全文获取类型
收费全文 | 2530篇 |
免费 | 153篇 |
国内免费 | 11篇 |
专业分类
耳鼻咽喉 | 16篇 |
儿科学 | 158篇 |
妇产科学 | 66篇 |
基础医学 | 341篇 |
口腔科学 | 80篇 |
临床医学 | 234篇 |
内科学 | 395篇 |
皮肤病学 | 46篇 |
神经病学 | 448篇 |
特种医学 | 86篇 |
外科学 | 256篇 |
综合类 | 6篇 |
预防医学 | 270篇 |
眼科学 | 21篇 |
药学 | 79篇 |
中国医学 | 5篇 |
肿瘤学 | 187篇 |
出版年
2024年 | 5篇 |
2023年 | 19篇 |
2022年 | 31篇 |
2021年 | 51篇 |
2020年 | 52篇 |
2019年 | 47篇 |
2018年 | 66篇 |
2017年 | 51篇 |
2016年 | 74篇 |
2015年 | 82篇 |
2014年 | 84篇 |
2013年 | 110篇 |
2012年 | 141篇 |
2011年 | 162篇 |
2010年 | 101篇 |
2009年 | 82篇 |
2008年 | 122篇 |
2007年 | 154篇 |
2006年 | 142篇 |
2005年 | 153篇 |
2004年 | 109篇 |
2003年 | 99篇 |
2002年 | 114篇 |
2001年 | 47篇 |
2000年 | 49篇 |
1999年 | 44篇 |
1998年 | 25篇 |
1997年 | 22篇 |
1996年 | 31篇 |
1995年 | 23篇 |
1994年 | 14篇 |
1993年 | 14篇 |
1992年 | 33篇 |
1991年 | 24篇 |
1990年 | 29篇 |
1989年 | 35篇 |
1988年 | 26篇 |
1987年 | 29篇 |
1986年 | 22篇 |
1985年 | 26篇 |
1984年 | 26篇 |
1983年 | 31篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 16篇 |
1978年 | 7篇 |
1974年 | 5篇 |
1968年 | 5篇 |
1967年 | 6篇 |
排序方式: 共有2694条查询结果,搜索用时 14 毫秒
71.
Susan M.R. Gurney Sandra Schneider René Pflugradt Elizabeth Barrett Anna Catharina Forster Bernd Brinkmann Thomas Jansen Peter Forster 《International journal of legal medicine》2010,124(6):617-622
Horse mtDNA profiling can be useful in forensic work investigating degraded samples, hair shafts or highly dilute samples. Degraded DNA often does not allow sequencing of fragments longer than 200 nucleotides. In this study we therefore search for the most discriminatory sections within the hypervariable horse mtDNA control region. Among a random sample of 39 horses, 32 different sequences were identified in a stretch of 921 nucleotides. The sequences were assigned to the published mtDNA types A–G, and to a newly labelled minor type H. The random match probability within the analysed samples is 3.61%, and the average pairwise sequence difference is 15 nucleotides. In a “sliding window” analysis of 200-nucleotide sections of the mtDNA control region, we find that the known repetitive central motif divides the mtDNA control region into a highly diverse segment and a markedly less discriminatory segment. 相似文献
72.
Laurent Frossard David Lee Gow Kerstin Hagberg Nicola Cairns Bill Contoyannis Steven Gray Richard Brånemark Mark Pearcy 《Gait & posture》2010,31(2):223-228
The purpose of this proof-of-concept study was to determine the relevance of direct measurements to monitor the load applied on the osseointegrated fixation of transfemoral amputees during static load bearing exercises. The objectives were (A) to introduce an apparatus using a three-dimensional load transducer, (B) to present a range of derived information relevant to clinicians, (C) to report on the outcomes of a pilot study and (D) to compare the measurements from the transducer with those from the current method using a weighing scale. One transfemoral amputee fitted with an osseointegrated implant was asked to apply 10 kg, 20 kg, 40 kg and 80 kg on the fixation, using self-monitoring with the weighing scale. The loading was directly measured with a portable kinetic system including a six-channel transducer, external interface circuitry and a laptop. As the load prescribed increased from 10 kg to 80 kg, the forces and moments applied on and around the antero-posterior axis increased by four-fold anteriorly and 14-fold medially, respectively. The forces and moments applied on and around the medio-lateral axis increased by nine-fold laterally and 16-fold from anterior to posterior, respectively. The long axis of the fixation was overloaded and underloaded in 17% and 83% of the trials, respectively, by up to ±10%. This proof-of-concept study presents an apparatus that can be used by clinicians facing the challenge of improving basic knowledge on osseointegration, for the design of equipment for load bearing exercises and for rehabilitation programs. 相似文献
73.
