全文获取类型
收费全文 | 516篇 |
免费 | 24篇 |
国内免费 | 6篇 |
专业分类
化学 | 442篇 |
晶体学 | 4篇 |
力学 | 2篇 |
数学 | 18篇 |
物理学 | 80篇 |
出版年
2023年 | 6篇 |
2022年 | 5篇 |
2021年 | 16篇 |
2020年 | 28篇 |
2019年 | 28篇 |
2018年 | 7篇 |
2017年 | 10篇 |
2016年 | 17篇 |
2015年 | 16篇 |
2014年 | 19篇 |
2013年 | 29篇 |
2012年 | 42篇 |
2011年 | 40篇 |
2010年 | 16篇 |
2009年 | 16篇 |
2008年 | 46篇 |
2007年 | 28篇 |
2006年 | 22篇 |
2005年 | 31篇 |
2004年 | 22篇 |
2003年 | 18篇 |
2002年 | 18篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 5篇 |
1972年 | 1篇 |
排序方式: 共有546条查询结果,搜索用时 31 毫秒
531.
Takumi Kongo 《Mathematical Social Sciences》2011,62(2):114-119
This paper studies cooperative games with restricted cooperation among players. We define situations in which a priori unions and hypergraphs coexist simultaneously and mutually depend on each other. We call such structures two-layered hypergraphs. Using a two-step approach, we define a value of the games with two-layered hypergraphs. The value is characterized by Owen’s coalitional value of hypergraph-restricted games and in terms of weighted Myerson value. Further, our value is axiomatically characterized by component efficiency and a coalition size normalized balanced contributions property. 相似文献
532.
A series of chiral M(6)M'(8) cluster compounds having twelve free carboxylate groups, [M(6)M'(8)(D-pen-N,S)(12)X](5-) (M/M'/X = Pd(II)/Ag(I)/Cl(-) ([1](5-)), Pd(II)/Ag(I)/Br(-) ([2](5-)), Pd(II)/Ag(I)/I(-) ([3](5-)), Ni(II)/Ag(I)/Cl(-) ([4](5-)), Pt(II)/Ag(I)/Cl(-) ([5](5-)), Pd(II)/Cu(I)/Cl(-) ([6](5-)); D-H(2)pen = D-penicillamine), in which six cis-[M(D-pen-N,S)(2)](2-) square-planar units are bound to a [M'(8)X](7+) cubic core through sulfur-bridges, was synthesized by the reactions of cis-[M(D-pen-N,S)(2)](2-) with M' in water in the presence of halide ions. These M(6)M'(8) clusters readily reacted with La(3+) in aqueous buffer to form La(III)(2)M(6)M'(8) heterotrimetallic compounds, La(2)[1](CH(3)COO), La(2)[2](CH(3)COO), La(2)[3](CH(3)COO), La(2)[4](CH(3)COO), La(2)[5](CH(3)COO) and La(2)[6]Cl, in which the M(6)M'(8) cluster units are linked by La(3+) ions through carboxylate groups in a 1?:?2 ratio. While the La(III)(2)M(6)Ag(I)(8) compounds derived from [1](5-), [2](5-), [3](5-), [4](5-) and [5](5-) have a 1D helix supramolecular structure with a right-handedness, the La(III)(2)Pd(II)(6)Cu(I)(8) compound derived from [6](5-) has a 2D sheet-like structure with a triangular grid of the Pd(II)(6)Cu(I)(8) cluster units. When aqueous HCl was added to the reaction solution of [6](5-) and La(3+), another La(III)(2)Pd(II)(6)Cu(I)(8) heterotrimetallic compound, La(2)[6]Cl·HCl, in which the Pd(II)(6)Cu(I)(8) cluster units are linked by La(3+) ions to form a 2D structure with a rectangular grid, was produced. The solid-state structures of these La(III)(2)M(6)M'(8) compounds, determined by single-crystal X-ray crystallography, along with the spectroscopic properties of the M(6)M'(8) cluster compounds in solution, are described. 相似文献
533.
Tamura M Tsuge K Igashira-Kamiyama A Konno T 《Chemical communications (Cambridge, England)》2011,47(46):12464-12466
Treatment of [Os(bpy)(2)Cl(2)] (bpy = 2,2'-bipyridine) with 2-aminoethanethiolate was accompanied by air oxidation to give [Os(2-aminoethanesulfinato-N,S)(bpy)(2)](+) ([1](+)), which was further oxidized by air to be converted into [Os(2-iminoethanesulfinato-N,S)(bpy)(2)](+) ([2](+)) under photoirradiation. Complex [2](+) was reverted back to [1](+) by treatment with BH(4)(-). 相似文献
534.
535.
Surinder K. Mehta Yosuke Imai Hiroki Takumi Kinue Shibata Hiroyasu Sakamoto Takanori Takiue Hiroki Matsubara Makoto Aratono 《Colloid and polymer science》2013,291(11):2647-2652
The temperature-dependent conformational states of a monolayer film of ethylene glycol monododecyl ether (C12E1) at the air/water interface have been investigated using ellipsometry, surface tension, external reflection–absorption FTIR spectroscopy and two-dimensional infrared (2DIR) correlation analysis. The ellipticity coefficients and the entropy associated with C12E1 adsorption changed almost discontinuously at certain temperatures, which manifested the interfacial phase transitions. The phase transition and coexistence of two phases were further clarified using 2DIR correlation analysis with temperature perturbation. The asynchronous correlation maps revealed that both bands of asymmetric and symmetric C–H stretching vibration in one-dimensional IR were split into two components, which confirmed the coexistence of two phases at the interface. 相似文献
536.
