全文获取类型
收费全文 | 5869篇 |
免费 | 824篇 |
国内免费 | 967篇 |
专业分类
化学 | 2738篇 |
晶体学 | 39篇 |
力学 | 886篇 |
综合类 | 102篇 |
数学 | 498篇 |
物理学 | 3397篇 |
出版年
2024年 | 11篇 |
2023年 | 69篇 |
2022年 | 149篇 |
2021年 | 189篇 |
2020年 | 151篇 |
2019年 | 164篇 |
2018年 | 179篇 |
2017年 | 224篇 |
2016年 | 260篇 |
2015年 | 224篇 |
2014年 | 334篇 |
2013年 | 558篇 |
2012年 | 326篇 |
2011年 | 365篇 |
2010年 | 345篇 |
2009年 | 360篇 |
2008年 | 337篇 |
2007年 | 357篇 |
2006年 | 359篇 |
2005年 | 318篇 |
2004年 | 305篇 |
2003年 | 265篇 |
2002年 | 261篇 |
2001年 | 217篇 |
2000年 | 193篇 |
1999年 | 208篇 |
1998年 | 172篇 |
1997年 | 120篇 |
1996年 | 107篇 |
1995年 | 105篇 |
1994年 | 88篇 |
1993年 | 53篇 |
1992年 | 47篇 |
1991年 | 37篇 |
1990年 | 25篇 |
1989年 | 33篇 |
1988年 | 23篇 |
1987年 | 19篇 |
1986年 | 6篇 |
1985年 | 16篇 |
1984年 | 12篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1979年 | 8篇 |
1978年 | 11篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1973年 | 5篇 |
1972年 | 2篇 |
1959年 | 2篇 |
排序方式: 共有7660条查询结果,搜索用时 15 毫秒
41.
本文简述了乳浓聚合动力学研究的进展,着重于澳大利亚Sydney大学Gilbert等在乳液聚合阶段Ⅱ动力学方面的研究概况。介绍了不同水溶性单体的小尺寸种子乳液体系的SmithEwart递推方程的求解方法及其解析解形式和乳液聚合动力学数据的处理。同时讨论了该研究的局限性。 相似文献
42.
Chemical techniques were employed to synthesize CdS nanoparticles embedded in polymer (PEG 300) and sol-gel silica matrices. Systematic growth of particles (radius 3–9 nm) was obtained by adjusting post-deposition annealing temperature and time to examine the dependence of surface-state–related luminescence on particle size. Photoluminescence (PL) peak energy showed a linear dependence with a gentle slope in the weak confinement region and a steep slope in the strong confinement region, the divergence being observed near the excitonic Bohr radius for CdS. The empirical relation proposed for the weak confinement region could be used for estimating chemically prepared CdS nanoparticle size with a high degree of reliability from PL peak energy. 相似文献
43.
Backman Ulrika Jokiniemi Jorma K. Auvinen Ari Lehtinen Kari E.J. 《Journal of nanoparticle research》2002,4(4):325-335
We have prepared spherical non-agglomerated silver nanoparticles by an evaporation–condensation–dilution/cooling technique. Silver was evaporated from a crucible in a tubular flow reactor. A porous tube diluter was used to quench the carrier gas at the outlet of the reactor to enhance the formation of small particles and to suppress agglomeration and other particle growth mechanisms. The number size distribution of the prepared particles was measured with a differential mobility analyser–condensation nucleus counter combination and the size and the shape of the particles were analysed with transmission electron microscope. The system was modelled using a sectional aerosol dynamics computer code to estimate the importance of different aerosol processes. In all conditions the particles obtained were non-agglomerated and spherical. The mean particle diameter varied from 4 to 10-nm depending on boundary conditions. From the modelling studies it can be concluded that the nucleation rate is the most important parameter controlling the final particle size. 相似文献
44.
45.
Upper bounds for survival probability of the contact process 总被引:3,自引:0,他引:3
46.
Dieter Petrak 《Particle & Particle Systems Characterization》2002,19(6):391-400
The objective of this study was to compare the measuring results of a fiber‐optical probe based on a modified spatial filtering technique with given size distributions of different test powders and also with particle velocity values of laser Doppler measurements. Fiber‐optical spatial filtering velocimetry was modified by fiber‐optical spot scanning in order to determine simultaneously the size and the velocity of particles. The fiber‐optical probe system can be used as an in‐line measuring device for sizing of particles in different technical applications. Spherical test particles were narrow‐sized glass beads in the range 30–100 μm and irregularly shaped test particles were limestone particles in the range 10–600 μm. Particles were dispersed by a brush disperser and the measurements were carried out at a fixed position in a free particle‐laden air stream. Owing to the measurement of chord lengths and to the influence of diffraction and divergent angle, the probe results show differences from the given test particle sizes. Owing to the particle‐probe collisions, the mean velocity determined by the probe is smaller than the laser Doppler mean velocity. 相似文献
47.
Tamotsu Kohyama 《Journal of statistical physics》1991,63(3-4):637-651
A class of simple two-dimensional cellular automata with particle conservation is proposed for easy simulations of interacting particle systems. The automata are defined by the exchange of states of neighboring cells, depending on the configurations around the cells. By attributing an energy to a configuration of cells, we can select significant rules from the huge number of possible rules and classify them into several groups, based on the analogy with a binary alloy. By numerical calculations, cluster growth is found in two kinds of phases which reveal gas-solid coexistence and liquid droplets. Normalized scaling functions are obtained, and dynamical scaling is examined. 相似文献
48.
The features of interaction of a spherical metallic particle with a rarefied thermal plasma flow due to the presence o charges-electrons and ions in the gaseous phase-are considered. Analytical expressions describing charge, momentum, and energy exchange between the plasma and the particle für the cases of strong and weak Debye screening are obtained. It is illustrated that the efficiency of particle heating in the plasma considerably grows as compared with a hot molecular gas due to participation of electrons and ions in file transfer processes. 相似文献
49.
50.
Heavy ion irradiation in the electronic stopping power region induces macroscopic dimensional change in metallic glasses and introduces magnetic anisotropy in some magnetic materials. The present work is on the irradiation study of ferromagnetic metallic glasses, where both dimensional change and modification of magnetic anisotropy are expected. Magnetic anisotropy was measured using Mössbauer spectroscopy of virgin and irradiated Fe40Ni40B20 and Fe40Ni38Mo4B18 metallic glass ribbons. 90 MeV 127I beam was used for the irradiations. Irradiation doses were 5×1013 and 7.5×1013 ions/cm2. The relative intensity ratios D 23 of the second and third lines of the Mössbauer spectra were measured to determine the magnetic anisotropy. The virgin samples of both the materials display in-plane magnetic anisotropy, i.e., the spins are oriented parallel to the ribbon plane. Irradiation is found to cause reduction in magnetic anisotropy. Near-complete randomization of magnetic moments is observed at high irradiation doses. Correlation is found between the residual stresses introduced by ion irradiation and the change in magnetic anisotropy. 相似文献