全文获取类型
收费全文 | 198455篇 |
免费 | 3092篇 |
国内免费 | 54篇 |
专业分类
耳鼻咽喉 | 1320篇 |
儿科学 | 7474篇 |
妇产科学 | 3601篇 |
基础医学 | 19457篇 |
口腔科学 | 1908篇 |
临床医学 | 15059篇 |
内科学 | 35438篇 |
皮肤病学 | 1045篇 |
神经病学 | 18839篇 |
特种医学 | 9459篇 |
外国民族医学 | 5篇 |
外科学 | 31475篇 |
综合类 | 2553篇 |
一般理论 | 71篇 |
预防医学 | 21277篇 |
眼科学 | 3255篇 |
药学 | 10926篇 |
1篇 | |
中国医学 | 662篇 |
肿瘤学 | 17776篇 |
出版年
2023年 | 272篇 |
2022年 | 393篇 |
2021年 | 1021篇 |
2020年 | 610篇 |
2019年 | 862篇 |
2018年 | 22748篇 |
2017年 | 17947篇 |
2016年 | 20097篇 |
2015年 | 1663篇 |
2014年 | 1801篇 |
2013年 | 2080篇 |
2012年 | 8773篇 |
2011年 | 22821篇 |
2010年 | 19662篇 |
2009年 | 12247篇 |
2008年 | 20744篇 |
2007年 | 23009篇 |
2006年 | 1733篇 |
2005年 | 3268篇 |
2004年 | 4394篇 |
2003年 | 5268篇 |
2002年 | 3248篇 |
2001年 | 574篇 |
2000年 | 711篇 |
1999年 | 413篇 |
1998年 | 373篇 |
1997年 | 333篇 |
1996年 | 176篇 |
1995年 | 205篇 |
1994年 | 187篇 |
1993年 | 163篇 |
1992年 | 235篇 |
1991年 | 270篇 |
1990年 | 310篇 |
1989年 | 246篇 |
1988年 | 217篇 |
1987年 | 194篇 |
1986年 | 185篇 |
1985年 | 174篇 |
1984年 | 125篇 |
1983年 | 121篇 |
1982年 | 111篇 |
1980年 | 103篇 |
1978年 | 91篇 |
1977年 | 82篇 |
1976年 | 72篇 |
1974年 | 89篇 |
1971年 | 71篇 |
1970年 | 70篇 |
1969年 | 73篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Sarah Averbach Othman Kakaire Rachel McDiehl Christine Dehlendorf Felicia Lester Jody Steinauer 《Contraception》2019,99(2):87-93
Objective
This study assessed whether immediate postpartum insertion of levonorgestrel contraceptive implants is associated with a difference in infant growth from birth to 6 months, onset of lactogenesis, or breastfeeding continuation at 3 and 6 months postpartum compared to delayed insertion at 6 to 8 weeks postpartum.Study design
We conducted a randomized trial of women in Uganda who desired contraceptive implants postpartum. We randomly assigned participants to receive either immediate (within 5 days of delivery) or delayed (6 to 8 weeks postpartum) insertion of a two-rod levonorgestrel contraceptive implant system. This is a prespecified secondary analysis evaluating breastfeeding outcomes. The primary outcome of this secondary analysis was change in infant weight; infants were weighed and measured at birth and 6 months. We used a validated questionnaire to assess onset of lactogenesis daily in person while participants were in the hospital, and then daily by phone after they left the hospital, until lactogenesis was documented. We used interviewer-administered questionnaires to assess breastfeeding continuation and concerns at 3 months and 6 months postpartum.Results
Among the 96 women randomized to the immediate group and the 87 women to the delayed group, the mean change in infant weight from birth to 6 months was similar between groups: 4632?g in the immediate group and 4407?g in the delayed group (p=.26). Among the 97 women who had not experienced lactogenesis prior to randomization, the median time to onset of lactogenesis did not differ significantly between the immediate and delayed groups (65?h versus 63?h; p=.84). Similar proportions of women in the immediate and delayed groups reported exclusive breastfeeding at 3 months (74% versus 71%; p=.74) and 6 months (48% versus 52%; p=.58).Conclusion
We found no association between the timing of postpartum initiation of levonorgestrel contraceptive implants and change in infant growth from birth to 6 months, onset of lactogenesis, or breastfeeding continuation at 3 or 6 months postpartum.Implications
This study provides evidence that immediate postpartum initiation of contraception implants does not have a deleterious effect on infant growth or initiation or continuation of breastfeeding. 相似文献22.
