全文获取类型
收费全文 | 88篇 |
免费 | 5篇 |
专业分类
化学 | 69篇 |
数学 | 9篇 |
物理学 | 15篇 |
出版年
2022年 | 1篇 |
2021年 | 3篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 3篇 |
2012年 | 2篇 |
2011年 | 4篇 |
2010年 | 2篇 |
2008年 | 3篇 |
2007年 | 6篇 |
2006年 | 6篇 |
2005年 | 5篇 |
2004年 | 1篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1982年 | 1篇 |
1975年 | 3篇 |
1973年 | 4篇 |
1971年 | 1篇 |
1964年 | 2篇 |
1956年 | 1篇 |
1937年 | 1篇 |
1932年 | 2篇 |
1931年 | 2篇 |
1928年 | 2篇 |
排序方式: 共有93条查询结果,搜索用时 281 毫秒
1.
The formation region of the various types of layered titanium hydrogen phosphate hydrates was investigated. The materials were prepared by hydrothermal methods, treating amorphous titanium phosphate with phosphoric acid (8 to 16M) in the temperature range 175 to 250°C. The materials obtained were:α-Ti(HPO4)2·H2O,γ-Ti(PO4)(H2PO4)·2H2O, and its anhydrous formβ-Ti(PO4)(H2PO4). The structure ofβ-Ti(PO4)(H2PO4) has been determined by Rietveld powder refinement of high resolution neutron diffraction data. The structure is refined in the monoclinic space groupP21/n(No. 14). The unit cell parameters are:a=18.9503(4) Å,b=6.3127(1) Å,c=5.1391(1) Å,β=105.366(2)°;Z=4. The final agreement factors were:Rp=2.9% andRwp=3.8%. The structure ofβ-Ti(PO4)(H2PO4) is built from TiO6octahedra linked together by tertiary phosphate (PO4) and dihydrogen phosphate ((OH)2PO2) tetrahedra. The layers are held together by hydrogen bonds. 相似文献
2.
Herein, we outline a method that is able to generate truly minimal basis sets that accurately describe either a group of bands, a band, or even just the occupied part of a band. These basis sets are the so-called NMTOs, muffin-tin orbitals of order N. For an isolated set of bands, symmetrical orthonormalization of the NMTOs yields a set of Wannier functions that are atom-centered and localized by construction. They are not necessarily maximally localized, but may be transformed into those Wannier functions. For bands that overlap others, Wannier-like functions can be generated. It is shown that NMTOs give a chemical understanding of an extended system. In particular, orbitals for the pi and sigma bands in an insulator, boron nitride, and a semimetal, graphite, will be considered. In addition, we illustrate that it is possible to obtain Wannier-like functions for only the occupied states in a metallic system by generating NMTOs for cesium. Finally, we visualize the pressure-induced s-->d transition. 相似文献
3.
4.
An automated method for the determination of pholcodine in plasma and whole blood is described. The technique combines dialysis and trace enrichment prior to high-performance liquid chromatography. Dialysis, trace enrichment on a weak cation-exchange column, separation on a cyano column and fluorescence detection was shown to be an extremely selective and sensitive method. The method has been used successfully in the analysis of real samples after administration of pholcodine. The automated method can be used, after minor modification, to determine other basic drugs in whole blood and plasma. 相似文献
5.
6.
7.
An environmentally stable mode-locked fiber laser based on nonlinear polarization rotation is experimentally demonstrated. The laser is based on a novel laser configuration that has negligible low-power steady-state reflectivity from one side and, consequently, no CW gain. The laser is self starting and the configuration is implementable as an all-fiber laser with standard polarization-maintaining fiber-pigtailed components. A pulse duration of 5.6 ps is obtained at a repetition rate of 5.96 MHz and at an average power of 8 mW. As an application of the proposed laser configuration, 213 mW of supercontinuum (600-1750 nm) was demonstrated from a fiber laser system with no sections of free-space optics. 相似文献
8.
T. Eichten H. Deden F.J. Hasert W. Krenz J. Von Krogh D. Lanske J. Morfin H. Weerts G. Bertrand-Coremans J. Sacton W. Van Doninck P. Vilain D.C. Cundy D. Haidt M. Jaffre G. Kalbfleisch S. Natali P. Musset J.L. Pinfold 《Physics letters. [Part B]》1973,46(2):281-284
The total cross-sections for -nucleon scattering have been measured. A test has been made of the muon number conservation law. A limit of 2.4 GeV is found the mass of the “Georgi-Glashow type” heavy lepton 相似文献
9.
Stig Veibel A. K. Dhamoon und Inger Grete Krogh Andersen 《Fresenius' Journal of Analytical Chemistry》1964,200(6):439-443
Zusammenfassung Acetylaceton und Benzoylaceton bilden mit elektronegativ substituierten Phenylhydrazinen, selbst mit 2,4-Dinitrophenylhydrazin, und selbst wenn die Reaktion bei Zimmertemperatur durchgeführt wird, 1,3,5-tri-substituierte Pyrazole ohne nachweisbare Mengen von Zwischenprodukten (Monophenylhydrazone).5-Methoxypentan-2,4-dion bildet mit p-Nitrophenylhydrazin bei Zimmertemperatur ein Monophenylhydrazon. Bei höherer Temperatur wird aber auch hier das entsprechende Pyrazol gebildet.
Wir möchten nicht unterlassen, dem Carlsbergfond unseren Dank für eine finanzielle Unterstützung auszusprechen. 相似文献
Summary Acetylacetone and benzoylacetone react with electro-negatively substituted phenylhydrazines to form 1,3,5-trisubstituted pyrazoles, also with 2,4-dinitrophenylhydrazine and even if the reaction is performed at room temperature. There are no detectable quantities of intermediate products (monophenylhydrazones).5-Methoxypentane-2,4-dione is forming with p-nitrophenylhydrazine at room temperature a monophenylhydrazone, but at higher temperature the corresponding pyrazole is also formed.
Wir möchten nicht unterlassen, dem Carlsbergfond unseren Dank für eine finanzielle Unterstützung auszusprechen. 相似文献
10.
Alongkrit Chutinan Bruce H. Krogh 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2013,19(1):30-50
This paper presents a new algorithm for generating finite-state automata models of hybrid systems in which the continuous-state dynamics can be switched when the continuous-state trajectory generates threshold events. The automata state transitions correspond to threshold events and the automata states correspond to portions of the threshold surfaces in the continuous state space. The hybrid system dynamics are approximated by the automata models in the sense that the languages of threshold event sequences generated by the automata contain the threshold event language for the hybrid system. Properties of the algorithm for constructing and refining the approximating automata are demonstrated and the application of approximating automata for system verification is illustrated for a switching controller for an inverted pendulum. Relationships to other approaches to hybrid system synthesis and verification are also discussed. 相似文献