全文获取类型
收费全文 | 1028篇 |
免费 | 47篇 |
国内免费 | 5篇 |
专业分类
化学 | 840篇 |
晶体学 | 7篇 |
力学 | 25篇 |
数学 | 46篇 |
物理学 | 162篇 |
出版年
2023年 | 2篇 |
2022年 | 11篇 |
2021年 | 22篇 |
2020年 | 18篇 |
2019年 | 19篇 |
2018年 | 13篇 |
2017年 | 14篇 |
2016年 | 32篇 |
2015年 | 27篇 |
2014年 | 27篇 |
2013年 | 73篇 |
2012年 | 76篇 |
2011年 | 96篇 |
2010年 | 57篇 |
2009年 | 55篇 |
2008年 | 91篇 |
2007年 | 75篇 |
2006年 | 81篇 |
2005年 | 62篇 |
2004年 | 40篇 |
2003年 | 35篇 |
2002年 | 30篇 |
2001年 | 6篇 |
2000年 | 17篇 |
1999年 | 5篇 |
1998年 | 9篇 |
1997年 | 10篇 |
1996年 | 10篇 |
1995年 | 10篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 2篇 |
1968年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有1080条查询结果,搜索用时 15 毫秒
71.
72.
Noise-limitations of the coherence imaging system based on the wavefront folding interferometer are studied. The signal-to-noise ratio SNR in two kinds of noise-limiting cases, the photon-noise-limit and the detector-noise-limit, is derived and are compared with the experimental results. The experimental demonstration is conducted using a wavefront folding interferometer and a single slit that provides the light source. An ensemble of ten sets of data are measured under the same conditions and the statistics of the retrieved images are computed from them. It is verified that the experimental results generally agree with the theoretical expectations. 相似文献
73.
Pawiga Thaweephan Scott Meng Grigori Sigalov Hyun Koo Kim Sung Ho Choi Thein Kyu 《Journal of Polymer Science.Polymer Physics》2001,39(14):1605-1615
Miscibility phase behavior in blends of poly(bromostyrene) with polystyrene (PS) has been investigated by means of time‐resolved light scattering, optical microscopy, and DSC. Cloud point phase diagrams of blends of conventional PS with poly‐(2‐bromostyrene) (P2BrS), poly‐(3‐bromostyrene), and poly‐(4‐bromostyrene) of comparable molecular weights were established by light scattering. Of particular interest is the fact that ortho, meta, and para substitutions in the styrenic aromatic rings of poly(bromostyrene) show profound effects on the composition–temperature phase diagrams of their blends with PS, exhibiting a lower critical‐solution temperature (LCST), an upper critical solution temperature (UCST), and combined LCST/UCST diagrams, respectively. Poly‐(2‐chlorostyrene) exhibits an LCST behavior very close to that of the P2BrS blend, suggesting that these types of halogen atoms may be inconsequential to phase behavior. A similar study has been extended to a PS blend containing commercial brominated PS (66 mol % bromine substitution) to determine what location of bromine substitution is crucial for miscibility enhancement in the flame‐retardant brominated PS blends. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1605–1615, 2001 相似文献
74.
75.
76.
Kyu Won Lee 《Solid State Communications》2005,136(2):63-66
We report the quasi-persistent photocurrent in the MEH-PPV conjugated polymer, induced by UV-irradiation in air. It is attributed to the irradiation-induced defects, which also act to accelerate its decay. 相似文献
77.
Kwati Leonard Junichi Kurawaki Katumitu Hayakawa Myint Thein Tun Yoshihumi Kusumoto 《Colloid and polymer science》2009,287(7):773-778
Laser irradiation of copper(II) tetrasulfonated phthalocyanine (CuTsPc) microcrystals in poor organic solvents such as methanol,
2-methyl-2-propanol, ethanol, tetrahydrofuran, and acetone has produced CuTsPc nanoparticles with 15–112 nm in diameter. Field
emission scanning electron microscopy (FESEM) images have shown the formation of CuTsPc nanoparticles in poor organic solvents
used in this work. The mean diameters of CuTsPc nanoparticles obtained from transmission electron microscopy (TEM) images
in methanol, 2-methyl-2-propanol, ethanol, tetrahydrofuran, and acetone were determined to be 26, 36, 35, 86, and 78 nm, respectively.
