全文获取类型
收费全文 | 87601篇 |
免费 | 12670篇 |
国内免费 | 6861篇 |
专业分类
化学 | 84249篇 |
晶体学 | 2022篇 |
力学 | 1833篇 |
综合类 | 265篇 |
数学 | 9198篇 |
物理学 | 9565篇 |
出版年
2024年 | 28篇 |
2023年 | 293篇 |
2022年 | 1104篇 |
2021年 | 1138篇 |
2020年 | 1282篇 |
2019年 | 3005篇 |
2018年 | 2779篇 |
2017年 | 3346篇 |
2016年 | 3665篇 |
2015年 | 5804篇 |
2014年 | 5787篇 |
2013年 | 8798篇 |
2012年 | 6880篇 |
2011年 | 6738篇 |
2010年 | 5712篇 |
2009年 | 5793篇 |
2008年 | 6080篇 |
2007年 | 5436篇 |
2006年 | 5117篇 |
2005年 | 4789篇 |
2004年 | 4236篇 |
2003年 | 3657篇 |
2002年 | 4144篇 |
2001年 | 2375篇 |
2000年 | 2259篇 |
1999年 | 1268篇 |
1998年 | 710篇 |
1997年 | 631篇 |
1996年 | 546篇 |
1995年 | 568篇 |
1994年 | 505篇 |
1993年 | 459篇 |
1992年 | 421篇 |
1991年 | 307篇 |
1990年 | 197篇 |
1989年 | 223篇 |
1988年 | 178篇 |
1987年 | 113篇 |
1986年 | 99篇 |
1985年 | 88篇 |
1984年 | 112篇 |
1983年 | 32篇 |
1982年 | 57篇 |
1981年 | 84篇 |
1980年 | 71篇 |
1979年 | 56篇 |
1978年 | 46篇 |
1977年 | 30篇 |
1976年 | 21篇 |
1975年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Facile non‐lithographic route to highly aligned silica nanopatterns using unidirectionally aligned polystyrene‐block‐polydimethylsiloxane films
下载免费PDF全文
![点击此处可从《Journal of Polymer Science.Polymer Physics》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Zhe Qiang Maurice L. Wadley Bryan D. Vogt Kevin A. Cavicchi 《Journal of Polymer Science.Polymer Physics》2015,53(15):1058-1064
Thin films (monolayer and bilayer) of cylinder forming polystyrene‐block‐polydimethylsiloxane (PS‐b‐PDMS) were shear aligned by the swelling and deswelling of a crosslinked PDMS pad that was physically adhered to the film during solvent vapor annealing. The nanostructures formed by self‐assembly were exposed to ultraviolet‐ozone to partially oxidize the PDMS, followed by calcination in air at 500 °C. In this process, the PS segments were fully decomposed, while the PDMS yielded silica nanostructures. The highly aligned PDMS cylinders were thus deposited as silica nanolines on the silicon substrate. Using a bilayer film, the center‐to‐center distance of these features were effectively halved from 38 to 19 nm. Similarly, by sequential shear‐alignment of two distinct layers, a rhombic array of silica nanolines was fabricated. This methodology provides a facile route to fabricating complex topographically patterned nanostructures. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1058–1064 相似文献
72.
Pan Huang Dawen Xu Robert M. Reich Felix Kaiser Boping Liu Fritz E. Kühn 《Tetrahedron letters》2019,60(24):1574-1577
A first example of an Et2Zn mediated silylation of 1-aklynes is reported. A series of functional groups are tolerated in this reaction. Mechanistic studies support Zn alkynilides as intermediates in the reaction. This reaction protocol provides a practical method for the preparation of alkynylsilanes and expands the application of organometallic zinc in organic synthesis. 相似文献
73.
74.
75.
76.
G. Montero L. Gonzlez E. Flrez M. D. García A. Surez 《Numerical Linear Algebra with Applications》2002,9(3):239-247
Parallel preconditioners are presented for the solution of general linear systems of equations. The computation of these preconditioners is achieved by orthogonal projections related to the Frobenius inner product. So, minM∈??∥AM?I∥ F and matrix M0∈?? corresponding to this minimum (?? being any vectorial subspace of ??n(?)) are explicitly computed using accumulative formulae in order to reduce computational cost when subspace ?? is extended to another one containing it. Every step, the computation is carried out taking advantage of the previous one, what considerably reduces the amount of work. These general results are illustrated with the subspace of matrices M such that AM is symmetric. The main application is developed for the subspace of matrices with a given sparsity pattern which may be constructed iteratively by augmenting the set of non‐zero entries in each column. Finally, the effectiveness of the sparse preconditioners is illustrated with some numerical experiments. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
77.
Double Michael additions of lithium enolaie of 1,4-dioxaspiro[4.5]dec-6-en-8-one to four acrylates afforded bicyclo[2.2.2]octan-2-ones with high regio- and stereoselectivities in moderate yields. 相似文献
78.
设计合成了用以检测过渡金属离子的荧光化学敏感器体系,它们是由1,8-萘二酰亚胺为荧光团,多胺衍生物为金属离子受体组成.在室温下对其光物理性质的研究中发现,在没有加入过渡金属离子时,由于体系内存在有效的光诱导电子转移过程使得荧光团的荧光被淬灭.加入过渡金属离子后,金属离子受体中的氮原子和过渡金属离子之间的配位作用阻断了光诱导电子转移过程,体系的荧光增强.不同的金属离子受体表现出了和过渡金属离子不同的配位识别能力,并且通过荧光的变化传递出受体-金属离子作用的信息. 相似文献
79.
80.