全文获取类型
收费全文 | 8463篇 |
免费 | 404篇 |
国内免费 | 35篇 |
专业分类
耳鼻咽喉 | 177篇 |
儿科学 | 175篇 |
妇产科学 | 211篇 |
基础医学 | 963篇 |
口腔科学 | 195篇 |
临床医学 | 561篇 |
内科学 | 2292篇 |
皮肤病学 | 184篇 |
神经病学 | 739篇 |
特种医学 | 173篇 |
外科学 | 1166篇 |
综合类 | 66篇 |
预防医学 | 707篇 |
眼科学 | 191篇 |
药学 | 417篇 |
中国医学 | 37篇 |
肿瘤学 | 648篇 |
出版年
2023年 | 51篇 |
2022年 | 105篇 |
2021年 | 253篇 |
2020年 | 125篇 |
2019年 | 235篇 |
2018年 | 253篇 |
2017年 | 151篇 |
2016年 | 164篇 |
2015年 | 183篇 |
2014年 | 291篇 |
2013年 | 388篇 |
2012年 | 634篇 |
2011年 | 651篇 |
2010年 | 390篇 |
2009年 | 388篇 |
2008年 | 587篇 |
2007年 | 569篇 |
2006年 | 500篇 |
2005年 | 514篇 |
2004年 | 465篇 |
2003年 | 396篇 |
2002年 | 438篇 |
2001年 | 76篇 |
2000年 | 77篇 |
1999年 | 85篇 |
1998年 | 53篇 |
1997年 | 54篇 |
1996年 | 46篇 |
1995年 | 33篇 |
1994年 | 40篇 |
1993年 | 37篇 |
1992年 | 26篇 |
1991年 | 35篇 |
1990年 | 28篇 |
1989年 | 44篇 |
1988年 | 39篇 |
1987年 | 32篇 |
1986年 | 27篇 |
1985年 | 28篇 |
1984年 | 27篇 |
1982年 | 27篇 |
1980年 | 19篇 |
1979年 | 21篇 |
1978年 | 20篇 |
1976年 | 29篇 |
1975年 | 25篇 |
1974年 | 19篇 |
1973年 | 29篇 |
1971年 | 29篇 |
1970年 | 19篇 |
排序方式: 共有8902条查询结果,搜索用时 15 毫秒
31.
Emilia Lachica Aurelio Luna Enrique Villanueva 《International journal of legal medicine》1989,103(2):111-119
Summary The diagnosis of myocardial infarction requires the use of a group of tests that are very efficient, quick and inexpensive. Another important consideration is the choice of myocardial sampling zones, especially in cases of differential diagnosis between a cardiac injury secondary to a trauma or violent asphyxia and others, secondary to myocardial infarction. The aim of this work was to choose, through discriminant analysis, the most useful zones of cardiac tissue for the quantification of free fatty acids and free carnitine and for the performance of the K/Na quotient, as biochemical parameters for the postmortem diagnosis of myocardial infarction. According to the discriminant analysis performed, seven zones of cardiac tissue are necessary to achieve a differential diagnosis among myocardial infarction, other natural deaths, and violent deaths with a 71.9% efficacy. Greater diagnostic efficacy was found (78.1%) for differentiating between natural deaths and violent deaths.
Offprint requests to: E. Lachica 相似文献
32.
Intestinal microvillous disorders are an uncommon cause of severe diarrhea, with very poor prognosis. The authors report the case of a female infant with Down syndrome, aganglionic megacolon, severe diarrhea, and jejunal biopsy with ultrastructural changes consistent with microvillous atrophy. The patient condition improved after a colostomy performed in the setting of the treatment of Hirschprung disease. 相似文献
33.
