全文获取类型
收费全文 | 235篇 |
免费 | 18篇 |
国内免费 | 20篇 |
专业分类
化学 | 137篇 |
晶体学 | 2篇 |
力学 | 3篇 |
数学 | 29篇 |
物理学 | 102篇 |
出版年
2022年 | 2篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 1篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2013年 | 9篇 |
2012年 | 8篇 |
2011年 | 17篇 |
2010年 | 3篇 |
2009年 | 8篇 |
2008年 | 19篇 |
2007年 | 15篇 |
2006年 | 13篇 |
2005年 | 11篇 |
2004年 | 13篇 |
2003年 | 12篇 |
2002年 | 21篇 |
2001年 | 13篇 |
2000年 | 12篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1965年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有273条查询结果,搜索用时 15 毫秒
161.
LUCIAE, a hadronic and string cascade model and its corresponding event generator are used to analyse strangeness production singly and multiply in p-Pb and Pb-Pb collisions at 158 A GeV. Spectra of multiplicity and transverse mass for single (Λ, Λ) and multiple (Ξ-, Ξ-, Ω-, Ω-) strangeness are given. In LUCIAE model it suggests a physical mechanism, i.e. the dependence of the strange quark suppression factor on incident energy, projectile mass and centrality of colliding system might result in increase of yield of strange particles with increasing the above three parameters. Calculations from the model reconstruct well the WA97 experimental data: increase of yield of strange particles with increasing centrality and increase of strangeness enhancement with increasing number of strange quarks, in relativistic nucleus-nucleus collisions. 相似文献
162.
Asymptotic analysis of the problem describing deformation ofa thin cylindrical plate with clamped lateral side is performed.The problem is considered under the most general statement withthe plate being laminated and consisting of an arbitrary numberof nonhomogeneous and anisotropic (21 elastic moduli) layers.Explicit integral representations of the differential operatorswhich form the two-dimensional model of the plate are derived.In the case when the elastic moduli of each of the layers areconstant, these integral representations turn into algebraicones. The asymptotic procedure is justified with the help ofa weighted inequality of Korn's type. The error estimates obtainedgive a rigorous mathematical proof of both of Kirchhoff's hypotheses(kinematic and static) and shed light on the well-known intrinsicinconsistency of two of the hypotheses. 相似文献
163.
Asher Yahalom 《Entropy (Basel, Switzerland)》2022,24(12)
An electron moving at velocities much lower that the speed of light with a spin, is described by a wave function which is a solution of Pauli’s equation. It has been demonstrated that this system can be viewed as a vortical fluid which has remarkable similarities but also differences with classical ideal flows. In this respect, it was shown that the internal energy of the Pauli fluid can be interpreted, to some degree, as Fisher Information. In previous work on this subject, electromagnetic fields which are represented by a vector potential were ignored, here we remove this limitation and study the system under general electromagnetic interaction. 相似文献
164.
We provide a survey of past research and a list of open problems regarding central simple algebras and the Brauer group over
a field, intended both for experts and for beginners. 相似文献
165.
Daniel A. Lutterman Laurie A. Lazinski-Melanson Yogen Asher Dean H. Johnston Judith C. Gallucci Claudia Turro 《Journal of photochemistry and photobiology. A, Chemistry》2011,217(1):100-107
Two new Ru(II) complexes, [Ru(bpy)2(1-COO-iqu)]+ (2; bpy = 2,2′-bipyridine, 1-COO-iqu? = isoquinoline-1-carboxylate) and [Ru(bpy)2(3-COO-iqu)]+ (3; 3-COO-iqu? = isoquinoline-3-carboxylate), were prepared and their crystal structures solved. The ground and excited state properties of 2 and 3 were characterized and compared to those of [Ru(bpy)3]2+ (1). The presence of the oxygen atom in the Ru(II) coordination sphere makes 2 and 3 easier to oxidize than 1. The Ru → bpy MLCT absorption and emission of 2 and 3 are red-shifted relative to that of 1 in CH2Cl2, and the E00 energies were estimated to be 1.89 eV and 1.95 eV from the low temperature emission of 2 and 3, resulting in excited state oxidation potentials of ?1.03 V and ?1.10 V vs SCE, respectively. In addition to the short-lived emissive 3MLCT state, a long-lived species is observed in the transient absorption of 3 in DMSO (τ = 49 μs) and pyridine (τ = 44 μs), assigned to a solvent-coordinated complex. This intermediate is not observed for 3 in non-polar solvents or for 2. The absence of the solvent coordinated intermediate in 2 is explained by the stronger Ru–O bond afforded by the lower conjugation in that extends onto the carboxylic acid in the 1-COO-iquo?ligand, compared to that in the 3-COO-iqu?ligand in 3. Transient absorption experiments also show that the 3MLCT excited state of 3 is able to reduce methyl viologen. 相似文献
166.
