全文获取类型
收费全文 | 11530篇 |
免费 | 1336篇 |
国内免费 | 29篇 |
专业分类
耳鼻咽喉 | 120篇 |
儿科学 | 290篇 |
妇产科学 | 313篇 |
基础医学 | 1810篇 |
口腔科学 | 221篇 |
临床医学 | 1241篇 |
内科学 | 2154篇 |
皮肤病学 | 192篇 |
神经病学 | 1221篇 |
特种医学 | 501篇 |
外国民族医学 | 10篇 |
外科学 | 1527篇 |
综合类 | 268篇 |
一般理论 | 7篇 |
预防医学 | 1011篇 |
眼科学 | 257篇 |
药学 | 796篇 |
中国医学 | 16篇 |
肿瘤学 | 940篇 |
出版年
2023年 | 76篇 |
2022年 | 136篇 |
2021年 | 231篇 |
2020年 | 165篇 |
2019年 | 248篇 |
2018年 | 291篇 |
2017年 | 243篇 |
2016年 | 241篇 |
2015年 | 287篇 |
2014年 | 368篇 |
2013年 | 434篇 |
2012年 | 653篇 |
2011年 | 717篇 |
2010年 | 351篇 |
2009年 | 352篇 |
2008年 | 542篇 |
2007年 | 542篇 |
2006年 | 532篇 |
2005年 | 477篇 |
2004年 | 438篇 |
2003年 | 429篇 |
2002年 | 410篇 |
2001年 | 308篇 |
2000年 | 303篇 |
1999年 | 267篇 |
1998年 | 132篇 |
1997年 | 100篇 |
1996年 | 106篇 |
1995年 | 98篇 |
1994年 | 87篇 |
1992年 | 221篇 |
1991年 | 188篇 |
1990年 | 165篇 |
1989年 | 163篇 |
1988年 | 161篇 |
1987年 | 163篇 |
1986年 | 174篇 |
1985年 | 175篇 |
1984年 | 103篇 |
1983年 | 111篇 |
1982年 | 75篇 |
1979年 | 122篇 |
1978年 | 100篇 |
1977年 | 73篇 |
1976年 | 95篇 |
1974年 | 99篇 |
1973年 | 117篇 |
1972年 | 86篇 |
1971年 | 69篇 |
1970年 | 73篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The localization of sodium and calcium to Schwann cell paranodal loops at nodes of Ranvier and of calcium to compact myelin 总被引:3,自引:0,他引:3
Summary High-voltage electron microscopy (HVEM) has been used to determine the distribution of cationic precipitates in myelinated axons resulting from the application of two cytochemical techniques: a direct osmium pyroantimonate treatment for precipitating Na+, Ca2+ and Mg2+; and a 5 mM Ca2+ inclusion procedure (Oschman & Wall) for imparting electron density to Ca2+ binding sites. Electron probe wavelength spectroscopy was then used on semi-thick tissue sections to identify the species of ions present in the following regions: Schwann cell paranodal loops, axoplasm at the node, compact myelin and extracellular matrix. With these combined procedures we were able to localize elevated concentrations of both Na+ and Ca2+ to cytoplasmic compartments of the Schwann cell paranodal loops, as well as to detect the presence of Ca2+ at elevated levels in compact myelin. The involvement of the Schwann cell paranodal loops in providing a source and/or sink for Na+ involved in impulse conduction is suggested by these results, and the significance of such a role is discussed. A role for Ca2+ in the formation and stabilization of myelin lamellae is also suggested. 相似文献
82.
