全文获取类型
收费全文 | 1559篇 |
免费 | 20篇 |
国内免费 | 6篇 |
专业分类
化学 | 889篇 |
晶体学 | 63篇 |
力学 | 32篇 |
数学 | 109篇 |
物理学 | 492篇 |
出版年
2022年 | 20篇 |
2021年 | 27篇 |
2020年 | 20篇 |
2019年 | 23篇 |
2018年 | 23篇 |
2017年 | 24篇 |
2016年 | 36篇 |
2015年 | 24篇 |
2014年 | 41篇 |
2013年 | 118篇 |
2012年 | 78篇 |
2011年 | 89篇 |
2010年 | 45篇 |
2009年 | 49篇 |
2008年 | 54篇 |
2007年 | 57篇 |
2006年 | 67篇 |
2005年 | 48篇 |
2004年 | 46篇 |
2003年 | 31篇 |
2002年 | 42篇 |
2001年 | 25篇 |
2000年 | 17篇 |
1999年 | 14篇 |
1998年 | 12篇 |
1997年 | 14篇 |
1996年 | 12篇 |
1995年 | 15篇 |
1994年 | 18篇 |
1993年 | 18篇 |
1992年 | 28篇 |
1991年 | 21篇 |
1990年 | 21篇 |
1989年 | 21篇 |
1988年 | 18篇 |
1987年 | 13篇 |
1986年 | 21篇 |
1985年 | 25篇 |
1984年 | 22篇 |
1983年 | 25篇 |
1982年 | 18篇 |
1981年 | 19篇 |
1980年 | 30篇 |
1979年 | 28篇 |
1978年 | 23篇 |
1977年 | 19篇 |
1976年 | 11篇 |
1975年 | 15篇 |
1973年 | 12篇 |
1971年 | 9篇 |
排序方式: 共有1585条查询结果,搜索用时 46 毫秒
111.
Y.N. Joshi K.S. Bhatia W.E. Jones 《Spectrochimica Acta Part B: Atomic Spectroscopy》1973,28(4):149-155
The third and fourth spectra of gallium have been photographed in the region 6000–400 Å by using a 3-m normal-incidence, vacuum spectrograph and a 3.5-m Ebert spectrograph. A three-electrode vacuum spark and a spark in helium were used as sources. New measurements for the wavelengths have confirmed earlier work and provided material to extend the analysis of Ga III and Ga IV. 相似文献
112.
J.C. Joshi N.C. Pandey B.C. Joshi B.C. Pandey J. Joshi 《Solid State Communications》1978,27(11):1051-1053
Characteristic visible green emission of Ho3+ and Er3+ was observed in zinc tellurite glass. Multiphonon relaxation theory was quantitatively applied to explain the experimentally obtained results. Fluorescence assignments and lifetime measurements have also been made. 相似文献
113.
Traps were created in the single crystal of CdSe by bombardment with Mo Kα X-ray radiation. These traps were studied by the relaxation curves of photoconductivity, obtained at 6000 Å and after two dosages of radiation. It has been found out that the traps created were β-type. 相似文献
114.
R. M. Joshi 《Journal of Polymer Science.Polymer Physics》1970,8(5):679-687
Thermodynamic functions of ten monomeric compounds have been calculated for three temperatures by the statistical method using molecular structural data and vibrational assignments. The ideal gas state entropies at 298.15°K are: maleic anhydride, 71.9; β-propiolactone, 69.1; vinylene carbonate, 70.1; cyclopentadiene, 65.3; diketene, 72.3; cyclopropene, 58.7, vinyl fluoride, 60.4; ethyleneimine, 62.8; butatriene, 71.7; and carbon suboxide, 66.0 cal./deg-mole. The standard free energies and equilibrium constants of formation are also derived by using mostly the published data on the heats of formation of these monomers. 相似文献
115.
Joshi Shrikant V. Park Jin Y. Taylor P. R. Richardson L. S. 《Plasma Chemistry and Plasma Processing》1985,5(2):143-161
Plasma Chemistry and Plasma Processing - A new integral mean diffusivity is proposed for the calculation of the mass transfer rate around a small particle immersed in a thermal plasma gas.... 相似文献
116.
