全文获取类型
收费全文 | 2498篇 |
免费 | 124篇 |
国内免费 | 149篇 |
专业分类
化学 | 1299篇 |
晶体学 | 22篇 |
力学 | 98篇 |
综合类 | 6篇 |
数学 | 255篇 |
物理学 | 1091篇 |
出版年
2023年 | 29篇 |
2022年 | 29篇 |
2021年 | 29篇 |
2020年 | 33篇 |
2019年 | 81篇 |
2018年 | 56篇 |
2017年 | 43篇 |
2016年 | 66篇 |
2015年 | 38篇 |
2014年 | 96篇 |
2013年 | 194篇 |
2012年 | 112篇 |
2011年 | 97篇 |
2010年 | 92篇 |
2009年 | 163篇 |
2008年 | 197篇 |
2007年 | 196篇 |
2006年 | 181篇 |
2005年 | 149篇 |
2004年 | 147篇 |
2003年 | 71篇 |
2002年 | 61篇 |
2001年 | 43篇 |
2000年 | 51篇 |
1999年 | 45篇 |
1998年 | 40篇 |
1997年 | 37篇 |
1996年 | 21篇 |
1995年 | 24篇 |
1994年 | 19篇 |
1993年 | 41篇 |
1992年 | 14篇 |
1991年 | 12篇 |
1990年 | 15篇 |
1989年 | 12篇 |
1987年 | 6篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 13篇 |
1981年 | 38篇 |
1980年 | 31篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 15篇 |
1976年 | 18篇 |
1975年 | 11篇 |
1974年 | 19篇 |
1973年 | 14篇 |
1968年 | 4篇 |
排序方式: 共有2771条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Utilization of carbohydrates by radiation processing 总被引:2,自引:0,他引:2
Upgrading and utilization of carbohydrates such as chitosan, sodium alginate, carrageenan, cellulose, pectin have been investigated for recycling these bio-resources and reducing the environmental pollution. These carbohydrates were easily degraded by irradiation and various kinds of biological activities such as anti-microbial activity, promotion of plant growth, suppression of heavy metal stress, phytoalexins induction, etc. were induced. On the other hand, some carbohydrate derivatives, carboxymethylcellulose and carboxymethylstarch, could be crosslinked under certain radiation condition and produce the biodegradable hydrogel for medical and agricultural use. 相似文献
6.
7.
XPS measurement revealed that the original state of TiO2 was changed to Ti2O3 and TiO by ion bombardment. TiO2 decreased and Ti2O3 increased at the initial stage. TiO increased at a later stage than Ti2O3. Each of them saturated after enough sputtering time.A formulation was proposed in order to explain the change of XPS spectra for oxides as a function of ion sputtering time. This formulation was based on reaction equations that contain two reduction processes (from TiO2 to Ti2O3 and from Ti2O3 to TiO), and sputtering effects. Using four fitting parameters (two reduction coefficients, sputtering yield and information depth), the present formula was fitted to the experimental results. The fitting results agree satisfactorily with the experimental results. The calculation shows that the reduction coefficient from TiO2 to Ti2O3 is about ten times larger than that from Ti2O3 to TiO. This calculation predicts that surface composition of an oxide that is changed by ion bombardment will reach a different value depending on its bulk composition. Moreover, the present formulation can determine the chemical states of compounds changed by ion bombardment. 相似文献
8.
The electronic states of the Cr overlayers on TiO2(0 0 1) surfaces have been investigated using angle-resolved and resonant photoemission spectroscopy with synchrotron radiation. At lower coverages, Cr deposition on TiO2(0 0 1) creates two well separated in-gap emissions due to the formation of surface Ti3+ (3d1) ions and Cr3+ (3d3) ions. At higher coverages, the in-gap emission is developed into the 2-peak-structure emission of Cr 3d character. The corresponding state is considered to be of metallic nature from the viewpoint of the high ability of oxygen adsorption, but has no Fermi edge, indicating a possibility of forming small Cr clusters on TiO2(0 0 1) at this stage. 相似文献
9.
Closed series solution of electromagnetic scattering by an eccentric coated cylinder is achieved in matrix form. Diffracted field patterns are examined for an incident plane transverse magnetic (TM) wave. The solution is found by the classical separation of variables technique and the translational addition theorems. Wave transformation and orthogonality of the complex exponentials are employed to produce an infinite series. Numerical results are then shown by shortening the infinite series to a limited number of terms. Solutions are discussed for a dielectric or a metamaterial coating. 相似文献
10.
Those who have worked in the Royal Institution of Great Britain have, since its foundation in 1799, made significant contributions
to scientific knowledge, to its practical application, and to its communication to a wide variety of audiences. Such work
cannot be carried out in an architectural vacuum, and in this paper we examine how the buildings of the Royal Institution,
20 and 21 Albemarle Street in central London, have shaped the work undertaken within its walls and how, on a number of occasions,
the buildings have been reconfigured to take account of the evolving needs of scientific research and communication.
This paper is based on the Conservation Plan of the Royal Institution that we wrote during 2003. The Conservation Plan did
not examine the land owned by the Royal Institution to the north (i.e., 22 and 23 Albemarle Street; for this area see Richard Garnier, “Grafton Street, Mayfair,” Georgian Group Journal 13 (2003), 210–272), but it did discuss 18 and 19 Albemarle Street. In this paper we concentrate on the core Royal Institution
buildings at 20 and 21 Albemarle Street. Other studies of the relationship of architecture,space, and science include Crosbie
Smith and Jon Agar, ed., Making Space for Science: Territorial Themes in the Shaping of Knowledge (Basingstoke: Macmillan, 1997); Peter Galison and Emily Thompson, ed., The Architecture of Science (Cambridge, Mass.: MIT Press, 1999); and Sophie Forgan,“The architecture of science and the idea of a university,” Studies in History and Philosophy of Science 20 (1989), 405–434.
Frank A.J.L. James is Professor of the History of Science at the Royal Institution; he has written widely on the history of
nineteenth-century science in its social and cultural contexts and is editor of the Correspondence of Michael Faraday. He is President of the British Society for the History of Science. Anthony Peers is an Associate of Rodney Melville and
Partners where he works in the field of building conservation as an architectural historian. He is a Council member of the
Ancient Monument Society. 相似文献