全文获取类型
收费全文 | 1003篇 |
免费 | 22篇 |
国内免费 | 6篇 |
专业分类
化学 | 628篇 |
晶体学 | 8篇 |
力学 | 48篇 |
数学 | 156篇 |
物理学 | 191篇 |
出版年
2023年 | 5篇 |
2021年 | 25篇 |
2020年 | 16篇 |
2019年 | 16篇 |
2018年 | 7篇 |
2017年 | 8篇 |
2016年 | 37篇 |
2015年 | 24篇 |
2014年 | 22篇 |
2013年 | 49篇 |
2012年 | 44篇 |
2011年 | 70篇 |
2010年 | 25篇 |
2009年 | 39篇 |
2008年 | 58篇 |
2007年 | 68篇 |
2006年 | 38篇 |
2005年 | 36篇 |
2004年 | 32篇 |
2003年 | 27篇 |
2002年 | 24篇 |
2001年 | 30篇 |
2000年 | 12篇 |
1999年 | 19篇 |
1998年 | 9篇 |
1997年 | 15篇 |
1996年 | 18篇 |
1995年 | 20篇 |
1994年 | 21篇 |
1993年 | 17篇 |
1992年 | 13篇 |
1991年 | 7篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1988年 | 14篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 13篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 10篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1975年 | 7篇 |
1974年 | 5篇 |
1966年 | 4篇 |
排序方式: 共有1031条查询结果,搜索用时 296 毫秒
61.
A. Akindinov A. Alici P. Antonioli S. Arcelli M. Basile G. Cara Romeo M. Chumakov L. Cifarelli F. Cindolo A. De Caro D. De Gruttola S. De Pasquale M. Fusco Girard C. Guarnaccia D. Hatzifotiadou H.T. Jung W.W. Jung D.W. Kim H.N. Kim J.S. Kim S. Kiselev G. Laurenti K. Lee S.C. Lee E. Lioublev M.L. Luvisetto A. Margotti A. Martemiyanov R. Nania F. Noferini P. Pagano A. Pesci R. Preghenella G. Russo E. Scapparone G. Scioli R. Silvestri Y. Sun I. Vetlitskiy K. Voloshin L. Vorobiev M.C.S. Williams B. Zagreev C. Zampolli A. Zichichi 《The European Physical Journal C - Particles and Fields》2007,50(2):341-352
In this work we explore the possibility to perform “effective energy” studies in very high energy collisions at the CERN large
hadron collider (LHC). In particular, we focus on the possibility to measure in pp collisions the average charged multiplicity
as a function of the effective energy with the ALICE experiment, using its capability to measure the energy of the leading
baryons with the zero degree calorimeters. Analyses of this kind have been done at lower centre-of-mass energies and have
shown that, once the appropriate kinematic variables are chosen, particle production is characterized by universal properties:
no matter the nature of the interacting particles, the final states have identical features. Assuming that this universality
picture can be extended to ion–ion collisions, as suggested by recent results from RHIC experiments, a novel approach based on the scaling hypothesis for limiting
fragmentation has been used to derive the expected charged event multiplicity in AA interactions at LHC. This leads to scenarios
where the multiplicity is significantly lower compared to most of the predictions from the models currently used to describe
high energy AA collisions. A mean charged multiplicity of about 1000–2000 per rapidity unit (at η∼0) is expected for the most
central Pb–Pb collisions at .
In memory of A. Smirnitskiy 相似文献
62.
Glycerol from biodiesel production can be an important industrial feedstock for chemical commodities as it can be used in the food,cosmetic,pharmaceutical and tobacco industries.However,crude glycerol derived from biodiesel production has a low value because of impurities.The purification of this glycerol into a high grade involves high costs and is not economically feasible for small and medium size plants.The glycerol conversion into chlorohydrins was studied using new homogeneous catalysts and hydrochloric acid as chlorination agent.This is an interesting alternative route to epichlorohydrin and then to epoxy resins.The behavior of two series of homologous catalysts,glycolic acid series(glycolic acid,di-glycolic acid and thio-glycolic acid) and amminoacid series(glutamic acid,aspartic acid and cysteine),were investigated for their activity and selectivity.Glycolic acids were more active than amminoacids.The pK_a values had a strong influence on selectivity(mono-chlorohydrins/di-chlorohydrins) for the amminoacid series,which was not observed for the glycolic acids.A kinetic model and reaction mechanism developed in a previous work were used for interpreting the kinetic runs. 相似文献
63.
