全文获取类型
收费全文 | 1053篇 |
免费 | 53篇 |
国内免费 | 1篇 |
专业分类
化学 | 825篇 |
晶体学 | 6篇 |
力学 | 40篇 |
数学 | 40篇 |
物理学 | 196篇 |
出版年
2022年 | 9篇 |
2021年 | 22篇 |
2020年 | 13篇 |
2019年 | 16篇 |
2018年 | 15篇 |
2017年 | 12篇 |
2016年 | 21篇 |
2015年 | 24篇 |
2014年 | 36篇 |
2013年 | 48篇 |
2012年 | 62篇 |
2011年 | 67篇 |
2010年 | 48篇 |
2009年 | 41篇 |
2008年 | 75篇 |
2007年 | 68篇 |
2006年 | 70篇 |
2005年 | 70篇 |
2004年 | 65篇 |
2003年 | 50篇 |
2002年 | 46篇 |
2001年 | 26篇 |
2000年 | 31篇 |
1999年 | 22篇 |
1998年 | 9篇 |
1997年 | 15篇 |
1996年 | 10篇 |
1995年 | 8篇 |
1994年 | 9篇 |
1993年 | 11篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1972年 | 2篇 |
排序方式: 共有1107条查询结果,搜索用时 31 毫秒
131.
Summary In a hybrid laminate containing an interfacial crack between piezoelectric and orthotropic layers, the dynamic field intensity
factors and energy release rates are obtained for electro-mechanical impact loading. The analysis is performed within the
framework of linear piezoelectricity. By using integral transform techniques, the problem is reduced to the solution of a
Fredholm integral equation of the second kind, which is obtained from one pair of dual integral equations. Numerical results
for the dynamic stress intensity factor show the influence of the geometry and electric field.
Received 29 June 2001; accepted for publication 3 December 2001 相似文献
132.
1,1‐Dibromo‐2,2‐bis(trimethylsilylethynyl)ethene ( 2 ) reacts with two equivalents of 1‐boraadamantane ( 1 ) by 1,1‐organoboration of both trimethylsilylethynyl groups to give a triene 3 bearing two 4‐methylene‐3‐borahomoadamantane moieties in terminal positions. The triene was characterized by one‐ and two‐dimensional 1H, 11B, 13C and 29Si NMR spectroscopy in solution and X‐ray structural analysis in the solid state. The planes of the C double bond are strongly twisted against each other as a result of the bulky substituents, and the surroundings of the boron atoms deviate from the ideal trigonal planar geometry owing to the tension in the tricyclic frameworks. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
133.
134.
Tzu‐Wei Tsai Eng‐Chi Wang Sie‐Rong Li Yung‐Hua Chen Yu‐Li Lin You‐Feng Wang Keng‐Shiang Huang 《中国化学会会志》2004,51(6):1307-1318
Based on Claisen rearrangement, the double bond isomerization of O‐allyl function together with the formation of O‐vinyl function in one pot, and ring‐closing metathesis (RCM), various phenols were transformed into various benzofurans in good yields. 相似文献
135.
S. Gemming R. Luschtinetz I. Chaplygin G. Seifert C. Loppacher L. M. Eng T. Kunze C. Olbrich 《The European physical journal. Special topics》2007,149(1):145-171
The present study describes an approach for the
scale-bridging modeling of ferroic materials as functional elements
in micro- and nanoelectronic devices. Ferroic materials are
characterized by temperature-dependent complex ordering phenomena of
the internal magnetic, electronic, and structural degrees of freedom
with several involved length and time scales. Hence, the modelling
of such compounds is not straightforward, but relies on a
combination of electronic-structure-based methods like ab-initio and
density-functional schemes with classical particle-based approaches
given by Monte-Carlo simulations with Ising, lattice-gas, or
Heisenberg Hamiltonians, which incorporate material-specific
parameters both from theory and experiment. The interplay of those
methods is demonstrated for device concepts based on electroceramic
materials like ferroelectrics and multiferroics, whose functionality
is closely related with their propensity towards structural and
magnetic polymorphism.