Robert A. Kinsman Enrique Fernandez Marsha Schocket Jerald F. Dirks Nicholas A. Covino 《Journal of behavioral medicine》1983,6(4):339-357
Subjective symptoms and experiences were explored within a group of 146 severe, chronic bronchitis and emphysema patients. Eighty-nine symptoms and experiences, derived from initial interviews with 29 patients, were rated according to the frequency of occurrence during breathing difficulties. Key cluster analyses were used to derive a Bronchitis-Emphysema Symptom Checklist (BESC) measuring 11 symptom categories: Helplessness-Hopelessness, Decathexis, Fatigue, Poor Memory, Peripheral-Sensory Complaints, Dyspnea, Congestion, Sleep Difficulties, Irritability, Anxiety, and Alienation. The BESC symptom categories are highly reliable and the relationships among categories are stable across two subgroups of patients. The BESC provides one way to describe how patients cope with and experience chronic bronchitis and emphysema. 相似文献
34.
Jin YP Fishbein MC Said JW Jindra PT Rajalingam R Rozengurt E Reed EF 《Human immunology》2004,65(4):291-302
Anti-human leukocyte antigen (HLA) antibodies (Ab) have long been implicated in the process of acute and chronic allograft rejection, yet their mechanism(s) of action is not well understood. The aim of this study was to determine whether ligation of HLA class I molecules by anti-HLA Ab on the surface of human endothelial cells (EC) activates the PI3 Kinase (PI3K)/Akt signaling pathway and downstream target proteins of the cell death apparatus. We report that Ab ligation of major histocompatibility complex (MHC) class I molecules on the surface of EC triggers phosphorylation of Akt, PI3K, and recruitment of PI3K and Akt into a signaling unit with focal adhesion kinase. Signaling through class I also stimulated phosphorylation of Bad and upregulated expression of Bcl-2 and Bcl-xL. Pretreatment of EC with the PI3K inhibitor wortmannin blocked class I-mediated expression of Bcl-2, but not Bcl-xL, suggesting a role for the PI3K/Akt signaling pathway in regulation of class I-induced Bcl-2 expression. The intracellular events initiated by class I ligation were influenced by the concentration of the anti-HLA Ab with the lowest tested concentrations of Ab stimulating the highest level of Akt phosphorylation, Bcl-xL and Bcl-2 expression. Consistent with the in vitro experiments, analysis of biopsy samples from heart transplant recipients with evidence of Ab-mediated rejection exhibited increased Bcl-2 expression on the vascular endothelium. These results suggest that exposure of the graft endothelium to low concentrations of anti-HLA Ab may promote cell survival by transducing signals resulting in upregulation of cell survival genes. 相似文献
35.
M C Gornick Anjene Addington P Shaw A J Bobb W Sharp D Greenstein S Arepalli F X Castellanos J L Rapoport 《American journal of medical genetics. Part B, Neuropsychiatric genetics》2007,(3):379-382
Polymorphisms of the dopamine receptor D4 gene DRD4, 11p15.5, have previously been associated with attention-deficit/hyperactivity disorder (ADHD) [Bobb et al., 2005; Am J Med Genet B Neuropsychiatr Genet 132:109-125; Faraone et al., 2005; Biol Psychiatry 57:1313-1323; Thapar et al., 2005; Hum Mol Genet 14 Spec No. 2:R275-R282]. As a follow up to a pilot study [see Castellanos et al., 1998; Mol Psychiatry 3:431-434] consisting of 41 probands and 56 controls which found no significant association between the DRD4 7-repeat allele in exon 3 and ADHD, a greatly expanded study sample (cases n = 166 and controls n = 282) and long term follow-up (n = 107, baseline mean age n = 9, follow-up mean age of n = 15) prompted reexamination of this gene. The DRD4 7-repeat allele was significantly more frequent in ADHD cases than controls (OR = 1.2; P = 0.028). Further, within the ADHD group, the 7-repeat allele was associated with better cognitive performance (measured by the WISC-III) (P = 0.013-0.07) as well as a trend for association with better long-term outcome. This provides further evidence of the role of the DRD4 7-repeat allele in the etiology of ADHD and suggests that this allele may be associated with a more benign form of the disorder. 相似文献
36.