Infrared multiphoton photodissociation (IRMPD) in a quadrupole ion trap is not selective for a parent ion. Product ions are
decreased in abundance by continuous sequential dissociation and may be lost below the low mass cut-off. The IRMPD process
is made selective by resonantly exciting trapped ions into an axially offset laser path. Product ions form and collisionally
relax out of the laser path to accumulate in the center of the trap. The technique, termed selective broadband (SB) IRMPD,
limits sequential dissociation to preserve first generation product ion abundance. The abundances of larger product ions are
maximized by completely dissociating the parent ion, but continuous sequential dissociation does not form small product ions
below the low mass cut-off associated with conventional IRMPD. Smaller product ions are further increased in abundance in
another tandem mass spectrum by performing sequential stages of SB-IRMPD, adjusting the trapping rf amplitude to dissociate
larger product ions at the same qz range. Thermal assistance is used to perform SB-IRMPD at higher bath gas pressures for increased sensitivity. 相似文献
167.
In this paper, density functional computations have been applied to the structural, elastic and electronic properties of ternary transition metal diborides Re0.5Ir0.5B2, Re0.5Tc0.5B2, Os0.5W0.5B2 and Os0.5Ru0.5B2 in hexagonal (P63/mmc) and orthorhombic (Pmmn) structures with both local density approximation and generalized gradient approximation. LDA gives smaller lattice parameters and larger elastic moduli than GGA. Both results show that the hexagonal ones are more stable than orthorhombic ones except Os0.5Ru0.5B2. Moreover, the hexagonal structure has superior elastic property than orthorhombic one. Generally speaking, the calculated elastic moduli of Re0.5Ir0.5B2 and Os0.5Ru0.5B2 are smaller than those values of Re0.5Tc0.5B2 and Os0.5W0.5B2 within the same structure because of the filling of antibonding states. The relativistic effects result in weaker bonds of Tc-B (Ru-B) than those of Re-B (Os-B). All the diborides are ultra-incompressible. Re0.5Tc0.5B2 has the largest shear modulus and it is a promising superhard diboride like Os0.5W0.5B2. The elastic properties are in high correlation with the bond strength. The shear moduli are more sensitive than the bulk moduli to the bond strength. 相似文献
168.
Sheldon E. Cremer John M. Cowles Asher Gamliel 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):369-372
Abstract The title compounds and their derivatives have been prepared in good yield. Several of the synthetic steps are novel and have general applicability. Isomer assignments for these materials were based upon nmr and x-ray data. A two bond phosphorus-carbon coupling Karplus relation has been established for phosphines and applied to the systems under investigation. Extensive stereochemical studies were conducted. The conformational energy barrier in cis-“phosphadecalin” (2) was estimated to be 12.3–13.6 kcal/mol. Hydroxide ion attack on cis-phosphonium salt 5 went with retention at phosphorus, while cis or trans 4 proceeded with considerable inversion. Nucleophilic displacements on derivatives of phosphorinane generally went with inversion of configuration. 相似文献
169.
催化光度法测定钒已有报道[1~3],在0.45 mol·L-1磷酸介质及加热条件下,过氧化氢氧化溴甲酚紫褪色反应非常缓慢,而痕量钒对此反应具有较高的催化活性,且在一定浓度范围内,钒量与褪色反应程度呈线性关系,据此可建立测定痕量钒的方法.方法的检出限为1.9×10-6g·L-1,测定范围为0.003~1.8 mg·L-1.方法操作简便,重现性好,用于钢样中痕量钒的测定,结果满意. 相似文献
170.
We consider a classical Hamiltonian H = Lz+Mz+LxMx, where the components of L and M satisfy Poisson brackets similar to those of angular momenta. There are three constants of motion: H, L2 and M2. By studying Poincaré surfaces of section, we find that the motion is regular when L2 or M2 is very small or very large. It is chaotic when both L2 and M2 have intermediate values. The interest of this model lies in its quantization, which involves finite matrices only. 相似文献