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91.
Karina A. Araus Roberto I. Canales José M. del Valle Juan C. de la Fuente 《The Journal of chemical thermodynamics》2011,43(12):1991-2001
Modification of an experimental device and methodology improved speed and reproducibility of measurement of solubility of β-carotene in pure and modified SuperCritical (SC) CO2 at (313 to 333) K. Solubilities of β-carotene in pure CO2 at (17 to 34) MPa ranged (0.17 to 1.06) μmol/mol and agreed with values reported in literature. The solubility of β-carotene in CO2 modified with (1.2 to 1.6) % mol ethanol increased by a factor of 1.7 to 3.0 as compared to its solubility in pure CO2 under equivalent conditions. The concentration of triolein in equilibrated ternary (CO2 + β-carotene + triolein) mixtures having excess triolein reached values (0.01 to 0.39) mmol/mol corresponding to its solubility in pure SC CO2 under equivalent conditions. Under these conditions, the solubility of β-carotene in triolein-modified CO2 increased by a factor of up to 4.0 in relation with its solubility in pure CO2 at comparable system temperature and pressure, reaching an uppermost value of 3.3 μmol/mol at 333 K and 32 MPa. Unlike in the case of ethanol, where enhancements in solubility where relatively independent on system conditions, solubility enhancements using triolein as co-solvent increased markedly with system pressure, being larger than using (1.2 to 1.6) % mol ethanol at about (24 to 28) MPa, depending on system temperature. The increase in the solubility β-carotene in SC CO2 as a result of using ethanol or triolein as co-solvent apparently does not depend on the increase in density associated with the dissolution of the co-solvent in CO2. Enhancements may be due to an increase in the polarizability of SC CO2, which possibly growths markedly as triolein dissolves in it when the system pressure becomes higher. 相似文献
92.
X. G. Li Z. Y. Gao B. Jia R. Jiang 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(3):385-391
Segregation effects commonly exist in granular mixtures
with difference in size, shape or density. In mixed traffic flow,
slow vehicle and fast vehicle, as two types of particles, have
different desired speed. We investigate the segregation along the
road in mixed traffic flow by using a symmetric two-lane cellular
automata model. A parameter D, which quantifies the degree of
segregation, is defined. We study the density dependency of the
parameter at different randomization probability. Simulation results
show that segregation is more obviously in free flow region. We
argue that the overtaking maneuvers have similar effect as
percolation in granular flow. 相似文献
93.
A. Trovato J. van Mourik A. Maritan 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,6(1):63-73
A lattice model of a hetero-polymer with random hydrophilic-hydrophobic charges interacting with the solvent is introduced,
whose continuum counterpart has been proposed by Garel, Leibler and Orland [#!GLO!#]. The transfer matrix technique is used
to study various constrained annealed systems which approximate at various degrees of accuracy the original quenched model.
For highly hydrophobic chains an ordinary -point transition is found from a high temperature swollen phase to a low temperature compact phase. Depending on the type
of constrained averages, at very low temperatures a swollen phase or a coexistence between compact and swollen phases are
found. The results are carefully compared with the corresponding ones obtained in the continuum limit, and various improvements
in the original calculations are discussed.
Received: 10 April 1998 / Revised: 4 June 1998 / Accepted: 1st July 1998 相似文献
94.
