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41.
Objectives
To analyze the influence of cavity geometry and lining materials in MOD composite restorations by characterizing the polymerization shrinkage and cusp deflection.Methods
Eighty intact molars with similar sizes were collected and randomly divided into eight groups. MOD cavities with various widths and depths were prepared on these teeth: Group I, 2(W) × 2(D) mm; Group II, 4(W) × 2(D) mm; Groups III, IIIf, IIIg, 2(W) × 4(D) mm; and Groups IV, IVf, IVg, 4(W) × 4(D) mm. In Groups IIIf and IVf, flowable composite liner was placed prior to composite restoration, while glass-ionomer liner was used in Groups IIIg and IVg. Deformations of restorations resulted from composite shrinkage were recorded for 30 min following light irradiation using a digital-image-correlation (DIC) method to subpixel level. The displacements at the boundaries of the restorations were analyzed using one-way ANOVA and the post hoc test at a 5% significance level. The correlation between the geometric factors and the displacements was also analyzed.Results
The inward displacements on free surfaces were greater than those on the bonded surfaces. Groups with flowable composite linings showed greater amount of displacements on free and bonded surfaces compared to the unlined and glass ionomer lining groups. The correlation analysis showed that the free surface shrinkage was related with the cavity width and C-factor, while cusp deflections were correlated with the cavity depth and the cusp compliance.Significance
The DIC technique measures composite shrinkage on different boundaries of restorations to facilitate the investigation of polymerization kinetics. Using flowable composite lining and increased cusp depth may aggravate the cusp flexure. 相似文献42.
STATEMENT OF PROBLEM: Because conventional glass ionomer cements are moisture sensitive, a surface coating is recommended during the initial setting stage. It is unknown whether resin-modified glass ionomer cements also need surface protection. PURPOSE: This study investigated the effect of various surface protections on microleakage with Class V resin-modified glass ionomer restorations. MATERIAL AND METHODS: Forty extracted molars with buccal and lingual Class V cavity preparations were restored with a resin-modified glass ionomer (Fuji II LC). The occlusal margin of each restoration was on enamel and the cervical margin on dentin. After immediate finishing and polishing, the teeth were divided into 4 groups according to the following surface protection treatments: group I, unprotected; group II, Fuji varnish; group III, resin adhesive; and group IV, acid etching and resin adhesive. After these procedures, all teeth were stored in isotonic saline for 24 hours, thermocycled 1500 times at 5 degrees C to 60 degrees C, and soaked in dye solution for 24 hours. The teeth then were longitudinally sectioned and observed under a stereomicroscope. The degree of dye penetration was recorded and analyzed with the Kruskal-Wallis and Mann-Whitney tests (P<.05) RESULTS: None of the 4 groups demonstrated complete margin sealing at either the occlusal or cervical margins. Groups II and III displayed the least microleakage at cervical margins; a significant difference existed between groups I and III (P=.034). Compared with the other 3 groups, group IV showed significantly greater microleakage at the cervical margins. CONCLUSION: Although resin-modified glass ionomers can be finished immediately, they remain moisture sensitive. Within the limitations of this study, the results suggest that resin adhesive should be used as a surface protection to reduce margin microleakage of resin-modified glass ionomer restorations. 相似文献
43.
OBJECTIVE: To investigate the cancer-promoting effect of Taiwan betel quid in hamster buccal pouch carcinogenesis.
MATERIALS AND METHODS: Two hundred and fifty-two non-inbred mate adult Syrian golden hamsters were randomly divided into six groups, each containing forty-two animalS. A treatment regimen over a 14-week experimental period was employed with six animals per group being killed at seven different periods (every 2 weeks). The right buccal pouch of each animal was painted three times a week with various combinations of 7, 12-dimethylbenz[a]anthracene (DMBA), Taiwan betel quid extract, dimethyl sulfoxide (DMSO) and mineral oil.
RESULT: Both the number and size of tumors in animals concurrently treated with DMBA and betel quid were significantly higher than those in animals treated with DMBA alone in each killing period of 8, 10, 12 and 14 weekS. No visible tumors but hyperkeratosis and acanthosis were observed in pouches treated with betel quid alone for all killing periods.
CONCLUSION: Our results indicate Taiwan betel quid may be a co-carcinogen in human oral carcinogenesis, if extrapolation can be made from the current animal study. 相似文献
MATERIALS AND METHODS: Two hundred and fifty-two non-inbred mate adult Syrian golden hamsters were randomly divided into six groups, each containing forty-two animalS. A treatment regimen over a 14-week experimental period was employed with six animals per group being killed at seven different periods (every 2 weeks). The right buccal pouch of each animal was painted three times a week with various combinations of 7, 12-dimethylbenz[a]anthracene (DMBA), Taiwan betel quid extract, dimethyl sulfoxide (DMSO) and mineral oil.
RESULT: Both the number and size of tumors in animals concurrently treated with DMBA and betel quid were significantly higher than those in animals treated with DMBA alone in each killing period of 8, 10, 12 and 14 weekS. No visible tumors but hyperkeratosis and acanthosis were observed in pouches treated with betel quid alone for all killing periods.
