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991.
稀土钬丙氨酸配合物的热力学性质 总被引:1,自引:0,他引:1
合成了稀土氯化钬丙氨酸配合物,[Ho2(Ala)4(H2O)8]Cl6,的晶体.用绝热量热法测定了其在78~363 K温区的热容.在214~255 K温区发现一固-固相变,相变峰温、相变焓和相变熵分别为235.09 K,3.017 kJ•mol-1和12.83 J•K-1•mol-1.用最小二乘法将实验热容值拟合成热容随温度变化的多项式方程,利用此方程式和热力学函数关系,计算出以298.15 K为参考温度的热力学函数值.在40~800 ℃温区,用热重分析和差示扫描量热法研究了该配合物的热稳定性,观察到[Ho2(Ala)4(H2O)8]Cl6分两步分解,第一步从80 ℃开始,179 ℃结束;第二步从242 ℃开始,479 ℃结束.从热分析结果推测出该配合物可能的热分解机理. 相似文献
992.
L. K. Neudachina Yu. G. Yatluk N. V. Baranova A. V. Pestov A. A. Vshivkov A. Yu. Plekhanova M. V. Zorina 《Russian Chemical Bulletin》2006,55(5):828-834
Two types of chelating sorbents with different types of addition of iminodipropionate groups to a polymeric matrix were synthesized:
carboxyethylated aminopolystyrene (sorbent 1) based on linear polystyrene and carboxyethylaminomethylpolystyrene (sorbent 2) based on the copolymer of styrene and divinylbenzene. The ionization constants and concentrations of functional groups of
the sorbents (exchange capacity for hydrogen ions) were determined. The sorbents exhibit high selectivity for copper(II) ions
with the maximum of sorption from ammonia—acetate buffer solutions lying in a range of pH 5.0–7.5. The time needed for a solution
of copper(II)—sorbent system with continuous stirring to reach exchange equilibrium is 3.5 and 2 h for sorbents 1 and 2, respectively. The exchange capacity for copper(II) ions is 2.54 and 0.10 mmol g−1, respectively.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 800–806, May, 2006. 相似文献
993.
I. Vélaz J. R. Isasi M. Sánchez M. Uzqueda G. Ponchel 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):65-68
Several β-cyclodextrin polymers (βCDP) have been obtained by cross-linking β-cyclodextrin (βCD) with the reagent epichlorohydrin
(EP). It is expected that these polymers are capable of retaining different organic molecules by adsorbing them on its network
and also by forming inclusion complexes with βCDs. In this work, two soluble polymers containing 39% and 48% βCD and other
insoluble ones with 65% and 74% βCD have been studied. The total amount of CD in the polymers could not be available for complexation.
This parameter has been calculated by means of the decrease of colour intensity of phenolphthalein solutions when different
amounts of βCDP were added. The insoluble polymer with 74% βCD appears to possess less CD available than that with 65% βCD,
probably due to the higher cross-linking degree of the former. On the other hand, a higher availability of CD is found for
the soluble polymer which contains 48% βCD. Moreover, the amount of glycerol monoether groups formed as a side effect during
the cross-linking process has been determined and related to the epichlorohydrin content, structure and swelling properties
of the polymers. It is concluded that, varying the synthesis conditions, it is possible to induce structural modifications
in the hydrogel networks which can improve their practical applications. 相似文献
994.
Quantitative thermal analysis was carried out for poly-(pivalolactone) (PPVL), including heat capacity determinations from 140 to 550 K. The experimental Cp below the glass transition temperature was fitted to an approximate vibrational spectrum and the ATHAS computation scheme was used to compute the “vibration only” heat capacities from 0.1 to 1000 K. The liquid Cp was derived from an empirical addition scheme and found to agree with the experimental Cp with an RMS of ±2.8% from 240 K to 550 K. A glass transition, Tg, could be detected at 260 K, and the change in heat capacity for 100% amorphous PPVL was calculated to be 38.8 J/(K mol). Above Tg, semicrystalline samples seem to show a rigid amorphous fraction that does not contribute to the increase in heat capacity at Tg. Using the ATHAS recommended heat capacities, the various thermodynamic functions (enthalpy, entropy, and Gibbs function) were derived. The residual entropy at 0 K for the amorphous PPVL was calculated to be 5.2 J/(K mol) per mobile bead, and was comparable to that obtained for a series of linear, aliphatic polyesters analyzed earlier. 相似文献
995.
Summary A low-capacity, anion-exchange, porous-polymer resin was used as the packing material in a microbore column. Using a phosphate buffer containing various organic modifiers, retention behavior of substituted benzoic acid isomers with amino, chloro, methyl, nitro and carboxylic groups was investigated. The effect of ethanol, acetonitrile and sodium dodecylsulfate used as organic modifiers on the retention behavior at various eluent pH values was studies and optimum separations of the positional isomers reported. 相似文献
996.