M. D. Sastry M. K. Bhide K. Savitri Y. Babu B. D. Joshi 《Fresenius' Journal of Analytical Chemistry》1979,298(5):367-372
Summary Studies were conducted on the assay of Sm, Eu, Dy and Er separated from uranium using aqueous standards by electrothermal AAS with Massmann type graphite furnace. The working curves were found to be linear in the ranges Sm (1–10 g/ml), Eu (0.05–0.6 g/ml), Dy (0.1–0.8 g/ml) and Er (0.1–1.0 g/ml). The values obtained for synthetic samples agreed favourably with those obtained by emission spectrographic method. Experiments using pyrolytic carbon coated tubes with and without pretreatment by La, Ta and Y have shown an enhancement with treatment upto a maximum of 15% and improve the memory effect marginally. The effect of Ta treatment was found to be singularly useful in improving the general behaviour of Sm. The interference effects of lanthanides, other than the analyte, were found to be negligible. However, the presence of uranium was found to affect the absorbance. The absorbance of Eu was found to be nearly independent of uranium after an initial increase. On the other hand, the absorbance of other elements studied was found to drastically decrease after an initial enhancement. Detailed investigations of temperature dependence of absorbance were carried out using Eu, Dy and Er. The differences in the behaviour of these elements is attributed to probable differences in the modes of their atomization.
Untersuchung von aus Uran abgetrenntem Samarium, Europium, Dysprosium und Erbium durch elektrothermische Atomabsorptions-Spektralphotometrie
Zusammenfassung Die Untersuchungen wurden mit Hilfe des Graphitrohrofens nach Maßmann durchgeführt. In folgenden Bereichen ergaben sich lineare Eichkurven: Sm 1–10 g/ml, Eu 0,05–0,6 g/ml, Dy 0,1–0,8 g/ml, Er 0,1-1,0 g/ml. Die aus synthetischen Proben erhaltenen Ergebnisse stimmten gut mit den durch Emissionsspektrographie erhaltenen überein. Versuche wurden mit Röhren mit pyrolytischen Kohlenstoffüberzug mit und ohne Vorbehandlung durch La, Ta und Y durchgeführt und ergaben eine bis 15%ige Steigerung durch die Behandlung sowie eine mäßige Besserung des Memoryeffektes. Eine Behandlung mit Ta war besonders für Sm vorteilhaft. Störungen durch andere Lanthanide waren vernachlässigbar. Uran beeinflußte jedoch die Absorption. Im Falle von Eu zeigte sich nach anfänglicher Zunahme fast eine Unabhängigkeit, während bei den anderen untersuchten Elementen nach anfänglicher Zunahme eine beträchtliche Abnahme auftrat. Mit Eu, Dy und Er wurde ebenfalls die Temperaturabhängigkeit der Absorption untersucht. Festgestellte Unterschiede im Verhalten werden auf unterschiedliche Atomisierung zurückgeführt.相似文献
117.
118.
The optimisation of ultrasonic cleaning procedures for dairy fouled ultrafiltration membranes 总被引:3,自引:0,他引:3
Muthukumaran S Kentish S Lalchandani S Ashokkumar M Mawson R Stevens GW Grieser F 《Ultrasonics sonochemistry》2005,12(1-2):29-35
Ultrafiltration (UF) of whey is a major membrane based process in the dairy industry. However, commercialization of this application has been limited by membrane fouling, which has a detrimental influence on the permeation rate. There are a number of different chemical and physical cleaning methods currently used for cleaning a fouled membrane. It has been suggested that the cleaning frequency and the severity of such cleaning procedures control the membrane lifetime. The development of an optimal cleaning strategy should therefore have a direct implication on the process economics. Recently, the use of ultrasound has attracted considerable interest as an alternative approach to the conventional methods. In the present study, we have studied the ultrasonic cleaning of polysulfone ultrafiltration membranes fouled with dairy whey solutions. The effects of a number of cleaning process parameters have been examined in the presence of ultrasound and results compared with the conventional operation. Experiments were conducted using a small single sheet membrane unit that was immersed totally within an ultrasonic bath. Results show that ultrasonic cleaning improves the cleaning efficiency under all experimental conditions. The ultrasonic effect is more significant in the absence of surfactant, but is less influenced by temperature and transmembrane pressure. Our results suggest that the ultrasonic energy acts primarily by increasing the turbulence within the cleaning solution. 相似文献
119.
[reaction: see text] First examples of aromatic core-modified twisted heptapyrrolic systems with six meso links have been obtained via a general [3 + 4] acid-catalyzed condensation method. Despite the twisted conformation, these heptaphyrins exhibit aromaticity in solution, unlike most of the all-aza analogues. 相似文献
120.
We have experimentally investigated dynamical hysteresis behavior by changing the sweeping frequency of the cavity input field in the optical bistability of rubidium atoms (in a three-level atomic-type configuration) inside an optical cavity. The shape, width (or area), and direction of the hysteresis cycle are sensitive functions of the sweeping frequency for such an optical bistable system. 相似文献