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101.
X. -M. He L. Wang W. -H. Pu J. -G. Ren W. Wu C. -Y. Jiang C. -R. Wan 《Journal of Thermal Analysis and Calorimetry》2008,94(1):151-155
Thermal analysis of sulfurization of polyacrylonitrile (PAN) with elemental sulfur was investigated by thermogravimetry and
differential thermal analysis of the mixture of polyacrylonitrile and elemental sulfur up to 600°C. Due to the volatilization
of sulfur, the different heating rate (10 and 20 K min−1) and different mixture proportion of polyacrylonitrile and elemental sulfur were adopted to run the analysis. The different
heating rates make the DSC curves of sulfur different, but make the DSC curves of PAN similar. In the DSC curve of sulfur
for the heating rate of 20 K min−1 around 400°C, a small exothermic peak occurs at 400°C in the wide endothermic peak around 380∼420°C, indicative of that there
is an exothermic reaction around 400°C. In the DSC curves of the mixture, the peaks around 320°C are exothermic as the content
of sulfur is below 3.5:1 and endothermic as the content of sulfur is over 4:1, indicating that one of the reactions between
PAN and sulfur takes place around 320°C. In the TG curves of the mixture, the mass losses begin at 220°C, and sharply drop
down from 280°C. The curves for the low sulfur content obviously show two steps of mass loss, and curves for the high sulfur
content show only one step of mass loss, indicative of more sulfur is benefit for the complete sulfurization of PAN. This
study demonstrates that the TG/DSC analysis can give the parameter for the sulfurization, even if the starting mixture contains
the volatile sulfur. 相似文献
102.
M. Błachnio P. Staszczuk G. Grodzicka 《Journal of Thermal Analysis and Calorimetry》2008,94(3):641-648
Modified carbon multiwall nanotubes were prepared via the oxidation process by means of 65% nitric acid or ferric nitrate
dissolved with 65% nitric acid. Using special thermogravimetry and sorptometry methods physicochemical properties of pure
and modified nanotube surfaces were investigated. A numerical and analytical procedure for the evaluation of total heterogeneous
properties on the basis of liquid thermodesorption from the sample surfaces under the quasi-equilibrium conditions are presented.
The calculations of the fractal dimensions of carbon nanotubes using the sorptometry and thermogravimetry data is presented. 相似文献
103.
In this paper, a systematic analysis of the errors involved in the determination of the kinetic parameters (including the
activation energy and frequency factor) from five integral methods has been carried out. The integral methods analyzed here
are Coats-Redfern, Gorbachev, Wanjun-Yuwen-Hen-Zhiyong-Cunxin, Junmeng-Fusheng-Weiming-Fang, Junmeng-Fang and Junmeng-Fang-Weiming-Fusheng
method. The results have shown that the precision of the kinetic parameters calculated by the different integral methods is
dependent on u (E/RT), that is, on the activation energy and the average temperature of the process. 相似文献
104.
L. J. Yu S. Wang X. M. Jiang N. Wang C. Q. Zhang 《Journal of Thermal Analysis and Calorimetry》2008,93(2):611-617
Combustion experiments of three typical seaweeds (Gracilaria cacalia, Enteromorpha clathrata and Laminaria japonica) have been studied using a DTA-60H Thermal Analyzer and the combustion processes and characteristics are studied. Thermogravimetric
experiments are carried out on the samples with 0.18 mm particle size at the heating rate of 20°C min−1.
The results indicate that the ignition mode of seaweed is homogeneous and the combustion process is composed of dehydration,
the pyrolysis and combustion of volatile, transition stage, the combustion of char as well as the reaction at high temperature.
And the combustion characteristic parameters are obtained such as ignition temperature, maximum rate of combustion, burnout
temperature etc. The combustion models of these seaweeds are also analyzed. The combustion characteristics and model differences
between the seaweed and woody biomass are caused by the differences of volatile components. The combustibility indexes of
seaweeds calculated are better than that of woody biomass, and the index of Gracilaria cacalia is the best. At last, activation energies are determined using Arrhenius model that is solved by binary linear regression
method. 相似文献
105.
Evidence for the existence of primitive life forms such as lichens and fungi can be based upon the formation of oxalates.
These oxalates form as a film like deposit on rocks and other host matrices. The anhydrous oxalate mineral moolooite CuC2O4 as the natural copper(II) oxalate mineral is a classic example. Another example of a natural oxalate is the mineral wheatleyite
Na2Cu2+(C2O4)2·2H2O.
