全文获取类型
收费全文 | 543篇 |
免费 | 158篇 |
国内免费 | 73篇 |
专业分类
化学 | 195篇 |
晶体学 | 12篇 |
力学 | 74篇 |
综合类 | 2篇 |
数学 | 45篇 |
物理学 | 446篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 18篇 |
2021年 | 8篇 |
2020年 | 13篇 |
2019年 | 5篇 |
2018年 | 10篇 |
2017年 | 25篇 |
2016年 | 21篇 |
2015年 | 25篇 |
2014年 | 28篇 |
2013年 | 48篇 |
2012年 | 53篇 |
2011年 | 42篇 |
2010年 | 39篇 |
2009年 | 45篇 |
2008年 | 38篇 |
2007年 | 41篇 |
2006年 | 43篇 |
2005年 | 33篇 |
2004年 | 29篇 |
2003年 | 26篇 |
2002年 | 26篇 |
2001年 | 17篇 |
2000年 | 25篇 |
1999年 | 18篇 |
1998年 | 11篇 |
1997年 | 28篇 |
1996年 | 14篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
排序方式: 共有774条查询结果,搜索用时 312 毫秒
51.
The interaction of 1-anilinonaphthalene-8-sulphonate (ANS) with cross-linked poly(N-vinyl-2-pyrrolidone) (CPVP) was studied
by the adsorption technique at different temperatures and at two different pH values. Analysis by the Scatchard method and
the study made in the presence of urea showed that the iceberg structure of water affects the sorption of ANS to CPVP, leading
to cooperativity. The observed Giles sorption isotherms at both the pH values were of theL-type which indicated the interaction of ANS in flat configuration with the binding site in CPVP. The sorption of ANS to CPVP
was enhanced considerably at acidic pH due to some structural factors which also resulted in multilayer sorption at this pH.
Comparison of binding of ANS to CPVP and to linear poly(N-vinyl-2-pyrrolidone) demonstrated the greater contribution of hydrophobic
interaction in CPVP than in the linear polymer. 相似文献
52.
Dr. Guanzhao Wu Yangxue Liu Hossein Rouh Liulei Ma Yao Tang Sai Zhang Peng Zhou Jia-Ying Wang Shengzhou Jin Dr. Daniel Unruh Dr. Kazimierz Surowiec Prof. Dr. Yanzhang Ma Prof. Dr. Guigen Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(30):8013-8020
The first asymmetric catalytic approach to multilayer 3D chirality has been achieved by using Suzuki-Miyaura cross-couplings. New chiral catalysts were designed and screened under various catalytic systems that proved chiral amide-phosphines to be more efficient ligands than other candidates. The multilayer 3D framework was unambiguously determined by X-ray structural analysis showing a parallel pattern of three layers consisting of top, middle and bottom aromatic rings. The X-ray structure of a catalyst complex, dichloride complex of Pd-phosphine amide, was obtained revealing an interesting asymmetric environment nearby the Pd metal center. Three rings of multilayer 3D products can be readily changed by varying aromatic ring-anchored starting materials. The resulting multilayer products displayed strong luminescence under UV irradiation and strong aggregation-induced emission (AIE). In the future, this work would benefit not only the field of asymmetric synthesis but also materials science, in particular polarized organic electronics, optoelectronics and photovoltaics. 相似文献
53.
54.
Construction of a highly stable covalently attached multilayer film electrode containing cobalt phthalocyanine was achieved by UV irradiation of ionic self-assembled multilayer films of diazo-resins (DAR) and cobalt phthalocyanine tetrasulfonic acid (CoTsPc) tetrasodium salt. The modified electrode had good potentiometric response to iodide ion. The potentiometric response was independent of the pH of the solution between pH 2.5 and 6.0, while it was dependent on the nature of the buffer media. The modified electrode had a linear dynamic range between 4.7×10−6 M and 0.1 M with a Nernstian slope of 58.8 mV per decade and a detection limit of 3.5×10−6 M in acetate buffer (0.1 M, pH 4.6). The modified electrode also exhibited a fast response, good stability and repeatability. 相似文献
55.
