首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5465篇
  免费   449篇
  国内免费   21篇
耳鼻咽喉   22篇
儿科学   202篇
妇产科学   92篇
基础医学   827篇
口腔科学   54篇
临床医学   621篇
内科学   1293篇
皮肤病学   92篇
神经病学   535篇
特种医学   130篇
外科学   610篇
综合类   55篇
一般理论   1篇
预防医学   607篇
眼科学   81篇
药学   409篇
中国医学   15篇
肿瘤学   289篇
  2024年   12篇
  2023年   83篇
  2022年   114篇
  2021年   230篇
  2020年   145篇
  2019年   206篇
  2018年   204篇
  2017年   148篇
  2016年   179篇
  2015年   190篇
  2014年   221篇
  2013年   283篇
  2012年   423篇
  2011年   450篇
  2010年   235篇
  2009年   197篇
  2008年   368篇
  2007年   325篇
  2006年   374篇
  2005年   330篇
  2004年   302篇
  2003年   270篇
  2002年   193篇
  2001年   37篇
  2000年   24篇
  1999年   43篇
  1998年   44篇
  1997年   38篇
  1996年   23篇
  1995年   34篇
  1994年   15篇
  1993年   12篇
  1992年   16篇
  1991年   15篇
  1990年   20篇
  1989年   19篇
  1988年   9篇
  1987年   11篇
  1986年   9篇
  1985年   8篇
  1984年   13篇
  1983年   9篇
  1982年   8篇
  1978年   5篇
  1977年   3篇
  1976年   3篇
  1975年   5篇
  1972年   4篇
  1969年   3篇
  1967年   3篇
排序方式: 共有5935条查询结果,搜索用时 31 毫秒
101.
102.
Forty common swifts (Apus apus), synanthropic birds living in an urban environment closely with humans and other animals, were hospitalized in the public veterinary hospital of the Regional Reference Center of Urban Veterinary Hygiene located in Naples, Campania Region, Italy. Each bird was sampled for bacteriological analyses. Out of 40 common swifts examined, eight were found positive for Salmonella enterica serovar Infantis although no sign of salmonellosis (e.g. diarrhoea) was shown. This is believed to be the first report of Salmonella spp. infection in common swifts. Our results suggest this avian species as a novel potential reservoir for one of most important Salmonella serovars.  相似文献   
103.
In the present study we aimed to evaluate the impact of langerin (CD207)+ dendritic cells (DCs) and FOXP3+ Treg cells in the intestinal mucosa of children with celiac disease (CD) and atopic dermatitis (AD) in comparison to children with functional gastrointestinal disorders (FGD). Seventy‐five children (37 male, mean age 8.4 ± 4.8 years), who randomly underwent small bowel biopsy, were studied. The CD was diagnosed in 14 children, including five persons with concomitant AD (all positive for anti‐tissue transglutaminase IgA antibodies and with small bowel atrophy). Normal small bowel mucosa was found in eight patients with AD and in 53 patients with FGD. The sera of all patients were tested for total and specific IgE antibodies to food allergen panels. Staining for CD11c+, langerin (CD207+) DCs, CD4+, and FOXP3+ Treg cells was performed on paraffin‐embedded sections of bioptates using immunohistochemistry. The density of CD11c+ DCs, CD4+, and FOXP3+ Treg cells was higher in the CD patients compared to the AD and FGD patients (p = 0.02; p = 0.001). In AD, significantly higher density of CD11c+ DCs was detected in patients positive for specific IgE to food allergen panels (p = 0.02). The FGD patients with elevated total IgE had increased density of langerin (CD207)+ DCs compared to the patients with normal total IgE levels (p = 0.01). The increased density of FOXP3+ Treg cells, CD4+, cells and CD11c+ DCs was associated with CD but not with AD. The elevated level of total IgE or specific IgE to food allergens was associated with more pronounced expression of DCs, indicating a possible link between the presence of these cells in small bowel mucosa with elevated level of serum IgE.  相似文献   
104.
