全文获取类型
| 收费全文 | 3520篇 |
| 免费 | 355篇 |
| 国内免费 | 87篇 |
专业分类
| 化学 | 1335篇 |
| 晶体学 | 62篇 |
| 力学 | 556篇 |
| 综合类 | 17篇 |
| 数学 | 266篇 |
| 物理学 | 1726篇 |
出版年
| 2025年 | 10篇 |
| 2024年 | 58篇 |
| 2023年 | 68篇 |
| 2022年 | 144篇 |
| 2021年 | 150篇 |
| 2020年 | 178篇 |
| 2019年 | 148篇 |
| 2018年 | 131篇 |
| 2017年 | 132篇 |
| 2016年 | 170篇 |
| 2015年 | 145篇 |
| 2014年 | 152篇 |
| 2013年 | 292篇 |
| 2012年 | 211篇 |
| 2011年 | 196篇 |
| 2010年 | 149篇 |
| 2009年 | 171篇 |
| 2008年 | 169篇 |
| 2007年 | 173篇 |
| 2006年 | 158篇 |
| 2005年 | 111篇 |
| 2004年 | 126篇 |
| 2003年 | 107篇 |
| 2002年 | 84篇 |
| 2001年 | 76篇 |
| 2000年 | 73篇 |
| 1999年 | 61篇 |
| 1998年 | 56篇 |
| 1997年 | 56篇 |
| 1996年 | 37篇 |
| 1995年 | 23篇 |
| 1994年 | 29篇 |
| 1993年 | 15篇 |
| 1992年 | 15篇 |
| 1991年 | 12篇 |
| 1990年 | 13篇 |
| 1989年 | 13篇 |
| 1988年 | 6篇 |
| 1987年 | 9篇 |
| 1986年 | 6篇 |
| 1985年 | 4篇 |
| 1984年 | 7篇 |
| 1983年 | 2篇 |
| 1982年 | 3篇 |
| 1981年 | 3篇 |
| 1976年 | 1篇 |
| 1975年 | 1篇 |
| 1973年 | 2篇 |
| 1971年 | 1篇 |
| 1957年 | 1篇 |
排序方式： 共有3962条查询结果，搜索用时 15 毫秒
101.
We generalize previous stochastic classical trajectory-ghost atom calculations for describing palladium deposition onto the Ni(111) surface between 0.1 and 0.5 monolayers. The growth evolves through two-dimensional islands. The islands are formed following the downward funneling mechanism. Surface temperature does not affect the island growth. 相似文献
102.
103.
用图形计算器和CBL系统测量物体间的静摩擦力 总被引：1，自引：0，他引：1
介绍图形计算器。CBL及力传感器。并用于测量两物体同的最大静摩擦力。 相似文献
104.
A.V. Prokofiev F. Büllesfeld W. Assmus H. Schwenk D. Wichert U. Löw B. Lüthi 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):313-316
Experimental results on magnetic resonance (ESR) and magnetic susceptibility are given for single crystalline (VO)2P2O7. The crystal growth procedure is briefly discussed. The susceptibility is interpreted numerically using a model with alternating
spin chains. We determine J
=51 K and . Furthermore we find a spin gap of meV from our ESR measurements. Using elastic constants no indication of a phase transition forcing the dimerization is seen
below 300 K.
Received: 22 December 1997 / Accepted: 17 March 1998 相似文献
105.
Molecular dynamics simulations have been extensively carried out to study glass transition of polymers for over 20 years, in which a central but still open question is how to quickly and reliably determine the glass transition temperature (Tg). To address this issue, the two “moderate big” bulk model systems comprised of the mono‐disperse isotactic or syndiotactic poly(methyl methacrylate) (iPMMA, sPMMA) chains have been separately simulated with the chemically specific coarse‐grained potentials. The model systems are first equilibrated at an enough high temperature and then cooled to an enough low temperature with three different rates. It is demonstrated that the densities and non‐bonded interaction energies qualitatively reveal glass transition whereas the reorientation functions of bond vectors quantitatively locate the Tg. Despite all, consistent result is yielded that sPMMA exhibits a higher Tg than iPMMA, which is in good agreement with the experimental observation. More importantly, the tacticity effects can be well dictated by the activation energy for the fast relaxation mode identified in the rubbery domain, which paves the way for quick assessment of polymer Tg. 相似文献
106.
