全文获取类型
收费全文 | 9456篇 |
免费 | 739篇 |
国内免费 | 61篇 |
专业分类
耳鼻咽喉 | 66篇 |
儿科学 | 354篇 |
妇产科学 | 304篇 |
基础医学 | 1207篇 |
口腔科学 | 292篇 |
临床医学 | 867篇 |
内科学 | 1886篇 |
皮肤病学 | 107篇 |
神经病学 | 544篇 |
特种医学 | 341篇 |
外科学 | 1549篇 |
综合类 | 446篇 |
一般理论 | 10篇 |
预防医学 | 444篇 |
眼科学 | 341篇 |
药学 | 482篇 |
1篇 | |
中国医学 | 31篇 |
肿瘤学 | 984篇 |
出版年
2023年 | 58篇 |
2022年 | 78篇 |
2021年 | 223篇 |
2020年 | 151篇 |
2019年 | 193篇 |
2018年 | 256篇 |
2017年 | 136篇 |
2016年 | 193篇 |
2015年 | 265篇 |
2014年 | 353篇 |
2013年 | 371篇 |
2012年 | 564篇 |
2011年 | 643篇 |
2010年 | 443篇 |
2009年 | 404篇 |
2008年 | 588篇 |
2007年 | 633篇 |
2006年 | 605篇 |
2005年 | 533篇 |
2004年 | 499篇 |
2003年 | 425篇 |
2002年 | 336篇 |
2001年 | 327篇 |
2000年 | 274篇 |
1999年 | 226篇 |
1998年 | 96篇 |
1997年 | 97篇 |
1996年 | 82篇 |
1995年 | 58篇 |
1994年 | 70篇 |
1993年 | 49篇 |
1992年 | 118篇 |
1991年 | 99篇 |
1990年 | 100篇 |
1989年 | 100篇 |
1988年 | 73篇 |
1987年 | 74篇 |
1986年 | 68篇 |
1985年 | 60篇 |
1984年 | 44篇 |
1983年 | 39篇 |
1982年 | 33篇 |
1981年 | 34篇 |
1980年 | 25篇 |
1979年 | 24篇 |
1978年 | 22篇 |
1977年 | 26篇 |
1976年 | 19篇 |
1975年 | 13篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Coxsackievirus B3-associated myocardial pathology and viral load reduced by recombinant soluble human decay-accelerating factor in mice 总被引:10,自引:0,他引:10
Yanagawa B Spiller OB Choy J Luo H Cheung P Zhang HM Goodfellow IG Evans DJ Suarez A Yang D McManus BM 《Laboratory investigation; a journal of technical methods and pathology》2003,83(1):75-85
Coxsackievirus B3 (CVB3) infection can result in myocarditis, which in turn may lead to a protracted immune response and subsequent dilated cardiomyopathy. Human decay-accelerating factor (DAF), a binding receptor for CVB3, was synthesized as a soluble IgG1-Fc fusion protein (DAF-Fc). In vitro, DAF-Fc was able to inhibit complement activity and block infection by CVB3, although blockade of infection varied widely among strains of CVB3. To determine the effects of DAF-Fc in vivo, 40 adolescent A/J mice were infected with a myopathic strain of CVB3 and given DAF-Fc treatment 3 days before infection, during infection, or 3 days after infection; the mice were compared with virus alone and sham-infected animals. Sections of heart, spleen, kidney, pancreas, and liver were stained with hematoxylin and eosin and submitted to in situ hybridization for both positive-strand and negative-strand viral RNA to determine the extent of myocarditis and viral infection, respectively. Salient histopathologic features, including myocardial lesion area, cell death, calcification and inflammatory cell infiltration, pancreatitis, and hepatitis were scored without knowledge of the experimental groups. DAF-Fc treatment of mice either preceding or concurrent with CVB3 infection resulted in a significant decrease in myocardial lesion area and cell death and a reduction in the presence of viral RNA. All DAF-Fc treatment groups had reduced infectious CVB3 recoverable from the heart after infection. DAF-Fc may be a novel therapeutic agent for active myocarditis and acute dilated cardiomyopathy if given early in the infectious period, although more studies are needed to determine its mechanism and efficacy. 相似文献
72.
