全文获取类型
收费全文 | 1516篇 |
免费 | 29篇 |
国内免费 | 7篇 |
专业分类
化学 | 1070篇 |
晶体学 | 4篇 |
力学 | 65篇 |
数学 | 235篇 |
物理学 | 178篇 |
出版年
2023年 | 9篇 |
2022年 | 34篇 |
2021年 | 40篇 |
2020年 | 30篇 |
2019年 | 27篇 |
2018年 | 23篇 |
2017年 | 24篇 |
2016年 | 44篇 |
2015年 | 21篇 |
2014年 | 41篇 |
2013年 | 69篇 |
2012年 | 68篇 |
2011年 | 90篇 |
2010年 | 52篇 |
2009年 | 58篇 |
2008年 | 82篇 |
2007年 | 106篇 |
2006年 | 97篇 |
2005年 | 76篇 |
2004年 | 87篇 |
2003年 | 51篇 |
2002年 | 53篇 |
2001年 | 14篇 |
2000年 | 20篇 |
1999年 | 10篇 |
1998年 | 17篇 |
1997年 | 14篇 |
1996年 | 14篇 |
1995年 | 20篇 |
1994年 | 9篇 |
1993年 | 14篇 |
1992年 | 12篇 |
1991年 | 17篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 17篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 12篇 |
1984年 | 14篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 16篇 |
1980年 | 16篇 |
1979年 | 17篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 13篇 |
1975年 | 6篇 |
1974年 | 8篇 |
排序方式: 共有1552条查询结果,搜索用时 0 毫秒
81.
Vincenzo Ancona 《Bulletin des Sciences Mathématiques》2006,130(6):525-552
In recent publications, we have defined complexes of differential forms on analytic spaces which are resolutions of the constant sheaf. These complexes were used to prove the existence of a mixed Hodge structure on the cohomology of analytic spaces which possess kählerian hypercoverings, in particular, projective algebraic varieties. We define an exterior product on these forms, which induces the cup product on the cohomology of analytic spaces. The main difficulty is to prove that this exterior product is functorial with respect to morphisms of analytic spaces. This exterior product can be used to prove that the cup product is compatible with the mixed Hodge structure on the cohomology. 相似文献
82.
Dino Boccaletti Francesco Catoni Vincenzo Catoni 《Advances in Applied Clifford Algebras》2007,17(4):611-616
The use of hyperbolic numbers for studying space-time geometry and trigonometry is extended for demonstrating the Frenet’s
formulas in space-time.
By means of this introduction the twin paradox for non-uniformly accelerated motions is formalized in a straightforward way. 相似文献
83.
Nonlinear Oscillations of a Nonresonant Cable under In-Plane Excitation with a Longitudinal Control 总被引:1,自引:0,他引:1
The nonlinear oscillations of a controlled suspended elastic cable under in-plane excitation are considered. Active control realized by longitudinal displacement of one support is introduced in order to reduce the transverse in-plane and out-of-plane vibrations. Linear and quadratic enhanced velocity feedback control laws are chosen and their effects on the cable motion are investigated using a two degree-of-freedom model. Perturbation analysis is performed to determine the in-plane steady-state solutions and their stability under an out-of-plane disturbance. The analysis is extended to the bifurcated two-mode steady-state oscillations in the region of parametric excitation. The dependence of the control effectiveness on the system parameters is investigated in the case of the first symmetric mode and the range of oscillation amplitudes in which the proposed control ensures a dissipation of energy is determined. Although control based only on in-plane response quantities is effective in reducing oscillations with a prevailing in-plane component, addition of out-of-plane measures has to be considered when the motion is characterized by two comparable components. 相似文献
84.
Summary A Riemann-Hilbert boundary value problem, occurring in neutron transport theory, is presented and solved in this note for the case of an infinite straight line and zero index.
Sommario Viene presentato e risolto in questa nota un problema al contorno di Riemann-Hilbert di indice zero e relativo ad un intervallo infinito. Esso ha origine da un problema di diffusione di neutroni, studiato nell'ambito della teoria del trasporto.相似文献
85.
