全文获取类型
收费全文 | 610篇 |
免费 | 16篇 |
专业分类
化学 | 389篇 |
晶体学 | 2篇 |
力学 | 37篇 |
数学 | 89篇 |
物理学 | 109篇 |
出版年
2023年 | 3篇 |
2022年 | 14篇 |
2021年 | 14篇 |
2020年 | 6篇 |
2019年 | 5篇 |
2018年 | 8篇 |
2017年 | 8篇 |
2016年 | 16篇 |
2015年 | 14篇 |
2014年 | 16篇 |
2013年 | 26篇 |
2012年 | 29篇 |
2011年 | 44篇 |
2010年 | 6篇 |
2009年 | 20篇 |
2008年 | 38篇 |
2007年 | 37篇 |
2006年 | 23篇 |
2005年 | 23篇 |
2004年 | 19篇 |
2003年 | 18篇 |
2002年 | 22篇 |
2001年 | 7篇 |
2000年 | 3篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1989年 | 9篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 3篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 6篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1964年 | 3篇 |
1960年 | 3篇 |
1913年 | 2篇 |
1908年 | 2篇 |
排序方式: 共有626条查询结果,搜索用时 8 毫秒
51.
Francesco A. Devillanova Gaetano Verani Luigi P. Battaglia Anna Bonamartini Corradi 《Transition Metal Chemistry》1980,5(1):362-364
Summary New complexes of copper(I) withN,N-dialkylsubstituted imidazolidine-2-thione ligands were prepared by reduction of CuX2 (X = Cl or Br). The i.r. spectra show that in all the complexes the ligand coordinates through the sulphur atom. The crystal structure of chloro-bis(N,N-dimethylimidazolidine-2-thione)copper(I) has been determined from x-ray diffraction data. Crystals are monoclinic. space groupC
2, with unit cell dimensions:a = 16.022(15),b = 9.942(10),c = 15.112(15) A, = 139.84(10)2, Z = 4. The final R index is 5.2%. The copper coordination is trigonal, involving sulphur atoms of the two ligands and One chlorine atom. The steric effect of the two methyls imposes a rotation of the imidazolidine rings with respect to the coordination plane. The dihedral angle between the mean plane of thiourea moieties. parallel one with the other. and the coordination plane is 119.3°.This work was supported by the National Research Council (C.N.R.) of Rome. 相似文献
52.
In the field of the Jacobian conjecture it is well-known after Dru?kowski that from a polynomial ‘cubic-homogeneous’ mapping we can build a higher-dimensional ‘cubic-linear’ mapping and the other way round, so that one of them is invertible if and only if the other one is. We make this point clearer through the concept of ‘pairing’ and apply it to the related conjugability problem: one of the two maps is conjugable if and only if the other one is; moreover, we find simple formulas expressing the inverse or the conjugations of one in terms of the inverse or conjugations of the other. Two nontrivial examples of conjugable cubic-linear mappings are provided as an application. 相似文献
53.
Gaetano D’Avino 《Rheologica Acta》2013,52(3):221-236
Deterministic lateral displacement devices have been proved to be an efficient way to perform continuous particle separation in microfluidic applications (Huang et al. Science 304:987–990, 2004). On the basis of their size, particles traveling through an array of obstacles follow different paths and can be separated in outflow. One limitation of such a technique is that each device works for a specific critical size to achieve particle separation, and a new device with different geometrical properties needs to be fabricated, as the dimensions of the particles to be separated change. In this work, we demonstrate the possibility to tune the critical particle size in a deterministic lateral displacement device by using non-Newtonian fluids as suspending liquid. The analysis is carried out by extending the theory developed for a Newtonian constitutive law (Inglis et al. Lab Chip 6:655–658, 2006) to account for fluid shear-thinning. 3-D finite element simulations are performed to compute the dynamics of a spherical particle flowing through the deterministic ratchet. The results show that fluid shear-thinning, by altering the flow field between the obstacles, contributes to decrease the critical particle diameter as compared to the Newtonian case. Numerical simulations demonstrate that tunability of the critical separation size can be achieved by using the flow rate as control parameter. A design formula, relating the separation diameter to the fluid rheology and the relevant geometrical parameters of the device, is derived. Such a formula, originally developed for a power-law model, is proved to work for non-Newtonian liquids with a general viscosity trend. 相似文献
54.