CONCLUSION: Our results indicate Taiwan betel quid may be a co-carcinogen in human oral carcinogenesis, if extrapolation can be made from the current animal study. 相似文献
44.
This study compares the shear bond strengths of plastic brackets with a mechanical base and metal brackets using two different adhesives, and examines the modes of failure using a scanning electron microscope (SEM). Forty extracted human premolars were selected for bonding. Two types of brackets: metal and plastic-Spirit MB, and two orthodontic adhesives: System 1 + and Enlight, were used. After bonding, all samples were put into a 37 degrees C distilled water bath for 24 hours before shear bond strengths were tested. The bond strengths of the plastic brackets were significantly lower than those of the metal brackets (P < .0001). There was a statistically significant difference in bond strengths between System 1 + and Enlight for plastic brackets (P < .05), but not for metal brackets. The modes of failure predominantly occurred at the enamel/adhesive interface in the metal bracket-System 1 + group, within the adhesive in the metal bracket-Enlight and plastic bracket-System 1 + groups, and at the bracket/adhesive interface in the plastic bracket-Enlight group. 相似文献
45.
46.
Risk factors for dental implant failure: a strategy for the analysis of clustered failure-time observations 总被引:4,自引:0,他引:4
This study's objective was to identify, in a statistically valid and efficient manner, the risk factors associated with dental implant failure. We hypothesize that factors exist which can be modified by clinicians to enhance outcome. A retrospective cohort study design was used. Cohort members had >or= one implant placed. Risk factors were classified as demographic, health status, implant-, anatomic-, or prosthetic-specific, and reconstructive variables. The outcome variable was implant failure. The cohort was composed of 677 patients who had 2349 implants placed. Based on the adjusted multivariate model, factors associated with implant failure were tobacco use, implant length, staging, well size, and immediate implants (p 相似文献
47.
48.
目的 运用数据挖掘技术分析国内外针灸治疗阿尔茨海默病的选穴规律。方法 检索建库至2020年12月31日中国期刊全文数据库(CNKI)、维普中文期刊服务平台(VIP)、万方数据知识服务平台(Wanfang)、Web of Science、Pubmed、Embase、Cochrane Library数据库收录的针灸治疗阿尔茨海默病的相关文献,采用Microsoft Excel 2019建立针灸处方数据库,对腧穴、经脉进行频数统计,并运用IBM SPSS Modeler 18.0软件对腧穴、经脉进行关联规则分析。结果 共纳入182篇文献,包括308个针灸处方、96个腧穴,腧穴使用总频次为1 928次。其中,主要选取的经脉为督脉及足三阳经;腧穴主要分布于头面、下肢和上肢;累计应用频次最高的腧穴为百会、四神聪、足三里;特定穴多使用交会穴;腧穴配伍以大椎→百会最为常见。结论 国内外针灸治疗阿尔茨海默病重视督脉及足三阳经的使用;取穴以近部取穴及远近配穴为主;重视特定穴使用,尤其是交会穴。 相似文献
49.
目的归纳膀胱副神经节瘤的临床一般特征、诊断及治疗。方法收集兰州大学第二医院2013年3月—2020年8月所有膀胱肿瘤患者术后病理结果,对术后病理证实为副神经节瘤的7例患者的临床资料及随访结果进行回顾性分析。结果7例中术前明确诊断2例。7例均成功完成手术治疗。经尿道膀胱肿瘤电切术4例[2例术程平稳;2例术中出现血压剧烈波动,经过积极降压1例最终完成手术、另1例取活检后终止手术(院外积极酚苄明准备,3月后再次入院行腹腔镜下膀胱部分切除术)];1例行经尿道膀胱肿瘤激光剜除术,术程平稳;腹腔镜下膀胱部分切除3例(包括上述因术中血压无法有效控制中止手术者1例),平均手术时间130(30~180)min,平均术中出血30(20~50)mL。术后无相关并发症发生,术后住院3~5 d后恢复良好出院。1例发现肿瘤远处转移建议转外院继续治疗。7例均获随访,全身转移1例于外院治疗效果不佳,其余6例症状均有所改善,影像学检查未发现复发征象。远期结果仍有待进一步随访。结论膀胱副神经节瘤术前明确诊断困难,往往误诊为膀胱恶性肿瘤。手术为一线治疗方式,腹腔镜下膀胱部分切除术体现出微创优势,术后恢复快,部分选择性病例采用经尿道膀胱肿瘤电切术,同样可取得良好临床结果。 相似文献
50.
自噬是细胞清除胞质中受损、缺陷或无用的细胞器、长寿命蛋白质和脂质,并回收其成分以满足生物新陈代谢的营养和能量需要的主要分解代谢过程。急性胰腺炎(AP)是常见临床急症,其发病率也逐年升高。研究显示,自噬在AP的发病过程中起到重要作用,可以导致胰腺腺泡细胞内胰蛋白酶原的激活,腺泡细胞内大液泡积聚,诱发促炎介质的释放,引起胰腺炎症细胞浸润和全身性炎症反应。笔者就自噬的分子机制以及自噬在AP发生、发展中作用机制的研究进展进行综述。 相似文献