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   35222篇
  免费   2679篇
  国内免费   96篇
耳鼻咽喉   334篇
儿科学   1046篇
妇产科学   903篇
基础医学   5369篇
口腔科学   472篇
临床医学   5012篇
内科学   6269篇
皮肤病学   700篇
神经病学   3929篇
特种医学   816篇
外科学   3222篇
综合类   289篇
现状与发展   1篇
一般理论   33篇
预防医学   3752篇
眼科学   606篇
药学   2310篇
中国医学   42篇
肿瘤学   2892篇
  2024年   32篇
  2023年   279篇
  2022年   428篇
  2021年   893篇
  2020年   594篇
  2019年   927篇
  2018年   1102篇
  2017年   859篇
  2016年   939篇
  2015年   972篇
  2014年   1380篇
  2013年   1777篇
  2012年   2805篇
  2011年   2900篇
  2010年   1563篇
  2009年   1428篇
  2008年   2447篇
  2007年   2527篇
  2006年   2277篇
  2005年   2380篇
  2004年   2107篇
  2003年   1960篇
  2002年   1845篇
  2001年   248篇
  2000年   150篇
  1999年   302篇
  1998年   395篇
  1997年   321篇
  1996年   237篇
  1995年   238篇
  1994年   191篇
  1993年   179篇
  1992年   122篇
  1991年   113篇
  1990年   90篇
  1989年   101篇
  1988年   78篇
  1987年   69篇
  1986年   61篇
  1985年   52篇
  1984年   73篇
  1983年   56篇
  1982年   59篇
  1981年   67篇
  1980年   68篇
  1979年   31篇
  1978年   30篇
  1977年   37篇
  1976年   29篇
  1974年   28篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
In humans, studies of back muscle activity have mainly addressed the functioning of lumbar muscles during postural adjustments or rhythmic activity, including locomotor tasks. The present study investigated how back muscles are activated along the spine during rhythmical activities in order to gain insights into spinal neuronal organization. Electromyographic recordings of back muscles were performed at various trunk levels, and changes occurring in burst amplitudes and phase relationships were analyzed. Subjects performed several rhythmic behaviors: forward walking (FW), backward walking (BW), amble walking (where the subjects moved their arms in phase with the ipsilateral leg), walking on hands and knees (HK) and walking on hands with the knees on the edge of a treadmill (Hand). In a final task, the subjects were standing and were asked to swing (Swing) only their arms as if they were walking. It was found that axial trunk muscles are sequentially activated by a motor command running along the spinal cord (which we term “motor waves”) during various types of locomotion or other rhythmic motor tasks. The bursting pattern recorded under these conditions can be classified into three categories: (1) double-burst rhythmic activity in a descending (i.e., with a rostro-caudal propagation) motor wave during FW, BW and HK conditions; (2) double-burst rhythmic activity with a stationary motor wave (i.e., occurring in a single phase along the trunk) during the ‘amble’ walk condition; (3) monophasic rhythmic activity with an ascending (i.e., with a caudo-rostral propagation) motor wave during the Swing and Hands conditions. Our results suggest that the networks responsible for the axial propagation of motor activity during locomotion may correspond to those observed in invertebrates or lower vertebrates, and thus may have been partly phylogenetically conserved. Such an organization could support the dynamic control of posture by ensuring fluent movement during locomotion.  相似文献   
992.
993.
Optimal donor selection is critical in hematopoietic stem cell transplantation (HSCT). Donor–recipient sex mismatch, donor age, and female donor–donor parity are known to impact graft-versus-host disease (GVHD) and outcomes in adults. Minor histocompatibility antigens encoded by the human Y chromosome can result in specific antibody formation in some female donors, may increase in frequency with increasing donor age, and may be contributory to the increased incidence of GVHD. To better understand the role of donor age/sex and sex matching in HSCT outcomes, we conducted a retrospective study of pediatric patients receiving their first myeloablative sibling donor HSCT (n?=?244) from 1998 to 2012. Observed rates of GVHD were low: 17% of patients surviving past engraftment (n?=?243) developed grades II to IV acute GVHD (aGVHD) and 14% surviving ≥ 100 days (n?=?229) developed chronic GVHD (cGVHD). On multivariate analysis the risk of aGVHD, cGVHD, and death increased with patient age as expected. Female donor sex and sex mismatch (female donor–male recipient) had no impact on the development of aGVHD. cGVHD was increased with female donors only if the donor was ≥12 years old. No cGVHD was observed among 109 patients aged < 10 years who received a 6/6 HLA-matched marrow HSCT, regardless of donor age or sex. Survival was mostly driven by diagnosis. Results suggest that in pediatric HSCT, young HLA-matched siblings are equivalently good donors regardless of sex or donor–recipient sex mismatch.  相似文献   
994.
The major reason for treatment failure after allografting in multiple myeloma (MM) is relapse. Donor lymphocyte infusions (DLIs) are considered a valuable post-transplant strategy mainly for relapsed patients but using them to prevent relapse in MM has been reported rarely. In the present study, we examined the efficacy of prophylactic DLIs after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in myeloma patients with a long-term follow-up of more than 5 years. A total of 61 patients with MM who did not relapse or develop disease progression after allo-HSCT were treated with prophylactic DLI in an escalating fashion (overall 132 DLI procedures) to deepen remission status and prevent relapse. Overall response rate to DLI was 77%. Thirty-three patients (54%) upgraded their remission status, 41 patients (67%) achieved or maintained complete remission, and 26% achieved a molecular remission. Incidence of acute graft-versus-host disease (GVHD) grade II to IV was 33% and no DLI-related mortality was noted. After a median follow-up of 68.7 months from first DLI the estimated 8-year progression-free survival (PFS), and overall survival (OS) in a landmark analysis was 43% (95% confidence interval [CI], 28% to 57%) and 67% (95% CI, 53% to 82%), respectively, with best outcome for patients who acquired molecular remission (8-year PFS was 62% and 8-year OS was 83%). Prophylactic escalating DLI in a selected cohort of MM patients to prevent relapse after allograft resulted in a low incidence of severe GVHD and encouraging long-term results, especially if molecular remission is achieved.  相似文献   
