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71.
Giuseppina Castronuovo Vittorio Elia Marcella Niccoli Filomena Velleca 《Thermochimica Acta》1998,320(1-2):13-22
The thermodynamics of dissolution in water of a set of substances has been studied calorimetrically. The examined substances were: potassium chloride, (glycyl-glycyl)diketopiperazine, (alanyl-alanyl)diketopiperazine, (leucyl-glycyl)diketopiperazine. They were chosen on the basis of their solubilities, going from a highly soluble electrolyte to the sparingly soluble diketopiperazines. It is shown that, using a commercially available calorimeter, it is possible to perform in a single calorimetric experiment the simultaneous determination of all thermodynamic parameters characterizing dissolution of a substance in a given solvent, i.e. solubility, dissolution enthalpy and dilution enthalpy. The solubility values in water obtained through the proposed method are in good agreement with those reported in the literature and obtained by other techniques. 相似文献
72.
Sergey?P.?BabailovEmail author Lubov?D.?Nikulina 《Journal of inclusion phenomena and macrocyclic chemistry》2005,51(1-2):103-109
1H and 13C NMR measurements are reported for the CDCl3 and CD2Cl2 solutions of [La(NO3)3(18-crown-6)] (I), [Pr(NO3)3(18-crown-6)] (II) and [Ce(NO3)3(18-crown-6)] (III) complexes. Temperature dependencies of the 1H NMR spectra of II have been analyzed using the dynamic NMR methods for multi-site exchange. Two types of conformational dynamic processes in II were identified (the first one with activation enthalpy ΔH
‡=26 ± 4 kJ/mol is conditioned by interconversion of complex enantiomeric form and pseudorotation of macrocycle molecule upon the C
2 symmetry axis, the second one with ΔH
‡=46 ± 5 kJ/mol is conditioned by macrocycle molecule inversion). Studies of the values of the lanthanide-induced shifts revealed that the structure of complexes in solution is similar to that reported for the complex I in the crystal state.This revised version was published online in July 2005 with a corrected issue number. 相似文献
73.
Kanibolotsky D. S. Golovataya N. V. Lisnyak V. V. 《Journal of Thermal Analysis and Calorimetry》2004,76(1):323-327
The enthalpies of mixing of liquid Gd-Si (1770±5 K) and Al-Gd (1760±5 K) alloys have been measured by high-temperature isoperibolic
calorimetry. The calorimetric study of the gadolinium-based liquid alloys demonstrates the great negative enthalpies of mixing,
which is associated with the contribution of GdSi and GdAl2 intermetallides into the liquid-state thermodynamics. The comparison of obtained results with literature data has been performed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
74.
The standard molar enthalpies of formation
f
H
m
°
(l) at the temperature T = 298.15 K were determined using combustion calorimetry for N-methylpiperidine (A), N-ethylpiperidine (B), N-propylpiperidine (C), N-butylpiperidine (D), N-cyclopentylpiperidine (E), N-cyclohexylpiperidine (F), and N-phenylpiperidine (G). The standard molar enthalpies of vaporization
l
g
H
m
° of these compounds were obtained from the temperature variation of the vapor pressure measured in a flow system. From these data the following standard molar enthalpies of formation in gaseous phase
f
H
m
°
(g) were derived for: A –(61.39 ± 0.88); B –(88.1 ± 1.3); C –(105.81 ± 0.66); D –(126.2 ± 1.3); E ( –88.21 ± 0.75); F –(135.21 ± 0.94); G (70.3 ± 1.4) kJ · mol–1. They are used to determine the strain enthalpies of the cyclic amines A–G. The N-alkylated piperidine rings have been found to be about strainless. 相似文献
75.
We have carried out a correlation analysis of some physicochemical characteristics of pyrrole, pyrazole, imidazole, triazole, and tetrazole, calculated by the semiempirical quantum-chemical AM1 method. We have found the linear dependences of the ionization potential, the dipole moment, and the acidity on the -electron excess, and also the dependence of the ionization potential on the enthalpy of formation of the studied azoles. 相似文献
76.
