全文获取类型
收费全文 | 7431篇 |
免费 | 464篇 |
国内免费 | 689篇 |
专业分类
化学 | 5999篇 |
晶体学 | 140篇 |
力学 | 711篇 |
综合类 | 12篇 |
数学 | 152篇 |
物理学 | 1570篇 |
出版年
2024年 | 12篇 |
2023年 | 86篇 |
2022年 | 111篇 |
2021年 | 124篇 |
2020年 | 230篇 |
2019年 | 182篇 |
2018年 | 177篇 |
2017年 | 258篇 |
2016年 | 389篇 |
2015年 | 295篇 |
2014年 | 311篇 |
2013年 | 539篇 |
2012年 | 429篇 |
2011年 | 491篇 |
2010年 | 398篇 |
2009年 | 539篇 |
2008年 | 400篇 |
2007年 | 467篇 |
2006年 | 426篇 |
2005年 | 341篇 |
2004年 | 296篇 |
2003年 | 222篇 |
2002年 | 162篇 |
2001年 | 159篇 |
2000年 | 136篇 |
1999年 | 134篇 |
1998年 | 121篇 |
1997年 | 95篇 |
1996年 | 89篇 |
1995年 | 91篇 |
1994年 | 100篇 |
1993年 | 70篇 |
1992年 | 57篇 |
1991年 | 67篇 |
1990年 | 54篇 |
1989年 | 32篇 |
1988年 | 62篇 |
1987年 | 42篇 |
1986年 | 46篇 |
1985年 | 47篇 |
1984年 | 59篇 |
1983年 | 33篇 |
1982年 | 68篇 |
1981年 | 39篇 |
1980年 | 30篇 |
1979年 | 36篇 |
1978年 | 13篇 |
1976年 | 5篇 |
1973年 | 5篇 |
1957年 | 2篇 |
排序方式: 共有8584条查询结果,搜索用时 15 毫秒
41.
42.
In this Letter, structural properties of liquid Ni20Al80 have been studied through molecular dynamics (MD) simulations, and results agree well with X-ray experiments. The prepeak in the structure factor manifests the existence of medium-range structural order (MRSO) in liquid Ni20Al80. Analyses in MRSO reveal the dominance of ideal icosahedra and defective icosahedra which, furthermore, form clusters and share common atoms. 相似文献
43.
Summary The nematic planar anchoring is usually explained by using simple elastic models: the surface easy axis corresponds to the
surface direction that minimizes the excess of nematic elastic energy. When anisotropic rough substrates are used to align
nematic liquid crystals, due to the complex surface morphology, usual elastic models are not directly applicable. This paper
presents quantitative topographical data of rough substrates, obtained with oblique SiO evaporation under vacuum for nematic
planar anchoring. Experimental data are obtained by means of Atomic Force Microscopy and they are used to demonstrate the
self-affine nature of these substrates and to relate the nematic anchoring with the anisotropy of the local fractal properties
of the substrate itself.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. 相似文献
44.
Liquid crystal lens with focus movable in focal plane 总被引:1,自引:0,他引:1
A liquid crystal lens with focus movable in the focal plane is reported. There are three electrodes in the cell. One electrode with a hole in the center is divided into four subelectrodes. The potential of each subelectrode is adjusted to produce a desired asymmetrical phase transformation resulting in off-axis movement of the focus. The potential of another electrode is adjusted to maintain the focus in the focal plane. Movements of the focus in three directions in the focal plane are demonstrated experimentally, and off-axis movement as large as approximately 800 μm is realized. 相似文献
45.
Reverse-mode polymer stabilized cholesteric texture (PSCT) cells with various chiral dopant and monomer concentrations were fabricated. Experimental results indicate that the chiral dopant concentration and the monomer concentration significantly influence the threshold voltage and hysteresis of the cells. The chiral dopant and monomer deform the hysteresis loop. Increasing the monomer concentration reduces the width of the hysteresis loop of the reverse-mode PSCT cell. 相似文献
46.
