全文获取类型
收费全文 | 4243篇 |
免费 | 109篇 |
国内免费 | 8篇 |
专业分类
化学 | 2449篇 |
晶体学 | 104篇 |
力学 | 127篇 |
数学 | 486篇 |
物理学 | 1194篇 |
出版年
2021年 | 36篇 |
2020年 | 56篇 |
2019年 | 45篇 |
2018年 | 31篇 |
2017年 | 28篇 |
2016年 | 82篇 |
2015年 | 75篇 |
2014年 | 79篇 |
2013年 | 141篇 |
2012年 | 153篇 |
2011年 | 218篇 |
2010年 | 117篇 |
2009年 | 123篇 |
2008年 | 158篇 |
2007年 | 152篇 |
2006年 | 161篇 |
2005年 | 129篇 |
2004年 | 140篇 |
2003年 | 118篇 |
2002年 | 102篇 |
2001年 | 81篇 |
2000年 | 99篇 |
1999年 | 64篇 |
1998年 | 52篇 |
1997年 | 58篇 |
1996年 | 75篇 |
1995年 | 67篇 |
1994年 | 65篇 |
1993年 | 73篇 |
1992年 | 74篇 |
1991年 | 55篇 |
1990年 | 56篇 |
1989年 | 56篇 |
1988年 | 65篇 |
1987年 | 59篇 |
1986年 | 52篇 |
1985年 | 55篇 |
1984年 | 32篇 |
1983年 | 52篇 |
1982年 | 42篇 |
1981年 | 68篇 |
1980年 | 45篇 |
1979年 | 59篇 |
1978年 | 64篇 |
1977年 | 53篇 |
1976年 | 52篇 |
1975年 | 38篇 |
1974年 | 36篇 |
1973年 | 41篇 |
1957年 | 28篇 |
排序方式: 共有4360条查询结果,搜索用时 31 毫秒
981.
A. Schiraldi V. Wagner G. Samanni P. Rossi 《Journal of Thermal Analysis and Calorimetry》1981,21(2):299-307
The glass transition temperatures,T
g, and thermal effects of polymerization,H, have been determined for five epoxy adhesives of unknown composition. From the trendsH vs./t
cure it has been possible to attain a phenomenological kinetic order of the polymerization rate at 100° through an iterative calculation procedure. For most of the investigated adhesives there are reasons (double peak of polymerization and doubleT
g signal) to assume that they are graft copolymers.
Zusammenfassung Die Glas-Übergangstemperaturen (T g) und dieH thermische Effekte der Polymerisation wurden für fünf Epoxy-Klebstoffe unbekannter Zusammensetzung bestimmt.Aus den TrendsH gegenübert cure war es möglich eine phenomenologische kinetische Ordnung der Polymerisationsgeschwindigkeit bei 100° durch ein iteratives Berechnungsverfahren zu ermitteln.Für die meisten untersuchten Klebstoffe besteht der Grund — Doppelpeak der Polymerisation und doppeltesT g-Signal — sie als Pfropfcopolymere zu betrachten.
Résumé On a déterminé, pour cinq adhésifs époxy de composition inconnue, les températures de transition vitreuseT g et les effets thermiques de polymérisationH.A partir de la variation deH en fonction du temps de recuit et par une méthode de calcul itératif, un ordre cinétique phénoménologique de la vitesse de polymérisation à 100° a pu être obtenu.Pour la plupart des adhésifs étudiés l'existence d'un pic double de polymérisation et d'une double transition vitreuseT g permet de supposer qu'il s'agit de copolymères greffés.
T g H. H.-t. 100° . T g , - .相似文献
982.
The increasing importance of spectroscopic methods as an analytical tool in industry, combined with the trend to automatize spectrometers, demands new standards in the quantity and quality of spectrum interpretation. Suitable computer programs should be able to predict structural features from mass spectral properties. The knowledge base is a structure-oriented mass spectral data collection consisting of some 42000 spectra and topologies. The comparison of selected mass spectral properties such as similarity, neutral losses and ion series of the unknown with the equivalent properties of the library spectra results in a set of corresponding structures. Subsequent substructure analysis yields a histogram of substructure frequencies containing information about their statistical relevance. The relevant substructure set may be recombined to produce a structure proposal, as is demonstrated for 1-acetyl-2-methoxy-4-trimethylsilyioxybenzene. In a second example, the relevant substructures derived by the interpretation system are used as input for the 13C-NMR substructure generator. This procedure reduces the solution space of the structure prediction algorithm considerably. Besides the spectrum interpretation, additional possibilities are available. The substructure search enables us, for example, to look for mass spectrometric reaction centres. Beyond that, substructure analysis is applicable to the determination of structural features typical of certain combinations of neutral losses and/or characteristic fragments. 相似文献
983.
