全文获取类型
收费全文 | 62239篇 |
免费 | 5086篇 |
国内免费 | 2218篇 |
专业分类
耳鼻咽喉 | 578篇 |
儿科学 | 1197篇 |
妇产科学 | 1186篇 |
基础医学 | 6434篇 |
口腔科学 | 1181篇 |
临床医学 | 7028篇 |
内科学 | 11559篇 |
皮肤病学 | 1383篇 |
神经病学 | 3366篇 |
特种医学 | 1427篇 |
外国民族医学 | 6篇 |
外科学 | 6819篇 |
综合类 | 7938篇 |
现状与发展 | 8篇 |
一般理论 | 9篇 |
预防医学 | 5478篇 |
眼科学 | 1352篇 |
药学 | 5897篇 |
68篇 | |
中国医学 | 3214篇 |
肿瘤学 | 3415篇 |
出版年
2024年 | 197篇 |
2023年 | 778篇 |
2022年 | 1865篇 |
2021年 | 2918篇 |
2020年 | 2079篇 |
2019年 | 1935篇 |
2018年 | 2110篇 |
2017年 | 1935篇 |
2016年 | 1659篇 |
2015年 | 2488篇 |
2014年 | 3247篇 |
2013年 | 3823篇 |
2012年 | 5652篇 |
2011年 | 5680篇 |
2010年 | 4018篇 |
2009年 | 3488篇 |
2008年 | 4208篇 |
2007年 | 4135篇 |
2006年 | 3579篇 |
2005年 | 3263篇 |
2004年 | 2435篇 |
2003年 | 2320篇 |
2002年 | 1839篇 |
2001年 | 606篇 |
2000年 | 489篇 |
1999年 | 376篇 |
1998年 | 290篇 |
1997年 | 270篇 |
1996年 | 240篇 |
1995年 | 194篇 |
1994年 | 163篇 |
1993年 | 124篇 |
1992年 | 112篇 |
1991年 | 76篇 |
1990年 | 84篇 |
1989年 | 71篇 |
1988年 | 62篇 |
1987年 | 61篇 |
1986年 | 64篇 |
1985年 | 50篇 |
1984年 | 47篇 |
1983年 | 42篇 |
1982年 | 60篇 |
1981年 | 67篇 |
1980年 | 36篇 |
1979年 | 40篇 |
1978年 | 21篇 |
1977年 | 32篇 |
1976年 | 33篇 |
1975年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
C. P. MULLER T. SCHROEDER R. TU N. H C. BRONS G. JUNG F. SCHNEIDER K. H. WIESMÜLLER 《Scandinavian journal of immunology》1993,38(5):463-471
Infection or immunization with measles virus induces a protective immune reaction including neutralizing antibodies against the haemagglutinin and fusion protein. The reactivity of the polyclonal IgG response of sera obtained from late convalescent donors was studied, using overlapping 15mer peptides covering the complete sequence of the measles virus haemagglutinin. Most sera reacted with a similar set of peptides generating a characteristic binding pattern. The reactive peptides correspond to a region mediating cell hemolysis (aa310–325), to regions which serve as targets to neutralizing antibodies and to a putative transmembrane region (aa35–58). The latter region contains also a human T-cell epitope providing evidence of a non-random association of T- and B-cell epitopes. We also immunized different strains of mice and rabbits with measles virus. In contrast to the human sera, animal sera with strong neutralizing activities did not react with any of the H-protein peptides. The mostly weak reactivities with the linear sequences contrast with the strong neutralizing activities of the human or animal antibodies, suggesting that these primarily recognize the fusion protein or conformational epitopes of the haemagglutinin protein. 相似文献
52.
Francisco Camacho Juan Ferrando Antonio R. Pichardo Ismael Sotillo Enrique Jorquera 《Pediatric dermatology》1993,10(1):54-57
Abstract: A 20-year-old woman and her 12-year-old brother had hypohidrotic ectodermal dysplasia, cleft lip and palate, midfacial hypoplasia with narrow nose from the nasal bridge to the tip, narrow dysplastic nails, and conical teeth and hypodontia, and hypospadias and hypoplastic uvula in the boy. The woman had major underdevelopment of intellectual capacity. The most important hair anomalies in both siblings were sparse eyebrows, pili torti, and pili canaliculi. Some of the pili canaliculi had two canals (pili bicanaliculi), and the cross section for scanning electron microscopy had a quadrangular aspect. This is the seventh family reported with Rapp-Hodgkin ectodermal dysplasia. 相似文献
53.
