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61.
62.
本文在两次标准加入法[1]的基础上,提出了三组份同时测定的三次标准加入法,并应用于钼、钨和钛的流动注射同时测定。测定条件:[水杨基荧光酮(SAF)]=1.25 ×10-4mol/L,[溴化+六烷基三甲基铵(CTMAB)」=2.5×10-3mol/L,pH1.35,25℃,采样、进样时间分别为10s和18s,进样频率128次/h。为消除组份间协同作用引起的吸光度加合性的偏离,定义了三组份协同系数。将其引入三组份同时测定方法,补偿了吸光度对线性的偏离。补偿后钼、钨和钛的测定范围分别为0.05~0.35,0.25~1.00,0.025~0.30mg/L。测定了钢样及模拟样品中钼、钨和钛含量,结果较好。 相似文献
63.
Lebedev B. V. Kulagina T. G. Smirnova N. N. Shifrina Z. B. Averina M. S. Rusanov A. L. 《Journal of Thermal Analysis and Calorimetry》2003,74(3):735-748
In an adiabatic vacuum calorimeter, the temperature dependence of the heat capacity C
p of phenylated polyphenylene and initial comonomer 1,4-bis(2,4,5-triphenylcyclopentadienone-3-yl)benzene was studied between
6 and 340 K with an uncertainty of about 0.2%. In a calorimeter with a static bomb and an isothermal shield their energies
of combustion DUcomb were measured. From the experimental data, the thermodynamic functions C
p
0 (T), H
0(T)-H
0(0), S
0(T)-S0(0), G
0(T)-H
0(0) were calculated from 0 to 340 K, and standard enthalpies of combustion ΔH
comb
0 and thermodynamic parameters of formation-enthalpies ΔH
f
0, entropies ΔH
f
0, Gibbs functions ΔG
f
0 - of the substances studied were estimated at T=298.15 K at standard pressure. The results were used to calculate the thermodynamic characteristics (ΔH
f
0 ,ΔS
f
0, ΔG
f
0) of phenylated polyphenylene synthesis in the range from 0 to 340 K.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
64.
This paper reports our results for the direct experimental determination of the equilibrium constant for the hydrogen-isotope-exchange
reaction, 1/2D2(g)+HCl(hexOH)=1/2H2(g)+DCl(hexOD), where hexOH isn-hexanol and hexOD isn-hexanol with deuterium substitution in the alcohol function. The reaction was studied in electrochemical double cells without
liquid junction for which the net cell reaction is the above isotope-exchange reaction. The experimentally determined value
of ε° (296.0°K) for this cell is 4.03±0.95 mV (strong electrolyte standard states, mole-fraction composition scale); the value
of the equilibrium constant for the reaction is 1.17±0.05. The contributions of isotope-exchange and transfer effects to the
magnitude of the standard Gibbs energy change for the above reaction and for the analogous reaction 1/2D2(g)+HCl(aq)=DCl(daq)+1/2H2(g) are considered. Our results support the conclusion of Heinzinger and Weston that the formulation of the solvated proton
in water as H3O+, as opposed to H9O4
+, is sufficient for the interpretation of the thermodynamics of hydrogen-isotope-exchange reactions in water. We also find
that the formulation of the solvated proton inn-hexanol as ROH
2
+
is sufficient for the interpretation of our results on the thermodynamics of hydrogen-isotope-exchange inn-hexanol. 相似文献
65.
Z. H. Zhang Z. J. Ku H. R. Li Y. Liu S. S. Qu 《Journal of Thermal Analysis and Calorimetry》2005,79(1):169-173
The solid-state ternary complex of terbium chloride with L-tyrosine and glycine, [Tb(Tyr)(Gly)3Cl3·3H2O], was synthesized and characterized. Using a solution-reaction isoperibol calorimeter, the enthalpy of reaction for the following reaction, TbCl3·6H2O(s)+Tyr(s)+3Gly(s)=Tb(Tyr)(Gly)3Cl3·3H2O(s)+3H2O(l), was determined to be (5.1±0.6) kJ mol-1. The standard enthalpy of formation of Tb(Tyr)(Gly)3Cl3-3H2O at T=298.15 K has been derived as -(4267.3±2.3) kJ mol-1. The thermal decomposition kinetics of the complex was studied by non-isothermal thermogravimetry in the temperature range of 325-675 K. Two main mass loss stages existed in the process of the decomposition of the complex, the kinetic parameters for the second stage were analyzed by means of differential and integral methods, respectively. Comparing the results of differential and integral methods, mechanism functions of the thermal decomposition reaction for its second stage were proposed. The kinetic equation can be expressed as: d/dt=Aexp(-E/RT)(1-)2. The average values of the apparent activation energy E and pre-exponential factor A were 213.18 kJ mol-1 and 2.51·1020 s-1, respectively. 相似文献
66.