Nasopharyngeal carcinoma (NPC) is predominantly of the undifferentiated histological subtype. Histological differentiation is of limited prognostic significance in NPC. Recent studies have suggested that downregulation of the cadherin-catenin cell adhesion complex may play a crucial role in the initial stage of cancer invasion and metastasis and is associated with poor prognosis in human cancers. Expression of E-cadherin has not been reported previously in NPC, and its prognostic value in NPC is unknown. The purpose of this study was to examine the expression pattern of E-cadherin and its associated partner, beta-catenin, in NPC and their possible applications as prognostic markers to predict the clinical outcome of NPC. Expression of the E-cadherin and beta-catenin was examined by immunohistochemical methods in 74 cases of primary NPC and 17 of their corresponding lymph node metastases. Normal nasopharyngeal epithelium showed strong and homogeneous immunocytochemical staining of E-cadherin and beta-catenin at the cell membranes and intercellular junctions. In contrast, primary NPC showed variable and heterogeneous staining patterns of E-cadherin and beta-catenin. Loss of membranous E-cadherin expression was significantly associated with advanced stages of diseases (P<.001). Eighty percent to ninety percent of NPC in stages IV and V (Ho's staging), respectively, showed a reduced (<35%) membranous staining of E-cadherin compared with normal nasopharyngeal epithelium. Expression of beta-catenin also was downregulated in advanced NPC. Ninety percent to one hundred percent of NPC in stages IV and V (Ho's staging) expressed a reduction (<35%) of imnmunocytochemical staining of beta-catenin. The expression pattern of beta-catenin staining was strongly associated with the expression of E-cadherin (P<.001). Unlike E-cadherin, nuclear staining of beta-catenin expression was observed in some of the primary NPC and lymph node metastasis. Reduced expression of E-cadherin and beta-catenin expression was associated with a shorter survival of NPC patients (P<.001). In advanced NPC patients (stages IV and V), a significant difference in survival was observed in tumors with higher or lower levels of E-cadherin expression (P=.0224, log-rank test). These observations suggests that expression of E-cadherin and beta-catenin may have prognostic values in NPC patients. 相似文献
73.
Ng PS Chan AS Sin WK Tang LC Cheung KB Yuen PM 《Human reproduction (Oxford, England)》2001,16(1):31-35
Postpartum haemorrhage accounts for nearly 28% of maternal mortality in developing countries. Syntometrine is an effective and commonly used oxytocic in preventing postpartum haemorrhage, but it requires a controlled storage environment and i.m. administration. Misoprostol is an orally active uterotonic agent. A total of 2058 patients having a singleton pregnancy, low risk for postpartum haemorrhage and vaginal delivery were randomized to receive either 1 ml syntometrine or 600 microgram misoprostol for the management of the third stage of labour. There were no significant differences between the two groups in the mean blood loss, the incidence of postpartum haemorrhage and the fall in haemoglobin concentration. The need for additional oxytocic injection was significantly higher in the misoprostol group [relative risk (RR) 1.62, 95% confidence interval (CI) 1.34-1.96], but that of manual removal of placenta was reduced (RR 0.29, 95% CI 0.09-0.87). Shivering and transient pyrexia were more common in the misoprostol group. Oral misoprostol might be used in the management of the third stage, especially in situations where the use of syntometrine is contraindicated and facilities for storage and parenteral administration of oxytocics are limited. 相似文献
74.
Regina Raz Kam Cheung Leona Ling David E. Levy 《Somatic Cell and Molecular Genetics》1995,21(2):139-145
The species specificity of interferons (IFNs) depends on restricted recognition of these ligands by multisubunit cell surface receptors. Expression of the human receptor subunit IFNAR in mouse cells conferred sensitivity only to one subtype of human IFN, IFN-B. Other genes on human chromosome 21 were required for responses to other subtypes of type I IFN. In contrast, IFNAR expression in hamster cells did not confer sensitivity to any human IFN tested, including IFN-B. Using human-hamster somatic cell hybrids, we mapped theIfnabr gene, encoding a ligand-binding subunit of the IFN-/ (type I) receptor, to human chromosome 21.Ifnabr colocalized withIfnar to the distal region of q22.1. The presence of a chromosomal fragment encoding IFNABR and IFNAR was also not sufficient to confer sensitivity to human IFN. In contrast, hybrids carrying in addition the region 21q22.2 showed a full response to human IFN-B, suggesting that a gene located in this region encodes a third factor required for type I IFN receptor activity. 相似文献
75.
