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   28439篇
  免费   2276篇
  国内免费   67篇
耳鼻咽喉   240篇
儿科学   1027篇
妇产科学   878篇
基础医学   3524篇
口腔科学   444篇
临床医学   5170篇
内科学   4943篇
皮肤病学   388篇
神经病学   2678篇
特种医学   530篇
外科学   2303篇
综合类   416篇
一般理论   64篇
预防医学   3926篇
眼科学   348篇
药学   1615篇
中国医学   26篇
肿瘤学   2262篇
  2023年   153篇
  2022年   195篇
  2021年   493篇
  2020年   421篇
  2019年   719篇
  2018年   751篇
  2017年   562篇
  2016年   665篇
  2015年   731篇
  2014年   920篇
  2013年   1460篇
  2012年   2000篇
  2011年   2021篇
  2010年   1113篇
  2009年   1013篇
  2008年   1897篇
  2007年   2031篇
  2006年   2025篇
  2005年   1927篇
  2004年   1807篇
  2003年   1733篇
  2002年   1641篇
  2001年   248篇
  2000年   210篇
  1999年   238篇
  1998年   397篇
  1997年   279篇
  1996年   277篇
  1995年   257篇
  1994年   226篇
  1993年   222篇
  1992年   138篇
  1991年   112篇
  1990年   111篇
  1989年   118篇
  1988年   105篇
  1987年   82篇
  1986年   100篇
  1985年   123篇
  1984年   104篇
  1983年   110篇
  1982年   138篇
  1981年   134篇
  1980年   137篇
  1979年   54篇
  1978年   57篇
  1977年   56篇
  1976年   60篇
  1975年   50篇
  1974年   45篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
991.
The study purpose was to test 1-year prospective associations between English–Spanish bilingualism and executive function in 5th to 6th grade students while controlling for biculturalism. Participants included 182 US Latino students (50 % female). Self-report surveys assessed biculturalism, bilingualism, and executive function (i.e., working memory, organizational skills, inhibitory control, and emotional control, as well as a summary executive function score). General linear model regressions demonstrated that bilingualism significantly predicted the summary executive function score as well as working memory such that bilingual proficiency was positively related to executive function. Results are the first to demonstrate (a) prospective associations between bilingualism to executive function while controlling for the potential third variable of biculturalism, and (b) a principal role for working memory in this relationship. Since executive function is associated with a host of health outcomes, one implication of study findings is that bilingualism may have an indirect protective influence on youth development.  相似文献   
992.
Migrants and recent immigrants in the US constitute a large population that is vulnerable to HIV. From March 2005 to February 2007, three community-based organizations conducted rapid HIV testing among migrants in five states. Participants were asked to complete a survey on sociodemographics, HIV-risk behaviors, and HIV-testing histories with the aim of understanding factors associated with HIV testing. Among 5,247 persons tested, 6 (0.1 %) were HIV-positive. Among 3,135 persons who completed surveys, more than half had never been tested for HIV previously (59 %). Participants reported high levels of HIV-risk behaviors in the past year, including 2 or more sex partners (45 %), sex while high/drunk (30 %), and transactional sex (29 %). Multivariate analysis identified several factors independently associated with decreased likelihood of prior HIV testing, including poor spoken English. Continued efforts are needed to ensure that migrant populations have improved access to HIV testing and prevention services. Understanding factors associated with migrants’ lack of previous HIV testing may help focus these efforts.  相似文献   
993.
994.

Background

Clubfoot can be treated nonoperatively, most commonly using a Ponseti approach, or surgically, most often with a comprehensive clubfoot release. Little is known about how these approaches compare with one another at longer term, or how patients treated with these approaches differ in terms of foot function, foot biomechanics, or quality-of-life from individuals who did not have clubfoot as a child.

Questions/purposes

We compared (1) focused physical and radiographic examinations, (2) gait analysis, and (3) quality-of-life measures at long-term followup between groups of adult patients with clubfoot treated either with the Ponseti method of nonsurgical management or a comprehensive surgical release through a Cincinnati incision, and compared these two groups with a control group without clubfoot.

Methods

This was a case control study of individuals treated for clubfoot at two separate institutions with different methods of treatment between 1983 to 1987. One hospital used only the Ponseti method and the other mainly used a comprehensive clubfoot release. There were 42 adults (24 treated surgically, 18 treated with Ponseti method) with isolated clubfoot along with 48 healthy control subjects who agreed to participate in a detailed analysis of physical function, foot biomechanics, and quality-of-life metrics.

