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排序方式: 共有6619条查询结果,搜索用时 15 毫秒
991.
Vapor–liquid equilibria (VLE) and vapor–liquid–liquid equilibria (VLLE) data for the carbon dioxide + 1-heptanol system were measured at 293.15, 303.15, 313.15, 333.15 and 353.15 K. Phase behavior measurements were made in a high-pressure visual cell with variable volume, based on the static-analytic method. The pressure range under investigation was between 0.58 and 14.02 MPa. The Soave–Redlich–Kwong (SRK)-EOS coupled with Huron–Vidal (HV) mixing rules and a reduced UNIQUAC model, was used in a semi-predictive approach, in order to represent the complex phase behavior (critical curve, LLV line, isothermal VLE, LLE, and VLLE) of the system. The topology of phase behavior is qualitatively correct predicted. 相似文献
992.
G. Grindlay L. Gras J. Mora M.T.C. de Loos-Vollebregt 《Spectrochimica Acta Part B: Atomic Spectroscopy》2008
In Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES), it has been observed that the emission intensity of some atomic lines is enhanced or depressed by the presence of carbon in the matrix. The goal of this work was to investigate the origin and magnitude of the carbon-related matrix effects in ICP-AES. To this end, the influence of the carbon concentration and source (i.e. glycerol, citric acid and potassium hydrogen phthalate), the experimental conditions and sample introduction system on the aerosol characteristics and transport, plasma excitation conditions and the emission intensity of several atomic and ionic lines of a total of 15 elements has been studied. Results indicate that carbon related matrix effects do not depend on the carbon source and they become more severe when the amount of carbon loaded into the plasma increases, i.e., when using: (i) carbon concentrations higher than 5 g L− 1; (ii) high sample uptake rates; and (iii) efficient sample introduction systems. Thus, when introducing carbon into the plasma, the emission intensity of atomic lines with excitation energies below 6 eV is depressed (up to 15%) whereas the emission intensity of atomic lines of higher excitation energies (i.e. As and Se) are enhanced (up to 30%). The emission intensity of the ionic lines is not affected by the presence of carbon. The origin of the carbon-related interferences on the emission intensity of atomic lines is related to changes in the line excitation mechanism since the carbon containing solutions show the same aerosol characteristics and transport efficiencies as the corresponding aqueous solutions. Based on the previous findings, a calibration approach for the accurate determination of Se in a Se-enriched yeast certified material (SELM-1) has been proposed. 相似文献
993.
Amine functionalised metal organic frameworks (MOFs) as adsorbents for carbon dioxide 总被引:1,自引:0,他引:1
Bjørnar Arstad Helmer Fjellvåg Kjell Ove Kongshaug Ole Swang Richard Blom 《Adsorption》2008,14(6):755-762
Three different porous metal organic framework (MOF) materials have been prepared with and without uncoordinated amine functionalities
inside the pores. The materials have been characterized and tested as adsorbents for carbon dioxide. At 298 K the materials
adsorb significant amount of carbon dioxide, the amine functionalised adsorbents having the highest CO2 adsorption capacities, the best adsorbing around 14 wt% CO2 at 1.0 atm CO2 pressure. At 25 atm CO2 pressure, up to 60 wt% CO2 can be adsorbed. At high pressures the CO2 uptake is mostly dependent on the available surface area and pore volume of the material in question. For one of the iso-structural
MOF pairs the introduction of amine functionality increases the differential adsorption enthalpy (from isosteric method) from
30 to around 50 kJ/mole at low CO2 pressures, while the adsorption enthalpies reach the same level at increase pressures. The high pressure experimental results
indicate that MOF based solid adsorbents can have a potential for use in pressure swing adsorption of carbon dioxide at elevated
pressures. 相似文献
994.
