全文获取类型
收费全文 | 2268篇 |
免费 | 213篇 |
国内免费 | 28篇 |
专业分类
耳鼻咽喉 | 15篇 |
儿科学 | 47篇 |
妇产科学 | 31篇 |
基础医学 | 310篇 |
口腔科学 | 34篇 |
临床医学 | 264篇 |
内科学 | 548篇 |
皮肤病学 | 28篇 |
神经病学 | 152篇 |
特种医学 | 37篇 |
外科学 | 371篇 |
综合类 | 54篇 |
预防医学 | 153篇 |
眼科学 | 44篇 |
药学 | 159篇 |
中国医学 | 7篇 |
肿瘤学 | 255篇 |
出版年
2023年 | 18篇 |
2022年 | 32篇 |
2021年 | 66篇 |
2020年 | 42篇 |
2019年 | 63篇 |
2018年 | 57篇 |
2017年 | 43篇 |
2016年 | 49篇 |
2015年 | 68篇 |
2014年 | 86篇 |
2013年 | 91篇 |
2012年 | 161篇 |
2011年 | 173篇 |
2010年 | 98篇 |
2009年 | 93篇 |
2008年 | 150篇 |
2007年 | 158篇 |
2006年 | 154篇 |
2005年 | 142篇 |
2004年 | 130篇 |
2003年 | 103篇 |
2002年 | 110篇 |
2001年 | 76篇 |
2000年 | 44篇 |
1999年 | 44篇 |
1998年 | 23篇 |
1997年 | 19篇 |
1996年 | 9篇 |
1995年 | 11篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 17篇 |
1991年 | 14篇 |
1990年 | 20篇 |
1989年 | 19篇 |
1988年 | 12篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1976年 | 9篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1966年 | 2篇 |
排序方式: 共有2509条查询结果,搜索用时 15 毫秒
21.
Gatzoulis MA Freeman MA Siu SC Webb GD Harris L 《The New England journal of medicine》1999,340(11):839-846
BACKGROUND: Atrial flutter and atrial fibrillation are causes of morbidity in adults with an atrial septal defect. In this study, we attempted to identify risk factors for atrial flutter and fibrillation both before and after the surgical closure of an atrial septal defect. METHODS: We searched for preoperative and postoperative atrial flutter or fibrillation in 213 adult patients (82 men and 131 women) who underwent surgical closure of atrial septal defects because of symptoms, a substantial left-to-right shunt (ratio of pulmonary to systemic blood flow, >1.5:1), or both at Toronto Hospital between 1986 and 1997. RESULTS: Forty patients (19 percent) had sustained atrial flutter or fibrillation before surgery. As compared with the patients who did not have atrial flutter or fibrillation before surgery, those who did were older (59+/-11 vs. 37+/-13 years, P<0.001) and had higher mean pulmonary arterial pressures (25.0+/-9.7 vs. 19.7+/-8.2 mm Hg, P=0.001). There were no perioperative deaths. After a mean follow-up period of 3.8+/-2.5 years, 24 of the 40 patients (60 percent) continued to have atrial flutter or fibrillation. The mean age of these patients was greater than that of the 16 who converted to sinus rhythm (P=0.02). New-onset atrial flutter or atrial fibrillation was more likely to have developed at follow-up in patients who were older than 40 years at the time of surgery than in those who were 40 or younger (5 of 67 vs. 0 of 106, P=0.008). Late events (those occurring more than one month after surgery) included stroke in six patients (all but one with atrial flutter or fibrillation, one of whom died) and death from noncardiac causes in two patients. Multivariate analysis showed that older age (>40 years) at the time of surgery (P=0.001), the presence of preoperative atrial flutter or fibrillation (P<0.001), and the presence of postoperative atrial flutter or fibrillation or junctional rhythm (P=0.02) were predictive of late postoperative atrial flutter or fibrillation. CONCLUSIONS: The risk of atrial flutter or atrial fibrillation in adults with atrial septal defects is related to the age at the time of surgical repair and the pulmonary arterial pressure. To reduce the morbidity associated with atrial flutter and fibrillation, the timely closure of atrial septal defects is warranted. 相似文献
22.
23.
Mutation spectrum and genotype-phenotype analyses in Cowden disease and Bannayan-Zonana syndrome, two hamartoma syndromes with germline PTEN mutation 总被引:22,自引:1,他引:22
Marsh DJ; Coulon V; Lunetta KL; Rocca-Serra P; Dahia PL; Zheng Z; Liaw D; Caron S; Duboue B; Lin AY; Richardson AL; Bonnetblanc JM; Bressieux JM; Cabarrot-Moreau A; Chompret A; Demange L; Eeles RA; Yahanda AM; Fearon ER; Fricker JP; Gorlin RJ; Hodgson SV; Huson S; Lacombe D; Eng C 《Human molecular genetics》1998,7(3):507-515
The tumour suppressor gene PTEN , which maps to 10q23.3 and encodes a 403
amino acid dual specificity phosphatase (protein tyrosine phosphatase;
PTPase), was shown recently to play a broad role in human malignancy.
