全文获取类型
收费全文 | 3114篇 |
免费 | 103篇 |
国内免费 | 20篇 |
专业分类
耳鼻咽喉 | 23篇 |
儿科学 | 37篇 |
妇产科学 | 49篇 |
基础医学 | 425篇 |
口腔科学 | 42篇 |
临床医学 | 328篇 |
内科学 | 672篇 |
皮肤病学 | 16篇 |
神经病学 | 356篇 |
特种医学 | 89篇 |
外科学 | 510篇 |
综合类 | 5篇 |
一般理论 | 1篇 |
预防医学 | 177篇 |
眼科学 | 23篇 |
药学 | 257篇 |
中国医学 | 2篇 |
肿瘤学 | 225篇 |
出版年
2023年 | 13篇 |
2022年 | 25篇 |
2021年 | 57篇 |
2020年 | 25篇 |
2019年 | 39篇 |
2018年 | 71篇 |
2017年 | 26篇 |
2016年 | 45篇 |
2015年 | 61篇 |
2014年 | 97篇 |
2013年 | 162篇 |
2012年 | 217篇 |
2011年 | 249篇 |
2010年 | 113篇 |
2009年 | 121篇 |
2008年 | 238篇 |
2007年 | 237篇 |
2006年 | 236篇 |
2005年 | 217篇 |
2004年 | 217篇 |
2003年 | 204篇 |
2002年 | 221篇 |
2001年 | 29篇 |
2000年 | 29篇 |
1999年 | 32篇 |
1998年 | 48篇 |
1997年 | 45篇 |
1996年 | 22篇 |
1995年 | 20篇 |
1994年 | 21篇 |
1993年 | 12篇 |
1992年 | 19篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 7篇 |
1985年 | 2篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1964年 | 1篇 |
1963年 | 1篇 |
1961年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有3237条查询结果,搜索用时 15 毫秒
1.
2.
3.
The immune response of Drosophila melanogaster 总被引:4,自引:0,他引:4
Summary: The response of the fruit fly Drosophila melanogaster to various microorganism infections relies on a multilayered defense. The epithelia constitute a first and efficient barrier. Innate immunity is activated when microorganisms succeed in entering the body cavity of the fly. Invading microorganisms are killed by the combined action of cellular and humoral processes. They are phagocytosed by specialized blood cells, surrounded by toxic melanin, or lysed by antibacterial peptides secreted into the hemolymph by fat body cells. During the last few years, research has focused on the mechanisms of microbial recognition by various pattern recognition receptors and of the subsequent induction of antimicrobial peptide expression. The cellular arm of the Drosophila innate immune system, which was somehow neglected, now constitutes the new frontier. 相似文献
4.
5.
Propriospinal myoclonus: utility of magnetic resonance diffusion tensor imaging and fiber tracking. 总被引:1,自引:0,他引:1
Emmanuel Roze Emmanuelle Apartis Marie Vidailhet Valérie Cochen Yara Beaugendre Jean-Marc Trocello Pierre Lasjaunias Denis Ducreux 《Movement disorders》2007,22(10):1506-1509
Propriospinal myoclonus (PSM) is a rare movement disorder characterized by involuntary spinal-generated muscular jerks that spread rostrally and caudally to other spinally innervated muscles. Most patients have no clear etiology, and conventional MRI of the spinal cord is generally normal. Here we report the use of magnetic resonance diffusion tensor imaging (DTI) and fiber tracking to detect tract-specific abnormalities in a patient with propriospinal myoclonus. As the patient had the fragile-X premutation and antithyroid antibodies, spinal cord DTI abnormalities may be related to these conditions. Tract-specific analysis may provide new insights into the pathophysiology of propriospinal myoclonus. 相似文献
6.
Claire Corot Jean-Marc Idee Anne-Marie Hentsch Robin Santus Catherine Mallet Valrie Goulas Bruno Bonnemain Dominique Meyer 《Journal of magnetic resonance imaging : JMRI》1998,8(3):695-702
Transmetallation between commercially available solutions of gadolinium (Gd) chelates and the zinc (Zn)-dependent angiotensin-converting enzyme (ACE) was investigated. In vitro, the strongest inhibitions were observed for the linear Gd complexes, Gd diethylene-triamine pentaacetic acid (DTPA) bis-methylamide (BMA) (IC50 = .016 ± .006 mmol/1) and Gd-DTPA (IC50 = .350 ± .034 mmol/1). The two macrocycles Gd tetraazacyclododecane tetraacetic acid (DOTA) and Gd-HP-DO3A were similar and 400 times less active than Gd-DTPA-BMA. These effects were mainly due to the presence of free ligand for DTPA and calcium (Ca) chelate in the case of DTPA-BMA because the addition of Zn2+ in the same quantities suppresses their inhibitory effects. In vivo, these two solutions of linear Gd chelates significantly inhibited ACE activity (Gd-DTPA: 67 ± 9% versus baseline; and Gd-DTPA-BMA: 73 ± 2% versus baseline at the clinical dose of .1 mmol/kg), whereas no significant effect was observed for the two macrocyclic chelates Gd-DOTA and Gd-HP-DO3A. Formulating the Gd chelate solution with either an excess of free ligand or Ca chelate (to decrease Gd3+ release) in the case of linear Gd chelate may have deleterious biologic consequences. 相似文献
7.
