全文获取类型
收费全文 | 6253篇 |
免费 | 488篇 |
国内免费 | 11篇 |
专业分类
耳鼻咽喉 | 93篇 |
儿科学 | 178篇 |
妇产科学 | 143篇 |
基础医学 | 841篇 |
口腔科学 | 62篇 |
临床医学 | 747篇 |
内科学 | 1219篇 |
皮肤病学 | 73篇 |
神经病学 | 619篇 |
特种医学 | 127篇 |
外科学 | 789篇 |
综合类 | 45篇 |
一般理论 | 14篇 |
预防医学 | 724篇 |
眼科学 | 158篇 |
药学 | 507篇 |
中国医学 | 4篇 |
肿瘤学 | 409篇 |
出版年
2024年 | 9篇 |
2023年 | 73篇 |
2022年 | 117篇 |
2021年 | 291篇 |
2020年 | 153篇 |
2019年 | 227篇 |
2018年 | 236篇 |
2017年 | 191篇 |
2016年 | 199篇 |
2015年 | 234篇 |
2014年 | 299篇 |
2013年 | 439篇 |
2012年 | 599篇 |
2011年 | 554篇 |
2010年 | 260篇 |
2009年 | 257篇 |
2008年 | 422篇 |
2007年 | 418篇 |
2006年 | 368篇 |
2005年 | 372篇 |
2004年 | 276篇 |
2003年 | 200篇 |
2002年 | 202篇 |
2001年 | 31篇 |
2000年 | 17篇 |
1999年 | 15篇 |
1998年 | 37篇 |
1997年 | 16篇 |
1996年 | 16篇 |
1995年 | 13篇 |
1994年 | 12篇 |
1993年 | 18篇 |
1992年 | 17篇 |
1991年 | 10篇 |
1990年 | 15篇 |
1989年 | 8篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1981年 | 5篇 |
1978年 | 6篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1973年 | 6篇 |
1972年 | 4篇 |
1971年 | 4篇 |
1940年 | 4篇 |
排序方式: 共有6752条查询结果,搜索用时 15 毫秒
61.
Hung JH Fu CY Chen CY Chao KC Hung J 《The journal of obstetrics and gynaecology research》2008,34(4):518-523
Objective: The purpose of the present study was to build a database of reference ranges of fetal nasal bone length (NBL) in a Chinese population. The accuracy rate of detecting Down syndrome was also analyzed using fetal NBL as a marker.
Methods: The control group of fetuses included 342 normal singleton pregnancies with no chromosomal or congenital anomalies. The present study was a cross-section study and the control group was used to construct percentile values of NBL from 13 to 29 gestational weeks of age. Two-dimensional ultrasonography was used for the nasal bone studies. Measurements of NBL were collected and each fetus contributed a single value to the reference sample. During the study period, 14 fetuses with Down syndrome were examined. Measurement of fetal NBL was made during amniocentesis, with gestational age ranging from 13 to 19 weeks.
Results: From 342 normal fetuses with gestational age ranging from 13 to 29 weeks, reference ranges of NBL were constructed. The reference ranges were constructed from the 100(1 − p)% reference range: , where Ŷ = 25 − exp(3.58 − 0.044 × t + 0.0006 × t2 ), with Ŷ being the fitted mean of regression model and t being gestational age (weeks). Using fetal NBL, the regression model was Pr (Down syndrome) = exp( W )/[1 + exp( W )], where W = 0.62–4.80 × NBL (multiples of the median) in predicting Down syndrome. Fetal NBL was found to have a sensitivity and specificity of 0.78 and 0.78, respectively, in predicting Down syndrome in the second trimester of pregnancy.
Conclusions: Fetal NBL measurement can provide a simple and useful algorithm to predict Down syndrome during the second trimester of pregnancy. 相似文献
Methods: The control group of fetuses included 342 normal singleton pregnancies with no chromosomal or congenital anomalies. The present study was a cross-section study and the control group was used to construct percentile values of NBL from 13 to 29 gestational weeks of age. Two-dimensional ultrasonography was used for the nasal bone studies. Measurements of NBL were collected and each fetus contributed a single value to the reference sample. During the study period, 14 fetuses with Down syndrome were examined. Measurement of fetal NBL was made during amniocentesis, with gestational age ranging from 13 to 19 weeks.
Results: From 342 normal fetuses with gestational age ranging from 13 to 29 weeks, reference ranges of NBL were constructed. The reference ranges were constructed from the 100(1 − p)% reference range: , where Ŷ = 25 − exp(3.58 − 0.044 × t + 0.0006 × t
Conclusions: Fetal NBL measurement can provide a simple and useful algorithm to predict Down syndrome during the second trimester of pregnancy. 相似文献
62.
63.
