全文获取类型
收费全文 | 12022篇 |
免费 | 2252篇 |
国内免费 | 777篇 |
专业分类
化学 | 1776篇 |
晶体学 | 155篇 |
力学 | 2322篇 |
综合类 | 160篇 |
数学 | 5098篇 |
物理学 | 5540篇 |
出版年
2024年 | 22篇 |
2023年 | 108篇 |
2022年 | 218篇 |
2021年 | 221篇 |
2020年 | 327篇 |
2019年 | 274篇 |
2018年 | 247篇 |
2017年 | 362篇 |
2016年 | 396篇 |
2015年 | 306篇 |
2014年 | 493篇 |
2013年 | 816篇 |
2012年 | 592篇 |
2011年 | 593篇 |
2010年 | 566篇 |
2009年 | 675篇 |
2008年 | 676篇 |
2007年 | 856篇 |
2006年 | 821篇 |
2005年 | 735篇 |
2004年 | 655篇 |
2003年 | 701篇 |
2002年 | 581篇 |
2001年 | 533篇 |
2000年 | 486篇 |
1999年 | 440篇 |
1998年 | 359篇 |
1997年 | 333篇 |
1996年 | 231篇 |
1995年 | 192篇 |
1994年 | 152篇 |
1993年 | 158篇 |
1992年 | 118篇 |
1991年 | 97篇 |
1990年 | 87篇 |
1989年 | 49篇 |
1988年 | 60篇 |
1987年 | 52篇 |
1986年 | 47篇 |
1985年 | 65篇 |
1984年 | 53篇 |
1983年 | 26篇 |
1982年 | 35篇 |
1981年 | 48篇 |
1980年 | 26篇 |
1979年 | 35篇 |
1978年 | 42篇 |
1977年 | 33篇 |
1976年 | 20篇 |
1971年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 132 毫秒
111.
112.
Mingshu Chen 《Surface science》2006,600(19):L255
In this letter, atomically resolved scanning tunneling microscopic (STM) images obtained from monolayer SiO2/Mo(1 1 2) are presented. The results are consistent with a previously proposed structural model of isolated [SiO4] units based on vibrational features observed by high-resolution electron energy loss spectroscopy (HREELS) and infrared reflection-absorption spectroscopy (IRAS), and oxygen species identified by ultra-violet photoemission spectroscopy (UPS). These results are inconsistent with a structural model that assumes a two-dimensional (2-D) [Si-O-Si] network. These data illustrate that a metal substrate, although coated with an oxide thin layer, can be directly imaged at the atomic-scale with STM. 相似文献
113.
Howel Tong 《应用数学学报(英文版)》2002,18(2):177-184
Abstract I reflect upon the development of nonlinear time series analysis since 1990 by focusing on five majorareas of development. These areas include the interface between nonlinear time series analysis and chaos,thenonparametric/semiparametric approach,nonlinear state space modelling,financial time series and nonlinearmodelling of panels of time series. 相似文献
114.
On a nonlinear multigrid algorithm with primal relaxation for the image total variation minimisation
Digital image restoration has drawn much attention in the recent years and a lot of research has been done on effective variational partial differential equation models and their theoretical studies. However there remains an urgent need to develop fast and robust iterative solvers, as the underlying problem sizes are large. This paper proposes a fast multigrid method using primal relaxations. The basic primal relaxation is known to get stuck at a ‘local’ non-stationary minimum of the solution, which is usually believed to be ‘non-smooth’. Our idea is to utilize coarse level corrections, overcoming the deadlock of a basic primal relaxation scheme. A further refinement is to allow non-regular coarse levels to correct the solution, which helps to improve the multilevel method. Numerical experiments on both 1D and 2D images are presented. 相似文献
115.
Adsorption structures of the pentacene (C22H14) molecule on the clean Si(0 0 1)-2 × 1 surface were investigated by scanning tunneling microscopy (STM) in conjunction with density functional theory calculations and STM image simulations. The pentacene molecules were found to adsorb on four major sites and four minor sites. The adsorption structures of the pentacene molecules at the four major sites were determined by comparison between the experimental and the simulated STM images. Three out of the four theoretically identified adsorption structures are different from the previously proposed adsorption structures. They involve six to eight Si-C covalent chemical bonds. The adsorption energies of the major four structures are calculated to be in the range 67-128 kcal/mol. It was also found that the pentacene molecule hardly hopped on the surface when applying pulse bias voltages on the molecule, but was mostly decomposed. 相似文献
116.
本文介绍非线性方程转化直线性方程和多元线性回归法来分析近代物理实验中塞曼效应分裂干涉圆环多处选点测量的处理过程。 相似文献
117.
118.
The engineering of many modern electronic devices demands control over a crystal down to the thickness of a single layer of atoms—and future demands will be even more challenging. Such control is achieved by the method of crystal growth known as epitaxy, and that makes this method the subject of intense study. More than that, recent advances are revolutionizing our knowledge of how surfaces grow. In fact, growing surfaces show a beautifully rich variety of phenomena, many of which are only now beginning to be uncovered. In the past few years many surface imaging techniques have been used to give us a close look at how crystals grow—while they are growing. The purpose of this article will be to illustrate some of the ways real surfaces grow and change as revealed by some of the latest in situ microscopic imaging technologies.
It is often said that crystal growth is more of an art than a science. Here we will show that it is emphatically both. 相似文献
119.
Hui-Ling Li De-Jiang Qi Qing-Quan Jiang Shu-Zheng Yang 《International Journal of Theoretical Physics》2006,45(12):2428-2436
An extension of the Parikh-Wilczek's semi-classical quantum tunneling method, the tunneling radiation of the charged particle from a torus-like black hole is investigated. Difference from the uncharged mass-less particle, the geodesics of the charged massive particle tunneling from the black hole is not light-like, but determined by the phase velocity. The derived result shows that the tunneling rate depends on the emitted particle's energy and electric charge, and takes the same functional form as uncharged particle. It proves also that the exact emission spectrum is not strictly pure thermal, but is consistent with the underlying unitary theory.
PACS Numbers: 04.70.Dy, 97.60.Lf, 05.30.Ch. 相似文献
120.
A stage structured host-parasitoid model is derived and the equilibria studied. It is shown under what conditions the parasitoid controls an exponentially growing host in the sense that a coexistence equilibrium exists. Furthermore, for host populations whose inherent growth rate is not too large it is proved that in order to minimize the adult host equilibrium level it is necessary that the parasitoids attack only one of the larval stages. It is also proved in this case that the minimum adult host equilibrium level is attained when the parasitoids attack that larval stage which also maximizes the expected number of emerging adult parasitoid per larva at equilibrium. Numerical simulations tentatively indicate that the first conclusion remains in general valid for the model. However, numerical studies also show that it is not true in general that the optimal strategy will maximize the number of emerging adult parasitoid per larva at equilibrium. 相似文献