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   78015篇
  免费   7717篇
  国内免费   156篇
耳鼻咽喉   650篇
儿科学   2311篇
妇产科学   1788篇
基础医学   11255篇
口腔科学   1678篇
临床医学   10452篇
内科学   14590篇
皮肤病学   1388篇
神经病学   7373篇
特种医学   2605篇
外国民族医学   1篇
外科学   9036篇
综合类   1418篇
现状与发展   1篇
一般理论   59篇
预防医学   8675篇
眼科学   1432篇
药学   5966篇
中国医学   114篇
肿瘤学   5096篇
  2023年   372篇
  2021年   1342篇
  2020年   947篇
  2019年   1555篇
  2018年   1820篇
  2017年   1367篇
  2016年   1521篇
  2015年   1663篇
  2014年   2294篇
  2013年   3116篇
  2012年   4745篇
  2011年   4843篇
  2010年   2665篇
  2009年   2490篇
  2008年   4301篇
  2007年   4452篇
  2006年   4171篇
  2005年   4194篇
  2004年   3789篇
  2003年   3573篇
  2002年   3414篇
  2001年   1760篇
  2000年   1577篇
  1999年   1685篇
  1998年   856篇
  1997年   657篇
  1996年   608篇
  1995年   696篇
  1994年   596篇
  1993年   632篇
  1992年   1316篇
  1991年   1230篇
  1990年   1156篇
  1989年   1123篇
  1988年   1040篇
  1987年   1024篇
  1986年   1033篇
  1985年   941篇
  1984年   835篇
  1983年   678篇
  1982年   481篇
  1981年   410篇
  1980年   397篇
  1979年   612篇
  1978年   509篇
  1977年   398篇
  1976年   402篇
  1974年   455篇
  1973年   414篇
  1972年   403篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Smoking cessation reduces the risk of death, improves recovery, and reduces the risk of hospital readmission. Evidence and policy support hospital admission as an ideal time to deliver smoking-cessation interventions. However, this is not well implemented in practice. In this systematic review, the authors summarize the literature on smoking-cessation implementation strategies and evaluate their success to guide the implementation of best-practice smoking interventions into hospital settings. The CINAHL Complete, Embase, MEDLINE Complete, and PsycInfo databases were searched using terms associated with the following topics: smoking cessation, hospitals, and implementation. In total, 14,287 original records were identified and screened, resulting in 63 eligible articles from 56 studies. Data were extracted on the study characteristics, implementation strategies, and implementation outcomes. Implementation outcomes were guided by Proctor and colleagues' framework and included acceptability, adoption, appropriateness, cost, feasibility, fidelity, penetration, and sustainability. The findings demonstrate that studies predominantly focused on the training of staff to achieve implementation. Brief implementation approaches using a small number of implementation strategies were less successful and poorly sustained compared with well resourced and multicomponent approaches. Although brief implementation approaches may be viewed as advantageous because they are less resource-intensive, their capacity to change practice in a sustained way lacks evidence. Attempts to change clinician behavior or introduce new models of care are challenging in a short time frame, and implementation efforts should be designed for long-term success. There is a need to embrace strategic, well planned implementation approaches to embed smoking-cessation interventions into hospitals and to reap and sustain the benefits for people who smoke.  相似文献   
2.
3.
4.
5.
We are, as of May 2019, witnessing yet another “caravan” of people fleeing violence in Latin America, bonding together to reach the territory of safer states in the North. Similarly, in the fall of 2015, Europe experienced the movement of many refugees fleeing war, persecution, and grave human rights violations in Syria. These new waves of people on the move have raised anew important questions about asylum and refuge: who should be able to claim asylum? Should the fear of persecution be sufficient, or do asylum seekers need to show that they have actually suffered it? And maybe most controversially, how should asylum‐granting states respond to the plight of those asking for asylum on their territory? The moral principles guiding asylum and refuge are different from the rules usually regulating immigration, which are based on the principle of territorial sovereignty that allows nation‐states to discriminate and select among those who hope to immigrate. Asylum and refuge instead call upon nation‐states to provide refugees with a new home, protect human rights, and over time, provide access to the social, political and civic rights that characterize membership. Included in the list of human rights, I will argue, is the provision of the means for individual physical and psychological well‐being.  相似文献   
6.
A central problem for the international governance of heritable germline gene editing is that there are important differences in attitudes and values as well as ethical and health care considerations around the world. These differences are reflected in a complicated and diverse regulatory landscape. Several publications have discussed whether reproductive uses would be legally permissible in individual countries and whether clinical applications could emerge in the context of regulatory gaps and gray areas. Systematic comparative studies that explore issues related to the governance of this technology from different national and international perspectives are needed to address the lack of knowledge in this area. In this research report, we contribute to filling this gap by presenting views of stakeholders in the United Kingdom on challenges to the governance of heritable genome editing. We present findings from a multistakeholder study conducted in the United Kingdom between October 2016 and January 2018 and funded by the Wellcome Trust. This research included interviews, literature analysis, and a workshop. We involved leading U.K. scientists, in vitro fertilization clinicians, and representatives from regulatory bodies, patient organizations, and other civil societal organizations, as well as fertility companies. Part one of this article explores stakeholder perceptions of possible global developments in heritable genome editing and associated risks and governance challenges. Part two presents a range of policy options that were generated during the workshop in relation to the challenges discussed in part one.  相似文献   
7.
8.

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   
9.
10.
Bisphenol A is a commercially important chemical used to make polycarbonate plastic, epoxy resins, and other specialty products. Despite an extensive body of in vitro, animal and human observational studies on the effects of exposure to bisphenol A, no authoritative bodies in the U.S. have adopted or recommended occupational exposure limits for bisphenol A. In 2017, the National Institute for Occupational Safety and Health published a Draft process for assigning health-protective occupational exposure bands, i.e., an airborne concentration range, to chemicals lacking an occupational exposure limit. Occupational exposure banding is a systematic process that uses both quantitative and qualitative toxicity information on selected health effect endpoints to assign an occupational exposure band for a chemical. The Draft process proposes three methodological tiers of increasing complexity for assigning an occupational exposure band. We applied Tier 1 (based on the Globally Harmonized System of Classification and Labelling) and Tier 2 (based on authoritative sources/reviews) to assign an occupational exposure band to bisphenol A. Under both Tier 1 and 2, the occupational exposure band for bisphenol A was “E” (<0.01?mg/m3), an assignment based on eye damage. “E” is the lowest exposure concentration range, reserved for chemicals with high potential toxicity. If eye damage was excluded in assigning an air concentration exposure range, then bisphenol A would band as “D” (>0.01 to 0.1?mg/m3) under Tier 1 (based on reproductive toxicity and respiratory/skin sensitization) and under Tier 2 (based on specific target organ toxicity-repeated exposure). In summary, Tiers 1 and 2 gave the same occupational exposure band for bisphenol A when eye damage was included (“E”) or excluded (“D”) as an endpoint.  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