High resolution thermogravimetry coupled to evolved gas mass spectrometry shows decomposition of wheatleyite at 255°C. Two
higher temperature mass losses are observed at 324 and 349°C. Higher temperature mass losses are observed at 819, 833 and
857°C. These mass losses as confirmed by mass spectrometry are attributed to the decomposition of tennerite CuO. In comparison
the thermal decomposition of moolooite takes place at 260°C. Evolved gas mass spectrometry for moolooite shows the gas lost
at this temperature is carbon dioxide. No water evolution was observed, thus indicating the moolooite is the anhydrous copper(II)
oxalate as compared to the synthetic compound which is the dihydrate. 相似文献
106.
Non-isothermal kinetic analysis and feasibilty study of medium grade crude oil field 总被引:1,自引:0,他引:1
M. V. Kök 《Journal of Thermal Analysis and Calorimetry》2008,91(3):745-748
In this research, non-isothermal kinetics and feasibility study of medium grade crude oil is studied in the presence of a
limestone matrix. Experiments were performed at a heating rate of 10°C min−1, whereas the air flow rate was kept constant at 50 mL min−1 in the temperature range of 20 to 600°C (DSC) and 20 to 900°C (TG). In combustion with air, three distinct reaction regions
were identified in all crude oil/limestone mixtures, known as low temperature oxidation (LTO), fuel deposition (FD) and high
temperature oxidation (HTO). The activation energy values were in the order of 5–9 kJ mol−1 in LTO region and 189–229 kJ mol−1 in HTO region. It was concluded that the medium grade crude oil field was not feasible for a self-sustained combustion process. 相似文献
107.
采用差示扫描量热法(DSC)、热重和微分热重(TG-DTG)及固相原位反应池/快速扫描傅立叶变换红外联用技术(hyphenated in situ thermolysis/RSFTIR)研究了纳米结晶体Ni0.5Zn0.5Fe2O4与高氯酸铵(AP)组成的混合物的热行为和分解反应动力学。结果表明:Ni0.5Zn0.5Fe2O4使得AP的低、高温分解放热峰温分别提前17.44 K和27.74 K,并使得对应的分解热分别增加3.7 J·g-1和193.7 J·g-1。Ni0.5Zn0.5Fe2O4并不影响AP的晶转温度和晶转热。Ni0.5Zn0.5Fe2O4使得AP的TG曲线出现3个阶段,并使得后2个失重阶段的初始和终止温度都有所提前。凝聚相分解产物分析表明Ni0.5Zn0.5Fe2O4加速了凝聚相AP的分解及氨气的释放。含Ni0.5Zn0.5Fe2O4的AP的高温分解反应的动力学参数Ea=238.88 kJ·mol-1,A=1018.59 s-1,动力学方程可表示为dα/dt=1018.99(1-α)[-ln(1-α)]3/5e-2.87×104T。始点温度(Te)和峰顶温度(Tp)计算得出AP的热爆炸临界温度值分别为:574.83 K和595.41 K。分解反应的活化熵(ΔS≠)、活化焓(ΔH≠)和活化能(ΔG≠)分别为:109.61 J·mol-1·K-1、236.49 kJ·mol-1及172.58 kJ·mol-1。 相似文献
108.
109.
B. Zhou S. Jiang L. Zou X. Wang D. Wang J. Liu S. Shang D. Zhou 《Journal of Thermal Analysis and Calorimetry》1999,58(2):487-493
A new compound cyclohexyl-t-butyldimethylammonium tetraphenylborate, [C6H11N(CH3)2(C(CH3)3)]BPh4 has been prepared, and its decomposition mechanism was studied by TG. The IR spectra of the products of thermal decomposition were examined at every stage. Kinetic analysis for the first stage of thermal decomposition process was obtained by TG and DTG curves, and kinetic parameters were obtained from the analysis of the TG-DTG curves with integral and differential equations. The most probable kinetic function was suggested by comparison of kinetic parameters.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
110.
V. J. Fernandes Jr. A. S. Araujo G. J. T. Fernandes 《Journal of Thermal Analysis and Calorimetry》1999,56(2):811-817
A thermogravimetric method is proposed for study of the kinetic parameters of coked HZSM-5 zeolite regeneration. The technique,
which makes use of integral thermogravimetric curves, was optimized by microprocessed integrated mathematical methods. The
kinetic parameters obtained from the TG curves are the activation energy, the rate constants, the half-life times, and in
particular the coke removal time as a function of temperature. The activation energy calculated by using the Flynn and Wall
kinetic method was 81.4 kJ mol−1. It was observed that, to remove 99% of the coke from the zeolite in a period of 1 h, it would be necessary to carry out
thermo-oxidation at 748 K, with a dry air purge flow of 120 cm3 min−1.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献