Results

Both treatment groups had diminished strength and motion compared with the control subjects on physical examination measures; however, the Ponseti group had significantly greater ankle plantar flexion ROM (p < 0.001), greater ankle plantar flexor (p = 0.031) and evertor (p = 0.012) strength, and a decreased incidence of osteoarthritis in the ankle and foot compared with the surgical group. During gait the surgical group had reduced peak ankle plantar flexion (p = 0.002), and reduced sagittal plane hindfoot (p = 0.009) and forefoot (p = 0.008) ROM during the preswing phase compared with the Ponseti group. The surgical group had the lowest overall ankle power generation during push off compared with the control subjects (p = 0.002). Outcome tools revealed elevated pain levels in the surgical group compared with the Ponseti group (p = 0.008) and lower scores for physical function and quality-of-life for both clubfoot groups compared with age-range matched control subjects (p = 0.01).

Conclusions

Although individuals in each treatment group experienced pain, weakness, and reduced ROM, they were highly functional into early adulthood. As adults the Ponseti group fared better than the surgically treated group because of advantages including increased ROM observed at the physical examination and during gait, greater strength, and less arthritis. This study supports efforts to correct clubfoot with Ponseti casting and minimizing surgery to the joints, and highlights the need to improve methods that promote ROM and strength which are important for adult function.

Level of Evidence

Level III, prognostic study.  相似文献   
995.

Background

There is significant lack of information regarding the Canadian pediatric surgery workforce.

Methods

An IRB-approved survey aimed at assessing workforce issues was administered to pediatric surgeons and pediatric surgery chiefs in Canada in 2012.

Results

The survey was completed by 98% of practicing surgeons and 13 of the 18 division chiefs. Only 6% of surgeons are older than 60 years, and only a fifth anticipate retirement over the next decade. The workforce is stable, with 82% of surgeons unlikely to change current positions. Surgical volume showed essentially no growth during the 5-year period 2006–2010. The majority of surgeons felt they were performing the right number or too few cases and anticipated minimal or no future growth in their individual practices or that of their group. Based on anticipated vacancies, the best estimate is a need for 20 new pediatric surgeons over the next decade. This need is significantly surpassed by the current output from the Canadian training programs.

Conclusions

The Canadian pediatric surgery workforce is currently saturated. The mismatch between the number of graduating trainees and the available positions over the next decade has significant repercussions for current surgery and pediatric surgery residents wishing to practice in Canada.  相似文献   
996.
Branding and advertising have a powerful effect on both familiarity and preference for products, yet no neuroimaging studies have examined neural response to logos in children. Food advertising is particularly pervasive and effective in manipulating choices in children. The purpose of this study was to examine how healthy children’s brains respond to common food and other logos. A pilot validation study was first conducted with 32 children to select the most culturally familiar logos, and to match food and non-food logos on valence and intensity. A new sample of 17 healthy weight children were then scanned using functional magnetic resonance imaging. Food logos compared to baseline were associated with increased activation in orbitofrontal cortex and inferior prefrontal cortex. Compared to non-food logos, food logos elicited increased activation in posterior cingulate cortex. Results confirmed that food logos activate some brain regions in children known to be associated with motivation. This marks the first study in children to examine brain responses to culturally familiar logos. Considering the pervasiveness of advertising, research should further investigate how children respond at the neural level to marketing.  相似文献   
997.
998.
We previously reported that moderate calorie restriction (CR) has minimal impact on testicular gene expression in young adult rhesus macaques, and no obvious negative impact on semen quality or plasma testosterone levels. We now extend these findings by examining the influence of CR on various aspects of the reproductive axis of older males, including 24-h circulating testosterone levels, testicular gene expression, and testicular morphology. Young adult and old adult male rhesus macaques were subjected to either 30 % CR for 5–7 years, or were fed a standard control diet. Analysis of the 24-h plasma testosterone profiles revealed a significant age-associated decline, but no evidence for CR-induced suppression in either the young or old males. Similarly, expression profiling of key genes associated with testosterone biosynthesis and Leydig cell maintenance showed no significant CR-induced changes in either the young or old animals. The only evidence for CR-associated negative effects on the testis was detected in the old animals at the histological level; when old CR animals were compared with their age-matched controls, there was a modest decrease in seminiferous tubule diameter and epithelium height, with a concomitant increase in the number of depleted germ cell lines. Reassuringly, data from this study and our previous study suggest that moderate CR does not negatively impact 24-h plasma testosterone profiles or testicular gene expression. Although there appear to be some minor CR-induced effects on testicular morphology in old animals, it is unclear if these would significantly compromise fertility.  相似文献   
999.
1000.
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