Somatic PTEN deletions and mutations were observed in sporadic breast,
brain, prostate and kidney cancer cell lines and in several primary tumours
such as endometrial carcinomas, malignant melanoma and thyroid tumours. In
addition, PTEN was identified as the susceptibility gene for two hamartoma
syndromes: Cowden disease (CD; MIM 158350) and Bannayan-Zonana (BZS) or
Ruvalcaba-Riley-Smith syndrome (MIM 153480). Constitutive DNA from 37 CD
families and seven BZS families was screened for germline PTEN mutations.
PTEN mutations were identified in 30 of 37 (81%) CD families, including
missense and nonsense point mutations, deletions, insertions, a
deletion/insertion and splice site mutations. These mutations were
scattered over the entire length of PTEN , with the exception of the first,
fourth and last exons. A 'hot spot' for PTEN mutation in CD was identified
in exon 5 that contains the PTPase core motif, with 13 of 30 (43%) CD
mutations identified in this exon. Seven of 30 (23%) were within the core
motif, the majority (five of seven) of which were missense mutations,
possibly pointing to the functional significance of this region. Germline
PTEN mutations were identified in four of seven (57%) BZS families studied.
Interestingly, none of these mutations was observed in the PTPase core
motif. It is also worthy of note that a single nonsense point mutation,
R233X, was observed in the germline DNA from two unrelated CD families and
one BZS family. Genotype-phenotype studies were not performed on this small
group of BZS families. However, genotype-phenotype analysis inthe group of
CD families revealed two possible associations worthy of follow-up in
independent analyses. The first was an association noted in the group of CD
families with breast disease. A correlation was observed between the
presence/absence of a PTEN mutation and the type of breast involvement
(unaffected versus benign versus malignant). Specifically and more
directly, an association was also observed between the presence of a PTEN
mutation and malignant breast disease. Secondly, there appeared to be an
interdependent association between mutations upstream and within the PTPase
core motif, the core motif containing the majority of missense mutations,
and the involvement of all major organ systems (central nervous system,
thyroid, breast, skin and gastrointestinal tract). However, these
observations would need to be confirmed by studying a larger number of CD
families.
相似文献
24.
Molecular genetic studies have pointed to a relationship between congenital lipodystrophy syndromes and some cardiac disorders. For instance, mutations in LMNA cause either lipodystrophy or cardiomyopathy, indicating that different mutations in the same gene can produce these clinical syndromes. The present authors describe a 10-year-old female with Berardinelli-Seip congenital complete lipodystrophy (MIM 606158) caused by homozygosity for a frameshift mutation in BSCL2. In addition to the typical attributes of complete lipodystrophy, this subject had hypertrophic cardiomyopathy diagnosed in the first year of her life; its progress has been followed with non-invasive imaging. The mechanism underlying the hypertrophic cardiomyopathy in complete lipodystrophy is unclear. It may result from a direct effect of the mutant gene or it might be secondary to the effects of hyperinsulinemia on cardiac development. The variability of the associated cardiomyopathy in patients with complete generalized lipodystrophy may be caused by differential effects of mutations in the same gene or of mutations in different genes which underlie the lipodystrophy phenotype. 相似文献
25.
Evaluation and Validation of an Enzyme-Linked Immunosorbent Assay and an Immunochromatographic Test for Serological Diagnosis of Severe Acute Respiratory Syndrome
下载免费PDF全文
![点击此处可从《Clinical and Vaccine Immunology : CVI》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ming Guan Kwok Hung Chan J. S. Malik Peiris See Wai Kwan Siu Yan Lam Chiu Mei Pang Ka Wing Chu Kit Man Chan Hsiao Ying Chen Ewe Beng Phuah Caiqin Jane Wong 《Clinical and Vaccine Immunology : CVI》2004,11(4):699-703
A newly developed severe acute respiratory syndrome (SARS)-specific enzyme-linked immunosorbent assay (ELISA) was further validated to confirm cutoff values and evaluate its diagnostic performance with clinical samples. In parallel, an immunochromatographic test was also evaluated. A total of 227 clinical serum specimens collected from SARS patients were used in the study, together with 385 samples from healthy donors. By use of an immunofluorescent (IF) test as the “gold standard, ” both the ELISA and the immunochromatographic test were able to detect immunoglobulin G antibodies to SARS not only from late-convalescent-stage samples (>21 days from the onset of clinical symptoms), as previously established, but also from early-acute-phase samples (1 to 10 days from onset). The ELISA, using an optical density (OD) of 0.25 as its cutoff value, produced the best sensitivity while maintaining high specificity. It detected SARS-specific antibodies in 58, 70, 75, and 95%, respectively, of the four groups of samples collected from patients 1 to 10 days, 11 to 20 days, 21 to 30 days, and more than 30 days after the onset of clinical symptoms. Similarly, the immunochromatographic test detected SARS-specific antibodies in 55, 68, 81, and 79% of the four groups, respectively. The overall specificities for the ELISA and the rapid test were 99.5 and 97.7%, respectively. Although the positive correlation observed between the ELISA OD values and the IF titers was moderate (r = 0.6915; P < 0.001), the detection rates of both the ELISA and the rapid test were found well in agreement with the IF titers. 相似文献
26.
