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951.
952.
Nonrelativistic and quasirelativistic energy-adjusted pseudopotentials for fixed 4f subconfigurations of the rare earth elements La through Lu together with corresponding optimized valence basis sets have been used in SCF and CI(SD) calculations to determine the spectroscopic constants for the energetically low lying superconfigurations of the lanthanide monohydrides, monoxides and monofluorides. The experimentally observed trends in dissociation energies, bond lengths and vibrational frequencies for the ground states of the calculated superconfigurations of the monoxides and monofluorides are well reproduced. The results for the monohydrides are mainly predictions. 相似文献
953.
O. Carugo C. Bisi Castellani A. Perotti 《Monatshefte für Chemie / Chemical Monthly》1993,124(6-7):681-687
Summary The yttrium(III) bonding to organic substrates (oximes, -diketonates and (poly)amino-(poly)carboxylates) has been compared with that of the lanthanoid(III) cations. The complexation constants of Y3+ with the examined organic ligands are similar to those of some cations of the first half of the lanthanoid series, in contrast with the fact that the Y3+ ionic dimensions are similar to those of Ho3+. This has been explained by correlating the formation constants of the Y3+ and the lanthanoids(III) complexes by the equation logK
1=C
ACB+E
AEB, where the parametersC andE indicate the tendency of each Lewis acidA and Lewis baseB to undergo covalent or ionic bonding, and where the ratioH=E/C indicates the charge control on the bond formation tendency of each speciesA orB. The results are commented in terms of the utility of Y3+ in assisting organic reactions.
Bindung von Yttrium(III) an organische Liganden: Vergleich mit Lanthanoid(III)-Kationen
Zusammenfassung Es wurde die Bindung von Yttrium(III) an organische Substanzen [Oxime, -Diketonate und (Poly)Amino(poly)carboxylate] im Vergleich mit Lanthanoid(III)-Kationen behandelt. Die Komplexierungskonstanten von Y3+ sind ähnlich denen einiger Kationen der ersten Hälfte der Lanthanoidenserie; dies steht im Gegensatz zur Tatsache, daß die Dimensionen des Y3+-Ions denen des Ho3+ entsprechen. Die Erklärung wurde mittels der für die Bildungskonstanten der Y3+- und Lanthanoid(III)-Komplexe gültigen Gleichung logK 1=C ACB+E AEB gefunden, wobeiC undE Parameter sind, die die Tendenz der Lewis-SäurenA und der Lewis-BasenB zum Eingehen von kovalenten oder ionischen Bindungen charakterisieren und wo das VerhältnisH=E/C den Steuerungseffekt der Ladung auf die Bindungstendenz der SpeziesA oderB beschreibt. Die Ergebnisse werden im Hinblick auf den Nutzen von Y3+ zur Unterstützung organischer Reaktionen diskutiert.相似文献
954.
O.L. Sologub L.P. Salamakha H. Noël A.P. Gonçalves 《Journal of solid state chemistry》2007,180(10):2740-2746
Two new compounds, La3Ru8B6 and Y3Os8B6, were synthesized by arc melting the elements. Their structural characterization was carried out at room temperature on as-cast samples by using X-ray diffractometry. According to X-ray single-crystal diffraction results these borides crystallize in Fmmm space group (no. 69), Z=4, a=5.5607(1) Å, b=9.8035(3) Å, c=17.5524(4) Å, ρ=8.956 Mg/m3, μ=25.23 mm−1 for La3Ru8B6 and a=5.4792(2) Å, b=9.5139(4) Å, c=17.6972(8) Å, ρ=13.343 Mg/m3, μ=128.23 mm−1 for Y3Os8B6. The crystal structure of La3Ru8B6 was confirmed from Rietveld refinement of X-ray powder diffraction data. Both La3Ru8B6 and Y3Os8B6 compounds are isotypic with the Ca3Rh8B6 compound and their structures are built up from CeCo3B2-type and CeAl2Ga2-type structural fragments taken in ratio 2:1. They are the members of structural series R(A)nM3n−1B2n with n=3 (R is the rare earth metal, A the alkaline earth metal, and M the transition metal). Structural and atomic parameters were also obtained for La0.94Ru3B2 compound from Rietveld refinement (CeCo3B2-type structure, P6/mmm space group (no. 191), a=5.5835(9) Å, c=3.0278(6) Å). 相似文献
955.
