全文获取类型
收费全文 | 1987278篇 |
免费 | 138969篇 |
国内免费 | 3494篇 |
专业分类
耳鼻咽喉 | 29143篇 |
儿科学 | 62583篇 |
妇产科学 | 58181篇 |
基础医学 | 287372篇 |
口腔科学 | 56644篇 |
临床医学 | 170624篇 |
内科学 | 381912篇 |
皮肤病学 | 40480篇 |
神经病学 | 156641篇 |
特种医学 | 77755篇 |
外国民族医学 | 526篇 |
外科学 | 306998篇 |
综合类 | 47150篇 |
现状与发展 | 3篇 |
一般理论 | 540篇 |
预防医学 | 148997篇 |
眼科学 | 46356篇 |
药学 | 150184篇 |
33篇 | |
中国医学 | 3774篇 |
肿瘤学 | 103845篇 |
出版年
2018年 | 17981篇 |
2015年 | 18005篇 |
2014年 | 25209篇 |
2013年 | 38535篇 |
2012年 | 52556篇 |
2011年 | 55934篇 |
2010年 | 32853篇 |
2009年 | 30958篇 |
2008年 | 53761篇 |
2007年 | 58435篇 |
2006年 | 58694篇 |
2005年 | 57881篇 |
2004年 | 56047篇 |
2003年 | 54238篇 |
2002年 | 52950篇 |
2001年 | 85084篇 |
2000年 | 87301篇 |
1999年 | 74257篇 |
1998年 | 21769篇 |
1997年 | 19714篇 |
1996年 | 19762篇 |
1995年 | 18688篇 |
1994年 | 17795篇 |
1993年 | 16523篇 |
1992年 | 61396篇 |
1991年 | 60468篇 |
1990年 | 59512篇 |
1989年 | 57773篇 |
1988年 | 53905篇 |
1987年 | 53017篇 |
1986年 | 50616篇 |
1985年 | 48576篇 |
1984年 | 36905篇 |
1983年 | 31937篇 |
1982年 | 19516篇 |
1981年 | 17593篇 |
1980年 | 16363篇 |
1979年 | 36003篇 |
1978年 | 25632篇 |
1977年 | 21848篇 |
1976年 | 20481篇 |
1975年 | 22331篇 |
1974年 | 26958篇 |
1973年 | 26035篇 |
1972年 | 24722篇 |
1971年 | 22934篇 |
1970年 | 21620篇 |
1969年 | 20891篇 |
1968年 | 19362篇 |
1967年 | 17370篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Nandita Perumal Daniel E. Roth Johnna Perdrizet Aluísio J. D. Barros Iná S. Santos Alicia Matijasevich Diego G. Bassani 《Emerging themes in epidemiology》2018,15(1):3
Background
Postmenstrual and/or gestational age-corrected age (CA) is required to apply child growth standards to children born preterm (< 37 weeks gestational age). Yet, CA is rarely used in epidemiologic studies in low- and middle-income countries (LMICs), which may bias population estimates of childhood undernutrition. To evaluate the effect of accounting for GA in the application of growth standards, we used GA-specific standards at birth (INTERGROWTH-21st newborn size standards) in conjunction with CA for preterm-born children in the application of World Health Organization Child Growth Standards postnatally (referred to as ‘CA’ strategy) versus postnatal age for all children, to estimate mean length-for-age (LAZ) and weight-for-age (WAZ) z scores at 0, 3, 12, 24, and 48-months of age in the 2004 Pelotas (Brazil) Birth Cohort.Results
At birth (n = 4066), mean LAZ was higher and the prevalence of stunting (LAZ < ?2) was lower using CA versus postnatal age (mean ± SD): ? 0.36 ± 1.19 versus ? 0.67 ± 1.32; and 8.3 versus 11.6%, respectively. Odds ratio (OR) and population attributable risk (PAR) of stunting due to preterm birth were attenuated and changed inferences using CA versus postnatal age at birth [OR, 95% confidence interval (CI): 1.32 (95% CI 0.95, 1.82) vs 14.7 (95% CI 11.7, 18.4); PAR 3.1 vs 42.9%]; differences in inferences persisted at 3-months. At 12, 24, and 48-months, preterm birth was associated with stunting, but ORs/PARs remained attenuated using CA compared to postnatal age. Findings were similar for weight-for-age z scores.Conclusions
Population-based epidemiologic studies in LMICs in which GA is unused or unavailable may overestimate the prevalence of early childhood undernutrition and inflate the fraction of undernutrition attributable to preterm birth.72.