In the present case, such scale-bridging techniques are employed to aid the
development of an organic field effect transistor on a ferroelectric
substrate generated by the self-assembly of field-sensitive molecules
on the surfaces of ferroic oxides. Electronic-structure-based methods
yield the microscopic properties of the oxide, the surface, the molecules, and the
respective interactions. They are combined with classical particle-based methods on a
scale-hopping basis. This combination allows to study the morphology evolution
during the self-assembly of larger adsorbate arrays on the (defective) oxide
surface and to investigate the interplay of low-temperature magnetic ordering
phenomena with the ferroelectric functionality at higher temperatures in
multiferroic oxides like the hexagonal manganites. The combination of
density-functional data with classical continuum modelling also yielded
a model Hamiltonian for the quick determination of the properties of a
gate structure based on bio-functionalized carbon nanotubes. 相似文献
136.
Fringe element reconstruction technique for tracking the free surface in three‐dimensional incompressible flow analysis was developed. The flow field was calculated by the mixed formulation based on a four‐node tetrahedral element with a bubble function at the centroid (P1+/P1). Since an Eulerian approach was employed in this study, the flow front interface was advected by the flow through a fixed mesh. For accurate modelling of interfacial movement, a fringe element reconstruction method developed can provide not only an accurate treatment of material discontinuity but also surface tension across the interface. The effect of surface tension was modelled by imposing tensile stress directly on the constructed surface elements at the flow front interface. To verify the numerical approach developed, the developed algorithm was applied to two examples whose solutions are available in references. Good agreement was obtained between the simulation results and these solutions. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
137.
The complex dynamics of a variable viscoelasticity oscillator is studied using the novel concept of Variable‐Order (VO) Calculus. The damping force in the oscillator varies continuously between the elastic and viscous regimes depending on the position of the mass. The oscillator considered here is composed of a linear spring of stiffness k that inputs a restitutive force Fk = ‐k x, a VO damper of order q(x(t)) that generates a damping force Fq = ‐cq ??q(x(t)) x, and a mass m. A modified Runge‐Kutta method is used in conjunction with a trapezoidal numerical integration technique to yield a second‐order accurate method for the solution of the resulting VO Differential Equation (VODE). The VO oscillator is also modelled using a Constant Order (CO) formulation where a number of CO fractional order differentials are weighted to simulate the VO behavior. The CO formulation asymptotically approaches the VO results when a relatively large number of weights is used. For the viscoelastic range of 0 ≤ q ≤ 1, the dynamics of the oscillator is well approximated by the CO formulation when 5 or more fractional terms are included (e.g., 0, 1/4, 1/2, 3/4, and 1). 相似文献
138.
Yoon Soo Han Sang Dae Kim Lee Soon Park Dong Uk Kim Younghwan Kwon 《Journal of polymer science. Part A, Polymer chemistry》2003,41(16):2502-2511
Four different types of conjugated copolymers, consisting of alternating structures of phenothiazinylene vinylene and phenylene vinylene derivatives such as phenylene vinylene, 1,1′‐biphenyl‐4,4′‐ylene vinylene, 2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylene vinylene, and 9,10‐anthrylene vinylene, were prepared by Horner–Emmons condensation between appropriate diphosphonates and dialdehydes. Single‐layer and double‐layer light‐emitting diodes were fabricated with the synthesized conjugated polymers, and their electroluminescent properties were investigated. Poly(N‐2‐ethylhexyl‐3,6‐phenothiazinylene vinylene‐alt‐9,10‐anthrylene vinylene), containing phenothiazinylene vinylene and anthrylene vinylene as repeat units, emitted a reddish‐orange color with Commission Internationale de l'Eclairage coordinates of x = 0.6173 and y = 0.3814 that was very similar to the National Television System Committee standard red, and it showed a bipolar carrier‐injection/transporting capability caused by electron‐withdrawing anthracene and electron‐donating amino groups. Poly[N‐2‐ethylhexyl‐3,6‐phenothiazinylene vinylene‐alt‐2‐methoxy‐5‐(2‐ethylhexyloxy)‐1,4‐phenylene vinylene], containing phenothiazinylene vinylene and dialkoxy phenylene vinylene moieties, showed excellent hole‐injection/transporting capability. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2502–2511, 2003 相似文献
139.
The distribution of chelate-forming reagents on a basis of arylimidodiphosphate between different organic solvents and 0.1
mol L−1 HNO3 has been studied by liquid-liquid extraction of 46Sc. The values of dimerization constants K2 in selected solvents, particularly on the chlorine and chlorine-fluorine hydrocarbon basis as well as distribution constants
KD(HA) have been determined. 相似文献
140.