Carboxylated multiwalled carbon nanotubes (MWCNT-COOH) were used to modify the working electrode surface of different screen-printed electrodes. The effect of this modification on the electrodic characteristics (double layer capacitance, electroactive area and heterogeneous rate constants for the electron transfer) was evaluated and optimized for the cyclic voltammetric determination of p-aminophenol. The enzymatic hydrolysis of p-aminophenylphosphate was employed for the quantification of alkaline phosphatase, one of the most important label enzymes in immunoassays. Finally, ELISA assays were carried out to quantify pneumolysin using this enzymatic system. Results obtained indicated that low superficial densities of MWCNT-COOH (0.03-0.06 μg mm−2) yielded the same electrodic improvements but with better analytical properties. 相似文献
995.
Gold nanoparticles were deposited electrolessly on multiwalled carbon nanotubes (CNTs) via in situ reduction of HAuCl4 by NaBH4. The resulting gold covered nanotubes were immobilised onto the surface of a glassy carbon electrode via evaporation of a suspension in chloroform. Anodic stripping voltammetry was performed with the modified electrode in As(III) solutions. A limit of detection (LOD based on 3σ) of 0.1 μg L−1 was obtained but more importantly a sensitivity of 1985 μA μM−1 was obtained with square wave voltammetry (SWV) in an optimised system with a deposition time of 120 s. These values, particularly the high sensitivity compare favourably with previously reported methods in the area of electrochemical arsenic detection. 相似文献
996.
The electrocatalytic oxidation of sulfite was investigated at carbon ionic liquid electrode (CILE). This electrode is a very good alternative to previously described electrodes because the electrocatalytic effect is achieved without any electrode modification. Comparative experiments were carried out using carbon paste electrode (CPE) and glassy carbon electrode (GCE). At CILE, highly reproducible and well-defined cyclic voltammograms were obtained for sulfite with a peak potential of 0.55 V vs. Ag/AgCl. Sulfite oxidation at CILE does not result in deactivation of the electrode surface. The kinetic parameters for this irreversible heterogeneous electron transfer process were determined. Under optimal experimental conditions, the peak current response increased linearly with sulfite concentration over the range of 6-1000 μM. The detection limit of the method was 4 μM. The method was applied to the determination of sulfite in mineral water, grape juice and non-alcoholic beer samples. 相似文献
997.
We used a carbon paste electrode modified with multi-walled carbon nanotubes as a working electrode and studied the electrochemical
behavior of zirconium-alizarin red S complex on it. It was found that the modified electrode exhibited a significant catalytic
effect toward the reduction of free alizarin red S and the complex. The second derivative linear scan voltammograms of the
complex were recorded by a polarographic analyser from 0 to −1000 mV (vs. SCE), and it was found that the complex can be adsorbed
on the surface of the modified electrode, yielding a peak at about −470 mV, corresponding to the reduction of alizarin red
S in the complex. The linear range was found to be 2.0 × 10−11–8.0 × 10−7 mol L−1, and the detection limit was 1.0 × 10−11 mol L−1 (S/N = 3) for 3 min accumulation. The procedure was successfully applied to the determination of trace amounts of zirconium in
the ore samples.
Correspondence: Pei-Hong Deng, Department of Chemistry and Material Science, Hengyang Normal University, Hengyang Hunan 421008,
P.R. China 相似文献
998.
999.
FCC汽油选择性HDS催化剂的原位红外光谱研究 总被引:1,自引:1,他引:0
采用器外预硫化法制备了碳纳米管(CNT)负载的硫化态Co-Mo-S选择性加氢脱硫催化剂.应用原位红外技术(in-situ IR)对选择性加氢脱硫催化剂(Co-Mo-S/CNT)的表面吸附烯烃特性和HDS过程进行了动态研究.原位红外光谱数据表明:1-辛烯在Co-Mo-S/CNT催化剂表面很容易发生加氢饱和,150℃时完全反应;二异丁烯较难加氢,340℃下归属于=C-H伸缩振动吸收峰的3081cm-1特征峰依然很明显;噻吩的特征峰在280℃左右完全消失,Co-Mo-S/CNT催化剂对二异丁烯和噻吩具有很高的选择性HDS活性,噻吩和二异丁烯在Co-Mo-S/CNT催化剂上的吸附发生在不同的活性位上,不存在相互影响. 相似文献
1000.