全文获取类型
收费全文 | 226篇 |
免费 | 2篇 |
专业分类
化学 | 133篇 |
晶体学 | 3篇 |
力学 | 2篇 |
数学 | 4篇 |
物理学 | 86篇 |
出版年
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 7篇 |
2013年 | 5篇 |
2012年 | 4篇 |
2011年 | 4篇 |
2010年 | 5篇 |
2009年 | 9篇 |
2008年 | 6篇 |
2007年 | 7篇 |
2006年 | 4篇 |
2005年 | 2篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 10篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 6篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1974年 | 7篇 |
1973年 | 9篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1970年 | 5篇 |
1969年 | 5篇 |
1968年 | 6篇 |
1967年 | 1篇 |
排序方式: 共有228条查询结果,搜索用时 15 毫秒
31.
DC Muddiman AP Null JC Hannis 《Rapid communications in mass spectrometry : RCM》1999,13(12):1201-1204
Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) has been used to determine the mass of a double-stranded 500 base-pair (bp) polymerase chain reaction (PCR) product with an average theoretical mass of the blunt-ended (i.e. unadenylated) species of 308 859.35 Da. The PCR product was generated from the linearized bacteriophage Lambda genome which is a double-stranded template. Utilization of ethanol precipitation in tandem with a rapid microdialysis step to purify and desalt the PCR product was crucial to obtain a precise mass measurement. The PCR product (0.8 pmol/μL) was electrosprayed from a solution containing 75% acetonitrile, 25 mM piperidine, and 25 mM imidazole and was infused at a rate of 200 nL/min. The average molecular mass and the corresponding precision were determined using the charge-states ranging from 172 to 235 net negative charges. The experimental mass and corresponding precision (reported as the 95% confidence interval of the mean) was 309 406 +/- 27 Da (87 ppm). The mass accuracy was compromised due to the fact that the PCR generates multiple products when using Taq polymerase due to the non-template directed 3'-adenylation. This results in a mixture of three PCR products with nearly identical mass (i.e. blunt-ended, mono-adenylated and di-adenylated) with unknown relative abundances that were not resolved in the spectrum. Thus, the experimental mass will be a weighted average of the three species which, under our experimental conditions, reflects a nearly equal concentration of the mono- and di-adenylated species. This report demonstrates that precise mass measurements of PCR products up to 309 kDa (500 bp) can be routinely obtained by ESI-FTICR requiring low femtomole amounts. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
32.
A. Bolshakova I. Boyko G. Chelkov D. Dedovitch A. Elagin M. Gostkin A. Guskov Z. Kroumchtein Y. Nefedov K. Nikolaev A. Zhemchugov F. Dydak J. Wotschack A. De Min V. Ammosov V. Gapienko V. Koreshev A. Semak Y. Sviridov E. Usenko V. Zaets 《The European Physical Journal C - Particles and Fields》2009,63(4):549-609
We report on double-differential inclusive cross sections of the production of secondary protons, charged pions, and deuterons, in the interactions with a 5% λ abs thick stationary tantalum target, of proton and pion beams with momentum from ±3 GeV/c to ±15 GeV/c. Results are given for secondary particles with production angles 20°<θ<125°. They are of particular relevance for the optimization of the design parameters of the proton driver of a neutrino factory. 相似文献
33.
S. V. Shevtsov A. F. Adiyatullin D. E. Sviridov V. I. Kozlovsky P. I. Kuznetsov S. N. Nikolaev V. S. Krivobok 《Physics of the Solid State》2014,56(4):801-811
The photoinduced charge redistribution in Zn(Cd)Se/ZnMgSSe/GaAs quantum-well heterostructures under different conditions of optical excitation has been investigated using scanning probe microscopy and optical spectroscopy in the temperature range from 5 to 300 K. Excitation of the samples by radiation with a photon energy greater than the band gap of Zn(Cd)Se leads to the accumulation of electrons in quantum wells, which is detected using scanning spreading resistance microscopy. For moderate excitation densities (up to 25 W/cm2) and at temperatures ranging from 80 to 100 K, the density of a quasi-two-dimensional electron gas formed in quantum wells is several orders of magnitude higher than the density of electron-hole pairs generated by the excitation radiation. The excess electron concentration in the quantum well leads to a broadening of the exciton resonances and to an increase in the relative intensity of the donor-bound exciton emission line and also determines the increase in the luminescence quantum yield with increasing excitation intensity. An additional illumination with a photon energy less than the band gap of Zn(Cd)Se decreases the concentration of excess electrons in quantum wells. The influence of the additional illumination is observed at a temperature of approximately 100 K and almost completely suppressed at 5 K. The obtained results are explained in terms of the formation of a potential barrier for electrons at the ZnMgSSe/GaAs interface and by the specific features of recombination processes in the electron-hole system containing impurity centers with different charge states. 相似文献
34.