Wong WW Doyle TC Cheung P Olson TM Reisler E 《Journal of muscle research and cell motility》2001,22(8):665-674
The molecular mechanisms by which different mutations in actin lead to distinct cardiomyopathies are unknown. Here, actin
mutants corresponding to α-cardiac actin mutations causing hypertrophic cardiomyopathy [(HCM) P164A and A331P] and dilated
cardiomyopathy [(DCM) R312H and E361G] were expressed in yeast and purified for in vitro functional studies. While P164A appeared unaltered compared to wild-type (WT) actin, A331P function was impaired. A331P showed
reduced stability in circular dichroism melting experiments; its monomer unfolding transition was 10°C lower compared to WT
actin. Additionally, in vitro filament formation was hampered, and yeast cell cultures were temperature sensitive, implying perturbations in actin–actin
interactions. Filament instability of the A331P mutant actin could lead to actomyosin dysfunction observed in HCM. Yeast strains
harboring the R312H mutation did not grow well in culture, suggesting that cell viability is compromised. The E361G substitution
is located at an α-actinin binding region where the actin filament is anchored. The mutant actin, though unaltered in the
in vitro motility and standard actomyosin functions, had a threefold reduction in α-actinin binding. This could result in impairment
of force-transduction in muscle fibers, and a DCM phenotype.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
76.
Evaluation of quantitative PCR and branched-chain DNA assay for detection of hepatitis B virus DNA in sera from hepatocellular carcinoma and liver transplant patients 总被引:4,自引:0,他引:4 下载免费PDF全文
This study evaluated the applicability of quantitative PCR (Q-PCR) and branched-chain DNA assays for detection of hepatitis B virus (HBV) DNA in sera. For 42 samples, the detection rates were 81 and 41%, respectively, with a correlation coefficient of 0.633. The Q-PCR is useful for early monitoring of HBV load in high-risk patients. 相似文献
77.
Tang NL Hui J Law LK Lam YY Chan KY Yeung WL Chan AY Cheung KL Fok TF 《Human mutation》2000,16(5):446
Glutaric acidemia type I is caused by mutations of the glutaryl-CoA dehydrogenase (GCDH) gene resulting in loss of GCDH enzyme activity. Patients present with progressive dystonia and lesions in basal ganglia. Dietary treatment, when instituted from the early neonatal period, markedly reduces dystonia and morbidity. Early diagnosis and prenatal diagnosis will be facilitated by knowledge of locally prevalent GCDH mutations. Several common GCDH mutations have been found in different ethnic groups. GCDH mutations were studied in 5 Chinese glutaric acidemia type I families. We detected two novel recurrent mutations (A219T and IVS10-2A>C) which were found in two unrelated families. An asymptomatic carrier of IVS10-2A>C was also found on screening of 120 individuals. Other mutations were identified, including two other novel (R386G & IVS3+1G>A) and two known mutations (G178R & R355H). Fibroblasts from patients carrying the novel mutations were confirmed to be deficient for GCDH activity. This is the first report of GCDH mutations describing recurrent mutations in Chinese patients. The carrier rate of IVS10-2A>C may be particularly high in Chinese. 相似文献
78.
79.
Detection and deletion of motion artifacts in electrogastrogram using feature analysis and neural networks 总被引:6,自引:0,他引:6
Electrogastrogram is a surface measurement of gastric myoelectrical activity, and electrogastrography has been an attractive
method for physiological and pathophysiological studies of the stomach due to its nonivasive nature. Motion artifacts, however,
ruin the electrogastrogram (EGG), and make the analysis very difficult and sometimes even impossible. They must be eliminated
from EGG signals before analysis. Up to now, this can only be done by visual inspection, which is not only time-consuming
but also subjective. In this study, a method using feature analysis and neural networks has been developed to realize automatic
detection and elimination of the motion artifacts in EGG recordings by computer. Experiments were conducted to investigate
the characteristics of different motion artifacts. Useful features were extracted, and different combinations of the features
used as the input of the neural network were compared to obtain the optimal performance for the detection of motion artifacts
using the artificial neural network. 相似文献
80.
Distribution of type I, II, III and V in the pepsin solubilized collagens in bovine menisci 总被引:3,自引:0,他引:3
H S Cheung 《Connective tissue research》1987,16(4):343-356
The inner one-third (IM) of both lateral and medial menisci resembles hyaline cartilage, both in gross appearance and histological examination, while the outer two-thirds (OM) is fibrocartilaginous in appearance. Collagen was extracted with pepsin, purified with anion and cation exchange column chromatographies and examined by differential salt precipitation, cyanogen bromide-peptide analysis and SDS gel electrophoresis. IM constitutes approximately 10% of the wet weight of whole meniscus, is made up of 70% collagen of which 34% is pepsin soluble. IM is composed of 60% type II and 40% type I collagen. OM is made up of 80% collagen of which 17% is pepsin soluble. The predominant collagen of OM is type I with a trace amount of types III and V (less than 1%). 相似文献