全文获取类型
收费全文 | 9558篇 |
免费 | 1988篇 |
国内免费 | 1018篇 |
专业分类
化学 | 7354篇 |
晶体学 | 46篇 |
力学 | 881篇 |
综合类 | 50篇 |
数学 | 440篇 |
物理学 | 3793篇 |
出版年
2024年 | 13篇 |
2023年 | 130篇 |
2022年 | 192篇 |
2021年 | 235篇 |
2020年 | 347篇 |
2019年 | 377篇 |
2018年 | 405篇 |
2017年 | 349篇 |
2016年 | 403篇 |
2015年 | 501篇 |
2014年 | 710篇 |
2013年 | 922篇 |
2012年 | 732篇 |
2011年 | 767篇 |
2010年 | 599篇 |
2009年 | 685篇 |
2008年 | 651篇 |
2007年 | 578篇 |
2006年 | 573篇 |
2005年 | 511篇 |
2004年 | 473篇 |
2003年 | 431篇 |
2002年 | 297篇 |
2001年 | 212篇 |
2000年 | 219篇 |
1999年 | 181篇 |
1998年 | 162篇 |
1997年 | 144篇 |
1996年 | 113篇 |
1995年 | 128篇 |
1994年 | 95篇 |
1993年 | 76篇 |
1992年 | 58篇 |
1991年 | 20篇 |
1990年 | 43篇 |
1989年 | 29篇 |
1988年 | 24篇 |
1987年 | 29篇 |
1986年 | 20篇 |
1985年 | 16篇 |
1984年 | 22篇 |
1983年 | 6篇 |
1982年 | 15篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 12篇 |
1977年 | 10篇 |
1976年 | 6篇 |
1973年 | 6篇 |
1957年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
81.
The syntheses of two rigid organic molecular rods bearing a nitronyl-nitroxide radical and a terminal nitrogen-based functionality like a pyridine or a cyano group are reported. Both new paramagnetic molecules are fully characterized, including crystal structure analysis. Furthermore their magnetic behaviours in the crystalline state are investigated and their spin concentration corroborate their excellent purity. While the pyridine functionalized rod is synthesized by converting the corresponding benzaldehyde to the phenyl-nitronyl-nitroxide radical, the synthesis of the cyano functionalized rod demonstrates the accessibility of highly sophisticated spin-labelled molecules via cross-coupling reaction with a meta-iodo-phenyl-nitronyl-nitroxide moiety. 相似文献
82.
The propagation of solitons through optical couplers is studied here in this paper. Both the twin-core couplers as well as the multiple-core couplers are considered here in this paper. The parameter dynamics of the solitons that are governed by the coupled generalized nonlinear Schrodinger's equation, due to non-Kerr law nonlinearity, has been obtained for such couplers. 相似文献
83.
溶液中CO…CO+体系相互作用的理论研究 总被引:3,自引:2,他引:1
在B3LYP/6-311+G水平上利用SCRF方法中的Onsager model模型考察了CO…CO+体系在两种介质(水和苯)中可能存在的相互作用复合物,发现由于H2O与CO+之间存在较强的相互作用,在水中仅能存在一种稳定结构,而在苯溶液中存在三种稳定的复合物.通过消除基函数引起的叠加误差(BSSE)和零点振动能(ZPVE)的校正,精确求算出三种复合物在两种介质中的相互作用能,表明溶剂的性质对复合物的稳定性有着重要的影响. 相似文献
84.
85.
86.
We present two methods for the creation of two-particle entangled states of excitons in a coupled quantum dot system. The system contains two identical quantum dots that are coupled by an inter-dot hopping process. The manipulation of the system is succeeded by proper application of an external laser field. 相似文献
87.
88.
89.
NongYueHE JianXinTANG SongLI HongCHEN AnCunZHOU 《中国化学快报》2005,16(3):397-400
Polypropylene microporous membranes were treated with plasma in a mixture of N2 and H2 (1:2 in volume). Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and ultra-violet (UV) spectra demonstrated the success of grafting amino groups. The density of the polar amino groups on the membrane surface is about 0.59 μmol/cm^2. The as-treated membranes were successively applied to the in situ synthesis of oligonucleotides and an average coupling yield was more than 98%. The surface feature of the treated membrane is suggested to be responsible for its advantage over a glass slide. 相似文献
90.
John A. Mikroyannidis Larysa Fenenko Masayuki Yahiro Chihaya Adachi 《Journal of polymer science. Part A, Polymer chemistry》2007,45(20):4661-4670
Three new copolymers, namely poly(fluorenevinylene‐alt‐naphthalenevinylene) ( N ), poly(fluorenevinylene‐alt‐anthracenevinylene) ( A ) and poly(fluorenevinylene‐alt‐pyrenevinylene) ( P ), were synthesized by Heck coupling of 9,9‐dihexyl‐2, 7‐divinylfluorene with a polynuclear aromatic dibromide. The 9,10‐disubstituted anthracene was obtained exclusively for A while N and P were obtained as a mixture of two isomers with predominant the 1,4‐disubstituted naphthalene and 1,8‐disubstituted pyrene, respectively. The polymers were soluble in common organic solvents and decomposed above 370 °C. Their glass transition temperature increased from 58 to 110 °C by increasing the number of the phenyl rings of the polynuclear aromatic moiety. Rather high‐efficiency blue and blue‐greenish photoluminescence (PL) of these copolymers in solution was largely decreased in their films, indicating the presence of concentration quenching in the solid state. The OLED using these polymers demonstrated green EL in the case of copolymers N and A , and red EL in the P derivative with ηEL = 0.26–0.31%. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4661–4670, 2007 相似文献