全文获取类型
收费全文 | 26518篇 |
免费 | 5122篇 |
国内免费 | 1803篇 |
专业分类
化学 | 26368篇 |
晶体学 | 234篇 |
力学 | 983篇 |
综合类 | 125篇 |
数学 | 517篇 |
物理学 | 5216篇 |
出版年
2024年 | 43篇 |
2023年 | 308篇 |
2022年 | 794篇 |
2021年 | 935篇 |
2020年 | 1647篇 |
2019年 | 1334篇 |
2018年 | 1163篇 |
2017年 | 1092篇 |
2016年 | 1734篇 |
2015年 | 1534篇 |
2014年 | 1660篇 |
2013年 | 2309篇 |
2012年 | 1667篇 |
2011年 | 1678篇 |
2010年 | 1418篇 |
2009年 | 1426篇 |
2008年 | 1359篇 |
2007年 | 1292篇 |
2006年 | 1227篇 |
2005年 | 1121篇 |
2004年 | 1085篇 |
2003年 | 878篇 |
2002年 | 1593篇 |
2001年 | 591篇 |
2000年 | 477篇 |
1999年 | 466篇 |
1998年 | 451篇 |
1997年 | 377篇 |
1996年 | 307篇 |
1995年 | 275篇 |
1994年 | 215篇 |
1993年 | 138篇 |
1992年 | 132篇 |
1991年 | 97篇 |
1990年 | 79篇 |
1989年 | 70篇 |
1988年 | 82篇 |
1987年 | 51篇 |
1986年 | 99篇 |
1985年 | 28篇 |
1984年 | 27篇 |
1983年 | 13篇 |
1982年 | 17篇 |
1981年 | 24篇 |
1980年 | 13篇 |
1979年 | 18篇 |
1978年 | 13篇 |
1977年 | 10篇 |
1972年 | 13篇 |
1966年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Future pathways for combinatorial chemistry 总被引:1,自引:0,他引:1
David Brown 《Molecular diversity》1997,2(4):217-222
Summary Investment in combinatorial chemistry (combichem) in the pharmaceutical industry is being driven by the need for increased efficiency. Results from pioneers in the field have demonstrated where mixture or discrete compound synthesis is useful, and what mixture sizes and compound concentrations are appropriate. To make the techniques of combichem of general utility in drug discovery, a broad range of advances is still required. Conversion of organic chemistry to solid phase conditions is key, as are developments in linkers and resins. Library design methodology requires further development. Combinatorial biosynthesis of focused libraries of natural products holds great promise for capitalising on hardwon natural product leads. Miniaturisation of screens is required to reduce the cost of screening combinatorial libraries. Developments in the processes preceding and following synthesis are required to enable the flow of increased numbers of compounds without new bottlenecks developing. The impact of combinatorial chemistry will be greatly enhanced by synergy with ongoing parallel developments in genetic technologies, screening technologies and bioinformatics. 相似文献
102.
103.
104.
105.
Serge Palacin Christophe Bureau Julienne Charlier Guy Deniau Brigitte Mouanda Pascal Viel 《Chemphyschem》2004,5(10):1468-1481
Electrografting is a powerful and versatile technique for modifying and decorating conducting surfaces with organic matter. Mainly based on the electro-induced polymerization of dissolved electro-active monomers on metallic or semiconducting surfaces, it finds applications in various fields including biocompatibility, protection against corrosion, lubrication, soldering, functionalization, adhesion, and template chemistry. Starting from experimental observations, this Review highlights the mechanism of the formation of covalent metal-carbon bonds by electro-induced processes, together with major applications such as derivatization of conducting surfaces with biomolecules that can be used in biosensing, lubrication of low-level electrical contacts, reversible trapping of ionic waste on reactive electrografted surfaces as an alternative to ion-exchange resins, and localized modification of conducting surfaces, a one-step process providing submicrometer grafted areas and which is used in microelectronics. 相似文献
106.
107.
N. S. Oliveira J. Dorgan J. A. P. Coutinho A. Ferreira J. L. Daridon I. M. Marrucho 《Journal of Polymer Science.Polymer Physics》2007,45(5):616-625
The sorption of carbon dioxide in glassy Poly(lactic acid) (PLA) films was studied by quartz crystal microbalance (QCM) at high pressures. Two thermal treatments, melted and quenched, were performed in PLA with two different L:D contents, 80:20 and 98:2, films and compared with a third thermal protocol, annealed, and used in a previous work. The results obtained show that for pressures higher than 2 MPa, the carbon dioxide solubility is larger in PLA 80:20 than in PLA 98:2, indicating that the L:D plays a dominant role on this property. The thermal treatments only affect the gas solubility in PLA 98:2. Sorption isotherms at temperatures 303, 313, and 323 K, below the glass transition temperature of the polymer, and pressures up to 5 MPa were measured and analyzed with three different models, the dual‐mode sorption model, the Flory–Huggins equation, and a modified dual‐mode sorption model where the Henry's law term was substituted by the Flory–Huggins equation. This last model performs especially well for CO2 in PLA 80:20, due to the convex upward curvature of the solubility isotherms for that system. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 616–625, 2007 相似文献
108.
The trisilanol 1,3,5‐(HOi‐Bu2Si)3C6H3 ( 7 ), prepared in three steps from 1,3,5‐tribromobenzene via the intermediates 1,3,5‐(Hi‐Bu2Si)3C6H3 ( 8 ) and 1,3,5‐(Cli‐Bu2Si)3C6H3 ( 9 ) forms an equimolar complex with trans‐bis(4‐pyridyl)ethylene (bpe), 7 ·bpe, whose structure was investigated by X‐ray crystallography. The hydrogen‐bonded network features a number of SiO? H(H)Si and SiO? H hydrogen bridges. Evidence was found for cooperative strengthening within the sequential hydrogen bonds. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
109.
110.
针对磷化铟(InP)复合沟道高电子迁移率晶体管(HEMT)的特点,对常规单沟道HEMT的小信号物理模型进行了修正,提出了一种新的用于复合沟道HEMT的小信号物理模型,用商用器件模拟软件ISE(integrated systems engineering)对其进行了仿真验证,对比了实测和仿真的I-V特性及转移特性曲线,重点研究了在InGaAs/InP双层沟道中考虑量子效应后的电场和电流密度随着不同栅电压的变化趋势,研究结果表明,由于在沟道中存在量子效应,在栅下靠源端低电场区域,电流主要分布在InGaAs沟道
关键词:
高电子迁移率晶体管
复合沟道
物理模型
磷化铟 相似文献