Mitchell Koolpe Juan J. Rodrigo Hilary P. Benton 《Journal of orthopaedic research》1998,16(2):217-226
Small calcium-mobilizing inflammatory mediators have been implicated in joint pathology. Here we demonstrate that bradykinin, adenosine 5′-triphosphate, uridine 5′-triphosphate, and lysophosphatidic acid raise the intracellular calcium concentration ([Ca2+]i) in human articular chondrocytes. Heterologous cross-desensitization experiments showed that the uridine 5′-triphosphate response was abolished by prior treatment with adenosine 5′-triphosphate and conversely, that the adenosine 5′-triphosphate response was abolished by prior treatment with uridine 5′-triphosphate: this indicated competition for the same receptor site, whereas bradykinin and lysophosphatidic acid did not compete with other ligands. Pretreatment with thapsigargin abolished ligand-mediated Ca2+ responses but not vice versa: this confirmed that Ca2+ release occurred from intracellular stores. Single-cell analysis of Fura-2 acetoxymethyl ester loaded chondrocytes showed mediator-dependent patterns of oscillatory Ca2+ changes in a subset of cells when challenged with submaximal concentrations of bradykinin, adenosine 5′-triphosphate, or uridine 5′-triphosphate in the presence of extracellular Ca2+. However, no oscillatory responses were seen after a challenge with lysophosphatidic acid. Therefore, although a number of different Ca2+-mobilizing ligands activate chondrocytes, the differences that occur in the temporal patterning of Ca2+ responses may result in unique mediator-dependent changes in cellular activity. 相似文献
54.
目的:探究11β-羟化类固醇脱氢酶1(11β-hydroxysteroid dehydrogenase,11β-HSD1)基因敲除对小鼠整体代谢和认知功能的影响。方法:将C57BL/6J为遗传背景的野生对照组及11β-HSD1基因敲除组各15只小鼠高脂喂养20周,代谢笼评估能量代谢,行为学评估观察小鼠认知功能,电镜评估海马体的线粒体结构,免疫荧光及PCR确定其认知功能、线粒体功能相关基因及炎症基因的变化。结果:11β-HSD1基因敲除能够提高高脂喂养小鼠学习和记忆能力,改善握力,改善海马体的微结构、线粒体含量变多,认知相关基因、线粒体呼吸功能相关基因上调,炎症相关基因改变。结论:11β-HSD1敲除后高脂饮食喂养小鼠认知功能显著改善,握力显著提高,可能是治疗认知功能障碍的有效靶点。 相似文献
55.
The goal of IMRT is to achieve an isodose distribution conformed to the tumor while avoiding the organs at risk. For these tasks several gantry angles are selected, each one containing a series of different leaf configurations for the multileaf collimator (MLC) (segments). Verifying the relative distributions as well as the absolute doses is an important step for quality assurance issues. We have observed that an accurate modeling of the transmission of the primary x-ray fluence through the jaws and MLC as well as the head scatter is crucial for a precise calculation of relative doses and monitor units. Also, an inaccurate calculation of the output factor for small size segments can lead to important differences in the absolute dose for points under these segments. Incorrect models could lead to systematic errors of around 5% to 10% in the calculated monitor units and a shift in the isodose curves. 相似文献
56.