Assessment of virulence of pigeon isolates of Salmonella enterica subsp. enterica serovar typhimurium variant copenhagen for humans
下载免费PDF全文
![点击此处可从《Journal of clinical microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Pasmans F Van Immerseel F Hermans K Heyndrickx M Collard JM Ducatelle R Haesebrouck F 《Journal of clinical microbiology》2004,42(5):2000-2002
Salmonella enterica serovar Typhimurium variant Copenhagen was isolated from 5 of 152 (3.3%) feral pigeons from the city of Ghent (Belgium) and from 26 pooled fecal samples from 114 pigeon lofts (22.8%). These isolates belonged to phage type (PT) 99. Seven of the pigeon isolates were further compared in vitro to five human variant Copenhagen isolates, 2 isolates of PT 208, 1 isolate each of PT 120 and U302, and a nontypeable isolate. No differences in invasiveness in human intestinal epithelial Caco-2 cells were found. The human strains, however, were able to multiply significantly more inside human THP-1 macrophages than the pigeon strains. After inoculation of mice with a pigeon PT 99 strain, high numbers of Salmonella bacteria were shed with the feces, the internal organs were heavily colonized, and the animals showed severe clinical symptoms resulting in death. In conclusion, the less-pronounced ability of the pigeon variant Copenhagen strains to multiply inside human macrophages than human strains as well as the lack of human PT 99 isolates during 2002, despite the relatively high frequency of this PT in the pigeon population, suggest these strains to be of low virulence to humans. However, the high virulence for mice of the tested strain implies that rodents may act as reservoirs. 相似文献
8.
Derothe JM Porcherie A Perriat-Sanguinet M Loubès C Moulia C 《Parasitology research》2004,93(5):356-363
The susceptibility to Aspiculuris tetraptera of European Mus musculus hybrids is thought to reflect the disruption of genomic co-adaptation through recombination of the parental genomes. Here, we compared the susceptibility to this parasite between parents and experimental hybrids (intersubspecific until F4, intrasubspecific F1, F2) to clarify the contributions of heterosis and subspecies incompatibility. F1 showed hybrid vigor. Unlike intrasubspecific F2, intersubspecific F2 were less resistant than F1, but revealed no increased susceptibility relative to the parents. Intersubspecific F3 and F4 showed the same hybrid vigor as F1. Heterosis contributed most to the resistance, but the differences between intra- and intersubspecific F2 suggested genomic incompatibilities between subspecies. However, the susceptibility did not increase through the recombination process, showing that disruption of co-adaptation does not directly affect resistance. Even if previous studies still support the selective role of parasites in the current hybrid zone, an alternative hypothesis on the origin of hybrid susceptibility is warranted. 相似文献
9.
Delaugerre C Teglas JP Treluyer JM Vaz P Jullien V Veber F Rouzioux C Chaix ML Blanche S 《Journal of acquired immune deficiency syndromes (1999)》2004,37(2):1269-1275
Predictive factors of the virologic success of the use of lopinavir/ritonavir (LPV/r) in HIV-infected children are unknown, especially in children who have been pretreated with protease inhibitors (PIs). This longitudinal, single-center, observational study included 69 children (21 PI-naive and 48 PI-experienced) who had received LPV/r for at least 3 months. The mean (+/- SD) age was 10.3 +/- 4.8 years, and the mean baseline of CD4 percentage and HIV-1 RNA was 14.9% +/- 9.8% and 4.8 +/- 1.05 log10 copies/mL, respectively. The mean duration of follow-up was 16.5 +/- 8.3 months. At 6, 12, and 18 months, 52%, 57%, and 49% of all children, respectively, had a viral load less than 50 copies/mL. The risk of virologic failure, defined as 2 consecutive viral loads greater than 1000 copies/mL, was significantly higher when the children were previously treated with PIs and when the baseline LPV mutation score exceeded 3 mutations. In the pretreated children, the ratio of the plasma LPV maximal concentration to the baseline LPV score mutation was also associated with failure, independently of resistance score. Finally, in children failing an LPV-containing regimen, accumulation of additional PI-associated resistance mutations was evidenced in viral isolates from children with prior PI treatment, even with viral replication levels less than 10,000 copies/mL. In pretreated children, LPV plasma levels should be optimized in an attempt to achieve sufficient drug concentrations to overcome the resistance level. 相似文献
10.
Disruption of the gene homologous to mammalian Nramp1 in Mycobacterium tuberculosis does not affect virulence in mice
下载免费PDF全文
![点击此处可从《Infection and immunity》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Boechat N Lagier-Roger B Petit S Bordat Y Rauzier J Hance AJ Gicquel B Reyrat JM 《Infection and immunity》2002,70(8):4124-4131
Natural-resistance-associated macrophage protein 1 (Nramp1) is a divalent cation transporter belonging to a family of transporter proteins highly conserved in eukaryotes and prokaryotes. Mammalian and bacterial transporters may compete for essential metal ions during mycobacterial infections. The mycobacterial Nramp homolog may therefore be involved in Mycobacterium tuberculosis virulence. Here, we investigated this possibility by inactivating the M. tuberculosis Nramp1 gene (Mramp) by allelic exchange mutagenesis. Disruption of Mramp did not affect the extracellular growth of bacteria under standard conditions. However, the Mramp mutation was associated with growth impairment under conditions of limited iron availability. The Mramp mutant displayed no impairment of growth or survival in macrophages derived from mouse bone marrow or in Nramp1(+/+) and Nramp1(-/-) congenic murine macrophage cell lines. Following intravenous challenge in BALB/c mice, counts of parental and Mramp mutant strains were similar in the lungs and spleens of the animals at all time points studied. These results indicate that Mramp does not contribute to the virulence of M. tuberculosis in mice. 相似文献