Cerebral palsy in preterm infants: a population-based case-control study of antenatal and intrapartal risk factors 总被引:1,自引:0,他引:1
Jacobsson B Hagberg G Hagberg B Ladfors L Niklasson A Hagberg H 《Acta paediatrica (Oslo, Norway : 1992)》2002,91(8):946-951
Previous studies have indicated that foetomaternal infection increases the risk of spastic cerebral palsy (CP) in term infants, whereas this association appears to be less evident in preterm infants. The aim of this study was to analyse infection-related risk factors for spastic CP in preterm infants. A population-based series of preterm infants with spastic CP, 91 very preterm (<32 wk) and 57 moderately preterm (32-36 wk), born in 1983-90, were included and matched with a control group (n = 296). In total, 154 maternal, antenatal and intrapartal variables were retrieved from obstetric records. In the entire group, histological chorioamnionitis/pyelonephritis, long interval between rupture of membranes and birth, admission-delivery interval <4 h and Apgar scores of <7 at 1 min just significantly increased the risk of CP, and Apgar scores of <7 at 5 and 10 min were strongly associated with an increased risk. Abruptio placentae, Apgar scores <7 at 1 min and pathological non-stress test (reason for delivery) were significant risk factors of CP only in the moderately preterm and hemiplegic groups, whereas fever before delivery was a significant risk factor in the very preterm and spastic diplegic groups. Antibiotics during pregnancy was associated with CP only in the spastic diplegic CP group. Conclusion: Antenatal infections marginally increased the risk of CP. Low Apgar score and abruptio placentae were associated with CP, especially in moderately preterm infants with hemiplegic CP. 相似文献
74.
75.
Disruption of interleukin-18, but not interleukin-1, increases vulnerability to preterm delivery and fetal mortality after intrauterine inflammation 下载免费PDF全文
Wang X Hagberg H Mallard C Zhu C Hedtjärn M Tiger CF Eriksson K Rosen A Jacobsson B 《The American journal of pathology》2006,169(3):967-976
Preterm birth is a major contributor of adverse perinatal outcome. Clinical data suggest that an inflammatory response is important in the process leading to preterm labor. By using a recently introduced mouse model of localized intrauterine lipopolysaccharide-induced inflammation, the effect of interleukin (IL)-18 gene disruption and/or IL-18 neutralization as well as combined IL-1alpha/beta gene disruption on inflammation-induced fetal loss was investigated. The frequency of preterm fetal loss was significantly higher in IL-18 knockout mice (58.9%) and in mice administered IL-18-binding protein (59.7%) compared to wild-type controls (34.7%). The rate of fetal loss was not affected by IL-1alpha/beta gene deficiency (38.7%). Decreased IL-18 protein expression combined with elevated IL-12 protein expression in uterine tissue of IL-18 knockout mice and IL-18-binding protein-treated animals was noticed. These data demonstrate that preterm pregnancy loss in response to intrauterine inflammation was enhanced by disruption of the IL-18 gene and/or IL-18 neutralization, events that may relate to exaggerated Th1 responses because of an increased IL-12/IL-18 ratio. 相似文献
76.
Heart rate and reinforcement sensitivity in ADHD 总被引:1,自引:0,他引:1
Luman M Oosterlaan J Hyde C van Meel CS Sergeant JA 《Journal of child psychology and psychiatry, and allied disciplines》2007,48(9):890-898
BACKGROUND: Both theoretical and clinical accounts of attention-deficit/hyperactivity disorder (ADHD) implicate a dysfunctional reinforcement system. This study investigated heart rate parameters in response to feedback associated with reward and response cost in ADHD children and controls aged 8 to 12. METHODS: Heart rate responses (HRRs) following feedback and heart rate variability (HRV) in the low frequency band (.04-.08 Hz), a measure of mental effort, were calculated during a time production paradigm. Performance was coupled to monetary gain, loss or feedback-only in a cross-over design. RESULTS: Children with ADHD exhibited smaller HRRs to feedback compared to controls. HRV of children with ADHD decreased when performance was coupled to reward or response cost compared to feedback-only. HRV of controls was similar across conditions. CONCLUSIONS: Children with ADHD were characterised by (a) possible abnormalities in feedback monitoring and (b) motivational deficits, when no external reinforcement is present. 相似文献
77.
After allogeneic hematopoietic stem-cell transplantation (allo-HSCT), EBV infections can be potentially dangerous and even life threatening. We evaluated the EBV viremia in 80 consecutive allo-HSCT with quantitative EBV-PCR every 2 weeks during the first 3 months and monthly thereafter until 1 yr after allo-HSCT or until death. We found a significantly more frequent viremia in patients who had in vivo T-cell depletion in which 23 out of 51 (45%) had EBV-PCR positivity. The EBV virus load was also significantly higher in the in vivo T-cell depleted group. Three patients developed clinical symptoms of EBV-PTLD and were treated with monoclonal anti-CD20 antibodies. No EBV- driven mortality was seen in this cohort. In our opinion EBV-PCR monitoring is mandatory after allo-HSCT. Most of the patients with EBV viremia had a good evolution after tapering the immune suppression, so this should be the first-line management of pediatric patients with EBV viremia. Monoclonal anti-CD20 antibodies should be reserved for those patients with early symptoms of EBV-PTLD. 相似文献
78.
