全文获取类型
收费全文 | 15490篇 |
免费 | 821篇 |
国内免费 | 73篇 |
专业分类
耳鼻咽喉 | 131篇 |
儿科学 | 295篇 |
妇产科学 | 475篇 |
基础医学 | 1876篇 |
口腔科学 | 565篇 |
临床医学 | 1252篇 |
内科学 | 4378篇 |
皮肤病学 | 394篇 |
神经病学 | 1373篇 |
特种医学 | 317篇 |
外科学 | 2232篇 |
综合类 | 98篇 |
一般理论 | 2篇 |
预防医学 | 1113篇 |
眼科学 | 217篇 |
药学 | 845篇 |
中国医学 | 79篇 |
肿瘤学 | 742篇 |
出版年
2024年 | 11篇 |
2023年 | 160篇 |
2022年 | 390篇 |
2021年 | 652篇 |
2020年 | 350篇 |
2019年 | 532篇 |
2018年 | 707篇 |
2017年 | 410篇 |
2016年 | 420篇 |
2015年 | 481篇 |
2014年 | 734篇 |
2013年 | 842篇 |
2012年 | 1326篇 |
2011年 | 1335篇 |
2010年 | 683篇 |
2009年 | 612篇 |
2008年 | 1023篇 |
2007年 | 955篇 |
2006年 | 908篇 |
2005年 | 877篇 |
2004年 | 767篇 |
2003年 | 603篇 |
2002年 | 604篇 |
2001年 | 70篇 |
2000年 | 71篇 |
1999年 | 87篇 |
1998年 | 93篇 |
1997年 | 64篇 |
1996年 | 73篇 |
1995年 | 60篇 |
1994年 | 46篇 |
1993年 | 33篇 |
1992年 | 38篇 |
1991年 | 25篇 |
1990年 | 23篇 |
1989年 | 19篇 |
1988年 | 19篇 |
1987年 | 11篇 |
1986年 | 27篇 |
1985年 | 19篇 |
1984年 | 22篇 |
1983年 | 17篇 |
1982年 | 23篇 |
1981年 | 20篇 |
1980年 | 22篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1974年 | 12篇 |
1973年 | 20篇 |
1972年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Objetive
: To know Spanish Obstetrics and Gynaecology Society (SEGO) members about cesarean section on request.Method
Three questions appeared on SEGO web: 1) If a normal primigravid with a term, cephalic presentation foetus ask you for a caesarean section, would you do it?; 2) If a normal primigravid with a term, breach presentation foetus ask you for a caesarean section, would you do it?; 3) If a woman on her normal third pregnancy with two previous vaginal and with a term, breach presentation foetus ask you for a caesarean section, would you do it? Questions were asked in May 2006 and answers were collected 19th October 2006. Data analysis was processed with web page statistic method.Results
Among the 5300 members of SEGO, 1222 contacted the web page (23%). To question n° 1, 57.8% answered no, 24.8% yes and 17.4% had no answer. To question n° 2, 6.1% answered no, 93.8% yes and there were no abstention. To n° 3 question, 16.7% said no, 74.5% said yes and 8.8% has no opinion.Results are commented, advantages and disadvantages of caesarean are discussed as well as sanitary consequences of such an indication. 相似文献102.
André São Pedro Renan Fernandes Cristiane Flora Villarreal Rosana Fialho Elaine Cabral Albuquerque 《Journal of microencapsulation》2016,33(1):18-29
Context Opioids have been used as the reference treatment on chronic pain. However, they are related to serious adverse effects which affect the patient compliance to treatment, as well as, his quality of life. Particulate formulations have been investigated as an alternative to improve opioid efficacy and safety. Objective Summarise the available studies concerning micro and nanoencapsulated opioid formulations discussing their biopharmaceutical characteristics, such as composition, size, in vitro release, pharmacokinetic and antinociceptive profile. Methods Papers available in 1995–2015 at Medline, Science Direct and Web of Science databases were collected and assessed. Searches were performed using varied combinations of the keywords of this work. Results Opioid-loaded particles showed prolonged drug release with maintenance of serum therapeutic concentrations and extended analgesia when compared with the free drugs. The side effects incidences were reduced or maintained the same. Conclusion Particulate formulations can significantly increase both potency and safety profiles of opioids. 相似文献
103.
