全文获取类型
收费全文 | 174229篇 |
免费 | 2428篇 |
国内免费 | 729篇 |
专业分类
化学 | 94347篇 |
晶体学 | 2498篇 |
力学 | 7701篇 |
综合类 | 7篇 |
数学 | 18193篇 |
物理学 | 54640篇 |
出版年
2021年 | 1021篇 |
2020年 | 1168篇 |
2019年 | 1181篇 |
2018年 | 1202篇 |
2017年 | 1205篇 |
2016年 | 2423篇 |
2015年 | 1982篇 |
2014年 | 2569篇 |
2013年 | 7884篇 |
2012年 | 6491篇 |
2011年 | 8209篇 |
2010年 | 4997篇 |
2009年 | 5134篇 |
2008年 | 7548篇 |
2007年 | 7549篇 |
2006年 | 7261篇 |
2005年 | 6771篇 |
2004年 | 6026篇 |
2003年 | 5186篇 |
2002年 | 5071篇 |
2001年 | 6081篇 |
2000年 | 4614篇 |
1999年 | 3514篇 |
1998年 | 2660篇 |
1997年 | 2657篇 |
1996年 | 2625篇 |
1995年 | 2314篇 |
1994年 | 2205篇 |
1993年 | 2052篇 |
1992年 | 2381篇 |
1991年 | 2344篇 |
1990年 | 2056篇 |
1989年 | 2036篇 |
1988年 | 2052篇 |
1987年 | 1976篇 |
1986年 | 1890篇 |
1985年 | 2801篇 |
1984年 | 2795篇 |
1983年 | 2238篇 |
1982年 | 2427篇 |
1981年 | 2307篇 |
1980年 | 2248篇 |
1979年 | 2195篇 |
1978年 | 2267篇 |
1977年 | 2212篇 |
1976年 | 2148篇 |
1975年 | 2133篇 |
1974年 | 2046篇 |
1973年 | 2126篇 |
1972年 | 1203篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Yang T. L. Kao C. L. Kuo C. E. Yeh H. C. Li W. J. Li H. T. Chen C. Y. 《Chemistry of Natural Compounds》2022,58(5):825-827
Chemistry of Natural Compounds - A novel bibenzyl derivative, hydrangchinenin (1), was isolated from the stems of Hydrangea chinensis Maxim. (Hydrangeaceae). Its structure was determined on the... 相似文献
2.
High Energy Chemistry - Modification of Polyvinylidene fluoride (PVDF) by radiation grafting is a research hotspot in recent years. In this study, the monomer 2-Hydroxyethyl methacrylate (HEMA) was... 相似文献
3.
In the pursuit to enlarge the library of polyimide materials for energy applications, new polyimide/MWCNTs composite films have been developed by MWCNTs-assisted polycondensation reaction of a hydroxyl and triphenylmethane-containing diamine with benzophenone tetracarboxylic dianhydride targeting to highlight their electrical storage capability as flexible electrodes in micro-supercapacitors (mSCs). The Fourier-transform infrared spectroscopy, proton nuclear magnetic resonance, UV–vis, fluorescence, and Raman spectroscopies were used to demonstrate the evolution of interfacial interactions between MWCNTs and the precursors (diamine monomer and intermediate polyamidic acid) and polyimide matrix that proved to be the origin of MWCNTs homogeneous dispersion. Thus, composite films incorporating 1, 3, 5, and 10 w.t.% MWCNTs were obtained and thoroughly investigated with regard to their morphology, mechanical behavior, thermal stability, and electrical conductivity. The electrochemical performance of these composites was first analyzed in a classical three-electrode cell by cyclic voltammetry and galvanostatic charge-discharge in both aqueous and organic electrolyte systems. By far, the best electrical storage capacity was obtained with the composite polyimide film containing 10% MWCNTs that was further used as both active material and current collector in a flexible symmetric mSC realized by a straightforward and low-cost procedure. In the attempt to better exploit the advantages of this composite film, it was layered with a graphite-containing paint and tested as an electrode in a flexible mSC, which provided satisfactory results. To our knowledge, this is the first report on the electrical charge storage capability of a polyimide/MWCNTs free-standing film as a flexible electrode in mSCs, which do not require time- and resource-consuming processing steps. 相似文献
4.
5.
M. Amar D. Andreucci R. Gianni C. Timofte 《Journal of Mathematical Analysis and Applications》2021,493(2):124533
We prove a well-posedness result for two pseudo-parabolic problems, which can be seen as two models for the same electrical conduction phenomenon in heterogeneous media, neglecting the magnetic field. One of the problems is the concentration limit of the other one, when the thickness of the dielectric inclusions goes to zero. The concentrated problem involves a transmission condition through interfaces, which is mediated by a suitable Laplace-Beltrami type equation. 相似文献
6.
7.
8.
Nonlinear Dynamics - In this article, the authors simulate and study dark and bright soliton solutions of 1D and 2D regularized long wave (RLW) models. The RLW model occurred in various fields such... 相似文献
9.
10.
A liquid dewetting method for the determination of the viscoelastic properties of ultrathin polymer films has been extended to study thickness effects on the properties of ultrathin polycarbonate (PC) films. PC films with film thicknesses ranging from 4 to 299 nm were placed on glycerol at temperatures from below the macroscopic glass transition temperature (Tg) to above it with the dewetting responses being monitored. It is found that the isothermal creep results for films of the same thickness, but dewetted at different temperatures can be superposed into one master curve, which is consistent with the fact of PC being a thermorheologically simple material. Furthermore, the results show that the Tg of PC thin films is thickness dependent, but the dependence is weaker than the results for freely standing films and similar to literature data for PC films supported on rigid substrates. It was also found that the rubbery plateau region for the PC films stiffens dramatically, but still less than what has been observed for freely standing polycarbonate films. The rubbery stiffening is discussed in terms of a recently reported model that relates macroscopic segmental dynamics with the stiffening. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1559–1566 相似文献