全文获取类型
收费全文 | 2536篇 |
免费 | 105篇 |
国内免费 | 19篇 |
专业分类
化学 | 1836篇 |
晶体学 | 18篇 |
力学 | 20篇 |
数学 | 367篇 |
物理学 | 419篇 |
出版年
2023年 | 14篇 |
2022年 | 40篇 |
2021年 | 51篇 |
2020年 | 62篇 |
2019年 | 70篇 |
2018年 | 53篇 |
2017年 | 54篇 |
2016年 | 107篇 |
2015年 | 84篇 |
2014年 | 109篇 |
2013年 | 177篇 |
2012年 | 178篇 |
2011年 | 220篇 |
2010年 | 128篇 |
2009年 | 112篇 |
2008年 | 167篇 |
2007年 | 146篇 |
2006年 | 139篇 |
2005年 | 103篇 |
2004年 | 97篇 |
2003年 | 63篇 |
2002年 | 64篇 |
2001年 | 29篇 |
2000年 | 22篇 |
1999年 | 23篇 |
1998年 | 26篇 |
1997年 | 20篇 |
1996年 | 24篇 |
1995年 | 16篇 |
1994年 | 10篇 |
1993年 | 21篇 |
1992年 | 12篇 |
1991年 | 13篇 |
1990年 | 13篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 17篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1983年 | 7篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1977年 | 6篇 |
1975年 | 9篇 |
1970年 | 5篇 |
1966年 | 6篇 |
1958年 | 6篇 |
1956年 | 5篇 |
1955年 | 9篇 |
排序方式: 共有2660条查询结果,搜索用时 15 毫秒
91.
We consider one-dimensional Schrödinger-type operators in a bounded interval with non-self-adjoint Robin-type boundary conditions. It is well known that such operators are generically conjugate to normal operators via a similarity transformation. Motivated by recent interests in quasi-Hermitian Hamiltonians in quantum mechanics, we study properties of the transformations and similar operators in detail. In the case of parity and time reversal boundary conditions, we establish closed integral-type formulae for the similarity transformations, derive a non-local self-adjoint operator similar to the Schrödinger operator and also find the associated “charge conjugation” operator, which plays the role of fundamental symmetry in a Krein-space reformulation of the problem. 相似文献
92.
93.
Miroslav Jelínek Petr Písařík Tomáš Kocourek Josef Zemek Jaroslav Lukeš 《Applied Physics A: Materials Science & Processing》2013,110(4):943-947
A hybrid PLD system with ion bombardment of films was developed. Growing DLC films were modified during the laser deposition (10 J?cm?2) by argon ions with energy in the range from 40 eV to 210 eV and cathode current of 0.15 A and 0.5 A. The content of sp2 “graphitic” and sp3 “diamond” bonds was measured using XPS. Sp3 bonds changed from 60 % to 81 %. We found the highest sp3 content for energy of 40 eV. Hardness (and reduced Young’s modulus) were determined by nanoindentation and reached 49 GPa (277 GPa). Film adhesion was studied using the scratch test and was up to 14 N for titanium substrates. Relations among deposition conditions and measured properties are presented. 相似文献
94.
Szymon Godlewski Jakub S. Prauzner-Bechcicki Janusz Budzioch Lukasz Walczak Irena G. Stará Ivo Starý Petr Sehnal Marek Szymonski 《Surface science》2012,606(21-22):1600-1607
Helicenes are carbon-rich materials with an ordered structure that possess interesting and remarkable electronic, chiroptical, mechanical and magnetic properties either in bulk or as single molecule devices. We report on the first attempt to anchor and organize [11]anthrahelicene ([11]AH) molecules onto a metal oxide surface. Molecular structures obtained on the (110) and (011) faces of rutile titania are characterized using scanning probe microscopy. On the (110) surface, [11]AH molecules form islands that are comprised of small domains of two types that are mirror reflections of each other and have an ordered quasi-hexagonal lattice. In contrast, molecules form unordered clusters on the (011) surface. Single molecules on both faces are imaged with sub-molecular resolution. 相似文献
95.
96.
Petr P. Sharin Sofia P. Yakovleva Susanna N. Makharova Maria I. Vasilieva Vasilii I. Popov 《Composite Interfaces》2019,26(1):53-65
The structural-phase state of the contact zone and the factors that influence on the strength of diamond retention in the diamond carbide composites were determined. Composites were obtained by the new hybrid technology that eliminates the reheating of the metalized coating. The elaborated technology combines the thermal diffusion metallization of a diamond and the sintering by the scheme of self-dosed impregnation in a one-stage technological cycle. By the methods of electron microscopy, X-ray diffraction analysis, and Raman spectroscopy the structural and phase characteristics of the interphase boundary were investigated. The improvement of chemical and mechanical adhesion between the diamond and carbide matrix was obtained. It was shown that the specific productivity of the samples with a metalized diamond component is 39% higher than those without metallization. 相似文献
97.
98.
Jan Pecháček Jiří Václavík Jan Přech Petr Šot Jakub Januščák Beáta Vilhanová Jiří Vavřík Marek Kuzma Petr Kačer 《Tetrahedron: Asymmetry》2013,24(4):233-239
We present, to the best of our knowledge, the first parametric study of the asymmetric transfer hydrogenation of imines catalyzed by a Noyori-type catalytic complex based on ruthenium. A model imine for this study was 1-methyl-3,4-dihydroisoquinoline, and a well-known complex RuCl(η6-p-cymene)((1S,2S)-N-p-toluenesulfonyl-1,2-diphenylethylenediamine) was chosen as the model catalyst. The reactions were performed in the presence of a formic acid–triethylamine mixture as the source of hydrogen.The parameters examined include general parameters, for example, concentration, temperature, and substrate-to-catalyst molar ratio, as well as parameters specific to this particular reaction, such as the amount of the hydrogenation mixture used, the ratio of its components, or the inhibitive effect of carbon dioxide. During this study, several unexpected parameters worth further investigation have emerged. 相似文献
99.
Alexey V. Laptev Dmitrii E. Pugachev Alexey Yu. Lukin Andrei V. Nechaev Nikolay E. Belikov Olga V. Demina Petr P. Levin Andrey A. Khodonov Andrey F. Mironov Sergei D. Varfolomeev Vitalii I. Shvets 《Mendeleev Communications》2013,23(4):199-201
A new 5,10,15,20-tetrasubstituted porphyrin containing four 6’-nitro-1,3,3-trimethylspiro(indolino-2,2’-2H-chromene) substituents and its complexes with Zn2+ and Cu2+ ions were prepared and characterized by physicochemical methods of analysis. 相似文献
100.