Pamela T. Soliman David Iglesias Mark F. Munsell Michael Frumovitz Shannon N. Westin Alpa M. Nick Kathleen M. Schmeler Pedro T. Ramirez 《Gynecologic oncology》2013
Background
The increasing role of robotic surgery in gynecologic oncology may impact fellowship training. The purpose of this study was to review the proportion of robotic procedures performed by fellows at the console, and compare operative times and lymph node yields to faculty surgeons.Methods
A prospective database of women undergoing robotic gynecologic surgery has been maintained since 2008. Intra-operative datasheets completed include surgical times and primary surgeon at the console. Operative times were compared between faculty and fellows for simple hysterectomy (SH), bilateral salpingo-oophorectomy (BSO), pelvic (PLND) and paraaortic lymph node dissection (PALND) and vaginal cuff closure (VCC). Lymph nodes counts were also compared.Results
Times were recorded for 239 SH, 43 BSOs, 105 right PLNDs, 104 left PLNDs, 34 PALND and 269 VCC. Comparing 2008 to 2011, procedures performed by the fellow significantly increased; SH 16% to 83% (p < 0.001), BSO 7% to 75% (p = 0.005), right PLND 4% to 44% (p < 0.001), left PLND 0% to 56% (p < 0.001), and VCC 59% to 82% (p = 0.024). Console times (min) were similar for SH (60 vs. 63, p = 0.73), BSO (48 vs. 43, p = 0.55), and VCC (20 vs. 22, p = 0.26). Faculty times (min) were shorter for PLND (right 26 vs. 30, p = 0.04, left 23 vs. 27, p = 0.02). Nodal counts were not significantly different (right 7 vs. 8, p = 0.17 or left 7 vs. 7, p = 0.87).Conclusions
Robotic surgery can be successfully incorporated into gynecologic oncology fellowship training. With increased exposure to robotic surgery, fellows had similar operative times and lymph node yields as faculty surgeons. 相似文献104.
Antonio Lpez-Uceda David Cantador-Fernndez Pedro Raposeiro Da Silva Jorge de Brito Jos María Fernndez-Rodríguez Jos Ramn Jimnez 《Materials》2022,15(15)
This study is framed within the circular economy model through the valorisation of industrial by-products. This research shows the results of producing self-compacting mortars (SCMs) with electric arc furnace dust (EAFD) and other industrial by-products such as fly ash, conforming (FA) or not conforming (NcFA), from coal-fired power plants, or recovery filler (RF) from hot-mix asphalt plants. Three batches of SCMs, each with one industrial-by product (FA, NcFA, or RF), and three levels of EAFD ratio incorporation (0%, 10%, 20%), were tested. An extra batch with a greater amount of FA was manufactured. When the incorporation ratio of EAFD rose, the mechanical strength decreased, due to the presence of a calcium zinc hydroxide dihydrate phase; nevertheless, this decrease diminished over time. All SCM mixes, except the 40C 40FA 20 EAFD mix, were above 20 MPa at 28 days. All mixes named 70C and 40C reached 40 and 30 MPa, respectively, at 90 days. Mixes with EAFD showed less capillarity and no difference in water absorption by immersion with respect to mixes without EAFD after 91 days. The SCMs designed proved to be stable in terms of leaching of the heavy metals contained in EAFD, where all the hardened SCMs were classified as inert. 相似文献
105.
