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71.
72.
Archimede Rotondo Giuseppe Bruno Francesco Nicol Giuseppe Tresoldi Santo Di Pietro 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(1):o15-o19
The structure of 2,6‐bis(2‐pyridyltsulfanylmethyl)pyridine (pytmp), (I), C17H15N3S2, presents a twisted conformation, with the three planar moieties almost perpendicular to each other. The structures of two related derivatives, namely 2,6‐bis(6‐methyl‐2‐pyridylsulfanylmethyl)pyridine (mpytmp), (II), C19H19N3S2, and 2,6‐bis(4‐methyl‐2‐pyrimidylsulfanylmethyl)pyridine (mprtmp) n‐pentane hemisolvate, (III), C17H17N5S2·0.5C5H12, present extended planar fragments with just one quasi‐perpendicular arylsulfanylmethyl side arm, such that the molecules are folded in an L‐shaped conformation. All three conformations appear different from those adopted by similar compounds, demonstrating the great flexibility of such species, although such differences in conformational behaviour might drive specific coordination modes. 相似文献
73.
R. Albrecht T. C. Awes P. Beckmann F. Berger M. A. Bloomer D. Bock R. Bock G. Claesson G. Clewing L. Dragon A. Eklund R. L. Ferguson A. Franz S. Garpman R. Glasow H. Å. Gustafsson H. H. Gutbrod M. Hartig G. Hölker J. Idh P. Jacobs K. H. Kampert B. W. Kolb P. Kristiansson H. Löhner I. Lund F. E. Obenshain A. Oskarsson I. Otterlund T. Peitzmann S. Persson F. Plasil A. M. Poskanzer M. Purschke H. G. Ritter B. Roters S. Saini R. Santo H. R. Schmidt R. Schmidt S. P. Sørensen K. Steffens P. Steinhauser E. Stenlund D. Stüken M. L. Tincknell A. Twyhues G. R. Young 《Zeitschrift fur Physik C Particles and Fields》1992,53(2):225-237
Correlations between positive pions are investigated in the target fragmentation region of 200A GeV16O+nucleus collisions. The pions are measured with the Plastic Ball detector in the WA80 experiment at the CERN SPS. The target mass dependence of the radii and the correlation strength extracted by interferometry is studied. A new approach to the fit of the correlation function is introduced. The correlation strength and both invariant and transverse radii increase with decreasing target mass. The transverse radius for16O+C reactions appears to be much larger than the geometrical radius of the nuclei involved. For the Au target only a small fraction of the measured pions contributes to the apparent correlation. Hints for a much larger second component in16O+Au reactions are observed. Rescattering phenomena may provide a clue to understand these phenomena. 相似文献
74.
I. H. Bechtold M. P. De Santo J. J. Bonvent E. A. Oliveira R. Barberi Th. Rasing 《Liquid crystals》2003,30(5):591-598
The rubbing of polymer-coated substrates is one of the most frequently used techniques for liquid crystal alignment. However, the aligning mechanisms are not completely understood. The influence of friction charges induced by the rubbing process has been taken into account in theoretical publications. In this work we investigate the rubbing-induced charge domains of three polymers (PMMA, PI and PVA) with the electrostatic force microscopy technique, which allows the simultaneous determination of the surface topography and electrostatic potential. We observed a large intensity of the potential for the PMMA substrate, whereas no charge domains were observed for PVA. In addition, we followed the time evolution of the surface charge domains, and surprisingly after five days the charges were still present with a small reduction of intesity. Using polarizing optical microscopy we studied the influence of the charge domains on the LC aligning properties. 相似文献
75.
We give conditions under which a homomorphism between two Zariski dense subgroups of connected semisimple Lie groups G and G' without compact factors and with trivial center can be extended to a continuous isomorphism between G and G'. In particular we prove the marked length rigidity and the marked translation vector rigidity. This last result was motivated
by a Margulis‚s question.
Received: September 18, 2001 相似文献
76.
A most debated topic of the last years is whether simple statistical physics models can explain collective features of social dynamics. A necessary step in this line of endeavor is to find regularities in data referring to large-scale social phenomena, such as scaling and universality. We show that, in proportional elections, the distribution of the number of votes received by candidates is a universal scaling function, identical in different countries and years. This finding reveals the existence in the voting process of a general microscopic dynamics that does not depend on the historical, political, and/or economical context where voters operate. A simple dynamical model for the behavior of voters, similar to a branching process, reproduces the universal distribution. 相似文献
77.
