全文获取类型
收费全文 | 12912篇 |
免费 | 758篇 |
国内免费 | 59篇 |
专业分类
耳鼻咽喉 | 215篇 |
儿科学 | 419篇 |
妇产科学 | 266篇 |
基础医学 | 1850篇 |
口腔科学 | 378篇 |
临床医学 | 1255篇 |
内科学 | 2577篇 |
皮肤病学 | 209篇 |
神经病学 | 1357篇 |
特种医学 | 392篇 |
外科学 | 1288篇 |
综合类 | 81篇 |
一般理论 | 7篇 |
预防医学 | 1322篇 |
眼科学 | 145篇 |
药学 | 1046篇 |
中国医学 | 58篇 |
肿瘤学 | 864篇 |
出版年
2023年 | 91篇 |
2022年 | 223篇 |
2021年 | 460篇 |
2020年 | 288篇 |
2019年 | 398篇 |
2018年 | 433篇 |
2017年 | 308篇 |
2016年 | 306篇 |
2015年 | 360篇 |
2014年 | 544篇 |
2013年 | 673篇 |
2012年 | 1015篇 |
2011年 | 1068篇 |
2010年 | 536篇 |
2009年 | 481篇 |
2008年 | 783篇 |
2007年 | 820篇 |
2006年 | 707篇 |
2005年 | 696篇 |
2004年 | 651篇 |
2003年 | 554篇 |
2002年 | 529篇 |
2001年 | 122篇 |
2000年 | 93篇 |
1999年 | 106篇 |
1998年 | 115篇 |
1997年 | 99篇 |
1996年 | 66篇 |
1995年 | 64篇 |
1994年 | 70篇 |
1993年 | 60篇 |
1992年 | 83篇 |
1991年 | 84篇 |
1990年 | 79篇 |
1989年 | 71篇 |
1988年 | 61篇 |
1987年 | 47篇 |
1986年 | 52篇 |
1985年 | 55篇 |
1984年 | 52篇 |
1983年 | 44篇 |
1982年 | 41篇 |
1981年 | 24篇 |
1980年 | 24篇 |
1979年 | 40篇 |
1978年 | 27篇 |
1975年 | 20篇 |
1974年 | 25篇 |
1971年 | 17篇 |
1970年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Evaluation of the offer vs. serve option within self-serve, choice menu lunch program at the elementary school level 总被引:1,自引:0,他引:1
The feasibility of a centralized menu and the effectiveness of an "offer vs. serve" option within a self-serve, choice menu lunch program at the elementary school level were determined. Student trays (no. = 370/day) were visually evaluated for foods chosen and consumed. The same 1-week menu was served at two urban Southern schools. One represented a high-poverty-area, all-black-student school and the other represented a middle-income-area school with a white to black student ratio of 3:1. Students were able to choose the required USDA minimal number of three foods, and 66% of the foods selected were similar at the two schools, demonstrating that a centralized menu was feasible. Three-fourths of the students were able to choose more than 75% of one-third of the RDA for all nutrients except pyridoxine and ascorbic acid at both schools and iron at the high-poverty school. Twenty-five percent or more of the students did not consume 75% of one-third the Recommended Dietary Allowance for thiamin, vitamin B-6, ascorbic acid, iron, and magnesium at either school or of niacin and vitamin A at the middle-income school. Overall plate waste was 12.9%, with younger children wasting more food than older children and more waste in the middle-income than the high-poverty school. In general, the "offer vs. serve" was an effective option. 相似文献
52.
Fisher JP Lalani Z Bossano CM Brey EM Demian N Johnston CM Dean D Jansen JA Wong ME Mikos AG 《Journal of biomedical materials research. Part A》2004,68(3):428-438
In this work we sought to understand the effect of biomaterial properties upon healing bone tissue. We hypothesized that a hydrophilic polymer gel implanted into a bone tissue defect would impede the healing process owing to the biomaterial's prevention of protein adsorption and thus cell adhesion. To test this hypothesis, healing bone was investigated within a rabbit incisor extraction socket, a subcritical size bone defect that resists significant soft tissue invasion by virtue of its conformity. After removal of the incisor teeth, one tooth socket was left as an empty control, one was filled with crosslinked polymer networks formed from the hydrophobic polymer poly(propylene fumarate) (PPF), and one was filled with a hydrogel formed from the hydrophilic oligomer oligo(poly(ethylene glycol) fumarate) (OPF). At five different times (4 days as well as 1, 2, 4, and 8 weeks), jaw bone specimens containing the tooth sockets were removed. We analyzed bone healing by histomorphometrical analysis of hematoxylin and eosin stained sections as well as immunohistochemically stained sections. The proposed hypothesis, that a hydrophilic material would hinder bone healing, was supported by the histomorphometrical results. In addition, the immunohistochemical results reflect molecular signaling indicative of the early invasion of platelets, the vascularization of wound-healing tissue, the differentiation of migrating progenitor cells, and the formation and remodeling of bone tissue. Finally, the results emphasize the need to consider biomaterial properties and their differing effects upon endogenous growth factors, and thus bone healing, during the development of tissue engineering devices. 相似文献
53.
