全文获取类型
收费全文 | 8417篇 |
免费 | 797篇 |
国内免费 | 366篇 |
专业分类
耳鼻咽喉 | 29篇 |
儿科学 | 69篇 |
妇产科学 | 78篇 |
基础医学 | 597篇 |
口腔科学 | 109篇 |
临床医学 | 1052篇 |
内科学 | 1007篇 |
皮肤病学 | 124篇 |
神经病学 | 556篇 |
特种医学 | 109篇 |
外科学 | 366篇 |
综合类 | 729篇 |
一般理论 | 1篇 |
预防医学 | 1158篇 |
眼科学 | 90篇 |
药学 | 2045篇 |
6篇 | |
中国医学 | 1309篇 |
肿瘤学 | 146篇 |
出版年
2024年 | 26篇 |
2023年 | 156篇 |
2022年 | 192篇 |
2021年 | 408篇 |
2020年 | 344篇 |
2019年 | 398篇 |
2018年 | 318篇 |
2017年 | 424篇 |
2016年 | 408篇 |
2015年 | 382篇 |
2014年 | 569篇 |
2013年 | 1129篇 |
2012年 | 528篇 |
2011年 | 505篇 |
2010年 | 363篇 |
2009年 | 348篇 |
2008年 | 382篇 |
2007年 | 370篇 |
2006年 | 355篇 |
2005年 | 287篇 |
2004年 | 250篇 |
2003年 | 236篇 |
2002年 | 193篇 |
2001年 | 169篇 |
2000年 | 101篇 |
1999年 | 86篇 |
1998年 | 105篇 |
1997年 | 85篇 |
1996年 | 65篇 |
1995年 | 45篇 |
1994年 | 39篇 |
1993年 | 37篇 |
1992年 | 38篇 |
1991年 | 22篇 |
1990年 | 18篇 |
1989年 | 26篇 |
1988年 | 18篇 |
1987年 | 18篇 |
1986年 | 15篇 |
1985年 | 20篇 |
1984年 | 21篇 |
1983年 | 12篇 |
1982年 | 16篇 |
1981年 | 10篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1974年 | 2篇 |
排序方式: 共有9580条查询结果,搜索用时 31 毫秒
61.
Maki Yoshikawa Masashi Hosokawa Kazuo Miyashita Hoyoku Nishino Takeshi Hashimoto 《Nutrients》2021,13(4)
Fucoxanthin (Fx) has preventive effect against muscle atrophy and myotube loss in vitro, but it has not yet been examined in vivo. Therefore, we aimed to investigate the effect of Fx on dexamethasone (Dex)-induced muscle atrophy and fat mass in mice. ICR mice were fed with Fx diets from 2 weeks before Dex treatment to the end of the study. Muscle atrophy was induced in the mice by oral administration of Dex. Body weight was significantly lower by Dex treatment. Visceral fat mass in the Fx-treated group were significantly lower than those in the control group. The Dex-induced decrease in tibialis anterior muscle mass was ameliorated by Fx treatment. Fx treatment significantly attenuated muscle lipid peroxidation compared with the control and Dex-treated groups. The phosphorylation of AMPK was significantly higher in the Dex-treated group than in the control group. The expression of cytochrome c oxidase (COX) IV was significantly higher in the Fx-treated group than in the control group. These results suggest that Fx may be a beneficial material to prevent muscle atrophy in vivo, in addition to the effect of fat loss. 相似文献
62.
Daniela Vitucci Angela Amoresano Marcella Nunziato Simona Muoio Andreina Alfieri Giovannangelo Oriani Luca Scalfi Luigi Frusciante Maria Manuela Rigano Piero Pucci Luigi Fontana Pasqualina Buono Francesco Salvatore 《Nutrients》2021,13(4)
The isoforms of lycopene, carotenoids, and their derivatives including precursors of vitamin A are compounds relevant for preventing chronic degenerative diseases such as cardiovascular diseases and cancer. Tomatoes are a major source of these compounds. However, cooking and successive metabolic processes determine the bioavailability of tomatoes in human nutrition. To evaluate the effect of acute/chronic cooking procedures on the bioavailability of lycopene and carotene isoforms in human plasma, we measured the blood levels of these compounds and of the serum antioxidant potential in volunteers after a meal containing two different types of tomato sauce (rustic or strained). Using a randomized cross-over administration design, healthy volunteers were studied, and the above indicated compounds were determined by HPLC. The results indicate an increased bioavailability of the estimated compounds and of the serum antioxidant potential with both types of tomato purée and the subsequently derived sauces (the increase was greater with strained purée). This study sheds light on the content of nutrient precursors of vitamin A and other antioxidant compounds derived from tomatoes cooked with different strategies. Lastly, our study indicates that strained purée should be preferred over rustic purée. 相似文献
63.
