全文获取类型
收费全文 | 5875篇 |
免费 | 486篇 |
国内免费 | 495篇 |
专业分类
化学 | 1401篇 |
晶体学 | 24篇 |
力学 | 2272篇 |
综合类 | 104篇 |
数学 | 1383篇 |
物理学 | 1672篇 |
出版年
2024年 | 12篇 |
2023年 | 48篇 |
2022年 | 95篇 |
2021年 | 177篇 |
2020年 | 165篇 |
2019年 | 129篇 |
2018年 | 141篇 |
2017年 | 222篇 |
2016年 | 310篇 |
2015年 | 214篇 |
2014年 | 264篇 |
2013年 | 402篇 |
2012年 | 262篇 |
2011年 | 307篇 |
2010年 | 266篇 |
2009年 | 321篇 |
2008年 | 322篇 |
2007年 | 310篇 |
2006年 | 310篇 |
2005年 | 293篇 |
2004年 | 294篇 |
2003年 | 235篇 |
2002年 | 202篇 |
2001年 | 184篇 |
2000年 | 162篇 |
1999年 | 146篇 |
1998年 | 134篇 |
1997年 | 129篇 |
1996年 | 128篇 |
1995年 | 102篇 |
1994年 | 97篇 |
1993年 | 64篇 |
1992年 | 57篇 |
1991年 | 49篇 |
1990年 | 43篇 |
1989年 | 30篇 |
1988年 | 27篇 |
1987年 | 29篇 |
1986年 | 31篇 |
1985年 | 26篇 |
1984年 | 21篇 |
1983年 | 5篇 |
1982年 | 31篇 |
1981年 | 8篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 5篇 |
1974年 | 4篇 |
1973年 | 4篇 |
排序方式: 共有6856条查询结果,搜索用时 15 毫秒
81.
82.
Three series of pressure‐sensitive adhesives were prepared with constant glass‐transition temperature, using emulsion polymerization. The monomers chosen were butyl acrylate, 2‐ethylhexyl acrylate (EHA), methyl methacrylate (MMA), and acrylic acid (AA). Within each polymer series, the proportion of AA monomer was held constant for each polymer preparation but acrylic ester monomer levels were varied. Adhesion performance was assessed by measurement of loop tack, static shear resistance, and through the construction of peel master‐curves. Peel master‐curves were generated through peel tests conducted over a range of temperatures and peel rates and through application of the time–temperature superposition principle. Bulk effects dominated by polymer zero shear viscosity change as AA and EHA levels were varied were attributed to the observed effect on static shear resistance and the horizontal displacements of peel master‐curves. Static shear resistance was found to strongly correlate with log(aC), a parameter introduced to horizontally shift peel master‐curves to form a superposed, “super master‐curve”. An interfacial interaction was proposed to account for deviations observed when loop tack was correlated with log(aC). Surface rearrangements via hydrogen bonding with the test substrate were suggested as responsible for the interfacial interaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1237–1252, 2006 相似文献
83.
生产函数有着相应的经济理论背景,是以科学的数据为样本,反复拟合、检验、修正后得到的,揭示产出量与生产要素资本和劳动之间内在的必然的统计相关关系,是科学的结论。本文就此与余斌、程立茹先生进行探讨和商榷。 相似文献
84.
Thermoanalytical characterization of carbon/carbon hybrid material, Apple Woodceramics 总被引:3,自引:0,他引:3
Woodceramics, a carbon/carbon composite of plant-originated carbon reinforced by glassy carbon from phenolic resin, was prepared from apple pomace at carbonizing temperatures of 1073 K (AWC800) and 1473 K (AWC1200), and characterized by thermoanalytical methods and X-ray diffraction (XRD). Simultaneous differential scanning calorimetry (DSC) and thermogravimetric (TG) showed complicated overlapping reactions similar to those of coal. The initial temperature of pyrolysis was obtained by fitting logistic functions to observed TG data. The results suggested that AWC1200 contained more volatile matter than AWC800. In an inert atmosphere, complicated devolatilization takes place. In an oxidizing atmosphere, thermal change occurs roughly in four steps: desorption of physically adsorbed matter; pyrolysis into aliphatic and aromatic fragments; ignition; combustion of char. The oxidation resistance of AWC1200 was superior to AWC800. 相似文献
85.
Suzdalev I. P. Buravtsev V. N. Maksimov Yu. V. Zharov A. A. Imshennik V. K. Novichikhin S. V. Matveev V. V. 《Russian Chemical Bulletin》2003,52(9):1950-1958
Magnetic phase transitions of the first and second order were revealed by Mössbauer spectroscopy in nanosystems of - and -ferric oxides and metallic europium subjected to shear stress (240°) under high pressure (20 kbar). For - and -ferric oxide nanoclusters, the Curie (Neel) points decreased to 300 K, whereas for nanostructured europium the Neel point increased from 90 to 100 K. The thermodynamic model of magnetic phase transitions predicting a change in the character of magnetic phase transitions and a decrease (increase) in the critical Neel (Curie) points in nanoclusters was developed. The type of magnetic phase transitions and the change in the critical points were caused by defects in nanoclusters, whose maximum concentration was observed for the clusters with the 20—50 nm size range. 相似文献
86.
E. P. Honig 《Rheologica Acta》1987,26(1):2-6
Equations are derived for the coaxial cylinder system in the combined oscillatory and steady-state shear mode. The limitations of the use of the various equations are presented. If the usual linear equations are used, the main limitation, in the case of oscillatory shear only, is that the frequency of measurement should be below 0.016 |
*|/(r
2
–r
1
)2. Here |
*| is the modulus of the complex viscosity, is the density of the liquid andr
1
andr
2
are the radii of the cylinders. Furthermore it is shown that there is a small error in the numerical factor of the usually applied equations. The calculations are set up in such a way that extension to higher harmonics follows in a natural way. An experimental example illustrates the use of the derived equations. 相似文献
87.
88.
A three-dimensional pharmacophore model was developed from a series of inhibitors of Aurora A kinase to discover new potent anti-cancer agents using the HypoGen module in the Catalyst software. The pharmacophore model was developed based on the structure of 20 currently available inhibitors, which were carefully selected from the literature. The best hypothesis (Hypo 1) was defined by four features: one hydrogen-bond donor and three hy- drophobic points, with the best correlation coefficient of 0.909, the lowest rms deviation of 1.563, and the highest cost difference of 99.075. The Hypo 1 was then validated by a test set consisting of 24 compounds and by a cross-validation of 95% confidence level through randomizing the data using the CatScramble program, which suggested that a predictive pharmacophore model had been successfully obtained. 相似文献
89.
90.
Matteo Scampicchio Nathan S. Lawrence Alessandra Arecchi Stella Cosio Saverio Mannino 《Electroanalysis》2007,19(1):85-90
Cyclic voltammetry has been applied to the rapid measurement of free SH‐compounds in food flours samples. The protocol is based on the electrochemical adaptation of the Ellman's test, where the DTNB reacts with SH‐compounds present in food flour extracts, resulting in the equimolar production of the electroactive compound TNBA which, in turns, reacts with phenylendiamine. The reaction is found to provide an analytical signal from which to quantify indirectly free sulfhydryl compounds in flours extracts. 相似文献