全文获取类型
收费全文 | 1333篇 |
免费 | 188篇 |
国内免费 | 10篇 |
专业分类
耳鼻咽喉 | 15篇 |
儿科学 | 100篇 |
妇产科学 | 14篇 |
基础医学 | 147篇 |
口腔科学 | 41篇 |
临床医学 | 207篇 |
内科学 | 307篇 |
皮肤病学 | 9篇 |
神经病学 | 153篇 |
特种医学 | 163篇 |
外科学 | 136篇 |
综合类 | 38篇 |
预防医学 | 43篇 |
眼科学 | 1篇 |
药学 | 101篇 |
中国医学 | 5篇 |
肿瘤学 | 51篇 |
出版年
2023年 | 2篇 |
2022年 | 4篇 |
2021年 | 11篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 40篇 |
2017年 | 44篇 |
2016年 | 40篇 |
2015年 | 39篇 |
2014年 | 41篇 |
2013年 | 69篇 |
2012年 | 48篇 |
2011年 | 36篇 |
2010年 | 69篇 |
2009年 | 56篇 |
2008年 | 41篇 |
2007年 | 41篇 |
2006年 | 38篇 |
2005年 | 31篇 |
2004年 | 24篇 |
2003年 | 28篇 |
2002年 | 20篇 |
2001年 | 30篇 |
2000年 | 18篇 |
1999年 | 16篇 |
1998年 | 61篇 |
1997年 | 60篇 |
1996年 | 62篇 |
1995年 | 52篇 |
1994年 | 31篇 |
1993年 | 45篇 |
1992年 | 30篇 |
1991年 | 31篇 |
1990年 | 39篇 |
1989年 | 38篇 |
1988年 | 42篇 |
1987年 | 38篇 |
1986年 | 26篇 |
1985年 | 34篇 |
1984年 | 19篇 |
1983年 | 27篇 |
1982年 | 14篇 |
1981年 | 21篇 |
1980年 | 12篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1976年 | 11篇 |
1975年 | 6篇 |
1974年 | 3篇 |
排序方式: 共有1531条查询结果,搜索用时 0 毫秒
21.
The role of size, sequence and haplotype in the stability of FRAXA and FRAXE alleles during transmission 总被引:2,自引:5,他引:2
Murray A; Macpherson JN; Pound MC; Sharrock A; Youings SA; Dennis NR; McKechnie N; Linehan P; Morton NE; Jacobs PA 《Human molecular genetics》1997,6(2):173-184
Factors involved in the stability of trinucleotide repeats during
transmission were studied in 139 families in which a full mutation,
premutation or intermediate allele at either FRAXA or FRAXE was
segregating. The transmission of alleles at FRAXA, FRAXE and four
microsatellite loci were recorded for all individuals. Instability within
the minimal and common ranges (0-40 repeats for FRAXA, 0-30 repeats for
FRAXE) was extremely rare; only one example was observed, an increased in
size at FRAXA from 29 to 39 repeats. Four FRAXA and three FRAXE alleles in
the intermediate range (41-60) repeats for FRAXA, 31-60 for FRAXE) were
unstably transmitted. Instability was more frequent for FRAXA intermediate
alleles that had a tract of pure CGG greater than 37 although instability
only occurred in two of 13 such transmissions: the changes observed were
limited to only one or two repeats. Premutation FRAXA alleles over 100
repeats expanded to a full mutation during female transmission in 100% of
cases, in agreement with other published series. There was no clear
correlation between haplotype and probability of expansion of FRAXA
premutations. Instability at FRAXA or FRAXE was more often observed in
conjunction with a second instability at an independent locus suggesting
genomic instability as a possible mechanism by which at least some FRAXA
and FRAXE mutations arise.
相似文献
22.
J Davies B Srinivasan PA Brennan 《Annals of the Royal College of Surgeons of England》2021,103(1):e42
Lipomas are common benign tumours that can occur in most parts of the body. Lipomas arising from the deep temporal fat pad, found between the two layers of the deep temporal fascia, are rare, however; there has been only one documented case report to our knowledge. We describe a second case arising from the temporal fat pad in a patient treated at our unit, having previously reported the first one, and discuss the relevant anatomy and management. 相似文献
23.