Evdokia Valsamidou Aristea Gioxari Charalampia Amerikanou Panagiotis Zoumpoulakis George Skarpas Andriana C. Kaliora 《Nutrients》2021,13(5)
Osteoarthritis (OA) is the most common form of arthritis and a major cause of limited functionality and thus a decrease in the quality of life of the inflicted. Given the fact that the existing pharmacological treatments lack disease-modifying properties and their use entails significant side effects, nutraceuticals with bioactive compounds constitute an interesting field of research. Polyphenols are plant-derived molecules with established anti-inflammatory and antioxidant properties that have been extensively evaluated in clinical settings and preclinical models in OA. As more knowledge is gained in the research field, an interesting approach in the management of OA is the additive and/or synergistic effects that polyphenols may have in an optimized supplement. Therefore, the aim of this review was to summarize the recent literature regarding the use of combined polyphenols in the management of OA. For that purpose, a PubMed literature survey was conducted with a focus on some preclinical osteoarthritis models and randomized clinical trials on patients with osteoarthritis from 2018 to 2021 which have evaluated the effect of combinations of polyphenol-rich extracts and purified polyphenol constituents. Data indicate that combined polyphenols may be promising for the treatment of osteoarthritis in the future, but more clinical trials with novel approaches in the identification of the in-between relationship of such constituents are needed. 相似文献
64.
Curcumin is one of the most frequently researched herbal substances; however, it has been reported to have a poor bioavailability and fast metabolism, which has led to doubts about its effectiveness. Curcumin has antioxidant and anti-inflammatory effects, and has demonstrated favorable health effects. Nevertheless, well-reported in vivo pharmacological activities of curcumin are limited by its poor solubility, bioavailability, and pharmacokinetic profile. The bidirectional interactions between curcumin and gut microbiota play key roles in understanding the ambiguity between the bioavailability and biological activity of curcumin, including its wider health impact. 相似文献
65.
目的 分析户外活动时间与学龄前参加文化课学习情况的交互作用与中小学生视力不良的关系,为制定防控中小学生视力不良的策略和措施提供科学依据。方法 采用分层整群随机抽样法于2018年9-11月在湖南省抽取8 467名小学四年级到高中三年级学生进行体格检查和问卷调查。相乘交互作用建立多因素Logistic回归模型,并计算交互作用超额危险度(RERI)、交互作用归因比(API)及交互作用指数 S (Index S)探讨户外活动时间与学龄前文化课学习对视力不良的相加交互作用。结果 8 467名调查对象中视力不良检出人数为5 612名,检出率为66.28%。学龄前参加过文化课学习者,视力不良的发生风险是不参加学习者的1.500倍(95%CI:1.331~1.689,P<0.001),每日户外活动<2 h的学生发生视力不良的风险是每日户外活动≥2 h者的1.247倍(95%CI:1.103~1.409,P<0.001)。户外活动时间与学龄前文化课学习的交互作用项具有统计学意义(P交互=0.003)。在调整相关因素后,户外活动时间与学龄前文化课学习的RERI、API、Index S分别为0.529、0.310、3.973。结论 中小学生户外活动时间、学龄前文化课学习均与视力不良发生风险相关,并两者对视力不良有交互作用。因此,应加强学龄前儿童的户外活动,以预防视力不良发生。 相似文献
66.
Huiguang Ren Xing He Xiaohua Bian Xinhua Shang Junsheng Liu 《The Journal of adolescent health》2021,68(1):35-42
PurposeAdolescents are particularly vulnerable during the COVID-19 quarantine periods and may be at risk for developing psychological distress symptoms that extend beyond a crisis, including depression. This study examined adolescents’ postquarantine depressive symptoms associated with pandemic stressors. The primary aim was to identify potential protective factors that may buffer the association between the presence of COVID-19 cases in adolescents’ communities and their postquarantine depressive symptoms.MethodsAdolescents from public schools were recruited from Zhengzhou city, Henan, China (N = 1,487, Mage=13.14 years, 50% girls). Adolescents reported the presence of confirmed or suspected COVID-19 cases in their communities, their daily activities and routines during the 2-month quarantine period, and depressive symptoms after the quarantine period.ResultsThe presence of cases in adolescents’ communities during the quarantine contributed to more depressive symptoms in adolescents after the quarantine. This association was buffered by adolescents’ spending more time on physical activities and better maintenance of daily living routines during the quarantine period. The presence of community infection was also more strongly associated with depressive symptoms in older adolescents.ConclusionsThe presence of COVID-19 cases in communities contributed to adolescents’ poorer mental health, and the association was stronger for older adolescents. Spending time on physical activities and maintaining daily living routines during the quarantine appear to be practical strategies that can be used by adolescents to mitigate the association between pandemic stressors and their diminishing mental health. 相似文献
67.
