全文获取类型
收费全文 | 295篇 |
免费 | 22篇 |
国内免费 | 2篇 |
专业分类
化学 | 246篇 |
力学 | 3篇 |
数学 | 49篇 |
物理学 | 21篇 |
出版年
2022年 | 5篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 8篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 21篇 |
2015年 | 7篇 |
2014年 | 5篇 |
2013年 | 15篇 |
2012年 | 20篇 |
2011年 | 25篇 |
2010年 | 9篇 |
2009年 | 10篇 |
2008年 | 17篇 |
2007年 | 22篇 |
2006年 | 22篇 |
2005年 | 13篇 |
2004年 | 18篇 |
2003年 | 17篇 |
2002年 | 10篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 6篇 |
1996年 | 1篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1969年 | 2篇 |
1967年 | 2篇 |
1964年 | 1篇 |
1962年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有319条查询结果,搜索用时 390 毫秒
291.
Victor Bassiloua Lahouari Ghaicha Mireille Privat René Bennes Emmanuel Tronel-Peyroz 《Journal of solution chemistry》1995,24(9):935-952
Activities of 2,5-dimethylpyridine in aqueous solution have been measured at eleven temperatures, two below and nine above the lower critical temperature of the mixture, by the dynamic method of Randall and Weber. Gibbs free energy, enthalpy and entropy are derived to obtain excess quantities and all the results are discussed in connection with the liquid-liquid phase separation, the critical situation and the association properties of the molecules. A comparison is also made with the aqueous 2,6-dimethylpyridine system. A new version of the phase diagram is proposed. 相似文献
292.
We encompass the Moreau-Yosida regularization process by infimal convolution into a general framework. This sheds light on the assumptions required for obtaining the usual properties. In particular the class of lower-T2 mappings is shown to be a suitable class for performing the usual proximal regularization in open subsets of Hilbert spaces. The role of growth conditions is pointed out. 相似文献
293.
Michel Betrencourt Mireille Morillon-Chapey Pierre Pinson 《International Journal of Infrared and Millimeter Waves》1981,2(3):493-524
Thev
2(A1) andv
5(E) fundamental vibration-rotation bands of12CH3F have been recorded under high resolution (0.015 to 0.020 cm–1) in the spectral range of 1460 cm–1. About 1100 transitions have been assigned. The Coriolis interaction between v2=1 and v5=1, and the l(2,-1) interaction in v5=1 have been rigorously treated. Sixteen molecular constants have been determined from a least squares analysis. They reproduce the observed data with an overall standard deviation of 0.0037 cm–1. 相似文献
294.
The synthesis and the characterization of triphenylbenzene-cored dendrimers of first- and second-generation are described. Their absorption, photoluminescence as well as their two-photon absorption properties have been investigated and compared to a quadrupolar counterpart. These molecules combine wide transparency in the visible range and high two-photon absorption cross-sections that increase with the generation, making these dendrimers promising systems for optical power limiting applications. 相似文献
295.
Olivier Mongin Laurent PorrèsClaudine Katan Thomas PonsJerome Mertz Mireille Blanchard-Desce 《Tetrahedron letters》2003,44(44):8121-8125
Two new three-branched fluorenylene-vinylene derivatives were synthesized by triple Heck-type or Horner-Wadsworth-Emmons reactions. Their one-photon absorption and fluorescence as well as their two-photon absorption properties are reported. These compounds, which combine very high solubility in organic solvents, high fluorescence quantum yield and giant two-photon absorption cross-sections in the red-NIR region (up to 3660 GM, in the femtosecond regime) are promising candidates for both optical power limiting applications and two-photon laser scanning microscopy. 相似文献
296.
A new lanthanide citrate motif of general formula [Ln(Hcit)(H2O)2.H2O]n, where Ln = Gd (1) and Nd (2) and Hcit3- = C(OH)(COO-)(CH2COO-)2, has been synthesized hydrothermally from Ln2O3 and citric acid at 100 degrees C and characterized by elemental analysis, IR, TG-DTA, single-crystal X-ray diffraction, and magnetic measurements. The structures can be seen as "ladder chains" along the a axis, with dinuclear Ln2O2 units serving as "steps" and R-COO groups as "uprights", which are connected by H bonds. The magnetic susceptibility between 2 and 300 K and the magnetization at 2 K, as a function of magnetic field between 0 and 5 T, were measured for both compounds. By modeling the magnetic behavior of the Gd compound with a dinuclear Hamiltonian [symbol: see text](S) = gmu(B)(S(A) + S(B))B(o) - J(o)S(A)S(B) (S(A) = S(B) = 7/2), a ferromagnetic exchange interaction J(o) = 0.039 cm(-1) was evaluated between Gd ions situated at d(o) = 4.321 angstroms in dinuclear units bridged by two symmetry-related tridentate carboxylate oxygens. The EPR spectrum of the Gd compound is discussed. The temperature dependence of the susceptibility of the Nd compound is caused by the depopulation of the excited crystal-field levels when the temperature decreases. The magnetic-field dependence of the magnetization of 2 is attributed to the ground-state Kramers' doublet populated at 2 K. The g factor of this ground-state doublet is calculated from the data and compared with values for other compounds reported in the literature. 相似文献
297.
Cogné-Laage E Allemand JF Ruel O Baudin JB Croquette V Blanchard-Desce M Jullien L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(6):1445-1455
This paper evaluates the use of diaroyl(methanato)boron difluoride compounds for designing efficient fluorescent probes through two-photon absorption. Three different pathways allowing for the syntheses of symmetrical and dissymmetrical molecules are reported. The stable diaroyl(methanato)boron difluoride derivatives can be easily obtained in good yields. They exhibit a large one-photon absorption that is easily tuned in the near-UV range. Their strong fluorescence emission covers the whole visible domain. In addition to these attractive linear properties, several diaroyl(methanato)boron difluoride derivatives possess significant cross sections for two-photon absorption. The derived structure-property relationships are promising for designing new generations of molecules relying on the diaroyl(methanato)boron difluoride backbone. 相似文献
298.
299.
300.
Laurent De Windt Mireille Defranceschi Joseph Dehalle 《International journal of quantum chemistry》1993,45(6):609-618
A method using the Svartholm iterative procedure to solve atomic Hartree–Fock equations in momentum space is defined and applied to the ground states of Be and B+. The calculated atomic orbital properties follow a monotonic and stable convergence, but with rates of convergence depending on each property. The evolution of the orbitals during the iterations is explained by the combined actions of the variational principle, the Svartholm iterative procedure, and the momentum space representation. © 1993 John Wiley & Sons, Inc. 相似文献