Spontaneous alpha peak frequency predicts working memory performance across the age span. 总被引:1,自引:0,他引:1
C Richard Clark Melinda D Veltmeyer Rebecca J Hamilton Elena Simms Robert Paul Daniel Hermens Evian Gordon 《International journal of psychophysiology》2004,53(1):1-9
Working memory capacity has been consistently shown to decline with increasing age. Mechanisms underlying this decline are poorly understood. One index that has been found to predict performance on memory tests is alpha peak frequency, the peak of spectral alpha power of the EEG. Activity in the alpha band has been also associated with higher cognitive functions including attention and anticipation and has been shown to slow with age. Few studies, however, have examined whether there might be a relationship between WM decline and alpha peak frequency. The present study specifically investigated this relationship. Digit span was used as the index of WM function. The study made use of 550 normal subjects aged between 11 and 70 years in the Brain Resource International Database. The data were acquired from six laboratories located in the USA (2), Europe (2) and Australia (2). Forward and reverse digit span were found to be lower in older relative to younger age groups. Spontaneous alpha peak frequency slowed with age and more so at anterior than posterior sites. Frontal alpha peak frequency was found to be a significant predictor of reverse digit span, with each 1 Hz increase in frequency associated with a 0.21 increase in reverse digit span score and this was independent of age, indicating a positive relationship between alpha peak frequency and working memory performance. 相似文献
83.
Raymond E Biagini Barbara A MacKenzie Deborah L Sammons Jerome P Smith Edward F Krieg Shirley A Robertson Robert G Hamilton 《Annals of allergy, asthma & immunology》2006,97(2):196-202
BACKGROUND: In the absence of a US Food and Drug Administration (FDA)-cleared latex skin testing reagent, in vitro tests remain important for the diagnosis of latex allergy. OBJECTIVE: To evaluate the performance characteristics of IMMULITE 2000 3gAllergy (Immulite), a third-generation, FDA-cleared, continuous random-access immunoanalyzer, for the quantification of latex specific IgE. METHODS: Stored serum samples (N = 201) from patients classified as having positive or negative latex puncture skin test results were measured for latex specific IgE levels using Immulite, and these data were compared with historical results from 3 second-generation, FDA-cleared IgE antilatex assays (AlaSTAT [Ala], AutoCAP [CAP], and HY*TEC enzyme immunoassay [HT]). RESULTS: The diagnostic performances of the CAP, Ala, and Immulite assays (> or = 0.35 kU/L cutoff value) were equivalent in sensitivity and specificity (P > .05). The HT assay (> or = 0.05 kU/L cutoff value) was more sensitive and less specific (P < .05). Immulite (> or = 0.10 kU/L cutoff value) had greater sensitivity than Ala and CAP and greater specificity than HT (P < .05 for both). Diagnostic efficiency was greater for Immulite than for CAP, Ala, and HT (P < .05). CONCLUSIONS: The Immulite system is superior in diagnostic performance, especially at the 0.10 kU/L or greater cutoff level, for the diagnosis of latex allergy compared with older, second-generation assays. Immulite still misclassifies 15.5% of puncture skin test-positive individuals as negative for latex specific IgE. Compared with second-generation assays, Immulite represents a technological advance, with enhanced speed and less operator intervention. 相似文献
84.
85.
Sporadic fundic gland polyps: common gastric polyps arising through activating mutations in the beta-catenin gene 总被引:1,自引:0,他引:1 下载免费PDF全文
Abraham SC Nobukawa B Giardiello FM Hamilton SR Wu TT 《The American journal of pathology》2001,158(3):1005-1010
Fundic gland polyps (FGPs) are the most common gastric polyps. FGPs traditionally have been regarded as nondysplastic hamartomatous or hyperplastic lesions, but their pathogenesis remains unclear. We have recently shown that somatic adenomatous polyposis coli (APC) gene alterations are frequently present in FGPs associated with familial adenomatous polyposis (FAP), raising the possibility that mutations of the beta-catenin gene affecting the APC/beta-catenin pathway might be involved in the pathogenesis of sporadic FGPs. We analyzed somatic beta-catenin gene mutations in 57 sporadic FGPs from 40 patients without FAP and in 19 FGPs from 13 FAP patients. Direct DNA sequencing of exon 3 encompassing the glycogen synthase kinase-3beta phosphorylation region for beta-catenin was used with confirmation by HIN:fI restriction endonuclease digestion. The foveolar epithelium and dilated fundic glands of the polyps were separately microdissected and analyzed in 22 of 57 sporadic FGPs. Activating beta-catenin gene mutations were present in 91% (52 of 57) of sporadic FGPs. Both the foveolar epithelium and the dilated fundic gland epithelium comprising the polyps were shown to have the same somatic beta-catenin mutation in 21 of 22 (95%) sporadic FGPs. In contrast, beta-catenin gene mutations were not present in any of the 19 FAP-associated FGPs (P: < 0.000001). The high frequency of beta-catenin mutations in sporadic FGPs indicates that these lesions arise through activating mutations of the beta-catenin gene. Beta-catenin mutations in gastrointestinal tract polyps have previously only been demonstrated in a subset of adenomatous (dysplastic) or neoplastic polyps. Sporadic FGPs are therefore the only lesions of the gastrointestinal tract to demonstrate beta-catenin mutations while lacking dysplastic morphology. 相似文献
86.