Oğuzhan Bol Serhat Koyuncu Nurullah Günay 《Journal of occupational medicine and toxicology (London, England)》2018,13(1):35
Background
Carbon monoxide (CO) is formed as a result of the incomplete burning of hydrocarbon-containing fuels such as natural gas, coal, liquid petroleum gas, and wood. CO is a colorless, odorless, and poisonous gas that produces various acute and chronic effects in CO-exposed people. In this study, we aimed to measure CO levels in auto care repairmen with chronic CO-related illnesses using a serial, non-invasive method.A prospective cohort study.Methods
A total of 99 people from six different auto-repair services were included in the study. Carboxyhemoglobin (COHb) levels were measured at four different times with 2-hour intervals starting at 08:00 AM. Data concerning employees’ ages, working hours, smoking statuses, and types of home heating fuel were collected. A control group of 100 cases was created based on this data. The measurements were done on the control group in the morning with a Masimo Rad-57 CO-oximeter.Results
The highest mean (± SD) COHb value was 7.04%?±?3.32% after the third measurement. The mean value for the control group was 1.61%?±?1.43%. A statistically significant difference between the groups was found for each value.Discussion
We determined that the risk of being affected by CO is high in buildings in which the auto services were located. The effects of chronic or prolonged exposure to low amounts of CO were found to be ambiguous. However, in some studies, it was found that low-grade CO exposure could lead to coronary artery disease and some neurological complications. Therefore, it is necessary to be careful about the health of employees who have been exposed to CO.Conclusions
We concluded that there is a need for more detailed studies concerning chronic CO poisoning. Also, in workplaces in which there is high exposure to CO, proper workplace safety measures should be taken to reduce this gas’s harmful effects to employees.73.
74.
Purpose
This article describes preclinical development of cell-based medicinal products for European markets and discusses European regulatory mechanisms open to developers to aid successful product development. Cell-based medicinal products are diverse, including cells that are autologous or allogeneic, have been genetically modified, or not, or expanded ex vivo, and applied systemically or to an anatomical site different to that of their origin; comments applicable to one product may not be applicable to others, so bespoke development is needed, for all elements - quality, preclinical and clinical.Methods
After establishing how the product is produced, proof of potential for therapeutic efficacy, and then safety, of the product need to be determined. This includes understanding biodistribution, persistence and toxicity, including potential for malignant transformation. These elements need to be considered in the context of the intended clinical development.Results
This article describes regulatory mechanisms available to developers to support product development that aim to resolve scientific issues prior to marketing authorization application, to enable patients to have faster access to the product than would otherwise be the case.Conclusions
Developers are encouraged to be aware of both the scientific issues and regulatory mechanisms to ensure patients can be supplied with these products.75.
76.
A. Sobke O. Makarewicz M. Baier C. Bär W. Pfister S.G. Gatermann M.W. Pletz C. Forstner 《International journal of antimicrobial agents》2018,51(2):213-220
The spread of antimicrobial resistance challenges the empirical treatment of urinary tract infections (UTIs). Among others, nitrofurantoin is recommended for first-line treatment, but acceptance among clinicians is limited due to chronic nitrofurantoin-induced lung toxicity and insufficient coverage of Enterobacteriaceae other than Escherichia coli. Nitroxoline appears to be an alternative to nitrofurantoin owing to its favourable safety profile, however data on its current in vitro susceptibility are sparse. In this study, susceptibility to nitroxoline was tested against 3012 urinary clinical isolates (including multidrug-resistant bacteria and Candida spp.) by disk diffusion test and/or broth microdilution. At least 91% of all Gram-negatives (n?=?2000), Gram-positives (n?=?403) and yeasts (n?=?132) had inhibition zone diameters for nitroxoline ≥18?mm. Except for Pseudomonas aeruginosa, nitroxoline MIC90 values were ≤16?mg/L and were 2- to >16-fold lower compared with nitrofurantoin. In extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae and methicillin-resistant Staphylococcus aureus (MRSA), MIC90 values of nitroxoline were two-fold higher compared with non-ESBL-producing enterobacteria and methicillin-susceptible S. aureus (MSSA). The in vitro efficacies of nitroxoline and nitrofurantoin against ATCC strains of E. coli, Enterococcus faecalis and Proteus mirabilis were compared by time–kill curves in Mueller–Hinton broth and artificial urine. Nitroxoline was non-inferior against E. coli, P. mirabilis and E. faecalis in artificial urine. In conclusion, nitroxoline showed a broad antimicrobial spectrum, with inhibition zone diameters and MICs of nitroxoline well below the EUCAST breakpoint for E. coli for most organisms, and thus may also be a target for therapy of uncomplicated UTIs. 相似文献
77.