Aziz Bouymajane Yassine Oulad El Majdoub Francesco Cacciola Marina Russo Fabio Salafia Alessandra Trozzi Fouzia Rhazi Filali Paola Dugo Luigi Mondello 《Molecules (Basel, Switzerland)》2020,25(22)
Olive oil is an important product in the Mediterranean diet, due to its health benefits and sensorial characteristics. Picholine marocaine is the most cultivated variety in Morocco. The present research aims to evaluate the phenolic compounds, vitamin E and fatty acids of commercial Picholine marocaine virgin olive oils (VOOs) from five different North Moroccan provinces (Chefchaouen, Taounate, Errachidia, Beni Mellal and Taza), using HPLC-photodiode array (PDA)/electrospray ionization (ESI)-MS, normal phase (NP)-HPLC/ fluorescence detector (FLD) and GC-flame ionization detector (FID)/MS, respectively. The obtained results showed an average content of 130.0 mg kg−1 of secoiridoids (oleuropein aglycone, 10-hydroxy-oleuropein aglycone and ligstroside aglycone, oleocanthal and oleacein), 108.1 mg kg−1 of phenolic alcohols (tyrosol and hydroxytyrosol), 34.7 mg kg−1 of phenolic acids (caffeic acid, ferulic acid and elenolic acid), and 8.24 mg kg−1 of flavonoids (luteolin, luteolin glucoside, apigenin). With regard to vitamin E, α-tocopherol was the most abundant vitamin E (57.9 mg kg−1), followed by α-tocotrienol (2.5 mg kg−1), γ-tocopherol (4.5 mg kg−1) and β-tocopherol (1.9 mg kg−1), while δ-tocopherol was not detected. Moreover, 14 fatty acids were found and, among them, oleic acid (76.1%), linoleic acid (8.1%) palmitic acid (8.7%) and stearic acid (2.5%) were the major fatty acids detected. Finally, heat map and principal component analysis allowed us to classify the studied provinces in terms of VOO chemical composition: Chefchaouen (tyrosol and hydroxytyrosol), Taounate (oleuropein aglycone), Errachidia (ferulic acid, w-3 and w-6), Beni Mellal (oleocanthal) and Taza (luteolin and oleic acid). 相似文献
64.
P. Ammendola B. Piriou L. Lisi G. Ruoppolo R. Chirone G. Russo 《Experimental Thermal and Fluid Science》2010,34(3):269-274
A dual fixed bed laboratory scale set up has been used to compare the activity of a novel Rh/LaCoO3/Al2O3 catalyst to that of dolomite, olivine and Ni/Al2O3, typical catalysts used in fluidized bed biomass gasification, to convert tars produced during biomass devolatilization stage. The experimental apparatus allows the catalyst to be operated under controlled conditions of temperature and with a real gas mixture obtained by the pyrolysis of the biomass carried out in a separate fixed bed reactor operated under a selected and controlled heating up rate.The proposed catalyst exhibits much better performances than conventional catalysts tested. It is able to completely convert tars and also to strongly decrease coke formation due to its good redox properties. 相似文献
65.