Lucarelli P Piciullo A Palmarino M Verdecchia M Saccucci P Arpino C Curatolo P 《Neuroscience letters》2004,367(1):88-91
Individuals with Down's syndrome (DS), i.e., trisomy 21, over 40 years of age, are likely to develop neuropathological changes characteristic of Alzheimer's disease (AD). The involvement of chromosome 21 both in DS and AD suggests a shared genetic susceptibility to these disorders, but genetic determinants are still undefined. The -48C/T polymorphism in the PSEN1 promoter is a possible candidate, since it has recently been associated with an increased risk of early onset AD. Based on the assumption that the excess of dementia in DS might be a consequence of a different distribution of the -48C/T polymorphism, we investigated the association between DS and this polymorphism in patients with trisomy 21 and controls. Overall, 260 DS patients and 197 controls were recruited at the Department of Neurosciences, Tor Vergata University of Rome. Cases and controls had similar age and gender distribution. High molecular weight DNA was extracted from whole blood samples collected in EDTANa(2) and -48C/T genotypes were determined. Genotype and allele frequencies were compared between cases and controls. Cases were less likely than controls to have the CC genotype ( P = 0.05). A significant difference for allele distribution between DS cases and controls was found, with DS showing a lower frequency of the allele C compared with the control population (OR: 0.57; 95% CI: 0.35-0.91; P = 0.01). No significant interaction of PSEN1 with age, gender, ApoE and -850 TNF-alpha polymorphisms was found. The association found suggests that the -48C/T polymorphism in the PSN1 gene promoter, which is involved in the modulation of amyloid beta load in human AD, is associated with DS. However, the biological role of this polymorphism in DS-related dementia remains unclear and merits further investigation. 相似文献
54.
Performance characteristics of a rapid new immunochromatographic test for detection of antibodies to human immunodeficiency virus 总被引:1,自引:0,他引:1
Ribeiro-Rodrigues R Ferreira da Silva Pinto Neto L Cunha CB Cabral VP Dietze R 《Clinical and diagnostic laboratory immunology》2003,10(2):303-307
A new immunochromatographic rapid test (Rapid Check HIV 1 and 2; Núcleo de Doen?as Infecciosas) for the detection of antibodies to human immunodeficiency virus type 1 and type 2 in human samples (whole blood, serum, and plasma) was evaluated and compared to the commercially available Determine (Abbott Laboratories). When whole-blood samples were evaluated, the specificity and sensitivity of both tests were 100%. However, when plasma samples were used, sensitivity for the Rapid Check HIV 1&2 and the Determine tests were 100 and 98.58%, respectively. The observed specificity for plasma samples was 98.94% for the Rapid Check HIV 1&2 and 96.97% for the Determine test. The results presented here are encouraging and support the adoption of both tests as an alternative to enzyme-lined immunosorbent assay and/or Western blots in regions where laboratorial infrastructure is not available or for use in the management of occupational accidents for healthcare workers. 相似文献
55.
Fazzi E Signorini SG Uggetti C Bianchi PE Lanners J Lanzi G 《American journal of medical genetics. Part A》2005,(1):13-19
Leber congenital amaurosis (LCA) is the most severe form of inherited retinal dystrophy that presents in infancy. LCA is both clinically and genetically heterogeneous. The aim of our study was to clarify the clinical aspects of LCA and to contribute to improved characterization of the disorder. We studied 40 children affected by LCA (mean age at first observation: 19 months, range: 8-50 months), who underwent a comprehensive evaluation that included: neurophthalmological evaluation, electroretinogram (ERG), and visual evoked potentials (VEPs), general and neurological examinations, developmental assessment using scales for visually impaired children, neuroradiological examinations, hepatic and renal function and metabolic investigations, brainstem auditory evoked potentials (BAEPs), EEG, and hand radiographs. Analyses of known LCA genes are ongoing. The subjects are still being followed up at 6-/12-month intervals. All the subjects fulfilled De Laey's criteria for LCA. The neurological examination was abnormal in 31 cases (hypotonia, ataxia with/without associated cerebellar signs). Cognitive development was normal in 24 cases, borderline in five, and subnormal in 11. Mild and nonspecific alterations on MRI were present in seven cases, and "molar tooth" sign in four; all the others had a normal neuroradiological picture. Among the subjects presenting with neurological signs, a subgroup (13 patients) emerged that was characterized by systemic (skin, kidney, liver) involvement. Our data confirm that LCA is a heterogeneous entity that can present as an isolated ocular manifestation, or in association with neurological and systemic abnormalities and support the need for a multidisciplinary approach to this entity and for genotype-phenotype studies. 相似文献
56.
