首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   21822篇
  免费   1825篇
  国内免费   447篇
耳鼻咽喉   478篇
儿科学   178篇
妇产科学   247篇
基础医学   1360篇
口腔科学   1351篇
临床医学   1711篇
内科学   1991篇
皮肤病学   1470篇
神经病学   677篇
特种医学   1114篇
外国民族医学   1篇
外科学   4228篇
综合类   2904篇
预防医学   661篇
眼科学   3539篇
药学   1088篇
  8篇
中国医学   715篇
肿瘤学   373篇
  2024年   15篇
  2023年   347篇
  2022年   396篇
  2021年   731篇
  2020年   808篇
  2019年   654篇
  2018年   619篇
  2017年   746篇
  2016年   832篇
  2015年   717篇
  2014年   1394篇
  2013年   1461篇
  2012年   1176篇
  2011年   1321篇
  2010年   1123篇
  2009年   1104篇
  2008年   1089篇
  2007年   1123篇
  2006年   994篇
  2005年   861篇
  2004年   773篇
  2003年   650篇
  2002年   550篇
  2001年   564篇
  2000年   419篇
  1999年   318篇
  1998年   316篇
  1997年   282篇
  1996年   261篇
  1995年   272篇
  1994年   277篇
  1993年   243篇
  1992年   226篇
  1991年   201篇
  1990年   169篇
  1989年   148篇
  1988年   140篇
  1987年   122篇
  1986年   115篇
  1985年   132篇
  1984年   112篇
  1983年   76篇
  1982年   56篇
  1981年   57篇
  1980年   34篇
  1979年   18篇
  1978年   17篇
  1977年   5篇
  1976年   6篇
  1974年   5篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
目的:探索不同功率的水冷激光对于不同种植体表面的影响。方法:收集临床上因种植体周围炎而拔除的不同表面种植体,分别用2、3、4 W 3种不同参数的水冷激光处理,通过扫描电镜(SEM)进行观察比较。结果:SLA?非亲水表面和INICELL?表面3~4 W的激光处理既能很好的去污又不会造成表面损伤;Tiunite?表面和国产MDIC种植体微弧氧化表面在2 W时去污效果欠佳,而3 W与4 W去污效果相当,4 W时会导致表面损伤。结论:随着功率的增大,水冷激光去污效果逐渐加强。不同激光参数对于不同种植体表面的影响不同,其中氧化类表面更易崩解,而喷砂酸蚀表面耐受激光的能力更强。  相似文献   
2.
目的 研究不同浓度细菌脂多糖(Lipopolysaccharides,LPS)对选择性激光熔化技术(Selective laser melting,SLM)制作的钴铬钼合金腐蚀行为的影响。方法 分别以SLM法及铸造法各制作12个钴铬钼合金试件,根据在腐蚀电解液中LPS浓度(0、0.15、15、150 μg/mL)不同分为4组,每组3个试件。采用电化学阻抗谱、动电位极化测试法分析2组合金试件在不同浓度脂多糖(LPS)中的腐蚀行为。结果 在单纯人工唾液中,SLM合金和铸造合金的腐蚀参数无统计学上的差异(P> 0.05)。当LPS浓度为150 μg/mL时,SLM合金和铸造合金的电阻(Rp)均显著下降且自腐蚀电流密度(Icorr)显著增大,但SLM合金的Rp值大于铸造合金且Icorr值较小(P< 0.05)。结论 LPS对SLM法和铸造法制作的钴铬钼合金的腐蚀行为均有不利影响,但对SLM法制作的合金的腐蚀影响小于铸造法制得的合金。  相似文献   
3.
4.
5.
Tsukamurella species are obligate aerobic, gram-positive, weak acid-fast, nonmotile bacilli. They are found in various environments, such as soil, water, sludge, and petroleum reservoir wastewater, and belong to the order Actinomycetales. In 2016, there was a reclassification of species within the genus Tsukamurella, merging the species Tsukamurella tyrosinosolvens (T. tyrosinosolvens) and Tsukamurella carboxydivorans. Tsukamurella species are clinically considered to be a rare opportunistic pathogen, because most reported cases have been related to bacteremia and intravascular prosthetic devices and immunosuppression. To date, it has been isolated only from human specimens, and has always been associated with clinical disease; human infections are very rare. Reported infections have included pneumonia, brain abscesses, catheter-related bloodstream infections, ocular infections, bacteremia, and sepsis presenting with septic pulmonary emboli in patients who are immunocompromised. To date, there is no commercially available test for identification. On the other hand, sequence-based identification, including matrix-assisted laser desorption ionization time-of-flight mass spectrometry, is an alternative method for identifying clinical isolates that are either slow growers or difficult to identify through biochemical profiling. The golden standards for diagnosis and optimal management still remain to be determined. However, newer molecular biological techniques can provide accurate identification, and contribute to the appropriate selection of definitive therapy for infections caused by this organism. Combinations of several antimicrobial agents have been proposed for treatment, though the length of treatment for infections has yet to be determined, and should be individualized according to clinical response. Immunocompromised patients often experience severe cases due to infection, and life-threatening T. tyrosinosolvens events associated with dissemination and/or failure of source control have occurred. Favorable prognoses can be achieved through earlier identification of the cause of infection, as well as successful management, including appropriate antibiotic therapy together with source control. Further analyses of similar cases are required to establish the most adequate diagnostic methods and treatment regimens for infections.  相似文献   
6.
