全文获取类型
收费全文 | 1008篇 |
免费 | 25篇 |
国内免费 | 57篇 |
专业分类
化学 | 371篇 |
晶体学 | 1篇 |
力学 | 23篇 |
综合类 | 2篇 |
数学 | 140篇 |
物理学 | 553篇 |
出版年
2022年 | 8篇 |
2021年 | 34篇 |
2020年 | 13篇 |
2019年 | 7篇 |
2018年 | 9篇 |
2017年 | 14篇 |
2016年 | 27篇 |
2015年 | 11篇 |
2014年 | 20篇 |
2013年 | 21篇 |
2012年 | 22篇 |
2011年 | 52篇 |
2010年 | 43篇 |
2009年 | 37篇 |
2008年 | 15篇 |
2007年 | 15篇 |
2006年 | 55篇 |
2005年 | 59篇 |
2004年 | 124篇 |
2003年 | 110篇 |
2002年 | 70篇 |
2001年 | 76篇 |
2000年 | 18篇 |
1999年 | 14篇 |
1998年 | 24篇 |
1997年 | 14篇 |
1996年 | 9篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 24篇 |
1992年 | 19篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 15篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1977年 | 3篇 |
1935年 | 2篇 |
1932年 | 2篇 |
1928年 | 2篇 |
1919年 | 3篇 |
1917年 | 2篇 |
1916年 | 2篇 |
1911年 | 4篇 |
1910年 | 3篇 |
1909年 | 3篇 |
1907年 | 3篇 |
排序方式: 共有1090条查询结果,搜索用时 15 毫秒
61.
Multijet production rates in neutral current deep inelastic scattering have been measured in the range of exchanged boson
virtualities
. The data were taken at the ep collider HERA with centre-of-mass energy
using the ZEUS detector and correspond to an integrated luminosity of
. Jets were identified in the Breit frame using the kT cluster algorithm in the longitudinally invariant inclusive mode. Measurements of differential dijet and trijet cross sections
are presented as functions of jet transverse energy (
), pseudorapidity (
) and Q2 with
and
. Next-to-leading-order QCD calculations describe the data well. The value of the strong coupling constant
, determined from the ratio of the trijet to dijet cross sections, is
.
Received: 1 April 2005, Revised: 28 June 2005, Published online: 30 August 2005 相似文献
62.
The H Collaboration 《The European Physical Journal C - Particles and Fields》2005,38(4):437-445
Results are presented on the photoproduction of isolated prompt photons, inclusively and associated with jets, in the
center of mass energy range 142 < W < 266 GeV. The cross sections are measured for the transverse momentum range of the photons
GeV and for associated jets with E
T
jet > 4.5 GeV. They are measured differentially as a function of
, the pseudorapidities
and
and estimators of the momentum fractions
and x
p
of the incident photon and proton carried by the constituents participating in the hard process. In order to further investigate the underlying dynamics, the angular correlation between the prompt photon and the jet in the transverse plane is studied. Predictions by perturbative QCD calculations in next to leading order are about
below the inclusive prompt photon data after corrections for hadronisation and multiple interactions, but are in reasonable agreement with the results for prompt photons associated with jets. Comparisons with the predictions of the event generators PYTHIA and HERWIG are also presented.Received: 13 July 2004, Revised: 15 November 2004, Published online: 17 December 2004 相似文献
63.
Donné AJ van Gorkom JC Udintsev VS Domier CW Krämer-Flecken A Luhmann NC Schüller FC;TEXTOR Team 《Physical review letters》2005,94(8):085001
Small-scale structures with high poloidal mode numbers (m=10-20) have been observed in the TEXTOR tokamak plasma with pulsed radar reflectometry and an electron cyclotron emission diagnostic, in conjunction with large 2/1 and 1/1 islands. The small islands have a peaked density profile, similar to that of the simultaneously observed large-scale 2/1 islands. This together with the observation that high-frequency density and temperature fluctuations are very pronounced near the X points of the large islands hints to a strongly perturbed magnetic topology around the X points. 相似文献
64.
Liang Y Koslowski HR Kelly FA Tokar MZ Loozen X Bertschinger G Biel W Finken KH Jakubowski MW Krämer-Flecken A Zimmermann O Lehnen M Sergienko G Wolf RC;TEXTOR Team 《Physical review letters》2005,94(10):105003
A significant influence of the dynamic ergodic divertor (DED) on the density limit in TEXTOR has been found. In Ohmic discharges, where without DED detachment normally arises at the density limit, a MARFE (multifaceted asymmetric radiation from the edge) develops when the DED is operated in a static regime. The threshold of the MARFE onset in the neutral beam heated plasmas is increased by applying 1 kHz ac DED at the high-field side. The theoretical predictions based on the parallel energy balance taking poloidal asymmetries into account agree well with the experimental observation. 相似文献
65.
