全文获取类型
收费全文 | 2101篇 |
免费 | 158篇 |
国内免费 | 7篇 |
专业分类
耳鼻咽喉 | 27篇 |
儿科学 | 75篇 |
妇产科学 | 62篇 |
基础医学 | 289篇 |
口腔科学 | 43篇 |
临床医学 | 119篇 |
内科学 | 619篇 |
皮肤病学 | 56篇 |
神经病学 | 167篇 |
特种医学 | 36篇 |
外科学 | 254篇 |
综合类 | 12篇 |
一般理论 | 1篇 |
预防医学 | 182篇 |
眼科学 | 34篇 |
药学 | 163篇 |
中国医学 | 23篇 |
肿瘤学 | 104篇 |
出版年
2023年 | 11篇 |
2022年 | 17篇 |
2021年 | 48篇 |
2020年 | 25篇 |
2019年 | 48篇 |
2018年 | 92篇 |
2017年 | 41篇 |
2016年 | 53篇 |
2015年 | 49篇 |
2014年 | 66篇 |
2013年 | 84篇 |
2012年 | 131篇 |
2011年 | 141篇 |
2010年 | 64篇 |
2009年 | 49篇 |
2008年 | 108篇 |
2007年 | 138篇 |
2006年 | 122篇 |
2005年 | 133篇 |
2004年 | 130篇 |
2003年 | 109篇 |
2002年 | 107篇 |
2001年 | 53篇 |
2000年 | 77篇 |
1999年 | 57篇 |
1998年 | 19篇 |
1997年 | 9篇 |
1996年 | 13篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 38篇 |
1991年 | 32篇 |
1990年 | 20篇 |
1989年 | 15篇 |
1988年 | 18篇 |
1987年 | 23篇 |
1986年 | 13篇 |
1985年 | 17篇 |
1984年 | 10篇 |
1983年 | 11篇 |
1981年 | 6篇 |
1979年 | 4篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1971年 | 6篇 |
1969年 | 3篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1966年 | 4篇 |
排序方式: 共有2266条查询结果,搜索用时 15 毫秒
11.
Marín N Romero B Bosch-Morell F Llansola M Felipo V Romá J Romero FJ 《Mechanisms of ageing and development》2000,119(1-2):63-67
It is known that beta-amyloid peptide (Abeta) contributes to the neurodegeneration in Alzheimer's disease (AD) and operates through activation of an apoptotic pathway. Apoptotic signal is driven by a family of cysteine proteases called caspases. The beta-amyloid precursor protein (APP) is directly and efficiently cleaved by caspases during apoptosis, resulting in elevated beta-amyloid peptide formation. Cerebellar neurons from rat pups were treated with the aged Abeta(25-35) at 1 and 5 microM and fluorescence assays of caspase activity performed over 4 days. We observed an increase in caspase activity after 48 h treatment in both 1 and 5 microM treated cells, then (72-96 h) caspase activity decreased to control values. The data presented support the hypothesis that Abeta(25-35)-induced apoptosis is mediated by the activation of Caspase-3 and that this is a transient effect. 相似文献
12.
Constitutional t(15;17) 总被引:2,自引:0,他引:2
13.
Vázquez B Ortíz C San Román J Plasencia MA López-Bravo A 《Journal of biomaterials applications》2000,15(2):118-139
Vitamin E containing copolymers for biomedical applications was obtained by copolymerization reaction of vitamin E methacrylate (VEMA) with 2-hydroxyethyl methacrylate (HEMA), N,N-dimethyl acrylamide (DMA) or vinyl pyrrolidone (VP), in different experiments. High molecular weight copolymers prepared by free radical reactions initiated by azobisisobutironitrilo, AIBN, present a random distribution of vitamin E derivatives along the macromolecular chains, and the average composition depends on the initial composition of the reaction medium. The relative flexibility of the polymeric systems was analyzed measuring the glass transition temperature of copolymeric sequences and that of the pure alternating diad (Tg12) obtained by the application of the treatments proposed by Johnston and Barton to all the systems. Tg12 was higher than the average T of both homopolymers (Tg) for the VEMA-HEMA system, Tg12 was lower than Tg for the VEMA-DMA system and Tg12 was similar to Tg for the VEMA-VP system. VEMA-HEMA copolymers gave rise to hydrogels in water, acidic and alkaline media. VEMA-DMA copolymers gave rise to hydrogels in acidic medium and dissolved in water and alkaline medium. VEMA-VP copolymers were soluble in all media. The swelling of all the hydrogels fit a second order kinetics. A VEMA-HEMA hydrogel was selected for in vivo experiments in order to study the influence of vitamin E on the regeneration process of Achilles tendon. The polymeric derivatives of vitamin E stimulated the regenerative process as a consequence of the antiaging effect in the local area of application. 相似文献
14.