Substandard application of preimplantation genetic screening may interfere with its clinical success
Munné S Gianaroli L Tur-Kaspa I Magli C Sandalinas M Grifo J Cram D Kahraman S Verlinsky Y Simpson JL 《Fertility and sterility》2007,88(4):781-784
The intent of this study was to evaluate a recent randomized clinical trial evaluating the effect of preimplantation genetic screening (PGS) that reports a negative effect on pregnancy outcome. This article reviews appropriate PGS techniques and how they differ from the trial in question. A closer look at the clinical trial in question reveals significant lack of expertise in biopsy, cell fixation, genetic analysis, and patient selection. At most, this trial demonstrates that in inexperienced hands, PGS can be detrimental. No other conclusions concerning the effect of PGS on pregnancy results can be drawn from the trial. 相似文献
64.
Nina Kurucz Jamie Lee McMahon Allan Warchot Glen Hewitson Jean Barcelon Frederick Moore Jasmin Moran Jessica J. Harrison Agathe M. G. Colmant Kyran M. Staunton Scott A. Ritchie Michael Townsend Dagmar Meyer Steiger Roy A. Hall Sally R. Isberg Sonja Hall-Mendelin 《Viruses》2022,14(6)
The Kunjin strain of West Nile virus (WNVKUN) is a mosquito-transmitted flavivirus that can infect farmed saltwater crocodiles in Australia and cause skin lesions that devalue the hides of harvested animals. We implemented a surveillance system using honey-baited nucleic acid preservation cards to monitor WNVKUN and another endemic flavivirus pathogen, Murray Valley encephalitis virus (MVEV), on crocodile farms in northern Australia. The traps were set between February 2018 and July 2020 on three crocodile farms in Darwin (Northern Territory) and one in Cairns (North Queensland) at fortnightly intervals with reduced trapping during the winter months. WNVKUN RNA was detected on all three crocodile farms near Darwin, predominantly between March and May of each year. Two of the NT crocodile farms also yielded the detection of MVE viral RNA sporadically spread between April and November in 2018 and 2020. In contrast, no viral RNA was detected on crocodile farms in Cairns during the entire trapping period. The detection of WNVKUN and MVEV transmission by FTATM cards on farms in the Northern Territory generally correlated with the detection of their transmission to sentinel chicken flocks in nearby localities around Darwin as part of a separate public health surveillance program. While no isolates of WNVKUN or MVEV were obtained from mosquitoes collected on Darwin crocodile farms immediately following the FTATM card detections, we did isolate another flavivirus, Kokobera virus (KOKV), from Culex annulirostris mosquitoes. Our studies support the use of the FTATM card system as a sensitive and accurate method to monitor the transmission of WNVKUN and other arboviruses on crocodile farms to enable the timely implementation of mosquito control measures. Our detection of MVEV transmission and isolation of KOKV from mosquitoes also warrants further investigation of their potential role in causing diseases in crocodiles and highlights a “One Health” issue concerning arbovirus transmission to crocodile farm workers. In this context, the introduction of FTATM cards onto crocodile farms appears to provide an additional surveillance tool to detect arbovirus transmission in the Darwin region, allowing for a more timely intervention of vector control by relevant authorities. 相似文献
65.
Background
Previous literature suggests that individuals with disabilities have increased rates of obesity and decreased participation in physical activity contributing to overall higher incidence of secondary health conditions compared to the general population without disabilities.Objective/hypothesis
The purpose of this research study was to examine the differences in physical activity rates for college students with Attention Deficit Hyperactivity Disorder (ADHD) and Learning Disabilities (LD).Methods
A secondary analysis was utilized to examine differences in physical activity rates based on disability, gender, and factors influencing participation in physical activity. The 2011 Fall National College Health Assessment was used as the reference group with a sample of 27,774 students. Multiple independent samples t-tests were utilized in this research.Results
The results of this study indicated that physical activity for college students with disabilities does not have significant variations compared to those without disabilities. However, gender influences participation in physical activity for this population.Conclusions
This research helps in narrowing the research gap in this topic through analysis of the college population with ADHD and LD. This paper concludes with implications that could benefit the health status of this population. 相似文献66.
Daniel R. Taber Jamie F. Chriqui Frank M. Perna Lisa M. Powell Sandy J. Slater Frank J. Chaloupka 《Preventive medicine》2013
Objective
To determine if state physical education (PE) laws are associated with student physical education attendance and physical activity (PA), and whether physical education and competitive food laws, in conjunction, are associated with lower BMI change.Method
State laws regarding physical education time requirements and competitive foods in 2003 and 2006 were classified as strong, weak, or none, based on codified law ratings obtained from the Classification of Laws Associated with School Students. Laws were linked to student data on PE attendance and physical activity (8th grade, Spring 2007) and BMI change (5th–8th grade, 2004–2007), obtained from the Early Childhood Longitudinal Study (n = 5510 students in 40 states).Results
Girls reported 0.31 more days of activity (95% CI: 0.02, 0.61) and were more likely to attend physical education ≥ 3 days/week (74.1% versus 52.1%, difference = 22.0, 95% CI: 2.1, 42.0) if they resided in states with strong physical education laws compared to no physical education laws. Weak physical education laws had modest associations with PE and activity, and there was no evidence that weak laws reduce BMI gain regardless of competitive food laws.Conclusion
Strong physical education laws with specific time requirements may increase physical education attendance and activity in girls. There is insufficient evidence that physical education laws reduce student weight gain. 相似文献67.
