全文获取类型
收费全文 | 667篇 |
免费 | 48篇 |
国内免费 | 22篇 |
专业分类
耳鼻咽喉 | 1篇 |
儿科学 | 62篇 |
妇产科学 | 14篇 |
基础医学 | 86篇 |
口腔科学 | 8篇 |
临床医学 | 108篇 |
内科学 | 103篇 |
皮肤病学 | 4篇 |
神经病学 | 14篇 |
特种医学 | 175篇 |
外科学 | 38篇 |
综合类 | 17篇 |
预防医学 | 54篇 |
眼科学 | 5篇 |
药学 | 30篇 |
肿瘤学 | 18篇 |
出版年
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 9篇 |
2014年 | 14篇 |
2013年 | 21篇 |
2012年 | 7篇 |
2011年 | 9篇 |
2010年 | 16篇 |
2009年 | 8篇 |
2008年 | 9篇 |
2007年 | 19篇 |
2006年 | 11篇 |
2005年 | 19篇 |
2004年 | 13篇 |
2003年 | 9篇 |
2002年 | 11篇 |
2001年 | 13篇 |
2000年 | 16篇 |
1999年 | 18篇 |
1998年 | 33篇 |
1997年 | 30篇 |
1996年 | 40篇 |
1995年 | 24篇 |
1994年 | 21篇 |
1993年 | 29篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 21篇 |
1989年 | 29篇 |
1988年 | 30篇 |
1987年 | 29篇 |
1986年 | 15篇 |
1985年 | 23篇 |
1984年 | 11篇 |
1983年 | 14篇 |
1982年 | 21篇 |
1981年 | 13篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1977年 | 11篇 |
1976年 | 20篇 |
1975年 | 10篇 |
1974年 | 11篇 |
1973年 | 6篇 |
1970年 | 3篇 |
1966年 | 2篇 |
排序方式: 共有737条查询结果,搜索用时 15 毫秒
71.
Baka is a platelet alloantigen whose putative allele, Bakb, has not been identified previously. By using a serum, "Har," obtained from a patient with posttransfusion purpura, we describe the platelet alloantigen Bakb. The Har serum reacted with an NP-40-extractable platelet membrane protein of 142 kd with mobility similar to platelet glycoprotein IIb alpha. We found that the antigen recognized by the Har serum is inherited in an autosomal dominant mode with an apparent gene frequency of .39. Chi-square analysis of observed and expected phenotype frequencies indicated that serum Har recognizes Bakb, the anticipated allele of Baka. Our findings provide new evidence for polymorphism of glycoprotein IIb and for the association of posttransfusion purpura with alloimmunization to determinants on this glycoprotein. 相似文献
72.
Lethal midline granuloma (LMG) is associated with Epstein-Barr virus (EBV). The latter has at least two subtypes with different biological properties. The subtypes can be identified by their genomic configuration. Using EBV-RNA (EBER) in situ hybridization and EBV polymerase chain reaction (PCR), we have looked for the presence of EBV in six LMGs and six non-Hodgkin's lymphomas (NHLs) located in the nasopharyngeal region, and determined the subtype of EBV. Six of six LMGs were positive by PCR and EBER in situ hybridization, whereas NHLs were either negative or, in three of six cases, showed few EBER- positive cells considered to be nonneoplastic lymphocytes. The subtype 2 was found in LMG lesions of three of six patients; the remaining three of six patients with LMG had the generally occurring subtype 1. The results indicate that the association of EBV with NHL may depend more on tumor type than on its localization. The occurrence of the rare subtype 2 in LMG may relate to a covert immune defect. 相似文献
73.
Kersten MJ; Evers LM; Dellemijn PL; van den Berg H; Portegies P; Hintzen RQ; van Lier RA; von dem Borne AE; van Oers RH 《Blood》1996,87(5):1985-1989
Diagnosis of meningeal localization of lymphoid malignancies by means of cytologic examination of the cerebrospinal fluid (CSF) can be difficult. Thus far no reliable CSF tumor markers have been identified. CD27 is a transmembrane disulfide-linked 55-kD homodimer present on most peripheral blood T cells and on a subset of B cells. CD27 is also expressed on human malignant B cells and high levels of soluble CD27 can be present in the serum of patients with B-cell malignancies. The aim of this study is to determine prospectively the diagnostic value of CSF sCD27 as a tumor marker in patients with meningeal localization of lymphoid malignancies. CSF sCD27 levels were determined by sandwich enzyme-linked immunosorbent assay. The optimal cut-off value using receiver operator characteristics curves was found to be 10 U/mL. sCD27 levels were normal in all 50 control patients (lumbar disc protrusion) and in 39 of 40 samples obtained from patients with either solid tumors or acute myeloid leukemia. Of 104 CSF samples from 70 children with acute lymphoblastic leukemia (ALL) or non-Hodgkin's lymphoma (NHL) undergoing routine central nervous system (CNS) staging, sCD27 was false positive and false negative in only one sample each. In 70 samples from 45 patients suspected of meningeal localization of ALL or NHL, the sCD27 test had an excellent sensitivity (100%) and specificity (82%). In 7 patients with positive CSF studied longitudinally, sCD27 levels correlated very well with remission and relapse. sCD27 levels were not nonspecifically increased by the administration of cytostatic drugs. Finally, sCD27 was also elevated in the 4 patients studied with primary central nervous system lymphoma (PCNSL). CSF sCD27 is a promising tumor marker in patients with either meningeal localization of lymphoid malignancies or PCNSL, and can be useful in the differential diagnosis of CNS involvement by either lymphoid malignancies or solid tumors. 相似文献
74.
