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   10920篇
  免费   1644篇
  国内免费   208篇
耳鼻咽喉   160篇
儿科学   200篇
妇产科学   309篇
基础医学   592篇
口腔科学   738篇
临床医学   1789篇
内科学   1975篇
皮肤病学   166篇
神经病学   496篇
特种医学   395篇
外国民族医学   3篇
外科学   1614篇
综合类   875篇
一般理论   1篇
预防医学   848篇
眼科学   90篇
药学   561篇
  13篇
中国医学   487篇
肿瘤学   1460篇
  2024年   42篇
  2023年   430篇
  2022年   435篇
  2021年   1050篇
  2020年   947篇
  2019年   885篇
  2018年   710篇
  2017年   664篇
  2016年   635篇
  2015年   555篇
  2014年   749篇
  2013年   752篇
  2012年   586篇
  2011年   605篇
  2010年   468篇
  2009年   436篇
  2008年   460篇
  2007年   414篇
  2006年   392篇
  2005年   277篇
  2004年   203篇
  2003年   195篇
  2002年   186篇
  2001年   134篇
  2000年   94篇
  1999年   88篇
  1998年   79篇
  1997年   36篇
  1996年   35篇
  1995年   28篇
  1994年   31篇
  1993年   15篇
  1992年   12篇
  1991年   20篇
  1990年   15篇
  1989年   13篇
  1988年   15篇
  1987年   10篇
  1986年   8篇
  1985年   11篇
  1984年   7篇
  1983年   4篇
  1982年   8篇
  1981年   9篇
  1980年   6篇
  1979年   3篇
  1978年   6篇
  1976年   2篇
  1975年   4篇
  1969年   1篇
排序方式: 共有10000条查询结果,搜索用时 984 毫秒
61.
A computer model was designed as a relational database to assess breast cancer screening in a cohort of women where the growth and development of breast cancer originates with the first malignant cell. The concepts of thresholds for growth, axillary spread, and distant sites are integrated. With tumor diagnosis, staging was performed that includes clinical and sub-clinical states. The model was parameterized to have staging characteristics similar to data published by the Surveillance, Epidemiology, and End-Results (SEER) Program. Validation was accomplished by comparing simulated staging results with non-SEER sources, and simulated survival with independent clinical survival data.  相似文献   
62.
Fourteen women with primary dysmenorrhea were administered four sessions of systematic desensitization (SD) by either a male or a female therapist. The following measures were taken during the flow periods before and after treatment and at a 6-month follow-up: menstrual symptom checklist, medication usage, invalid hours, and menstrual attitudes. At pretreatment, menstrually distressed women had significantly higher scores on all measures compared to a normative group and an explicitly nondistressed group. At posttreatment, treated women's scores on the dependent variables were significantly reduced. All indices were reduced to a nondistressed level at posttreatment and at 6-month follow-up. Type of dysmenorrhea (congestive vs. spasmodic), trait anxiety level, and therapist sex did not predict differential responsiveness to SD. SD did not affect frontalis EMG, peripheral blood flow, or pain threshold. A Retrospective Symptom Scale of menstrual distress was found to be highly reliable, valid, and sensitive.  相似文献   
63.
Early stages of chick somite development   总被引:17,自引:0,他引:17  
We report on the formation and early differentiation of the somites in the avian embryo. The somites are derived from the mesoderm which, in the body (excluding the head), is subdivided into four compartments: the axial, paraxial, intermediate and lateral plate mesoderm. Somites develop from the paraxial mesoderm and constitute the segmental pattern of the body. They are formed in pairs by epithelialization, first at the cranial end of the paraxial mesoderm, proceeding caudally, while new mesenchyme cells enter the paraxial mesoderm as a consequence of gastrulation. After their formation, which depends upon cell-cell and cell-matrix interactions, the somites impose segmental pattern upon peripheral nerves and vascular primordia. The newly formed somite consists of an epithelial ball of columnar cells enveloping mesenchymal cells within a central cavity, the somitocoel. Each somite is surrounded by extracellular matrix material connecting the somite with adjacent structures. The competence to form skeletal muscle is a unique property of the somites and becomes realized during compartmentalization, under control of signals emanating from surrounding tissues. Compartmentalization is accompanied by altered patterns of expression of Pax genes within the somite. These are believed to be involved in the specification of somite cell lineages. Somites are also regionally specified, giving rise to particular skeletal structures at different axial levels. This axial specification appears to be reflected in Hox gene expression. MyoD is first expressed in the dorsomedial quadrant of the still epithelial somite whose cells are not yet definitely committed. During early maturation, the ventral wall of the somite undergoes an epithelio-mesenchymal transition forming the sclerotome. The sclerotome later becomes subdivided into rostral and caudal halves which are separated laterally by von Ebner's fissure. The lateral part of the caudal half of the sclerotome mainly forms the ribs, neural arches and pedicles