Silver nanoparticles (SNPs) can pass from the cell membrane and testicular blood barrier due to their small size, and by increasing oxidative stress they cause disorder in the male reproductive system. Kombucha is a traditional fermented drink with detoxification and potent antioxidant properties. We aimed to examine the protective effect of Kombucha against the damages due to SNPs on the testis tissue. In this experimental study, NMRI mice were randomly separated into four groups (n = 6), namely control (distilled water), SNPs (500 mg/kg), Kombucha extract (9 ml/kg) and SNPs + Kombucha, and were treated with gavage for 35 days. A significant decrease in testosterone level and total antioxidant capacity, and a significant increase in malondialdehyde concentration was observed in the SNPs group in comparison with the control group. Histological studies on the testis of mice treated with SNPs showed vacuolation, decrease in generational epithelium thickness, seminiferous tubules diameter, testis volume and the number of spermatozoa in lumen of the seminiferous tubule and increase in the volume of interstitial space while the mentioned parameters were improved in the SNPs + Kombucha group compared to the SNPs group. Kombucha reduces the adverse effects of SNPs on testis tissue and improves the function of the male reproductive system. 相似文献
68.
Christopher C. Stahl Sarah A. Jung Alexandra A. Rosser Aaron S. Kraut Benjamin H. Schnapp Mary Westergaard Azita G. Hamedani Rebecca M. Minter Jacob A. Greenberg 《American journal of surgery》2021,221(2):369-375
BackgroundEntrustable Professional Activities (EPAs) contain narrative ‘entrustment roadmaps’ designed to describe specific behaviors associated with different entrustment levels. However, these roadmaps were created using expert committee consensus, with little data available for guidance. Analysis of actual EPA assessment narrative comments using natural language processing may enhance our understanding of resident entrustment in actual practice.MethodsAll text comments associated with EPA microassessments at a single institution were combined. EPA—entrustment level pairs (e.g. Gallbladder Disease—Level 1) were identified as documents. Latent Dirichlet Allocation (LDA), a common machine learning algorithm, was used to identify latent topics in the documents associated with a single EPA. These topics were then reviewed for interpretability by human raters.ResultsOver 18 months, 1015 faculty EPA microassessments were collected from 64 faculty for 80 residents. LDA analysis identified topics that mapped 1:1 to EPA entrustment levels (Gammas >0.99). These LDA topics appeared to trend coherently with entrustment levels (words demonstrating high entrustment were consistently found in high entrustment topics, word demonstrating low entrustment were found in low entrustment topics).ConclusionsLDA is capable of identifying topics relevant to progressive surgical entrustment and autonomy in EPA comments. These topics provide insight into key behaviors that drive different level of resident autonomy and may allow for data-driven revision of EPA entrustment maps. 相似文献
69.
Jessica E. Rabski Ashirbani Saha Michael D. Cusimano 《American journal of surgery》2021,221(2):388-393
BackgroundCompetency-based medical education requires evaluations of residents’ performances of tasks of the discipline (ie. entrustable professional activities (EPAs)). Using neurosurgical Faculty perspectives, this study investigated whether a sample of neurosurgical EPAs accurately reflected the expectations of general neurosurgical practice.MethodA questionnaire was sent to all Canadian neurosurgery Faculty using a SurveyMonkey® platform.ResultsThe proportion of respondents who believed the EPAs were representative of general neurosurgery competences varied significantly across all EPAs [47%–100%] (p < 0.0001). For 9/15 proposed EPAs, ≥75% agreed they were appropriate for general neurosurgery training and expected residents to attain the highest standard of performance. However, a range of 27–53% of the respondents felt the other six EPAs would be more appropriate for fellowship training and thus, require a lower standard of performance from graduating residents.ConclusionThe shift towards subspecialization in neurosurgery has implications for curriculum design, delivery and certification of graduating residents. 相似文献
70.
Tea is a famous beverage that is produced from leaves of Camellia sinensis. Amongst the six major tea categories in China, dark tea is the only one that involves microbial fermentation in the manufacturing process, which contributes unique flavors and functions for the tea. In the recent decade, the reports about the biofunctions of dark teas have increased rapidly. Therefore it may be the proper time to consider dark tea as one potential homology of medicine and food. In this viewpoint, our current understanding of the chemical constituents, biological activities and possible health beneficial effects of dark teas were introduced. Some future directions and challenges to the development perspectives of dark teas were also discussed. 相似文献