Background: The association between vitamin D and weight gain remains controversial due to important limitations in the studies. We investigated the relationship between vitamin D levels and 5 and 10 years of weight and waist circumference change in a population-based prospective cohort study. Methods: Prospective study including participants aged between 35 and 75 years living in the city of Lausanne, Switzerland. Weight and waist change at 5- and 10-year follow-up were assessed according to baseline vitamin D status (normal, insufficiency and deficiency). Results: A total of 3638 participants (47.9 % women, mean age 51.6 ± 10.4 years) were included for the 5-year follow-up. No association was found between vitamin D categories and weight change, multivariate-adjusted average ± standard error: 1.6 ± 0.3, 1.5 ± 0.2 and 1.2 ± 0.1 kg for normal, insufficiency and deficiency, respectively, p = 0.159. For waist change, the corresponding values were 3.3 ± 0.4, 3.3 ± 0.2 and 3.4 ± 0.2 cm, p = 0.792. For the 10-year follow-up, data from 2999 participants (45.8% women, mean age 50.8 ± 10.3 years) were used. No association was found for weight 2.3 ± 0.4, 2.3 ± 0.2 and 2.0 ± 0.2 kg, p = 0.588, or for waist 3.7 ± 0.4, 3.6 ± 0.3 and 4.2 ± 0.2 cm for normal, insufficiency and deficiency, respectively, p = 0.259. Conclusion: No association between vitamin D status and weight or waist gain at 5- and 10-year follow-up was found. 相似文献
106.
Ignacio Ruiz del Olmo Izuzquiza Matilde Bustillo Alonso María Luisa Monforte Cirac Pedro Burgués Prades Carmelo Guerrero Laleona 《Anales de pediatría (Barcelona, Spain : 2003)》2017,86(3):115-121
Objective
To study the epidemiology, clinical features, diagnosis, therapeutic management, and outcome of non-tuberculous mycobacterial lymphadenitis in a paediatric population of Aragón (Spain).Material and methods
A retrospective study was conducted on patients under 15 years-old diagnosed with non-tuberculous mycobacterial lymphadenitis between the years 2000 and 2015. Inclusion criteria: patients with lymphadenitis and positive culture. Quantitative values are shown as mean, rank, and standard deviation, and qualitative data as frequencies.Results
Twenty-seven cases were registered, with a mean age of presentation of 39.9 months (range 10 months–8 years). The mean time between the symptoms onset and first consultation was 1.7 ± 1.1 months. The most frequent location was sub-maxilar in 17/27 cases (63%), on the right side in 59.3%, and size 2.96 ± 1.26 cm. Fistulae were observed in 16/27 cases. Tuberculin test was greater than 10 mm in 7/24 (29.1%). Microbiological cultures were positive for Mycobacterium avium in 14/27 (51.9%), Mycobacterium intracellulare 3/27 (11.1%), and Mycobacterium lentiflavum 3/27 (11.1%). Combined treatment of antibiotics and surgery was given in 16/27 cases (59.8%), medical treatment only in7/27 (25.9%), and surgical exeresis alone in 4/27 (14.8%). Two patients required a new surgery, and one showed severe neutropenia secondary to rifabutin. Only one case (3.7%) suffered from temporary facial palsy as sequel.Conclusions
The most frequent treatment was the combination of antibiotics and surgery. Delay in diagnosis seemed to be responsible for the limited number of exeresis as first option, only one for every seven patients. 相似文献107.
目的:报道经玻璃体腔内注射高剂量曲安奈德(triamcinolone acetonide,TA)联合光动力学疗法(photodynamic therapy,PDT)治疗老年性黄斑变性( age related macular degeneration, AMD)的脉络膜新生血管(choroidal neovascularization,CNV)后发生的脉络膜毛细血管萎缩。方法:我们采用非随机回顾性干涉治疗病例。在阿利坎特学院眼科,连续观察51眼(实验组)玻璃体腔内的注射(19.4±2.1)mg/0.1mL TA联合PDT治疗AMD的全部中心凹下型CNV患者,经过2a的随访,检查黄斑部脉络膜毛细血管和视网膜色素上皮细胞(RPE)萎缩情况。同时,采用单独PDT治疗的连续30眼患者作为对照组,其年龄,性别和AMD的CNV类型及大小与实验组相匹配。结果:随访24mo后,在治疗区域21/47眼(45%,实验组)和7/30眼(23%,对照组)发展成黄斑部RPE和脉络膜毛细血管萎缩(P=0.04,卡方检验)。实验组平均最大萎缩区域的直径为(5044±1666)μm,而对照组为(4345±1550)μm。在实验组中,RPE萎缩患者的平均最佳矫正视力为(0.87±0.33),而非RPE萎缩患者的平均最佳矫正视力为(0.66±0.26) (P=0.11,秩和U检验)。结论:玻璃体腔内注射大剂量TA联合PDT治疗可能会增加RPE和脉络膜毛细血管萎缩的风险。 相似文献
108.