Chromosomal imbalances in diffuse large B-cell lymphoma detected by comparative genomic hybridization. 总被引:7,自引:0,他引:7
Mattias Berglund Gunilla Enblad Emma Flordal Weng-Onn Lui Carin Backlin Ulf Thunberg Christer Sundstr?m G?ran Roos Susanne V Allander Martin Erlanson Richard Rosenquist Catharina Larsson Svetlana Lagercrantz 《Modern pathology》2002,15(8):807-816
Diffuse large B-cell lymphoma (DLBCL) is the most common form of non-Hodgkin lymphoma. In contrast to many other hematological malignancies, no chromosomal abnormalities with a diagnostic or prognostic value have been identified in DLBCL. Numerical chromosomal imbalances were characterized by comparative genomic hybridization (CGH) performed on 54 DLBCL tumors from a total of 40 patients. The clonal relatedness was demonstrated in 9 of 11 pairs of matched diagnostic tumors and their relapses as determined by IGH gene rearrangement analysis and/or the CGH profiles. Furthermore, immunohistochemical expression analyses of BCL2 and BCL6/LAZ3 were performed on all cases. Copy number changes were detected in 94% of the diagnostic tumor samples and in all of the relapses. Chromosomal losses in diagnostic tumors were preferentially observed at 8p22-pter (29%), 1p34-pter (26%), 6q23-qter (20%), 17p12-pter (17%) and 22q (17%), 9p23-pter (14%), whereas gains were mainly seen in Xq25-26 (43%), 13q22 (26%), 12cen-q14 (20%), 3q24-25 (11%), 7 (11%), and 18q12-21 (11%). Loss of 22q was significantly more commonly seen in the diagnostic tumor samples with more advanced clinical stage in other words, Stage III-IV compared with Stage I-II, and band 18q21 was significantly more often gained in relapses as compared to diagnostic tumors. None of the recurrent alterations were detected as a single abnormality, suggesting that other genetic lesions below the detection level of CGH may be the initiating event in the tumorigenesis of DLBCL. However, the distribution of CGH alterations support the idea of a progression of genetic events where loss of 8p and 9p and gain of 3q, 13q, and 18q would represent relatively early events because they were distributed in tumors with only two abnormalities. 相似文献
79.
Older and younger aerobically trained and sedentary adults participated in an S1-S2-S3 paradigm designed to elicit event-related potential (ERP) and behavioral responses to determine the influence of cardiovascular fitness on cognitive and motor processes. The paradigm provided warning (S1) as to the difficulty level of an upcoming decision task (S2). Participants had to decide the taller of two bars on presentation of S2 but hold their response until S3, to which they indicated their choice motorically. Results revealed age-related differences for ERP measures as older participants showed increased amplitude of the stimulus preceding negativity (SPN) prior to S2, and longer latencies and equipotentiality of P3 in response to S2. Fitness effects were also observed for the contingent negative variation (CNV) with decreased amplitude for fit relative to sedentary individuals. Age interacted with fitness for P3 latency to S2 as older sedentary individuals showed the longest latency followed by older fit and both younger groups. No significant group differences were observed for reaction time (RT) to S3. Therefore, physical fitness is associated with attenuation of cognitive decline in older individuals and greater economy of motor preparation for both young and older participants. 相似文献
80.
A well-known issue in functional neuroimaging studies, regarding motor synchronization, is to design suitable control tasks able to discriminate between the brain structures involved in primary time-keeper functions and those related to other processes such as attentional effort. The aim of this work was to investigate how the predictability of stimulus onsets in the baseline condition modulates the activity in brain structures related to processes involved in time-keeper functions during the performance of a visually cued motor synchronization task (VM). The rational behind this choice derives from the notion that using different stimulus predictability can vary the subject's attention and the consequently neural activity. For this purpose, baseline levels of BOLD activity were obtained from 12 subjects during a conventional-baseline condition: maintained fixation of the visual rhythmic stimuli presented in the VM task, and a random-baseline condition: maintained fixation of visual stimuli occurring randomly. fMRI analysis demonstrated that while brain areas with a documented role in basic time processing are detected independent of the baseline condition (right cerebellum, bilateral putamen, left thalamus, left superior temporal gyrus, left sensorimotor cortex, left dorsal premotor cortex and supplementary motor area), the ventral premotor cortex, caudate nucleus, insula and inferior frontal gyrus exhibited a baseline-dependent activation. We conclude that maintained fixation of unpredictable visual stimuli can be employed in order to reduce or eliminate neural activity related to attentional components present in the synchronization task. 相似文献