Erik Diaz Teresa Gonzlez-Cossío Juan Rivera Maarten D. C. Immink Ruben Dario Mendoza C. Rafael Flores 《American journal of human biology》1991,3(5):525-530
This study aims at assessing the accuracy of estimates of body composition provided by bioimpedance (BIA) equations developed for U.S. populations when applied to a sample of Guatemalan farmers. If these equations were shown to have low validity, the second objective was to develop more accurate estimates of fat-free mass (FFM). One hundred males and females 19 to 45 years of age were randomly selected from four rural communities in the Western Highlands of Guatemala. Bioimpedance equations explained 59 and 33% of the variation in FFM, with a RMSE of 2.7 and 2.8 kg in males and females, respectively. Body fat (BF) predictions had a lower R2. Using the “all possible regressions” procedure, the best subset for prediction of FFM used anthropometric and BIA variables as predictors. The best model for men and women included only anthropometric variables: 75% of the variance in FFM for men and 70% of the variance in women was explained by this model. The RMSE was 2.1 and 1.9 kg for both groups, respectively. It is concluded that FFM can be estimated from anthropometric dimensions with a high degree of accuracy and use of BIA does not provide more valid estimates. 相似文献
57.
Systematic changes in gene expression in postmortem human brains associated with tissue pH and terminal medical conditions 总被引:8,自引:0,他引:8
58.
Evolution of foot-and-mouth disease virus 总被引:28,自引:0,他引:28
Domingo E Escarmís C Baranowski E Ruiz-Jarabo CM Carrillo E Núñez JI Sobrino F 《Virus research》2003,91(1):47-63
Foot-and-mouth disease virus evolution is strongly influenced by high mutation rates and a quasispecies dynamics. Mutant swarms are subjected to positive selection, negative selection and random drift of genomes. Adaptation is the result of selective amplification of subpopulations of genomes. The extent of adaptation to a given environment is quantified by a relative fitness value. Fitness values depend on the virus and its physical and biological environment. Generally, infections involving large population passages result in fitness gain and population bottlenecks lead to fitness loss. Very different types of mutations tend to accumulate in the foot-and-mouth disease virus (FMDV) genome depending on the virus population size during replication. Quasispecies dynamics predict higher probability of success of antiviral strategies based on multivalent vaccines and combination therapy, and this has been supported by clinical and veterinary practice. Quasispecies suggest also new antiviral strategies based on virus entry into error catastrophe, and such procedures are under investigation. Studies with FMDV have contributed to the understanding of quasispecies dynamics and some of its biological implications. 相似文献
59.
目的 探讨力竭游泳对大鼠胃肠道 5 HT免疫反应细胞 (5 HTIR细胞 )的影响。方法 本研究以力竭游泳大鼠为运动模型 ,游泳后即刻取大鼠胃窦、十二指肠、空肠和回肠用免疫组织化学SP法检测 5 HT ,用图像分析系统测定胃肠 5 HTIR细胞数和平均灰度。结果 (1)游泳后胃窦 5 HTIR细胞数虽与对照组无明显差异 ,但阳性细胞的平均灰度却明显下降 (P <0 .0 5)。 (2 )十二指肠、空肠、回肠 5 HTIR细胞数都明显下降 ,与对照组相比有显著性差异 (P <0 .0 5) ,但只有空肠 5 HTIR细胞平均灰度明显增加 ,与对照组间有明显差异 (P <0 .0 5)。结果 胃肠道不同区域 5 HTIR细胞以不同的反应方式应答运动应激。 相似文献
60.
Juan Tentoni Nélida Nora Polini Emma Beatriz Casanave 《Comparative clinical pathology》2008,17(3):193-196
The fibrinolytic mechanism in the armadillo Chaetophractus villosus (Mammalia, Xenarthra, Dasypodidae) quite unknown until now was studied. Results were compared with those corresponding to
healthy adult human beings. Whole blood lysis time and diluted blood lysis time were not detectable in armadillos. Euglobulin
clot lysis time and plasminogen activity (Plg) were lower than in healthy humans. We established the presence of the fibrinolytic
system in Ch. villosus through the measurement of fibrin fibrinogen degradation products. The activity of the plasminogen activator inhibitor was
two to four times greater than in healthy humans. The activity of the alpha 2 anti-plasmin (α2AP) was similar and displaced
toward lower values. The Plg/α2AP relation was lower. The results obtained suggest that Ch. villosus has a hypercoagulable and hypofibrinolytic profile. Our findings are not only the first contribution to elucidate the physiology
of the fibrinolytic system in Xenarthra but also contribute to develop an animal model for studies in haemostasis and thrombosis. 相似文献