全文获取类型
收费全文 | 190篇 |
免费 | 0篇 |
专业分类
化学 | 89篇 |
晶体学 | 3篇 |
力学 | 6篇 |
数学 | 50篇 |
物理学 | 42篇 |
出版年
2022年 | 2篇 |
2020年 | 3篇 |
2016年 | 5篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 11篇 |
2012年 | 9篇 |
2011年 | 7篇 |
2010年 | 6篇 |
2009年 | 3篇 |
2008年 | 7篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 3篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2001年 | 4篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1972年 | 4篇 |
1970年 | 1篇 |
1969年 | 5篇 |
1967年 | 1篇 |
1966年 | 2篇 |
1963年 | 1篇 |
1959年 | 3篇 |
1958年 | 1篇 |
1957年 | 6篇 |
1956年 | 2篇 |
排序方式: 共有190条查询结果,搜索用时 31 毫秒
51.
Svatopluk Zeman 《Thermochimica Acta》1980,39(2):117-124
The activation energies, E, of the decomposition of picramide and its N-methyl-,N-ethyl-,N-n-propyl- and N-n-butyl-derivatives are determined by means of non-isothermal DTA, in its simple form, as well as by the Piloyan method. A relationship is found between the E values of the above-mentioned compounds and the published values of the moments of inertia of the corresponding n-alkyl groups. Taking into account data published previously, which were obtained by application of the Piloyan method in the DTA of polynitroaromates, it is concluded that by suitable selection of DTA measurement conditions, it is possible to record the early part of the exothermal decomposition of the above-mentioned compounds were no autocatalytic influence exists. Attention is also paid to the thermostability of the polynitroaromates due to their contact with the construction materials employed in the course of thermolysis. 相似文献
52.
The automated modification of the radioanalytical determination of lead and beryllium using AutoAnalyzer modules has been developed. The method for lead determination is based on a two-phase isotope exchange of lead between the sample solution labelled with212Pb and the standard lead diethyldithiocarbamate solution in carbon tetrachloride. For the determination of beryllium a substoichiometric isotope dilution method using7Be as tracer and acetylacetone in chloroform as extractant was used. As little as 0.02 μg/ml of lead and 2 μg/ml of beryllium can be determined by the methods above. The flow diagrams of the automated procedures are presented. 相似文献
53.
54.
A rapid method for the substoichiometric determination of gallium by neutron-activation analysis has been developed. After irradiation and dissolution of the test sample, gallium carrier is added and two preliminary separation steps are performed: the extraction into chloroform of cupferrates from 7N sulphuric acid and of diethyldithiocarbamates from 2-3N sulphuric acid. The pH of the remaining aqueous phase is then adjusted to 5.5, the solution extracted with a substoichiometric amount of 8-hydroxyquinoline in chloroform and the activity of the gallium hydroxyquinolate extract measured. A simultaneously irradiated gallium standard is treated in exactly the same way. From the activities of these two substoichiometric extracts the amount of gallium originally present in the test sample can be calculated. The method has been applied to the determination of 10(-6) to 10(-3)% of gallium in metallic aluminium and transistor-grade silicon. 相似文献
55.
The Piloyan activation energiesE, as well as the initial exotherm temperaturesT
D, are determined for sixN-monoalkyl- and fiveN,N-dialkyl-2,4,6-trinitroanilines. By comparison withR
f-factors, orR
M-functions of paper chromatography, the molecular-structural dependences ofE andT
D are studied for these compounds. Relationships are also found between the termE · T
D
–1
and theR
M-functions. The effects are discussed of the introduction of the 6-nitro group into the TV-substituted 2,4-dinitroanilines, and of the introduction of the 4-nitro group into the 2,6-dinitro analogues, upon the thermal stabilities of the resulting 2,4,6-trinitroanilines.
