全文获取类型
收费全文 | 612篇 |
免费 | 80篇 |
国内免费 | 93篇 |
专业分类
化学 | 619篇 |
晶体学 | 5篇 |
力学 | 1篇 |
综合类 | 4篇 |
数学 | 2篇 |
物理学 | 154篇 |
出版年
2024年 | 2篇 |
2023年 | 8篇 |
2022年 | 18篇 |
2021年 | 13篇 |
2020年 | 38篇 |
2019年 | 24篇 |
2018年 | 20篇 |
2017年 | 14篇 |
2016年 | 35篇 |
2015年 | 31篇 |
2014年 | 42篇 |
2013年 | 100篇 |
2012年 | 47篇 |
2011年 | 39篇 |
2010年 | 25篇 |
2009年 | 43篇 |
2008年 | 39篇 |
2007年 | 20篇 |
2006年 | 24篇 |
2005年 | 31篇 |
2004年 | 17篇 |
2003年 | 19篇 |
2002年 | 27篇 |
2001年 | 5篇 |
2000年 | 11篇 |
1999年 | 11篇 |
1998年 | 6篇 |
1997年 | 10篇 |
1996年 | 14篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1986年 | 2篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有785条查询结果,搜索用时 0 毫秒
51.
吡啶—2,6—二羧酸体系导数荧光法同时测定铀,钐,铕,铽,镝 总被引:4,自引:0,他引:4
本研究了吡啶-2,6-二羧酸(DPA)体系导数荧光法同时测定铀,钐,铕,铽,镝的最佳条件。在pH5.5,4.8×10^-^5mol/LDPA,激发波长272nm的条件下,可分别在518,639,621,539和66nm处测定铀,钐,铕,铽和镝,检测限分别达到7,0.4,0.004,0.026和0.25ng/mL。应用本法测定了混合成试液中上术五种离子含量,回收率为92.3-108.1%。 相似文献
52.
According to the experiment results of X-ray diffraction and IR, the reduced partition function ratio (RPFR) and the contribution of various related vibration modes of uranium-crown ether complex (DCH18C6·H_3O)_2UO_2Cl_4 were theoreticallv calculated in detail. The equilibrium constant K_(eq) (that is, the single stage isotopic separation factor α) of exchange reaction for uranium isotopic chemical exchange system UO_2~(2+)(H_2O)_5—(DCH18C6.H_3O)_2UO_2Cl_4 is estimated to be 1.000746 at 12℃ and 1.000672 at 29℃, respectively, which are quite close to the experimental values 1.0010±0.0002 arid 1.0012±0.0004. Theoretical analysis shows that in the course of forming the complex of uranium with crown ether, the coordinated water of uranium is stripped, which performs a key action on the remarkable isotope effect for this system. 相似文献
53.
Karl Krmer Hans U. Güdel Gerd Meyer Thorsten Heuer Norman N. Edelstein Bernd Jung Lukas Keller Peter Fischer Eugeniusz Zych Janusz Drozdzynski 《无机化学与普通化学杂志》1994,620(8):1339-1345
The ternary uranium(III) halides A2UX5 (A = K, Rb; X = Cl, Br, I) have been prepared from the binary components AX and UX3 in sealed tantalum containers. According to their Guinier X-ray powder patterns, they all crystallize with the K2PrCl5/Y2HfS5 type of structure. Lattice constants for ambient temperature are reported. Single-crystal structure refinemens were undertaken for K2UI5 and Rb2UCl5. Magnetic susceptibility data were recorded with a SQUID magnetometer from liquid helium to room temperature. One-dimensional (intrachain) and three-dimensional antiferromagnetic ordering occur at low temperatures dependent upon the U3+? U3+ distance. Absorption spectra were recorded between 4 000 and 28 000 cm?1. They show f—f transitions typical for U3+ and, depending on the halide, very strong f—d transitions above 14 000 to 15 000 cm?1, respectively. 相似文献
54.
55.
Conrad A. P. Goodwin Dr. Floriana Tuna Prof. Eric J. L. McInnes Prof. Stephen T. Liddle Dr. Jonathan McMaster Dr. Inigo J. Vitorica‐Yrezabal Dr. David P. Mills 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(45):14579-14583
We report the synthesis and characterization of the uranium(III) triamide complex [UIII(N**)3] [ 1 , N**=N(SiMe2tBu)2?]. Surprisingly, complex 1 exhibits a trigonal planar geometry in the solid state, which is unprecedented for three‐coordinate actinide complexes that have exclusively adopted trigonal pyramidal geometries to date. The characterization data for [UIII(N**)3] were compared with the prototypical trigonal pyramidal uranium(III) triamide complex [UIII(N“)3] (N”=N(SiMe3)2?), and taken together with theoretical calculations it was concluded that pyramidalization results in net stabilization for [UIII(N“)3], but this can be overcome with very sterically demanding ligands, such as N**. The planarity of 1 leads to favorable magnetic dynamics, which may be considered in the future design of UIII single‐molecule magnets. 相似文献
56.
A. P. Zazhogin A. A. Zazhogin A. I. Komyak D. S. Umreiko 《Journal of Applied Spectroscopy》2007,74(5):622-625
We have studied the effect of irradiation on the uranyl nitrate — acetone and uranyl perchlorate — acetone systems. We have
established that when the uranyl perchlorate — acetone system is irradiated, polymerization of the acetone occurs and the
catalyst for the process is excited uranyl complexes. In the polymer, uranium is found in the form of nanoclusters of pentavalent
and tetravalent uranium, formed as a result of photochemical reactions. Polymerization does not occur in the uranyl nitrate
— acetone system. We consider possible factors responsible for the noted differences.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 565–568, September–October, 2007. 相似文献
57.
