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   3783篇
  免费   246篇
  国内免费   24篇
耳鼻咽喉   15篇
儿科学   228篇
妇产科学   69篇
基础医学   469篇
口腔科学   115篇
临床医学   375篇
内科学   881篇
皮肤病学   62篇
神经病学   211篇
特种医学   530篇
外科学   300篇
综合类   40篇
一般理论   1篇
预防医学   239篇
眼科学   38篇
药学   210篇
中国医学   11篇
肿瘤学   259篇
  2022年   20篇
  2021年   73篇
  2020年   38篇
  2019年   73篇
  2018年   89篇
  2017年   57篇
  2016年   62篇
  2015年   78篇
  2014年   101篇
  2013年   158篇
  2012年   122篇
  2011年   132篇
  2010年   135篇
  2009年   118篇
  2008年   156篇
  2007年   132篇
  2006年   137篇
  2005年   129篇
  2004年   102篇
  2003年   103篇
  2002年   82篇
  2001年   79篇
  2000年   96篇
  1999年   86篇
  1998年   155篇
  1997年   129篇
  1996年   151篇
  1995年   102篇
  1994年   86篇
  1993年   92篇
  1992年   46篇
  1991年   62篇
  1990年   40篇
  1989年   91篇
  1988年   73篇
  1987年   79篇
  1986年   78篇
  1985年   72篇
  1984年   42篇
  1983年   48篇
  1982年   42篇
  1981年   29篇
  1980年   47篇
  1979年   25篇
  1978年   24篇
  1977年   23篇
  1976年   32篇
  1975年   27篇
  1966年   11篇
  1965年   11篇
排序方式: 共有4053条查询结果,搜索用时 562 毫秒
991.
Although recent studies have suggested that tooth loss is positively related to the risk of gastric non-cardia cancer, the underlying oral health conditions potentially responsible for the association remain unknown. We investigated whether clinical and behavioral measures of oral health are associated with the risk of gastric precancerous lesions. We conducted a cross-sectional study of 131 patients undergoing upper gastrointestinal endoscopy. Cases were defined as those with gastric precancerous lesions including intestinal metaplasia or chronic atrophic gastritis on the basis of standard biopsy review. A validated structured questionnaire was administered to obtain information on oral health behaviors. A comprehensive clinical oral health examination was performed on a subset of 91 patients to evaluate for periodontal disease and dental caries experience. A total of 41 (31%) cases of gastric precancerous lesions were identified. Compared with non-cases, cases were significantly more likely to not floss their teeth [odds ratio (OR) = 2.89, 95% confidence interval (CI): 1.09-7.64], adjusting for age, sex, race, body mass index, smoking status, educational attainment and Helicobacter pylori status in serum. Among participants who completed the oral examination, cases (n = 28) were more likely to have a higher percentage of sites with gingival bleeding than non-cases [OR = 2.63, 95% CI: 1.37-5.05 for a standard deviation increase in bleeding sites (equivalent to 19.7%)], independent of potential confounders. Our findings demonstrate that specific oral health conditions and behaviors such as gingival bleeding and tooth flossing are associated with gastric precancerous lesions.  相似文献   
992.
993.
African-American female adolescents who engaged in vaginal sex only (= 272) were compared to adolescents who engaged in two types (vaginal plus oral or anal; N = 295) and three types (vaginal, oral and anal; N = 144) on a constellation of other sexual risk behaviors (SRBs) and on sexually transmitted infections (STIs). Adjusted contrasts among groups revealed that adolescents who engaged in two and in three types of sex as compared to those who engaged in vaginal sex only were more likely to engage in six of the seven SRBs, but were just as likely to have a STI. One SRB, having ≥ 4 lifetime sex partners, was in turn associated with STI. Two-way interactions indicated that having a casual sex partner and having multiple sex partners in the last 60 days increased the likelihood of STI, but only for adolescents who engaged in all three types.  相似文献   
