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1.
《Dental materials》2022,38(4):e69-e82
Objectivestesting if hypothetical transverse centripetal strains due to polymerization contraction of luting materials produce differential alterations in its bonding to luted structures, depending on distances to the center of the luting mass, and if this effect is C-factor related. Two hypotheses were tested: (1) there is a statistically significant decreasing relationship between the bonding strength and the transverse distances to the center of the luting material, and (2) there is a statistically significant difference between bonding strengths among luting spaces with different configuration factors.Methods10 PMMA (15 mm Ø) pairs of cylinders were cemented (Scotchbond Universal adhesive & Relyx Universal, both chemically cured) in a compliant setup under two (20 and 70 N) luting forces forming 2 groups (5 samples each), resulting in different C-factors. Whole samples were sectioned in x and y directions obtaining non-trimmed beams from all along the luting surfaces. Their relative positions in each sample were assessed before separating and categorized (10 categories) according to their distances to the center of the sample. All beams were tested in tension and, because of their uneven bonding areas and to balance its influence, UTS results were transformed into UTSres. First hypothesis was tested trough a linear relationship between UTSres and distances to vertical centers per samples. Second hypothesis was tested using Mann-Whitney U tests to compare UTSres between groups, along all categories. Further Weibull analysis was applied.ResultsANOVA’s p of the regression UTSres – categories were statistically significant for all samples in group 70 N and for all except one in group 20 N: first hypothesis is partially maintained. Although Mann-Whitney tests p comparing UTSres of both groups for all categories but the first were statistically significant this hypothesis was maintained relying in Weibull analysis. Significance: bonded attachment of cemented materials decreases from centers to outbounds in plane, extensive surfaces, and this decrease is C-factor related.  相似文献   
2.
目的研究不同存储条件下6种通用型粘接剂及喷砂条件对聚醚醚酮(PEEK)与复合树脂之间粘接强度和耐久性的影响。 方法将PEEK材料切割成12个边长为2 cm的正方体试件。对其中6个试件进行氧化铝喷砂处理。6种通用型粘接剂为:Tetric N-Bond Universal(TNU)、Single Bond Universal(SBU)、DX.BOND UNI(DXB)、Selective Etch Bond(SEB)、Gluma Bond Universal(GBU)、Prime & Bond Universal(PBU)。实验分为7组,每组包含4个喷砂面和4个未喷砂面。7种表面处理方法分别为:不使用粘接剂(对照组)和6种通用型粘接剂(实验组:TNU组、SBU组、DXB组、SEB组、GBU组、PBU组)。经表面处理后,将流动复合树脂F00注入透明模具并将其无压力置于试件表面后进行光照固化。试件分别在37 ℃恒温水浴24 h或冷热循环3000次后进行剪切粘接强度测试。使用松风EyeSpecial C-Ⅳ口腔专用相机微距模式进行断面拍照并进行断裂模式分析。采用SPSS 23.0软件Three-Way ANOVA(冷热循环、粘接剂与喷砂)与Tukey方法对各组数据进行统计分析(α = 0.05)。 结果24 h水浴条件下,TNU组分别获得不喷砂组(9.92 ± 1.19)MPa与喷砂组(9.97 ± 1.03)MPa最高粘接强度;冷热循环3000次后PBU组分别获得不喷砂组(6.75 ± 0.99)MPa与喷砂组(7.22 ± 1.30)MPa最高粘接强度。三因素分析结果显示:冷热循环(F = 3 045.429,P<0.001)、粘接剂(F = 361.165,P<0.001)与喷砂(F = 80.050,P<0.001)可显著影响粘接强度;冷热循环与粘接剂(F = 155.724,P<0.001)、粘接剂与喷砂(F = 3.535,P = 0.002)、冷热循环与喷砂(F = 9.184,P = 0.003)两两因素间分别具有交互作用;冷热循环、粘接剂与喷砂三因素间具有交互作用(F = 12.392,P<0.001)。 结论(1)喷砂有助于改善通用型粘接剂对复合树脂与PEEK 37 ℃恒温水浴24 h粘接强度;(2)复合树脂与PEEK粘接强度在冷热循环3000次后显著降低;(3)本实验中PBU组粘接耐久性优于其他粘接系统。  相似文献   
3.
4.
随着科技的高速发展,基于核物理的诊断技术和放疗技术在医学中得到广泛应用,但同时也会给人体造成不同程度的损伤。因此,研究和开发能够预防以及治疗辐射损伤的药物意义重大。综述抗辐射天然产物如多糖、黄酮、酚酸、皂苷等的研究进展,并对其研究前景进行展望,为其进一步开发提供参考。  相似文献   
