全文获取类型
收费全文 | 139篇 |
免费 | 0篇 |
专业分类
化学 | 77篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 24篇 |
物理学 | 36篇 |
出版年
2016年 | 2篇 |
2013年 | 4篇 |
2012年 | 3篇 |
2011年 | 5篇 |
2009年 | 3篇 |
2008年 | 2篇 |
2007年 | 8篇 |
2006年 | 3篇 |
2005年 | 7篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1993年 | 7篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1981年 | 6篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1974年 | 3篇 |
1970年 | 1篇 |
1966年 | 2篇 |
1960年 | 1篇 |
1948年 | 1篇 |
1941年 | 2篇 |
1937年 | 1篇 |
1936年 | 1篇 |
1935年 | 1篇 |
1932年 | 5篇 |
1930年 | 1篇 |
1928年 | 3篇 |
1927年 | 4篇 |
1926年 | 1篇 |
1925年 | 6篇 |
1924年 | 1篇 |
1923年 | 1篇 |
排序方式: 共有139条查询结果,搜索用时 140 毫秒
1.
2.
The influence of humic substances on sorption and methylation processes for inorganic- and organotin species is presented. Four sediment samples from different locations of the Rivers Elbe, Mulde and Spittelwasser, Germany, with different organotin and humic contents were selected to extract the humic and fulvic acids. The various fractions—the original sediment, the humic acid, the fulvic acid and the residual sediment—were analysed for their organotin content. The individual buyltin species show quite different distribution patterns. Monobutyltin is found mostly associated with humic acids. Dibutyltin shows a nonunique behaviour. At low total organotin content, dibutyltin is found bonded to humic and fulvic acids, whereas at high organotin content dibutyltin is distributed more with the residual sediment. Most of the tributyltin remains in the sediment unextracted; only small quantities of it are in the fulvic acid fraction. Tetrabutyltin is only in the humic acid fraction when it binds to humic matter; it mostly remains in the sediment. General observations indicate that ionic butyltin species bind to fulvic acids whereas the non-polar tetrabutyltin is not found in the fulvic acid fractions in any of the samples. The appearance of monomethyl- and dimethyl-tin species in the humic and fulvic acid fractions after the alkaline extraction was surprising. There is a correlation between the humic content of the sample and the formation of methyltin species. Evidence is provided by experiments that humic substances act as methylation agents. 相似文献
3.
4.
S. Francis Amevor Hans-Ulrich Hund Albrecht Salzer 《Journal of organometallic chemistry》1996,520(1-2):79-84
A series of heterodimetallic complexes of general formula (C5R5)M(μ-CO)3RuC5Me5 (M = Cr, Mo, W; R = Me, Et) has been prepared in good yields by the reaction of [C5R5M(CO)3]− with [C5Me5Ru(CH3CN)3]+. (C5Me4Et)W(μ-CO)3Ru(C5Me5) was characterized by a crystal structure determination. The W---Ru bond length of 2.41 Å is consistent with the formulation of a metal-metal triple bond, while the unsymmetrical bonding mode of the three bridging carbonyl groups reflects the inherent non-equivalence of the two different C5R5M-units. Using [CpRu(CH3CN)3]+ or [CpRu(CO)2(CH3CN)]+ as the cationic precursor leads to the formation of dimetallic species (C5R5)M(CO)5RuC5H5 with both bridging and terminal carbonyl groups. 相似文献
5.
