全文获取类型
收费全文 | 2010篇 |
免费 | 66篇 |
国内免费 | 14篇 |
专业分类
化学 | 1429篇 |
晶体学 | 10篇 |
力学 | 52篇 |
数学 | 208篇 |
物理学 | 391篇 |
出版年
2022年 | 12篇 |
2021年 | 23篇 |
2020年 | 25篇 |
2019年 | 36篇 |
2018年 | 19篇 |
2017年 | 11篇 |
2016年 | 37篇 |
2015年 | 36篇 |
2014年 | 71篇 |
2013年 | 90篇 |
2012年 | 102篇 |
2011年 | 139篇 |
2010年 | 58篇 |
2009年 | 63篇 |
2008年 | 111篇 |
2007年 | 105篇 |
2006年 | 100篇 |
2005年 | 84篇 |
2004年 | 69篇 |
2003年 | 46篇 |
2002年 | 57篇 |
2001年 | 28篇 |
2000年 | 34篇 |
1999年 | 28篇 |
1998年 | 19篇 |
1997年 | 14篇 |
1996年 | 27篇 |
1995年 | 21篇 |
1994年 | 25篇 |
1993年 | 20篇 |
1992年 | 12篇 |
1991年 | 15篇 |
1990年 | 29篇 |
1989年 | 15篇 |
1988年 | 22篇 |
1987年 | 16篇 |
1986年 | 15篇 |
1985年 | 24篇 |
1984年 | 29篇 |
1983年 | 22篇 |
1982年 | 25篇 |
1981年 | 24篇 |
1980年 | 24篇 |
1979年 | 32篇 |
1978年 | 35篇 |
1977年 | 35篇 |
1976年 | 20篇 |
1975年 | 24篇 |
1974年 | 25篇 |
1973年 | 25篇 |
排序方式: 共有2090条查询结果,搜索用时 328 毫秒
31.
During electrolysis of molten KF-2HF, strongly adherent fluorine bubbles are generated at the surface of carbon anode. The current was passing even if the horizontal anode was fully covered with gas film. The formation and growth of gas bubbles were studied by transient electrochemical techniques. It was observed that the fluorine bubbles do not have the spherical cap shape predicted by the classical theory. The curvature radius of the interface profile is not constant, the edge of the bubble being flat with a contact angle close to zero. The results are interpreted in the frame of a model which takes into account the predominant role of the interfacial properties. 相似文献
32.
Hiroshi Ito Vladimir Marousek Conrad Schuerch 《Journal of polymer science. Part A, Polymer chemistry》1979,17(5):1299-1307
1,6-Anhydro-2,3,4-tri-O-(p-methylbenzyl)-ß-D -galactopyranose (TXGal,M1) has been copolymerized with 1,6-anhydro-2,3,4-tri-O-benzyl-ß-D -mannopyranose (TBMan,M2), the products characterized by NMR, specific rotation, and viscosity, and the reactivity ratios calculated. The reactivity ratios r1 = 0.37 ± 0.15 and r2 = 38 ± 4 indicate that the anhydromannose derivative is about 100 times as reactive as that of anhydrogalactose. A comparison of glucose, mannose, and galactose copolymerizations suggests that the reactivity differences of the three propagating cations are comparatively small and the reactivity differences of the monomers large. This result is consistent with a mechanism proposed earlier. Methyl substitution on the aromatic rings of the p-xylyl groups inhibits the initiation process significantly relative to benzyl, but propagation only slightly. 相似文献
33.
Edmond Amouyal Bertrand Zidler Patrick Keller Alec Moradpour 《Chemical physics letters》1980,74(2):314-317
Rate constants kq for the quenching of the excited state of Ru(bipy)32+ by a series of viologen salts having different redox potential E have been determined in deaerated aqueous solutions at pH = 5 by laser flash photolysis. The kq values are found to decrease with increasing —E and to correlate with the reaction free-energy change ΔG. Such a correlation is shown to be consistent with the Rehm—Weller model for electron-transfer reactions. 相似文献
34.
A chiral stationary phase (CSP) based on (-)-(18-crown-6)-2,3,11,12-tetracarboxylic acid was evaluated for the direct resolution of the enantiomers of dipeptides and tripeptides. The type and concentration of the acid and the methanol content were optimized with regard to retention time and resolution using Ala-Phe as model peptide. A mobile phase consisting of 10 mM sulfuric acid in 70% aqueous methanol was applied to the separation of a set of 16 structurally diverse dipeptides and tripeptides. Generally, the configuration of the amino acid at the N-terminus determined the enantiomer elution order. With a few exceptions the LL- and LD-enantiomers interacted stronger with the CSP compared to the corresponding DD- or DL-enantiomers. The experimental conditions also allowed the simultaneous separation of all four stereoisomers of Ala-Phe. Addition of ammonium sulfate generally reduced retention times and enantiomer resolution. Addition of triethylamine as modifier led to an overall increase of the retention times while the resolution did not show a general trend, increasing in the case of Ala-Ala but decreasing in the case of Ala-Phe. 相似文献
35.