994.
995.
996.
神经病理性痛大鼠脊髓背角星形胶质细胞NF-κB活性的变化   总被引:1,自引:1,他引:0  
目的 观察神经病理性痛大鼠脊髓背角星形胶质细胞NF-κB活性的变化,以探讨脊髓星形胶质细胞调控神经病理性痛时胞内可能的信号转导通路机制.方法 雄性SD大鼠16只,月龄2~3 71,体重220~280 g,随机分为2组(n=8):假手术组(S组)和神经病理性痛组(CCI组).CCI组采用慢性压迫性损伤法制备大鼠慢性神经病理性痛模型,S组仅暴露坐骨神经.分别于术前1 d和术后7 d测定机械痛阈和热痛阈,术后第7天测定痛阈后处死大鼠,取脊髓,记录腰段脊髓背角星形胶质细胞核内NF-κBp65的免疫反应阳性细胞数.结果 与术前1 d比较,CCI组大鼠术后7 d机械痛阈和热痛阈降低(P<0.05).与S组比较,CCI组大鼠术后7 d机械痛阈和热痛阈降低,术侧脊髓背角星形胶质细胞NF-κBp65免疫阳性细胞数增多(P<0.05).结论 脊髓背角星形胶质细胞参与大鼠神经病理性痛的调控,其机制可能与NF-κB信号转导通路有关.  相似文献   
997.
Articular cartilage damage in the young adult knee, if left untreated, it may proceed to degenerative osteoarthritis and is a serious cause of disability and loss of function. Surgical cartilage repair of an osteochondral defect can give the patient significant relief from symptoms and preserve the functional life of the joint. Several techniques including bone marrow stimulation, cartilage tissue based therapy, cartilage cell seeded therapies and osteotomies have been described in the literature with varying results. Established techniques rely mainly on the formation of fibro-cartilage, which has been shown to degenerate over time due to shear forces. The implantation of autologous cultured chondrocytes into an osteochondral defect, may replace damaged cartilage with hyaline or hyaline-like cartilage. This clinical review assesses current surgical techniques and makes recommendations on the most appropriate method of cartilage repair when managing symptomatic osteochondral defects of the knee. We also discuss the experience with the technique of autologous chondrocyte implantation at our institution over the past 11 years.  相似文献   
998.
Background: The aim of this study was to evaluate the preventive effect in vitro of experimental gel containing iron and/or fluoride on the erosion of bovine enamel. Methods: To standardize the blocks (n = 80), specimens (4 × 4 mm) were previously selected to measure the initial microhardness. The blocks were randomly allocated into four groups of 20 samples each: C (control, placebo gel); F (fluoride gel, 1.23% NaF); Fe (iron gel, 10 mmol/L FeSO4) and F + Fe (fluoride + iron gel). The gels were applied and removed after 1 minute. The blocks were then submitted to six alternating remineralization and demineralization cycles. The beverage Coca‐Cola® (10 minutes, 30 mL) was used for demineralization, and artificial saliva (1 hour) for remineralization. The effect of erosion was measured by wear analysis (profilometry). Data were analysed by ANOVA and the Tukey test for individual comparisons (p <0.05). Results: The mean wear (± SD, μm) was C: 0.94 ± 0.22; F: 0.55 ± 0.12; Fe: 0.49 ± 0.11 and F + Fe: 0.55 ± 0.13. When the experimental gels were used, there was statistically significant reduction in enamel wear in comparison with the control (p <0.001). However, the experimental gels did not differ significantly among them. Conclusions: The gels containing iron with or without fluoride are capable of interfering with the dissolution dental enamel in the presence of erosive challenge.  相似文献   
999.
Vanderploeg RD, Schwab K, Walker WC, Fraser JA, Sigford BJ, Date ES, Scott SG, Curtiss G, Salazar AM, Warden DL, for the Defense and Veterans Brain Injury Center Study Group. Rehabilitation of traumatic brain injury in active duty military personnel and veterans: Defense and Veterans Brain Injury Center randomized controlled trial of two rehabilitation approaches.