Joshua R Lewis Trudy Voortman John PA Ioannidis 《Journal of bone and mineral research》2021,36(2):219-226
A healthy diet is essential to attain genetically determined peak bone mass and maintain optimal skeletal health across the adult lifespan. Despite the importance of nutrition for bone health, many of the nutritional requirements of the skeleton across the lifespan remain underexplored, poorly understood, or controversial. With increasingly aging populations, combined with rapidly changing diets and lifestyles globally, one anticipates large increases in the prevalence of osteoporosis and incidence of osteoporotic fractures. Robust, transparent, and reproducible nutrition research is a cornerstone for developing reliable public health recommendations to prevent osteoporosis and osteoporotic fractures. However, nutrition research is often criticized or ignored by healthcare professionals due to the overemphasis of weak science, conflicting, confusing or implausible findings, industry interests, common misconceptions, and strong opinions. Conversely, spurious research findings are often overemphasized or misconstrued by the media or prominent figures especially via social media, potentially leading to confusion and a lack of trust by the general public. Recently, reforms of the broader discipline of nutrition science have been suggested and promoted, leading to new tools and recommendations to attempt to address these issues. In this perspective, we provide a brief overview of what has been achieved in the field on nutrition and bone health, focusing on osteoporosis and osteoporotic fractures. We discuss what we view as some of the challenges, including inherent difficulties in assessing diet and its change, disentangling complex interactions between dietary components and between diet and other factors, selection of bone-related outcomes for nutrition studies, obtaining evidence with more unbiased designs, and perhaps most importantly, ensuring the trust of the public and healthcare professionals. This perspective also provides specific recommendations and highlights new developments and future opportunities for scientists studying nutrition and bone health. © 2021 American Society for Bone and Mineral Research (ASBMR). 相似文献
24.
Bias in somatic hypermutation of human VH genes 总被引:3,自引:1,他引:2
Translationally silent mutations, which are not antigen selected,of human VH6 Ig gene rearrangements isolated from human spleenwere analyzed for bias to gain insight into intrinsic featuresof the mutation process. Sixty-three clones representing 38VH6DJ rearrangements had an overall mutation frequency of 4.5%,a replacement/silent (R/S) mutation ratio of 2.1 and 167 uniquesilent mutations. The silent mutations showed bias in: (I) targetingto CDR1 and CDR2, (II) an increased frequency of mutations ofA compared to T nucleotide bases on the coding strand, and (III)an increased frequency of transitions versus transvereions.Bias of CG over CA, of GC over GT and of AC over AT transvereionswas also present. Hot spots of mutation were observed, somewhich corresponded to potential sites of stem - loop formation.The results suggest that the somatic mutation process in manmay be targeted to the complementarity determining region forsome V genes, exhibits specific base substitutions favoringtransitions and specific types of transversions, and may beoccurring on only one DNA strand. 相似文献
25.
26.
27.
目的探讨瘦素质量浓度与早期静脉营养及生长发育的关系。方法新疆医科大学第一
附属医院新生儿科于2005 01—2006 02,将收治的86例早产适于胎龄儿用随机数字表法分为观察组(早期微量喂养同时辅助胃肠外营养组)45
例和对照组(单纯早期微量喂养组)47例,分别测定脐血及第7天血清瘦素质量浓度,同时监测营养状况和生长发育指标,并作对比分析。结果
(1)观察组与对照组脐血瘦素质量浓度分别为(4.6±3.7)ng/mL、(4.8±2.2)ng/mL,生后第7天两组瘦素质量浓度分别为(4.3±2.2)ng/mL、(3.1
±1.7)ng/mL。对照组第7天血清瘦素质量浓度明显低于脐血(P<0.05),而观察组其差异无统计学意义(P>0.05)。(2)脐血瘦素质量浓度与出生体
重、胎龄成正相关(r=0.56、r=0.67)。(3)观察组第7天热卡及蛋白质摄入量、血清瘦素质量浓度、皮褶厚度变化值与对照组相比,差异有统计
学意义(P<0.05)。结论对早产儿应尽早喂养,同时需要胃肠外营养作为肠内营养的补充。瘦素可作为新生儿营养效果判定的实验室指标之一。 相似文献
28.
