全文获取类型
收费全文 | 54948篇 |
免费 | 4708篇 |
国内免费 | 1233篇 |
专业分类
耳鼻咽喉 | 829篇 |
儿科学 | 508篇 |
妇产科学 | 160篇 |
基础医学 | 2002篇 |
口腔科学 | 2236篇 |
临床医学 | 8636篇 |
内科学 | 6109篇 |
皮肤病学 | 191篇 |
神经病学 | 2901篇 |
特种医学 | 17742篇 |
外国民族医学 | 27篇 |
外科学 | 4862篇 |
综合类 | 6244篇 |
现状与发展 | 4篇 |
预防医学 | 868篇 |
眼科学 | 3085篇 |
药学 | 1407篇 |
8篇 | |
中国医学 | 156篇 |
肿瘤学 | 2914篇 |
出版年
2024年 | 75篇 |
2023年 | 1041篇 |
2022年 | 1508篇 |
2021年 | 2434篇 |
2020年 | 2047篇 |
2019年 | 1817篇 |
2018年 | 1860篇 |
2017年 | 1779篇 |
2016年 | 1889篇 |
2015年 | 1904篇 |
2014年 | 3773篇 |
2013年 | 2995篇 |
2012年 | 3328篇 |
2011年 | 3558篇 |
2010年 | 3115篇 |
2009年 | 3221篇 |
2008年 | 3149篇 |
2007年 | 3182篇 |
2006年 | 2837篇 |
2005年 | 2415篇 |
2004年 | 1963篇 |
2003年 | 1629篇 |
2002年 | 1331篇 |
2001年 | 1192篇 |
2000年 | 934篇 |
1999年 | 797篇 |
1998年 | 607篇 |
1997年 | 625篇 |
1996年 | 491篇 |
1995年 | 468篇 |
1994年 | 417篇 |
1993年 | 304篇 |
1992年 | 245篇 |
1991年 | 207篇 |
1990年 | 195篇 |
1989年 | 190篇 |
1988年 | 164篇 |
1987年 | 177篇 |
1986年 | 125篇 |
1985年 | 155篇 |
1984年 | 161篇 |
1983年 | 94篇 |
1982年 | 140篇 |
1981年 | 114篇 |
1980年 | 78篇 |
1979年 | 61篇 |
1978年 | 34篇 |
1977年 | 39篇 |
1976年 | 23篇 |
1974年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
《European journal of surgical oncology》2020,46(6):982-990
IntroductionLung cancer is the leading cause of cancer-death worldwide. The U.S. Preventative Services Task Force (USPTSF) approved screening for current or former smokers aged 55–80 based on the results of the National Lung Screening trial (NLST). Following the NLST, new evidence has emerged from clinical trials and updates to previous trials prior to the anticipated update to the USPSTF guideline. We review the new evidence on lung cancer screening with low dose computed tomography (LDCT) and the surgical implications.MethodsA review of new literature was performed pertaining to lung cancer screening since implementation of UPSTF guidelines. Articles for inclusion were identified by both authors’, then search of the Pubmed and Cochrane database was performed from January 1st, 2013 through February 4th, 2020 using the MeSH search terms: “lung cancer”; “screening”; “low dose CT”. The results of these studies are summarized.ResultsWe identified multiple prospective randomized control trials and meta-analysis since the NLST supporting lung cancer-specific mortality with screening. We identified new nodule classification systems and the development of risk-models which may reduce false positive rates and identify high risk patients not currently eligible for screening. Finally, we discussed the surgical implications of screening.ConclusionNew data supports NLST findings and show ongoing benefit to LDCT for lung cancer screening. Standardized LDCT screening classification has been shown to reduce harm and lower false positive rates. Further study is needed regarding use of risk-modeling. Screening will require an increase in the thoracic workforce to accommodate the amount of surgically operable cancers. 相似文献
82.
