全文获取类型
收费全文 | 17260篇 |
免费 | 699篇 |
国内免费 | 155篇 |
专业分类
化学 | 11891篇 |
晶体学 | 163篇 |
力学 | 529篇 |
综合类 | 1篇 |
数学 | 1591篇 |
物理学 | 3939篇 |
出版年
2023年 | 91篇 |
2022年 | 260篇 |
2021年 | 349篇 |
2020年 | 314篇 |
2019年 | 314篇 |
2018年 | 280篇 |
2017年 | 241篇 |
2016年 | 507篇 |
2015年 | 468篇 |
2014年 | 621篇 |
2013年 | 1056篇 |
2012年 | 1247篇 |
2011年 | 1403篇 |
2010年 | 853篇 |
2009年 | 754篇 |
2008年 | 1103篇 |
2007年 | 968篇 |
2006年 | 921篇 |
2005年 | 867篇 |
2004年 | 745篇 |
2003年 | 642篇 |
2002年 | 630篇 |
2001年 | 416篇 |
2000年 | 376篇 |
1999年 | 229篇 |
1998年 | 158篇 |
1997年 | 168篇 |
1996年 | 217篇 |
1995年 | 169篇 |
1994年 | 160篇 |
1993年 | 156篇 |
1992年 | 133篇 |
1991年 | 112篇 |
1990年 | 113篇 |
1989年 | 112篇 |
1988年 | 69篇 |
1987年 | 63篇 |
1986年 | 66篇 |
1985年 | 87篇 |
1984年 | 66篇 |
1983年 | 62篇 |
1982年 | 53篇 |
1981年 | 63篇 |
1980年 | 39篇 |
1979年 | 43篇 |
1978年 | 39篇 |
1977年 | 44篇 |
1976年 | 52篇 |
1975年 | 37篇 |
1974年 | 32篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Won-Sang Chung 《International Journal of Theoretical Physics》2003,42(12):2941-2946
In this paper we use the bosonic realization of ospq(1/2) algebra to obtain its metaplectic representation. The group element for this algebra is shown to be described in terms of the basic hypergeometric function. 相似文献
42.
43.
44.
45.
Kyung Hwa Hong Jong Lyoul Park In Hwan Sul Ji Ho Youk Tae Jin Kang 《Journal of Polymer Science.Polymer Physics》2006,44(17):2468-2474
Polyvinyl alcohol (PVA) nanofibers containing Ag nanoparticles were prepared by electrospinning PVA/silver nitrate (AgNO3) aqueous solutions, followed by short heat treatment, and their antimicrobial activity was investigated for wound dressing applications. Since PVA is a water soluble and biocompatible polymer, it is one of the best materials for the preparation of wound dressing nanofibers. After heat treatment at 155 °C for 3 min, the PVA/AgNO3 nanofibers became insoluble, while the Ag+ ions therein were reduced so as to produce a large number of Ag nanoparticles situated preferentially on their surface. The residual Ag+ ions were reduced by subsequent UV irradiation for 3 h. The average diameter of the Ag nanoparticles after the heat treatment was 5.9 nm and this value increased slightly to 6.3 nm after UV irradiation. It was found that most of the Ag+ ions were reduced by the simple heat treatment. The PVA nanofibers containing Ag nanoparticles showed very strong antimicrobial activity. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2468–2474, 2006 相似文献
46.
Diem Ho 《Numerische Mathematik》1989,56(7):721-734
Summary The acceleration by Tchebychev iteration for solving nonsymmetric eigenvalue problems is dicussed. A simple algorithm is derived to obtain the optimal ellipse which passes through two eigenvalues in a complex plane relative to a reference complex eigenvalue. New criteria are established to identify the optimal ellipse of the eigenspectrum. The algorithm is fast, reliable and does not require a search for all possible ellipses which enclose the spectrum. The procedure is applicable to nonsymmetric linear systems as well. 相似文献
47.
