全文获取类型
收费全文 | 807篇 |
免费 | 23篇 |
国内免费 | 2篇 |
专业分类
化学 | 506篇 |
晶体学 | 44篇 |
力学 | 14篇 |
数学 | 88篇 |
物理学 | 180篇 |
出版年
2020年 | 7篇 |
2017年 | 10篇 |
2016年 | 16篇 |
2015年 | 7篇 |
2014年 | 15篇 |
2013年 | 42篇 |
2012年 | 21篇 |
2011年 | 32篇 |
2010年 | 14篇 |
2009年 | 20篇 |
2008年 | 25篇 |
2007年 | 23篇 |
2006年 | 18篇 |
2005年 | 15篇 |
2004年 | 12篇 |
2003年 | 17篇 |
2002年 | 13篇 |
2001年 | 15篇 |
2000年 | 12篇 |
1999年 | 19篇 |
1998年 | 9篇 |
1997年 | 14篇 |
1996年 | 10篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 8篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 17篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 14篇 |
1985年 | 10篇 |
1984年 | 22篇 |
1983年 | 13篇 |
1982年 | 7篇 |
1981年 | 18篇 |
1980年 | 19篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 13篇 |
1975年 | 7篇 |
1974年 | 12篇 |
1973年 | 7篇 |
1972年 | 8篇 |
1971年 | 8篇 |
1968年 | 6篇 |
1967年 | 7篇 |
1908年 | 5篇 |
排序方式: 共有832条查询结果,搜索用时 218 毫秒
1.
Operators on manifolds with corners that have base configurations with geometric singularities can be analysed in the frame of a conormal symbolic structure which is in spirit similar to the one for conical singularities of Kondrat'ev's work. Solvability of elliptic equations and asymptotics of solutions are determined by meromorphic conormal symbols. We study the case when the base has edge singularities which is a natural assumption in a number of applications. There are new phenomena, caused by a specific kind of higher degeneracy of the underlying symbols. We introduce an algebra of meromorphic edge operators that depend on complex parameters and investigate meromorphic inverses in the parameter-dependent elliptic case. Among the examples are resolvents of elliptic differential operators on manifolds with edges. 相似文献
2.
A. G. Milekhin A. I. Nikiforov M. Yu. Ladanov O. P. Pchelyakov S. Schulze D. R. T. Zahn 《Physics of the Solid State》2004,46(1):92-96
This paper reports on the results of resonant Raman scattering investigations of the fundamental vibrations in Ge/Si structures with strained and relaxed germanium quantum dots. Self-assembled strained Ge/Si quantum dots are grown by molecular-beam epitaxy on Si(001) substrates. An ultrathin SiO2 layer is grown prior to the deposition of a germanium layer with the aim of forming relaxed germanium quantum dots. The use of resonant Raman scattering (selective with respect to quantum dot size) made it possible to assign unambiguously the line observed in the vicinity of 300 cm?1 to optical phonons confined in relaxed germanium quantum dots. The influence of confinement effects and mechanical stresses on the vibrational spectra of the structures with germanium quantum dots is analyzed. 相似文献
3.
Julie Clutterbuck Oliver C. Schnürer Felix Schulze 《Calculus of Variations and Partial Differential Equations》2007,29(3):281-293
We prove stability of rotationally symmetric translating solutions to mean curvature flow. For initial data that converge
spatially at infinity to such a soliton, we obtain convergence for large times to that soliton without imposing any decay
rates.
The authors are members of SFB 647/B3 “Raum – Zeit – Materie: Singularity Structure, Long-time Behaviour and Dynamics of Solutions
of Non-linear Evolution Equations”. 相似文献
4.
5.
On the Dispersion of Metals in Supported Catalysts. II. Small Angle X-ray Investigation. on Platinum/Alumina and Palladium/Alumina Catalysts The metal dispersion in 0.5% Pd/A12O3. 0.5°% Pt/Al2O3 abd 1.5% Pt/Al2O3 catalysts was investigated by small angle X-ray scattering, Using a Kratky camera the difference scattering curves catalyst-carrier were evaluated. The assumption was made that the scattering centres are globular and that there is no interparticular scattering. From the Guinier approximation the Guinier radii RG of the metal particles were determined. With the Pd catalyst always positive difference scattering curves were found, whereas negative values were found with the Pt catalysts at a scattering angle greater than 0.022 rad. Therefore only for the sample with 0.5% Pd the Porod invariant \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \tilde Q}$\end{document} and the Porod radius RP could be determined. From RG and RP the parameters of a two- and of a one-parametric distribution were calculated. The results are in good agreement with data from wide angle X-ray diffraction measurements. 相似文献
6.