多氮杂大环的配位化学一直是人们感兴趣的领域。近年来,人们努力把支链配位基团引入大环中,以便得到同时具有相对刚性和动力学稳定性的大环结构单元和具有相对柔性和动力学活性的开链结构单元的新型配体。我们曾通过简单的立体化学选择合成得到一系列部分N-乙酸取代六甲基四氮杂大环。本文报道新的大环配体c-meso-meso-5,12-二苯基-7,14-二甲基-1,4,8,11-四氮杂环十四烷-N,N″-二乙酸(H_2L~3及其镧系配合物的合成和表征。 相似文献
956.
Polycrystalline samples of Ln3OsO7 (Ln=Pr,Nd,Sm) have been prepared. The structures of these compounds were determined by X-ray powder diffraction. They crystallize in a superstructure of cubic fluorite (space group Cmcm, Z=4). The samples have been characterized by magnetometry. The compounds show complex magnetic behavior at low temperatures caused by competing magnetic interactions leading to frustration. 相似文献
957.
Summary Partition chromatographic behaviour of the rare earth elements on C18 bonded silica reversed-phase material has been investigated by thin-layer chromatography in methanol — lactate media. The rare earth lactato complexes are distributed and fractionated on bonded silica layers without ion-interaction reagents. The concentration and pH of lactate solution, methanol concentration and temperature have effects on the migration and resolution of the rare earth elements. The partition system is particularly suited to separate adjacent rare earths of middle atomic weight groups, allowing the separation of gadolinium, terbium, dysprosium, holmium, erbium and thulium to be achieved by development to 18 cm distance. 相似文献
958.
Peter Rogl 《Monatshefte für Chemie / Chemical Monthly》1980,111(2):517-527
The crystal structure of LaIr4B4 has been refined from single crystal counter data. LaIr4B4 is tetragonal,P42/n,Z=2, isotypic with NdCo4B4, |F|/|F
o|=0.039 for 312 independent reflections [|F
o|>2 (F
o)]. ThIr4B4 and ThOs4B4 also belong to the NdCo4B4-type structure. URu4B4 and UOs4B4 were found to crystallize with LuRu4B4-type structure. The crystal chemistry of (RE)T
4B4-phases is discussed and simple geometric relations are shown to exist between them.Dedicated to Prof.B. T. Matthias in celebration of his 60th birthday. 相似文献
959.
Qian-Ming Wang 《Journal of organometallic chemistry》2006,691(17):3567-3573
The study concentrates on the syntheses of modified 2-hydroxynicotinic acid by 3-(triethoxysilyl)-propyl isocyanate (TESPIC) and the preparation of their corresponding organic-inorganic molecular-based hybrid material with the two components equipped with covalent bonds. The bridging unit is a derivative of 2-hydroxynicotinic acid which is utilized to coordinate to Tb3+, Eu3+ or Zn2+ and further occurred hydrolysis and polycondensation processes by functional triethoxysilyl groups. Ultraviolet absorption, phosphorescence spectra, and luminescence spectra were applied to characterize the photophysical properties of the obtained hybrid material and the above spectroscopic data present that the triplet energy of modified 2-hydroxynicotinic acid efficiently initiates the antenna effect and matches with the emissive energy level of metal ions. As a result, the intramolecular energy transfer process completed within these molecular-based hybrids and strong green or red emissions of Ln3+ have been obtained. 相似文献
960.
Revathy Rajagopal Vishnu R. Ajgaonkar 《Monatshefte für Chemie / Chemical Monthly》2002,133(11):1387-1395
Summary. Double rare earth monomethylammonium selenates of the general formula CH3NH3
Ln (SeO4)2·5H2O (Ln = Sm, Eu, Gd, Tb, Ho, Y) were synthesized and characterized using X-ray powder diffraction and infrared spectroscopy. The
thermal decomposition of the compounds were investigated using TG, DTG, and DTA techniques.
Corresponding author. E-mail: vrajgaonkar@yahoo.com, vrajgaonkar@mail.mu.ac.in
Received November 5, 2001. Accepted (revised) March 6, 2002 相似文献