Fernández M Fernández G Diez-Ewald M Torres E Vizcaíno G Fernández N Narváez J Arteaga-Vizcaíno M 《Investigación clínica》2005,46(2):187-195
The increase of plasmatic homocysteine (Hc) in pregnant women, who later develop preeclampsia/eclampsia, the cause of this increment and its pathogenic role in toxemia of pregnancy, are still controversial. The objectives of the present research were to determine the plasmatic He concentrations during the first and second trimesters of pregnancy and the effect of folic acid administration on these values, and in the prevention of preeclampsia. Ninety six pregnant women of low economic background were studied on the first prenatal consultation: 27 women in the first trimester of pregnancy and 59 in the second. After 8 hours of fasting, venous blood was extracted and each patient was provided with 1 mg folic acid tablets and instructed to ingest one tablet daily, and to come back to the laboratory after three months. Plasma homocysteine and serum folic acid were determined for each patient before and after the folic acid treatment, by using the IMX system (Abbott Lab) and radioimmunoassay, respectively. Basal homocysteine concentrations were 4.0 +/- 2.1 micromol/L and 4.8 +/- 2.1 micromol/L in the first and second trimesters respectively, with no significant modifications after three months of folic acid. Although the degree of desertion from the study was high, it was possible to determine the evolution of 65 pregnancies. Ten of them developed preeclampsia (15.4%). No significant differences were found in Hc concentrations, or the frequency of hyperhomocysteinemia in the different stages of pregnancy, between women with normal gestation and those who developed preeclampsia. The small sample size of these groups, preclude any valid conclusion, however the results do not suggest that Hc concentration or folic acid administration influence the development of toxemia of pregnancy. 相似文献
37.
Holger Arndt Paul Kubes Matthew B. Grisham Enrique Gonzalez D. Neil Granger 《Inflammation》1992,16(5):549-559
The objective of this study was to determine the turnover rate of the extravascular pool of granulocytes in different regions of the feline gastrointestinal tract. Leukocyte emigration from the vasculature was prevented over a 48-h period by repeated intravenous injections of a monoclonal antibody (MAb IB4) directed against the leukocyte adhesion glycoprotein complex CD11/CD18. Tissue-associated myeloperoxidase (MPO) activity was used to monitor the total tissue granulocyte pool at 0.5, 12, 24, and 48 h after MAb IB4 administration. The mucosal layer of the duodenum, jejunum, ileum, and colon exhibited different kinetics of granulocyte clearance, with average life-spans (t1/2) ranging between 6.9 (colon) and 10.4 h (duodenum). Granulocyte clearance rates of 0.5 × 106 and 2.4 x 106 cells/h/g tissue were estimated (from measured values oft1/2 and tissue granulocyte pool) for the small bowel and colonie mucosae, respectively. The submucosal layer of the intestine exhibited a biphasic reduction in tissue MPO activity following immunoneutralization of CD11/CD18, with an initialt1/2 0.5 h followed by at1/2 of 36–60 h. The initial rapid decline in tissue MPO suggests that a significant fraction of granulocytes in the submucosa is localized in a readily exchangeable pool (e.g., marginated cells within the vasculature). The results of this study indicate that the average life-span of resident granulocytes varies significantly between different regions of the gastrointestinal tract, with the intestinal mucosa exhibiting at1/2 comparable to that previously reported for circulating feline neutrophils (R 8 h). 相似文献
38.