Objectives

To determine the relative efficacy of 2 different acute traumatic brain injury (TBI) rehabilitation approaches: cognitive didactic versus functional-experiential, and secondarily to determine relative efficacy for different patient subpopulations.

Design

Randomized, controlled, intent-to-treat trial comparing 2 alternative TBI treatment approaches.

Setting

Four Veterans Administration acute inpatient TBI rehabilitation programs.

Participants

Adult veterans or active duty military service members (N=360) with moderate to severe TBI.

Interventions

One and a half to 2.5 hours of protocol-specific cognitive-didactic versus functional-experiential rehabilitation therapy integrated into interdisciplinary acute Commission for Accreditation of Rehabilitation Facilities–accredited inpatient TBI rehabilitation programs with another 2 to 2.5 hours daily of occupational and physical therapy. Duration of protocol treatment varied from 20 to 60 days depending on the clinical needs and progress of each participant.

Main Outcome Measures

The 2 primary outcome measures were functional independence in living and return to work and/or school assessed by independent evaluators at 1-year follow-up. Secondary outcome measures consisted of the FIM, Disability Rating Scale score, and items from the Present State Exam, Apathy Evaluation Scale, and Neurobehavioral Rating Scale.

Results

The cognitive-didactic and functional-experiential treatments did not result in overall group differences in the broad 1-year primary outcomes. However, analysis of secondary outcomes found differentially better immediate posttreatment cognitive function (mean ± SD cognitive FIM) in participants randomized to cognitive-didactic treatment (27.3±6.2) than to functional treatment (25.6±6.0, t332=2.56, P=.01). Exploratory subgroup analyses found that younger participants in the cognitive arm had a higher rate of returning to work or school than younger patients in the functional arm, whereas participants older than 30 years and those with more years of education in the functional arm had higher rates of independent living status at 1 year posttreatment than similar patients in the cognitive arm.

Conclusions

Results from this large multicenter randomized controlled trial comparing cognitive-didactic and functional-experiential approaches to brain injury rehabilitation indicated improved but similar long-term global functional outcome. Participants in the cognitive treatment arm achieved better short-term functional cognitive performance than patients in the functional treatment arm. The current increase in war-related brain injuries provides added urgency for rigorous study of rehabilitation treatments. (http://ClinicalTrials.gov ID# NCT00540020.)  相似文献   
1000.
Platelet inhibition as measured by vasodilator-stimulated phosphoprotein (VASP) and light transmission aggregometry (LTA) have shown concordance following dosing of clopidogrel. No reports have directly compared the VASP assay and LTA at the levels of P2Y(12) blockade after loading doses (LDs) of prasugrel or high dose clopidogrel (600 and 900 mg). The aim was to compare the VASP assay and LTA during the loading dose phase of a comparative study of prasugrel and clopidogrel. Prasugrel 60 mg LD/10 mg maintenance dose (MD) and clopidogrel 300 mg/75 mg and 600 mg/75 mg LD/MD regimens were compared in a 3-way crossover study in 41 healthy, aspirin-free subjects. Each LD was followed by seven daily MDs and a 14-day washout period. P2Y(12) receptor blockade was estimated using the VASP assay, expressed as platelet reactivity index (VASP-PRI). Platelet aggregation was assessed by light transmission aggregometry (20 and 5 microM ADP). Twenty-four hours after prasgurel 60 mg or clopidogrel 300 mg and 600 mg, respectively, VASP-PRI decreased from approximately 80% to 8.9%, 54.7%, and 39.0%, and maximal platelet aggregation (MPA) decreased from approximately 79% to 10.8%, 42.7%, and 31.2%, with an overall VASP:MPA correlation of 0.88 (p < 0.01). VASP assay responses after the clopidogrel LDs showed a wider range of values (300 mg: 0-93%; 600 mg: 0-80%) than prasugrel (0-13%); MPA responses followed a similar trend. Pearson's correlation suggested a strong agreement between VASP and LTA (20 microM ADP) for MPA (r = 0.86, p < 0.0001). VASP and LTA demonstrated concordance across the response range of P2Y(12) receptor blockade following thienopyridine LDs.  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