Rasmieh Al-Amer Lucie Ramjan Paul Glew Sue Randall Yenna Salamonson 《Issues in mental health nursing》2013,34(10):744-755
Diabetes mellitus is reaching epidemic levels worldwide. In a developing country like Jordan, type 2 diabetes mellitus (T2DM) has reached a prevalence rate of 17.1%. This cross-sectional study examined the relationship between self-care activities and: illness perception, depression, social support, religiosity and spiritual coping, and self-efficacy among patients with T2DM. A random sample of 220 patients with T2DM, who attended Jordan University Hospital in Jordan were enrolled. The data were collected through a structured interview and the medical files. The instruments consisted of a sociodemographic and clinical standardised questionnaires: Brief Illness Perception Questionnaire, Patients’ Health Questionnaire-9; ENRICH Social Support Instrument; Religious and Spiritual Coping Subscale; Diabetes Management Self-Efficacy Scale; and Summary of Diabetes Self-Care Activities. Bivariate analysis investigated the relationship between variables. Structure Equation Modelling (SEM) was performed to test the proposed conceptual model. The study found that approximately 70% of the respondents suffered some form of depressive symptoms. The SEM showed a direct relationship between self-efficacy and self-care activities (β = 0.40; p < 0.001). Depression was indirectly related to self-care activities through self-efficacy (β = –0.20; p = 0.003); nevertheless, it was directly related to perception of: treatment control, consequences, and emotional representations. Overall, the sequence between illness perception and self-efficacy was mediated by depression. Strategies to promote self-efficacy and illness perception are vital in customising a diabetes health plan to meet Arabic cultural expectations. 相似文献
75.
76.
Erythropoietin structure-function relationships: high degree of sequence homology among mammals 总被引:7,自引:3,他引:4
Wen D; Boissel JP; Tracy TE; Gruninger RH; Mulcahy LS; Czelusniak J; Goodman M; Bunn HF 《Blood》1993,82(5):1507-1516
To investigate structure-function relationships of erythropoietin (Epo), we have obtained cDNA sequences that encode the mature Epo protein of a variety of mammals. A first set of primers, corresponding to conserved nucleotide sequences between mouse and human DNAs, allowed us to amplify by polymerase chain reaction (PCR) intron 1/exon 2 fragments from genomic DNA of the hamster, cat, lion, dog, horse, sheep, dolphin, and pig. Sequencing of these fragments permitted the design of a second generation of species-specific primers. RNA was prepared from anemic kidneys and reverse-transcribed. Using our battery of species-specific 5' primers, we were able to successfully PCR- amplify Epo cDNA from Rhesus monkey, rat, sheep, dog, cat, and pig. Deduced amino acid sequences of mature Epo proteins from these animals, in combination with known sequences for human, Cynomolgus monkey, and mouse, showed a high degree of homology, which explains the biologic and immunological cross-reactivity that has been observed in a number of species. Human Epo is 91% identical to monkey Epo, 85% to cat and dog Epo, and 80% to 82% to pig, sheep, mouse, and rat Epos. There was full conservation of (1) the disulfide bridge linking the NH2 and COOH termini; (2) N-glycosylation sites; and (3) predicted amphipathic alpha- helices. In contrast, the short disulfide bridge (C29/C33 in humans) is not invariant. Cys33 was replaced by a Pro in rodents. Most of the amino acid replacements were conservative. The C-terminal part of the loop between the C and D helices showed the most variation, with several amino acid substitutions, deletions, and/or insertions. Calculations of maximum parsimony for intron 1/exon 2 sequences as well as coding sequences enabled the construction of cladograms that are in good agreement with known phylogenetic relationships. 相似文献
77.
Bone marrow disorders: characterization with quantitative MR imaging 总被引:10,自引:0,他引:10
Thirty patients with various hematologic disorders and 15 healthy control subjects underwent quantitative magnetic resonance (MR) imaging of the lumbar spine with spin-echo techniques. Images of patients with infiltrative bone marrow disorders showed significantly more prolonged T1 times than those of control subjects (P less than .001). It was not possible to distinguish different diffuse infiltrative bone marrow disorders on the basis of T1 values. Aplastic anemia could be distinguished from normality because of significantly shortened T1 (P less than .001). A significant correlation was seen between T1 and bone marrow cellularity (r = .74, P less than .001). T2 was of no value in the characterization of bone marrow disorders. Quantitative MR imaging dose not improve the diagnostic potential of bone marrow imaging in the detection of diffuse marrow infiltrates. 相似文献
78.
79.
80.
About 1-2% of the human genome is allocated to production of receptors for the olfactory epithelium-a hint as to the possible importance of this chemical sense, which includes two anatomically distinct systems: the main olfactory system with sensory cells located in the upper part of the nasal cavity, and the vomero-nasal organ with sensory cells on the nasal septum. In adults, individual odours may influence mate preferences and a growing body of evidence indicates that naturally occurring odours play an important role in the mediation of the infant's behaviour. Even foetal olfactory learning seems to occur and breast odours from the mother exert a pheromone-like effect at the newborn's first attempt to locate the nipple. Newborns are generally responsive to breast odours produced by lactating women. Olfactory recognition may be implicated in the early stages of the mother-infant attachment process, when the newborns learn to recognize the own mother's unique odour signature-a process possibly facilitated by the high norepinephrine release and the arousal of the locus coeruleus at birth. New knowledge about human odour physiology may have diagnostic and therapeutic implications-the initiation and stabilization of breastfeeding and termination of apnoeic spells are mentioned as examples. 相似文献