Alfredo De Rossi Gaetano Assanto Stefano Trillo William E. Torruellas 《Optics Communications》1998,150(1-6):390-398
We have identified a family of (2+1)D spatial solitary waves which can stably propagate in bulk media in the presence of coexisting diffraction, self-focusing Kerr and quadratic nonlinearities. In a conspicuous range of excitation conditions close to the stationary solutions, the emerging wavepackets are immune to the detrimental occurrence of filamentation and collapse, typical of pure Kerr media. The presence of a second-order contribution to the cubic nonlinear response is, therefore, able to prevent optical damage in applications relying on self-guidance. We show that the cross-phase modulation plays an important effect on stability. Our estimate shows that the effects of the cubic susceptibility cannot be neglected below a certain beam size in realistic crystals (e.g. KTP or similar). 相似文献
55.
We briefly describe how to introduce the basic notions of noncommutative differential geometry on the 3-dim quantum space covariant under the quantum group of rotations SO
q(3). 相似文献
56.
57.
We propose a model in which a recently reported modulation in the decay of the hydrogenlike ions 140Pr58+, 142Pm60+ and 122I52+ arises from the coupling of rotation to the spin of electron and nucleus. The model shows that the spin–spin coupling of electron and nucleus does not contribute to the modulation and predicts that the anomaly cannot be observed if the motion of the ions is rectilinear, or if the ions are stopped in a target. It also supports the notion that the modulation frequency is proportional to the inverse of the atomic mass and that no modulation is expected for the β+-decay. The model predicts that for He-like ions the modulation is still present. 相似文献
58.
Using diffusion Monte Carlo simulations we have investigated the ground state of a symmetric electron-hole bilayer and determined its phase diagram at T = 0. We find clear evidence of an excitonic condensate, whose stability however is affected by an in-layer electronic correlation. This stabilizes the electron-hole plasma at large values of the density or interlayer distance, and the Wigner crystal at low density and large distance. We have also estimated pair correlation functions and low-order density matrices to give a microscopic characterization of correlations as well as to try and estimate the condensate fraction. 相似文献
59.
Gaetano Fiore 《Communications in Mathematical Physics》1995,169(3):475-500
We realize the Hopf algebraU
q–1
(so(N)) as an algebra of differential operators on the quantum Euclidean spaceR
q
N
. The generators are suitableq-deformed analogs of the angular momentum components on ordinaryR
N
. The algebra Fun(R
q
N
) of functions onR
q
N
splits into a direct sum of irreducible vector representations ofU
q–1
(so(N)); the latter are explicitly constructed as highest weight representations. 相似文献
60.
Gaetano Zingone 《Meccanica》1972,7(2):117-123
Summary The limit analysis of indefinite plates resting on a continuous elastoplastic medium and subjected to a load distributed over a partial surface with a circular boundary yields the fundamental equation governing the problem. Minimum conditions are set and the solution that supplies the collapse load of the plate-soil system is found by variational calculus.
This research was supported by the CNR (National Research Council). 相似文献
Sommario Si analizza lo stato limite delle piastre indefinite, appoggiate su un mezzo elastoplastico continuo e sottoposte a carico ripartito su una superficie parziale a contorno circolare, pervenendo all'equazione fondamentale che regge il problemaImponendo quindi delle condizioni minimizzanti, si trova, tramite il calcolo variazionale, la soluzione che fornisce il carico di collasso del sistema piastra-suolo.
This research was supported by the CNR (National Research Council). 相似文献