全文获取类型
收费全文 | 18368篇 |
免费 | 1051篇 |
国内免费 | 89篇 |
专业分类
耳鼻咽喉 | 318篇 |
儿科学 | 490篇 |
妇产科学 | 318篇 |
基础医学 | 2662篇 |
口腔科学 | 1562篇 |
临床医学 | 1325篇 |
内科学 | 3823篇 |
皮肤病学 | 448篇 |
神经病学 | 1247篇 |
特种医学 | 534篇 |
外科学 | 2144篇 |
综合类 | 94篇 |
一般理论 | 3篇 |
预防医学 | 2042篇 |
眼科学 | 256篇 |
药学 | 1298篇 |
中国医学 | 190篇 |
肿瘤学 | 754篇 |
出版年
2023年 | 192篇 |
2022年 | 407篇 |
2021年 | 727篇 |
2020年 | 453篇 |
2019年 | 585篇 |
2018年 | 729篇 |
2017年 | 510篇 |
2016年 | 550篇 |
2015年 | 628篇 |
2014年 | 813篇 |
2013年 | 1002篇 |
2012年 | 1403篇 |
2011年 | 1612篇 |
2010年 | 860篇 |
2009年 | 673篇 |
2008年 | 1073篇 |
2007年 | 1023篇 |
2006年 | 879篇 |
2005年 | 788篇 |
2004年 | 651篇 |
2003年 | 588篇 |
2002年 | 482篇 |
2001年 | 377篇 |
2000年 | 339篇 |
1999年 | 309篇 |
1998年 | 125篇 |
1997年 | 115篇 |
1996年 | 98篇 |
1995年 | 58篇 |
1994年 | 71篇 |
1993年 | 54篇 |
1992年 | 146篇 |
1991年 | 122篇 |
1990年 | 91篇 |
1989年 | 120篇 |
1988年 | 95篇 |
1987年 | 67篇 |
1986年 | 87篇 |
1985年 | 70篇 |
1984年 | 58篇 |
1983年 | 42篇 |
1982年 | 28篇 |
1981年 | 24篇 |
1980年 | 33篇 |
1979年 | 46篇 |
1978年 | 30篇 |
1977年 | 31篇 |
1976年 | 34篇 |
1975年 | 24篇 |
1969年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Evaluation of anhydride oligomers within polymer microsphere blends and their impact on bioadhesion and drug delivery in vitro 总被引:3,自引:0,他引:3
The effect of the addition of small molecular weight anhydride oligomers to polymer microspheres was evaluated and increased bioadhesion of the composite was demonstrated. Blends of low molecular weight anhydride oligomers with thermoplastic poly(fumaric-co-sebacic anhydride) [p(FASA)] and polycaprolactone were examined. The effects of anhydride oligomers on polymer microsphere degradation, crystallinity, and surface morphology were also explored. The results demonstrated that fumaric anhydride oligomer remained within polymer microspheres for several hours after exposure to phosphate buffer, formed a homogenous crystalline blend, increased bioadhesion as measured on rat intestine, and enhanced drug delivery in vitro as measured by the everted sac technique. 相似文献
82.
Summary. The genome structure of six bacteriophages of Oenococcus oeni was compared. Two distinct groups with no apparent restriction site conservation were defined. In members of the α group
(fOgML34, fOg4029, fOg30 and fOg218) a 7.5 kb region containing the origin of DNA packaging (cos) was highly conserved. Stretches of DNA heterogeneity could also be assigned to particular regions and were mostly evident
in the right area of the genomes. fOg44 and fOgPSU1 (β group) were indistinguishable in the left half of their genomes, including
cos, but were markedly dissimilar in other regions. Strong labelling signals detected in cross-hybridizations involving members
of different groups were confined to fragments centrally located in their physical maps. The attachment site (attP) of fOg44 was assigned to this conserved region. It is suggested that recombination events at this location may have been
important in generating the observed diversity of oenophage genomes.
Accepted October 15, 1997 Received August 11, 1997 相似文献
83.
Coagulase-Negative Staphylococci: Comparison of Phenotypic and Genotypic Oxacillin Susceptibility Tests and Evaluation of the Agar Screening Test by Using Different Concentrations of Oxacillin 下载免费PDF全文
84.
