全文获取类型
收费全文 | 691篇 |
免费 | 19篇 |
国内免费 | 4篇 |
专业分类
化学 | 553篇 |
晶体学 | 9篇 |
力学 | 5篇 |
数学 | 29篇 |
物理学 | 118篇 |
出版年
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 13篇 |
2019年 | 10篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 6篇 |
2015年 | 15篇 |
2014年 | 17篇 |
2013年 | 36篇 |
2012年 | 27篇 |
2011年 | 39篇 |
2010年 | 31篇 |
2009年 | 22篇 |
2008年 | 35篇 |
2007年 | 39篇 |
2006年 | 33篇 |
2005年 | 35篇 |
2004年 | 31篇 |
2003年 | 25篇 |
2002年 | 31篇 |
2001年 | 18篇 |
2000年 | 17篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 8篇 |
1995年 | 4篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1989年 | 5篇 |
1986年 | 9篇 |
1985年 | 17篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1972年 | 6篇 |
1971年 | 4篇 |
1970年 | 6篇 |
1967年 | 5篇 |
1966年 | 4篇 |
排序方式: 共有714条查询结果,搜索用时 15 毫秒
1.
2.
The effect of the cation concentration, hydrolysis temperature, and composition in the CeO2–ZrO2 system on the direct precipitation of ceria–zirconia solid solutions and the structure of the precipitates from acidic aqueous solutions of (NH4)2Ce(NO3)6 and ZrOCl2 by hydrolysis under hydrothermal conditions were investigated. Nanometer-sized (8–10 nm) ceria–zirconia solid solution particles in a composition range of 0 to 60 mol% ZrO2 were directly precipitated from the solutions with total metal cation concentration less than 0.2 mol/dm3 by simultaneous thermal hydrolysis at 150–240°C. The crystalline phase of the precipitates gradually changed from cubic and/or tetragonal to monoclinic with increasing the cation concentration of the solution from 0.2 to 0.8 mol/dm3 at the starting composition of 50 mol% ZrO2 under hydrolysis condition of 150°C for 48 h, which was attributed to decrease in the supply of hydrolyzed Ce component caused by decrease in the hydrolysis ratio of (NH4)2Ce(NO3)6. Ceria–zirconia solid solutions containing large amount of ZrO2 maintained high specific surface area and small-sized crystallite after heat-treatment at 900–1000°C for 1 h. 相似文献
3.
Hidefumi Ohsugi 《Journal of Combinatorial Theory, Series A》2006,113(4):718-725
Athanasiadis [Ehrhart polynomials, simplicial polytopes, magic squares and a conjecture of Stanley, J. Reine Angew. Math., to appear.] studies an effective technique to show that Gorenstein sequences coming from compressed polytopes are unimodal. In the present paper we will use such the technique to find a rich class of Gorenstein toric rings with unimodal h-vectors arising from finite graphs. 相似文献
4.
Hidefumi Kawasaki 《Mathematical Programming》1988,41(1-3):327-339
The purpose of this paper is to give a formula for expressing the second order directional derivatives of the sup-type functionS(x) = sup{f(x, t); t T} in terms of the first and second derivatives off(x, t), whereT is a compact set in a metric space and we assume thatf, f/x and
2
f/x
2 are continuous on
n
× T. We will give a geometrical meaning of the formula. We will moreover give a sufficient condition forS(x) to be directionally twice differentiable. 相似文献
5.
I Kitagawa A Matsuda T Nishimura S Hirai I Yoshioka 《Chemical & pharmaceutical bulletin》1967,15(9):1435-1437
6.
7.
8.
9.
Preparation of Sr2CeO4:Eu3+,Dy3+ white luminescence phosphor particles and thin films by using an emulsion liquid membrane system 总被引:3,自引:0,他引:3
Sr(2)CeO(4) and Sr(2)CeO(4):Eu(3+),Dy(3+) phosphor particles and thin films were prepared by using an emulsion liquid membrane (ELM, water-in-oil-in-water (W/O/W) emulsion) system, containing VA-10 (2-methyl-2-ethylheptanoic acid) as extractant (cation carrier). A two-step extraction enabled efficient extraction for Sr(3+) and rare earth ions, and the resulting precursor metal oxalate particles produced in the internal water phase of the ELM system were about 60 nm in diameter. Calcination of the oxalate particles in air gave submicrometer-sized Sr(2)CeO(4) and Sr(2)CeO(4):Eu(3+),Dy(3+) particles, which showed blue and white luminescence, respectively, by UV excitation. Blue and white luminescence phosphor thin films were also prepared by soaking alumina substrates into the W/O emulsion containing precursor oxalate particles, followed by calcination in air. 相似文献
10.
Katsuma Hiraki Takeo Inoue Hidefumi Hirai 《Journal of polymer science. Part A, Polymer chemistry》1970,8(9):2543-2554
ESR spectra of homogeneous catalyst derived from tris(acetylacetonato)titanium(III) and triethylaluminum were observed at several temperatures from ?78°C, to +25°C, at molar ratios of aluminum to titanium of 1–108. At ?78°C, this catalyst yields a violet complex which shows an ESR signal with a g value of 1.959 and is associated with the first intermediate. At ?40°C to ?30°C, this signal decreases, and two signals with g values of 1.947 and 1.960 are observed. The latter two signals diminish at ?5°C to +10°C, while two kinds of new signals with g values of 1.965 and 1.969 appear overlapping each other. The structures of the species corresponding to these five signals are discussed on the basis of the ESR spectra, the intensity change, and the unpaired spin distribution. A new signal with a g value of 1.978 is found in the presence of butadiene at 25°C at Al/Ti > 8 and is assigned to a growing end of polybutadiene with this catalyst. The polymer yield increases remarkedly at Al/Ti molar ratios greater than 10. The microstructure of the resulting polymer consists almost completely of 1,2 units. The structure of the growing end is proposed to be a titanium (III) species containing two 1-substituted allyl groups, by comparison with the structure ascribed to the growing end of polybutadiene with n-butyl titanate-triethylaluminum catalyst. 相似文献