I. M. Batyaev Yu. A. Kabatskii E. A. Mokhova V. V. Sviridov 《Journal of Applied Spectroscopy》1989,50(4):394-397
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 50, No. 4, pp. 609–613, April, 1989. 相似文献
35.
A. F. Sviridov V. S. Borodkin M. S. Ermolenko D. V. Yashunskii 《Russian Chemical Bulletin》1989,38(3):600-606
Conclusions A synthesis of a C5-C9-fragment common to erythronolides A and B was carried out starting from levoglucosan.For previous communications, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 674–680, March, 1989. 相似文献
36.
The modification of phenol-formaldehyde oligomer with Resydrol alkyd oligomer has been proposed for the production of adhesive-bonded wood materials. The chemical processes that occur in the modified binder have been determined using IR spectroscopy. A model of chemical interaction of phenol-formaldehyde oligomer with Resydrol alkyd oligomer has been presented. 相似文献
37.
Conclusions Using Cp2Zr(H)Cl, 1,6-anhydro-2-desoxy-2-C-methyl-3-O-benzyl-4-methylene--D-xylohexapyranose has been reduced with a high degree of stereospecificity to 1,6-anhydro-2,4-didesoxy-2,4-di-C-methyl-3-Obenzyl--D-galactopyranose, which was then converted into the C9-C13 fragments of erythronolide Band oleandonolide.Short communication [1]; previous communication [2].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2568–2572, November, 1982. 相似文献
38.
The benzyloxy group at C(4) of the pyranose ring in 3,4-disubstituted and 3-deoxy carbohydrate derivatives affects the direction of intramolecular free-radical C(2)-C(6) cyclization. A possible mechanism of the formation of the tetrahydrofuran ring was proposed.For Part 3, see Ref. 1.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 767–773, April, 1995.The present work was partially supported by the Russian Foundation for Basic Research (project No. 93-03-5834) and the International Science Foundation (Project No. MOM 000). 相似文献
39.
Titanium and Iron Oxide-Based Magnetic Photocatalysts for Oxidation of Organic Compounds and Sulfur Dioxide 总被引:5,自引:0,他引:5
D. G. Shchukin E. A. Ustinovich D. V. Sviridov A. I. Kulak 《High Energy Chemistry》2004,38(3):167-173
New approaches to designing magnetic photocatalysts on the basis of microheterogeneous structures built according to the scheme magnetic core–photocatalytic shell were proposed. A procedure for preparing the Zn0.35Ni0.65Fe2O4/SiO2/TiO2 catalyst designed for the destructive oxidation of organic compounds, as well as the Fe3O4/Fe2O3/Fe4[Fe(CN)6]3: KCo[Co(CN)6] and Fe3O4/Fe2O3/polyaniline catalysts designed for the photo-oxidation of SO2, was considered. It was shown that the reduction of molecular oxygen proceeded primarily to H2O2, as a result of doping the polyaniline shell with 18-tungstophosphoric acid, and the quantum yield of the SO2 photo-oxidation reaction was doubled by coupling heterogeneous photocatalysis with homogeneous catalysis (involving the hydrogen peroxide formed). 相似文献
40.
V. D. Sviridov N. D. Chkanikov A. F. Kolomiets A. V. Fokin 《Russian Chemical Bulletin》1985,34(11):2367-2369
Conclusions A new reaction of adenine and adenosine with hexafluoroacetone, affecting the amidine fragment of their molecules and leading to tricyclic 2, 2,9,9-tetrakis(trifluoromethyl)[1,3, 5]oxadiazine[3,4-i]purines, was conducted.Translated from Izvestiya Akademii Nauk SSSR, No. 11, pp. 2554–2557, November, 1985. 相似文献