全文获取类型
收费全文 | 288篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
化学 | 160篇 |
晶体学 | 4篇 |
力学 | 5篇 |
数学 | 43篇 |
物理学 | 80篇 |
出版年
2021年 | 3篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 2篇 |
2013年 | 18篇 |
2012年 | 8篇 |
2011年 | 10篇 |
2010年 | 5篇 |
2009年 | 10篇 |
2008年 | 8篇 |
2007年 | 16篇 |
2006年 | 6篇 |
2005年 | 6篇 |
2004年 | 10篇 |
2003年 | 4篇 |
2002年 | 17篇 |
2001年 | 6篇 |
2000年 | 10篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 7篇 |
1962年 | 2篇 |
1948年 | 4篇 |
1933年 | 3篇 |
1916年 | 1篇 |
1913年 | 1篇 |
1894年 | 1篇 |
排序方式: 共有292条查询结果,搜索用时 16 毫秒
81.
The nitate-selective membrane electrode based on tributyloctadecylphosphonium nitrate can be used to quantify perrhenate and perchlorate after appropriate conditioning of the membrane. Near-Nernstian responses are obtained for 10?3–10?6 M perrhenate and 10?2–4 × 10?6 M perchlorate. Iron(II), copper(II) and chloride do not interfere in moderate amounts; other interferences are discussed. Rhenium leaches are analysed after suitable sample preparation. The electrode is useful in following the potentiometric titration of perrhenate with nitron. 相似文献
82.
M. Feist R. Kunze D. Neubert K. Witke E. Kemnitz 《Journal of Thermal Analysis and Calorimetry》1997,49(2):635-647
(trienH2)[CoCl4], which contains tetrahedral chlorocobaltate(II) anions, decomposes under argon in two stages via a stepwise deprotonation of the cation. The decomposition starts at 310°C with the liberation of HCl, followed at 400°C by the simultaneous release of a further mole of HCl and triene and/or its cracking products. The second decomposition stage is strongly influenced by the atmosphere. In the lower temperature region (<400°C), increasing oxygen contents of the carrier gas lead to decreasing mass losses. Therefore, the solid residues contain various amounts of C,N-containing products as well as coke. The thermal decomposition of the iron(III) compound, which contains μ-oxalato-bridged FeCl4 units, begins with the dehydratation followed by the decay of the complex anion to produce CO, CO2, and HCl. Instead of a binuclear, monooxobridged chloroferrate(III) complex, a [FeCl4]? — containing compound is proposed as one of the final products. The third decomposition stage, partially overlaying the preceding one, is the degradation of the organic cation as found for the cobalt compound. The results of thein situ-TA-MS measurements are compared with those obtained from usual TA techniques as well as from the residue characterization by X-ray diffraction, Raman spectroscopy, and chemical analysis. 相似文献
83.
The conformations and vibrational spectra of the 2,6-dimethylanisole and n-propyl-2,6-dimethylphenyl ether molecules have been analysed within the framework of density functional theory. The calculated force field (B3LYP/6-31G*) has been transformed to internal coordinates, and the set of 10 different scaling factors has been applied. The scaled quantum mechanical method reproduces the experimental range of the IR and Raman spectra with high accuracy. According to the computations, the conformational behaviour of the alkyl aryl ethers studied is similar to the related dialkyl ether molecules, i.e. the CO–CC bond prefers the anti conformation, while the OC–CC bond prefers the gauche conformation. The major part of the vibrational spectra of the title compounds can be approximated by the sum of the vibrational modes of their constituent groups, these modes being transferable among the related molecules. 相似文献
84.
M. Kunze 《Mathematical Methods in the Applied Sciences》1999,22(6):515-529
We show the existence of periodic solutions to models in elastoplasticity, like the Chaboche model. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
85.
