全文获取类型
收费全文 | 1470篇 |
免费 | 37篇 |
国内免费 | 16篇 |
专业分类
化学 | 1094篇 |
晶体学 | 12篇 |
力学 | 7篇 |
数学 | 213篇 |
物理学 | 197篇 |
出版年
2023年 | 12篇 |
2022年 | 7篇 |
2021年 | 12篇 |
2020年 | 18篇 |
2019年 | 15篇 |
2018年 | 13篇 |
2017年 | 9篇 |
2016年 | 16篇 |
2015年 | 27篇 |
2014年 | 39篇 |
2013年 | 91篇 |
2012年 | 60篇 |
2011年 | 83篇 |
2010年 | 44篇 |
2009年 | 47篇 |
2008年 | 82篇 |
2007年 | 80篇 |
2006年 | 82篇 |
2005年 | 87篇 |
2004年 | 93篇 |
2003年 | 86篇 |
2002年 | 78篇 |
2001年 | 20篇 |
2000年 | 23篇 |
1999年 | 25篇 |
1998年 | 19篇 |
1997年 | 18篇 |
1996年 | 20篇 |
1995年 | 12篇 |
1994年 | 12篇 |
1993年 | 14篇 |
1992年 | 14篇 |
1991年 | 10篇 |
1990年 | 11篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1985年 | 16篇 |
1984年 | 22篇 |
1983年 | 14篇 |
1982年 | 16篇 |
1981年 | 15篇 |
1980年 | 22篇 |
1979年 | 21篇 |
1978年 | 7篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 24篇 |
1973年 | 10篇 |
1972年 | 9篇 |
1968年 | 6篇 |
排序方式: 共有1523条查询结果,搜索用时 15 毫秒
1.
2.
Shigeru Tasaka Norihiro Inagaki Masaaki Igawa 《Journal of Polymer Science.Polymer Physics》1991,29(6):691-694
The permeability of annealed poly (l-(trimethylsilyl)-l-propyne) was studied from the viewpoint of structural information obtained from x-ray diffraction and density. The sample cast from benzene solution had low density (0.82 g/cm3) and high permeability, whereas the annealed sample had a higher density (0.88 g/cm3) and permeability lower by two orders of magnitude. The smaller-angle x-ray diffraction peak for each sample, which was likely to reflect the distance between intermolecular chains, increased in intensity and shifted toward higher angle, corresponding to the change of the density with annealing. The logarithmic oxygen permeability was proportional to the density, namely the free volume fraction correlated with the diffusion coefficient and controlled by annealing and swelling by alcohols. 相似文献
3.
Masaaki Harada 《Designs, Codes and Cryptography》2006,38(1):5-16
In this paper, we show that the code generated by the rows of a block-point incidence matrix of a self-orthogonal 3-(56,12,65)
design is a doubly-even self-dual code of length 56. As a consequence, it is shown that an extremal doubly-even self-dual
code of length 56 is generated by the codewords of minimum weight. We also demonstrate that there are more than one thousand
inequivalent extremal doubly-even self-dual [56,28,12] codes. This result shows that there are more than one thousand non-isomorphic
self-orthogonal 3-(56,12,65) designs.
AMS Classification: 94B05, 05B05 相似文献
4.
Takuya Hashimoto Koichi Kitazawa Masaaki Nakabayashi Tadashi Shiraishi Youichi Suemune Takakazu Yamamoto Hideomi Koinuma 《应用有机金属化学》1991,5(4):325-330
For low-temperature deposition of oxide films relating to Bi-Sr-Ca-Cu-O superconductors, photo-absorption and -decomposition properties were examined with respect to copper and alkaline-earth ß-diketonates. It was confirmed that all ß-diketonates examined were promising as source materials for photochemical vapour deposition (photo-CVD) using a low-pressure mercury lamp, in view of their large light absorption coefficients at wavelength 254 nm. The light irradiation was effective for the formation of highly crystalline oxide films at temperatures below 600 °C. By combining two sources, Ca2CuO3 and SrCuO2 films were prepared. Photo-CVD of c-axis oriented Bi2Sr2CuOx film was achieved by the irradiation of ternary sources of Bi(C6H5)3 and strontium and copper ß-diketonates at 500 °C. 相似文献
5.
In Homma M and Kim SJ [2], the authors considered two-point codes on a Hermitian curve defined over fields of odd characteristic.
In this paper, we study the geometry of a Hermitian curve over fields of even characteristic and classify the two-point codes
whose minimum distances agree with the designed ones. 相似文献
6.
Yasutada Suzuki Masatoshi Endo Jiye Jin Kenji Iwase Masaaki Iwatsuki 《Analytical sciences》2006,22(3):411-414
Tristimulus colorimetry using a digital still camera (DSC) as a colorimeter has been developed. A photograph of a sample and standard solutions was taken simultaneously with the DSC, and it was transferred to a PC. On the PC, the colors of the sample and of the standard solutions were analyzed and L* (brightness), a* (red-green component), and b* (yellow-blue component) values were determined with laboratory-made software. A dedicated light-box containing white-color LEDs as light source was made of white acrylic to make constant exposure at each photograph. Various settings of the DSC, such as exposure mode, white balance, and so on, that affect analytical figures, were studied with determination of iron with 1,10-phenanthroline. This method was successfully applied to the determinations of iron in a river water sample and of residual chlorine in tap water samples with N,N-diethylphenylenediamine (DPD). 相似文献
7.
Masaaki Kubota Raul A. Reimer Kuniko Terajima Yuji Yoshimura Akio Nishijima 《Analytica chimica acta》1987
Inductively-coupled plasma/atomic emission spectrometry with a high-resolution vacuum scanning monochromator is described for the determination of sulfur at 180.734 nm. The behavior of the signal-to-background ratio is investigated as functions of RF power, argon gas flow rate and observation height above the load coil. Under the operating conditions selected, the detection limit is 3 μg l?1. The Se I 196.090-nm line is chosen as internal standard, because the S/Se line pair exhibited the least change with carrier gas flow rate and acid concentration of solution. Sulfur in NiMo and CoMo/ Al2O3 catalysts used for coal liquefaction is determined as S(II) and S(VI) species. The total amount of the species agreed well with the sulfur value obtained by the conventinal combustion method. 相似文献
8.
9.
Noboru Matsumura Atsushi Ito Masaaki Tomura Yasuyuki Okumura Kazuhiko Mizuno 《Journal of heterocyclic chemistry》2004,41(1):99-102
Tetraazathiapentalene derivative 1 reacts with heterocumulenes such as diphenylketene (2) and 2‐pyridylisothiocyanate (5) to give heterocycles 3, 6 and 7 with elimination of methylisothiocyanate. The reactions of thiadiazolopyrimidine derivatives 8a‐b with ethoxycarbonyl isothiocyanate (9) and carbon disulfide (11) gives heterocycles 10 and 12 via thermal decomposition of 1:1 cycloadducts C and D which have a hypervalent sulfur. The mechanistic and reactivity features of these reactions are described. 相似文献
10.
Masaaki Tomura Md. Akhtaruzzaman Kazuharu Suzuki Yoshiro Yamashita 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(7):o373-o375
In the crystal structures of the title compounds, C6H2I2N2S, (I), and C12H4I2N4S2, (II), respectively, a large number of short inter‐heteroatom contacts, such as S?N, I?I and N?I, are observed. In (II), which is non‐centrosymmetric, two halves of the molecule are related by a crystallographic twofold axis. 相似文献