995.
Abstract: Background: Both peer and professional support have been identified as important to the success of breastfeeding. The aim of this metasynthesis was to examine women’s perceptions and experiences of breastfeeding support, either professional or peer, to illuminate the components of support that they deemed “supportive.” Methods: The metasynthesis included studies of both formal or “created” peer and professional support for breastfeeding women but excluded studies of family or informal support. Qualitative studies were included as well as large‐scale surveys if they reported the analysis of qualitative data gathered through open‐ended responses. Primiparas and multiparas who initiated breastfeeding were included. Studies published in English, in peer‐reviewed journals, and undertaken between January 1990 and December 2007 were included. After assessment for relevance and quality, 31 studies were included. Meta‐ethnographic methods were used to identify categories and themes. Results: The metasynthesis resulted in four categories comprising 20 themes. The synthesis indicated that support for breastfeeding occurred along a continuum from authentic presence at one end, perceived as effective support, to disconnected encounters at the other, perceived as ineffective or even discouraging and counterproductive. A facilitative approach versus a reductionist approach was identified as contrasting styles of support that women experienced as helpful or unhelpful. Conclusions: The findings emphasize the importance of person‐centered communication skills and of relationships in supporting a woman to breastfeed. Organizational systems and services that facilitate continuity of caregiver, for example continuity of midwifery care or peer support models, are more likely to facilitate an authentic presence, involving supportive care and a trusting relationship with professionals. (BIRTH 38:1 March 2011)  相似文献   
996.
Abstract: Background: The World Health Organization (WHO) developed the Baby‐Friendly Hospital Initiative to improve hospital maternity care practices that support breastfeeding. In Hong Kong, although no hospitals have yet received the Baby‐Friendly status, efforts have been made to improve breastfeeding support. The aim of this study was to examine the impact of Baby‐Friendly hospital practices on breastfeeding duration. Methods: A sample of 1,242 breastfeeding mother‐infant pairs was recruited from four public hospitals in Hong Kong and followed up prospectively for up to 12 months. The primary outcome variable was defined as breastfeeding for 8 weeks or less. Predictor variables included six Baby‐Friendly practices: breastfeeding initiation within 1 hour of birth, exclusive breastfeeding while in hospital, rooming‐in, breastfeeding on demand, no pacifiers or artificial nipples, and information on breastfeeding support groups provided on discharge. Results: Only 46.6 percent of women breastfed for more than 8 weeks, and only 4.8 percent of mothers experienced all six Baby‐Friendly practices. After controlling for all other Baby‐Friendly practices and possible confounding variables, exclusive breastfeeding while in hospital was protective against early breastfeeding cessation (OR: 0.61; 95% CI: 0.42–0.88). Compared with mothers who experienced all six Baby‐Friendly practices, those who experienced one or fewer Baby‐Friendly practices were almost three times more likely to discontinue breastfeeding (OR: 3.13; 95% CI: 1.41–6.95). Conclusions: Greater exposure to Baby‐Friendly practices would substantially increase new mothers’ chances of breastfeeding beyond 8 weeks postpartum. To further improve maternity care practices in hospitals, institutional and administrative support are required to ensure all mothers receive adequate breastfeeding support in accordance with WHO guidelines. (BIRTH 38:3 September 2011)  相似文献   
997.
998.
999.
1000.

Objective

A multisite field trial testing whether improved outcomes associated with intensive referral to mutual help groups (MHGs) could be maintained after the intervention was adapted for the circumstances and needs of rural veterans in treatment for substance use disorder (SUD).

Methods

In three Veterans Affairs treatment programs in the Midwest, patients (N = 195) received standard referral (SR) or rural-adapted intensive referral (RAIR) and were measured at baseline and 6-month follow-up.

Results

Both groups reported significant improvement at 6-months, but no significant differences between SR and RAIR groups in MHG participation, substance use, addiction severity, and posttraumatic stress symptoms. Inconsistent delivery of the intervention resulted in only one-third of the RAIR group receiving the full three sessions, but this group reported significantly greater 6-month abstinence from alcohol than those receiving no sessions.

Conclusion

Further research should explore implementation problems and determine whether consistent delivery of the intervention enhances 12-step facilitation.

Practice implications

The addition of rural-specific elements to the original intensive referral intervention has not been shown to increase its effectiveness among rural veterans.  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