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201.
Dr. Russell W. Driver Prof. Timothy D. W. Claridge Prof. Steve Scheiner Prof. Martin D. Smith 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(46):16513-16521
The precise role of non‐conventional hydrogen bonds such as the C?H???O interaction in influencing the conformation of small molecules remains unresolved. Here we survey a series of β‐turn mimetics using X‐ray crystallography and NMR spectroscopy in conjunction with quantum calculation, and conclude that favourable torsional and electronic effects are important for the population of states with conformationally influential C?H???O interactions. Our results also highlight the challenge in attempting to deconvolute a myriad of interdependent noncovalent interactions in order to focus on the contribution of a single one. Within a small molecule that is designed to resemble the complexity of the environment within peptides and proteins, the interplay of different steric burdens, hydrogen‐acceptor/‐donor properties and rotational profiles illustrate why unambiguous conclusions based solely on NMR chemical shift data are extremely challenging to rationalize. 相似文献
202.
Cover Picture: Radiation Damage and Racemic Protein Crystallography Reveal the Unique Structure of the GASA/Snakin Protein Superfamily (Angew. Chem. Int. Ed. 28/2016) 下载免费PDF全文
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204.
A pentaammineazidocobalt(III) complex, [Co(NH3)5N3](MnO4)2XH2O has been synthesized by an one-pot synthesis method. It was characterized by studies such as infrared (IR) and UV-visible spectroscopy. The single crystal X-ray structure analysis revealed that the title complex crystallizes in space group Cc. The cobalt center is six coordinated with slightly octahedral geometry. The supramolecular architecture is also formed by intermolecular N-H…O (anion and H2O) and Mn-O…O-H hydrogen bonds. The binding property of the cation, [Co(NH3)5N3]2+ with the anion, MnO4– has also been determined (in solution phase) with the help of UV-visible spectroscopic titrations. Further, the genotoxic effects of KMnO4, [Co(NH3)5N3]Cl2 and [Co(NH3)5N3](MnO4)2XH2O were studied using Allium cepa root chromosomal aberration assay and it revealed that the genotoxicity of the newly synthesized complex is 1.97–1.76 fold, which is less compared to KMnO4. The order of genotoxic potential has been observed to be KMnO4 > [Co(NH3)5N3](MnO4)2XH2O > [Co(NH3)5N3]Cl2. 相似文献
205.
Thomas M. Klapötke Burkhard Krumm Dieter Naumann 《Journal of fluorine chemistry》2004,125(6):997-1005
The perfluoroaryl tellurolates C6F5TeLi (1) and 4-CF3C6F4TeLi (2) were prepared. These intermediates were identified by NMR spectroscopy and may form, depending on the reaction conditions, either the corresponding ditellanes C6F5TeTeC6F5 (3) and CF3C6F4TeTeC6F4CF3 (4) by subsequent oxidation, or in the case of 1, a telluranthrene (C6F4Te)2 (5) by reaction with itself. The halogenation products of 5, ( C6F4Te)2F4 (6), (C6F4Te)2Cl4 (7), (C6F4Te)2Br4 (8), as well as the azidation product (C6F4Te)2(N3)4 (9) were synthesized. Furthermore, in pursuit of our recent work on tellurium azides, the syntheses and properties of R2Te(N3)2 (R=CF3 (10), C6F2H3 (11)) and RTe(N3)3 (R=CF3 (12) and C6F5 (13)) are reported. The crystal structures of CF3C6F4TeTeC6F4CF3 (4), (C6F4Te)2Br4 (8), and (C6F2H3)2Te(N3)2 (11) were determined. 相似文献
206.
Jonathon E. Beves Edwin C. Constable Catherine E. Housecroft Markus Neuburger Silvia Schaffner Jennifer A. Zampese 《Helvetica chimica acta》2009,92(11):2214-2226
The syntheses of the five 2,2′: 6′,2″‐terpyridine (tpy) ligands 5 – 9 functionalized in the 4′‐position with a hydrazone substituent RR′C?N? NH (R=R′=Me; R=H, R′=4‐BrC6H4, 4‐O2NC6H4, 4‐MeOC6H4, or 3,5‐(MeO)2C6H3) are described. Protonation of the tpy domain of the ligands is facile. Solution behaviour has been studied by NMR and electronic spectroscopies. Representative structural data are presented for neutral and monoprotonated ligands, and illustrate that H‐bonding involving the formal amine NH unit is a dominant structural motif in all cases. 相似文献
207.