A correlation between the size of CuTsPc nanoparticles and a solvent polarity could be found in this work. 相似文献
78.
In Kyu Moon Masuki Kawamoto Tatsuo Wada 《Journal of polymer science. Part A, Polymer chemistry》2009,47(9):2434-2442
In the present study, a new (E)‐rich‐enyne π‐conjugated polymer containing a carbazole was designed and synthesized. Two different synthesis methods of poly[N‐(2‐ethylhexyl)‐3,6‐carbazolyleneethynylene‐(E)‐vinylene] (PCZEV) have been prepared from 3,6‐diethynyl‐9(2‐ethylhexyl)carbazole by using the palladium‐carbene‐catalyzed reaction and/or by using the organolanthanide‐catalyzed reaction leading to well‐defined polymer, and their general properties were studied. Compared to poly[N‐(2‐ethylhexyl)‐3,6‐carbazolyleneethynylene] (PCE), the UV‐vis absorption and photoluminescence of the PCZEV was red‐shifted, which indicates the extension of conjugation length. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2434–2442, 2009 相似文献
79.
Moonhor Ree Thein Kyu Richard S. Stein 《Journal of Polymer Science.Polymer Physics》1987,25(1):105-126
Small-angle light-scattering (SALS) patterns were obtained during melting and crystallization of blends of linear low-density polyethylene (LLDPE) with conventional low-density polyethylene (LDPE). Quantitative measurements of these SALS patterns using a two-dimensional optical multichannel analyzer apparatus (OMA2) indicate that the LLDPE which is miscible with the LDPE component in the molten state crystallizes first, forming volume-filling spherulites. The LDPE then crystallizes within the preformed spherulites. These findings are supported by optical microscopy studies showing that the blend samples were volume filled with one kind of the spherulites having a radius comparable to that of the pure LLDPE. The SALS intensity curve changes with composition of the blends in a manner that may be interpreted by considering the orientation of crystals within spherulites. It has been observed that the spherulites in the blend have more diffuse boundaries as the LDPE content increases. The lattice spacing and long spacings in blends were obtained by wide-angle and small-angle x-ray scattering, respectively. The SALS technique along with differential scanning calorimetry (DSC) is shown to be useful for determining the crystallization behavior of a crystallizable polymer blend system. 相似文献
80.
Hyebin Kang Taesong Lee Ukhwa Jin Kyu Tae Kim 《Proceedings of the Combustion Institute》2021,38(4):6035-6042
Self-excited combustion instabilities in a mesoscale multinozzle array, also referred to as a micromixer-type injector, have been experimentally investigated in a lean-premixed tunable combustor operating with preheated methane and air. The injector assembly consists of sixty identical swirl injectors of 6.5 mm inner diameter, which are evenly distributed across the combustor dump plane. Their flow paths are divided into two groups – inner and outer stages – to form radially stratified reactant stoichiometry for the control of self-excited instabilities. OH PLIF measurements of stable flames reveal that the presence of radial staging has a remarkable influence on stabilization mechanisms, reactant jet penetration/merging, and interactions between adjacent flame fronts. In an inner enrichment case, two outer (leaner) streams merge into a single jet structure, whereas the inner (richer) reactant jets penetrate far downstream without noticeable interactions between neighboring flames. The constructed stability map in the 〈?i, ?o〉 domain indicates that strong self-excited instabilities occur under even split and outer enrichment conditions at relatively high global equivalence ratios. This is attributed to large-scale flame surface deformation in the streamwise direction, as manifested by vigorous detachment/attachment movements. The use of the inner fuel staging method was found, however, to limit the growth of large-amplitude heat release rate fluctuations, because the center flames are securely anchored during the whole period of oscillation, giving rise to a moderate lateral motion. We demonstrate that the collective motion of sixty flames – rather than the individual local flame dynamics – play a central role in the development of limit cycle oscillations. This suggests that the distribution pattern of the injector array, in combination with the radial fuel staging scheme, is the key to the control of the instabilities. 相似文献