全文获取类型
收费全文 | 114篇 |
免费 | 2篇 |
专业分类
化学 | 59篇 |
晶体学 | 4篇 |
力学 | 3篇 |
数学 | 38篇 |
物理学 | 12篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 1篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2010年 | 6篇 |
2009年 | 4篇 |
2008年 | 3篇 |
2007年 | 2篇 |
2006年 | 1篇 |
2005年 | 1篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2001年 | 1篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1985年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 1篇 |
1941年 | 2篇 |
1939年 | 1篇 |
1938年 | 1篇 |
1933年 | 2篇 |
排序方式: 共有116条查询结果,搜索用时 15 毫秒
91.
Katharina Pock F. Steger T. Schönfeld 《Journal of Radioanalytical and Nuclear Chemistry》1991,155(6):427-433
The thorium content of quartz glass tubing was found to vary greatly from very low values (<5 ng Th/g) to about 300 ng Th/g. When trace amounts of thorium are to be determined by activation analysis, e.g. in excreta, thorium content of quartz glass irradiation vials has to be taken into consideration. Analysis of fecal ash samples from persons living in the Vienna area who were not occupationally exposed to thorium containing dust, gave thorium excretion rates in feces of 0.5 to 8 g per day. For occupationally exposed persons some of the values were much higher, up to 70 g per day. 相似文献
92.
H. Steger M. Honka W. Kamke I. V. Hertel 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1994,29(2):81-83
Ionization dynamics of free C60 is investigated after single photon excitation with synchrotron radiation in the energy range between 8.9 eV and 27.6 eV. Upper limits for the time constants describing possible delayed ionization are obtained from peak shape asymmetries in time of flight spectra as a function of excitation energy. The results clearly indicate that delayed ionization is not observed after single photon excitation in contrast to the results obtained in ns-laser MPI experiments. 相似文献
93.
A method has been developed to determine sulphate and thiosulphate in small amounts of the oxidation products of sulphide minerals. The sample is treated with ammonium sulphide solution to promote ion-exchange between sulphide ion and the sulphur-bearing anions of the oxidation products. Sulphate is determined alone and then all other sulphoxy anions are oxidized to sulphate and determined as such. The non-sulphate anions are reported as thiosulphate. The relative error is about 10% or less for 2 mg or more of sulphoxy anion. Although this method does not yield exact results with respect to sulphite or polythionates, a clearer understanding of the oxidation of sulphide minerals is now available. 相似文献
94.
A study of the physical state of226Ra in uranium mill tailings was undertaken by Chemex Laboratories Ltd. under contract to NUTP. A test portion of a leached uranium ore was collected just prior to neutralization with lime and subjected to repetitive batch water leaching. The leachates were analyzed for barium, lead,226Ra, iron and sulphate. The experimental results suggest that226Ra is co-precipitated with lead sulphate during uranium leaching of the ore with sulphuric acid. The attainment of equilibrium conditions in the pore water of the leached ore then allows a re-proportioning of226Ra between solid lead and barium sulphates resulting in a depletion of226Ra in the outer layers of the crystals of solid lead sulphate and an enrichment in226Ra in the outer layers of solid barium sulphate. 相似文献
95.
96.
The stability of three certified reference sulphide ores, MP-1, KC-1 and SU-1, towards air oxidation has been measured at 50 degrees and 40, 62 and 82% relative humidity, and at 62% relative humidity and 34 degrees and 67 degrees . Both the relative humidity and temperature affect the rate of oxidation but their relative importance depends on the mineralogical composition of the ore. Changes in the water-extractable metals and elemental sulphur content on oxidation have been determined. It is concluded that these ores may be stored safely in sealed bottles under normal laboratory conditions. 相似文献
97.
J. Krauss J. de Vries H. Steger E. Kaiser B. Kamke W. Kamke 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,20(1):29-32
Single photon ionization of argon and krypton clusters has been studied in the region between threshold and the ionization potential of the corresponding atom. Synchrotron radiation from the electron storage ring BESSY is used to ionize the clusters; threshold-photo-electron-photoion-coincidence (TPEPICO)-time-of-flight technique is used to detect ions correlated with the emission of zero-kinetic-energy-electrons. The spectra of the clusters in the range ofn=2 to 15 are discussed in view of the extensive fragmentation taking place in these systems. In order to characterize the properties of the clusters a method using scaling laws is applied. The principles and the deduction of Hagena's scaling parameter Γ* are briefly reviewed. Using Γ* an experimentally derived mean cluster size for molecular beams can be assigned. This allows one to clearly demonstrate the systematic variations of the measured spectra due to cluster fragmentation. As a general feature it is observed that, in the range studied, the peak in the measured ionization rate for a cluster ion (fragment) of a given size shifts to higher photon energies as the mean cluster size is increased. 相似文献
98.
We study the Maker‐Breaker H‐game played on the edge set of the random graph . In this game two players, Maker and Breaker, alternately claim unclaimed edges of , until all edges are claimed. Maker wins if he claims all edges of a copy of a fixed graph H; Breaker wins otherwise. In this paper we show that, with the exception of trees and triangles, the threshold for an H‐game is given by the threshold of the corresponding Ramsey property of with respect to the graph H. © 2015 Wiley Periodicals, Inc. Random Struct. Alg., 49, 558–578, 2016 相似文献
99.
Let {Gi} be the random graph process: starting with an empty graph G0 with n vertices, in every step i ≥ 1 the graph Gi is formed by taking an edge chosen uniformly at random among the nonexisting ones and adding it to the graph Gi ? 1. The classical “hitting‐time” result of Ajtai, Komlós, and Szemerédi, and independently Bollobás, states that asymptotically almost surely the graph becomes Hamiltonian as soon as the minimum degree reaches 2, that is if δ(Gi) ≥ 2 then Gi is Hamiltonian. We establish a resilience version of this result. In particular, we show that the random graph process almost surely creates a sequence of graphs such that for edges, the 2‐core of the graph Gm remains Hamiltonian even after an adversary removes ‐fraction of the edges incident to every vertex. A similar result is obtained for perfect matchings. 相似文献
100.
Patrik Blumenthal Marc C. Steger Daniel Einfalt Jrg Rieke-Zapp Andrs Quintanilla Bellucci Katharina Sommerfeld Steffen Schwarz Dirk W. Lachenmeier 《Molecules (Basel, Switzerland)》2021,26(9)
Methanol is a natural ingredient with major occurrence in fruit spirits, such as apple, pear, plum or cherry spirits, but also in spirits made from coffee pulp. The compound is formed during fermentation and the following mash storage by enzymatic hydrolysis of naturally present pectins. Methanol is toxic above certain threshold levels and legal limits have been set in most jurisdictions. Therefore, the methanol content needs to be mitigated and its level must be controlled. This article will review the several factors that influence the methanol content including the pH value of the mash, the addition of various yeast and enzyme preparations, fermentation temperature, mash storage, and most importantly the raw material quality and hygiene. From all these mitigation possibilities, lowering the pH value and the use of cultured yeasts when mashing fruit substances is already common as best practice today. Also a controlled yeast fermentation at acidic pH facilitates not only reduced methanol formation, but ultimately also leads to quality benefits of the distillate. Special care has to be observed in the case of spirits made from coffee by-products which are prone to spoilage with very high methanol contents reported in past studies. 相似文献