of 90 s. The relative standard deviation (RSD) for the determination of 0.5 and 6.0 ng mL?1 were 2.60 and 1.94% respectively. (n=10). The method has been applied to the analysis of copper in analytical reagent grade salts and tap water, mineral water and drug samples with satisfactory results. 相似文献
995.
以乙醇为溶剂, 钛酸四丁酯为前驱体, 用溶剂热法制备了Ag表面修饰的负载型纳米二氧化钛光催化剂. 利用X射线衍射(XRD)、N2吸附-脱附(BET)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱等技术对其进行了系统的表征, 以亚甲基蓝(MB)溶液的脱色降解为模型反应, 考察了不同Ag含量样品的光催化性能. 结果表明: 用溶剂热法制备的样品中TiO2皆为锐钛矿相, 金属Ag颗粒沉积在TiO2表面, 粒径为2 nm左右, 比表面积较溶胶凝胶法制备的样品大大增加, 最高可达151.44 m2·g-1; UV-Vis光谱和光催化实验表明: Ag修饰使TiO2对光的吸收能力大大增强, 吸收带边红移至可见光区, 亚甲基蓝在该复合材料上的光催化降解反应遵循一级反应动力学模型; 溶剂热法制备样品的光催化性能明显好于溶胶凝胶法制备的样品, 在紫外光和可见光下, Ag摩尔分数为5%的样品表现出最佳的光催化活性. 相似文献
996.
A spectrophotometric method is reported for the determination of bismuth in pharmaceutical products using sequential injection analysis. Methylthymol blue (MTB) was used as a color forming reagent and the absorbance of the Bi(III)-MTB complex was monitored at 548 nm. The various chemical and physical variables that affected the reaction were studied. A linear calibration graph was obtained in the range 0.0-75.0 mg l−1 Bi(III) at a sampling frequency of 72 h−1. The reagent consumption was considerably reduced compared to conventional flow injection systems, as only 150 μl of MTB were consumed per run. The precision was very satisfactory (sr=0.5%, at 50.0 mg l−1 Bi(III), n=12) and the limit of detection, cL, was 0.250 mg l−1. The developed method was applied successfully to the analysis of various pharmaceutical products containing Bi(III). The relative errors er, were <1.5% in all cases and were evaluated by comparison of the obtained results with those found using atomic absorption spectrometry as the reference method. 相似文献
997.
Sérgio L. C. Ferreira Bruno F. Santos Jailson B. de Andrade Antonio C. Spinola Costa 《Mikrochimica acta》1996,122(1-2):109-115
The reaction of nickel(II) cation with hydroxynaphthol blue (HNB) in aqueous media at pH 5.2–6.0 results in a red complex that is stable for at least 2h. Beer's Law is obeyed up to 3.2 g/ml of nickel(II) with an apparent molar absorptivity of 1.38 × 104l/mol/cm at 563 nm. This paper proposes procedures for nickel determination by ordinary and first-derivative spectrophotometry. The results demonstrate that the linear dynamic range is 0.08–3.20 g/ml with a limit of detection of 23 ng/ml for ordinary spectrophotometry, compared with 21–800 ng/ml and 6 ng/ml, respectively, for first-derivative spectrophotometry. Calcium(II), magnesium(II), barium(II), strontium(II), cadmium(II), lead(II), manganese(II), bismuth(III) and molybdenum(VI) ions do not interfere for at least 1001 mass ratios. The main interferents are cobalt(II), titanium(IV), aluminium(III), mercury(II) and copper(II). The interferences of titanium(IV), aluminium(III), zirconium(IV) and iron(III) can be masked by fluoride and mercury(II) and copper(II) with thiosulfate or thiourea. The derivative method is applied to nickel determination in standard brasses and the results demonstrate that there is no significant difference between the results and certified values at the 95% confidence level. 相似文献
998.
The effect of temperature of activation on bone charcoal, used as adsorbent for the removal of Patent Blue VF from water solutions was studied. The adsorbent was characterized by FTIR, XRD, SEM and EDS. The kinetic of adsorption of dye was carried out at 10 °C and 45 °C. Carbonization temperature (600–1000 °C) of the adsorbent has significant effect on the removal of dye from water solutions. The first order kinetic, Elovich, Bangham, parabolic diffusion and power function equations were found to fit the kinetic data. Activation energies of adsorption (Δ≠) have higher values for the charcoal activated at high temperatures and the other thermodynamic parameters like ΔH≠, ΔS≠ and ΔG≠ were also found. 相似文献
999.
几种表面活性剂与DNA的相互作用 总被引:7,自引:1,他引:7
用循环伏安、紫外-可见光谱和交流阻抗等方法,以电活性小分子亚甲基蓝( MB)为探针,研究了几种表面活性剂与DNA的相互作用。研究发现,阴离子、阳离 子和非离子表面活性剂均可通过疏水和静电作用与固定在电极表面的DNA分子结合 ,改变电极表面DNA的状态,进而影响电活性小分子的电化学行为。阴离子表面活 性剂与DNA之间以静电排斥为主,也有部分疏水性结合,它使MB的氧化还原峰峰电 流减小。阳离子表面活性剂十六烷基三甲基溴化铵、十二烷基三甲基氯化铵均在一 定浓度范围内对MB的电化学响应有增敏作用,而代十六烷基吡啶、溴代十八烷基吡 啶表现出抑制效应,它们与DNA间既有疏水性作用,也有静电吸引。非离子表面活 性剂与DNA的结合较弱,其主要是通过改变溶液的性质(如粘度、极性和介电常数 等)影响DNA的构象,从而导致MB电化学参数的微弱变化。此外,表面活性剂疏水 链的长短及极性头基的大小对作用过程也有一定影响。 相似文献
1000.
Hyoyoung Lee Jiyoung OhHye Yong Chu Jeong-Ik LeeSeong Hyun Kim Yong Suk YangGi Heon Kim Lee-Mi DoTaehyoung Zyung Jouhahn LeeYongsup Park 《Tetrahedron》2003,59(16):2773-2779
Three new octyloxy substituted spirobifluorenes, 2,7-diphenyl-3′,6′-bis(octyloxy)-9,9′-spirobifluorene (DPBSBF, 1a), 2,7-dibiphenyl-3′,6′-bis(octyloxy)-9,9′-spirobifluorene (DBBSBF, 1b) and 2,7-diterphenyl-3′,6′-bis(octyloxy)-9,9′-spirobifluorene (DTBSBF, 1c) were prepared. All the compounds had been fully characterized by 1H and 13C NMR, UV-Vis, DSC, mass spectrometry and gave satisfactory elemental analyses. They possessed good solubility in common organic solvents and good homogeneous film formation. The optical energy band gap of DBBSBF was 3.27 eV between the HOMO energy level, 5.85 eV, measured by UPS and the LUMO, 2.58 eV, calculated from absorption spectrum. A blue organic light emitting diode (OLED) based on the structure of ITO/TPD (60 nm)/DBBSBF (40 nm)/Alq3 (20 nm)/LiF (1 nm)/Al (100 nm) showed good performance. The luminance of 3125 cd/m2 was observed at a drive voltage of 12.8 V and the colour coordinate in CIE chromaticity was (0.14, 0.12). The external quantum efficiency was obtained to be 2.8% at 100 cd/m2. 相似文献