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111.
Speed of sound and density of 1-propanol + heavy water were measured in the whole concentration range at temperatures from 293 to 313 K. Isentropic compressibility was calculated from the Laplace formula. The partial molar volume of 1-propanol reaches a minimum at the mole fraction of 1-propanol x
1 0.03. At the same concentration, the compressibility isotherms intersect one another. These features of the investigated system are similar to those of 1-propanol + H2O, that points to essential similarity of the two mixtures. A clathrate-like structure was suggested to explain the experimental results for dilute solutions of the alcohol. Somewhat more pronounced hydrophobic hydration in D2O than in H2O is manifested by an effect similar to that resulting from the elongation of the alcohol molecule. 相似文献
112.
I. Gascón S. Martín P. Cea M. C. López F. M. Royo 《Journal of solution chemistry》2002,31(11):905-915
Densities and speeds of sound of the binary mixtures 1,3-dioxolane + 1-butanol, 1,3-dioxolane + 2-butanol, 1,4-dioxane + 1-butanol, and 1,4-dioxane + 2-butanol have been measured at 25 and 40°C. The excess molar volumes and excess isentropic compressibility coefficients were calculated from experimental data and fitted to a Redlich–Kister polynomial function. Results were analyzed in terms of molecular interactions and compared with literature data. 相似文献
113.
Gonzalo Cerruela García Irene Luque Ruiz Miguel Ángel Gómez-Nieto 《Journal of mathematical chemistry》2006,40(3):213-231
In this paper, we propose a new method for clustering of chemical databases based on the representation of measurements of structural similarity onto multidimensional spaces. The proposed method permits the tuning of the clustering process through the selection of the dimension of the projection space, the normal vectors and the sensibility of the projection process. The structural similarity of each element regarding to the database elements is projected onto the defined spaces generating clusters that represent the characteristics and diversity of the database and whose size and characteristics can be easily adjusted. 相似文献
114.
Abelló S Medina F Tichit D Pérez-Ramírez J Groen JC Sueiras JE Salagre P Cesteros Y 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(2):728-739
Two different rehydration procedures in the liquid or gas phase have been applied to reconstruct mixed oxides derived from calcined hydrotalcite-like materials to be used as catalysts for aldol condensation reactions. The as-synthesized hydrotalcite, its decomposition product, as well as the reconstructed solids upon rehydration were characterized by XRD, N(2) adsorption, He pycnometry, FTIR, SEM, TEM, (27)Al MAS-NMR and CO(2)-TPD (TPD=temperature-programmed desorption). Compared to the Mg-Al mixed oxide rehydrated in the gas phase (HT-rg), that rehydrated in the liquid phase (HT-rl) exhibits a superior catalytic performance with respect to the aldol condensation of citral with ketones to yield pseudoionones and in the self-aldolization of acetone. The textural properties of HT-rl and HT-rg differ strongly and determine the catalytic behavior. A memory effect led to a higher degree of reconstruction of the lamellar structure when the mixed oxide was rehydrated in the gas phase rather than in the liquid phase, although liquid-phase rehydration under fast stirring produced a surface area that was 26 times greater. This contrasts to typical statements in the literature claiming a higher degree of reconstruction in the presence of large amounts of water in the medium. CO(2)-TPD shows that the number of OH(-) groups and their nature are very similar in HT-rg and HT-rl, and cannot explain the markedly different catalytic behavior. Accordingly, only a small fraction of the available basic sites in the rehydrated samples is active in liquid-phase aldol condensations. Our results support the model in which only basic sites near the edges of the hydrotalcite platelets are partaking in aldol reactions. Based on this, reconstructed materials with small crystallites (produced by exfoliation during mechanical stirring), that is, possessing a high external surface area, are beneficial in the reactions compared to larger crystals with a high degree of intraplatelet porosity. 相似文献
115.
116.
Yinghong Sheng Jerzy Leszczynski Thuc-Quyen Nguyen Anu Bamgbelu 《Structural chemistry》2007,18(6):827-832
A theoretical study using density functional theory was performed to understand the structure/property relationship of the
cationic conjugated polyelectrolytes, poly[9,9-bis-(6′-N,N,N-trimethylammonium) hexyl] fluorene-alt-4,7-(2,1,3-benzothiadiazole)] (PFBT-X, where X = Br). The torsion angle between the fluorene and benzothiadiazole units in the PFBT monomer was found to substantially affect
the structural and electronic properties of the cationic PFBT monomer. The changes of geometrical parameter, HOMO and LUMO energy levels, and band gap, as well as the absorption maximum
are discussed in terms of the torsion in the PFBT monomer structure. For comparison, its neutral analogue, the monomer of
poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) was also studied. The length of conjugation backbone was also examined. 相似文献
117.