Isothiosemicarbazides 2 react with acyl isothiocyanates under addition-cyclization to yield 1,3,4-thiadiazoline-2-imines 3 as well as the isomeric 2-amino-substituted 1,3,4-thiadiazolium-5-acylaminides 3′ . In a similar manner the 2-hydrazino-substituted 1,3-thiazoline 4 adds ethoxycarbonyl isothiocyanate to give the thiosemicarbazide 5 , which undergoes a rearrangement to the 1,3,4-thiadiazoline-2-imine 5′. The [2+2] cycloreversion of 3d involving ethoxycarbonyl iso(thio)cyanate and the thermal induced Dimroth rearrangement of 3′f and h are also discussed. 相似文献
7.
Werner Schulze und Manfred Scheffler 《Fresenius' Journal of Analytical Chemistry》1967,226(5):395-401
Zusammenfassung Um Material zur Deutung des Mechanismus der Sorption von Sr2+-Ionen an Eisen(III)-hydroxid zu gewinnen, werden Meßreihen mitgeteilt, in denen die pH-Abhängigkeit der Sorption sowie deren Beeinflussung bei Fällung mit verschiedenen Basen (NaOH, Ammoniak, Trimethylamin, Benzylamin) untersucht wird. Aus den charakteristischen Unterschieden der Sorptionskurven muß gefolgert werden, daß die Art der Base für die Sorption eine wichtige Rolle spielt.
Summary The sorption of Sr2+ ions on iron(III) hydroxide was studied as a function of the pH, of the precipitating reagent (NaOH, ammonium hydroxide, benzylamine, trimethylamine), of the temperature and of the total concentration.The curves of the relative sorption vs. pH are found to show characteristic differences which have to be explained in a detailed theory of the mechanism.相似文献
8.
M. Röder J. Hahn U. Falke S. Schulze F. Richter M. Hietschold 《Mikrochimica acta》1997,125(1-4):283-286
A series of BN films was deposited by means of r.f. magnetron sputtering of a h-BN target onto Si(1OO) surfaces. Hereby, the substrate bias voltage was varied. Special interest is focussed to the influence of the deposition parameters on the orientation of the growing hexagonal BN film with respect to the substrate. For structural investigation, cross section samples were prepared. In addition to HRTEM and diffraction investigations, especially electron energy loss spectroscopy (EELS) was applied successfully for phase identification. For negative bias voltages of U
B
=–300 V and U
B
=–350V, we found a phase system consisting of a first-grown 25 nm thick layer of hexagonal structure with the c axis parallel to the substrate surface followed by the cubic phase.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday 相似文献
9.
Einkristalle von SrAl2O4 wurden durch Hochtemperaturreaktionen von SrO mit Al2O3 dargestellt und röntgenographisch untersucht (a = 844,7; b = 881,6; c = 516,3 pm;β = 93,42°; Raumgruppe C–;P21, Z = 4). Die Tetraederabfolge in den Sechsringen dieser aufgefüllten Tridymit-Struktur wird mit der ähnlicher Oxometallate verglichen. Compound Formation MeO:M2O3. IV. Structure of Monoclinic SrAl2O4 Single crystals of SrAl2O4 were prepared by high temperature CO2-LASER technique and investigated by X-ray methods. (a = 844.7; b = 881.6; c = 516.3 pm; β = 93.42°; space group C–P21, Z = 4). The orientation of the tetrahedra in this stuffed tridymite structure is discussed in comparison with related oxometallates. 相似文献
10.
Klaus Behmel Manfred Schulze und Ulrich Annagat 《Fresenius' Journal of Analytical Chemistry》1968,241(1):1-4
Zusammenfassung Eine einfache und genaue Methode zur Bestimmung von Si-H- und Si-Si-Gruppen wird vorgeschlagen, die auf alkalischer Hydrolyse der Substanz in einem verschlossenen und evakuierten Kolben und AuswÄgen des dem entwickelten Wasserstoff entsprechenden Wasservolumens beruht. Bei H-Gehalten von 1–2% betrÄgt die Genauigkeit ± 0,03% (abs.).
Herrn Prof. Dr. E. Asmus zum 60. Geburtstag gewidmet. 相似文献
Note on the quantitative determination of Si-H- and Si-Si-groups
A simple, robust and surprisingly exact method for the quantitative determination of Si-H- or Si-Si-groups is based on alkaline hydrolysis of the Si-H- or Si-Si-containing substances in a sealed and evacuated vessel and weighing of the volume of water equivalent to the developed volume of hydrogen. The accuracy is ± 0.03% (abs.) with H contents of 1–2%.
Herrn Prof. Dr. E. Asmus zum 60. Geburtstag gewidmet. 相似文献