全文获取类型
收费全文 | 1268篇 |
免费 | 23篇 |
国内免费 | 5篇 |
专业分类
化学 | 978篇 |
晶体学 | 23篇 |
力学 | 18篇 |
数学 | 59篇 |
物理学 | 218篇 |
出版年
2022年 | 6篇 |
2019年 | 11篇 |
2016年 | 10篇 |
2015年 | 23篇 |
2014年 | 24篇 |
2013年 | 83篇 |
2012年 | 64篇 |
2011年 | 67篇 |
2010年 | 40篇 |
2009年 | 35篇 |
2008年 | 61篇 |
2007年 | 61篇 |
2006年 | 57篇 |
2005年 | 64篇 |
2004年 | 65篇 |
2003年 | 47篇 |
2002年 | 45篇 |
2001年 | 25篇 |
2000年 | 15篇 |
1999年 | 16篇 |
1998年 | 17篇 |
1997年 | 15篇 |
1996年 | 13篇 |
1995年 | 14篇 |
1994年 | 12篇 |
1993年 | 11篇 |
1992年 | 18篇 |
1991年 | 19篇 |
1990年 | 26篇 |
1989年 | 16篇 |
1988年 | 13篇 |
1987年 | 12篇 |
1986年 | 17篇 |
1985年 | 28篇 |
1984年 | 24篇 |
1983年 | 17篇 |
1982年 | 21篇 |
1981年 | 23篇 |
1980年 | 25篇 |
1979年 | 21篇 |
1978年 | 11篇 |
1977年 | 16篇 |
1976年 | 11篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1973年 | 8篇 |
1972年 | 5篇 |
1970年 | 4篇 |
1967年 | 4篇 |
1930年 | 4篇 |
排序方式: 共有1296条查询结果,搜索用时 15 毫秒
41.
Toshiyuki Yamashita Takeo Fujino Norio Masaki Hiroaki Tagawa 《Journal of solid state chemistry》1981,37(2):133-139
The structural parameters of α- and β-CdUO4 crystals are determined by X-ray powder diffraction technique. α-CdUO4 is rhombohedral and cell parameters are a = 6.233(3) Å and α = 36.12(5)°. β-CdUO4 crystallizes in a C-centered orthorhombic cell with a = 7.023(4), b = 6.849(3), c = 3.514 (2) Å. The space groups are for α-CdUO4 and Cmmm for β-CdUO4. α-CdUO4: 1U in (000), 1Cd in (), 2O(1) in ±(uuu), 2O(2) in ±(vvv); u = 0.113, v = 0.350, Z = 1. β-CdUO4: 2U in (), 2Cd in (), 4O(1) in (), 4O(2) in (); x = 0.159, y = 0.278, Z = 2. β-CdUO4 contains collinear uranyl UO2+2 groups with a UO(1) distance of 1.91 Å, located either along or parallel to the c axis whereas the UO(1) bond length in α-CdUO4 is 1.98 Å which is longer than the usual uranyl bond length. 相似文献
42.
Numerical Algorithms - In this paper, we propose an infeasible arc-search interior-point algorithm for solving nonlinear programming problems. Most algorithms based on interior-point methods are... 相似文献
43.
44.
In order to interpret abrupt changes of distributions of orientations andmagnitudes of hyperfine fields in Mössbauer measurements of57Fe in YFeMnO4, a model is proposed. The origin is assumed to be not static but dynamic. Fluctuating fields are caused by spins in a fully frustrated spin system, namely, a Heisenberg spin system on a triangular lattice in a two-dimensional antiferromagnet. Extending the stochastic theory for the fluctuation between two states to that among many states with a Gaussian distribution, we fit the spectra with three parameters, hyperfine fieldH
hf, correlation time c, andwidth of fluctuating field , within a limited condition of =c=1. Obtained results represent the characteristic features of Mössbauer spectra well, in spite of a simplified model. 相似文献
45.
46.
47.
Asymmetric monobenzoylation reactions of cyclic meso-1,3- and 1,4-diols were catalyzed by a phosphinite derivative of quinidine to afford the corresponding monobenzoylated diol with good yield and enantioselectivity. [reaction: see text] 相似文献
48.
Nanosized TiO2 supported on activated alumina was prepared using a sonochemical method. To prepare this supported material, direct immersion horn and cup horn ultrasonic systems were used. The efficiency of the sonochemical coating process was determined by UV photodecolourisation of the aqueous methyl orange solution. It was found that TiO2 supported on activated alumina prepared by the sonochemical method gave the maximum decolourisation efficiency. In that method itself, direct immersion horn gave a higher photodecolourisation activity as compared to the cup horn. The obtained results suggest that the direct immersion horn results in uniform, as well as a maximum number of TiO2 particles to be adsorbed on an activated alumina surface. 相似文献
49.
Copper mediated alkyl-transfer reaction of trialkylaluminum (R3Al) with (E)-4,4-difluoro-5-hydroxyallylic alcohol derivative smoothly proceeded to give the corresponding 2-alkylated 4-fluoro-5-hydroxyhomoallylic alcohol derivative with completely Z and 2,5-syn selective manner. Regio- and stereoselective conversion of the C5-hydroxyl group of the fluoroolefin thus obtained to amino group could be achieved through one-pot mesylation and azidation reaction. 相似文献
50.
Katsuyuki Ogura Kunio Sanada Kazumasa Takahashi Hirotada Iida 《Tetrahedron letters》1982,23(39):4035-4038
Ethyl 2-acetylalkanoate gave ethyl 2-(methyl- or phenylthio)alkanoate in high yield on treatment wiht CH3SSO2CH3, PhSSO2Ph, or PhSSPh in the presence of small excess of EtONa in EtOH. Application of the present method to synthesis of pellitorine and the queen substance is also described. 相似文献