The regions of variation of density, enthalpy of formation, and detonation velocity of all of the formally possible structual isomers were determined for several molecular formulas of C,H,N,O-containing explosives. The histograms of the distribution of the structual isomers over these parameters were constructed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 859–862, May, 1995.The authors are grateful to Mrs. I. D. Solodukhina for the design of the graphical material.The work was carried out with the financial support of the Russian Foundation for Basic Research (Project No. 94-03-09323). 相似文献
77.
利用六种密度泛函理论方法(B3LYP, B3P86, MPW1K, TPSS1KCIS, X3LYP, BMK)对碳氯键离解能进行理论计算,结果发现几种新发展的密度泛函(DFT)方法用于碳氯键离解能的计算比传统的B3LYP有较大的改善,其中对能量估算相对准确的B3P86方法对碳氯键离解能的计算精度最高,对17个分子中碳氯键离解能计算的平均绝对偏差为6.58 kJ/mol。最后运用B3P86方法对一系列环境危害较大,但可通过光化学降解和生物降解的氯代有机物的碳氯键离解能值进行预测,并讨论了影响碳氯键离解能的结构性质关系。 相似文献
78.
Andrea Melchior Martina Sanadar Rosita Cappai Marilena Tolazzi 《Entropy (Basel, Switzerland)》2022,24(9)
Access to the enthalpy and entropy of the formation of metal complexes in solution is essential for understanding the factors determining their thermodynamic stability and speciation. As a case study, in this report we systematically examine the complexation of silver(I) in acetonitrile (AN) with the following monoamines: n-propylamine (n-pr), n-butylamine (n-but), hexylamine (hexyl), diethylamine (di-et), dipropylamine (di-pr), dibutylamine (di-but), triethylamine (tri-et) and tripropylamine (tri-pr). The study shows that the complex stabilities are quite independent of the length of the substitution chain on the N atom and demonstrates that, in general, the overall enthalpy terms associated with the complex formation are strongly exothermic, whereas the entropy values oppose the complex formations. In addition, we examined the similarity of the formation constants of AgL complexes of the primary monoamines in AN, dimethylsulfoxide (DMSO) and water, which were unexpected on the basis of the difference between the donor properties of solvents. 相似文献
79.
Artemiy A. Samarov Stanislav O. Kondratev Sergey P. Verevkin 《Molecules (Basel, Switzerland)》2022,27(23)
Benzophenone derivatives exhibit not only biological activity but also act as photo initiator and UV blocker. We carried out experimental and theoretical thermochemical studies of hydroxy- and methoxy-substituted benzophenones. Standard molar enthalpies of vaporisation were obtained from the temperature dependence of vapour pressures measured by the transpiration method. The thermodynamic data on phase transitions available in the literature (crystal–gas, crystal–liquid, and liquid–gas) were also collected and evaluated. High-level quantum chemical methods G3MP2 and G4 were used to estimate the standard molar enthalpies of formation of substituted benzophenones in the gas phase and establish agreement between experimental and theoretical results. The application of the “centrepiece” group-contribution approach to hydroxy- and methoxy-substituted benzophenones was demonstrated. A quantitative assessment of the hydrogen bond was carried out using various approaches based on experimental data and quantum chemical calculations. 相似文献
80.
Katarzyna Szymczyk Andrzej Lewandowski Anna Zdziennicka Magdalena Szaniawska Bronisaw Jaczuk 《Molecules (Basel, Switzerland)》2022,27(23)
The studies on the behavior of Auramine O (AuO) at the water–air interface and in the bulk phase of the aqueous solution of Kolliphor® ELP (ELP) and Kolliphor® RH 40 (RH40) and their mixture were based on the results obtained from the measurements of the contact angle of water, formamide and diiodomethane on the polytetrafluoroethylene covered by the AuO layer, the surface tension of the aqueous solution of AuO, AuO + ELP, AuO + RH40, AuO + ELP + RH40, density and fluorescence intensity. Based on the obtained results, it was possible to determine components and parameters of the AuO surface tension, concentration and composition of the mixed monolayer, including AuO, ELP and RH40, as well as that of the mixed micelles, and to determine the Gibbs standard free energy of adsorption, micellization and AuO solubilization. The obtained results also showed that surface tension isotherms of the studied solutions can be described by the Szyszkowski equation and the exponential function of the second order and predicted by the Fainerman and Miller equation. In addition, the mixed surface layer composition can be predicted based on the contribution of the components of this layer to the water surface tension reduction. 相似文献