全文获取类型
收费全文 | 684篇 |
免费 | 35篇 |
国内免费 | 3篇 |
专业分类
化学 | 522篇 |
力学 | 27篇 |
数学 | 85篇 |
物理学 | 88篇 |
出版年
2023年 | 8篇 |
2022年 | 14篇 |
2021年 | 10篇 |
2020年 | 12篇 |
2019年 | 21篇 |
2018年 | 17篇 |
2017年 | 10篇 |
2016年 | 29篇 |
2015年 | 29篇 |
2014年 | 11篇 |
2013年 | 34篇 |
2012年 | 45篇 |
2011年 | 59篇 |
2010年 | 22篇 |
2009年 | 29篇 |
2008年 | 35篇 |
2007年 | 56篇 |
2006年 | 33篇 |
2005年 | 32篇 |
2004年 | 35篇 |
2003年 | 28篇 |
2002年 | 30篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 7篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 16篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 3篇 |
1976年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1962年 | 3篇 |
1960年 | 2篇 |
排序方式: 共有722条查询结果,搜索用时 62 毫秒
101.
We investigate the six quaternionic theta constants introduced by Freitag and Hermann. More precisely we investigate their
restrictions to the Hermitian resp. Siegel half-space of degree 2. It turns out that these theta constants generate the graded
ring of symmetric Hermitian modular forms for the principal congruence subgroup of level 1 + i over the Gaussian number field resp. of Siegel modular forms for the principal congruence subgroup of level 2 and even weight.
As an application we obtain a simple construction of Igusa’s Siegel modular form of degree 2 and weight 30 with respect to
the non-trivial character. 相似文献
102.
103.
Felicitas Brmmel Dominic Kramer Benjamin P. Brown Heino Finkelmann Anke Hoffmann 《Macromolecular rapid communications》2013,34(2):135-141
We present studies on bulk smectic‐A copolymer networks with end‐on attached homeotropically oriented mesogens that show spontaneous optical biaxiality at room temperature. Orthoscopic and conoscopic investigations under uniaxial extension in the layer planes give first evidence of the orientability of the minor director in mechanical fields yielding biaxial monodomains with 3‐d orientational long‐range order of all three principle axes. This is an important step towards the synthesis of permanently oriented biaxial monodomain elastomers for which highly interesting mechanical and optical properties are expected. 相似文献
104.
In this work we present a novel approach to the modeling of magnetorheological elastomers (MREs) for finite deformations. Keeping in mind the composite nature at the microscale, we employ the microsphere model as an effective tool to capture the constitutive response of the material. The microsphere model has been successfully applied to the modelling of rubber-like materials. Here, we extend this approach by taking into account the effect of the magnetic dipole-dipole interactions on the orientation of the polymer chains. Thus, the presented microsphere model is directly motivated by considering the underlying phenomena at the microscale level. Finally the material model is embedded in a finite element framework and the results of a boundary value problems is presented. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
105.
Mingxiang Chen Dominic P. Clemence 《Journal of Difference Equations and Applications》2013,19(9):887-899
This paper considers a non-linear system of ordinary differential equations, which arises in the study of hantavirus epidemics. The system has the property that the total population obeys the logistic equation. For this system, we use linearization and the dynamical properties of the logistic equation to analyze the dynamics of the subpopulation system. In view of the usual numerical instabilities associated with standard finite difference methods used for simulating such systems, we construct non-standard finite difference (NSFD) schemes, which preserve the dynamic properties of the system, and may therefore be used for its simulation. 相似文献
106.
Mingxiang Chen Dominic P. Clemence 《Journal of Difference Equations and Applications》2013,19(12):1243-1256
This paper studies the stability properties of a nonstandard finite difference (NSFD) scheme used to simulate the dynamics of a mouse population model in hantavirus epidemics. It is shown that this difference scheme and the underlying system of differential equations have the same dynamics. The proof uses the fact that the total population obeys the logistic equation, as well as techniques from calculus, graphical analysis, and dynamical systems. 相似文献
107.
108.
Kuldeep Singh Charak Ravinder Kumar Dominic Rochon 《Advances in Applied Clifford Algebras》2013,23(3):593-605
This paper presents a bicomplex version of the Spectral Decomposition Theorem on infinite dimensional bicomplex Hilbert spaces. In the process, the ideas of bounded linear operators, orthogonal complements and compact operators on bicomplex Hilbert spaces are introduced and treated in relation with the classical Hilbert space M′ imbedded in any bicomplex Hilbert space M. 相似文献
109.
Matthew J. Hyers Alex M. Fodor Dominic K. Bierwisch Emanuele Curotto 《International journal of quantum chemistry》2019,119(13):e25915
Nuclear quantum effects in finite temperature simulations of molecular clusters are determined by taking advantage of a recently developed method based on the Feynman Path Integral. The structural and thermodynamic properties, including the nuclear quantum effects are determined for three Stockmayer clusters. The ionic system contain a lithium ion solvated by six strong dipoles and 12 weaker ones. The presence of the ion in the mixed Stockmayer cluster drastically enhances the fluxional nature of the less polar components which occupy the second solvation layer, whereas the neutral counterpart has the effect of reducing it. The nuclear quantum effects are significant at room temperature and above for the solvated ionic system. These are attributable to two factors: (a) the lightness of the lithium ion and (b) the stiffness of the ion-dipole interactions. At 300 K, the difference between the fully converged quantum and the classical heat capacities is about 1.3 KB for the ionic cluster. This difference is about 10 SDs obtained from 95% confidence estimates of the statistical fluctuations. Cubic convergence is confirmed for temperatures as low as 50 K by regression analysis. The nuclear quantum effects do not change the peak melting temperature of the cluster. 相似文献
110.
Alexander J. Boddy Dominic P. Affron Christopher J. Cordier Emma L. Rivers Alan C. Spivey James A. Bull 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(5):1472-1476
Methods that provide rapid access to new heterocyclic structures in biologically relevant chemical space provide important opportunities in drug discovery. Here, a strategy is described for the preparation of 2,2‐disubstituted azetidines, pyrrolidines, piperidines, and azepanes bearing ester and diverse aryl substituents. A one‐pot rhodium catalyzed N–H insertion and cyclization sequence uses diazo compounds to stitch together linear 1,m‐haloamines (m=2–5) to rapidly assemble 4 ‐, 5 ‐, 6 ‐, and 7 ‐membered saturated nitrogen heterocycles in excellent yields. Over fifty examples are demonstrated, including examples with diazo compounds derived from biologically active compounds. The products can be functionalized to afford α,α‐disubstituted amino acids and applied to fragment synthesis. 相似文献