Ruana Cardoso-Lima Joel Flix Silva Diniz Filho Maria Luiza de Araujo Dorneles Renato Simes Gaspar Pedro Filho Noronha Souza Clenilton Costa dos Santos Daniela Santoro Rosa Ralph Santos-Oliveira Luciana Magalhes Rebelo Alencar 《Viruses》2022,14(12)
Chikungunya virus (CHIKV) belongs to the genus Alphaviridae, with a single-stranded positive-sense RNA genome of 11.8 kbp encoding a polyprotein that generates both non-structural proteins and structural proteins. The virus is transmitted by the Aedes aegypti and A. albopictus mosquitoes, depending on the location. CHIKV infection leads to dengue-like musculoskeletal symptoms and has been responsible for several outbreaks worldwide since its discovery in 1952. Patients often experience fever, headache, muscle pain, joint swelling, and skin rashes. However, the ultrastructural and mechanical properties of CHIKV have not been fully characterized. Thus, this study aims to apply a physical approach to investigate CHIKV′s ultrastructural morphology and mechanical properties, using atomic force microscopy and Raman spectroscopy as the main tools. Using nanomechanical assays of AFM and a gold nanoparticles substrate for Raman signal enhancement, we explored the conformational plasticity, morphology, vibrational signature, and nanomechanical properties of the chikungunya virus, providing new information on its ultrastructure at the nanoscale and offering a novel understanding of the virus’ behavior upon mechanical disruptions besides its molecular composition. 相似文献
109.
Natanael Bolson Pedro Prieto Tadeusz Patzek 《Proceedings of the National Academy of Sciences of the United States of America》2022,119(52)
Given the dire consequences of climate change and the war in Ukraine, decarbonization of electrical power systems around the world must be accomplished, while avoiding recurring blackouts. A good understanding of performance and reliability of different power sources underpins this endeavor. As an energy transition involves different societal sectors, we must adopt a simple and efficient way of communicating the transition’s key indicators. Capacity factor (CF) is a direct measure of the efficacy of a power generation system and of the costs of power produced. Since the year 2000, the explosive expansion of solar PV and wind power made their CFs more reliable. Knowing the long-time average CFs of different electricity sources allows one to calculate directly the nominal capacity required to replace the current fossil fuel mix for electricity generation or expansion to meet future demand. CFs are straightforwardly calculated, but they are rooted in real performance, not in modeling or wishful thinking. Based on the current average CFs, replacing 1 W of fossil electricity generation capacity requires installation of 4 W solar PV or 2 W of wind power. An expansion of the current energy mix requires installing 8.8 W of solar PV or 4.3 W of wind power.Greenhouse gas emissions are the driving force behind climate change (1), which threatens biodiversity (2), food security (3), and cultural diversity (4). The main source of carbon emissions in electricity generation is the current mixture of inputs (5). The current state of affairs demands an energy transition, but numerous challenges emerge (6–8). Such a transition implicates different societies in different ways (9–11), but even the conservative United States wants a decarbonized future (12). Actions toward a sustainable future have been taken at different scales from city (13) to country level (14).The current energy system in place has a rigid structure with a modus operandi of “winner takes all” that hampers the establishment of alternatives (15). Policies can be implemented to overcome the status quo. However, unintended consequences can arise, e.g., carbon pricing policies tend to incentivize optimization of the current energy system instead of the required transformations to achieve a decarbonized one (16). This conclusion is not universally accepted (17–19). It seems, however, that renewables will lead the energy transition and solar photovoltaics will play a key role (20–22).Engaging different players in a society for the energy transition is essential. However, the diversity of stakeholders creates communication barriers, particularly when technical details are transmitted to a broad audience. The war in Ukraine and insufficient natural gas supply in Europe have added painful urgency to clear and truthful communication