《Journal of endodontics》2020,46(5):662-667
IntroductionThe aim of this study was to evaluate the amount of root canal dentin removed and apical transportation occurrence after instrumentation of mesiobuccal canals of maxillary molars with ProTaper Next (PTN [Dentsply Maillefer, Ballaigues, Switzerland]), OneShape (OS [MicroMega, Besançon, France]), and EdgeFile (EF [Edge Endo, Albuquerque, NM]) rotary systems.MethodsTwenty-seven mesiobuccal canals of maxillary molars were used. Canals were randomly divided into 3 groups for canal preparation: PTN, EF X3, or OS (n = 9 for each group). Micro–computed tomographic imaging was used to measure apical transportation (mm) and the volume of dentin removed (mm3). The amount of dentin removed was measured for the coronal portion and for the whole canal length. Superposition of pre- and postoperative cross-sectional apical slices were used to measure apical transportation at 1 mm from the apex; the differences were evaluated using the Kruskal-Wallis test and Wilcoxon analysis. The Spearman correlation coefficient was used to display the relationship between variables for each group. The significance level was set at P < .05.ResultsThe percentages of the amount of dentin removed on the coronal portion and the amount removed for the whole canal length were statistically similar between groups (P > .05). The average amount of apical transportation for the PTN, OS, and EF X3 were 0.197, 0.263, and 0.218 mm, respectively. Statistically, there were no significant differences between the 3 rotary instruments for apical transportation.ConclusionsThe amount of dentin removed for the coronal third portion and the whole canal length was similar for the PTN, OS, and EF X3 rotary instruments. Although there were differences in the sizes of apical enlargement, no apical transportation was observed in any of the instrumentation systems. 相似文献
83.
目的 测量并比较白内障摘除术中不同型号人工晶状体(IOL)植入后在眼内的居中性。设计 回顾性病例系列。研究对象 连续收集2019年12月在北京同仁医院眼科进行白内障摘除IOL植入术后6个月复诊的患者120例(120眼)。方法 根据所植入IOL的型号不同分为A、B、C三组,每组40例。对术眼进行前段扫频OCT(AS-SS-OCT)检查。同一轴线上IOL中心与巩膜突连线中点的距离为IOL偏心度,IOL平面与巩膜突平面间的夹角为IOL倾斜度。分别测量水平方向和垂直方向的偏心度和倾斜度,并进行组间比较。主要指标 IOL在水平方向和垂直方向的偏中心度和倾斜度。结果 A组水平方向偏心度为(0.24±0.07)mm (0.11~0.39 mm),倾斜角度为(1.41±0.64)° (0.48~2.68°),垂直方向偏心度为(0.23±0.08)mm (0.11~0.47mm),倾斜角度为(1.79±0.91)° (1.02-4.72°)。B组水平方向偏心度为(0.23±0.08)mm (0.11~0.43 mm),倾斜角度为(1.59±1.19)° (0.44~3.61°),垂直方向偏心度为(0.23±0.07)mm (0.14~0.41 mm),倾斜角度为(2.09±1.31)° (0.56~5.04°)。C组水平方向偏心度为(0.28±0.12)mm (0.13~0.49 mm),倾斜角度为(1.86±1.21)° (0.26~3.71°),垂直方向偏心度为(0.31±0.17)mm (0.23~0.46 mm),倾斜角度为(2.01±1.01)° (0.61~4.86°)。三组间水平和垂直方向的偏心程度和倾斜角度差异均无显著性 (P均>0.05)。三组患者在充分矫正屈光不正后,均未出现炫光等不适主诉。结论 白内障摘除IOL植入术后IOL偏中心的发生与所植入IOL的类型可能无关;在IOL偏中性度<0.5 mm、倾斜度<5°的情况未导致术后的不良视觉现象。 相似文献
84.
《Radiologia》2022,64(3):245-255
ObjectiveTo review the main findings for anisakiasis in the different imaging tests that can be used to diagnose it, based on studies done at our center.ConclusionThe presence of Anisakis species in food consumed in Western countries is becoming more common. Patients with anisakiasis present with acute abdomen; there are no specific clinical signs or laboratory findings. Careful history taking is key to discovering exposure to Anisakis-contaminated food, but this task is hindered by unfamiliarity with the condition and lack of suspicion and is also confounded by the variable latency period after ingestion of Anisakis-contaminated food. Give the nonspecific presentation, patients with anisakiasis often undergo imaging tests to rule out other processes. Thus, radiologists need to be familiar with the spectrum of imaging findings that should lead to the inclusion of anisakiasis in the differential diagnosis, so they can guide clinicians toward directed history taking and specific tests. 相似文献
85.