I. Zięborak-Tomaszkiewicz 《Journal of Thermal Analysis and Calorimetry》2006,83(3):611-615
The energies of combustion
in fluorine of gallium nitride and indium nitride in wurzite crystalline structure
have been measured in a two-compartment calorimetric bomb, and new standard
molar enthalpies of formation have been calculated: ΔfHm0(GaN(cr)
298.15 K)= –(163.7±4.2) kJ mol–1
and ΔfHm0(InN(cr) 298.15 K)= –(146.5±4.6) kJ mol–1
. Comparison with the recommended values of the ΔfHm0 nitrides
from the literature is also presented. 相似文献
67.
Quantitative separation of zinc traces from cadmium matrices by solid-phase extraction with polyurethane foam 总被引:1,自引:0,他引:1
Santiago de Jesus D Souza de Carvalho M Spínola Costa AC Costa Ferreira SL 《Talanta》1998,46(6):1525-1530
A system for separation of zinc traces from large amounts of cadmium is proposed in this paper. It is based on the solid-phase extraction of the zinc in the form of thiocyanate complexes by the polyurethane foam. The following parameters were studied: effect of pH and of the thiocyanate concentration on the zinc extraction, shaking time required for quantitative extraction, amount of PU foam necessary for complete extraction, conditions for the separation of zinc from cadmium, influence of other cations and anions on the zinc sorption by PU foam, and required conditions for back extraction of zinc from the PU foam. The results show that zinc traces can be separated from large amounts of cadmium at pH 3.0±0.50, with the range of thiocyanate concentration from 0.15 to 0.20 mol l−1, and the shaking time of 5 min. The back extraction of zinc can be done by shaking it with water for 10 min. Calcium, barium, strontium, magnesium, aluminum, nickel and iron(II) are efficiently separated. Iron(III), copper(II) and cobalt(II) are extracted simultaneously with zinc, but the iron reduction with ascorbic acid and the use of citrate to mask copper(II) and cobalt(II) increase the selectivity of the zinc extraction. The anions nitrate, chloride, sulfate, acetate, thiosulphate, tartarate, oxalate, fluoride, citrate, and carbonate do not affect the zinc extraction. Phosphate and EDTA must be absent. The method proposed was applied to determine zinc in cadmium salts using 4-(2-pyridylazo)-resorcinol (PAR) as a spectrophotometric reagent. The result achieved did not show significant difference in the accuracy and precision (95% confidence level) with those obtained by ICP–AES analysis. 相似文献
68.
We present sets of real 3- symbols which correspond to explicitly given irreducible matrix representations for the two double group hierarchies T* C
3
*
and T* C
2
*
. They fit into the formalism exposed in a previous paper [1] on the general theory of 3- symbols and coupling coefficients and illustrate much of the discussion in a subsequent one [2] treating the particular properties of the double groups. 相似文献
69.
70.
P. De Bièvre 《Accreditation and quality assurance》2000,5(6):224-230
Traceability is a property of the result of a measurement. Since values carried by (reference) materials must also have been
obtained, of necessity, by measurement, the definition of traceability also applies to reference materials. It is extremely
helpful to give the traceability (of the origin) of a reference material a separate name, i.e. 'trackability'. An analysis
of the function of values carried by reference materials, shows that they can fulfill different functions, depending on the
intended use. One of the functions located outside the traceability chain – and hence not very relevant for establishing traceability
– is evaluating the approximate size of the uncertainty of the measurement of an unknown sample by performing a similar measurement
on a reference material, used as a 'simulated sample'. Another function is located inside the traceability chain, where the
reference material is used as an added 'internal standard'. Then, the value carried by the reference material is essential
for establishing the traceability of the measured value of an unknown sample. In the latter application, the reference material
acts as an 'amount standard' (the certified value for amount is used).
Received: 11 November 1999 / Accepted: 24 February 2000 相似文献