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51.
Rozniecki JJ Dimitriadou V Lambracht-Hall M Pang X Theoharides TC 《Brain research》1999,840(1-2):1-15
The effects of changes in temperature on primary and secondary endings of isolated cat muscle spindles were investigated under ramp-and-hold stretches and different degrees of pre-stretch. Temperature-induced alterations of the discharge frequency were compared over a temperature range of 25–35°C. Both primary and secondary endings responded to warming with increasing discharge frequencies when the spindle was pre-stretched by 5–10% of its in situ length. The following differences between the temperature effects on primary and secondary endings were observed: (1) The temperature coefficients (Q10) obtained from the discharge frequencies during the dynamic and static phase of a stretch were similar for endings of the same type, but they were larger in primary endings (range of Q10: 2.3–3.3; mean: 2.9) than in secondary endings (range of Q10: 1.6–2.2; mean: 2.0); (2) With primary endings, but not with secondary endings, the temperature sensitivity (imp s−1 °C−1) was larger during the dynamic phase than during the static phase of a stretch; (3) In primary endings, the fast and slow adaptive components occurring in the discharge frequency during the static phase of a stretch clearly increased with warming while in secondary endings, the slow decay was less affected, and the fast decay showed no change; (4) In relaxed spindles, the excitatory effect of warming was overlaid by a strong inhibitory effect as soon as the temperature exceeded about 30°C, resulting in an abrupt cessation of the background activity in most secondary endings, but not usually in primary endings. In general, warming induced an enhanced stretch sensitivity in both types of ending, and additionally an inhibitory effect that is obvious only in secondary endings of relaxed spindles. The different effects of temperature on the discharge frequency of primary and secondary afferents are assumed to be caused by different properties of their sensory membranes. 相似文献
52.
The location of amino acids in soluble or membrane proteins is related to the hydrophobicity of the side chains. Amino acid hydrophobicity values are based upon the thermodynamics of transfer from an aqueous to a nonaqueous environment. However, for certain hydrophilic residues uncertainty exists on the appropriate hydrophobicity values. We have measured the octanol- water partition coefficients (P
o/w) of tripeptides of the sequence N-14-C-acetyl-Ala-JT-Ala-NH-tButyl (AcAlaXAlaNHtButyl), where the central residue X was either Gly , Ala, Phe, Trp, Pro, His, Asp, or Glu. The P
o/w for the tripeptides agreed reasonably well with values calculated by the fragment method of D. J. Abraham and A. J. Leo (Proteins Struct. Func. Gen. 2, 130–152, 1987). The log P
o/w of the uncharged form was 1.6,2.7, and 2.5 greater than the log P
o/w of the ionized form for the His, Asp, and Glu peptide, respectively. The new data on the pH dependence of the ionizable side chains, His, Asp, and Glu, should result in better prediction of the partition coefficient of peptides as a function of pH. The thermodynamic parameters were determined from the temperature dependence of partitioning. In the temperature range studied (2 to 65°C) the transfer of tripeptides from water to octanol was entropy governed except for the ionized peptides. A heat capacity term was necessary to account for the transfer of tripeptides containing non polar residues. The heat capacity change for transfer from water into octanol was –45, –73, –81, and –88 cal/mol K for Ala, Phe, Trp, and Pro peptides, respectively. Peptides containing Gly, His (pH 7.2), and the uncharged forms of Asp, Glu, and His did not show a significant change in heat capacity. The side-chain contribution of the central residue X (G
X) to the free energy of transfer was obtained from the difference between the free energy o f transfer of the peptide containing the central residue X and the Gly peptide; G
X = G
(AcAlaGlyAlaNHtButyl) - G (AcAlaGlyAlaNHtButyl). The relative order of hydrophobicity of the side chains correlated well with previous studies. However, a significant difference was found for the absolute hydrophobicity between the present study and experimental data on N-acetyl amino acid amide derivatives (J. Fauchere and V. Pliska, Eur. J. Med. Chem. 18(4), 369–375, 1983). The G
X values at pH 7.2 were 0, –0.13, –2.19, –2.52,–0.29, –0.16, 3.50, and 3.12 kcal/mol for Gly, Ala, Phe, Trp, Pro, His, Asp, and Glu, respectively. These hydrophobicity values in a tripeptide environment provide suggested values for a hydrophobicity scale. 相似文献
53.