78.
Anne Beck Patricia Pelz Robert C. Lorenz Katrin Charlet Olga Geisel Andreas Heinz Torsten Wüstenberg Christian A. Müller 《European neuropsychopharmacology》2018,28(11):1206-1216
Increased functional brain response towards alcohol-associated stimuli is a neural hallmark of alcohol dependence and a promising target for pharmacotherapy. For the first time, we assessed the effects of individually titrated high-dose baclofen on cue reactivity and functional connectivity in alcohol-dependent (AD) patients in a randomized controlled trial (RCT).We investigated 23 recently detoxified AD patients and 23 matched healthy controls (HC) with a cue reactivity functional magnetic resonance imaging task. Patients were further scanned at baseline without medication and during treatment with high-dose baclofen/placebo (30–270 mg/d). Analyses were conducted for alcohol cue-elicited brain response, alcohol cue-modulated and stimulus-independent functional connectivity with left ventral tegmental area (VTA) as seed region.At baseline, AD patients (N?=?23) showed increased cue-elicited brain activation in the ventral striatum (VS) compared to HC (N?=?23), which was decreased at the second scanning session compared to baseline. Patients receiving baclofen (N?=?10) showed a significant stronger decrease in cue-elicited brain activation in left orbitofrontal cortex (OFC), bilateral amygdala and left VTA than patients receiving placebo (N?=?13). Treatment with baclofen further led to a decrease in alcohol cue-modulated functional connectivity between left VTA and left anterior cingulate cortex (ACC) as well as left medial prefrontal cortex (MPFC). Regarding clinical outcome, significantly more patients of the baclofen group remained abstinent during the high-dose period.Baclofen specifically decreased cue-elicited brain responses in areas known to be involved in the processing of salient (appetitive and aversive) stimuli. Treatment with high-dose baclofen seems to provide a pharmacological relief of this neural “warning signal” evoked by alcohol-related cues, thereby possibly supporting patients in remaining abstinent.Trial Registration Identifier of the main trial [BACLAD study] at clinicaltrials.gov: NCT01266655. 相似文献
79.
Yuliya V. Yushkova Elena I. Chernyak Yuriy V. Gatilov Vladimir G. Vasilev Sergey V. Morozov Igor A. Grigorev 《Saudi Pharmaceutical Journal》2018,26(1):84-92
The interaction of trolox with ammonia, alkylamines of different classes, and amino derivatives of heterocyclic compounds, including nitroxyl radicals and alkaloids, led to the production of ammonium salts called ion conjugates (ICs). Five ICs were characterised by X-ray diffraction. This is the first time a wide range of ICs were made from trolox with amines, and ESI-MS data demonstrated they have the potential to generate pseudomolecular [(A?B+)?+?H]+ ions. For all obtained trolox ICs, a significant increase (1–3 orders of magnitude) in water solubility was achieved while retaining high antioxidant activity. ICs synthesised from two biologically active fragments may be used to create polyfunctional agents with varying solubility and bioavailability. 相似文献
80.
Birke J. Benedikter Emiel F. M. Wouters Paul H. M. Savelkoul Gernot G. U. Rohde 《Journal of toxicology and environmental health. Part B, Critical reviews》2018,21(3):142-160
Extracellular vesicles (EV) are secreted signaling entities that enhance various pathological processes when released in response to cellular stresses. Respiratory exposures such as cigarette smoke and air pollution exert cellular stresses and are associated with an increased risk of several chronic diseases. The aim of this review was to examine the evidence that modifications in EV contribute to respiratory exposure-associated diseases. Publications were searched using PubMed and Google Scholar with the search terms (cigarette smoke OR tobacco smoke OR air pollution OR particulate matter) AND (extracellular vesicles OR exosomes OR microvesicles OR microparticles OR ectosomes). All original research articles were included and reviewed. Fifty articles were identified, most of which investigated the effect of respiratory exposures on EV release in vitro (25) and/or on circulating EV in human plasma (24). The majority of studies based their main observations on the relatively insensitive scatter-based flow cytometry of EV (29). EV induced by respiratory exposures were found to modulate inflammation (19), thrombosis (13), endothelial dysfunction (11), tissue remodeling (6), and angiogenesis (3). By influencing these processes, EV may play a key role in the development of cardiovascular diseases and chronic obstructive pulmonary disease and possibly lung cancer and allergic asthma. The current findings warrant additional research with improved methodologies to evaluate the contribution of respiratory exposure-induced EV to disease etiology, as well as their potential as biomarkers of exposure or risk and as novel targets for preventive or therapeutic strategies. 相似文献