全文获取类型
收费全文 | 389篇 |
免费 | 2篇 |
专业分类
化学 | 171篇 |
晶体学 | 7篇 |
力学 | 12篇 |
数学 | 36篇 |
物理学 | 165篇 |
出版年
2023年 | 4篇 |
2021年 | 10篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2016年 | 7篇 |
2015年 | 11篇 |
2014年 | 8篇 |
2013年 | 7篇 |
2012年 | 15篇 |
2011年 | 19篇 |
2010年 | 13篇 |
2009年 | 15篇 |
2008年 | 18篇 |
2007年 | 23篇 |
2006年 | 21篇 |
2005年 | 13篇 |
2004年 | 18篇 |
2003年 | 12篇 |
2002年 | 12篇 |
2001年 | 11篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1974年 | 7篇 |
1973年 | 4篇 |
1971年 | 2篇 |
1960年 | 2篇 |
排序方式: 共有391条查询结果,搜索用时 234 毫秒
51.
Detailed predictions of QCD on transverse momentum distributions of jets in leptoproduction are presented. The average p⊥2 is found to be asymptotically proportional to W2 (the hadronic invariant mass squared) with a coefficient function that depends little on x and y. Contributions from gluons in the nucleon are relatively smaller than for σL/σT. 相似文献
52.
Enzo Martinelli 《Annali di Matematica Pura ed Applicata》1955,39(1):335-343
Sunto Si assegna una condizione necessaria e sufficiente per la validità di una formula diCaccioppoli generalizzazione2-dimensionale dell'indicatore logaritmico.
A Mauro Picone nel suo 70mo compleanno. 相似文献
53.
Marco Bochicchio Luciano Maiani Guido Martinelli Giancarlo Rossi Massimo Testa 《Nuclear Physics B》1985,262(2):331-355
The chiral properties of the continuum limit of lattice QCD with Wilson fermions are studied. We show that a partially conserved axial current can be defined, satisfying the usual current algebra requirements.A proper definition of the chiral symmetry order parameter, , is given, and the chiral properties of composite operators are investigated. The implications of our analysis to the lattice determination of non-leptonic weak amplitudes are also discussed. 相似文献
54.
Large deviations and Lifshitz singularity of the integrated density of states of random Hamiltonians
We consider the integrated density of states (IDS) ρ∞(λ) of random Hamiltonian Hω=?Δ+Vω, Vω being a random field on ? d which satisfies a mixing condition. We prove that the probability of large fluctuations of the finite volume IDS |Λ|?1ρ(λ, HΛ(ω)), Λ ? ? d , around the thermodynamic limit ρ∞(λ) is bounded from above by exp {?k|Λ|},k>0. In this case ρ∞(λ) can be recovered from a variational principle. Furthermore we show the existence of a Lifshitztype of singularity of ρ∞(λ) as λ → 0+ in the case where Vω is non-negative. More precisely we prove the following bound: ρ∞(λ)≦exp(?kλ?d/2) as λ → 0+ k>0. This last result is then discussed in some examples. 相似文献
55.
We calculate the quantum correlations existing among the three output fields (pump, signal, and idler) of a triply resonant nondegenerate optical parametric oscillator operating above threshold. By applying the standard criteria [P. van Loock and A. Furusawa, Phys. Rev. A 67, 052315 (2003)], we show that strong tripartite continuous-variable entanglement is present in this well-known and simple system. Furthermore, since the entanglement is generated directly from a nonlinear process, the three entangled fields can have very different frequencies, opening the way for multicolored quantum information networks. 相似文献
56.
del Amo Sanchez P Lees JP Poireau V Prencipe E Tisserand V Garra Tico J Grauges E Martinelli M Palano A Pappagallo M Eigen G Stugu B Sun L Battaglia M Brown DN Hooberman B Kerth LT Kolomensky YG Lynch G Osipenkov IL Tanabe T Hawkes CM Watson AT Koch H Schroeder T Asgeirsson DJ Hearty C Mattison TS McKenna JA Khan A Randle-Conde A Blinov VE Buzykaev AR Druzhinin VP Golubev VB Onuchin AP Serednyakov SI Skovpen YI Solodov EP Todyshev KY Yushkov AN Bondioli M Curry S Kirkby D Lankford AJ 《Physical review letters》2010,105(17):172001
We present a search for f(J)(2220) production in radiative J/ψ→γf(J)(2220) decays using 460 fb?1 of data collected with the BABAR detector at the SLAC PEP-II e(+)e? collider. The f(J)(2220) is searched for in the decays to K(+)K? and K(S)?K(S)?. No evidence of this resonance is observed, and 90% confidence level upper limits on the product of the branching fractions for J/ψ→γf(J)(2220) and f(J)(2220)→K(+)K?(K(S)?K(S)?) as a function of spin and helicity are set at the level of 10??, below the central values reported by the Mark III experiment. 相似文献
57.
Summary: Chitosan films and microspheres were prepared and their surfaces were functionalized with first generation dendritic molecules. The films were modified by Weisocyanate dendron, while Behera's and bis Behera's amine dendrons were used to modify the microspheres. Prior to dendronization films were prepared by blending chitosan with 18% of polyvinyl pyrrolidone (PVP), and casting the resulting mixture. The degree of dendronization reached was 28%. The microspheres were prepared by coacervation/precipitation, after which the surfaces were activated with either epychlorohydrine (ECH) or 1,4-butanediol diglycidyl ether (BDGE). The oxirane groups were utilized to form covalent bonds between chitosan and dendrons. The degree of dendronization yielded with Behera's amine was 60% for both activating agents. When bis Behera's amine was used, the dendronization reached values of 15 and 21% when ECH or BDGE were used, respectively. The dendronized products were characterized through spectroscopic and microscopic studies and by determination of swelling indexes. Only one of the surfaces was dendronized in every film, which therefore presented a hydrophobic and a hydrophilic surface. Since these films maintain the properties of chitosan, they offer interesting potential as dressings for exuding wounds. The different surfaces make the microspheres potentially applicable as carriers for delivery and controlled release of drugs. 相似文献
58.
59.
We present a framework for sequential decision making in problems described by graphical models. The setting is given by dependent discrete random variables with associated costs or revenues. In our examples, the dependent variables are the potential outcomes (oil, gas or dry) when drilling a petroleum well. The goal is to develop an optimal selection strategy of wells that incorporates a chosen utility function within an approximated dynamic programming scheme. We propose and compare different approximations, from naive and myopic heuristics to more complex look-ahead schemes, and we discuss their computational properties. We apply these strategies to oil exploration over multiple prospects modeled by a directed acyclic graph, and to a reservoir drilling decision problem modeled by a Markov random field. The results show that the suggested strategies clearly improve the naive or myopic constructions used in petroleum industry today. This is useful for decision makers planning petroleum exploration policies. 相似文献
60.
A reconfigurable coupled-resonator optical waveguide made of a few directly coupled ring resonators is employed to control the delay of data streams modulated at tens of gigabits per second. A delay of 8 bit lengths (1 optical byte) with a small pulse broadening and 1 dB/bit fractional loss is achieved by using only eight rings. The limiting role of waveguide loss and spurious backreflections is experimentally investigated. The high storage efficiency (1 bit/ring) of the device enables an easy, reliable, hitless, and relatively low-power-consuming management of the delay. A higher storage efficiency is demonstrated to be associated to an unavoidable higher pulse distortion. 相似文献