目的了解大学生社交焦虑和班集体人际关系现状,为高校心理健康保健提供确实的依据。方法对重庆市3所大学共5个班进行交往焦虑量表和大学班级集体人际关系问卷调查。结果农村大学生的社交焦虑高于城镇大学生;男生的负向人缘系数高于女生;非独生子女大学生的负向人缘系数高于独生子女大学生;大学生社交焦虑与负向人缘系数呈显著负相关,大学生的自我认知和自我体验与实际的人际关系并不完全一致。结论大学生社交焦虑与负向人缘系数呈显著负相关。 相似文献
54.
提出一种利用相关性和RR间期比相结合的快速室性早搏的检测算法.该算法具有一定的病人自适应性.通过MIT-BIH心律失常数据库的验证,该方法对Normal和PVC有很高的识别率. 相似文献
55.
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In contrast to other reliability estimates, test-retest reliability (or reproducibility) captures not only the measurement error of an assessment instrument, but also the stability of the construct measured. Consequently, one would expect any departure from identity (Y = X) of measurement pairs (X first, and Y second measurement) to be treated as 'error' by the respective reproducibility statistic, even if 'true' changes happened, e.g. worsening of a disease due to its natural course. The Pearson correlation, still often advocated for continuous measures in test-retest reliability studies, however captures the degree of linearity (Y = bX + a): perfect relationship can be computed, even if the measurement pairs differ not only by a additive constant 'a', but also because of a multiplication of the X-values with the slope 'b'. Therefore, intraclass correlation coefficients (ICCs) have been proposed as alternative statistics for reproducibility. However, only ICCs with absolute agreement definition of concordance capture the degree of identity. ICCs with a consistency definition of concordance measure the degree of additivity (Y = X + a). ICCs are calculated from repeated measures analyses of variance (ANOVAs), and a common population variance must be is assumed for the different measurements. Given this assumption, an ICC computed from a one-way ANOVA seems to be the best choice for this purpose. Otherwise, Lin's concordance correlation coefficient is recommended as identity measure. 相似文献
57.
综合评价中指标权重系数确定方法探讨 总被引:23,自引:0,他引:23
目的探讨加权关联度分析在综合评价中指标权重系数的确定方法。方法应用6种计算指标权重系数的方法:经验性权数法、因子分析权数法、信息量权数法、独立性权数法、秩和比(RSR)权数法和层次分析权数法。结果得出6种权数法计算的指标权重系数值,经对比、稳定性检验和合理性分析,在6种权数方法中,因子分析权数法和层次分析权数法求得的权数评价结果具有稳定性、合理性,符合客观实际。结论6种权数法,从不同侧面反映了各评价指标相对重要性权数,其中,因子分析权数和层次分析权数是一种稳定、合理的权数,为加权关联度分析综合评价奠定了基础。 相似文献
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60.
Rohan S. Virgincar Zackary I. Cleveland S. Sivaram Kaushik Matthew S. Freeman John Nouls Gary P. Cofer Santiago Martinez‐Jimenez Mu He Monica Kraft Jan Wolber H. Page McAdams Bastiaan Driehuys 《NMR in biomedicine》2013,26(4):424-435
In this study, hyperpolarized 129Xe MR ventilation and 1H anatomical images were obtained from three subject groups: young healthy volunteers (HVs), subjects with chronic obstructive pulmonary disease (COPD) and age‐matched controls (AMCs). Ventilation images were quantified by two methods: an expert reader‐based ventilation defect score percentage (VDS%) and a semi‐automated segmentation‐based ventilation defect percentage (VDP). Reader‐based values were assigned by two experienced radiologists and resolved by consensus. In the semi‐automated analysis, 1H anatomical images and 129Xe ventilation images were both segmented following registration to obtain the thoracic cavity volume and ventilated volume, respectively, which were then expressed as a ratio to obtain the VDP. Ventilation images were also characterized by generating signal intensity histograms from voxels within the thoracic cavity volume, and heterogeneity was analyzed using the coefficient of variation (CV). The reader‐based VDS% correlated strongly with the semi‐automatically generated VDP (r = 0.97, p < 0.0001) and with CV (r = 0.82, p < 0.0001). Both 129Xe ventilation defect scoring metrics readily separated the three groups from one another and correlated significantly with the forced expiratory volume in 1 s (FEV1) (VDS%: r = –0.78, p = 0.0002; VDP: r = –0.79, p = 0.0003; CV: r = –0.66, p = 0.0059) and other pulmonary function tests. In the healthy subject groups (HVs and AMCs), the prevalence of ventilation defects also increased with age (VDS%: r = 0.61, p = 0.0002; VDP: r = 0.63, p = 0.0002). Moreover, ventilation histograms and their associated CVs distinguished between subjects with COPD with similar ventilation defect scores, but visibly different ventilation patterns. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献