Prof. Dr. Skye Fortier José Veleta Dr. Amélie Pialat Jennifer Le Roy Kamran B. Ghiassi Prof. Dr. Marilyn M. Olmstead Dr. Alejandro Metta‐Magaña Prof. Dr. Muralee Murugesu Prof. Dr. Dino Villagrán 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(6):1931-1936
After more than 50 years, the synthesis and electronic structure of the first and only reported “U0 complex” [U(bipy)4] ( 1 ) has been reinvestigated. Additionally, its one‐electron reduced product [Na(THF)6][U(bipy)4] ( 2 ) has been newly discovered. High resolution crystallographic analyses combined with magnetic and computational data show that 1 and its derivative 2 are best described as highly reduced species containing mid‐to‐high‐valent uranium ligated by redox non‐innocent ligands. 相似文献
58.
Dr. Rudolf C. Hoffmann Maximilian Trapp Dr. Emre Erdem Dr. Markus Kratzer Prof. Dr. Christian Teichert Prof. Dr. Hans-Joachim Kleebe Prof. Dr. Jörg J. Schneider 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(42):9319-9329
Cobalt-doped zinc oxide single crystals with the shape of hexagonal platelets were synthesized by thermohydrolysis of zinc acetate, cobalt acetate, and hexamethylenetetramine (HMTA) in mixtures of ethanol and water. The mineralization proceeds by a low-temperature dissolution–reprecipitation process from the liquid phase by the formation of basic cobalt zinc salts as intermediates. The crystal shape as well as twin formation of the resulting oxide phase can be influenced by careful choice of the solvent mixture and the amount of doping. An understanding of the course of the reaction was achieved by comprehensive employment of analytical techniques (i.e., SEM, XRD, IR) including an in-depth HRTEM study of precipitates from various reaction stages. In addition, EPR as well as UV/Vis spectroscopic measurements provide information about the insertion of the cobalt dopant into the zincite lattice. The Langmuir–Blodgett (LB) technique is shown to be suitable for depositing coatings of the platelets on glass substrates functionalized with polyelectrolyte multilayers and hence is applied for the formation of monolayers containing domains with ordered tessellation. No major differences are found between deposits on substrates with anionic or cationic surface modification. The adherence to the substrates is sufficient to determine the absolute orientation of the deposited polar single crystals by piezoresponse force microscopy (PFM) and Kelvin probe force microscopy (KPFM) studies. 相似文献
59.
Dr. Erli Lu Josef T. Boronski Dr. Matthew Gregson Dr. Ashley J. Wooles Prof. Stephen T. Liddle 《Angewandte Chemie (International ed. in English)》2018,57(19):5506-5511
Unprecedented silyl‐phosphino‐carbene complexes of uranium(IV) are presented, where before all covalent actinide–carbon double bonds were stabilised by phosphorus(V) substituents or restricted to matrix isolation experiments. Conversion of [U(BIPMTMS)(Cl)(μ‐Cl)2Li(THF)2] ( 1 , BIPMTMS=C(PPh2NSiMe3)2) into [U(BIPMTMS)(Cl){CH(Ph)(SiMe3)}] ( 2 ), and addition of [Li{CH(SiMe3)(PPh2)}(THF)]/Me2NCH2CH2NMe2 (TMEDA) gave [U{C(SiMe3)(PPh2)}(BIPMTMS)(μ‐Cl)Li(TMEDA)(μ‐TMEDA)0.5]2 ( 3 ) by α‐hydrogen abstraction. Addition of 2,2,2‐cryptand or two equivalents of 4‐N,N‐dimethylaminopyridine (DMAP) to 3 gave [U{C(SiMe3)(PPh2)}(BIPMTMS)(Cl)][Li(2,2,2‐cryptand)] ( 4 ) or [U{C(SiMe3)(PPh2)}(BIPMTMS)(DMAP)2] ( 5 ). The characterisation data for 3 – 5 suggest that whilst there is evidence for 3‐centre P?C?U π‐bonding character, the U=C double bond component is dominant in each case. These U=C bonds are the closest to a true uranium alkylidene yet outside of matrix isolation experiments. 相似文献
60.
Die Eignung organischer Elektrolyselösungen für die elektrolytische Abscheidung von Thorium wurde geprüft. Äthanol, Äthanol-Aceton-Mischung und Aceton gestatten innerhalb von ca. 10 Minuten Elektrolysedauer die vollständige Abscheidung von Thorium in einem weiten Massebereich. Der Einfluß von Wasseranteilen auf die Abscheidegeschwindigkeit wurde untersucht. Die Auswahtl der geeignetsten Elektrolyselösung erfolgte anhand der Reproduzierbarkeil der Homogenitätt abgeschiedener Schichten. Anwendungsbeispiele weisen sowohl auf die Eignung der Verfahren hin als auch auf Probleme, wie sie bei der Herstellung von Meßproben mit alpha-aktiven Substanzen geringer spezifischer Aktivität für die alpha-spetrometrische Auswertung zu berücksichtigen sind. 相似文献