Dynamic imaging of the lungs using x-ray phase contrast 总被引:4,自引:0,他引:4
Lewis RA Yagi N Kitchen MJ Morgan MJ Paganin D Siu KK Pavlov K Williams I Uesugi K Wallace MJ Hall CJ Whitley J Hooper SB 《Physics in medicine and biology》2005,50(21):5031-5040
High quality real-time imaging of lungs in vivo presents considerable challenges. We demonstrate here that phase contrast x-ray imaging is capable of dynamically imaging the lungs. It retains many of the advantages of simple x-ray imaging, whilst also being able to map weakly absorbing soft tissues based on refractive index differences. Preliminary results reported herein show that this novel imaging technique can identify and locate airway liquid and allows lung aeration in newborn rabbit pups to be dynamically visualized. 相似文献
27.
28.
A derivative chromosome 8 was observed in a newborn boy who presented with low birth weight, multiple congenital anomalies, and dysmorphic face. The der(8) was further characterized at age 18 months by a high resolution G-banding analysis, spectral karyotyping, and fluorescence in situ hybridization (FISH) with multiple DNA probes. The karyotype was described as 46,XY,der(8)(qter-->q24.13::p21.3-->p23.3::p23.3-->qter), representing an inverted duplication of region 8p21.3-->p23.3 and a duplication of region 8q24.13-->qter, which attaches to the duplicated short arm segment at 8p21.3. Different from previously reported patients with an inverted duplication (8p), no deletion was detected in the distal region of 8p in this case. This young child had manifested a broad nasal bridge, micrognathia, cleft lip, hydrocephalus, partial agenesis of the corpus callosum, Dandy-Walker malformation, congenital heart defects, dysplastic kidneys, hydronephrosis, marked hypotonia, and significant psychomotor retardation. These features are compared with those commonly seen in cases with an inverted duplication of 8p and cases with a partial trisomy of 8q. 相似文献
29.
Primary intraventricular hemorrhage in adults 总被引:1,自引:0,他引:1
P C Gates H J Barnett H V Vinters R L Simonsen K Siu 《Stroke; a journal of cerebral circulation》1986,17(5):872-877
Five adults with primary intraventricular hemorrhage are described. The presenting features included headache, confusion and drowsiness. Focal neurological signs were minimal or absent. All five had a history of hypertension, three patients had bilateral internal carotid occlusion at its origin, one had unilateral occlusion of the left internal carotid artery with severe stenosis of the contralateral siphon. Unilateral occlusion of the middle cerebral artery were present in the fifth patient. Pathological examination of the brain from one patient showed the presence of severe hemorrhagic "lacunar" infarcts adjacent to the left lateral ventricle, one showing direct continuity of blood in the lacune with the massive intraventricular hematoma. We hypothesize that such a finding illustrates one possible mechanism for this unusual type of hemorrhage. Patients with longstanding hypertension and severe occlusive disease of the internal carotid arteries may be predisposed to this unusual complication. 相似文献
30.
Kenneth Siu-Sing Leung Timothy Ting-Leung Ng Alan Ka-Lun Wu Miranda Chong-Yee Yau Hiu-Yin Lao Ming-Pan Choi Kingsley King-Gee Tam Lam-Kwong Lee Barry Kin-Chung Wong Alex Yat Man Ho Kam-Tong Yip Kwok-Cheung Lung Raymond Wai-To Liu Eugene Yuk-Keung Tso Wai-Shing Leung Man-Chun Chan Yuk-Yung Ng Kit-Man Sin Kitty Sau-Chun Fung Sandy Ka-Yee Chau Wing-Kin To Tak-Lun Que David Ho-Keung Shum Shea Ping Yip Wing Cheong Yam Gilman Kit-Hang Siu 《Emerging infectious diseases》2021,27(1):196
Initial cases of coronavirus disease in Hong Kong were imported from mainland China. A dramatic increase in case numbers was seen in February 2020. Most case-patients had no recent travel history, suggesting the presence of transmission chains in the local community. We collected demographic, clinical, and epidemiologic data from 50 patients, who accounted for 53.8% of total reported case-patients as of February 28, 2020. We performed whole-genome sequencing to determine phylogenetic relationship and transmission dynamics of severe acute respiratory syndrome coronavirus 2 infections. By using phylogenetic analysis, we attributed the community outbreak to 2 lineages; 1 harbored a common mutation, Orf3a-G251V, and accounted for 88.0% of the cases in our study. The estimated time to the most recent common ancestor of local coronavirus disease outbreak was December 24, 2019, with an evolutionary rate of 3.04 × 10−3 substitutions/site/year. The reproduction number was 1.84, indicating ongoing community spread. 相似文献