B. Roduit Ch. Borgeat B. Berger P. Folly B. Alonso J. N. Aebischer F. Stoessel 《Journal of Thermal Analysis and Calorimetry》2005,80(1):229-236
Summary An advanced kinetic study on the thermal behaviour of pyrotechnic ignition mixtures has been carried out by differential scanning calorimetry using different B/KNO3 mixtures (50:50, 30:70, 20:80) as a model reaction. The experimental conditions applied (isochoric conditions/closed crucibles and isobaric conditions/open crucibles) as well as the composition of the mixtures noticeably influences the relative thermal stabilities of the energetic materials. The kinetic study focused on the prediction of the thermal stability of the different mixtures both in extended temperature ranges and under temperature conditions at which ordinary investigation would be very difficult. Using advanced numerical tools [1], thermal ageing and influence of the complex thermal environment on the heat accumulation conditions were computed. This can be done for any surrounding temperature profile such as isothermal, non-isothermal, stepwise, modulated, shock, adiabatic conditions and additionally for temperature profiles reflecting real atmospheric temperature changes (yearly temperature profiles of different climates with daily minimal and maximal fluctuations). Applications of accurate decomposition kinetics enabled the determination of the time to maximum rate under adiabatic conditions (TMRad) with a precision given by the confidence interval of the predictions. This analysis can then be applied for the examination of the effects of the surrounding temperature for safe storage or transportation conditions (e.g. determination of the safe transport or storage temperatures). 相似文献
118.
2-(8-羟基喹啉-5-磺酸-7-偶氮)-1,8-二羟基-3,6-萘二磺酸与牛血清白蛋白的相互作用 总被引:5,自引:0,他引:5
用平衡透析法和分光光度法研究了 2 (8 羟基喹啉 5 磺酸 7 偶氮 ) 1,8 二羟基 3,6 萘二磺酸与牛血清白蛋白 (BSA)在酸性溶液中的结合反应 ,认为 8Q5SAC与BSA之间的结合力是以静电引力为主的非共键作用力 ,并探讨了其结合模型。在 2 98K下 ,测得这一反应的最大结合数为 35~ 40 ,结合常数为 6 .1× 10 5L mol。还研究了溶液基本条件如酸度和离子强度等对 8Q5SAC与牛血清白蛋白分子复合物形成的影响 ,在pH =3.34条件下 ,标准工作曲线的线性范围为 0 .2 0~ 46 .90mg L。 相似文献
119.
ABSTRACTThis study proposes a simple method of designing a high-speed liquid crystal variable retarder (LCVR) with reflection mode. First, a series of simple formulas is provided for analysing the effects of tilt incidence and birefringence of the liquid crystal on the phase retardation and response time of the LCVR. Then, a reflective LCVR is fabricated to validate the theoretical analysis. Measured results show that the response speed can reach 2.7 kHz with a phase retardation of 1 λ. Furthermore, the theoretical curve is close to the measured curve while the incident angle is less than 10°. However, the theoretical and measured values show a considerable difference under a large incident angle. This problem is discussed, and a modified method is given. This work is helpful for the design and fabrication of high-speed LCVR. 相似文献
120.
The speed of sound u in and densities of eight binary mixtures of p-dioxane (p-C4H8O2) with methylcyclohexane (c-C6H11CH3), 1-chlorohexane (C6H13C1), 1-bromohexane (C6H13Br), p-xylene [C6H4(CH3)2], propylbenzene (C6H5C3H7), methyl acetate CH3COOCH3), butyl acetate (CH3COOC4H9), and amyl acetate (CH3COOC5H11) were measured over the whole composition range at 30°C. Isentropic compressibilities (K
S), Rao's molar sound functions (R), excess molar volumes (V
E), excess isentropic compressibilities (K
S
E
) together with relative change in volume V/12 values, have been obtained for all measured mole fractions. The excess partial molar volume (V1-V
1
0
) of p-dioxane in different solvents have also been estimated. The experimental results have been analyzed in terms of the Prigogine–Flory–Patterson theory of solutions. 相似文献