Ute Ch.?Rodewald Mar’yana?Lukachuk Rolf-Dieter?Hoffmann Rainer?P?ttgenEmail author 《Monatshefte für Chemie / Chemical Monthly》2005,136(12):1985-1991
Summary. The gadolinium–rhodium–indide Gd3Rh1.940(7)In4 was prepared by arc-melting of the elements and subsequent annealing in a corundum crucible in a sealed silica tube. Gd3Rh1.940(7)In4 adopts the hexagonal Lu3Co1.87In4 type, space group
, a = 781.4(5), c = 383.8(3) pm, wR2 = 0.0285, BASF = 0.375(1) (merohedric twinning via a twofold axis (xx0)), 648 F2 values, 22 variables. The structure is derived from the well known ZrNiAl type through an ordering of rhodium and indium
atoms on the Ni2 sites. The Rh/In ordering forces a reduction of the space group symmetry from
to
, leading to merohedric twinning for the investigated crystal. The Rh1 site has an occupancy of only 94.0(7)%. The investigated
crystal had a composition Gd3Rh1.940(7)In4. The main geometrical motif are three types of centered, tricapped trigonal prisms, i.e., [Rh1In26Gd3], [Rh2Gd6In23], and [In1Gd6In23]. The shortest interatomic distances occur for Rh–In (276–296 pm) followed by In–In (297 pm). Together, the rhodium and indium
atoms build up a three-dimensional [Rh1.940(7)In4] network, in which the gadolinium atoms fill slightly distorted pentagonal channels. The crystal chemistry of Gd3Rh1.940(7)In4 is discussed on the basis of a group-subgroup scheme. 相似文献
6.
The chemistry of [Re(CO)(NO)L2] fragments (L ? phosphorus donor) was explored. Starting from [Re(CO)5Cl] the synthesis of [Re2Cl2(μ-Cl)2(CO)4(NO)2] ( 1 ) was accomplished via the preparation of [Et4N]2[Re2Cl2(μ-Cl)2(CO)6] and nitrosylation of this compound with [NO][BF4]. Complex 1 was converted to [RecL2(CO)(NO)L2] complexes 2 ( a L = (MeO)3P; b L = (EtO)3P; c L = (i-PrO)3P; d L ? Me3P; e L ? Et3P; f L ? Cy3P) by heating with L in MeCN. In the case of the reaction of L = (MeO)3P, a trisubstitued compound mer-{ReCl2(NO)[P(OMe)3]3} 3 was also obtained. Replacement of the Cl ligands in 2a–e with Me groups was achieved by reacting them with MeLi in Et2O yielding cis, trans-[Re(CO)(NO)Me2L2]complexes 4a–e . Reaction of 2a–e with Li[BHEt3] led to substitution of one Cl by an H ligand with formation of [ReCl(CO)H(NO)L2] compounds 5a–;e , displaying trans-H,NO geometries. The hydride-transfer agent Na[AlH2(OCH2CH2OCH3)2] transformed 2 into the cis-dihydride systems [Re(CO)H2(NO)L2] 6a–f . Reductive carbonylation of 2a–d in the presence of Na/Hg and CO gave pentacoordinate [Re(CO)2(NO)L2] complexes 7b–d , and under comparable conditions the Cl substituents of 2b–f were replaced by tolane using Mg or t-BuLi giving trigonal bipyramidal [Re(CO)(NO)L2(PhC?CPh)] compounds 8b–f . Complexes 5c , 6a , and 8d were characterized by X-ray crystal-structure analysis. 相似文献
7.
Single crystals of SrIr9In18 were obtained by induction melting of the elements in a glassy carbon crucible followed by annealing at 1070 K. SrIr9In18 was structurally characterized by X-ray powder and single crystal diffraction: P4 m2, a = 811.21(5), c = 854.49(5) pm, wR2 = 0.0511, 1223 F2 values, and 46 variables. The structure is of a new type. The basic building units are Ir@In8 (distorted square-prismatic, square anti-prismatic and bicapped trigonal prismatic coordination) and Ir@In9 (distorted trigonal prismatic coordination) polyhedra, which condense to a three-dimensional network, which leaves large cavities for the strontium cations, which are coordinated to four iridium and twelve indium atoms. The [Ir9In18]2– polyanionic network is stabilized through Ir–In (267–290 pm) and In–In (302–354 pm) bonding. 相似文献
8.
9.
10.