全文获取类型
收费全文 | 1732篇 |
免费 | 264篇 |
国内免费 | 170篇 |
专业分类
化学 | 1272篇 |
晶体学 | 20篇 |
力学 | 73篇 |
综合类 | 6篇 |
数学 | 177篇 |
物理学 | 618篇 |
出版年
2024年 | 2篇 |
2023年 | 41篇 |
2022年 | 75篇 |
2021年 | 74篇 |
2020年 | 85篇 |
2019年 | 77篇 |
2018年 | 60篇 |
2017年 | 59篇 |
2016年 | 84篇 |
2015年 | 93篇 |
2014年 | 104篇 |
2013年 | 125篇 |
2012年 | 167篇 |
2011年 | 186篇 |
2010年 | 111篇 |
2009年 | 96篇 |
2008年 | 102篇 |
2007年 | 99篇 |
2006年 | 85篇 |
2005年 | 69篇 |
2004年 | 67篇 |
2003年 | 36篇 |
2002年 | 32篇 |
2001年 | 10篇 |
2000年 | 24篇 |
1999年 | 29篇 |
1998年 | 31篇 |
1997年 | 21篇 |
1996年 | 25篇 |
1995年 | 17篇 |
1994年 | 16篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 12篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有2166条查询结果,搜索用时 0 毫秒
61.
62.
Xiaoxiao Zheng Rongli Zhai Zihao Zhang Baoqing Zhang Jiangwei Liu Aamir Razaq Muhammad Ashfaq Ahmad Rizwan Raza Muhammad Saleem Syed Rizwan Syed Hassan Mujtaba Jafri Hu Li Raffaello Papadakis 《Molecules (Basel, Switzerland)》2022,27(6)
Composite materials and their applications constitute a hot field of research nowadays due to the fact that they comprise a combination of the unique properties of each component of which they consist. Very often, they exhibit better performance and properties compared to their combined building blocks. Graphene oxide (GO), as the most widely used derivative of graphene, has attracted widespread attention because of its excellent properties. Abundant oxygen-containing functional groups on GO can provide various reactive sites for chemical modification or functionalization of GO, which in turn can be used to develop novel GO-based composites. This review outlines the most recent advances in the field of novel dyes and pigments encompassing GO as a key ingredient or as an important cofactor. The interactions of graphene with other materials/compounds are highlighted. The special structure and unique properties of GO have a great effect on the performance of fabricated hybrid dyes and pigments by enhancing the color performance of dyes, the anticorrosion properties of pigments, the viscosity and rheology of inks, etc., which further expands the applications of dyes and pigments in dyeing, optical elements, solar-thermal energy storage, sensing, coatings, and microelectronics devices. Finally, challenges in the current development as well as the future prospects of GO-based dyes and pigments are also discussed. This review provides a reference for the further exploration of novel dyes and pigments. 相似文献
63.
The transport properties and magnetoresistance of electron-doped manganate / insulator composites (La0.8Te0.2MnO3)1 - x/(ZrO2)x (x=0, 0.3, and 0.5) are investigated. It is found that the metal-insulator transition temperature of this system shifts to a lower value as the ZrO2 content increases. The introduction of ZrO2 enhances both the domain scattering and electron relative scattering in the metal transport region. In the adiabatic small polaron hopping transport region, the thermal activation energy seems invariable regardless of the ZrO2 content. The application of a magnetic field promotes the charge transportation capabilities of the composites, and the magnetoresistance is enhanced with an increase of the ZrO2 content. This could be attributed to the more remarkable modification effect of magnetic field on ordering degree in the composites than in pure La0.8Te0.2MnO3. 相似文献
64.
In this work, characteristics of microcavity top-emitting red organic light-emitting device (TEROLED) having metallic electrodes had been examined. The TEOLED shows the higher efficiency in comparison with that of the bottom OLED. However, color variation with the increasing view angles is also observed. For the purpose of diminishing the blue-shift of resonant wavelength (RW) in the device with increasing view angle, the effect of out-coupling layer on the emission properties of the TEOLED is discussed in detail. Finally, the out-coupling layer was introduced in theory without sacrificing the efficiency through precise optical simulation. 相似文献
65.