This clinical study aimed to determine whether periodontal disease is associated with expression of developmental endothelial locus‐1 (Del‐1) and pentraxin‐3 (PTX‐3), endogenous inhibitors of leukocyte extravasation in humans. Expression of DEL1, PTX3, interleukin‐17A (IL17A), and lymphocyte function‐associated antigen‐1 (LFA1) was determined, using RT‐PCR and melting curve analysis, in biopsies of gingival tissues from 95 patients: 42 with moderate periodontitis; 40 with severe periodontitis; and 13 healthy controls. Relative expression of DEL1 and PTX3 was statistically significantly weaker in patients with periodontitis than in the control subjects. On the contrary, both IL17A and LFA1 showed statistically significant stronger expression in patients with periodontitis than in healthy controls. Correlation analysis, performed using Spearman's test, showed that expression of DEL1 was statistically significantly linked to periodontitis (ρ = ?0.103) and to age (ρ = ?0.134), but not to the gender of the patient, and that expression of PTX3 was significantly correlated with periodontitis (ρ = ?0.354). Expression of neutrophil extravasation inhibitors DEL1 and PTX3 show significant, but weak, association with the clinical manifestation of chronic periodontitis.  相似文献   
105.
Background: The vertebrate inner ear comprises mineralized elements, namely the otoliths (fishes) or the otoconia (mammals). These elements serve vestibular and auditory functions. The formation of otoconia and otoliths is described as a stepwise process, and in fish, it is generally divided into an aggregation of the otolith primordia from precursor particles and then a growth process that continues throughout life. Results: This study was undertaken to investigate the complex transition between these two steps. Therefore, we investigated the developmental profiles of several inner ear structural and calcium-binding proteins during the complete embryonic and larval development of the cichlid fish Oreochromis mossambicus in parallel with the morphology of inner ear and especially otoliths. We show that the formation of otoliths is a highly regulated temporal and spatial process which takes place throughout embryonic and larval development. Conclusions: Based on our data we defined eight phases of otolith differentiation from the primordia to the mature otolith.  相似文献   
106.
Introduction: Multi‐disease community health campaigns can be effective for population‐wide HIV testing in a research setting (SEARCH: NCT01864603). We sought to evaluate feasibility and uptake of a community‐led health campaign (CLHC) planned and implemented by village leaders and local clinic workers in Uganda. Methods: Over five months in 2014, locally elected village leaders and Ministry of Health (MoH) clinic staff in a rural parish in Uganda planned a census followed by a CLHC, after training by two SEARCH trial consultants and by leaders from a neighbouring parish that had previously participated in a SEARCH health campaign. We defined feasibility as: (1) elected leaders’ participation in training and implementation of pre‐campaign census and mobilization activities; (2) implementation of all campaign activities by MoH‐funded, local clinic staff; and (3) community participation in the campaign, including point‐of‐care screening for HIV, malaria, hypertension and diabetes, and same‐day referral for male circumcision and family planning (FP). Costing of all salaries and supplies was conducted. Results: Elected leaders from all eight villages in the parish participated in CLHC training. They and local clinic staff met monthly to select and plan CLHC services. Village leaders then leveraged existing volunteer health teams to perform a door‐to‐door census, enumerating 5,202 parish residents over 2 weeks. 2,753 (53%) residents participated in the 6‐day CLHC. Of 1,584 adult participants, 1,474 (93%) tested for HIV: 105/1,474 (7.1%) tested HIV positive. 27% (751/2,753) of participants reported fever and underwent malaria rapid diagnostic testing: 5.3% (40/751) tested positive. Among adults screened, 19% (271/1,452) were hypertensive, and 3% (18/637) had a random blood sugar >11.1 mmol/L. Of 805 men and boys (>10 years), 91 (11%) accepted same‐day clinic referral and underwent medical circumcision. Of 900 women offered same‐day long‐term FP referrals, 25 accepted. The CLHC cost, including census, mobilization and testing services, was $23,597 ($8.57/participant). C onclusions: Elected village leaders successfully planned and conducted a 6‐day multi‐disease health campaign with service provision by local clinic staff that reached over half of a rural Ugandan community. These data suggest it is feasible for local leaders and clinics to adopt a multi‐disease health campaign approach to scale‐up HIV testing in rural Africa.  相似文献   
107.