Ho Tony; Martinez-Moreno Juan; Peralta Antonio M.; Russo Bernard 《Journal London Mathematical Society》2002,65(1):85-102
At the regional conference held at the University of California,Irvine, in 1985 [24], Harald Upmeier posed three basic questionsregarding derivations on JB*-triples: (1) Are derivations automatically bounded? (2) When are all bounded derivations inner? (3) Can bounded derivations be approximated by inner derivations? These three questions had all been answered in the binary cases.Question 1 was answered affirmatively by Sakai [17] for C*-algebrasand by Upmeier [23] for JB-algebras. Question 2 was answeredby Sakai [18] and Kadison [12] for von Neumann algebras andby Upmeier [23] for JW-algebras. Question 3 was answered byUpmeier [23] for JB-algebras, and it follows trivially fromthe KadisonSakai answer to question 2 in the case ofC*-algebras. In the ternary case, both question 1 and question 3 were answeredby Barton and Friedman in [3] for complex JB*-triples. In thispaper, we consider question 2 for real and complex JBW*-triplesand question 1 and question 3 for real JB*-triples. A real orcomplex JB*-triple is said to have the inner derivation propertyif every derivation on it is inner. By pure algebra, every finite-dimensionalJB*-triple has the inner derivation property. Our main results,Theorems 2, 3 and 4 and Corollaries 2 and 3 determine whichof the infinite-dimensional real or complex Cartan factors havethe inner derivation property. 相似文献
66.
The Cu(+) and Cu(2+) preferred binding sites on alpha-alanine and their affinity values for this amino acid were determined at the density functional level using three different hybrid exchange correlation potentials and the 6-311++G** basis set. The results demonstrated that the two ions both give stable complexes with alpha-alanine but the stability order of the metalated species and the coordination sites are different depending on the nature of the cation. In particular, the Cu(+)-alpha-alanine ground-state structure is characterized by an eta(2)-N,O coordination with the nitrogen and oxygen atoms belonging to the amino and carbonyl groups, respectively. In contrast, the most stable complex of the Cu(2+)-alpha-alanine system has an eta(2)-O,O coordination with the cation bonded to the -CO(2) (-) moiety of the zwitterionic form of the amino acid. Comparison with the Cu(+) and Cu(2+) affinity values for glycine, computed at the same levels of theory, demonstrated that the relative values do not change significantly as different hybrid functionals are used, although the absolute affinities are strongly influenced by the choice of the hybrid potential. 相似文献
67.
Density functional theory calculations on [LnCp2APh] (Ln = La, Lu; Cp = eta 5-C5H5; A = O, S; Ph = C6H5) suggest that the linearity of the Ln-O-C vectors arises largely as a result of electrostatic repulsion between the alpha carbon and the trivalent metal centre. 相似文献
68.
Mordini A Sbaragli L Valacchi M Russo F Reginato G 《Chemical communications (Cambridge, England)》2002,(7):778-779
Aziridinyl ethers are selectively and easily converted to either amino vinyl ethers or alkoxy allylamines by treatment with mixed metal bases (superbases). 相似文献
69.
T. H. Prettyman C. S. Cooper P. N. Luke P. A. Russo M. Amman D. J. Mercer 《Journal of Radioanalytical and Nuclear Chemistry》1998,233(1-2):257-264
A physics-based approach to gamma-ray response-function generation is presented in which the response of CdZnTe detectors
is modeled from first principles. Numerical modeling is used to generate response functions needed for spectrum analysis for
general detector configurations (e.g., electrode design, detector materials and geometry, and operating conditions). With
numerical modeling, requirements for calibration and characterization are significantly reduced. Elements of the physics-based
model, including gamma-ray transport, charge carrier drift and diffusion, and circuit response, are presented. Calculated
and experimental gamma-ray spectra are compared for a coplanar-grid CdZnTe detector. 相似文献
70.
X. Xu C. P. Grigoropoulos R. E. Russo 《Applied Physics A: Materials Science & Processing》1996,62(1):51-59
A nanosecond-time-resolution pyrometer has been developed for measuring the transient surface temperature of a solid material heated by pulsed excimer-laser irradiation. Fast germanium diodes are employed to capture the transient thermal emission signals in the wavelength range between 1.2 and 1.6 pm. The surface temperature is derived from the measured spectral thermal emission. The directional spectral emissivity is determined in situ by measuring the transient directional spectral reflectivity and applying Kirchhoffs law. The experimental results are in good agreement with numerical thermal modeling predictions. The pyrometric thermal emission measurement also yields the solid/liquid interface temperature during the pulsed excimer-laser-induced melting. The relation between the measured interface superheating temperature and the interface velocity reveals the melting kinetic relation during the high-power, short-pulse laser-induced phase-change processes. 相似文献