5.
目的:对采用响应面法优化九节中总黄酮的提取工艺后以大孔树脂富集的工艺进行评价。方法:在单因素实验基础上,以九节总黄酮提取率作为响应值,以乙醇浓度、提取温度、料液比和提取时间为自变量,采用Box-Behnken响应面法,根据其中心组合的实验原理优化工艺条件,再以吸附、解吸及回收效果等为指标筛选最优的大孔树脂,对总黄酮进一步富集。结果:最优提取工艺为:提取温度59 ℃,乙醇浓度75%,料液比1:10,提取时间48 min,提取次数为2次,在此条件下浸膏得率25.60%,总黄酮得率为2.36%,HP-20型树脂对九节总黄酮有较好的富集效果,富集后总黄酮回收率达到87.70%,纯度相比浸膏提升6倍。结论:该工艺简单且稳定性好,对于九节作为药品资源的开发利用具有重要的参考价值。  相似文献   
6.
无花果果实中化学成分研究   总被引:1,自引:0,他引:1  
邵明辉  张文浩  张明明  刘艳萍  赵烽  付艳辉 《中草药》2019,50(11):2524-2528
目的研究桑科榕属植物无花果Ficus carica果实的化学成分。方法综合运用硅胶柱色谱、ODS柱色谱、Sephadex LH-20凝胶柱色谱以及制备型高效液相色谱等技术进行系统分离,根据化合物的理化性质及波谱数据鉴定化合物的化学结构。结果从无花果果实的90%乙醇提取物中分离得到了16个化合物,分别鉴定为怀特酮(1)、甘草宁G(2)、4′-羟基-5,7-二甲氧基-6-(3-甲基-丁烯基)-异黄酮(3)、猫尾草异黄酮(4)、indicanine C(5)、木豆素(6)、美迪紫檀素(7)、高丽槐素(8)、4-羟基-3-甲氧基-8,9-亚甲二氧基紫檀烷(9)、3-羟基-9,10-二甲氧基紫檀烷(10)、松脂素(11)、杜仲树脂酚(12)、丁香树脂醇(13)、8-羟基松脂醇(14)、3-羟基-1-(4-羟基-3-甲氧基苯)-1-丙酮(15)和4-羟基-3-甲氧基苯乙醇(16)。结论所有化合物均为首次从无花果中分离得到。  相似文献   
7.
The aim of the present study was to compare the restorative time for filling cavities in posterior teeth using bulk‐fill and conventional resin composites through a systematic review and meta‐analysis. A search for clinical trials and laboratory studies was performed in PubMed/MEDLINE, Scopus, the Latin American and Caribbean Health Sciences Literature database, the Brazilian Library in Dentistry, Cochrane Library, Clinical Trials, and ReBEC (Registro Brasileiro de Ensaios Clínicos) databases without publication year or language restriction. Two reviewers identified eligible studies according to the inclusion criteria: bulk‐fill compared to conventional resin in class I or II, and the restorative time as an outcome. A meta‐analysis of the restorative time mean difference between composites was performed (inverse variance method, random effects model; Z‐test, P ≤ .05). From the 662 eligible studies, 133 were selected for full‐text analysis; three were included in the systematic review and in the meta‐analysis. Overall, the restorative time was lower when bulk‐fill was used (P = .0007, Z = 3.37), as the subgroup full‐body bulk‐fill (P < .00001, Z = 21.00). There was no difference in restorative time between flowable bulk‐fill and conventional resins (P = .08, Z = 1.76). Moderate‐to‐substantial heterogeneity was detected. Full‐body bulk‐fill composites decrease the restorative time in posterior teeth compared to conventional resins. Full‐body bulk‐fill resins require a shorter restorative time to perform restorations in posterior teeth than conventional resins, but the same is not valid for flowable bulk‐fill resin composites.  相似文献   
8.
目的:研究喷砂和微弧氧化两种金属表面处理方式及树脂粘结剂对钛合金与硬质复合树脂粘结强度和耐久性的影响。方法:应用CAD/CAM技术切削出80个底面直径10 mm、高8 mm的圆柱形钛合金试件。根据表面处理方式分为两组:喷砂组(sandblasting,SB)试件表面进行Al2O3 颗粒喷砂,微弧氧化组(microarc-oxidation,MAO)试件表面处理后形成疏松多孔的陶瓷膜结构。每组内根据是否应用树脂粘结剂分为SB-resin luting-N组(不使用)、SB-resin luting-Y组(使用)、MAO-resin luting-N组(不使用)、MAO-resin luting-Y组(使用)4个亚组。试件与Cemerage硬质复合树脂粘结固化,每组的各一半测试冷热循环0次和5 000次后的粘结强度,对比分析测试结果。扫描电镜观察粘结强度试验前后钛合金试件表面形貌。结果:喷砂联合树脂粘结剂组冷热循环0次后,钛合金与硬质复合树脂的粘结强度最高(16.2±1.8) MPa;微弧氧化未联合树脂粘结剂组冷热循环5 000次后,两者的粘结强度最低(8.9±1.5) MPa,喷砂和微弧氧化未联合树脂粘结剂组冷热循环5 000次后粘结强度分别为(10.7±2.2) MPa和(8.9±1.5) MPa,相比循环0次组降低,差异有统计学意义(P=0.000和P=0.001);喷砂和微弧氧化处理联合树脂粘结剂5 000次冷热循环后粘结强度分别为(15.5±2.1) MPa和(11.7±1.3) MPa,相比循环0次组降低,但差异无统计学意义(P=0.087和P=0.234)。结论:喷砂和微弧氧化两种表面处理方式联合树脂粘结剂均可提高钛合金与硬质复合树脂的粘结强度和耐久性,以喷砂组提高更为显著;目前受微弧氧化技术参数的限制,喷砂效果优于微弧氧化。  相似文献   
9.

