全文获取类型
收费全文 | 5240篇 |
免费 | 879篇 |
国内免费 | 1118篇 |
专业分类
化学 | 3236篇 |
晶体学 | 98篇 |
力学 | 562篇 |
综合类 | 70篇 |
数学 | 38篇 |
物理学 | 1911篇 |
无线电 | 1322篇 |
出版年
2024年 | 15篇 |
2023年 | 49篇 |
2022年 | 133篇 |
2021年 | 157篇 |
2020年 | 192篇 |
2019年 | 178篇 |
2018年 | 133篇 |
2017年 | 188篇 |
2016年 | 226篇 |
2015年 | 223篇 |
2014年 | 239篇 |
2013年 | 408篇 |
2012年 | 382篇 |
2011年 | 436篇 |
2010年 | 361篇 |
2009年 | 334篇 |
2008年 | 346篇 |
2007年 | 388篇 |
2006年 | 374篇 |
2005年 | 329篇 |
2004年 | 293篇 |
2003年 | 292篇 |
2002年 | 276篇 |
2001年 | 206篇 |
2000年 | 182篇 |
1999年 | 162篇 |
1998年 | 127篇 |
1997年 | 116篇 |
1996年 | 106篇 |
1995年 | 92篇 |
1994年 | 62篇 |
1993年 | 46篇 |
1992年 | 34篇 |
1991年 | 33篇 |
1990年 | 22篇 |
1989年 | 18篇 |
1988年 | 20篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 10篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有7237条查询结果,搜索用时 9 毫秒
31.
32.
33.
N. V. Sotskaya O. V. Dolgikh E. I. Ryabinina 《Russian Journal of Electrochemistry》2005,41(8):866-873
The rate of anodic oxidation of the hypophosphite ion on alloys Ni-P, Ni-B, and Ni-Mo-P is studied as a function of their composition and structure. The organic compounds that are customarily used to stabilize electrolytes of electroless nickel plating are shown to come useful when controlling composition of the Ni-P coatings at the expense of their different influence on the rates of partial processes of deposition of the alloy components. The formation of catalytic activity of such coatings is affected mostly by a structural factor. With alloys Ni-P, Ni-B, and Ni-Mo-P, whose composition was varied by altering the concentration of the source of the alloying component, dependence of catalytic activity of the surface on the composition is defined mainly by an electronic factor.__________Translated from Elektrokhimiya, Vol. 41, No. 8, 2005, pp. 972–980.Original Russian Text Copyright © 2005 by Sotskaya, Dolgikh, Ryabinina. 相似文献
34.
The stoichiometric reactions of trimethylaluminum with 2,6‐(MeOCH2)2C6H3OH (LH) revealed compounds L3Al ( 1 ) and L2AlMe ( 2 ). On the other hand reaction of 1 equiv. of LH with trimethylaluminum did not lead to the formation of complex LAlMe2 ( 3 ), rather 2 together with Me3Al were observed as a result of a disproportionation of 3 . Compounds 1 and 2 were characterized by elemental analysis, 1H and 13C NMR spectroscopy and in the case of 1 by X‐ray diffraction. Derivative 2 underwent transmetalation with Ph3SnOH, giving LSnPh3 ( 4 ) as the result of a migration of ligand L from the aluminum to the tin atom. The identity of 4 was established by elemental analysis, 1H, 13C and 119Sn NMR spectroscopy and 1H, 119Sn HMBC experiments. The system 2 and B(C6F5)3 in a 1:1 molar ratio was shown to be active in the polymerization of propylene oxide and ε‐caprolactone. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
35.
本文介绍了一种实用的液态合金离子源结构,我们利用本结构研制成功了Au-Si和Au-Si-Be液态合金离子源,测出了它们的发射特性。 相似文献
36.
C. Papatriantafillou C. E. Paraskevaidis C. Krikos P. Panagopoulos 《Journal of statistical physics》1989,54(1-2):191-200
We study a generalized Ising system consisting of a Bethe lattice on every site of which two spin-1/2 and two isospin-1/2 (or atomic species A) states can be realized, the spin-species interacting with appropriate nearest neighbor couplings. The system is equivalent to that of four states per site and we obtain its exact thermodynamic behavior. The case of a fixed concentration of species is the annealed or liquid magnetic binary alloy. The temperature dependence of the short-range-order (SRO) parameter of such systems is obtained as an application of the theory and discussed in connection with relevant material from the literature. When fixing both the concentration and the nearest neighbor spatial correlation of the species, we obtain Eggarter's formulas for the frozen-in species problem, which therefore are only approximately valid even on the Bethe lattice. 相似文献
37.
38.
Cu-12.7(wt)%Al合金从900℃高温淬至365℃~500℃温度范围等温不同时间(30秒至15分钟)的试样中形成了大量树枝状的γ_2相沉淀粒子。应用配有X线能谱仪(XEDS)和电子能量损失谱仪(EELS)的分析电子显微镜(JEOL JEM-2000FX型)对上还试样研究,结果表明:这些γ_2相粒子具有富铝的“核心”,长大到粒子线度大于约800nm后以不稳定方式生长成“花朵”状。生长过程中伴随着溶质元素Al由基体向γ_2相内的富集。而且在γ_2相粒子内部呈现出Spinodal分解组织的形貌特征,表明γ_2粒子内形成了化学成分调幅。EELS分析表明试样含氧。 相似文献
39.
40.