Firouz Matloubi-Moghandam Peter Rüedi Conrad Hans Eugster 《Helvetica chimica acta》1984,67(1):209-215
Preparation of the First Spiro[(methylcyclopropan)-phenanthrene]-1,3-dione Derivatives by 1,6-Elimination Reactions of Spirocoleons Spirocoleons, e.g. coleon J ( 1 ), on treatment with 1,5-diazabicyclo[4.3.0]non-5-ene (DBN) in aprotic solvents, undergo enolization followed by a rapid 1,6-elimination with formation of the hitherto unknown 2-methyl-spiro[cyclopropane-1,2′(1′H)-phenanthrene]-1′,3′(4′bH)-dione system, e.g. 3 . In protic solvents, base-catalyzed solvolysis of the spirocyclopropane predominates. 相似文献
36.
Tilson JL Naleway C Seth M Shepard R Wagner AF Ermler WC 《The Journal of chemical physics》2004,121(12):5661-5675
A valence full configuration interaction study with a polarized double-zeta quality basis set has been carried out for the lowest 49 electronic states of AmCl(+). The calculations use a pseudopotential treatment for the core electrons and incorporate a one-electron spin-orbit interaction operator. Electrons in the valence s, p, d, and f subshells were included in the active space. The resulting electronic potential energy curves are largely repulsive. The chemical bonding is ionic in character with negligible participation of 5f electrons. The molecular f-f spectroscopy of AmCl(+) arises essentially from an in situ Am(2+) core with states slightly redshifted by the presence of chloride ion. Am(+)+Cl asymptotes which give rise to the few attractive potential energy curves can be predicted by analysis of the f-f spectroscopy of isolated Am(+) and Am(2+). The attractive curves have substantial binding energies, on the order of 75-80 kcal/mol, and are noticeably lower than recent indirect measurements on the isovalent EuCl(+). An independent empirical correlation supports the predicted reduction in AmCl(+) binding energy. The energies of the repulsive curves are strongly dependent on the selection of the underlying atomic orbitals while the energies of the attractive curves do not display this sensitivity. The calculations were carried out using our recently developed parallel spin-orbit configuration interaction software. 相似文献
37.
Bertrand Pierre Broniatowski Michel Marcotorchino Jean-François 《Advances in Data Analysis and Classification》2022,16(4):1069-1093
Advances in Data Analysis and Classification - This paper aims at comparing two coupling approaches as basic layers for building clustering criteria, suited for modularizing and clustering very... 相似文献
38.
Adams MR Aïd S Anthony PL Averill DA Baker MD Baller BR Banerjee A Bhatti AA Bratzler U Braun HM Breidung H Busza W Carroll TJ Clark HL Conrad JM Davisson R Derado I Dhawan SK Dietrich FS Dougherty W Dreyer T Eckardt V Ecker U Erdmann M Faller F Fang GY Figiel J Finlay RW Gebauer HJ Geesaman DF Griffioen KA Guo RS Haas J Halliwell C Hantke D Hicks KH Hughes VW Jackson HE Jancso G Jansen DM Jin Z Kaufman S Kennedy RD Kinney ER Kirk T Kobrak HG Kotwal AV Kunori S Lancaster S Lord JJ Lubatti HJ 《Physical review letters》1995,74(9):1525-1529
39.
McFarland KS Naples D Arroyo CG Auchincloss P de Barbaro P Bazarko AO Bernstein RH Bodek A Bolton T Budd H Conrad J Drucker RB Harris DA Johnson RA Kim JH King BJ Kinnel T Koizumi G Koutsoliotas S Lamm MJ Lefmann WC Marsh W McNulty C Mishra SR Nienaber P Nussbaum M Oreglia MJ Perera L Quintas PZ Romosan A Sakumoto WK Schumm BA Sciulli FJ Seligman WG Shaevitz MH Smith WH Spentzouris P Steiner R Stern EG Vakili M Yang UK 《Physical review letters》1995,75(22):3993-3996
40.
Conrad Newton Per Osland Tai Tsun Wu 《Zeitschrift fur Physik C Particles and Fields》1994,61(3):441-447
As a method of regularization, point splitting has played an essential role in the recent theoretical determination of the masses of the Higgs boson and the top quark. It is the purpose of this paper to put this pointsplitting regularization on a firm basis. The result turns out to be extremely simple: replace the usual vertex factor-ieγ µ in quantum electrodynamics by $$ - ie(\gamma _\mu - \frac{{\not p}}{{p \cdot \delta }}\delta _\mu ),$$ wherep is the momentum of the photon line, andδ µ is the distance for point splitting. No additional vertices are needed. 相似文献