J. Fortún A. López -San Román J. J. Velasco A. Sánchez-Sousa E. de Vicente J. Nuño C. Quereda R. Bárcena G. Monge A. Candela A. Honrubia A. Guerrero 《European journal of clinical microbiology & infectious diseases》1997,16(4):314-318
The cases of four liver transplant recipients who developed invasive candidiasis (2 cholangitis, 1 perihepatic abscess, 1 candidemia) due to azole-resistantCandida glabrata are reported. Three patients were receiving azolic compounds (2 itraconazole, 1 fluconazole) when the infection was diagnosed. All four patients received fluconazole as intestinal decontamination during the first three weeks post transplantation. The infections occurred two months after transplantation in all patients, and in one patientCandida infection was the direct cause of death. Infection of the biliary tree was the origin of candidiasis in three patients; the fourth patient developed neutropenic-related candidemia. Fluconazole MICs exceeded 16 g/ml in all cases; itraconazole MICs were 16, 2, 1, and 2 g/ml, respectively. The potential role ofCandida species other thanalbicans in these patients after administration of azole agents is discussed. 相似文献
15.
Laboratory detection of Haemophilus influenzae with decreased susceptibility to nalidixic acid, ciprofloxacin, levofloxacin, and moxifloxacin due to GyrA and ParC mutations 下载免费PDF全文
Pérez-Vázquez M Román F Aracil B Cantón R Campos J 《Journal of clinical microbiology》2004,42(3):1185-1191
The detection of clinical isolates with decreased fluoroquinolone susceptibilities and a resistance mechanism is of epidemiological and clinical interest. We studied the susceptibilities of 62 clinical isolates and 2 American Type Culture Collection reference strains of Haemophilus influenzae to ciprofloxacin, levofloxacin, moxifloxacin, and nalidixic acid by the microdilution and disk diffusion methods. The ciprofloxacin MICs for 34 of the isolates were >/=0.12 micro g/ml (range, 0.12 to 32 micro g/ml), and the ciprofloxacin MICs for 28 matched control isolates were =0.06 micro g/ml. In addition, we sequenced the quinolone resistance-determining regions (QRDRs) of gyrA and parC of all strains. The log(2) MICs of all quinolones were plotted against the inhibition zone diameters. The MICs and inhibition zone diameters selected to screen for the resistance mechanism were based on the susceptibility distribution data and the presence or absence of amino acid changes in the QRDRs of GyrA and ParC. Strains for which ciprofloxacin MICs were =0.06 micro g/ml, levofloxacin and moxifloxacin MICs were =0.03 micro g/ml, and nalidixic acid MICs were =2.0 micro g/ml lacked modifications in the QRDR of GyrA. In contrast, all strains for which ciprofloxacin, levofloxacin, and moxifloxacin MICs were >/=0.5 micro g/ml and the vast majority of those for which nalidixic acid MICs were >/=32 micro g/ml exhibited amino acid changes in GyrA and ParC. Nalidixic acid and the other three fluoroquinolones studied could be used to screen H. influenzae isolates for the detection of decreased susceptibilities to quinolones due to the acquisition of two amino acid changes in the QRDRs of GyrA and ParC (sensitivity, >95%; specificity, >80%). 相似文献
16.