Federico Ferrando-Castagnetto Enrique Macri Alejandro Silva Darío Padula Gastón Garcés 《Educación Médica》2019
Introduction
Although an objective structured clinical examination (OSCE) format has been applied in Uruguay since 2004, and providing reliable performance measures, perceptions of it properties and level of student satisfaction have not been determined.Objective
To evaluate the face validity of OSCE format as a contribution to its local feasibility study.Material and methods
At the end of the introductory clinical course, the sub-cohort enrolled at the University Hospital responded to a 28-item questionnaire aimed at exploring perceptions about the properties of the OSCE about the potential factors ‘design’ and ‘apparent validity’. After analysing the reliability of the original questionnaire, the questionnaire was refined in an attempt to provide a shorter and more reliable tool.Results
The original questionnaire showed good internal consistency (Cronbach alpha = 0.70), with a dominance of ‘agreement/total agreement’ opinions on authenticity of the stimuli, dynamic, relevance, and equity of the test. Students perceived organisational obstacles during the test, expressing disagreement to include some stations only aimed at assessing communication skills, and requiring personalised feedback sessions. The refined version of the questionnaire provides consistent measures on student perceptions and is a useful tool that can be widely applied. A discussion is presented on the contributions of this experience to a comprehensive feasibility study of the new format during curriculum transition.Conclusions
The OSCE is well evaluated by students at the end of the propaedeutic course, supporting its validity. Educational potentials of the new format should be exploited, providing effective feedback to students, clinical teachers, and institutions. 相似文献39.
Martinez-Marcos A Ubeda-Bañon I Lanuza E Halpern M 《Journal of chemical neuroanatomy》2005,29(1):49-69
The olfactostriatum, a portion of the striatal complex of snakes, is the major tertiary vomeronasal structure in the ophidian brain, receiving substantial afferents from the nucleus sphericus, the primary target of accessory olfactory bulb efferents. In the present study, we have characterized the olfactostriatum of garter snakes (Thamnophis sirtalis) on the basis of chemoarchitecture (distribution of serotonin, neuropeptide Y and tyrosine hydroxylase) and hodology (afferent connections). The olfactostriatum is densely immunoreactive for serotonin and neuropeptide Y and shows moderate-to-weak immunoreactivity for tyrosine hydroxylase. In addition to afferents from the nucleus sphericus, the olfactostriatum receives inputs from the dorsal and lateral cortices, nucleus of the accessory olfactory tract, external and dorsolateral amygdalae, dorsomedial thalamic nucleus, ventral tegmental area and raphe nuclei. Double labeling experiments demonstrated that the distribution of serotonin and neuropeptide Y in this area almost completely overlaps the terminal field of projections from the nucleus sphericus. Also, serotonergic and dopaminergic innervation of the olfactostriatum likely arise, respectively, from the raphe nuclei and the ventral tegmental area, whereas local circuit neurons originate the neuropeptide Y immunoreactivity. These results indicate that the olfactostriatum of snakes could be a portion of the nucleus accumbens, with features characteristic of the accumbens shell, devoted to processing vomeronasal information. Comparative data suggest that a similar structure is present in the ventral striatum of amphibians and mammals. 相似文献
40.
Velayos A Fuentes-Vicente M Aguilar-Elena R Eslava AP Iturriaga EA 《Current genetics》2004,45(6):371-377
Two Mucor circinelloides
structural genes involved in isoprenoid biosynthesis were isolated and characterised. The isoA gene encodes a typical eukaryotic farnesyl diphosphate synthase (EC 2.5.1.10), whereas the isoB gene deduced amino acid sequence shows similarity to fungal medium-chain prenyl diphosphate synthases. By functional complementation in Escherichia coli, the isoB gene product was shown to be a solanesyl diphosphate synthase (EC 2.5.1.11), which is the first fungal enzyme reported having this specificity. In addition, a M. circinelloides one-marker-per-chromosome map was completed by contour-clamped homogeneous electric field localisation of isoA, isoB and three other isoprenoid biosynthesis genes to individual chromosomes.Abbreviations FPP
farnesyl diphosphate (or pyrophosphate)
- GGPP
geranylgeranyl diphosphate
- PrenylPP
prenyl diphosphate
- DPP
decaprenyl diphosphate
- HPP
hexaprenyl diphosphate
- SPP
solanesyl diphosphate 相似文献