全文获取类型
收费全文 | 86442篇 |
免费 | 1916篇 |
国内免费 | 1624篇 |
专业分类
化学 | 30551篇 |
晶体学 | 924篇 |
力学 | 7098篇 |
综合类 | 107篇 |
数学 | 32889篇 |
物理学 | 18413篇 |
出版年
2023年 | 154篇 |
2022年 | 327篇 |
2021年 | 328篇 |
2020年 | 356篇 |
2019年 | 429篇 |
2018年 | 10656篇 |
2017年 | 10488篇 |
2016年 | 6433篇 |
2015年 | 1325篇 |
2014年 | 873篇 |
2013年 | 1011篇 |
2012年 | 4607篇 |
2011年 | 11278篇 |
2010年 | 6254篇 |
2009年 | 6646篇 |
2008年 | 7257篇 |
2007年 | 9328篇 |
2006年 | 745篇 |
2005年 | 1698篇 |
2004年 | 1874篇 |
2003年 | 2221篇 |
2002年 | 1247篇 |
2001年 | 439篇 |
2000年 | 425篇 |
1999年 | 296篇 |
1998年 | 299篇 |
1997年 | 232篇 |
1996年 | 303篇 |
1995年 | 212篇 |
1994年 | 150篇 |
1993年 | 160篇 |
1992年 | 111篇 |
1991年 | 105篇 |
1990年 | 88篇 |
1989年 | 83篇 |
1988年 | 90篇 |
1987年 | 76篇 |
1986年 | 76篇 |
1985年 | 70篇 |
1984年 | 51篇 |
1983年 | 45篇 |
1982年 | 44篇 |
1981年 | 43篇 |
1980年 | 48篇 |
1979年 | 45篇 |
1914年 | 45篇 |
1913年 | 40篇 |
1912年 | 40篇 |
1909年 | 41篇 |
1908年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Zenon Moszner 《Aequationes Mathematicae》2018,92(4):617-625
We give the form of the output function in Ginsburg’s machine in which the input and output dictionaries are abelian groups and the transition function is of a special form. 相似文献
22.
23.
Facile fabrication of fast recyclable and multiple self‐healing epoxy materials through diels‐alder adduct cross‐linker
下载免费PDF全文
![点击此处可从《Journal of polymer science. Part A, Polymer chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xiao Kuang Guoming Liu Xia Dong Xianggui Liu Jianjun Xu Dujin Wang 《Journal of polymer science. Part A, Polymer chemistry》2015,53(18):2094-2103
A reversibly cross‐linked epoxy resin with efficient reprocessing and intrinsic self‐healing was prepared from a diamine Diels‐Alder (DA) adduct cross‐linker and a commercial epoxy oligomer. The newly synthesized diamine cross‐linker, comprising a DA adduct of furan and maleimide moieties, can cure epoxy monomer/oligomer with thermal reversibility. The reversible transition between cross‐linked state and linear architecture endows the cured epoxy with rapid recyclability and repeated healability. The reversibly cross‐linked epoxy fundamentally behaves as typical thermosets at ambient conditions yet can be fast reprocessed at elevated temperature like thermoplastics. As a potential reversible adhesive, the epoxy polymer with adhesive strength values about 3 MPa showed full recovery after repeated fracture‐thermal healing processes. The methodology explored in this contribution provides new insights in modification of conventional engineering plastics as functional materials. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2094–2103 相似文献
24.
Understanding and control of the surface properties such as molecular orientations are of great importance in numerous applications of ionic liquids. However, there remain discrepancies among the previous experimental and theoretical studies on the surface orientation and structures of room temperature ionic liquids(RTIL) systems. In this article, the orientation of 1-butyl-3-methylimidazolium([bmin]) cation at the air/liquid interface of a characteristic RTIL, 1-butyl-3-methylimidazolium hexafluorophosphate([bmim][PF6]), was investigated by the sum frequency generation vibrational spectroscopy(SFG-VS). Detailed polarization and experimental configuration analyses of the SFG-VS spectra showed the possibility of a small spectral splitting in the CH3 symmetric stretching region, which can be further attributed to the probable existence of multiple orientations for the interfacial [bmim] cations. In addition, the(N)–CH3 vibrations were absent, ruling out the prediction by several recent molecular dynamics simulations which state that portions of the [bmim] cations orient with a standing-up(N)–CH3 group at the ionic liquid surface. Hence, new realistic theoretical models have to be developed to reflect the complex nature of the ionic liquid surface. 相似文献
25.
26.
27.
28.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films
were investigated using a number of techniques. A high saturation magnetic induction up to B
s
= 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed,
which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of
the composition.
The text was submitted by the authors in English. 相似文献
29.
A forecasting model is developed for the number of daily applications for loans at a financial services telephone call centre. The purpose of the forecasts and the associated prediction intervals is to provide effective staffing policies within the call centre. The model building process is constrained by the availability of only 2 years and 7 months of data. The distinctive feature of the data is that demand is driven in the main by advertising. The analysis given focuses on applications stimulated by press advertising. Unlike previous analyses of broadly similar data, where ARIMA models were used, a model with a dynamic level, multiplicative calendar effects and a multiplicative advertising response is developed and shown to be effective. 相似文献
30.
Chee Sing Yap 《The Journal of the Operational Research Society》1989,40(7):649-658
This paper describes three case studies which investigated issues relating to the implementation and management of advanced information technology. The benefits derived from information technology were found to vary from one organization to another. These studies provide further evidence to support earlier research findings that senior management has an important role to play in the effective exploitation of information technology, and that the investment approach taken by an organization has a significant effect on the development of computer-based information systems. The effectiveness of a system depends not only on applying the appropriate technology, but also on how successfully technical and behavioural issues are resolved. 相似文献