Maria do Carmo Debur Juliano Bordignon Claudia Nunes Duarte dos Santos Luine Rosele Vidal Meri Bordignon Nogueira Sérgio Monteiro de Almeida Sonia Mara Raboni 《Journal of clinical virology》2007,39(1):59-62
BACKGROUND: Human metapneumovirus (hMPV) has been described as an etiologic agent of acute respiratory infections (ARI), mainly in pediatric patients. Viral isolation is difficult and has low sensitivity, and consequently RT-PCR assays are currently used for detection. OBJECTIVES: Detect hMPV in ARI in hospitalized children in Southern Brazil; standardize a RT-PCR for routine hMPV diagnosis; validate a positive control for molecular tests; and perform phylogenetics analyses. STUDY DESIGN: Nasopharyngeal aspirates (NPA) from 156 hospitalized children were studied. A conserved region of the nucleoprotein gene was cloned, characterized and used to standardize an RT-PCR assay. Phylogenetic analyses were performed. Clinical data were obtained from medical records. RESULTS: hMPV was detected in 6.4% of the samples. Dyspnea and wheezing were frequently reported symptoms and the most common diagnoses were bronchiolitis, acute respiratory insufficiency or laryngotracheobronchitis. Nucleotide sequence alignment revealed 97.7% identity with genotype A1 of hMPV. The detection limit of hMPV genomes by RT-PCR in clinical samples was 180 copies/microL. CONCLUSION: This is the first report of the detection and genetic characterization of hMPV infections in children with lower ARI in Southern Brazil. 相似文献
85.
For both practical and methodological reasons, mice have been the most widely employed species for development of transgenic and gene knockin and knockout animals. However, basic behavioral and physiology control and regulatory mechanisms in mice are not well characterized. To broaden our understanding of the processes maintaining body fluid and blood pressure homeostasis in the mouse, the objectives of this study were to evaluate voluntary water, and sodium intakes during the development of renal hypertension and to examine the relationship between hypertension and the quantities of water and salt ingested. In male, C57BL/6J mice, two-kidney, one-clip renal hypertension (2K-1C) was induced, and water and 1.8% NaCl intakes were monitored for 2 weeks. At the end of this period, all animals received arterial catheters for direct recording of blood pressure. The mice that received renal artery clips were sorted into hypertensive (152+/-4 mm Hg) and normotensive (122+/-2 mm Hg) groups and were compared to control (117+/-4 mm Hg) animals that underwent a sham renal clipping procedure. Hypertensive 2K-1C animals had significantly elevated water intake compared to control animals. On most of the postsurgical days, the normotensive 2K-1C animals did not display increased water intake in comparison to the control group. No significant effect was detected for 1.8% saline intake between any of the pairs of groups. In summary, the reduction of blood flow to a single kidney in the 2K-1C model of renal hypertension induces high blood pressure accompanied by sustained hyperdipsia in the mouse. 相似文献
86.
Santos Marília Neves Azeredo Catarina Machado Rinaldi Ana Elisa Madalena 《Maternal and child health journal》2022,26(7):1496-1506
Maternal and Child Health Journal - The aim of this study was to estimate the association between individual and contextual characteristics related to maternal work and exclusive breastfeeding... 相似文献
87.
Ferreira Larissa Bueno Lobo Cecília Viana do Carmo Ariene Silva Souza Rafaela Cristina Vieira e dos Santos Luana Caroline 《Maternal and child health journal》2022,26(7):1464-1472
Maternal and Child Health Journal - Dietary patterns can influence maternal and child health outcomes. The study aims to characterize dietary patterns during pregnancy as well as to identify their... 相似文献
88.