Dr. Vincenzo Grande Dr. Filippo Doria Prof. Dr. Mauro Freccero Prof. Dr. Frank Würthner 《Angewandte Chemie (International ed. in English)》2017,56(26):7520-7524
G-quadruplexes (G4s) are peculiar DNA or RNA tertiary structures that are involved in the regulation of many biological events within mammalian cells, bacteria, and viruses. Although their role as versatile therapeutic targets has been emphasized for 35 years, G4 selectivity over ubiquitous double-stranded DNA/RNA, as well as G4 differentiation by small molecules, still remains challenging. Here, a new amphiphilic dicyanovinyl-substituted squaraine, SQgl , is reported to act as an NIR fluorescent light-up probe discriminating an extensive panel of parallel G4s while it is non-fluorescent in the aggregated state. The squaraine can form an unconventional sandwich π-complex binding two quadruplexes, which leads to a strongly fluorescent (ΦF=0.61) supramolecular architecture. SQgl is highly selective against non-quadruplex and non-parallel G4 sequences without altering their topology, as desired for applications in selective in vivo high-resolution imaging and theranostics. 相似文献
86.
87.
Reversible Activation of Water by an Air- and Moisture-Stable Frustrated Rhodium Nitrogen Lewis Pair
Dr. María Carmona Dr. Joaquina Ferrer Dr. Ricardo Rodríguez Dr. Vincenzo Passarelli Prof. Dr. Fernando J. Lahoz Dr. Pilar García-Orduña Dr. Laura Cañadillas-Delgado Prof. Dr. Daniel Carmona 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(60):13665-13670
[Cp*Rh(κ3N,N′,P- L )][SbF6] (Cp*=C5Me5), bearing a guanidine-derived phosphano ligand L , behaves as a “dormant” frustrated Lewis pair and activates H2 and H2O in a reversible manner. When D2O is employed, a facile H/D exchange at the Cp* ring takes place through sequential C(sp3)−H bond activation. 相似文献
88.
Jeffrey M. Farrell Vincenzo Grande David Schmidt Frank Würthner 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(46):16656-16659
A new strategy is demonstrated for the synthesis of warped, negatively curved, all‐sp2‐carbon π‐scaffolds. Multifold C?C coupling reactions are used to transform a polyaromatic borinic acid into a saddle‐shaped polyaromatic hydrocarbon ( 2 ) bearing two heptagonal rings. Notably, this Schwarzite substructure is synthesized in only two steps from an unfunctionalized alkene. A highly warped structure of 2 was revealed by X‐ray crystallographic studies and pronounced flexibility of this π‐scaffold was ascertained by experimental and computational studies. Compound 2 exhibits excellent solubility, visible range absorption and fluorescence, and readily undergoes two reversible one‐electron oxidations at mild potentials. 相似文献
89.
Vincenzo Barone Alessandro Cafarella Claudio Corianò Marco Guzzi Philip G. Ratcliffe 《Physics letters. [Part B]》2006
We present next-to-leading order predictions for double transverse-spin asymmetries in Drell–Yan dilepton production initiated by proton–antiproton scattering. The kinematic region of the proposed PAX experiment at GSI: 30?s?200 GeV2 and 2?M?7 GeV is examined. The Drell–Yan asymmetries turn out to be large, in the range 20–40%. Measuring these asymmetries would provide the cleanest determination of the quark transversity distributions. 相似文献
90.
We extend a new method to measure possible variation of the speed of light by using Baryon Acoustic Oscillations and the Hubble function onto an inhomogeneous pressure model of the universe. The method relies on the fact that there is a simple relation between the angular diameter distance maximum and the Hubble function (H) evaluated at the same maximum‐condition redshift, which includes the speed of light c. One limit of such a method was the assumption of the vanishing of spatial curvature (though, as it has been shown, a non‐zero curvature has negligible effect). In this paper, apart from taking into account an inhomogeneity, we consider non‐zero spatial curvature and calculate an exact relation between and H. Our main result is the evaluation if current or future missions such as Square Kilometer Array (SKA) can be sensitive enough to detect any spatial variation of c which can in principle be related to the recently observed spatial variation of the fine structure constant (an effect known as α‐dipole). 相似文献