8,9,12-Trihydro-9,9-pentamethylene-12-(3-nitrophenyl)-11H-naphtho[1′,25,6] pyrano[2,3-d]pyrimidin-11(10H)-one 1, another conversion product of Friedl(a)ndler reaction, has been synthesized by the reaction of 2-amino-4-(3-nitrophenyl)-4H benzo[f]chromene-3-carbo- nitrile 2 with cyclohexanone in the presence of Lewis acid catalysts. The crystal of the title compound 1 THF solvate, C60H62N6O10, was obtained and determined by X-ray diffraction me- thod. The crystal is of triclinic, space group P with a = 11.4633(11), b = 12.6247(12), c = 19.658(2)(A), α = 72.642(8), β = 89.045(9), γ = 68.340(5)°, V = 2509.6(4), Z = 2, Dc = 1.359 g/cm3, F(000) = 1088, Mr = 1027.16, the final R = 0.0674 and wR = 0.1869 with I > 2σ(I) and the goodness-of-fit S = 1.045 on F2. The pyrimidine ring has an envelope conformation, linked with a six-membered ring through a spiro C atom. The crystal packing of 1 THF solvate is stabilized by N-H…O hydrogen bonds, and π-π stacking interaction occurs between two adjacent nearly planar molecules of 1. 相似文献
208.
209.
ZeMin Zhang FuSheng Guo PengHu Guo JunLiang Liu ZhaoPing Ni MingLiang Tong 《中国科学:化学(英文版)》2012,55(6):934-941
Four 3d-4f heterometallic complexes, [CuⅡ LnⅢ (bpt) 2 (NO 3 ) 3 (MeOH)] (Ln = Gd, 1; Dy, 2; bptH = 3,5-bis(pyrid-2-yl)-1,2,4- triazole), [CuⅡ 2 LnⅢ 2 (μ-OH) 2 (bpt) 4 Cl 4 (H 2 O) 2 ]·6H 2 O (Ln = Gd, 3; Dy, 4), have been synthesized under solvothermal conditions. X-ray structural analyses reveal that 1 and 2 are isostructural while 3 and 4 are isostructural. In each complex, the copper and gadolinium or dysprosium ions are linked by two triazolate bridges and form a CuⅡ -LnⅢ dinuclear unit. The intramolecular Cu-Ln distances are 4.542, 4.525, 4.545 and 4.538 for 1, 2, 3 and 4, respectively. Two dinuclear CuLn units are bridged by two OH- groups into the zig-zag tetranuclear {CuⅡ 2 LnⅢ 2 } structures with the Ln(Ⅲ) Ln(Ⅲ) distances of 3.742 and 3.684 for 3 and 4, respectively. Magnetic studies show that the antiferromagnetic CuⅡ-LnⅢ interactions occur in 1 (J CuGd = 0.21 cm-1 ) and 2. The antiferromagnetic interaction occurs in complex 3 with J CuGd = 0.82 cm-1 and J GdGd = 0.065 cm-1 , while dominant ferromagnetic interaction occurs in complex 4. 相似文献
210.
α‐Peptide–Oligourea Chimeras: Stabilization of Short α‐Helices by Non‐Peptide Helical Foldamers 下载免费PDF全文
Dr. Juliette Fremaux Laura Mauran Dr. Karolina Pulka‐Ziach Dr. Brice Kauffmann Dr. Benoit Odaert Dr. Gilles Guichard 《Angewandte Chemie (International ed. in English)》2015,54(34):9816-9820
Short α‐peptides with less than 10 residues generally display a low propensity to nucleate stable helical conformations. While various strategies to stabilize peptide helices have been previously reported, the ability of non‐peptide helical foldamers to stabilize α‐helices when fused to short α‐peptide segments has not been investigated. Towards this end, structural investigations into a series of chimeric oligomers obtained by joining aliphatic oligoureas to the C‐ or N‐termini of α‐peptides are described. All chimeras were found to be fully helical, with as few as 2 (or 3) urea units sufficient to propagate an α‐helical conformation in the fused peptide segment. The remarkable compatibility of α‐peptides with oligoureas described here, along with the simplicity of the approach, highlights the potential of interfacing natural and non‐peptide backbones as a means to further control the behavior of α‐peptides. 相似文献