Irina V. Glinkina Vladimir A. Durov Galina A. Mel''nitchenko 《Journal of Molecular Liquids》2004,110(1-3):63-67
Modelling of the biologic solutions has a great importance for basic physicochemical backgrounds of the living processes, mechanism of the diseases and drugs action, etc. The modelling of the chemical equilibria in solution that served as a prototype of the blood plasma with application to calcification of the tissues is performed. The concentrations of molecular–ionic forms containing calcium and hydrogen cations and phosphate anions in the range of ionized-calcium and total phosphorus concentrations from 0.5 to 3.0 mM and at the solution pH of 7.1–7.8 were calculated. The activities of the ionized species were described in approach to Debye–Hückel's theory. The full set of the equilibria taking into consideration dissociation of the water, phosphoric acid, formation of both inert and ionic calcium phosphates was considered. The states of calcium hydrophosphate dihydrate CaHPO4·2H2O (CHPD), calcium phosphate Ca3(PO4)2 (CP), calcium hydrophosphate-phosphate dihydrate Ca4H(PO4)3·2H2O (CHPPD) and hydroxyapatite Ca3OH(PO4)3 (HA) with respect to the boundary of the region in which they crystallise were determined. A criterion has been introduced to characterize the degree of salt supersaturation with respect to crystallisation, which is based on the concentration distance between the states of a salt in solution and at the boundary of its crystallisation. This criterion is used to provide a quantitative characteristic of the supersaturation of the phosphates and their tendency to crystallise in blood's plasma. It was established that the most soluble of the phosphates, CaHPO4·2H2O, is undersaturated and the other phosphates are supersaturated with respect to crystallisation. Thus, this phosphate does not take part in the calcification, and this is the source for ionized calcium in a blood plasma from the soft tissues. The role of the other phosphates in calcification of the soft tissues is decreased in the series HA>CP>CHPPD. The dependencies of the supersaturation of the solution on the pH and on the concentrations of calcium and phosphorus in a mixture are discussed. 相似文献
95.
The solubility of ethane in ethylene glycol (EG) has been determined at temperatures in the range 298–398 K at pressures up to 20 MPa. The experimental results were correlated by the Peng–Robinson equation of state, and interaction parameters have been obtained for this system. The parameters in the Krichevsky–Ilinskaya equation were calculated from these interaction parameters. 相似文献
96.
本工作合成了以聚α-甲基苯乙烯(PαMS)为硬段、聚丁二烯(PBD)及氢化聚丁二烯(HPBD)为软段的两种ABA型三嵌段共聚物。研究了其合成方法、结构与性能,虽然这两种三嵌段共聚物软段T_g相近,均在-25℃左右,但由于氢化聚丁二烯的溶度参数很高,与聚α-甲基苯乙烯的相容性大,以致PαMS-HPBD-PαMS的断裂伸长,断裂强度及回弹性和硬段T_g均较之PαMS-PBD-PαMS有明显下降。 相似文献
97.
98.
Shvedene NV Borovskaya SV Sviridov VV Ismailova ER Pletnev IV 《Analytical and bioanalytical chemistry》2005,381(2):427-430
Polyvinyl chloride-plasticized membrane ion-selective electrodes (ISE) based on conventional ion-exchangers have been proposed as a cheap universal tool to measure the solubilities of ionic liquids (ILs) in water. They are applicable for ILs with a wide range of solubilities in water, since the linear range of a potentiometric response spans several orders of magnitude. As an example, we have fabricated and tested ISEs for widely used alkylimidazolium ionic liquids. The aqueous solubilities of four typical ILs have been determined at 21 °C: 0.075±0.001 mol l–1 (1-butyl-3-methylimidazolium, BMIm, hexafluorophosphate); 0.018±0.001 mol l–1 (BMIm bis(triflylimide)); 0.054±0.007 mol l–1 (1-butyl-2,3-dimethylimidazolium, BDMIm, hexafluorophosphate); 0.014±0.001 mol l–1 (BDMIm bis(triflylimide)). 相似文献
99.
100.
求取二氧化碳在饱和液态甲烷中的溶解度,对于在较高温度下实现液化天然气至关重要。文中在理想溶液基础上,采用正规溶液关系式和改进的Scatchard-H ildebrand关系式进行二氧化碳的溶解度计算,并且在临界点附近采用经验公式对其进行修正。将上述计算结果与Davis实验数据进行比较后表明,改进的正规溶液理论计算方法在低于140K温区时可推荐用于此项溶解度计算,经验公式可用于接近临界温度区域的溶解度计算。 相似文献