全文获取类型
收费全文 | 1765篇 |
免费 | 169篇 |
国内免费 | 311篇 |
专业分类
化学 | 1174篇 |
晶体学 | 19篇 |
力学 | 19篇 |
综合类 | 7篇 |
数学 | 21篇 |
物理学 | 1005篇 |
出版年
2024年 | 1篇 |
2023年 | 103篇 |
2022年 | 43篇 |
2021年 | 49篇 |
2020年 | 70篇 |
2019年 | 47篇 |
2018年 | 36篇 |
2017年 | 63篇 |
2016年 | 65篇 |
2015年 | 56篇 |
2014年 | 84篇 |
2013年 | 122篇 |
2012年 | 112篇 |
2011年 | 105篇 |
2010年 | 100篇 |
2009年 | 128篇 |
2008年 | 107篇 |
2007年 | 129篇 |
2006年 | 113篇 |
2005年 | 68篇 |
2004年 | 77篇 |
2003年 | 62篇 |
2002年 | 56篇 |
2001年 | 43篇 |
2000年 | 53篇 |
1999年 | 62篇 |
1998年 | 64篇 |
1997年 | 35篇 |
1996年 | 30篇 |
1995年 | 25篇 |
1994年 | 28篇 |
1993年 | 18篇 |
1992年 | 15篇 |
1991年 | 12篇 |
1990年 | 14篇 |
1989年 | 9篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1973年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有2245条查询结果,搜索用时 281 毫秒
91.
《Particuology》2016
Electrostatic phenomena are commonly observed in the processing of solids. However, the working mechanism of electrostatic charge generation for single granules and particularly, their electrostatic equilibria have not been properly understood. In this work, repeated-sliding charging experiments with single granules were investigated for their electrostatic generation particularly from the perspective of triboelectrification equilibrium. Factors including granule length-ratio, sliding face shape, sliding times, sliding area, sliding velocity, front-facing edge, and sliding-plate inclined-angle were found to have an obvious effect on granule charge generation. Length-ratio and sliding area have significant effects as the granules evolved toward an equilibrium state. Equilibrium charge is suggested as a variable expressing the charging propensity of the material. In addition, under the same working conditions, a semi-cylindrical granule generates greater charge than a rectangular granule. 相似文献
92.
J. Mark Parnis Kaitlynn A. King Matthew G. K. Thompson 《Journal of mass spectrometry : JMS》2013,48(11):1224-1231
The chemistry of ionized acetone:Ar mixtures under varied ionizing electron density conditions has been studied using matrix‐isolation techniques. Gaseous acetone diluted in excess argon gas was subjected to electron bombardment with 300 eV electrons at currents between 20 and 200 μA. Linear wire ‘pin’ and metal ‘plate’ electron collector geometries were employed, allowing a wide range of electron density conditions to be explored. The products of subsequent reaction processes were matrix isolated and analyzed by Fourier transform infrared absorption spectroscopy. Products included methane, ketene, 1‐propen‐2‐ol (the enol isomer of acetone), CO, HCO, ethane, ethane, acetylene and CCCO. Product absolute and relative yields varied with acetone number density, the choice of anode geometry and the rate of electron bombardment. The overall chemistry observed is rationalized in terms of mechanistic steps involving unimolecular cation decomposition, ion–molecule reactions, radical–radical reactions and dissociative recombination processes. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
93.
94.
《Journal of computational science》2014,5(4):590-596
A σ-hole is a region of diminished electronic density on the extension of a covalent bond to an atom. This region often exhibits a positive electrostatic potential, which allows attractive noncovalent interactions with negative sites. In this study, we have systematically examined the dependence of σ-hole potentials upon (a) the atom having the σ-hole, and (b) the remainder of the molecule. We demonstrate that not only relative electron-attracting powers need to be considered, but also relative charge capacities (or polarizabilities), and that other factors can also have significant roles. 相似文献
95.
In order to study the effect of epitaxial crystallization on charge transport in low-density polyethylene (LDPE) under multi-field coupling conditions, three typical epitaxial crystallizations, namely disorder (glass substrate), crossover (isotactic polypropylene substrate), and parallel (polytetrafluoroethylene substrate), were prepared and denoted as LD-G, LD-iPP, and LD-PT, respectively. Packet-like space charge through samples was analyzed by the pulsed electro-acoustic (PEA) method. It is shown that different microscopic surface morphologies appeared in the LDPE samples with different epitaxial crystallizations, which, however, do not change the crystalline structure of the bulk. Packet-like space charge phenomena were observed and the distortion field increased with the temperature which could be attributed to the larger amount of charge injection in a shorter period. The differences of the amount and injection rate of the space charge were explained and verified considering the typical chain alignment of epitaxial crystallization, which, in our opinions, contributes to the pass over of positive charge in LD-iPP samples. 相似文献
96.
Relaxation process of surface charge owing to dielectric barrier discharge (DBD) in “needle – air gap – polyethylene terephthalate film – plane” configuration is considered. Experimental data of the surface charge relaxation (SCR) are obtained by means of the rotating capacitive probe. Taking into account Gaussian radial distribution of accumulated charge density, effective surface and volume electrical conductivities of a barrier dielectric, phenomenological model of SCR for any dielectric thickness is proposed and exact solutions are obtained. The adequacy of the model is confirmed by the numerical computation. There is a good agreement between the experimental results and the model calculations. 相似文献
97.
98.
Gi-Seong Ryu 《Molecular Crystals and Liquid Crystals》2017,652(1):207-212
Most of the merit of organic thin film transistors (OTFTs) is that they can be manufactured using cost effective processes. However, expensive gold (Au) electrodes have usually been used as a source/drain (S/D), due to their benign energy level matching, high air stability, and easy patternability. In this article, we report a simple method for improving the charge injection from a low cost molybdenum (Mo) electrode to organic semiconductors in OTFTs by incorporating a dodecanoic acid (DA)–based self-assembled monolayer (SAM). The OTFT performance is remarkably improved when compared to the devices with a pristine Au electrode. The hole carrier mobilities (hole μFET) were ~0.13 (rr-P3HT), ~0.55 (PC12TV12T) and ~0.72 (P2100) cm2/V·sec. 相似文献
99.
100.
Macrocycles consisting of two tris(phenylene ethynylene) (or tri-PE) units connected via two flexible linkers adopt an ‘unfolded’ conformation that is converted into a folded conformation upon introducing intramolecular hydrogen bonding interaction. These foldable macrocycles are capable of forming inclusion charge transfer (CT) complex with electron-deficient small aromatics. 相似文献