87.
Stein RI Legault L Daneman D Weksberg R Hamilton J 《American journal of medical genetics. Part A》2004,(2):166-170
We report on three patients with Costello syndrome and isolated growth hormone (GH) deficiency treated with biosynthetic GH. To our knowledge, these are the only patients with Costello syndrome who have been successfully treated for GH deficiency. We review the pathophysiology of Costello syndrome and highlight the recent recommendations of tumor screening and cardiac surveillance in this population, of particular relevance to those receiving GH therapy. 相似文献
88.
Uthoff SM Crawford NP Eichenberger MR Hamilton CJ Petras RE Martin ER Galandiuk S 《American journal of medical genetics》2002,113(3):242-249
Genomewide scanning has been used to identify chromosomal regions encoding susceptibility loci to inflammatory bowel disease (IBD). The greatest evidence for linkage to IBD has been reported for a region of chromosome 12q14 surrounding the microsatellite marker D12S83, with a logarithm of odds score of 5.47 and a positive transmission disequilibrium test, and which was subsequently named IBD2. We wished to confirm this locus by genotyping the highly polymorphic microsatellites D12S1022, D12S1056, and D12S83, spanning a continuous region on chromosome 12 of 342 kb, in a cohort of nonrelated individuals with ulcerative colitis (89 patients), Crohn disease (121 patients), and population-based control subjects (100 patients). In non-Jewish Caucasians, one D12S1022 allele, one D12S1056 genotype, and three D12S83 alleles were found to have statistically significant differences in distribution between the two disease groups and the control population. These data support a significant association of IBD with the IBD2 locus in close vicinity to the three markers studied. The replication of genetic risk loci in a case control association study may indicate susceptibility genes in this region and may facilitate identification of candidate genes for IBD. Subgroup analysis revealed a notable difference in genotype distribution among Jewish Caucasian and African American patients affected with Crohn disease when compared with similarly affected non-Jewish Caucasians. Using Fisher exact test, statistically significant distribution differences were observed for D12S1022 and D12S83. These data indicate that there may be significant genetic heterogeneity between different ethnic and racial IBD populations or may simply reflect differences in marker allele frequencies among populations. 相似文献
89.
90.
Hamilton R. Correia Sandra C. Balseiro Elisabete R. Correia Paulo G. Mota Manuel L. De Areia 《American journal of human biology》2004,16(1):24-30
The plumpness of the human newborn has long been recognized as a trait in need of explanation among researchers. Using a linear regression analysis, we find that head circumference is significantly and positively associated with BMI at birth, after gestational age and birthlength were controlled for, in a sample of 1,069 healthy liveborn routinely delivered at the University Hospital of Coimbra (partial correlation r = 0.409, P < 0.0001). This significant association is consistent with the idea that newborn fatness is related to the higher need of lipids in newborn humans as an energetic and plastic substrate during its accelerated brain growth period. As birthweight and birth head size are associated with head size and cognitive abilities in childhood and adult life, it could be postulated that these cognitive abilities could have acted as selective pressure responsible for the newborn fatness increase in our lineage. Am. J. Hum. Biol. 16:24–30, 2004. © 2003 Wiley‐Liss, Inc. 相似文献