全文获取类型
收费全文 | 64524篇 |
免费 | 4525篇 |
国内免费 | 236篇 |
专业分类
耳鼻咽喉 | 747篇 |
儿科学 | 1329篇 |
妇产科学 | 932篇 |
基础医学 | 8502篇 |
口腔科学 | 874篇 |
临床医学 | 5912篇 |
内科学 | 15111篇 |
皮肤病学 | 696篇 |
神经病学 | 6450篇 |
特种医学 | 2589篇 |
外国民族医学 | 1篇 |
外科学 | 10307篇 |
综合类 | 692篇 |
一般理论 | 69篇 |
预防医学 | 4458篇 |
眼科学 | 1201篇 |
药学 | 4261篇 |
中国医学 | 93篇 |
肿瘤学 | 5061篇 |
出版年
2023年 | 320篇 |
2022年 | 551篇 |
2021年 | 1640篇 |
2020年 | 1058篇 |
2019年 | 1517篇 |
2018年 | 1907篇 |
2017年 | 1278篇 |
2016年 | 1406篇 |
2015年 | 1693篇 |
2014年 | 2496篇 |
2013年 | 3016篇 |
2012年 | 5063篇 |
2011年 | 5092篇 |
2010年 | 2879篇 |
2009年 | 2592篇 |
2008年 | 4514篇 |
2007年 | 4665篇 |
2006年 | 4534篇 |
2005年 | 4475篇 |
2004年 | 4037篇 |
2003年 | 3700篇 |
2002年 | 3371篇 |
2001年 | 481篇 |
2000年 | 335篇 |
1999年 | 484篇 |
1998年 | 647篇 |
1997年 | 564篇 |
1996年 | 470篇 |
1995年 | 424篇 |
1994年 | 335篇 |
1993年 | 322篇 |
1992年 | 247篇 |
1991年 | 221篇 |
1990年 | 190篇 |
1989年 | 191篇 |
1988年 | 146篇 |
1987年 | 126篇 |
1986年 | 148篇 |
1985年 | 173篇 |
1984年 | 193篇 |
1983年 | 176篇 |
1982年 | 200篇 |
1981年 | 166篇 |
1980年 | 139篇 |
1979年 | 80篇 |
1978年 | 89篇 |
1977年 | 88篇 |
1976年 | 73篇 |
1975年 | 69篇 |
1973年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Ingmar Fleps Pierre Guy Stephen J Ferguson Peter A Cripton Benedikt Helgason 《Journal of bone and mineral research》2019,34(10):1837-1850
The majority of hip fractures in the elderly are the result of a fall from standing or from a lower height. Current injury models focus mostly on femur strength while neglecting subject-specific loading. This article presents an injury modeling strategy for hip fractures related to sideways falls that takes subject-specific impact loading into account. Finite element models (FEMs) of the human body were used to predict the experienced load and the femoral strength in a single model. We validated these models for their predicted peak force, effective pelvic stiffness, and fracture status against matching ex vivo sideways fall impacts (n = 11) with a trochanter velocity of 3.1 m/s. Furthermore, they were compared to sideways impacts of volunteers with lower impact velocities that were previously conducted by other groups. Good agreement was found between the ex vivo experiments and the FEMs with respect to peak force (root mean square error [RMSE] = 10.7%, R2 = 0.85) and effective pelvic stiffness (R2 = 0.92, RMSE = 12.9%). The FEMs were predictive of the fracture status for 10 out of 11 specimens. Compared to the volunteer experiments from low height, the FEMs overestimated the peak force by 25% for low BMI subjects and 8% for high BMI subjects. The effective pelvic stiffness values that were derived from the FEMs were comparable to those derived from impacts with volunteers. The force attenuation from the impact surface to the femur ranged between 27% and 54% and was highly dependent on soft tissue thickness (R2 = 0.86). The energy balance in the FEMS showed that at the time of peak force 79% to 93% of the total energy is either kinetic or was transformed to soft tissue deformation. The presented FEMs allow for direct discrimination between fracture and nonfracture outcome for sideways falls and bridge the gap between impact testing with volunteers and impact conditions representative of real life falls. © 2019 American Society for Bone and Mineral Research. 相似文献
2.
Aaron Pitzele Mohammad Rahimi Eric Armbrecht 《The journal of maternal-fetal & neonatal medicine》2015,28(15):1770-1773
Objective: To determine whether packed red blood cell (PRBC) transfusion affects post-prandial superior mesenteric artery blood flow velocities (SMA BFVs) in very-low birth weight (VLBW) neonates and if so, at what time point after transfusion restoration of previous SMA BFV patterns occurs.Design/Methods: VLBW pre-term neonates, older than 14 days and tolerating bolus enteral feedings administered every 3?h were enrolled in this prospective observational study. Pulsed Doppler ultrasound was used to measure pre- and post-prandial (at 45?min) time-averaged mean, peak and end diastolic velocities (TAMV, PSV, EDV) immediately before and after 15?ml/kg of PRBC transfusion was given over 3?h; patent ductus arteriosus (PDA) status was also evaluated. Subsequent pre- and post-prandial SMA BFVs were recorded 24 and 48?h after the transfusion.Results: Pre- and post-prandial measurements were obtained for 21 out of 25 enrolled infants. Post-prandial SMA BFVs were attenuated during the feedings immediately after transfusion; at 24 and 48?h after transfusion, changes in post-prandial SMA BFVs were similar to those measured prior to transfusion; the presence of the PDA did not affect results.Conclusions: PRBC transfusion blunted SMA BFV responses to feedings immediately after the transfusion with normalization observed 24?h post-transfusion. 相似文献
3.
