全文获取类型
收费全文 | 73033篇 |
免费 | 10694篇 |
国内免费 | 7582篇 |
专业分类
化学 | 49942篇 |
晶体学 | 711篇 |
力学 | 4837篇 |
综合类 | 583篇 |
数学 | 9122篇 |
物理学 | 26114篇 |
出版年
2024年 | 144篇 |
2023年 | 1417篇 |
2022年 | 1759篇 |
2021年 | 2303篇 |
2020年 | 2655篇 |
2019年 | 2533篇 |
2018年 | 2245篇 |
2017年 | 2034篇 |
2016年 | 3070篇 |
2015年 | 3155篇 |
2014年 | 3771篇 |
2013年 | 5054篇 |
2012年 | 6190篇 |
2011年 | 6418篇 |
2010年 | 4436篇 |
2009年 | 4396篇 |
2008年 | 4551篇 |
2007年 | 4111篇 |
2006年 | 3870篇 |
2005年 | 3358篇 |
2004年 | 2702篇 |
2003年 | 2164篇 |
2002年 | 1918篇 |
2001年 | 1695篇 |
2000年 | 1564篇 |
1999年 | 1663篇 |
1998年 | 1395篇 |
1997年 | 1221篇 |
1996年 | 1304篇 |
1995年 | 1103篇 |
1994年 | 1039篇 |
1993年 | 903篇 |
1992年 | 799篇 |
1991年 | 690篇 |
1990年 | 578篇 |
1989年 | 487篇 |
1988年 | 374篇 |
1987年 | 362篇 |
1986年 | 308篇 |
1985年 | 301篇 |
1984年 | 203篇 |
1983年 | 181篇 |
1982年 | 148篇 |
1981年 | 113篇 |
1980年 | 82篇 |
1978年 | 56篇 |
1977年 | 53篇 |
1976年 | 50篇 |
1975年 | 57篇 |
1973年 | 58篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
You‐Liang Zhao Chuan‐Fu Chen Fu Xi 《Journal of polymer science. Part A, Polymer chemistry》2003,41(14):2156-2165
The atom transfer radical copolymerization of N‐substituted maleimides such as N‐phenylmaleimide (PhMI), N‐cyclohexylmaleimide (ChMI), and N‐butylmaleimide (NBMI) with styrene initiated with dendritic polyarylether 2‐bromoisobutyrates in an ionic liquid, 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim][PF6]), at room temperature and anisole at 110 °C was investigated. The dendritic‐linear block copolymers obtained in ionic liquid possessed well‐defined molecular weight and low polydispersity (1.05 < Mw/Mn < 1.32) and could be used as a macroinitiator for chain‐extension polymerization, suggesting the living nature of the reaction system. The ionic liquids containing catalyst could be recycled in the atom transfer radical polymerization systems without further treatment. Compared with polymerization conducted in anisole, the polymerization in ionic liquid had a stronger tendency for alternation. The tendency for alternation decreased in the order PhMI > NBMI > ChMI in [bmim][PF6] and PhMI > ChMI > NBMI in anisole. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2156–2165, 2003 相似文献
182.
183.
184.
185.
A novel and simple two-frequency Brillouin fiber laser is presented. It is based on a fiber Fabry-Perot cavity with fiber Bragg gratings as reflectors. The model of stimulated Brillouin scattering in fiber grating-based Fabry-Perot resonator is investigated. The laser allows conversion efficiency of close to 100% and suppresses the higher-order Stokes waves. The theoretical prediction is presented and the experimental demonstration is realized. 相似文献
186.
187.
Ping Li Fei Rong Yibing Xie Van Hu Chunwei Yuan 《Journal of Analytical Chemistry》2004,59(10):939-944
S-naproxen imprinted polymer was prepared with acrylamide as a functional monomer, 1,4-butanediyl diacrylate as a new kind of crossliner, and 2,4,6-trimethylbenzoylphenyl-phosphinic acid ethyl ester as photoinitiator. Their UV and IR spectra were applied to study the interactions between the template and the monomer. Binding experiments showed that the S-naproxen imprinted polymer had better recognition capability for the template than that of a blank polymer. The adsorption distribution coefficient KD of S-naproxen on molecularly-imprinted polymer was 153.2 g/mL, and the separation factor was 1.95 when the initial concentration of substrate was 2.0 mmol/L. Scatchard curves suggested that there were two classes of binding sites in the imprinted polymer and only one class in the blank polymer. Computer simulation using Hyperchem showed the existence of the interactions between the template and the functional monomer as well as the models of the complexes formed by the template and the monomer. 相似文献
188.
关于凸曲面的几个定义的关系 总被引:1,自引:0,他引:1
本文讨论了凸曲面的几种定义及其关系,发现有的定义是局部凸的定义,有的是整体凸的定义,有的则对于局部凸和整体凸都适合,最后给出了各种定义之间互推的证明,对于局部凸和整体凸定义之间不能推证的,则说明了原因. 相似文献
189.
This paper presents an evaluation of the capability of turbulence models available in the commercial CFD code FLUENT 6.0 for their application to hydrofoil turbulent boundary layer separation flow at high Reynolds numbers. Four widely applied two‐equation RANS turbulence models were assessed through comparison with experimental data at Reynolds numbers of 8.284×106 and 1.657×107. They were the standard k–εmodel, the realizable k–εmodel, the standard k–ωmodel and the shear‐stress‐transport (SST) k–ωmodel. It has found that the realizable k–εturbulence model used with enhanced wall functions and near‐wall modelling techniques, consistently provides superior performance in predicting the flow characteristics around the hydrofoil. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
190.
有限长通电螺线管空间的磁场分布 总被引:2,自引:0,他引:2
本文计算了有限长通电螺线管空间的磁感应强度分布,给出了解析表达式,并绘出了它们的空间分布图。 相似文献