of the potential pitfalls of any energy transition that boil down to the clear understanding of what the different components of electricity generation systems can and cannot do. Regarding power-generation efficiencies of different sources, the use of CF is an excellent tool to connect with a broad set of audiences.CF is a measure of a power plant efficacy (23). In short, it is an indicator of how fully the power plant is used, relative to its thermodynamic and technological constraints and required spare capacity (24). For all technologies, CFs have typical values for a set time interval and input (a fuel, light, water, or wind).An electrical power plant’s CF gives this plant’s average output relative to its maximum capacity. This could be quite misleading for renewables. If a plant works at 50% of nominal capacity, its CF is 0.5. This does not mean that the plant worked 12 h at full capacity and was off over the remaining 12 h. This plant could be down for different reasons such as repairs, maintenance, refueling, or intermittency for renewables. Despite its limitations, CF is a straightforward indicator that can be easily calculated and predict the amount of electricity that will be obtained on average from a specific nominal capacity installed.Comparing CFs across different technologies can be tricky, mainly when some are well established and mature, while others are at pilot-scale or not fully deployed. In the last two decades, solar PV and wind have been growing exponentially. This explosive growth allows one to obtain reliably their CFs. When a technology is more established, the effects of pilot plants, learning curves (25–28), or optimal sites no longer dominate, giving reliable estimates about that technology’s performance. Field tests are the ultimate answer. Theoretical estimates can differ significantly from the measured ones. Such discrepancies have been presented for wind (29) and concentrated solar power plants (30) (SI Appendix, section 10). Knowing the real value of CFs is fundamental to estimating costs, power production, and the future roles of specific technologies.In this work, we analyze the average CFs of different electricity sources (i.e., biomass, fossil fuels, geothermal heat, water, uranium, solar light, and wind) over the period 2000–2017. Global and regional values are estimated to highlight the differences in the performance of different technologies. These average CF values are then used to calculate the required nominal capacity to be installed in the future for our unavoidable energy transition. 相似文献
110.
Luiz Fernando M Pinheiro Stefano Garzon Jos Mariani Jr. Guy F. Almeida Prado Adriano Mendes Caixeta Breno Oliveira Almeida Pedro Alves Lemos 《Arquivos brasileiros de cardiologia》2022,119(6):931
BackgroundCoronary stenosis can be caused de novo atherosclerosis, in-stent restenosis, and in-stent neoatherosclerosis, three entities that develop from a diverse pathophysiological milieu.ObjectiveThis study aims to investigate, using optical coherence tomography (OCT), whether or not coronary lesions related to these processes differ in their local inflammatory profile.MethodsRetrospective analysis of patients with diagnosed or suspected coronary lesions who had undergone OCT imaging for clinical reasons. Macrophage and intra-plaque neovascularization were assessed by OCT and used as surrogates of local inflammation. A significance level of < 0.05 was adopted as statistically significant.ResultsFrom the 121 lesions, 74 were de novo, 29 were restenosis, and 18 were neoatherosclerosis. Neovascularization was found in 65.8% of de novo, 10.3% in restenosis, and 94.4% in neoatherosclerosis (p<0.01 for all). The volume of neovascularization was different among lesion types (950 vs. 0 vs. 6220, respectively [median values in 1000 x µm3/mm]; p<0.01 for all), which were significantly higher in neoatherosclerosis and lower in restenosis. The presence of macrophages differed among the lesions (95.9% in de novo vs. 6.9% in restenosis vs. 100% in neoatherosclerosis [p<0.01 for all]). Moreover, the intensity of macrophagic infiltration was different among lesion types (2.5 vs. 0.0 vs. 4.5, respectively [median values of macrophage score]; p<0.01 for all), significantly higher in neoatheroscleosis and lower in restenosis.ConclusionWhen compared using coronary OCT, de novo atherosclerosis, in-stent restenosis, and neoatherosclerosis presented markedly different inflammatory phenotypes. 相似文献