本文主要研究了介质填充微波部件微放电随时间演变的过程,重点分析了介质微波部件微放电自熄灭机理.以介质部分填充平行平板传输线为研究对象,忽略空间电荷效应,采用自主研发粒子模拟软件模拟微放电过程,并将模拟结果与金属微波部件结果进行对比.结果表明,在一定功率下,金属微放电过程中电子数目呈指数形式增长,而介质微放电过程经历初始电子倍增后发生自熄灭现象,同时发现在电子数目即将下降为0时,介质表面的平均二次电子发射系数大于1或约等于1.另外,在上述模拟结果的基础上对微放电过程中介质表面积累电荷问题进一步分析,模拟结果表明,如果持续向微波部件内注入电子,介质表面的平均二次电子发射系数最终都约等于1.所得结论对研究复杂介质填充微波部件微放电的机理具有一定的理论指导价值. 相似文献
66.
Yuguo Li Ruiqin Peng Xianwu Xiu Xuelei Zheng Xiaosen Zhang Guannan Zhai 《Superlattices and Microstructures》2011,50(5):511-516
Tin oxide (SnO2) nanoparticles were fabricated by evaporation of Sn powers at 1000 °C in air pressure. The as-deposited SnO2 particles were single crystal structure, which were mostly spherical shape, the diameter of particles was ranging from 200 to 600 nm. The photoluminescence (PL) spectrum showed that a sharp emission peak at around 393 nm with the excitation wavelength at 325 nm, which suggested possible applications in nanoscaled optoelectronic devices. It was also found that the holding time affects the morphology of the products. The formation mechanism of SnO2 particles was discussed. 相似文献
67.
Zhaowei Tian Shuying Zhai Zhifeng Weng 《Journal of Applied Analysis & Computation》2020,10(3):904-919
In this paper, three compact difference schemes for the time-fractional Black-Scholes model governing European option pricing are presented. Firstly, in order to obtain the fourth-order accuracy in space by applying the Pad\''{e} approximation, we eliminate the convection term of the B-S equation by an exponential transformation. Then the time fractional derivative is approximated by $L1$ formula, $L2 - 1_\sigma$ formula and $L1 - 2$ formula respectively, and three compact difference schemes with oders $O(\Delta t^{2-\alpha}+h ^4)$, $O(\Delta t^{2}+h ^4)$ and $O(\Delta t^{3-\alpha}+h ^4)$ are constructed. Finally, numerical example is carried out to verify the accuracy and effectiveness of proposed methods, and the comparisons of various schemes are given. The paper also provides numerical studies including the effect of fractional orders and the effect of different parameters on option price in time-fractional B-S model. 相似文献
68.
To solve the problem of organic-inorganic light conductive composite interface features, transparent resin and cement matrix were used as carriers to further study features of the organic-inorganic interface formed by transparent resin and cement matrix and the interface modification of the coupling agent. The bond strength, micro-hardness, microstructure and surface morphology of a resin light conductive cementitious materials (RLCCM) interface were evaluated by tests of tensile and oblique shear, micro-hardness, environmental scanning electron microscopy, and atomic force microscope. The results show that the silane A-151 and aluminate coupling agent could significantly improve interface bond properties of RLCCM. At 7 d, the interface tensile bond strength of the silane A-151 and aluminate coupling agent increased by 117 and 105%, respectively. At 28 d, strength on average increased by 73%. At 7 d, interface shear strength the silane A-151 and aluminate coupling agent of 45° increased by 43 and 53%, respectively, At 28 d, strength on average increased by 40%. The transparent resin performance weakened region thickness up to 100 μm; the hardness of the transparent resin in the transition region was increased by 19.6 and 39.9%, respectively. Silane coupling agent A-151 and cement hydration products formed flat spherical particles with diameter of approximately 78 nm, and these particles mosaicked and fused in the surface of the hydrate; therefore, the surface became denser and smoother. 相似文献
69.
In this report, we demonstrate the efficient generation of collinearly propagating photon pairs in a bulk periodically poled potassium titanyl phosphate pumped by a cw laser. The detected coincidence counts are more than 7400/s with 3.58 mW pump power in a Hanbury-Brown-Twiss-type experiment. The estimated photon pair production rate is about 0.73 MHz/mW. This is very promising for some applications, such as quantum key distribution, proof of the Bell-inequality, preparation of single photon states in broadband wave packets, Franson-type interference and so on. 相似文献
70.
Canik JM Anderson DT Anderson FS Likin KM Talmadge JN Zhai K 《Physical review letters》2007,98(8):085002
Differences in the electron particle and thermal transport are reported between plasmas produced in a quasihelically symmetric (QHS) magnetic field and a configuration with the symmetry broken. The thermal diffusivity is reduced in the QHS configuration, resulting in higher electron temperatures than in the nonsymmetric configuration for a fixed power input. The density profile in QHS plasmas is centrally peaked, and in the nonsymmetric configuration the core density profile is hollow. The hollow profile is due to neoclassical thermodiffusion, which is reduced in the QHS configuration. 相似文献