of vertebrae, whereas within the lateral part of the rostral half the spinal nerve develops. The medially migrating sclerotomal cells form the peri-notochordal sheath, and later give rise to the vertebral bodies and intervertebral discs. The somitocoel cells also contribute to the sclerotome. The dorsal half of the somite remains epithelial and is referred to as the dermomyotome because it gives rise to the dermis of the back and the skeletal musculature. The cells located within the lateral half of the dermomyotome are the precursors of the muscles of the hypaxial domain of the body, whereas those in the medial half are precursors of the epaxial (back) muscles. Single epithelial cells at the cranio-medial edge of the dermomyotome elongate in a caudal direction, beneath the dermomyotome, and become anchored at its caudal margin. These post-mitotic and muscle protein-expressing cells form the myotome. At limb levels, the precursors of hypaxial muscles undergo an epithelio-mesenchymal transition and migrate into the somatic mesoderm, where they replicate and later differentiate. These cells express the Pax-3 gene prior to, during and after this migration. All compartments of the somite contribute endothelial cells to the formation of vascular primordia. These cells, unlike all other cells of the somite, occasionally cross the midline of the developing embryo. We also suggest a method for staging somites according to their developmental age.  相似文献   
64.
《Value in health》2022,25(5):773-784
ObjectivesAs healthcare systems continue to respond to the COVID-19 pandemic, cost-effectiveness evidence will be needed to identify which tests and treatments for COVID-19 offer value for money. We sought to review economic evaluations of diagnostic tests and treatments for COVID-19, critically appraising the methodological approaches used and reporting cost-effectiveness estimates, using a “living” systematic review approach.MethodsKey databases (including MEDLINE, EconLit, Embase) were last searched on July 12, 2021. Gray literature and model repositories were also searched. Only full economic evaluations published in English were included. Studies were quality assessed and data were extracted into standard tables. Results were narratively summarized. The review was completed by 2 reviewers independently, with disagreements resolved through discussion with a senior reviewer.ResultsOverall, 3540 records were identified, with 13 meeting the inclusion criteria. After quality assessment, 6 were excluded because of very severe limitations. Of the 7 studies included, 5 were cost-utility analyses and 2 were cost-effectiveness analyses. All were model-based analyses. A total of 5 evaluated treatments (dexamethasone, remdesivir, hypothetical) and 2 evaluated hypothetical testing strategies. Cost-effectiveness estimates were sensitive to the treatment effect on survival and hospitalization, testing speed and accuracy, disease severity, and price.ConclusionsPresently, there are few economic evaluations for COVID-19 tests and treatments. They suggest treatments that confer a survival benefit and fast diagnostic tests may be cost effective. Nevertheless, studies are subject to major evidence gaps and take inconsistent analytical approaches. The evidence may improve for planned updates of this “living” review.  相似文献   
65.
66.
BACKGROUD/OBJECTIVESEvidence has suggested an association between serum vitamin D and metabolic syndrome (MetS), but prospective studies are very limited. The objective was to assess the dose-response association between serum vitamin D concentration and MetS risk using a systematic review and meta-analysis of updated observational studies.MATERIALS/METHODSUsing MEDLINE, PubMed, and Embase, a systematic literature search was conducted through February 2020 and the references of relevant articles were reviewed. A random-effects model was used to estimate the summary odds ratio/relative risk and 95% confidence interval (CI). Heterogeneity among studies was evaluated with I2 statistic. In total, 23 observational studies (19 cross-sectional studies, and four cohort studies) were included in the meta-analysis.RESULTSThe pooled estimates (95% CI) for MetS per 25-nmol/L increment in serum vitamin D concentration were 0.80 (95% CI, 0.76–0.84; I2 = 53.5) in cross-sectional studies, and 0.85 (95% CI, 0.72–0.98; I2 = 85.8) in cohort studies. Similar results were observed, irrespectively of age of study population, study location, MetS criteria, and adjustment factors. There was no publication bias for the dose-response meta-analysis of serum vitamin D concentrations and MetS.CONCLUSIONSDose-response meta-analysis demonstrated that a 25-nmol/L increment in the serum vitamin D concentration was associated with 20% and 15% lower risks of MetS in cross-sectional studies and cohort studies, respectively.  相似文献   
67.
