全文获取类型
收费全文 | 3570篇 |
免费 | 119篇 |
国内免费 | 11篇 |
专业分类
化学 | 2799篇 |
晶体学 | 37篇 |
力学 | 37篇 |
数学 | 144篇 |
物理学 | 683篇 |
出版年
2022年 | 24篇 |
2021年 | 21篇 |
2020年 | 43篇 |
2019年 | 63篇 |
2018年 | 44篇 |
2017年 | 22篇 |
2016年 | 68篇 |
2015年 | 64篇 |
2014年 | 79篇 |
2013年 | 171篇 |
2012年 | 185篇 |
2011年 | 208篇 |
2010年 | 117篇 |
2009年 | 104篇 |
2008年 | 195篇 |
2007年 | 186篇 |
2006年 | 184篇 |
2005年 | 181篇 |
2004年 | 168篇 |
2003年 | 155篇 |
2002年 | 144篇 |
2001年 | 88篇 |
2000年 | 88篇 |
1999年 | 58篇 |
1998年 | 36篇 |
1997年 | 47篇 |
1996年 | 42篇 |
1995年 | 31篇 |
1994年 | 35篇 |
1993年 | 48篇 |
1992年 | 44篇 |
1991年 | 51篇 |
1990年 | 53篇 |
1989年 | 33篇 |
1988年 | 43篇 |
1987年 | 43篇 |
1986年 | 37篇 |
1985年 | 61篇 |
1984年 | 47篇 |
1983年 | 23篇 |
1982年 | 35篇 |
1981年 | 38篇 |
1980年 | 26篇 |
1979年 | 36篇 |
1978年 | 35篇 |
1977年 | 42篇 |
1976年 | 33篇 |
1975年 | 22篇 |
1974年 | 20篇 |
1973年 | 22篇 |
排序方式: 共有3700条查询结果,搜索用时 15 毫秒
81.
Kyoji Tsubakiyama Togoro Matsuo Takashi Sasaki Kenzo Yoshida Takashi Fujimura Kunio Araki 《Journal of polymer science. Part A, Polymer chemistry》1979,17(1):173-184
γ-Ray-induced polymerizations of ferrocenylmethyl methacrylate (FMMA) in crystalline and amorphous states were investigated with kinetical and ESR methods. In the crystalline state the polymerization of FMMA proceeded slowly and gave low-molecular-weight polymers, whereas in the amorphous state it proceeded rapidly and gave polymers of much higher molecular weight. Molecular weight distributions of these polymers were binodal. The temperature dependence and the dose-rate dependence of the polymerization rates were different between the two states. Wide-line nuclear magnetic resonance (NMR) spectra of the amorphous monomer suggested that the polymerization proceeded in a supercooled state. Electron spin resonance (ESR) spectra of γ-irradiated FMMA and 1,1′-ferrocenyl-di(methyl methacrylate) showed that ferrocene radicals and methacrylic radicals were formed simultaneously at low temperature; with increasing temperature the former radicals disappeared, whereas the latter changed into growing chain radicals. The yields of radicals were relatively low; this means that ferrocene groups in the monomers behave as a radiation energy absorber. 相似文献
82.
83.
84.
LiBH(4) is a powerful and selective reagent for regiospecific reduction reactions. A simple synthesis of LiB(3)H(4) at near theoretical specific radioactivity is reported. We have treated Li(3)H synthesized from tritium gas ((3)H(2), approximately 98%) with BBr(3) to produce LiB(3)H(4) (specific activity = 4120 GBq/mmol = 110 Ci/mmol. The maximum theoretical specific activity of LiB(3)H(4) is 4252 GBq/mmol = 115.04 Ci/mmol; 1 matom of (3)H = 1063 GBq = 28.76 Ci.) The tritium labeling performance of the reagent was tested by an exemplary reduction of 2-naphthaldehyde to 2-naphthalenemethanol. LiB(3)H(4) and the reduction products were characterized by a combination of (1)H, (3)H, and (11)B NMR techniques, as appropriate. 相似文献
85.
Nobuo Yoshida 《Probability Theory and Related Fields》1993,94(4):473-488
Summary We formulate and prove a large deviation principle for the (r, p)-capacity on an abstract Wiener space. As an application, we obtain a sharpening of Strassen's law of the iterated logarithm in terms of the capacity. 相似文献
86.
87.
Treatment of 3,4-alkadienyl carbonates 2a-i with a low-valent titanium reagent diisopropoxy(eta(2)-propene)titanium (1), readily generated by the reaction of Ti(O-i-Pr)(4) with 2 i-PrMgCl, resulted in an intramolecular nucleophilic acyl substitution (INAS) reaction to afford vinyltitanium compounds 3 which, in turn, reacted with H(3)O(+), D(2)O, or iodine to give alpha-substituted beta,gamma-unsaturated esters 4 in good to excellent yields. The olefin moiety of the hydrolysis product 4 has (Z)-geometry mainly except for 4h. Starting from chiral 2f or 2g, the reaction proceeded stereospecifically to give optically active alpha-substituted beta,gamma-unsaturated ester 4f or 4g having (Z)-olefin geometry exclusively. 相似文献
88.
We have prepared polycrystalline samples of Sr3YCo4O10.56, Sr2.4Ca0.6YCo4O10.54, and Sr3YCo3.76Mn0.24O10.59, and found that these materials show unusual impurity effects on their transport and magnetic properties. A tiny amount of impurities such as Mn or Ca suppresses room-temperature ferromagnetism of Sr3YCo4O10.56. With the suppression, their resistivities and thermopowers are also dramatically changed. We propose that the unusual impurity effects are caused by the suppression of orbital ordering. 相似文献
89.
New substrates and reaction conditions which may be expected to yield phenyl cation intermediates have been investigated. The approaches used were: (a) solvolysis of PhX in fluorinated alcohols, where X = ? N (O) = NOTs (tosyloxyazoxy), ? N (O) = NONf (Nf = C4F9SO) and ? OSO2\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^{\rm + } $\end{document} (CH3)3ōTf (Tf=CF3SO); (b) solvolysis of ArBr, PhOTf and PhOSO2\documentclass{article}\pagestyle{empty}\begin{document}$ \mathop {\rm N}\limits^{\rm + } $\end{document}(CH3)3ōTf (phenyl ‘betylate triflate’) in super-acid solvents (FSO3H · SbF5, SbF5, AgSbF6). Analysis of the product mixtures provided no evidence for the intermediacy of phenyl cations as a major pathway in any of the reactions. This result is remarkable, since the ‘betylate’, for example, is a better leaving group by a factor of at least 105 than the ‘super’ leaving group triflate in the solvolysis of alkyl sulfonates. These results are a further indication of the extremely low stability of phenyl cations, as well as of the very special properties of the nitrogen leaving group in arenediazonium ions. 相似文献
90.