Jochen Lutz The Vinh Ho Richard H. Fish Andreas Schmid 《Journal of organometallic chemistry》2004,689(25):4783-4790
The biocatalytic, regioselective hydroxylation of 2-hydroxybiphenyl to the corresponding catechol was accomplished utilizing the monooxygenase 2-hydroxybiphenyl 3-monooxygenase (HbpA). The necessary natural 1,4-dihydronicotinamde adenine dinucleotide (NADH) co-factor for this biocatalytic process was replaced by a biomimetic co-factor, N-benzyl-1,4-dihydronicotinamide, 1b. The interaction between the flavin (FAD) containing HbpA enzyme and the corresponding biomimetic NADH compound, N-benzyl-1,4-dihdronicotinamide, 1b, for hydride transfer, was shown to readily occur. The in situ recycling of the reduced NADH biomimic 1b from 1a was accomplished with [Cp*Rh(bpy)H](Cl); however, productive coupling of this regeneration reaction to the enzymatic hydroxylation reaction was not totally successful, due to a deactivation process concerning the HbpA enzyme peripheral groups; i.e., -SH or -NH2 possibly reacting with the precatalyst, [Cp*Rh(bpy)(H2O)](Cl)2, and thus inhibiting the co-factor regeneration process. The deactivation mechanism was studied, and a promising strategy of derivatizing these peripheral -SH or -NH2 groups with a polymer containing epoxide was successful in circumventing the undesired interaction between HbpA and the precatalyst. This latter strategy allowed tandem co-factor regeneration using 1a or 2a, [Cp*Rh(bpy)(H2O)](Cl)2, and formate ion, in conjunction with the polymer bound, FAD containing HbpA enzyme to provide the catechol product. 相似文献
66.
The EDDA Collaboration 《The European Physical Journal A - Hadrons and Nuclei》2004,22(1):125-148
We have measured differential cross-sections for
elastic scattering with internal fiber targets in the recirculating beam of the proton synchrotron COSY. Measurements were made continuously during acceleration for projectile kinetic energies between 0.23 and 2.59 GeV in the angular range
. Details of the apparatus and the data analysis are given and the resulting excitation functions and angular distributions presented. The precision of each data point is typically better than 4%, and a relative normalization uncertainty of only 2.5% within an excitation function has been reached. The impact on phase shift analysis as well as upper bounds on possible resonant contributions in lower partial waves are discussed.Received: 24 March 2004, Published online: 19 October 2004PACS:
25.40.Cm Elastic proton scattering - 13.75.Cs Nucleon-nucleon interactions (including antinucleons, deuterons, etc.) - 13.85.Dz Elastic scattering - 21.30.-x Nuclear forces 相似文献
67.
The H Collaboration 《The European Physical Journal C - Particles and Fields》2004,37(2):141-159
Triple differential dijet cross sections in
interactions are presented in the region of photon virtualities 2 < Q
2 < 80 GeV2, inelasticities 0.1 < y < 0.85, jet transverse energies E
*
T 1 > 7 GeV, E
*
T 2 > 5 GeV, and pseudorapidities
. The measurements are made in the
centre-of-mass frame, using an integrated luminosity of 57 pb-1. The data are compared with NLO QCD calculations and LO Monte Carlo programs with and without a resolved virtual photon contribution. NLO QCD calculations fail to describe the region of low Q
2 and low jet transverse energies, in contrast to a LO Monte Carlo generator which includes direct and resolved photon interactions with both transversely and longitudinally polarised photons. Initial and final state parton showers are tested as a mechanism for including higher order QCD effects in low E
T
jet production.Received: 13 January 2004, Revised: 21 July 2004, Published online: 18 August 2004 相似文献
68.
Searches for neutral Higgs bosons produced at LEP in association with Z bosons, in pairs and in the Yukawa process are presented in this paper. Higgs boson decays into b quarks,
leptons, or other Higgs bosons are considered, giving rise to four-b, four-b + jets, six-b and four-
final states, as well as mixed modes with b quarks and
leptons. The whole mass domain kinematically accessible at LEP in these topologies is searched. The analysed data set covers both the LEP1 and LEP2 energy ranges and exploits most of the luminosity recorded by the DELPHI experiment. No convincing evidence for a signal is found, and results are presented in the form of mass-dependent upper bounds on coupling factors (in units of model-independent reference cross-sections) for all processes, allowing interpretation of the data in a large class of models.Received: 26 October 2003, Revised: 1 September 2004, Published online: 28 October 2004 相似文献
69.
Approximately 438 pb-1 of e + e- data from the OPAL detector, taken with the LEP collider running at centre-of-mass energies of 192-209 GeV, are analyzed to search for evidence of chargino pair production,
, or neutralino associated production,
. Limits are set at the 95% confidence level on the product of the cross-section for the process
and its branching ratios to topologies containing jets and missing energy, or jets with a lepton and missing energy, and on the product of the cross-section for
and its branching ratio to jets. R-parity conservation is assumed throughout this paper. When these results are interpreted in the context of the Constrained Minimal Supersymmetric Standard Model, limits are also set on the masses of the
and
, and regions of the parameter space of the model are ruled out. Nearly model-independent limits are also set at the 95% confidence level on
with the assumption that each chargino decays via a W boson, and on
with the
assumed to decay via a Z0.Received: 15 December 2003, Revised: 16 February 2004, Published online: 23 April 2004 相似文献
70.
A second workshop on small-x physics, within the Small-x Collaboration, was held in Lund in June 2002 with the aim of over-viewing recent theoretical progress in this area and summarizing the experimental status.Received: 23 December 2003, Published online: 30 April 2004This paper is dedicated to the memory of Jan Kwieciski, who died unexpectedly on August 29, 2003. 相似文献