Purpose

The aim of this study was to determine the mechanical properties of computer-aided design/computer-aided manufacturing (CAD/CAM) resin composites for dental restoration assuming perfect silane coupling by in silico homogenization analysis using a three-dimensional model constructed from cryo-electron microscopy (cryo-EM) images.

Methods

Three-dimensional dataset of a commercial CAD/CAM resin composite block (RCB) was obtained using EM with cryo-stage and focused ion beam at ?130 °C. The region of inspection was 1.8 μm × 1.4 μm × 1.2 μm, and 213 slices were obtained from this region. Each slice was processed (noise reduction, threshold setting, and segmentation) using image processing software to design an in silico model. From the processed image slices, a bulk three-dimensional object and stereolithography model were reconstructed using voxel modeling software. To evaluate the elastic modulus and Poisson’s ratio of the CAD/CAM RCB, homogenization analysis was performed.

Results

The generated voxel model included 37,276,216 voxels, 42,472,040 patches of the surface, 2,123,672 nodes, a volume of 165,748,899, and a surface area of 175,206,723. The mean of the elastic moduli along each axis was 10.71 ± 1.79 GPa. The mean of the Poisson’s ratios of each plane was 0.23 ± 0.02.

Conclusions

A CAD/CAM resin composite model was successfully reconstructed from cryo-EM images, suggesting that the established image processing method is useful for producing dental restorative materials containing nano-fillers and for predicting homogenized mechanical properties. The homogenized mechanical properties indicated that the mechanical properties of the CAD/CAM RCB assumed perfect silane coupling between the fillers and resin matrix.  相似文献   
10.
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