Christine Kunze Ion Neda Matthias Freytag Peter G. Jones Reinhard Schmutzler 《无机化学与普通化学杂志》2002,628(3):545-552
The reaction behaviour of 1, 3, 5‐triaza‐2σ3λ3‐phosphorin‐4, 6‐dionyloxy‐substituted calix[4]arenes towards mono‐ and binuclear rhodium and platinum complexes was investigated. Special attention was directed to structure and dynamic behaviour of the products in solution and in the solid state. Depending on the molar ratio of the reactands, the reaction of the tetrakis(triazaphosphorindionyloxy)‐substituted calix[4]arene ( 4 ) and its tert‐butyl‐derivative ( 1 ) with [(cod)RhCl]2 yielded the mono‐ and disubstituted binuclear rhodium complexes 2 , 3 , and 5 . In all cases, a C2‐symmetrical structure was proved in solution, apparently caused by a fast intramolecular exchange process between cone conformation and 1, 3‐alternating conformation. The X‐ray crystal structure determination of 5 confirmed [(calixarene)RhCl]2‐coordination through two opposite phosphorus atoms with a P ⃜P separation of 345 pm. The complex displays crystallographic inversion symmetry, and the Rh2Cl2 core is thus exactly planar. Reaction of 1 and of the bis(triazaphosphorindionyloxy)‐bis(methoxy)‐substituted tert‐butyl‐calix‐[4]arene ( 7 ) with (cod)Rh(acac) in equimolar ratio and subsequent reaction with HBF4 led to the expected cationic monorhodium complexes 5 and 8 , involving 1, 3‐alternating P‐Rh‐P‐coordination. The cone conformation in solution was proved by NMR spectroscopy and characteristic values of the 1J(PRh) coupling constants in the 31P‐NMR‐spectra. Reaction of equimolar amounts of 4 with (cod)Rh(acac) or (nbd)Rh(acac) led, by substitution of the labile coordinated acetylacetonato and after addition of HBF4, to the corresponding mononuclear cationic complexes 9 and 10 . Only two of the four phosphorus atoms in 9 and 10 are coordinated to the central metal atom. Displacement of either cycloocta‐1, 5‐diene or norbornadiene was not observed. For both compounds, the cone conformation was proved by NMR spectroscopy. Reaction of 4 with (cod)PtCl2 led to the PtCl2‐complex ( 11 ). As for all compounds mentioned above, only two phosphorus atoms of the ligand coordinate to platinum, while two phosphorus atoms remain uncoordinated (proved by δ31P and characteristic values of 1J(PPt)). NMR‐spectroscopic evidence was found for the existence of the cone conformation in the cis‐configuration of 11 . 相似文献
86.
Christine Kunze Detlef Selent Ion Neda Matthias Freytag Peter G. Jones Reinhard Schmutzler Wolfgang Baumann Armin Brner 《无机化学与普通化学杂志》2002,628(4):779-787
New calix[4]arene‐based bis‐phosphonites, bis‐phosphites and bis‐O‐acylphosphites were synthesized and characterized. Treatment of these P‐ligands with selected rhodium and platinum precursors led to mononuclear complexes that were satisfactorily characterized. The solid state structure of the dirhodium(I) complex 14 has been determined by X‐ray diffraction. The two rhodium centres are bridged by two chloro ligands; one rhodium atom is further coordinated by calix[4]arene phosphorus atoms and the other by cyclooctadiene. The new calix[4]arene P‐ligands were tested in the Rh(I) catalyzed hydroformylation of 1‐octene. All Rh(I) complexes catalyzed the reaction leading to high chemoselectivity with regard to the formation of aldehydes. Yields and n/iso‐selectivities depended on the reaction conditions. Average yields of 80 % and n/iso‐ratios of about 1.3 to 1.5 were observed. High yields of aldehydes can be achieved using the methoxy substituted P‐ligands at low Rh:ligand ratios. 相似文献
87.
88.
The problem of existence of ground states in higher-order dispersion managed NLS equation is considered. The ground states are stationary solutions to dispersive equations with nonlocal nonlinearity which arise as averaging approximations in the context of strong dispersion management in optical communications. The main result of this note states that the averaged equation possesses ground state solutions in the practically and conceptually important case of the vanishing residual dispersions. 相似文献
89.
T. Spillane F. Raiola F. Zeng H. W. Becker L. Gialanella K. U. Kettner R. Kunze C. Rolfs M. Romano D. Schürmann F. Strieder 《The European Physical Journal A - Hadrons and Nuclei》2007,31(2):203-205
For the β--decay of 198Au in a Au metallic environment the half-life was observed to be longer by 0.4±0.7% at room temperature (T = 293K) and by 4.0±0.7% when the metal was cooled to T = 12K, both compared to the literature value of T
1/2 = 2.6943±0.0008d. 相似文献
90.