D'adda T Pizzi S Azzoni C Bottarelli L Crafa P Pasquali C Davoli C Corleto VD Delle Fave G Bordi C 《Human pathology》2002,33(3):322-329
Most foregut digestive endocrine neoplasms may be associated with the multiple endocrine type 1 (MEN-1) syndrome. In contrast, midgut/hindgut carcinoids never show such association. To investigate the pathogenetic involvement of the MEN-1 gene and of putative additional oncosuppressor gene(s) distal to it, a comparative analysis of loss of heterozygosity (LOH) at chromosome 11q13 to 11qter was performed in 27 foregut (pancreatic endocrine tumors [PETs]), 23 midgut (ileal and appendiceal), and 3 hindgut (rectal) endocrine tumors. LOH at the MEN-1 gene locus at 11q13 was observed in 52% of the 23 sporadic and in all 4 MEN-1-associated PETs and was found to consistently and continuously span to the most distal marker investigated at 11qter. In contrast, only occasional, discontinuous, and mostly interstitial LOH for 11q markers was observed in ileal (midgut) carcinoids, whereas no LOH was found in all appendiceal (midgut) and rectal (hindgut) carcinoids. The consistent extension of LOH from the MEN-1 region to 11qter in sporadic PETs suggests a mechanism of gene inactivation via chromosomal breakage and complete loss of chromosome 11q; furthermore, these results expand beyond the 11q13 region the search for additional oncosuppressor gene(s) potentially involved in the genesis of these neoplasms. The low frequency, limited extension, and discontinuous distribution of 11q deletions in midgut/hindgut carcinoids suggest that MEN-1 gene is not involved in the pathogenesis of these tumors. 相似文献
57.
Marco Salvetti Giovanni Ristori Mauro D'Amato Carla Buttinelli Marika Falcone Cesare Fieschi Hartmut Wekerle Carlo Pozzilli 《European journal of immunology》1993,23(6):1232-1239
T lymphocytes from patients with multiple sclerosis (MS) recognize multiple myelin basic protein (MBP) epitopes. This situation complicates the design of specific immunotherapies. We investigated to which extent the T cell response to MBP is heterogeneous in single subjects in terms of preferentially recognized regions of the molecule, major histocompatibility complex (MHC) restriction, and stability over time. From each of nine patients with MS, a minimum of six MBP-specific T lymphocyte lines (TLL) were assayed for the proliferative response to a panel of overlapping peptides, encompassing the whole MBP. Predominant Tcell recognitions of distinct MBP regions were present in three patients, all HLA-DR2+, independently of the clinical features of their disease. Tcell reactivity was preferentially directed to residues 16-38 in one patient. In this case the response was also stable over time, during different phases of the disease. Predominant reactivity to residues 86-99 was detected in the two other DR2+ patients. In each of the patients with other HLA-DR haplotypes (DR2?), as well as in three DR2+ non-MS donors, the Tcell response to MBP appeared to be considerably more heterogeneous. The HLA restriction element varied among TLL recognizing the same MBP region, even when raised from the same individual. The genomic HLA typing, performed on the DRB1 and DRB5 genes in the DR2+ subjects, showed no obvious correspondence between preferential responses to regions of MBP and HLA-DR2 subtypes. In this context, a simple, new method for the genomic typing of the HLA-DRB1 gene in individuals with the HLA-DR2 serological specificity is also described. We conclude that predominant and stable T cell responses to a single MBP region can be detected in some patients with MS. In these individuals, the MHC restriction of the T cell recognition of predominant regions appears to be variable. Polymorphisms of the HLA-DR2 gene products alone do not account for the selection of the dominant MBP Tcell epitope. 相似文献
58.