Sachi Taniyasu Kurunthachalam Kannan Qian Wu Karen Y. Kwok Leo W.Y. Yeung Paul K.S. Lam Brock Chittim Takafumi Kida Takumi Takasuga Yoshiteru Tsuchiya Nobuyoshi Yamashita 《Analytica chimica acta》2013
The ISO 25101 (International Organization for Standardization, Geneva) describes a new international standard method for the determination of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) in unfiltered samples of drinking and surface waters. The method is based on the extraction of target analytes by solid phase extraction, solvent elution, and determination by high performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS). For the determination of the performance of this method, more than 20 laboratories from 9 different countries participated in an inter-laboratory trial in 2006. In addition, inter-laboratory trials were conducted in 2008 and 2009 for the analysis of perfluoroalkylsubstances (PFASs), including PFOS and PFOA, in water samples by following the protocols of Japanese Industrial Standard (JIS). Overall, the repeatability coefficients of variation (i.e., within-laboratory precision) for PFOS and PFOA in all water samples were between 3 and 11%, showing a adequate precision of the ISO and JIS methods. The reproducibility coefficients of variation (i.e., between-laboratory precision) were found to vary within a range of 7–31% for surface water and 20–40% for wastewater. The recoveries of PFOS and PFOA, as a measure of accuracy, varied from 84 to 100% for surface water and from 84 to 100% for wastewater among the samples with acceptable criteria for internal standards recovery. The determined concentrations of PFASs in samples compared well with the “true” values. The results of the inter-laboratory trial confirmed that the analytical methods are robust and reliable and can be used as a standard method for the analysis of target compounds in water samples. 相似文献
537.
Commercially useful aromatic urea herbicides were synthesized in good yields from lithium amides of aromatic amines with thiocarbamates, which were prepared by the selenium-assisted carbonylation of secondary amines with carbon monoxide and sulfur under mild conditions. 相似文献
538.
539.
Takeda M Kusano T Matsunaga T Endo H Shibayama M Shikata T 《Langmuir : the ACS journal of surfaces and colloids》2011,27(5):1731-1738
Shear-induced thickening/thinning phenomena of aqueous rodlike micellar solutions of cetyltrimethylammonium bromide (CTAB) and sodium p-toluene sulfonate (NapTS) were investigated by means of simultaneous measurements of rheology and small-angle neutron scattering (SANS), the so-called Rheo-SANS. The aqueous CTAB/NapTS solutions were classified into five different categories dependent on their flow behavior and micellar structure. By increasing salt concentration and/or shear rates, the micelles underwent morphological transition from (i) spherical or short rodlike micelles to (ii) long rodlike micelles without entanglements, followed by (iii) those with entanglements. These transitions were recognized as changes in flow behavior from Newtonian to shear-thickening and shear-thinning flow, respectively. In the latter two cases, anisotropic SANS patterns appeared around these critical shear rates. The physical meaning of the anisotropic SANS patterns accompanied by shear-thickening flow behavior is discussed in conjunction with other shear-thickening systems. 相似文献
540.
Youhei ShimogoriTakefumi Hamamatsu Takeshi FujinamiHiroaki Hagiwara Naohide Matsumoto Nazzareno ReJerzy Mrozinski Yuichi IshikawaAsako Igashira-Kamiyama Takumi Konno 《Polyhedron》2011,30(6):1127-1133
A linear tetranuclear CuII-GdIII-CuII-GdIII complex [CuIILdpen(meso)GdIII(thd)2(H2O)]2 was synthesized from the reaction of [NaCuIILdpen(meso)(DMF)] with [GdIII(thd)3(H2O)2], and the structures and magnetic properties were investigated, where H3Ldpen(meso) = meso-1,2-diphenyl-1-(2-hydroxybenzamido)-2-(2-hydroxy-3-ethoxybenzylideneamino)ethane and Hthd = 2,2,6,6-tetramethyl-3,5-heptanedione. The CuII complex component [NaCuIILdpen(meso)(DMF)] has a one-dimensional (1D) chain structure, in which the Na+ ion is coordinated by two phenoxo and an ethoxy oxygen atoms of a CuII complex and an amido oxygen atom of the adjacent CuII unit to produce the 1D structure, in which the diphenylethylenediamine moieties have the array of {(1R,2S)-Na-(1S,2R)}1∞. The assembly reaction of the CuII and GdIII components gave a linear complex with the array of Cu(1)-Gd(1)-Cu(2)-Gd(2), in which two diphenylethylenediamine moieties have the same chirality of (1R,2S)-(1R,2S) or (1S,2R)-(1S,2R). Two linear Cu(1)-Gd(1)-Cu(2)-Gd(2) units are linked by hydrogen bonds through two water molecules to give a cyclic structure with a center of symmetry. The temperature dependence of the magnetic susceptibilities and field-dependent magnetization revealed the ferromagnetic interaction between the CuII and GdIII ions within the linear chain. 相似文献