Marie V. Plaisime PhD MPH Marie Jipguep-Akhtar PhD Joseph J. Locascio PhD Harolyn M. E. Belcher MD MHS Rachel R. Hardeman PhD MPH Katherine Picho-Kiroga PhD Sylvia P. Perry PhD Sean M. Phelan PhD MPH Michelle van Ryn PhD LMFT MPH John F. Dovidio PhD 《Health services research》2023,58(Z2):229-237
Objective
To examine the experience of interracial anxiety among health professionals and how it may affect the quality of their interactions with patients from racially marginalized populations. We explored the influence of prior interracial exposure—specifically through childhood neighborhoods, college student bodies, and friend groups—on interracial anxiety among medical students and residents. We also examined whether levels of interracial anxiety change from medical school through residency.Data Source
Web-based longitudinal survey data from the Medical Student Cognitive Habits and Growth Evaluation Study.Study Design
We used a retrospective longitudinal design with four observations for each trainee. The study population consisted of non-Black US medical trainees surveyed in their 1st and 4th years of medical school and 2nd and 3rd years of residency. Mixed effects longitudinal models were used to assess predictors of interracial anxiety and assess changes in interracial anxiety scores over time.Principal Findings
In total, 3155 non-Black medical trainees were followed for 7 years. Seventy-eight percent grew up in predominantly White neighborhoods. Living in predominantly White neighborhoods and having less racially diverse friends were associated with higher levels of interracial anxiety among medical trainees. Trainees' interracial anxiety scores did not substantially change over time; interracial anxiety was highest in the 1st year of medical school, lowest in the 4th year, and increased slightly during residency.Conclusions
Neighborhood and friend group composition had independent effects on interracial anxiety, indicating that premedical racial socialization may affect medical trainees' preparedness to interact effectively with diverse patient populations. Additionally, the lack of substantial change in interracial anxiety throughout medical training suggests the importance of providing curricular tools and structure (e.g., instituting interracial cooperative learning activities) to foster the development of healthy interracial relationships. 相似文献23.
Rachel P. Winograd Ned Presnall Erin Stringfellow Claire Wood Phil Horn Alex Duello 《The American journal of drug and alcohol abuse》2019,45(4):333-340
Background: The opioid addiction and overdose crisis continues to ravage communities across the U.S. Maintenance pharmacotherapy using buprenorphine or methadone is the most effective intervention for Opioid Use Disorder (OUD), yet few have immediate and sustained access to these medications. Objectives: To address lack of medication access for people with OUD, the Missouri Department of Mental Health began implementing a Medication First (Med First) treatment approach in its publicly-funded system of comprehensive substance use disorder treatment programs. Methods: This Perspective describes the four principles of Med First, which are based on evidence-based guidelines. It draws conceptual comparisons between the Housing First approach to chronic homelessness and the Med First approach to pharmacotherapy for OUD, and compares state certification standards for substance use disorder (SUD) treatment (the traditional approach) to Med First guidelines for OUD treatment. Finally, the Perspective details how Med First principles have been practically implemented. Results: Med First principles emphasize timely access to maintenance pharmacotherapy without requiring psychosocial services or discontinuation for any reason other than harm to the client. Early results regarding medication utilization and treatment retention are promising. Feedback from providers has been largely favorable, though clinical- and system-level obstacles to effective OUD treatment remain. Conclusion: Like the Housing First model, Medication First is designed to decrease human suffering and activate the strengths and capacities of people in need. It draws on decades of research and facilitates partnerships between psychosocial and medical treatment providers to offer effective and life-saving care to persons with OUD. 相似文献
24.
25.
Konrad Matyja Anna Małachowska-Jutsz Anna K. Mazur Kazimierz Grabas 《Ecotoxicology (London, England)》2016,25(5):924-939
Dehydrogenase activity is frequently used to assess the general condition of microorganisms in soil and activated sludge. Many studies have investigated the inhibition of dehydrogenase activity by various compounds, including heavy metal ions. However, the time after which the measurements are carried out is often chosen arbitrarily. Thus, it can be difficult to estimate how the toxic effects of compounds vary during the reaction and when the maximum of the effect would be reached. Hence, the aim of this study was to create simple and useful mathematical model describing changes in dehydrogenase activity during exposure to substances that inactivate enzymes. Our model is based on the Lagergrens pseudo-first-order equation, the rate of chemical reactions, enzyme activity, and inactivation and was created to describe short-term changes in dehydrogenase activity. The main assumption of our model is that toxic substances cause irreversible inactivation of enzyme units. The model is able to predict the maximum direct toxic effect (MDTE) and the time to reach this maximum (TMDTE). In order to validate our model, we present two examples: inactivation of dehydrogenase in microorganisms in soil and activated sludge. The model was applied successfully for cadmium and copper ions. Our results indicate that the predicted MDTE and TMDTE are more appropriate than EC50 and IC50 for toxicity assessments, except for long exposure times. 相似文献
26.
27.
28.
Contraceptive use is an important strategy for the prevention of unwanted pregnancy and avoidance of induced abortion. Of all the contraception methods, emergency contraceptive (EC) offers the last chance to achieve this. However, few studies have documented the use of EC among young people in Ghana. This study explored knowledge and usage of EC as well as the factors associated with it among University of Cape Coast students. Data were obtained on the knowledge and usage of ECs among University of Cape Coast students in 2013. Logistic regression analysis was used to investigate the association between students’ socio-demographic characteristics and EC knowledge and use. More male students (72 %) than females (59 %) were sexually active. Fifty-seven percent of the respondents had ever heard of EC and 36 % had ever used EC. Although males were more likely to be sexually active, females were more likely to have knowledge of EC use compared to males. The study underscores the need to increase awareness regarding EC among University students in order to offer them the opportunity that EC provides if other forms of contraceptives are missed. 相似文献
29.
30.