Jamie Lütscher Christa Hauswirth Siegenthaler Caroline Hertler David Blum Paul Windisch Renate Grathwohl Shaker Christina Schrder Daniel Rudolf Zwahlen 《Current oncology (Toronto, Ont.)》2022,29(6):4235
Cancer burdens not only the patients themselves but also their personal environment. A few studies have already focused on the mental health and personal needs of caregivers of patients. The purpose of this retrospective analysis was to further assess the emotional burden and unmet needs for support of caregivers in a population of brain metastasis patients. In the time period 2013–2020, we identified 42 informal caregivers of their respective patients after palliative radiation treatment for brain metastases. The caregivers completed two standardized questionnaires about different treatment aspects, their emotional burden, and unmet needs for support. Involvement of psycho-oncology and palliative care was examined in a chart review. The majority of the caregivers (71.4%, n = 30) suffered from high emotional burden during cancer treatment of their relatives and showed unmet needs for emotional and psychosocial support, mostly referring to information needs and the involvement in the patient’s treatment decisions. Other unmet needs referred to handling personal needs and fears of dealing with the sick cancer patient in terms of practical care tasks and appropriate communication. Palliative care was involved in 30 cases and psycho-oncology in 12 cases. There is a high need for emotional and psychosocial support in informal caregivers of cancer patients. There might still be room for an improvement of psychosocial and psycho-oncological support. Care planning should cater to the emotional burden and unmet needs of informal caregivers as well. Further prospective studies in larger samples should be performed in order to confirm this analysis. 相似文献
68.
Sanja Budisavljevic Jamie M. Kawadler Flavio Dell'Acqua Frühling V. Rijsdijk Fergus Kane Marco Picchioni Philip McGuire Timothea Toulopoulou Anna Georgiades Sridevi Kalidindi Eugenia Kravariti Robin M. Murray Declan G. Murphy Michael C. Craig Marco Catani 《Social cognitive and affective neuroscience》2016,11(5):746-757
Individual differences in cognitive ability and social behaviour are influenced by the variability in the structure and function of the limbic system. A strong heritability of the limbic cortex has been previously reported, but little is known about how genetic factors influence specific limbic networks. We used diffusion tensor imaging tractography to investigate heritability of different limbic tracts in 52 monozygotic and 34 dizygotic healthy adult twins. We explored the connections that contribute to the activity of three distinct functional limbic networks, namely the dorsal cingulum (‘medial default-mode network’), the ventral cingulum and the fornix (‘hippocampal-diencephalic-retrosplenial network’) and the uncinate fasciculus (‘temporo-amygdala-orbitofrontal network’). Genetic and environmental variances were mapped for multiple tract-specific measures that reflect different aspects of the underlying anatomy. We report the highest heritability for the uncinate fasciculus, a tract that underpins emotion processing, semantic cognition, and social behaviour. High to moderate genetic and shared environmental effects were found for pathways important for social behaviour and memory, for example, fornix, dorsal and ventral cingulum. These findings indicate that within the limbic system inheritance of specific traits may rely on the anatomy of distinct networks and is higher for fronto-temporal pathways dedicated to complex social behaviour and emotional processing. 相似文献
69.
70.
Steve Dingwall Jung Bok Lee Borhane Guezguez Aline Fiebig Jamie McNicol Douglas Boreham Tony J. Collins Mick Bhatia 《Oncotarget》2015,6(26):22258-22269
Studies have implicated that a small sub-population of cells within a tumour, termed cancer stem cells (CSCs), have an enhanced capacity for tumour formation in multiple cancers and may be responsible for recurrence of the disease after treatment, including radiation. Although comparisons have been made between CSCs and bulk-tumour, the more important comparison with respect to therapy is between tumour-sustaining CSC versus normal stem cells that maintain the healthy tissue. However, the absence of normal known counterparts for many CSCs has made it difficult to compare the radiation responses of CSCs with the normal stem cells required for post-radiotherapy tissue regeneration and the maintenance of tissue homeostasis. Here we demonstrate that transformed human embryonic stem cells (t-hESCs), showing features of neoplastic progression produce tumours resistant to radiation relative to their normal counterpart upon injection into immune compromised mice. We reveal that t-hESCs have a reduced capacity for radiation induced cell death via apoptosis and exhibit altered cell cycle arrest relative to hESCs in vitro. t-hESCs have an increased expression of BclXL in comparison to their normal counterparts and re-sensitization of t-hESCs to radiation upon addition of BH3-only mimetic ABT737, suggesting that overexpression of BclXL underpins t-hESC radiation insensitivity. Using this novel discovery platform to investigate radiation resistance in human CSCs, our study indicates that chemotherapy targeting Bcl2-family members may prove to be an adjuvant to radiotherapy capable of targeting CSCs. 相似文献