Pirie FJ Pegoraro R Motala AA Rauff S Rom L Govender T Esterhuizen TM 《Tissue antigens》2005,66(2):125-130
Type 1 diabetes is the consequence of exposure of genetically susceptible individuals to specific environmental precipitants. The innate immune system provides the initial response to exogenous antigen and links with the adaptive immune system. The aim of this study was to assess the role of polymorphisms occurring in the cytoplasmic region of toll-like receptor (TLR) 3 gene and immediate 5' sequence, in subjects of Zulu descent with type 1 diabetes in KwaZulu-Natal, South Africa. Seventy-nine subjects with type 1 diabetes and 74 healthy normal glucose tolerant gender-matched control subjects were studied. Parts of exon 4 and exon 3/intron 3 of the TLR3 gene were studied by polymerase chain reaction, direct sequencing and restriction enzyme digestion with Bts 1. Of the nine polymorphisms studied, a significant association with type 1 diabetes was found for the major allele in the 2593 C/T polymorphism and for the minor alleles in the 2642 C/A and 2690 A/G polymorphisms, which were found to be in complete linkage disequilibrium. Correction of the P-values for the number of alleles studied, however, rendered the results no longer significant. These results suggest that polymorphisms in the TLR3 gene, which is part of the innate immune system, may be associated with type 1 diabetes in this population. 相似文献
17.
Dennis Vestergaard Pedersen Josefine Lorentzen Gregers Rom Andersen 《Immunological reviews》2023,313(1):46-59
Structures of alternative pathway proteins have offered a comprehensive structural basis for understanding the molecular mechanisms governing activation and regulation of the amplification pathway of the complement cascade. Although properdin (FP) is required in vivo to sustain a functional alternative pathway, structural studies have been lagging behind due to the extended structure and polydisperse nature of FP. We review recent progress with respect to structure determination of FP and its proconvertase/convertase complexes. These structures identify in detail regions in C3b, factor B and FP involved in their mutual interactions. Structures of FP oligomers obtained by integrative studies have shed light on how FP activity depends on its oligomerization state. The accumulated structural knowledge allows us to rationalize the effect of point mutations causing FP deficiency. The structural basis for FP inhibition by the tick CirpA proteins is reviewed and the potential of alphafold2 predictions for understanding the interaction of FP with other tick proteins and the NKp46 receptor on host immune cells is discussed. The accumulated structural knowledge forms a comprehensive basis for understanding molecular interactions involving FP, pathological conditions arising from low levels of FP, and the molecular strategies used by ticks to suppress the alternative pathway. 相似文献
18.
Saint-Félix D Trousset Y Picard C Ponchut C Roméas R Rougée A 《Physics in medicine and biology》1994,39(3):583-595
A new system has been designed and built to validate the concept of 3D computerized angiography (CA). This system can acquire a set of 2D digital subtracted angiography images while rotating around a patient and then, using these images, reconstruct a 3D representation of the opacified vasculature. The design principles and main characteristics of the system are described, with special attention paid to data processing aspects. An initial in vivo evaluation of this system performed on anaesthetized animals and human volunteers is presented. The influence on the quality of the 3D reconstruction of different factors such as volume resolution, estimation method, source trajectory and number of projections is discussed. 相似文献
19.
From acetone extracts of the exudate of the tree BURSERA ARIENSIS, a new bilignan, named ariensin, has been isolated and characterized as (2R,3R)-bis-2.3-(3.4-methylenedioxybenzyl-)-1.4-butanediol diacetate. The structure has been determined from UV, IR, (1)H-NMR and (13)C-NMR data of the natural product, the dibromo derivative and the hydrolysis product. The optical rotation of the latter allowed the determination of the absolute configuration. 相似文献
20.
J. W. Everts K. van Frankenhuyzen B. Román J. H. Koeman 《Archives of environmental contamination and toxicology》1983,12(1):91-97
During tsetse control operations near Bouaflé, Ivory Coast, Africa, a study was made of environmental side-effects of helicopter sprayings with permethrin and deltamethrin on a riverine forest. Terrestrial and aquatic arthropod populations and fish were observed for acute effects. The abundance of the species was assessed by various trapping devices before, during, and after the spraying cycle. Populations of mayfly-larvae and small shrimps (Caridina africana) were virtually eliminated after the spraying cycle. TheEphemeroptera recovered within the same season. Caddis-fly andSimulium-larvae populations were affected but they recovered within each spraying interval. Large shrimps (Macrobrachium vollenhovenii) were paralyzed by the insecticide. Recovery occurred within 48 hr. Among the terrestrial arthropods, the hymenopteran and dipteran populations were significantly affected. No effect was observed on bottom dwelling spiders. The ability of the ecosystems to recover from the disturbance is discussed. 相似文献