More than one year has passed since the first cases of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome (SARS)-CoV-2 coronavirus were reported in Wuhan (China), rapidly evolving into a global pandemic. This infectious disease has become a major public health challenge in the world. Unfortunately, to date, no specific antivirals have been proven to be effective against COVID-19, and although a few vaccines are available, the mortality rate is not decreasing but is still increasing. One therapeutic strategy has been focused on infection prevention and control measures. In this regard, the use of nutraceutical supports may play a role against some aspect of the infection, particularly the inflammatory state and the immune system function of patients, thus representing a strategy to control the worst outcomes of this pandemic. For this reason, we performed an overview including meta-analyses and systematic reviews to assess the association among melatonin, vitamin C, vitamin D, zinc supplementation and inflammatory markers using three databases, namely, MEDLINE, PubMed Central and the Cochrane Library of Systematic Reviews. According to the evidence available, an intake of 50,000 IU/month of vitamin D showed efficacy in CRP. An amount of 1 to 2 g per day of vitamin C demonstrated efficacy both in CRP and endothelial function, and a dosage of melatonin ranging from 5 to 25 mg /day showed good evidence of efficacy in CRP, TNF and IL6. A dose of 50 mg/day of elemental zinc supplementation showed positive results in CRP. Based on the data reported in this review, the public health system could consider whether it is possible to supplement the current limited preventive measures through targeted nutraceutical large-scale administration.  相似文献   
68.
ObjectivesPain, a complex subjective experience, is common in care home residents. Despite advances in pain management, optimal pain control remains a challenge. In this updated systematic review, we examined effectiveness of interventions for treating chronic pain in care home residents.DesignA Cochrane-style systematic review and meta-analysis using PRISMA guidelines.Setting and ParticipantsRandomized and nonrandomized controlled trials and intervention studies included care home residents aged ≥60 years receiving interventions to reduce chronic pain.MethodsSix databases were searched to identify relevant studies. After duplicate removal, articles were screened by title and abstract. Full-text articles were reviewed and included if they implemented a pain management intervention and measured pain with a standardized quantitative pain scale. Meta-analyses calculated standardized mean differences (SMDs) using random-effect models. Risk of bias was assessed using the Cochrane Risk-of-Bias Tool 2.0.ResultsWe included 42 trials in the meta-analysis and described 13 more studies narratively. Studies included 26 nondrug alternative treatments, 8 education interventions, 7 system modifications, 3 nonanalgesic drug treatments, 2 analgesic treatments, and 9 combined interventions. Pooled results at trial completion revealed that, except for nonanalgesic drugs and health system modification interventions, all interventions were at least moderately effective in reducing pain. Analgesic treatments (SMD ?0.80; 95% CI ?1.47 to ?0.12; P = .02) showed the greatest treatment effect, followed by nondrug alternative treatments (SMD ?0.70; 95% CI ?0.95 to ?0.45; P < .001), combined interventions (SMD ?0.37; 95% CI ?0.60 to ?0.13; P = .002), and education interventions (SMD ?0.31; 95% CI ?0.48 to ?0.15; P < .001).Conclusions and ImplicationsOur findings suggest that analgesic drugs and nondrug alternative pain management strategies are the most effective in reducing pain among care home residents. Clinicians should also consider implementing nondrug alternative therapies in care homes, rather than relying solely on analgesic drug options.  相似文献   
69.
 目的 系统评价与分析恩替卡韦(ETV)序贯聚乙二醇化干扰素-α(Peg-IFN-α)与单用ETV在治疗慢性乙型肝炎患者中的临床疗效。方法 计算机检索PubMed、Embase、Cochrane Library、中国知网、万方数据库,搜索有关ETV及ETV序贯Peg-IFN-α治疗慢性乙型肝炎的随机对照试验研究,应用Stata 16.0软件对符合纳入条件的临床研究进行系统评价与分析。结果 共纳入10篇文献,1 250例患者,其中553例患者采用ETV序贯Peg-IFN-α治疗,697例患者单用ETV治疗,两组患者组间基线特征比较,差异均无统计学意义(均P>0.05)。ETV序贯Peg-IFN-α试验组的HBsAg转换率、HBsAg清除率、HBeAg转换率、HBeAg清除率均高于ETV对照组,差异均有统计学意义(均P<0.05)。结论 在慢性乙型肝炎抗病毒治疗中,总体上ETV序贯Peg-IFN-α治疗疗效优于单用ETV。  相似文献   
70.
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