Mixed mode (MM) separation using a combination of MEKC and polyelectrolyte multilayer (PEM) coatings is herein reported for the separation of achiral and chiral analytes. Many analytes are difficult to separate by MEKC and PEM coatings alone. Therefore, the implementation of a MM separation provides several advantages for overcoming the limitations of these well‐established methods. In this study, it was observed that achiral separations using MEKC and PEM coatings individually resulted in partial resolution of eight very similar aryl ketones when the molecular micelle (sodium poly(N‐undecanoyl‐L ‐glycinate)) concentration was varied from 0.25 to 1.00% w/v and the bilayer number varied from 2 to 4. However, when MM separation was introduced, baseline resolution was achieved for all eight analytes. In the case of chiral separations, temazepam, aminoglutethimide, benzoin, benzoin methyl ether, and coumachlor were separated using the three separation techniques. For chiral separations, the chiral molecular micelle, sodium poly(N‐undecanoyl‐L ‐leucylvalinate), was employed at concentrations of 0.25–1.50% w/v for both MEKC and PEM coatings. Overall, the results revealed partial separation with MEKC and PEM coatings individually. However, MM separation enabled baseline separation of each chiral mixture. The separation of achiral and chiral compounds from different compound classes demonstrates the versatility of this MM approach. 相似文献
56.
A multilayer dielectric cylindrical mirror (MDCM) based on the one-dimensional omnidirectional reflection of a photonic crystal is presented. In this case, the refractive indices of the two materials are 1.6 (polystyrene) and 4.6 (tellurium), and the corresponding optimized thicknesses are 0.75a and 0.25a. A very high reflectance over a wide frequency range is observed. In this case, a is the lattice constant of the photonic crystal. In this band, the MDCM has good reflection and focal properties. Therefore, it is feasible to use the MDCM for integrated waveguide devices. As an example, an etched diffraction grating demultiplexer based on the MDCM is also proposed. Both the operational principle and design of the device are introduced. This provides a method for designing compact integrated waveguide devices. 相似文献
57.
Wenyu Ji Letian Zhang Mo Liu Jing Wang Guoqiang Liu Wenfa Xie Hanzhuang Zhang 《Current Applied Physics》2011,11(6):1410-1413
White top-emitting organic light-emitting devices (TEOLEDs) were fabricated on a glass substrate with metal/organic multilayer of (Ag/Alq3)2 (Alq3 is tris-(8-hydroxyquinoline) aluminum) as cathode. White TEOLEDs with high efficiency were obtained due to the microcavity effects. And the (Ag/Alq3)2 cathode, which adjusted the optical characteristics of the devices, played an important role. In addition, Alq3–Ag–Alq3 multilayer could work as a buffer layer, which would simplify the process of encapsulation for devices. We also calculated the electroluminescence spectrum of devices encapsulated with Al2O3 (150 nm) and Al2O3(75 nm)/ZrO2(75 nm). And the results indicated that the CIE coordinates is almost the same between with and without encapsulating. 相似文献
58.
Electric field-induced stress birefringence in layered composites PbZr1-xTixO3/Polycarbonate
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Electro-optical composites based on the product of electro-strictive and elasto-optical effects are developed.Layered composites of PbZr 1 x Ti x O 3 and polycarbonate are synthesised.Their electro-optical properties are studied.The nominal transverse electro-optical coefficient of the composite is observed to be about 3.6 times larger than that of LiNbO 3.Experiments and theoretical analyses show that the electro-optical effect of the composite has a strong ’size effect’.With the ratio of thickness/length decreasing or the width of elasto-optical phase increasing,the half-wave electric field intensity increases but the transverse electro-optical coefficient decreases for the layered composite. 相似文献
59.
60.
I.P. Coelho M.S. VasconcelosC.G. Bezerra 《Journal of magnetism and magnetic materials》2011,323(23):3162-3167
In this paper we investigated the influence of mirror symmetry on the transmission spectra of quasiperiodic magnonic multilayers arranged according to Fibonacci, Thue-Morse and double period quasiperiodic sequences. We consider that the multilayers composed of two simple cubic Heisenberg ferromagnets with bulk exchange constants JA and JB and spin quantum numbers SA and SB, respectively. The multilayer structure is surrounded by two semi-infinite slabs of a third Heisenberg ferromagnetic material with exchange constant JC and spin quantum number SC. For simplicity, the lattice constant has the same value a in each material, corresponding to epitaxial growth at the interfaces. The transfer matrix treatment was used for the exchange-dominated regime, taking into account the random phase approximation (RPA). Our numerical results illustrate the effects of mirror symmetry on (i) transmission spectra and (ii) transmission fingerprints. 相似文献