Dense deposit disease (DDD) is a severe renal disease characterized by accumulation of electron-dense material in the mesangium and glomerular basement membrane. Previously, DDD has been associated with deficiency of factor H (fH), a plasma regulator of the alternative pathway (AP) of complement activation, and studies in animal models have linked pathogenesis to the massive complement factor 3 (C3) activation caused by this deficiency. Here, we identified a unique DDD pedigree that associates disease with a mutation in the C3 gene. Mutant C3923ΔDG, which lacks 2 amino acids, could not be cleaved to C3b by the AP C3-convertase and was therefore the predominant circulating C3 protein in the patients. However, upon activation to C3b by proteases, or to C3(H2O) by spontaneous thioester hydrolysis, C3923ΔDG generated an active AP C3-convertase that was regulated normally by decay accelerating factor (DAF) but was resistant to decay by fH. Moreover, activated C3b923ΔDG and C3(H2O)923ΔDG were resistant to proteolysis by factor I (fI) in the presence of fH, but were efficiently inactivated in the presence of membrane cofactor protein (MCP). These characteristics cause a fluid phase–restricted AP dysregulation in the patients that continuously activated and consumed C3 produced by the normal C3 allele. These findings expose structural requirements in C3 that are critical for recognition of the substrate C3 by the AP C3-convertase and for the regulatory activities of fH, DAF, and MCP, all of which have implications for therapeutic developments.  相似文献   
108.
109.
Beta-catenin is temporally regulated during normal liver development   总被引:9,自引:0,他引:9  
BACKGROUND & AIMS: beta-Catenin, a key component of the Wnt pathway, plays an important role in unregulated liver growth in liver tumors, in regulated growth during liver regeneration, and in ex vivo embryonic liver cultures. METHODS: We used developing livers from several stages of gestational development to examine beta-catenin expression, protein-protein interactions, localization, and regulation in prenatal and postnatal livers. RESULTS: Microarray, Northern, and protein analyses showed peak expression of beta-catenin during early liver development at Embryonic day 10 (E10)-E12, followed by a decrease and a complete loss of normal beta-catenin (97-kilodalton species) after E16 through the remaining prenatal period. At the early stages, beta-catenin localized to the cytoplasm and nuclei of resident cells in addition to its normal membranous localization, which was seen at all later stages and in adult liver. Decreases in beta-catenin levels at E14 onward coincided with its decreased gene expression and increased degradation, as seen by an increase in serine 45/threonine 41-phosphorylated beta-catenin and its other negative regulators, such as axin, adenomatous polyposis coli gene product (APC), and glycogen synthase kinase-3 beta. Finally, we showed an intact association of E-cadherin and beta-catenin despite the loss of beta-catenin at E16-E18, owing to the presence of membrane-associated smaller-molecular-weight beta-catenin species. CONCLUSIONS: We also identified a stage-specific expression and regulation of beta-catenin during liver development that might be crucial for physiological liver development. Nuclear and cytoplasmic beta-catenin corresponded to cell proliferation in liver development. Finally, a smaller-molecular-weight species of beta-catenin might be maintaining normal interactions at the membrane.  相似文献   
110.
BACKGROUND: Cytosolic aldehyde dehydrogenase, or ALDH1A1, functions in ethanol detoxification, metabolism of neurotransmitters, and synthesis of retinoic acid. Because the promoter region of a gene can influence gene expression, the ALDH1A1 promoter regions were studied to identify polymorphism, to assess their functional significance, and to determine whether they were associated with a risk for developing alcoholism. METHODS: Sequence analysis was performed in the promoter region by using Asian, Caucasian, and African American subjects. The resulting polymorphisms were assessed for frequency in Asian, Caucasian, Jewish, and African American populations and tested for associations with alcohol dependence in Asian and African American populations of alcoholics and controls. The functional significance of each polymorphism was determined through in vitro expression analysis by using HeLa and HepG2 cells. RESULTS: Two polymorphisms, a 17 base pair (bp) deletion (-416/-432) and a 3 bp insertion (-524), were discovered in the ALDH1A1 promoter region: ALDH1A1*2 and ALDH1A1*3, respectively. ALDH1A1*2 was observed at frequencies of 0.035, 0.023, 0.023, and 0.012 in the Asian, Caucasian, Jewish, and African American populations, respectively. ALDH1A1*3 was observed only in the African American population, at a frequency of 0.029. By using HeLa and HepG2 cells for in vitro expression, the activity of the luciferase reporter gene was significantly decreased after transient transfection of ALDH1A1*3-luciferase compared with the wild-type construct ALDH1A1*1-luciferase. In an African American population, a trend for higher frequencies of the ALDH1A1*2 and ALDH1A1*3 alleles was observed in a population of alcoholics (p = 0.03 and f = 0.12, respectively) compared with the control population. CONCLUSIONS: ALDH1A1*2 and ALDH1A1*3 may influence ALDH1A1 gene expression. Both ALDH1A1*2 and ALDH1A1*3 produce a trend in an African American population that may be indicative of an association with alcoholism; however, more samples are required to validate this observation. The underlying mechanisms contributing to these trends are still unknown.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号