Hyeong Taek Ham Yeong Suk Choi Mu Guen Chee In Jae Chung 《Journal of polymer science. Part A, Polymer chemistry》2006,44(1):573-584
This work is to make carbon nanotubes dispersible in both water and organic solvents without oxidation and cutting nanotube threads. Polystyrene‐singlewall carbon nanotube (PS‐SWNT) composites were prepared with three different methods: miniemulsion polymerization, conventional emulsion polymerization, and mixing SWNT with PS latex. The two factors, crosslinking and surface coverage of PS are important factors for the mechanical and electrical properties, including dispersion states of SWNT in various solvents. The PS‐SWNT composite prepared via a conventional emulsion polymerization showed SWNT bundles entirely covered with PS, whereas the PS‐SWNT composite prepared via a miniemulsion polymerization showed SWNT partially covered with crosslinked PS nanoparticles. The method of mixing SWNTs with PS latex did not show the well dispersed state of carbon nanotubes because PS was not crosslinked and was dissolved in a solvent, and nanotubes separated from PS precipitated. So the PS nanoparticle‐SWNT composite had lower electrical resistance, and higher mechanical strength than the other composites made by the latter two methods. As the amount of SWNT increases, the bare surface area of SWNT increases and the electrical conductivity increases in the composite made by the miniemulsion polymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 573–584, 2006 相似文献
47.
Tzong‐Ming Wu Shih‐Hsiang Lin 《Journal of polymer science. Part A, Polymer chemistry》2006,44(21):6449-6457
Size‐controllable polypyrrole (PPy)/multiwalled carbon nanotube (MWCNT) composites have been synthesized by in situ chemical oxidation polymerization directed by various concentrations of cationic surfactant cetyltrimethylammonium bromide (CTAB). Raman spectra, FTIR, SEM, and TEM were used to characterize their structure and morphology. These results showed that the composites are core (MWCNT)–shell (PPy) tubular structures with the thickness of the PPy layer in the range of 20–40 nm, depending on the concentration of CTAB. Raman and FTIR spectra of the composites are almost identical to those of PPy alone. The electrical conductivities of these composites are 1–2 orders of magnitude higher than those of PPy without MWCNTs. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6449–6457, 2006 相似文献
48.
Teruhiko Kai Yasunori Suma Shuichiro Ono Takeo Yamaguchi Shin‐ichi Nakao 《Journal of polymer science. Part A, Polymer chemistry》2006,44(2):846-856
We have investigated the effect of the surface state and surface treatment of the pores of an inorganic substrate on the plasma‐grafting behavior of pore‐filling‐type organic/inorganic composite membranes. Shirasu porous glass (SPG) was used as the inorganic substrate, and methyl acrylate was used as the grafting monomer. The grafting rate increased as the density of silanol on the SPG substrate increased. This result suggests that radicals are generated mainly at the silanol groups on the pore surface by plasma irradiation. The SPG substrates were treated with silane coupling agents used to control the mass of organic material bonded to the pore surface. The thickness of the grafted layer became thinner as the mass of organic material bonded to the pore surface of SPG increased. This decrease in the thickness of the grafted layer could be explained by the decrease in the penetration depth of vacuum ultraviolet rays contained in plasma having a wavelength of less than 160 nm that generated radicals in the pores of the substrate. The thickness of the grafted layer inside the SPG substrates could be controlled through the control of the mass of organic material bonded to the pore surface of the SPG substrate. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 846–856, 2006 相似文献
49.
B C Anusionwu 《Pramana》2006,67(2):319-330
The thermodynamic properties of Sb-Sn and In-Sn liquid alloys have been studied using the quasi-chemical model for compound
forming binary alloys and that for simple regular alloys. The concentration fluctuation S
cc(0) and the Warren-Cowley short-range order parameter (α
1) were determined for the whole concentration range at a temperature of 770 K. The surface tensions of these liquid alloys
were determined for the whole concentration range by using energetics determined from thermodynamic calculations. In all calculations,
In-Sn manifested properties very close to alloys of ideal mixing, while Sb-Sn showed properties that are asymmetric about
equiatomic composition. Our results suggest that a weak complex of the form SbSn2 could be present in the Sb-Sn alloy at a temperature of about 770 K. 相似文献
50.
The paper presents a theoretical-numerical hybrid method for determining the stresses distribution in composite laminates
containing a circular hole and subjected to uniaxial tensile loading. The method is based upon an appropriate corrective function
allowing a simple and rapid evaluation of stress distributions in a generic plate of finite width with a hole based on the
theoretical stresses distribution in an infinite plate with the same hole geometry and material. In order to verify the accuracy
of the method proposed, various numerical and experimental tests have been performed by considering different laminate lay-ups;
in particular, the experimental results have shown that a combined use of the method proposed and the well-know point-stress
criterion leads to reliable strength predictions for GFRP or CFRP laminates with a circular hole.
Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 43, No. 4, pp. 531–570, July–August, 2007. 相似文献