Simone Zanella Dr. Michele Mingozzi Alberto Dal Corso Dr. Roberto Fanelli Dr. Daniela Arosio Prof. Dr. Marco Cosentino Dr. Laura Schembri Dr. Franca Marino Dr. Marta De Zotti Prof. Dr. Fernando Formaggio Dr. Luca Pignataro Prof. Dr. Laura Belvisi Prof. Dr. Umberto Piarulli Prof. Dr. Cesare Gennari 《ChemistryOpen》2015,4(5):633-641
A dual-action ligand targeting both integrin αVβ3 and vascular endothelial growth factor receptors (VEGFRs), was synthesized via conjugation of a cyclic peptidomimetic αVβ3 Arg-Gly-Asp (RGD) ligand with a decapentapeptide. The latter was obtained from a known VEGFR antagonist by acetylation at the Lys13 side chain. Functionalization of the precursor ligands was carried out in solution and in the solid phase, affording two fragments: an alkyne VEGFR ligand and the azide integrin αVβ3 ligand, which were conjugated by click chemistry. Circular dichroism studies confirmed that both the RGD and VEGFR ligand portions of the dual-action compound substantially adopt the biologically active conformation. In vitro binding assays on isolated integrin αVβ3 and VEGFR-1 showed that the dual-action conjugate retains a good level of affinity for both its target receptors, although with one order of magnitude (10/20 times) decrease in potency. The dual-action ligand strongly inhibited the VEGF-induced morphogenesis in Human Umbilical Vein Endothelial Cells (HUVECs). Remarkably, its efficiency in preventing the formation of new blood vessels was similar to that of the original individual ligands, despite the worse affinity towards integrin αVβ3 and VEGFR-1. 相似文献
78.
Ertuğrul Gazi Sağlam Sevcan Erden Özgür Tutsak Dilek Eskiköy Bayraktepe Zehra Yazan Durmuş Hakan Dal 《Phosphorus, sulfur, and silicon and the related elements》2017,192(3):322-329
Some 1,3-dithiadiphosphetane 2,4-disulfides (X2P2S4, X: Fc, FcLR; X: CH3O?C6H4?, LR) were allowed to react with alcohols to obtain dithiophosphonic acids (X(OR)PS2H). These were converted to the corresponding ammonium salts. The salts were of the structures [Fc(OR)PS2]?[NH4]+, R: 3-methyl-1-butyl- for I; 1-phenyl-1-propyl- for II; 3-pentyl- for III; 3-phenyl-1-propyl- for IV and [CH3O?C6H4(OR)PS2]?[NH4]+, R: 3-methyl-1-butyl- for V and 1-phenyl-1-propyl- for VI. To the best of our knowledge, all the compounds except V were prepared for the first time.The compounds synthesized were characterized by elemental analysis, NMR (1H, 13C, 31P), MS, FTIR, and Raman spectroscopies. Electrochemical behaviors of I–VI at disposable pencil graphite electrode (PGE) were investigated by using cyclic voltammetry (CV) and square-wave voltammetry (SWV). Adsorption and diffusion patterns of all the compounds on the PGE were also studied.Two electroactive groups were identified in the compounds I–IV and only one in V and VI. The ferrocenyl groups of I-IV were oxidized at around 0.4 V. The same compounds display a second, more intense CV band at 0.8 V. The corresponding band for the compounds V–VI appears at around 0.6 V with a much weaker intensity. It is suggested that the ferrocenyl group introduced into the structures stabilizes the radical species formed as the product of the oxidation of the dithiophosphonato group. 相似文献
79.
Kuwamura N Kitano K Hirotsu M Nishioka T Teki Y Santo R Ichimura A Hashimoto H Wright LJ Kinoshita I 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(38):10708-10715
Interchange between the nickel +2 and +3 oxidation states precisely controls the reversible rearrangement of the tris(2-pyridylthio)methanide (tptm) ligand in the organometallic nickel(II) complex [{Ni(μ-Br)-(tptm)}(2)] (2). Oxidation of 2 first gives the corresponding Ni(III) complex [{Ni(μ-Br)(tptm)}(2)][PF(6)](2) (4). However, in solution the tptm ligand in 4 slowly undergoes a rearrangement, in which the N and S atoms of one of the pyridylthiolate arms exchange Ni and C bonding partners, thereby resulting in an "N,S-confused" isomer of tptm in the product, [NiBr(bpttpm)]PF(6) (5; bpttpm= bis(2-pyridylthio)(2-thiopyridinium)-methyl). Reduction of 5 reverses this ligand rearrangement and 2 is reformed quantitatively. The individual steps involved in these unusual ligand rearrangements were investigated by a number of methods, including voltammetric analysis, and a mechanism for this process is proposed. X-ray crystal structure determinations of the key compounds 2, 4 and 5 have been obtained. 相似文献
80.
Di Santo G Blankenburg S Castellarin-Cudia C Fanetti M Borghetti P Sangaletti L Floreano L Verdini A Magnano E Bondino F Pignedoli CA Nguyen MT Gaspari R Passerone D Goldoni A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(51):14354-14359
Scratching the surface: Formation of a monolayer of 2H-tetraphenylporphyrins (2H-TPP) on Ag(111), either by sublimation of a multilayer in the range 525-600?K or by annealing (at the same temperature) a monolayer deposited at room temperature, induces a chemical modification of the molecules. Rotation of the phenyl rings into a flat conformation is observed and tentatively explained, by using DFT calculations, as a peculiar reaction due to molecular dehydrogenation. 相似文献