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11.
T Wave Complexity in Patients with Hypertrophic Cardiomyopathy 总被引:2,自引:0,他引:2
GANG YI KRISHNA PRASAD PERRY ELLIOTT SANJAY SHARMA XIAOHUA GUO WILLIAM J. MCKENNA MAREK MALIK 《Pacing and clinical electrophysiology : PACE》1998,21(11):2382-2386
The complexity of the T wave assessed by principal component analysis (PCA) has been proposed to reflect obnormal repolarization, which may be arrhythmogenic. To determine whether PCA can differentiate patients with hypertrophic cardiomyopathy (HCM) from normal subfects and whether PCA is of prognostic importance in HCM, 112 patients with HCM (41 ±14 years, 64 males) and 72 healthy subjects (39 ± 9 years, 41 males) were studied. Patients with sinus node dysfunction, AV conduction block, flat T waves, QRS > 140 ms, and those < 15 years were excluded from this study. Standard 12-lead ECGs were recorded digitally using the MAC-VU system (Marquette Medical Systems). PCA parameters were computed using the QT Guard software package by Marquette. PCA ratio was significantly greater in HCM patients than in normal controls (23.9%± 12.4% vs 16.1%± 7.6%, P < 0.0001) and was correlated with QT-end dispersion (r = 0.24. P = 0.01) and QT peak (Q point to T peak) dispersion (r = 0.35, P < 0.0001). HCM patients with syncope (n = 23) had increased PCA ratios compared with those without syncope (29.1%± 11.5% vs 22.5%± 12.3%, P = 0.01). PCA ratio was similar in patients with and without nonsustained ventricular tachycardia on Holter (25.9%± 11.4% vs 22.7%± 12.1%, P = 0.2), as well as in patients treated with amiodarone or sotalol versus those not on therapy. In conclusion, assessment of the complexity of the T wave by PCA differentiates HCM patients from normal subjects. PCA ratio correlated with QT dispersion and an increased PCA ratio was associated with a history of syncope in HCM. 相似文献
12.
SUDHANAND PRASAD R. BALAJI RAO HAKAN BERGSTRAND BRITTA LUNDQUIST ELMER L. BECKER P. BALARAM 《Chemical biology & drug design》1996,48(4):312-318
Five stereochemically constrained analogs of the chemotactic tripeptide incorporating l-aminocycloalkane-l-carboxylic acid (Acnc) and α, α-dialkylglycines (Deg, diethylglycine; Dpg, N, N-dipropylglycine and Dbg, N, N-dibutylglycine) at position 2 have been synthesized. NMR studies of peptides For-Met-Xxx-Phe-OMe (Xxx = Ac7c. I: Ac8c. II: Deg, III; Dpg, IV and Dbg, V; For, formyl) establish that peptides with cycloalkyl residues, I and II, adopt folded β-turn conformations in CDCl3, and (CD3)2SO. In contrast, analogs with linear alkyl sidechains, III-V, favour fully extended (C5) conformations in solution. Peptides I-V exhibit high activity in inducing β-glucosaminidase release from rabbit neutrophils, with ED50 values ranging from 1.4–8.0 × 10–11. M. In human neutrophils the Dxg peptides III-V have ED50 values ranging from 2.3 × 10?8 to 5.9 × 10?10 M, with the activity order being V>IV>III. While peptides I-IV are less active than the parent. For-Met-Leu-Phe-OH, in stimulating histamine release from human basophils, the Dbg peptide V is appreciably more potent, suggesting its potential utility as a probe for formyl peptide receptors. © Munksgaard 1996. 相似文献
13.
ISABELLA L. KARLE R. GURUNATH SUDHANAND PRASAD R. BALAJI RAO P. BALARAM 《Chemical biology & drug design》1996,47(5):376-382
Two crystal structures of a nonapeptide (anhydrous and hydrated) containing the amino acid residue α,α-di-n-butylglycyl, reveal a mixed 310-α-helical conformation. Residues 1-7 adopt φ, ψ values in the helical region, with Val(8) being appreciably distorted. The Dbg residue has φ, ψ values of -40, -37° and -46, -407° in the two crystals with the two butyl side chains mostly extended in each. Peptide molecules in the crystals pack into helical columns. The crystal parameters are: C50 H91 N9 O12, space group P21, with a= 9.789(1)Å;, b= 20.240(2) Å. c= 15.998(3) Å. β= 103.97(1): Z= 2, R=10.3% for 1945 data observed < 3σ(F) and C50H91N9O12· 3H2O, space group P21 with a= 9.747(3)Å, b= 21.002(8) Å, c= 15.885(6) Å, β= 102.22(3). Z= 2. R=13.6% for 2535 data observed < 3σ(F) The observation of a helical conformation at Dbg suggests that the higher homologs in the α,α-dialkylated glycine series also have a tendency to stabilize peptide helices. © Munksgaard 1996. 相似文献
14.
L-Histidine acetate crystallizes in two forms: (I) orthorhombic; P212121; a= 5.027, b= 11.126, c= 17.473 Å; Z = 4; (II) monoclinic; C2; a= 15.649, b= 9.276, c= 8.566 Å; β= 94.65°; Z = 4. The structures were solved by direct methods and refined to R-values of 0.056 and 0.089 for 1131 and 1330 observed reflections, respectively. The conformations of the histidine molecule in the two forms are different. However, both are such that they facilitate the occurrence of a specific interaction of the histidine molecule with a carboxylate group. The basic elements of aggregation are hydrogen-bonded histidine ribbons, but they are of different types in the two structures. The ribbons are interconnected by acetate ions to form the crystals. The structures contain two characteristic interaction patterns involving amino and carboxylate groups, one of which is observed for the first time. The two water molecules in form II and their symmetry equivalents form an uninterrupted hydrogen-bonded chain running through the crystal. They also present an interesting case of disorder in hydrogen bonds. A comparative study involving amino acid complexes of acetic acid shows that the presence of acetate ion could lead to new aggregation patterns, specific interactions and characteristic interaction patterns with varying degrees of similarity with those observed in other structures containing amino acids. 相似文献
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