S. Park T. U. Kampen T. Kachel P. Bressler W. Braun D. R. T. Zahn 《Applied Surface Science》2002,190(1-4):376-381
The interaction of Ag and In with a thin film of 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) was studied by near-edge X-ray absorption fine structure (NEXAFS). Upon Ag deposition on a PTCDA film of 20 nm thickness the relative intensities and lineshapes, as well as the angular dependence of the spectra remains unchanged, illustrating the formation of a chemically unreactive Ag/PTCDA interface. On the other hand, the adsorption of 0.3 nm In strongly decreases the intensity of the π* resonances in C and O K-edge NEXAFS spectra. This is attributed to a strong charge transfer between In and PTCDA, leading to a redistribution of the charge in the molecule. However, the absence of a strong shift or new features and negligible dependence of peak intensities corresponding to π* resonances on the In thickness indicate that the interaction between In and PTCDA is not accompanied by a covalent bond formation. 相似文献
48.
In this paper, the nonfragile control problem for synchronization of a class of chaotic dynamical systems with controller gain variations is studied. Using the Lyapunov method and LMI (linear matrix inequality) technique, a criterion for the existence of the nonfragile controller for synchronization is derived in terms of LMI. To show the effectiveness of the proposed method, the control problem is applied to Genesio chaotic system. 相似文献
49.
D. P. Kozlenko S. E. Kichanov S. Lee J. -G. Park V. P. Glazkov B. N. Savenko 《JETP Letters》2006,83(8):346-350
The effect of a high pressure (up to 6 GPa) on the crystal and magnetic structure of the hexagonal manganite LuMnO3 is studied by neutron diffraction in the temperature range 10–295 K. It is found that, as the pressure increases, the ordered magnetic moment of Mn ions at T = 10 K decreases noticeably from 2.48 (0 GPa) to 1.98 μB (6 GPa). This decrease is due to an enhancement of the geometrical frustration effects on the triangular lattice. At the same time, the symmetry of the triangular antiferromagnetic state (the irreducible representation Γ2) remains unchanged. A correlation is revealed between the distortion parameter of the triangular lattice formed by Mn ions and the symmetry of the antiferromagnetic state of hexagonal manganites RMnO3. Based on this correlation, a generalized magnetic phase diagram of these compounds is constructed. The obtained phase diagram provides an explanation for the changes observed in the magnetic state of hexagonal manganites caused by high pressure and chemical substitution. 相似文献
50.
Tung-Yang Ho Ting-Yi Sung Lih-Hsing Hsu Chang-Hsiung Tsai Jeng-Yan Hwang 《Journal of Algorithms in Cognition, Informatics and Logic》1998,28(2):216-257
Given a series-parallel network (network, for short)N, its dual networkN′ is given by interchanging the series connection and the parallel connection of networkN. We usually use a series-parallel graph to represent a network. LetG[N] andG[N′] be graph representations ofNandN′, respectively. A sequence of edgese1, e2,…,ekis said to form a common trail on (G[N], G[N′]) if it is a trail on bothG[N] andG[N′]. If a common trail covers all of the edges inG[N] andG[N′], it is called adouble Euler trail.However, there are many different graph representations for a network. We say that a networkNhas a double Euler trail (DET) if there is a common Euler trail for someG[N] and someG[N′]. Finding a DET in a network is essential for optimizing the layout area of a complementary CMOS functional cell. Maziasz and Hayes (IEEE Trans. Computer-Aided Design9(1990), 708–719) gave a linear time algorithm for solving the layout problem in fixedG[N] andG[N′] and an exponential algorithm for finding the optimal cover in a network without fixing graph representations. In this paper, we study properties of subnetworks of a DET network. According to these properties, we propose an algorithm that automatically generates the rules for composition of trail cover classes. On the basis of these rules, a linear time algorithm for recognizing DET networks is presented. Furthermore, we also give a necessary and sufficient condition for the existence of a double Euler circuit in a network. 相似文献