86.
87.
《Journal of endodontics》2020,46(11):1712-1718
IntroductionThe preparation of flattened root canals using reciprocating or rotary nickel-titanium instruments associated with the Flatsonic ultrasonic tip (Helse Ultrasonic, Santa Rosa de Viterbo, SP, Brazil) was evaluated by micro–computed tomographic imaging.MethodsTwenty-four flattened distal canals of mandibular molars with a buccolingual diameter 4 or more times larger than the mesiodistal diameter were selected. The root canals were randomly divided into 2 experimental groups for preparation: a Reciproc Blue (RB; VDW GmbH, Munich, Germany) 40/.06 file in reciprocating motion or ProDesign Logic (PDL; Easy Equipamentos Odontológicos, Belo Horizonte, MG, Brazil) 40/.01 and 40/.05 files in rotary motion (n = 12). A complementary preparation was performed with the Flatsonic ultrasonic tip for both preparations. Micro–computed tomographic scanning at a resolution of 8.74 μm was performed before and after preparation with the nickel-titanium instruments and after the use of the Flatsonic tip. The percentages of increase in volume, debris, and uninstrumented surface were analyzed. The data obtained were submitted to the paired and unpaired t test, analysis of variance, and the Tukey test (α = 5%).ResultsThe percentage increase in volume, debris, and uninstrumented surface was similar between RB and PDL in the entire root canal (P > .05). The PDL promoted a lower percentage of debris in the cervical third and a lower percentage of increase in volume in the apical third in comparison with RB (P < .05). The Flatsonic decreased debris and uninstrumented surface after PDL preparation in all thirds (P < .05). After preparation with RB, the Flatsonic decreases the debris in the cervical third and the uninstrumented surface in the cervical and middle thirds (P < .05).ConclusionsThe preparation of flattened root canals using RB or PDL produced a high percentage of debris and uninstrumented surface. The Flatsonic ultrasonic tip significantly improved the cleaning of flattened root canals. 相似文献
88.
89.
90.
《Journal of Cardiovascular Computed Tomography》2020,14(6):478-482
BackgroundMultiple appropriate use criteria (AUC) exist for the evaluation of coronary artery disease (CAD), but there is little data on the agreement between AUC from different professional medical societies. The aim of this study is to compare the appropriateness of coronary computed tomography angiography (CCTA) exams assessed using multimodality AUC from the American College of Cardiology Foundation (ACCF) versus the American College of Radiology (ACR).MethodsIn a single-center prospective cohort study from June 2014 to 2016, 1005 consecutive subjects referred for evaluation of known or suspected CAD received a contrast-enhanced CCTA. The primary outcome was the agreement of appropriateness ratings using ACCF and ACR guidelines, measured by the kappa statistic. A secondary outcome was the rate of obstructive CAD by appropriateness rating.ResultsAmong 1005 subjects, the median (5–95th percentile) age was 59 (37–76) years with 59.0% male. The ACCF criteria classified 39.6% (n = 398) appropriate, 24.2% (n = 243) maybe appropriate, and 36.2% (n = 364) rarely appropriate. The ACR guidelines classified 72.3% (n = 727) appropriate, 2.6% (n = 26) maybe appropriate, and 25.1% (n = 252) rarely appropriate. ACCF and ACR appropriateness ratings were in agreement for 55.0% (n = 553). Overall, there was poor agreement (kappa 0.27 [95% confidence interval 0.23–0.31]). By both AUC methods, a low rate of obstructive CAD was observed in the rarely appropriate exams (ACCF 7.1% [n = 26 of 364] and ACR 13.5% [n = 34 of 252]).ConclusionsCompared to ACCF criteria, the ACR guidelines of appropriateness were broader and classified significantly more CCTA exams as appropriate. The poor agreement between appropriateness ratings from the ACCF and ACR AUC guidelines evokes implications for reimbursement and future test utilization. 相似文献