H. Ibach H. D. Bruchmann H. Wagner 《Applied Physics A: Materials Science & Processing》1982,29(3):113-124
Using high-resolution electron energy loss spectroscopy (EELS) the vibrations of Si(111) and Si(100) surfaces in the early stages of oxidation have been investigated. Three different stages of oxidation, the last being the formation of a thin layer of vitreous SiO2 are identified when the surfaces are held at a temperature of 700K during the exposure with molecular oxygen. We show that also the first two stages involve atomic oxygen in bridging positions between silicon atoms. Small exposures at low temperatures (100 K) produce vibrational features of a different, possibly molecular, species. For higher exposures at the same temperature the spectrum again develops the characteristics of atomic oxygen and the molecular species eventually disappears. Exposure at room temperature leads to a mixture of atomic and molecular oxygen for smaller exposures and to purely atomic oxygen for exposures greater than 102 L. At room temperature even exposures as high as 1011 L do not produce the spectrum of vitreous SiO2. The same is found for the natural, room temperature grown, oxide layer on silicon wafers which we have studied by introducing the sample into the spectrometer through an air-lock. Annealing of the wafer to 700 K produced the characteristic spectrum of vitreous SiO2. The results are discussed in comparison with previous work. 相似文献
984.
A. Stuirbrink G. J. Wagner K. T. Knöpfle Liu Ken Pao G. Mairle H. Riedesel K. Schindler V. Bechtold L. Friedrich 《Zeitschrift für Physik A Hadrons and Nuclei》1980,297(4):307-309
Using the ( \(\vec d\) ,3He) reactions on90Zr and144Sm at 52 MeV spins of deeply-bound hole states have been measured for the first time. In contrast to neutron pick-up reactions the shell model strength is exhausted which enables us to derive the 1f and 1g spin-orbit splitting. 相似文献
985.
J. Großfeld A. Simmer J. van Loon W. Springer S. Juschkewitsch V. Kubelka J. Wagner S. Zuravlev Thompsonwerke W. Normann H. P. Trevithik M. F. Lauro A. Bömer A. Gehrke G. de Belsunce J. I. Lurje F. Fritz Zitek R. Otto A. Halter J. M. Purdy W. G. France W. L. Evans H. P. Kaufmann M. Keller 《Analytical and bioanalytical chemistry》1931,83(5-6):223-230
986.
J. G. M. Bullowa D. J. Porter D. S. Cryder F. B. Varga R. H. Newton K. Bunte W. Litterscheidt F. Schuster R. Graßberger A. Luszczak M. Shepherd H. F. Görlacher M. Jureček L. S. Gregory W. A. Cook J. B. Ficklen Y. Kauko J. Carlberg V. Mantere M. L. Jean S. Mihaéloff A. Klemenc R. Wechsberg G. Wagner E. Hofmann O. Fischinger R. Goubau J. Eeckhout H. Brückner W. Gröbner A. Bloch G. H. Damon H. Kautsky I. Hirsch E. Briner H. Paillard Olga Waldbauer R. Kraus P. Woog R. Sigwalt J. de Saint-Mars 《Analytical and bioanalytical chemistry》1936,104(11-12):422-432
987.
H. Menzel O. Faust J. Reitstötter R. E. Liesegang Teichmann H. Wagner 《Colloid and polymer science》1935,72(2):250-252
Ohne Zusammenfassung 相似文献
988.
Cunningham and Edmonds [4[ have proved that a 2-connected graphG has a unique minimal decomposition into graphs, each of which is either 3-connected, a bond or a polygon. They define the notion of a good split, and first prove thatG has a unique minimal decomposition into graphs, none of which has a good split, and second prove that the graphs that do not have a good split are precisely 3-connected graphs, bonds and polygons. This paper provides an analogue of the first result above for 3-connected graphs, and an analogue of the second for minimally 3-connected graphs. Following the basic strategy of Cunningham and Edmonds, an appropriate notion of good split is defined. The first main result is that ifG is a 3-connected graph, thenG has a unique minimal decomposition into graphs, none of which has a good split. The second main result is that the minimally 3-connected graphs that do not have a good split are precisely cyclically 4-connected graphs, twirls (K
3,n
for somen3) and wheels. From this it is shown that ifG is a minimally 3-connected graph, thenG has a unique minimal decomposition into graphs, each of which is either cyclically 4-connected, a twirl or a wheel.Research partially supported by Office of Naval Research Grant N00014-86-K-0689 at Purdue University. 相似文献
989.
990.
Nikodem Ku
nik Jan Zawadiak Danuta Gilner Angelika Wickol Pawe Wagner Maciej Kubicki 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(9):o549-o550
The title compound, C26H30O4, is one of the first alkyl bis‐peroxides to be structurally characterized. The molecule lies on a centre of inversion and therefore the terminal phenyl rings are parallel. Although there are three aromatic rings in the molecule, the C—O—O—C torsion angle of 163.10 (10)° is close to the value found in Me3COOCMe3. 相似文献