Wojciech Zielenkiewicz Anna Zielenkiewicz Jean-Pierre E. Grolier Alain H. Roux Geneviève Roux-Desgranges 《Journal of solution chemistry》1992,21(1):1-13
Densities and apparent molar heat capacities of some alkylated derivatives of uracil and adenine: 1-methyluracil, 1,3-dimethyluracil, 1,3-diethylthymine, 5,6-trimethylene-1,3-dimethyluracil, 5,6-tetramethylene-1,3-dimethyluracil, 5,6-pentamethylene-1,3-dimethyluracil, 2,9-dimethyladenine, 2-ethyl-9-methyladenine, 2-propyl-9-methyladenine, 8-ethyl-9-methyladenine, 6,8,9-trimethyladenine and 8-ethyl-6,9-dimethyladenine were determined using flow calorimetry and flow densimetry at 25°C. It was found that the partial molar volumes and heat capacities correlate linearly with the number of substituted methylene groups-CH
2
-as well as to the number of hydrogen atoms, n
H
, belonging to the skeleton of the molecule. In the case of alkylated uracils a difference was observed in the values at infinite dilution V
2
o
and C
p2
o
, depending on the substitution of alkyl and cyclooligomethylene groups. 相似文献
997.
本文从信息论观点出发,将彩色照相材料作为一个客观景物信息的传输通道,其单个空间可分辨面积构成一个独立信道,照相材料是大量独立信道并联组成的扩展信道,并提出了使用复层Shannon熵计算彩色照相材料独立信道容量的方法。作者在PDS显微光密度计——电子计算机系统上发展了全套测试计算程序,并完成了中国1821型彩色红外航空负片的信道容量测试。 相似文献
998.
The first measurements of the enthalpies of combustion, sublimation, and fusion of an organo-phosphorus sulfide, triphenylphosphine sulfide, are reported: c
H
m
o
(C18H15PS, cr)=–(10752.58 ±2.90), sub
H
m
o
(C18H15PS, 403 K)=(136.80±6.09), and fus
H
m
o
(C18H15PS, Tm=435.92 K) =(30.53±0.21) kJ·mol–1. Correction of the phase change enthalpies toT=298.15K and po =0.1 MPa results in the standard phase change enthalpy values of sub
H
m
o
(298.15 K)=(142.8 ±6.8) and fus
H
m
o
(298.15 K)=(19.28±0.21) kj·mol–1. Accordingly, the enthalpies of formation of solid, liquid, and gaseous triphenylphosphine sulfide are derived: f
H
m
o
(C18H15PS, cr) =(63.20±2.56), fH
m
o
(C18H15PS, l)=(82.48±2.57), and fH
m
o
(C18H15PS, g)=(206.0±7.3) kJ·mol–1. From these ancillary data, the P=S double-bond enthalpy is 394 kJ-mol–1 and in good agreement with earlier reaction calorimetry results. These phosphorus sulfide values are compared with those for the arsenic sulfides. Plausibility arguments are given for our results. 相似文献
999.
R. Chartoff 《Journal of Thermal Analysis and Calorimetry》2006,85(1):213-217
We have studied the compound MnAs with a giant magnetocaloric
effect, which has a magneto-structural transition at 316 K. The magnetic phase
diagram has been deduced from adiabatic heat-capacity measurements and from
cooling and heating curves. The ferroto paramagnetic transition changes with
field from 316 K at 0 T to 335.3 K at 6 T. There is a strong thermal hysteresis
between 10 and 5 K, depending on field. Direct measurements of the adiabatic
temperature change caused by the application of magnetic field were made and
compared with the values deduced from heat-capacity data.Moreover, adiabatic
field cycles were performed quasi-statically between 0 and 6 T around the
phase coexistence region, showing the strength of the effect in each phase
and on the coexistence lines. 相似文献
1000.
Surface Tension, Heat Capacity, and Volume of Amphiphilic Compounds in Formamide Solutions 总被引:1,自引:0,他引:1
Americo Inglese Pietro D'Angelo Rosario De Lisi Stefania Milioto 《Journal of solution chemistry》1998,27(5):403-424
Density measurements of sodium dodecyl sulfate (SDS), sodium decyl sulfate (SDeS), sodium octyl sulfate(SOS), and sodium hexyl sulfate(SHS) in formamide (FA) as functions of the surfactant concentrations were carried out at 25°C. For SDS in FA, additional density measurements at 35 and 60°C and surface tension and specific heat capacity measurements at 25°C were also performed. From density and specific heat capacity data, the apparent molar volume and heat capacity of the surfactants as functions of concentration were calculated. The surface excess of SDS at the solution–air interface was also determined from the surface tension measurements using the Gibbs adsorption equation. Under our experimental conditions, none of the experimental results evidence micelle formation. In addition, volumetric studies of the hexanol–SDS–FA ternary system at 25°C evidence only interactions between the dispersed surfactant and alcohol. 相似文献