Oana‐Maria Manta Radu Bala Roman Murzac Mihaela Ulmeanu Cristian Vasile Doicin 《Macromolecular Symposia》2020,389(1)
The aim of this article is to analyze the behavior of baffle solution assembled on a pump module inside an automotive fuel tank. The originality comes from the baffle design which is adapted to a serial life tank definition to decrease the slosh noise impact generated by over storage of kinetic energy. The hypothesis that stays at the basis of the static analysis is to evaluate the deformation and the yielding strength considering a calculated maximum possible theoretical force existent in the fuel tank. The added value of this study is to identify the limitations of the technical solution to decide if design modifications for further studies should be considered for physical tests. 相似文献
107.
Dr. Yuan Liu Dr. Jin-Cheng Liu Teng-Hao Li Zeng-Hui Duan Dr. Tian-Yu Zhang Ming Yan Dr. Wan-Lu Li Prof. Dr. Hai Xiao Prof. Dr. Yang-Gang Wang Prof. Dr. Chun-Ran Chang Prof. Dr. Jun Li 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(42):18745-18749
The direct, nonoxidative conversion of methane on a silica-confined single-atom iron catalyst is a landmark discovery in catalysis, but the proposed gas-phase reaction mechanism is still open to discussion. Here, we report a surface reaction mechanism by computational modeling and simulations. The activation of methane occurs at the single iron site, whereas the dissociated methyl disfavors desorption into gas phase under the reactive conditions. In contrast, the dissociated methyl prefers transferring to adjacent carbon sites of the active center (Fe1©SiC2), followed by C−C coupling and hydrogen transfer to produce the main product (ethylene) via a key −CH−CH2 intermediate. We find a quasi Mars–van Krevelen (quasi-MvK) surface reaction mechanism involving extracting and refilling the surface carbon atoms for the nonoxidative conversion of methane on Fe1©SiO2 and this surface process is identified to be more plausible than the alternative gas-phase reaction mechanism. 相似文献
108.
Chun-Dong Xue Zhong-Ping Sun Yong-Jiang Li Jian-Feng Chen Bo Liu Kai-Rong Qin 《Electrophoresis》2020,41(10-11):909-916
In the present study, we numerically demonstrate an approach for separation of micro and sub-micro diamagnetic particles in dual ferrofluid streams based on negative magnetophoresis. The dual streams are constructed by an intermediate sheath flow, after which the negative magnetophoretic force induced by an array of permanent magnets dominates the separation of diamagnetic particles. A simple and efficient numerical model is developed to calculate the motions of particles under the action of magnetic field and flow field. Effects of the average flow velocity, the ratio of sheath fluid flow to sample fluid flow, the number of the magnet pair as well as the position of magnet pair are investigated. The optimal parametric condition for complete separation is obtained through the parametric analysis, and the separation principle is further elucidated by the force analysis. The separation of smaller micro and sub-micro diamagnetic particles is finally demonstrated. This study provides an insight into the negative magnetophoretic phenomenon and guides the fabrication of feasible, low-cost diagnostic devices for sub-micro particle separation. 相似文献
109.
Directing the self-assembly of organic building blocks with 2D templates has been a promising method to create molecular superstructures having unique physicochemical properties. In this work the on-surface self-assembly of simple ditopic functional molecules confined inside periodic nanotemplates was modeled by means of the lattice Monte Carlo simulation method. Two types of confinement, that is honeycomb porous networks and parallel grooves of controlled diameter and width were used in the calculations. Additionally, the effect of (pro)chirality of the adsorbing molecules on the outcome of the templated self-assembly was examined. To that end, enantiopure and racemic assemblies were studied and the resulting structures were identified and classified. The obtained findings demonstrated that suitable tuning of the structural parameters of the templates enables directing the self-assembly towards linear and cyclic aggregates with controlled size. Moreover, chiral resolution of the molecular conformers using honeycomb networks with adjusted pore size was found possible. Our theoretical predictions can be helpful in designing structured surfaces to direct self-assembly and polymerization of organic functional building blocks. 相似文献
110.
Realizing spatiotemporal patterns out of a chemical reaction diffusion system remains an experimental challenge owing to the difficulty in overcoming the stringent condition of diffusion driven instability. Herein, by considering the spatially extended Gray-Scott model system, we have investigated how the cross diffusivities of the reactants involved influence the nature and dynamics of spatiotemporal patterns. Our study unravels that in absence of diffusion driven instability, spatially inhomogeneous patterns can be obtained for the Gray-Scott model system, and unstable time dependent patterns can be stabilized just by adjusting cross diffusivities of the reactants. Interestingly, the effect of cross diffusion in presence of the diffusion driven instability can differentially alter the speed of pattern formation, and potentially modify the nature of the spatiotemporal patterns obtained under different parametric conditions. Experimental verification of our findings may allow us to observe spatiotemporal patterns beyond the regime of classical Turing instability. 相似文献