全文获取类型
收费全文 | 10674篇 |
免费 | 1232篇 |
国内免费 | 1053篇 |
专业分类
化学 | 8027篇 |
晶体学 | 181篇 |
力学 | 419篇 |
综合类 | 87篇 |
数学 | 1333篇 |
物理学 | 2912篇 |
出版年
2024年 | 12篇 |
2023年 | 202篇 |
2022年 | 245篇 |
2021年 | 420篇 |
2020年 | 452篇 |
2019年 | 417篇 |
2018年 | 336篇 |
2017年 | 369篇 |
2016年 | 528篇 |
2015年 | 491篇 |
2014年 | 599篇 |
2013年 | 825篇 |
2012年 | 950篇 |
2011年 | 968篇 |
2010年 | 641篇 |
2009年 | 571篇 |
2008年 | 747篇 |
2007年 | 669篇 |
2006年 | 586篇 |
2005年 | 529篇 |
2004年 | 424篇 |
2003年 | 313篇 |
2002年 | 338篇 |
2001年 | 205篇 |
2000年 | 174篇 |
1999年 | 119篇 |
1998年 | 103篇 |
1997年 | 63篇 |
1996年 | 89篇 |
1995年 | 47篇 |
1994年 | 58篇 |
1993年 | 53篇 |
1992年 | 30篇 |
1991年 | 47篇 |
1990年 | 45篇 |
1989年 | 29篇 |
1988年 | 29篇 |
1987年 | 34篇 |
1986年 | 17篇 |
1985年 | 35篇 |
1984年 | 22篇 |
1983年 | 15篇 |
1982年 | 19篇 |
1981年 | 13篇 |
1980年 | 14篇 |
1979年 | 15篇 |
1978年 | 7篇 |
1977年 | 9篇 |
1976年 | 4篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
21.
Ana Luísa Daniel‐da‐Silva João Carlos Moura Bordado José Miguel Martín‐Martínez 《Journal of Polymer Science.Polymer Physics》2007,45(22):3034-3045
The degree of phase separation in several moisture‐cured poly(urethane urea)s (PUUs) was studied by FTIR spectroscopy, wide angle X‐ray diffraction (WAXD), and temperature‐modulated differential scanning calorimetry (TMDSC). This latter technique was shown to be particularly useful in analysing the degree of phase separation in PUU polymers. Both phase mixing and phase segregation coexisted in the PUUs and the degree of phase separation increased as the urea hard segment (HS) content in the PUU increased. The maximum solubility of urea HSs into the polyol soft segments (SSs) was achieved for 50 wt % urea HS content in diol‐based PUUs, whereas for triol‐based PUUs the highest solubility between HS and SS was reached for lower urea HS amount. Finally, the higher the urea HS content the higher the extent of phase separation in the PUU. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3034–3045, 2007 相似文献
22.
J.-F. Pascual-Sánchez A. San Miguel F. Vicente 《General Relativity and Gravitation》2004,36(9):2075-2083
We analyze the geometry of a rotating disk with a tangential acceleration in the framework of the theory of Special Relativity, using the kinematic linear differential system that verifies the relative position vector of time-like curves in a Fermi reference. A numerical integration of these equations for a generic initial value problem is made up and the results are compared with those obtained in other works. 相似文献
23.
Anna Arkhireeva John N. Hay Jackie M. Lane Miguel Manzano Helen Masters Wilberforce Oware Steve J. Shaw 《Journal of Sol-Gel Science and Technology》2004,31(1-3):31-36
The synthesis of ORganically MOdified SILica (ORMOSIL) particles has been carried out using both the hydrolytic and non-hydrolytic sol-gel routes. The hybrid (nano)composites are organically modified with an alkyl or aryl group covalently bonded to silicon. Hybrids have been synthesised in an aqueous sol-gel process by a modified Stöber route, producing spherical nanoparticles with diameters in the range 50–300 nm. The size of the particles can be controlled by control of certain reaction parameters. Smaller ormosil nanoparticles can be synthesised by a base-catalysed emulsion polymerisation route, by varying the type and concentration of surfactant and precursor feed rate. In this case, particles in the size range 3.5–10 nm can be obtained. Hybrids have been synthesised from hyperbranched polyesters by encapsulation in a silica matrix using the hydrolytic sol-gel route. Optimisation of the reaction conditions allows the hybrids to be produced as isolated sub-micron spherical particles. Ormosil particles have also been synthesised using the non-hydrolytic sol-gel route, which may lead to products of different morphologies because of the different polarity of the reaction medium. Different reaction conditions were studied in order to optimise the size and shape of the particles, including choice of solvent, use of surfactants and addition of polystyrene. Dimethylsulfoxide acts as a novel oxygen donor for the catalyst-free formation of colourless silsesquioxanes. 相似文献
24.
Polypropylene (PP) was modified with elastomer or CaCO3 particles of two different sizes (1 μm and 50 nm) in various volume fractions. The dispersion morphology and mechanical properties of the two systems were investigated as functions of the particle size and volume fraction of the modifier. The brittle‐to‐tough transition occurred when the matrix ligament thickness was less than the critical ligament thickness, which was about 0.1 μm for the PP used here, being independent of the type of modifier. At the same matrix ligament thickness, the improvement of the toughness was obviously higher with the elastomer rather than with CaCO3, but adding CaCO3 increased the modulus of PP. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1656–1662, 2004 相似文献
25.
26.
The aim of this paper is to present construction of finite element multiscaling function with three coefficients. In order to illuminate the result, two examples are given finally. 相似文献
27.
Despite the large cost of bodily injury (BI) claims in motor insurance, relatively little research has been done in this area. Many companies estimate (and therefore reserve) bodily injury compensation directly from initial medical reports. This practice may underestimate the final cost, because the severity is often assessed during the recovery period. Since the evaluation of this severity is often only qualitative, in this paper we apply an ordered multiple choice model at different moments in the life of a claim reported to an insurance company. We assume that the information available to the insurer does not flow continuously, because it is obtained at different stages. Using a real data set, we show that the application of sequential ordered logit models leads to a significant improvement in the prediction of the BI severity level, compared to the subjective classification that is used in practice. We also show that these results could improve the insurer’s reserves notably. 相似文献
28.
José A. Anquela Teresa Cortés Miguel Gómez-Lozano Mercedes Siles-Molina 《Acta Mathematica Hungarica》2004,103(3):177-196
We investigate the basic properties of the different socles that can be considered in not necessarily semiprime associative
systems. Among other things, we show that the socle defined as the sum of minimal (or minimal and trivial) inner ideals is
always an ideal. When trivial inner ideals are included, this inner socle contains the socles defined in terms of minimal
left or right ideals.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
29.
30.