The authors would like to thank Mrs. Anna Colláková for careful DTA measurements, and Dr. Ladislav Smolka for help in the treatment of the measured results with the Wang 600 computer. 相似文献
Zusammenfassung Die AktivierungsenergienE nach Piloyan und die Anfangswerte der ExothermenT D der sechsN-monoalkyl- und fünfN,N-Dialkyl-2,4,6-trinitroaniline wurden bestimmt. Unter Berücksichtigung des Vergleichs mitR f-Faktoren oderR M-Funktionen der Papierchromatographie wurden die molekularstrukturellen AbhÄngigkeiten der WerteE undT D dieser Verbindungen untersucht. ZusammenhÄnge wurden auch zwischen dem AusdruckE · Tw D –1 und denR M-Funktionen gefunden. Der Einfluss der Einführung der 6-Nitrogruppe in dieN-substituierten 2,4-Dinitroaniline, sowie der Einfluss der Einführung der 4-Nitrogruppe in 2,6-Nitroanaloge auf die ThermostabilitÄt der resultierenden 2,4,6-Trinitroaniline werden erörtert.
Résumé On a déterminé les énergies d'activation par la méthode de Piloyan ainsi que les températures initialesT D de l'effet exothermique de sixN-monoalcoyl- et cinqN,N-dialcoyl-2,4,6-trinitroanilines. En se référant aux facteursR F ou aux valeurs des fonctionsR M en Chromatographie sur papier, on a étudié la dépendance entre les valeurs deE et deT D sur les caractéristiques moléculaires-structurales de ces composés.On a également trouvé des rapports entre le termeE · T D –1 et les fonctionsR M. On discute l'influence de l'introduction du groupe 6-nitro dans les 2,4-dinitroanilinesN-substituées ainsi que l'influence de l'introduction du groupe 4-nitro dans les 2,6-dinitro analogues sur la stabilité thermique des 2,4,6-trinitroanilines qui en résultent.
N-- N,N--2,4,6- E , T D. R f,- R M — , - E T D. E.T D –1 R M-. 6N- 2,4- 4 2,6- 2,4,6- .
The authors would like to thank Mrs. Anna Colláková for careful DTA measurements, and Dr. Ladislav Smolka for help in the treatment of the measured results with the Wang 600 computer. 相似文献
56.
The paper presents the methodology intended to the vibration and noise analysis of gearboxes or generally of large rotating systems. These systems are considered including their interior rotating shaft system and housing joined together by rollingelement bearings and gear couplings. The new developed bearing model respects real number of rolling bodies and roller contact forces acting between the journals and the outer housing. The model of a complete gearbox is created using the modal synthesis method. Steady state dynamic response of the whole gearbox excited by gear kinematic transmission errors is investigated. A noise radiated by the housing is calculated on the basis of the acoustic power density evaluation. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
57.
The contribution presents the modal synthesis method of the mathematical modelling of the large rotating systems. The condensed mathematical model is used for deriving analytical formula for eigenvalue sensitivity calculation. According to the sensitivity analysis suitable design parameters are chosen and the optimization process for the purpose of steady state response minimization in a certain operating speed area is performed. The theory is applied to a simple test‐gearbox. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
58.
The paper considers the problem of estimating the risk of a tick-borne disease in a given region. A large set of epidemiological data is evaluated, including the point pattern of collected cases, the population map and covariates, i.e. explanatory variables of geographical nature, obtained from GIS.The methodology covers the choice of those covariates which influence the risk of infection most. Generalized linear models are used and AIC criterion yields the decision. Further, an empirical Bayesian approach is used to estimate the parameters of the risk model. Statistical properties of the estimators are investigated. Finally, a comparison with earlier results is discussed from the point of view of statistical disease mapping. 相似文献
59.
Let be a family of subsets of S and let G be a graph with vertex set such that: (xA, xB) is an edge iff . The family is called a set representation of the graph G.It is proved that the problem of finding minimum k such that G can be represented by a family of sets of cardinality at most k is NP-complete. Moreover, it is NP-complete to decide whether a graph can be represented by a family of distinct 3-element sets.The set representations of random graphs are also considered. 相似文献
60.
The paper is concerned with several related combinatorial problems one of which is that of estimating the numbers of qualitatively independent p-partitions. Besides nonconstructive basic estimates, a constructive procedure yielding not much worse ones is presented. In conclusion, some applications are shown. 相似文献