4.
Danielle E Whittier Elizabeth J Samelson Marian T Hannan Lauren A Burt David A Hanley Emmanuel Biver Pawel Szulc Elisabeth Sornay-Rendu Blandine Merle Roland Chapurlat Eric Lespessailles Andy Kin On Wong David Goltzman Sundeep Khosla Serge Ferrari Mary L Bouxsein Douglas P Kiel Steven K Boyd 《Journal of bone and mineral research》2022,37(3):428-439
Prevalence of osteoporosis is more than 50% in older adults, yet current clinical methods for diagnosis that rely on areal bone mineral density (aBMD) fail to detect most individuals who have a fragility fracture. Bone fragility can manifest in different forms, and a “one-size-fits-all” approach to diagnosis and management of osteoporosis may not be suitable. High-resolution peripheral quantitative computed tomography (HR-pQCT) provides additive information by capturing information about volumetric density and microarchitecture, but interpretation is challenging because of the complex interactions between the numerous properties measured. In this study, we propose that there are common combinations of bone properties, referred to as phenotypes, that are predisposed to different levels of fracture risk. Using HR-pQCT data from a multinational cohort (n = 5873, 71% female) between 40 and 96 years of age, we employed fuzzy c-means clustering, an unsupervised machine-learning method, to identify phenotypes of bone microarchitecture. Three clusters were identified, and using partial correlation analysis of HR-pQCT parameters, we characterized the clusters as low density, low volume, and healthy bone phenotypes. Most males were associated with the healthy bone phenotype, whereas females were more often associated with the low volume or low density bone phenotypes. Each phenotype had a significantly different cumulative hazard of major osteoporotic fracture (MOF) and of any incident osteoporotic fracture (p < 0.05). After adjustment for covariates (cohort, sex, and age), the low density followed by the low volume phenotype had the highest association with MOF (hazard ratio = 2.96 and 2.35, respectively), and significant associations were maintained when additionally adjusted for femoral neck aBMD (hazard ratio = 1.69 and 1.90, respectively). Further, within each phenotype, different imaging biomarkers of fracture were identified. These findings suggest that osteoporotic fracture risk is associated with bone phenotypes that capture key features of bone deterioration that are not distinguishable by aBMD. © 2021 American Society for Bone and Mineral Research (ASBMR). 相似文献
5.
6.
Benyam Kinde Harrison W. Gabel Caitlin S. Gilbert Eric C. Griffith Michael E. Greenberg 《Proceedings of the National Academy of Sciences of the United States of America》2015,112(22):6800-6806
DNA methylation at CpG dinucleotides is an important epigenetic regulator common to virtually all mammalian cell types, but recent evidence indicates that during early postnatal development neuronal genomes also accumulate uniquely high levels of two alternative forms of methylation, non-CpG methylation and hydroxymethylation. Here we discuss the distinct landscape of DNA methylation in neurons, how it is established, and how it might affect the binding and function of protein readers of DNA methylation. We review studies of one critical reader of DNA methylation in the brain, the Rett syndrome protein methyl CpG-binding protein 2 (MeCP2), and discuss how differential binding affinity of MeCP2 for non-CpG and hydroxymethylation may affect the function of this methyl-binding protein in the nervous system. 相似文献
7.
8.
9.
Eric S. Zhou Larissa Nekhlyudov Sharon L. Bober 《Translational andrology and urology》2015,4(2):218-231
There is a large and growing population of long-term cancer survivors. Primary care physicians (PCPs) are playing an increasingly greater role in the care of these patients across the continuum of cancer survivorship. In this role, PCPs are faced with the responsibility of managing a range of medical and psychosocial late effects of cancer treatment. In particular, the sexual side effects of treatment which are common and have significant impact on quality of life for the cancer survivor, often go unaddressed. This is an area of clinical care and research that has received increasing attention, highlighted by the presentation of this special issue on Cancer and Sexual Health. The aims of this review are 3-fold. First, we seek to overview common presentations of sexual dysfunction related to major cancer diagnoses in order to give the PCP a sense of the medical issues that the survivor may present with. Barriers to communication about sexual health issues between patient/PCPs in order are also described in order to emphasize the importance of PCPs initiating this important conversation. Next, we provide strategies and resources to help guide the PCP in the management of sexual dysfunction in cancer survivors. Finally, we discuss case examples of survivorship sexual health issues and highlight the role that a PCP can play in each of these case examples. 相似文献
10.