全文获取类型
收费全文 | 129篇 |
免费 | 5篇 |
专业分类
化学 | 107篇 |
力学 | 1篇 |
数学 | 14篇 |
物理学 | 4篇 |
无线电 | 8篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2021年 | 1篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2016年 | 2篇 |
2015年 | 6篇 |
2014年 | 3篇 |
2013年 | 5篇 |
2012年 | 7篇 |
2011年 | 2篇 |
2010年 | 6篇 |
2009年 | 5篇 |
2008年 | 4篇 |
2007年 | 3篇 |
2006年 | 9篇 |
2005年 | 4篇 |
2004年 | 8篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 6篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1978年 | 1篇 |
1974年 | 2篇 |
1968年 | 1篇 |
1965年 | 1篇 |
1963年 | 1篇 |
1960年 | 1篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1939年 | 2篇 |
1933年 | 2篇 |
1925年 | 2篇 |
1922年 | 2篇 |
排序方式: 共有134条查询结果,搜索用时 15 毫秒
81.
We consider the wiring or layer assignment problem for edge-disjoint layouts. The wiring problem is well understood for the case that the underlying layout graph is a square grid (Lipski Jr. and Preparata, 1987). In this paper, we introduce a more general approach to this problem. For an edge-disjoint layout in the plane, respectively in an arbitrary planar layout graph, we give equivalent conditions for k-layer wirability. Based on these conditions, we obtain linear-time algorithms to wire every layout in a tri-hexagonal grid or a tri-square-hexagonal grid, respectively, using at most five layers. 相似文献
82.
Marquardt D Xie Z Taubert A Thomann R Janiak C 《Dalton transactions (Cambridge, England : 2003)》2011,40(33):8290-8293
The synthesis of Co-NPs and Mn-NPs by microwave-induced decomposition of the metal carbonyls Co(2)(CO)(8) and Mn(2)(CO)(10), respectively, yields smaller and better separated particles in the functionalized IL 1-methyl-3-(3-carboxyethyl)-imidazolium tetrafluoroborate [EmimCO(2)H][BF(4)] (1.6 ± 0.3 nm and 4.3 ± 1.0 nm, respectively) than in the non-functionalized IL 1-n-butyl-3-methylimidazolium tetrafluoroborate [Bmim][BF(4)]. The particles are stable in the absence of capping ligands (surfactants) for more than six months although some variation in particle size could be observed by TEM. 相似文献
83.
Dorothea Wolff von Gudenberg Irina Sens Ulrich Müller Bernhard Neumüller Kurt Dehnicke 《无机化学与普通化学杂志》1992,613(7):49-54
Chelate Complexes of Rhenium Tetrachloride. The Crystal Structures of ReCl4(DME) and ReCl4(DPPE) · Tolan Bright green crystals of ReCl4(DME) have been prepared by the reaction of rhenium pentachloride with dimethoxyethane (DME) in dichloromethane. ReCl4(DPPE) · tolan was obtained in form of red crystals by the reaction of the alkyne complex [ReCl4(Ph? C?C? Ph)(POCl3)] with bis(diphenylphosphino)ethane (DPPE) in dichloromethane. The complexes were characterized by X-ray structure determinations. ReCl4(DME): Space group I4 2d, Z = 8, 829 observed unique reflexions, R = 0.022. Lattice dimensions at 19.5°C: a = b = 960.60(6), c = 2337.2(6) pm. The complex forms monomeric molecules with DME as chelating ligand; the Re? O bond lengths are 213.1 pm. The chlorine atoms, arranged in trans position to the chelating ligand, have slightly shorter Re? Cl bonds than the chlorine atoms in cis position (232,1 pm). ReCl4(DPPE) · tolan: Space group P21/n, Z = 4,4313 observed unique reflexions, R = 0.040. Lattice dimensions at ?80°C: a = 1095.7(1), b = 1764.2(2), c = 1898.0(2) pm, β = 99.229(8)°. The compound consists in form of monomeric molecules [ReCl4(DPPE)] and diphenylacetylene molecules, which are incorporated in the lattice. The two phenyl rings of the tolan molecules are twisted towards each other along the C? C axis with a dihedral angle of 21°. The DPPE molecules are bonded to the rhenium atom in a chelating fashion with medium Re? P lengths of 250.4 pm. The chlorine atoms, arranged in trans position to this ligand, with Re? Cl bond lengths of 234.5 pm are slightly longer than the Re? Cl bonds in cis position with 232.3 pm. 相似文献
84.
J. W. Marden J. C. Ghosh H. T. Beans Dorothea R. Mossman J. Ciochina K. Roesch W. Werz H. Mathesius J. Arend H. Schnellenbach F. Spindeck A. Angeletti L. Moser K. Neumayer K. Winter J. Singer W. R. Schoeller C. Jahn H. W. Webb A. R. Powell H. Ginsberg F. P. Treadwell A. Gautier H. Hueber 《Analytical and bioanalytical chemistry》1933,93(5-6):203-222
85.
86.
Dr. Daniel Werner Uwe Bayer Dr. Dorothea Schädle Prof. Dr. Reiner Anwander 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(53):12194-12205
The cerium(IV) pyrazolate complexes [Ce(Me2pz)4]2 and [Ce(Me2pz)4(thf)] initiate β-hydride abstraction of the bis(dimethylsilyl)amido moiety, to afford a heteroleptic cerium(IV) species containing a dimethylpyrazolyl-substituted silylamido ligand, namely [Ce(Me2pz)3(bpsa)] (bpsa=bis((3,5-dimethylpyrazol-1-yl)dimethylsilyl)amido; Me2pz =3,5-dimethylpyrazolato), along with some cerium(III) species. Remarkably, the nucleophilic attack of the pyrazolyl at the silicon atom and concomitant Si−H-bond cleavage is restricted to the tetravalent cerium oxidation state and appears to proceed via the formation of a transient cerium(IV) hydride, which engages in immediate redox chemistry. When [Ce(Me2pz)4]2 is treated with [Li{N(SiMe3)2}], that is, in the absence of the SiH functionality, any redox chemistry did not occur. Instead, the ceric ate complex [LiCe2(Me2pz)9] and the stable mixed-ligand ceric species [Ce(Me2pz)2{N(SiMe3)2}2] were obtained. 相似文献
87.
88.
89.
Dong VM Fiedler D Carl B Bergman RG Raymond KN 《Journal of the American Chemical Society》2006,128(45):14464-14465
Iminium ions are known to exist only transiently in aqueous solution due to their high reactivity toward hydrolysis. In this communication, we report on the generation and stabilization of iminium ions in aqueous solution via molecular encapsulation using a K12Ga4L6 host. Our studies revealed that tetrahedral host 1 can encapsulate a variety of iminium cations in a molecular recognition process that is selective based on the charge, hydrophobicity, size, and shape of the guest. 相似文献
90.