全文获取类型
收费全文 | 499篇 |
免费 | 11篇 |
专业分类
化学 | 352篇 |
晶体学 | 6篇 |
力学 | 19篇 |
数学 | 31篇 |
物理学 | 102篇 |
出版年
2022年 | 6篇 |
2021年 | 9篇 |
2020年 | 13篇 |
2019年 | 10篇 |
2018年 | 14篇 |
2017年 | 6篇 |
2016年 | 20篇 |
2015年 | 16篇 |
2014年 | 9篇 |
2013年 | 25篇 |
2012年 | 12篇 |
2011年 | 33篇 |
2010年 | 20篇 |
2009年 | 14篇 |
2008年 | 16篇 |
2007年 | 22篇 |
2006年 | 17篇 |
2005年 | 16篇 |
2004年 | 16篇 |
2003年 | 7篇 |
2002年 | 20篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 10篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 12篇 |
1984年 | 10篇 |
1983年 | 4篇 |
1982年 | 11篇 |
1981年 | 7篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 9篇 |
1976年 | 9篇 |
1975年 | 9篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1972年 | 8篇 |
1971年 | 3篇 |
1967年 | 2篇 |
排序方式: 共有510条查询结果,搜索用时 93 毫秒
41.
42.
The influence of treatment in a magnetic field at low temperatures on the nonlinear optical properties of NiI2-doped CdI2 single crystals is investigated. The impurity ions in the interlayer space or more complex centers into which these ions enter can align on exposure to a magnetic field due to the interaction with the membrane vibrations of the lattice and create residual polarization in a specimen. This polarization causes redistribution of the electric charge on the bonds and improves the nonlinear optical properties of single crystals. 相似文献
43.
We present a new computational method with associated computer program TROVE (Theoretical ROVibrational Energies) to perform variational calculations of rovibrational energies for general polyatomic molecules of arbitrary structure in isolated electronic states. The (approximate) nuclear kinetic energy operator is represented as an expansion in terms of internal coordinates. The main feature of the computational scheme is a numerical construction of the kinetic energy operator, which is an integral part of the computation process. Thus the scheme is self-contained, i.e., it requires no analytical pre-derivation of the kinetic energy operator. It is also general, since it can be used in connection with any internal coordinates. The method represents an extension of our model for pyramidal XY3 molecules reported previously [S.N. Yurchenko, M. Carvajal, P. Jensen, H. Lin, J.J. Zheng, W. Thiel, Mol. Phys. 103 (2005) 359]. Non-rigid molecules are treated in the Hougen-Bunker-Johns approach [J.T. Hougen, P.R. Bunker, J.W.C. Johns, J. Mol. Spectrosc. 34 (1970) 136]. In this case, the variational calculations employ a numerical finite basis representation for the large-amplitude motion using basis functions that are generated by Numerov-Cooley integration of the appropriate one-dimensional Schrödinger equation. 相似文献
44.
Rose Mary Michell Alejandro J. Müller Mariya Spasova Philippe Dubois Stefano Burattini Barnaby W. Greenland Ian W. Hamley Daniel Hermida‐Merino Nicolas Cheval Amir Fahmi 《Journal of Polymer Science.Polymer Physics》2011,49(19):1397-1409
The thermal properties, crystallization, and morphology of amphiphilic poly(D ‐lactide)‐b‐poly(N,N‐dimethylamino‐2‐ethyl methacrylate) (PDLA‐b‐PDMAEMA) and poly (L ‐lactide)‐b‐poly(N,N‐dimethylamino‐2‐ethyl methacrylate) (PLLA‐b‐PDMAEMA) copolymers were studied and compared to those of the corresponding poly(lactide) homopolymers. Additionally, stereocomplexation of these copolymers was studied. The crystallization kinetics of the PLA blocks was retarded by the presence of the PDMAEMA block. The studied copolymers were found to be miscible in the melt and the glassy state. The Avrami theory was able to predict the entire crystallization range of the PLA isothermal overall crystallization. The melting points of PLDA/PLLA and PLA/PLA‐b‐PDMAEMA stereocomplexes were higher than those formed by copolymer mixtures. This indicates that the PDMAEMA block is influencing the stability of the stereocomplex structures. For the low molecular weight samples, the stereocomplexes particles exhibited a conventional disk‐shape structure and, for high molecular weight samples, the particles displayed unusual star‐like shape morphology. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1397–1409, 2011 相似文献
45.
A. G. Yurchenko T. I. Klepa R. I. Yurchenko V. I. Kadentsev B. I. Maksimov O. S. Chizhov 《Russian Chemical Bulletin》1990,39(7):1523-1525
The decomposition of acid and trisubstituted phosphites containing 1- and 2-adamantyl, cyclohexyl, and ethyl groups in various combinations was studied under electron impact. The major directions for the fragmentation of the compounds studied are related to cleavage of the C-O bond, which is accompanied by migration of one or two hydrogen atoms to the phosphorus-containing fragment. Mono-, di-, and triadamantyl phosphites feature the loss of phosphorous acid (in the case of acid phosphites) or alkylphosphorous acid (n the case of trisubstituted phosphites) from the molecular ion, which leads to the generation of a diadamantyl or alkyladamantyl species. In this case, the charge is localized predominantly on the hydrocarbon fragment.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1676–1678, July, 1990. 相似文献
46.
Gerd Teschke Mariya Zhariy Maria Joana Soares 《Mathematical Methods in the Applied Sciences》2008,31(5):575-587
We develop a regularization technique for Perona–Malik diffusion equations that relies on multiresolution techniques. The main result of this paper is to show that the chosen discretization overcomes the ill posedness of the nonlinear Perona–Malik model. The resulting algorithm is tested and the results are compared with pixel‐based methods. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
47.
48.
49.
50.
Mariya V. Kozytska 《Tetrahedron letters》2008,49(18):2899-2901
A unified synthetic approach to the basiliolides/transtaganolides is outlined herein, along with studies illustrating the feasibility of the strategy with respect to the total synthesis of basiliolide B. This work lays the foundation for chemical synthesis of an emerging family of Thapsia metabolites. 相似文献