全文获取类型
收费全文 | 1187篇 |
免费 | 33篇 |
国内免费 | 1篇 |
专业分类
化学 | 814篇 |
晶体学 | 4篇 |
力学 | 55篇 |
数学 | 177篇 |
物理学 | 171篇 |
出版年
2023年 | 10篇 |
2022年 | 34篇 |
2021年 | 27篇 |
2020年 | 20篇 |
2019年 | 27篇 |
2018年 | 18篇 |
2017年 | 19篇 |
2016年 | 45篇 |
2015年 | 35篇 |
2014年 | 30篇 |
2013年 | 76篇 |
2012年 | 66篇 |
2011年 | 78篇 |
2010年 | 47篇 |
2009年 | 43篇 |
2008年 | 65篇 |
2007年 | 64篇 |
2006年 | 66篇 |
2005年 | 54篇 |
2004年 | 39篇 |
2003年 | 45篇 |
2002年 | 42篇 |
2001年 | 7篇 |
2000年 | 9篇 |
1999年 | 7篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 11篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 12篇 |
1988年 | 9篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 12篇 |
1984年 | 13篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 11篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1975年 | 12篇 |
1974年 | 7篇 |
1973年 | 4篇 |
排序方式: 共有1221条查询结果,搜索用时 15 毫秒
91.
Different types of fused-silica capillaries of 75 microm inside diameter (ID) were packed, namely type A and B, and evaluated for the direct resolution of racemates of several basic compounds by enantioselective capillary electrochromatography (e-CEC). Type A was packed with a chiral stationary phase (CSP) containing teicoplanin (TE) mixed with silica microparticles (3:1 w/w) while type B contained only the TE-CSP. In both cases, particles of different sizes (3.5 and 5 microm ID) were employed. A polar-organic mobile phase containing methanol-acetonitrile (60-40% v/v and 0.05% w/v ammonium acetate was used. Several beta-blockers (alprenolol, oxprenolol, metoprolol, pindolol, salbutamol, propranolol, atenolol, acebutolol) were baseline-enantioresolved with both capillary types, in very short times. 相似文献
92.
93.
We report the first example of a molecular switch of multifunctional dipolar ruthenium(III/II) pentaammine-N-methyl-(4,4'-bipyridinium) complexes, exclusively driven by light. This is achieved by using a two-phase (water/benzene) system in which RuIII/II complexes are soluble only in the water phase. The reversible redox switching is triggered by the selective irradiation of the water and the benzene compartments with 254 and 528 nm light, respectively. 相似文献
94.
Framed Discs Operads and Batalin-Vilkovisky Algebras 总被引:1,自引:0,他引:1
95.
We analyze in some detail the course that Ettore Majorana gave on theoretical physics at the University of Naples between
January and March 1938, just prior to his mysterious disappearance. We discuss, in particular, the recently discovered Moreno
Lecture Notes, in which all of Majorana’s lectures are recorded, six of which are not present in those that are preserved
in the Domus Galilaeana in Pisa, Italy.
Antonino Drago is a retired professor of history of physics at the University of Naples “Federico II.” Salvatore Esposito
is a researcher on theoretical physics and history of physics at the University of Naples “Federico II.” 相似文献
96.
Salvatore Giuffrida Guglielmo G. Condorelli Lucia L. Costanzo Giorgio Ventimiglia Raffaella Lo Nigro Maria Favazza Enrico Votrico Corrado Bongiorno Ignazio L. Fragalà 《Journal of nanoparticle research》2007,9(4):611-619
Liquid Phase Photo-Deposition (LPPD) technique has been used to obtain both colloidal particles and thin films of metallic
and chloride nickel from solutions of only precursor Ni(acac)2 (acac=2,4-pentandionato). Metallic nickel was obtained from ethanol solutions by direct nickel(II) photoreduction at 254 nm
and by acetone sensitised reaction at 300 nm. In this latter process the rate was higher than in the first one. NiCl2 was formed from CCl4 solution by a solvent-initiated reaction. TEM analysis, performed on colloidal particles of nickel, showed that their dimensions
are in the range 2–4 nm. The films did not present carbon contamination and were characterized by AFM, XPS and GIXRD. Metallic
films consisted of particles of 20–40 nm that are the result of the aggregation of smaller crystallites (4–5 nm). Larger agglomerations
(around 200 nm) have been observed for NiCl2 films. 相似文献
97.
98.
Vincenzo Cunsolo Elisa Cairone Rosaria Saletti Vera Muccilli Salvatore Foti 《Rapid communications in mass spectrometry : RCM》2009,23(13):1907-1916
Two coeluting components, with experimentally measured Mr values of 25529 and 24606 Da, were identified by reversed‐phase high‐performance liquid chromatography (RP‐HPLC) and mass spectrometric analysis in the dephosphorylated casein fraction of a milk sample collected from an individual donkey belonging to the Ragusano breed of the east of Sicily. By coupling enzymatic digestions, matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) and RP‐HPLC/nano‐electrospray ionization tandem mass spectrometry (nESI‐MS/MS) analysis, the two proteins were identified as donkey β‐CNs and their sequences characterized completely, using the two known β‐CNs from mare as references. The two donkey β‐CNs, showing a mass difference of 923 Da, differ by the presence of the domain E27SITHINK34 in the full‐length component (Mr 25529 Da). In comparison with the mare's β‐CNs used as reference, they present nine amino acid substitutions: L→S37, R→H52, S→N81, P→V84, L→V91, R→Q203, P→L/I206, L→F210 and A→P219. Together, these substitutions account for the increase of 18 Da in the Mr of the donkey β‐CNs with respect to the counterparts from the mare. The molecular mass determination by ESI‐MS for the phosphorylated proteins showed that the full‐length component was composed of highly multi‐phosphorylated isoforms with five to seven phosphate groups. By analogy with the homologous mare's β‐CNs, the full‐length (226 amino acids) β‐CN was termed variant A, whereas the shorter (218 amino acids) β‐CN was termed variant AΔ5. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
99.
Salvatore Capozziello Giuseppe Basini Mariafelicia De Laurentis 《The European Physical Journal C - Particles and Fields》2011,71(6):1679
We derive a geometrical approach to produce the mass of particles that could be suitably tested at LHC. Starting from a 5D
unification scheme, we show that all the known interactions could be suitably deduced as an induced symmetry breaking of the
non-unitary GL(4)-group of diffeomorphisms. The deformations inducing such a breaking act as vector bosons that, depending on the gravitational
mass states, can assume the role of interaction bosons like gluons, electroweak bosons or photon. The further gravitational
degrees of freedom, emerging from the reduction mechanism in 4D, eliminate the hierarchy problem since generate a cutoff comparable
with electroweak one at TeV scales. In this “economic” scheme, gravity should induce the other interactions in a non-perturbative
way. 相似文献