Macedo-Soares MF Itami DM Lima C Perini A Faquim-Mauro EL Martins MA Macedo MS 《The Journal of allergy and clinical immunology》2004,114(1):97-104
BACKGROUND: Chronic airway inflammation is a fundamental feature of bronchial asthma, which is characterized by the accumulation and activation of inflammatory cells, such as mast cells and eosinophils, that are tightly regulated by TH2 cytokines and chemokines. Recently, we demonstrated, in a murine model of asthma with immunosuppressed mice reconstituted with antigen-specific IgE or IgG1 antibodies, that IgE, but not IgG1, participates in potentiation of airway inflammation and induction of airway hyperreactivity (AHR). The IgG1 antibody, however, did not elicit passive cutaneous anaphylactic reactions, which was in contrast to IgE. OBJECTIVES: Because 2 types of murine IgG1 have been demonstrated with regard to anaphylactic activity, the present experiments were undertaken to determine the role of anaphylactic and nonanaphylactic IgG1 antibodies in the development of antigen-induced eosinophilia and AHR in this model. METHODS: Dinitrophenyl-conjugated, heat-coagulated hen's egg white was implanted in immunosuppressed mice reconstituted with anaphylactic or nonanaphylactic IgG1. Intratracheal challenge with aggregated dinitrophenyl-ovalbumin was performed on day 14, and lung inflammatory and mechanical parameters were evaluated after 48 hours. RESULTS: Our results demonstrated that reconstitution of immunosuppressed mice with anaphylactic IgG1 antibodies in contrast to nonanaphylactic IgG1 antibodies potentiates their ability to have pulmonary eosinophilic inflammation and AHR. IL-5 and eotaxin levels in bronchoalveolar lavage fluid from anaphylactic IgG1-reconstituted mice were also higher than those in nonanaphylactic IgG1-reconstituted mice. CONCLUSIONS: These results indicate that the anaphylactic property of murine IgG1 molecules is essential for their capacity to enhance lung eosinophilic inflammation and to induce AHR. 相似文献
59.
Characterization of human papillomavirus infection,P53 and Ki-67 expression in cervix cancer of Mozambican women 总被引:3,自引:0,他引:3
Carrilho C Gouveia P Cantel M Alberto M Buane L David L 《Pathology, research and practice》2003,199(5):303-311
In this study, we aimed at evaluating the distribution of HPV types and the expression of P53 and Ki-67 in cervix carcinomas of Mozambican women. Fourty-seven invasive carcinomas, 10 CIN III, and 10 normal cervix were studied. P53 and Ki-67 expression was examined immunohistochemically. HPV infection and HPV types were detected by PCR (GP5+/bio-GP6+) and enzyme-immunoassay, respectively. Expression of P53 and Ki-67 and detection of HPV were as follows: normal cervix--0%, 10%, and 0%, respectively; CIN III--10%, 0%, and 100%, respectively; invasive carcinomas--50%, 55.5%, and 70%, respectively. HPV 16 was identified in 54% of invasive carcinomas, HPV 31, 33, 35, and 45 in 23%, "unidentified" HPV in 19%, and HPV 18 in 4% of invasive carcinomas. No significant associations were observed between P53 expression, Ki-67 expression, and HPV infection. In conclusion, we observed a high frequency of HPV infection in CIN III lesions and invasive carcinomas from Mozambican women, with HPV 16 representing the most frequent viral type. HPV status was not related to P53 and Ki-67 expression. Both P53 and Ki-67 are associated with invasive cervix carcinomas, mainly of the squamous keratinizing histotype. 相似文献
60.
Jak-3 is a non-receptor tyrosine kinase that plays an important role in coordinating signals received through a wide range of cytokine receptors, including the IL-7 receptor (IL-7R). Jak-3-deficient mice have a profound block in B cell development at the pro-to-pre-B cell transition and have very few peripheral B cells. This block has been postulated to reflect the inability of Jak-3(-/-) pro-B cells to respond to IL-7. Here we demonstrate that B cell development can be partially restored in Jak-3-deficient mice when they are bred to mice carrying both a rearranged Ig heavy chain (IgH/Igmu) transgene and a c-myc transgene expressed in the B cell lineage. Jak-3(-/-) mice expressing both of these transgenes exhibit significant increases in the number of B cells in the bone marrow and, to a lesser extent, in the spleen. However, very few rescued B cells were detectable in mice greater than 4 months of age. To determine whether resident hyperactivated Jak-3(-/-) peripheral T cells are responsible for the elimination of the rescued B cells in older mice, we bred IgH transgenic (Igmu Tg)/myc Tg/Jak-3(-/-) mice to T cell-deficient (TCRalpha(-/-)) mice. Data from these experiments suggest that the paucity of B cells in older Jak-3(-/-) mice is largely attributable to the lack of Jak-3 in the B cells themselves. Thus, Jak-3 seems to play several important roles in B cells: during development, to enable cell division, Ig gene rearrangement and cell differentiation, and in mature cells, to promote B cell survival in the periphery. 相似文献