目的探讨超脉冲CO2点阵激光联合胶原贴敷料治疗面部痤疮瘢痕的临床效果。方法选取2020年1月至2021年1月宜阳县人民医院收治的60例面部痤疮瘢痕患者作为研究对象,并按照随机数表法将其随机分为观察组和对照组,每组30例,观察组患者采用超脉冲CO2点阵激光联合胶原贴敷料治疗,对照组患者单纯采用超脉冲CO2点阵激光治疗,对比两组患者面部美观度与皮肤屏障功能变化情况、临床疗效以及不良反应发生情况。结果治疗结束后,观察组患者面部皮肤毛孔值、纹理值以及经皮水分丢失(TEWL)、pH值、皮肤红斑指数均明显低于对照组(t=13.490、8.883、2.204、2.692、5.931,P<0.001、P<0.001、P=0.032、P=0.009、P<0.001),角质层含水量明显高于对照组(t=2.752,P=0.008);观察组患者中痊愈10例、显效12例、有效6例、无效2例,明显优于对照组患者的痊愈6例、显效7例、有效9例、无效8例(Z=-2.285,P=0.022);治疗期间,观察组患者不良反应发生率为6.67%,明显低于对照组患者的不良反应发生率30.00%(χ2=5.455,P=0.020)。结论超脉冲CO2点阵激光联合胶原贴敷料治疗面部痤疮瘢痕,可明显改善面部美观度和皮肤屏障功能,疗效显著,且胶原贴敷料可明显降低CO2点阵激光治疗造成的不良反应发生率。  相似文献   
7.
When human remains are discovered, confirming the identification of the decedent is the first part of the forensic medical investigation. In cases where the remains are skeletonised or badly decomposed, differential preservation often increases the difficulty of this task. Bomb pulse dating, which directly compares levels of 14 C within human tissues to atmospheric levels, can provide an estimate of the year of death, which may assist in the identification process. This study measured the 14 C content in samples of hair, nail and puparia collected from donors at the Australian Facility for Taphonomic Experimental Research (AFTER). The radiocarbon results demonstrated that the nail samples provided the most accurate year of death estimation, with 91% correctly predicting YOD, closely followed by hair, with a 79% correct prediction rate, with both hair and nails having a lag time of 0–1 years. This is consistent with the time taken for atmospheric CO 2 to enter the food chain, and be taken in by humans. Puparia was found to have the highest levels of 14 C, and was the least consistent with the actual YOD (46% correct). However, predicted YOD ranges were still within 4 years of the actual YOD. Based on the results of this study, hair, nail and puparia should be considered as useful samples to obtain accurate estimates for YOD using bomb pulse dating.  相似文献   
8.
ObjectivesOsteoclasts can sense the surface topography of materials. However, it is difficult to identify the structural factors that affect osteoclast formation and its function. Furthermore, we hypothesized that the type of osteoclast precursor cells also affects osteoclastogenesis in the materials. In this study, we investigated the effects of defined micro/nanoscale patterns on osteoclastogenesis from bone marrow cells (BMCs).MethodsVarious cyclo-olefin polymer (COP) patterns were prepared using nanoimprinting. The effects of shape, size, and height of the patterns, and the wettability of the patterned surfaces on osteoclastogenesis from BMCs were evaluated in vitro.ResultsOsteoclast formation was promoted on pillars (diameter, 1 μm or 500 nm; height, 500 nm). Notably, osteoclastogenesis from BMCs was better promoted on hydrophobic pillars than on hydrophilic pillars. In contrast, decreased osteoclast formation was observed on the nanopillars (diameter, 100 nm; height, 200 nm).ConclusionsWe demonstrated the promotion of osteoclast formation from BMCs on hydrophobic pillars with diameters of 1 μm and 500 nm. Some cellular behaviors in the patterns were dependent on the type of osteoclast precursor cells. The designed patterns are useful for designing the surface of dental implants or bone replacement materials with a controllable balance between osteoblast and osteoclast activities.  相似文献   
9.
AIM: To identify the predictive factors and laser photocoagulation associated with the use of silicone oil as endotamponade during primary diabetic vitrectomy. METHODS: The medical and surgical records of 690 patients (798 eyes) who underwent primary diabetic vitrectomy at a tertiary eye hospital in China from January 2018 to December 2018 were reviewed in this retrospective cohort study. The patients’ baseline characteristics and preoperative treatments were recorded. The binary Logistic regression model was used to evaluate the risk factors for the use of silicone oil as endotamponade agent during primary vitrectomy for proliferative diabetic retinopathy (PDR)-related complications. RESULTS: Among 690 patients with mean age of 52.1±10.5y (range: 18-85y), 299/690 (43.3%) were female. The 31.6% of the eyes received preoperative laser treatment, and 72.4% of the eyes received preoperative anti-VEGF adjuvant therapy. Non-clearing vitreous haemorrhage (VH) alone or combined with retinal detachment was the main surgical indication (89.5%) for primary vitrectomy. Silicone oil was used as endotamponade in 313 (39.2%) eyes. Lack of preoperative laser treatment [odds ratio (OR) 0.66, 95% confidence interval (CI): 0.48-0.92; P=0.015] and older age (OR 0.96, 95%CI: 0.95-0.98; P<0.001) were predictors of silicone oil tamponade during primary vitrectomy for PDR. CONCLUSION: The lack of preoperative laser treatment is a significant predictor of silicone oil tamponade during primary vitrectomy for PDR. However, the severity of PDR relevant to silicone oil use should be further evaluated.  相似文献   
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号