The isolated capsular polysaccharide induces antibody protective against invasive infections by H. influenzae b. Maturation of responsiveness is slow such that infants are not protected. Several protein-coupled versions of the antigen are being tested for immunogenicity in early infancy. The relation of structure to immunogenicity is not completely defined, but all induce a booster-type antibody response with protective potential. Primary vaccination in infancy appears to mimic natural priming, activating clones of B lymphocytes that can later be restimulated by uncoupled polysaccharide. Prospects appear good for immunizing normal infants and also children with immunoregulatory defects predisposing to infection. 相似文献
29.
Rajeev Gupta MD Manuel Villa MD Emanuel Agaba MD Garry Ritter PA MHA Cristina Sison Corrado P. Marini MD Rafael Barrera MD 《JPEN. Journal of parenteral and enteral nutrition》2013,37(3):368-374
Background: The incidence of obesity is rising, and an increasing number of obese patients are admitted to surgical intensive care units (SICUs). However, it is not clear whether obesity is an independent risk factor for increased morbidity and mortality in SICU patients. We examined the effect of obesity on morbidity and mortality in patients admitted to the SICU in this study. Method: We reviewed prospectively acquired SICU data in normal and obese patients with an SICU length of stay >24 hours. Comparability of the groups was assessed using a χ2 test or Fisher exact test, as appropriate, for categorical variables and analysis of variance (ANOVA) or the Kruskal‐Wallis test, as appropriate, for continuous variables. Results: Of the 1792 consecutive patients evaluated, 711 had a normal body mass index (BMI), and 993 were either preobese or obese. There was no statistically significant difference across the 5 BMI groups with respect to any of the 3 comorbidity indices (Acute Physiology and Chronic Health Evaluation III [APACHE III], Simplified Acute Physiology Score, or Multiple Organ Dysfunction Score). There was no statistically significant difference in the intensive care unit (ICU) length of stay and hospital length of stay or time‐to‐ICU mortality (log‐rank test P = .054) among the 5 BMI groups. A Cox regression analysis and backward elimination algorithm selected APACHE III to be the most important explanatory variable for survival time. Conclusion: Obesity does not affect the mortality of patients admitted to the SICU. We conclude that obesity cannot be used as an independent predictive mortality outcome variable in patients admitted to the SICU. 相似文献
30.
D'Andrea RJ; Barry SC; Moretti PA; Jones K; Ellis S; Vadas MA; Goodall GJ 《Blood》1996,87(7):2641-2648
The hypothesis that extracellular truncation of the common receptor subunit for interleukin-3 (IL-3), granulocyte-macrophage colony- stimulating factor, and IL-5 (h beta c) can lead to ligand-independent activation was tested by infecting factor-dependent hematopoietic cell lines with retroviruses encoding truncated forms of h beta c. A truncation, resembling that in v-Mpl, and retaining 45 h beta c-derived extracellular residues, led to constitutive activation in the murine myeloid cell line, FDC-P1. However, infection of cells with retrovirus encoding a more severely truncated receptor, retaining only 7 h beta c- derived extracellular residues, did not confer factor independence on these cells. These experiments show that truncation activates the receptor and define a 37-amino acid segment of h beta c (H395-A431) which contains two motifs conserved throughout the cytokine receptor superfamily (consensus Y/H XX R/Q VR and WSXWS), as essential for factor-independent signaling. The mechanism of activation was also investigated in less severe truncations. A receptor that retains the entire membrane-proximal domain (domain 4) also conferred factor independent growth on FDC-P1 cells; however, a retrovirus encoding a truncated form of h beta c having two intact membrane proximal domains did not have this ability, suggesting that domain 3 may have an inhibitory role in h beta c. The ability of these receptors to confer factor independence was cell specific as demonstrated by their inability to confer factor-independent growth when introduced into the murine IL-3-dependent pro-B cell line BaF-B03. These results are consistent with a model in which activation requires unmasking of an interactive receptor surface in domain 4 and association with a myeloid- specific receptor or accessory component. We suggest that in the absence of ligand intramolecular interactions prevent inappropriate signaling. 相似文献