Francisco A. O. Júnior Clara R. Ruiz Yohanna de Oliveira Marco A. V. Barros Alexandre S. Silva Maria S. B. Santos Vinícius J. B. Martins Camille M. Balarini Valdir A. Braga 《Nutrients》2021,13(3)
Exploring an alternative to improve the clinical management of hypertension, we tested the hypothesis that food supplementation with coconut oil (EVCO), alone or combined with aerobic exercise training, could exert an antihypertensive effect (primary outcome) in patients with stage 1 hypertension. Forty-five hypertensive volunteers of both genders participated in a placebo-controlled clinical trial. The volunteers were submitted to 24-hour ambulatory blood pressure monitoring, analysis of blood pressure variability (BPV), measurement of serum malondialdehyde (MDA) and nutritional assessment. Results indicate that EVCO consumption had no adverse effects. The supplementation did not increase the caloric intake compared with placebo, and the dietary constituents were similar between groups, except for the saturated fats, especially lauric acid. The analysis of blood pressure indicated absence of antihypertensive effect of EVCO alone or combined with physical training. Furthermore, no effects on blood pressure variability and oxidative stress were observed in the supplemented hypertensive patients. Thus, despite the results observed in pre-clinical studies, the current clinical study did not provide evidence to support the use of coconut oil as an adjuvant in the management of hypertension in humans. 相似文献
89.
Osvaldo Santos Miodraga Stefanovska-Petkovska Ana Virgolino Ana Cristina Miranda Joana Costa Elisabete Fernandes Susana Cardoso Antnio Vaz Carneiro 《Nutrients》2021,13(3)
Self-management of health requires skills to obtain, process, understand, and use health-related information. Assessment of adolescents’ functional health literacy requires valid, reliable, and low-burden tools. The main objective of this study was to adapt and study the psychometric properties of the Newest Vital Sign for the Portuguese adolescents’ population (NVS-PTeen). Classic psychometric indicators of reliability and validity were combined with item response theory (IRT) analyses in a cross-sectional survey, complemented with a 3-month test-retest assessment. The NVS-PTeen was self-administered to students enrolled in grades 8 to 12 (12 to 17 years old) in a school setting. Overall, 386 students (191 girls) from 16 classes of the same school participated in the study (mean age = 14.5; SD = 1.5). Internal reliability of the NVS-PTeen was α = 0.60. The NVS-PTeen total score was positively and significantly correlated with Portuguese (r = 0.28) and mathematics scores (r = 0.31), school years (r = 0.31), and age (r = 0.19). Similar to the original scale (for the U.S.), the NVS-PTeen is composed of two dimensions, reading-related literacy and numeracy. Temporal reliability is adequate, though with a learning effect. IRT analyses revealed differences in difficulty and discriminative capacity among items, all with adequate outfit and infit values. Results showed that the NVS-PTeen is valid and reliable, sensible to inter-individual educational differences, and adequate for regular screening of functional health literacy in adolescents. 相似文献
90.
Amanda Rodrigues Amorim Adegboye Danilo Dias Santana Pedro Paulo Teixeira dos Santos Paula Guedes Cocate Camila Benaim Maria Beatriz Trindade de Castro Michael Maia Schlüssel Gilberto Kac Berit Lilienthal Heitmann 《Nutrients》2021,13(3)
In this 2 × 2 factorial, outcome-assessor blinded, feasibility randomised trial we explored the effect of a non-pharmaceutical multi-component intervention on periodontal health and metabolic and inflammatory profiles among pregnant women with periodontitis receiving prenatal care in a Brazilian public health centre. 69 pregnant women (gestational age ≤20 weeks, T0) were randomly allocated into four groups: (1) fortified sachet (vitamin D and calcium) and powdered milk plus periodontal therapy during pregnancy (early PT) (n = 17); (2) placebo sachet and powdered milk plus early PT (n = 15); (3) fortified sachet and powdered milk plus late PT (after delivery) (n = 19); (4) placebo sachet and powdered milk plus late PT (n = 18). Third trimester (T1) and 6–8 weeks postpartum (T2) exploratory outcomes included periodontal health (% sites with bleeding on probing (BOP)), glucose, insulin, C-Reactive Protein, serum calcium and vitamin D. The mean BOP was significantly reduced in the early PT groups, while BOP worsened in the late PT groups. No significant effect of fortification on BOP was observed. Changes in glucose levels and variation on birthweight did not differ among groups This feasibility trial provides preliminary evidence for estimating the minimum clinically important differences for selected maternal outcomes. A large-scale trial to evaluate the interventions’ clinical benefits and cost-effectiveness is warranted. 相似文献