收费全文 | 1451762篇 |
免费 | 127839篇 |
国内免费 | 5272篇 |
耳鼻咽喉 | 19077篇 |
儿科学 | 47178篇 |
妇产科学 | 39387篇 |
基础医学 | 204199篇 |
口腔科学 | 41279篇 |
临床医学 | 156919篇 |
内科学 | 284270篇 |
皮肤病学 | 29880篇 |
神经病学 | 126074篇 |
特种医学 | 51983篇 |
外国民族医学 | 366篇 |
外科学 | 202699篇 |
综合类 | 29245篇 |
现状与发展 | 42篇 |
一般理论 | 543篇 |
预防医学 | 130238篇 |
眼科学 | 31318篇 |
药学 | 101922篇 |
6篇 | |
中国医学 | 3207篇 |
肿瘤学 | 85041篇 |
2021年 | 14637篇 |
2020年 | 12245篇 |
2019年 | 14607篇 |
2018年 | 23674篇 |
2017年 | 19723篇 |
2016年 | 21190篇 |
2015年 | 23190篇 |
2014年 | 31425篇 |
2013年 | 44391篇 |
2012年 | 50212篇 |
2011年 | 52698篇 |
2010年 | 34355篇 |
2009年 | 34048篇 |
2008年 | 47490篇 |
2007年 | 49108篇 |
2006年 | 49947篇 |
2005年 | 46915篇 |
2004年 | 44150篇 |
2003年 | 41609篇 |
2002年 | 40241篇 |
2001年 | 62638篇 |
2000年 | 63671篇 |
1999年 | 53939篇 |
1998年 | 16616篇 |
1997年 | 15050篇 |
1996年 | 14931篇 |
1995年 | 14025篇 |
1994年 | 12652篇 |
1993年 | 11806篇 |
1992年 | 42308篇 |
1991年 | 41376篇 |
1990年 | 39979篇 |
1989年 | 37832篇 |
1988年 | 35073篇 |
1987年 | 34074篇 |
1986年 | 32528篇 |
1985年 | 30950篇 |
1984年 | 23334篇 |
1983年 | 19905篇 |
1982年 | 11993篇 |
1979年 | 20914篇 |
1978年 | 14982篇 |
1977年 | 12208篇 |
1976年 | 11985篇 |
1975年 | 12209篇 |
1974年 | 14903篇 |
1973年 | 14545篇 |
1972年 | 13467篇 |
1971年 | 12496篇 |
1970年 | 11557篇 |
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Background
Rosacea is a chronic inflammatory skin condition whose etiology has been linked to mast cells and the antimicrobial peptide cathelicidin LL-37. Individuals with refractory disease have demonstrated clinical benefit with periodic injections of onabotulinum toxin, but the mechanism of action is unknown.Objectives
To investigate the molecular mechanism by which botulinum toxin improves rosacea lesions.Methods
Primary human and murine mast cells were pretreated with onabotulinum toxin A or B or control. Mast cell degranulation was evaluated by β-hexosaminidase activity. Expression of botulinum toxin receptor Sv2 was measured by qPCR. The presence of SNAP-25 and VAMP2 was established by immunofluorescence. In vivo rosacea model was established by intradermally injecting LL-37 with or without onabotulinum toxin A pretreatment. Mast cell degranulation was assessed in vivo by histologic counts. Rosacea biomarkers were analyzed by qPCR of mouse skin sections.Results
Onabotulinum toxin A and B inhibited compound 48/80-induced degranulation of both human and murine mast cells. Expression of Sv2 was established in mouse mast cells. Onabotulinum toxin A and B increased cleaved SNAP-25 and decreased VAMP2 staining in mast cells respectively. In mice, injection of onabotulinum toxin A significantly reduced LL-37-induced skin erythema, mast cell degranulation, and mRNA expression of rosacea biomarkers.Conclusions
These findings suggest that onabotulinum toxin reduces rosacea-associated skin inflammation by directly inhibiting mast cell degranulation. Periodic applications of onabotulinum toxin may be an effective therapy for refractory rosacea and deserves further study. 相似文献Methods: Tumour and surrounding tissue were modeled by elliptical two- and three-dimensional computational phantoms having six different nanoparticle distributions. Nanoparticles were modeled as point heat sources having amplitude-dependent loss power. The total number of nanoparticles was fixed, and their spatial distribution and heat output were varied. Heat transfer was computed by solving the Pennes’ bioheat equation using finite element methods (FEM) with temperature-dependent blood perfusion. Local temperature was regulated using a proportional-integral-derivative (PID) controller. Tissue temperature, thermal dose and tissue damage were calculated. The required minimum thermal dose delivered to the tumor was kept constant, and heating power was adjusted for comparison of both the heating methods.
Results: Modulated power heating produced lower and more homogeneous temperature distributions than did constant power heating for all studied nanoparticle distributions. For a concentrated nanoparticle distribution, located off-center within the tumor, the maximum temperatures inside the tumor were 16% lower for modulated power heating when compared to constant power heating. This resulted in less damage to surrounding normal tissue. Modulated power heating reached target thermal doses up to nine-fold more rapidly when compared to constant power heating.
Conclusions: Controlling the temperature at the tumor-healthy tissue boundary by modulating the heating power of magnetic nanoparticles demonstrably compensates for a variable nanoparticle distribution to deliver effective treatment. 相似文献