全文获取类型
收费全文 | 5209篇 |
免费 | 411篇 |
出版年
2024年 | 2篇 |
2023年 | 31篇 |
2022年 | 21篇 |
2021年 | 128篇 |
2020年 | 68篇 |
2019年 | 116篇 |
2018年 | 137篇 |
2017年 | 128篇 |
2016年 | 195篇 |
2015年 | 300篇 |
2014年 | 331篇 |
2013年 | 432篇 |
2012年 | 509篇 |
2011年 | 487篇 |
2010年 | 299篇 |
2009年 | 243篇 |
2008年 | 332篇 |
2007年 | 337篇 |
2006年 | 309篇 |
2005年 | 249篇 |
2004年 | 242篇 |
2003年 | 215篇 |
2002年 | 192篇 |
2001年 | 31篇 |
2000年 | 19篇 |
1999年 | 27篇 |
1998年 | 43篇 |
1997年 | 15篇 |
1996年 | 21篇 |
1995年 | 20篇 |
1994年 | 13篇 |
1993年 | 13篇 |
1992年 | 26篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1975年 | 2篇 |
1939年 | 1篇 |
排序方式: 共有5620条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Francesca Pecori‐Giraldi Giuseppina Manzoni Jorgo Michailidis Massimo Scacchi Marco Stramba‐Badiale Francesco Cavagnini 《Obesity (Silver Spring, Md.)》2011,19(10):2015-2018
Obese subjects show several electrocardiographic alterations, including prolonged QT interval, a marker for fatal cardiac arrhythmias. Prolonged QT interval has recently been linked to low testosterone levels, a frequent occurrence in male obese patients but no study has yet assessed whether hypoandrogenism contributes to QT interval prolongation in this population. Aim of this study was to evaluate whether prolonged QT interval is linked to hypogonadism in male obese subjects. QT interval corrected for heart rate (QTc) was measured from standard electrocardiogram recordings in 136 obese men (BMI 30 >kg/m2, range 30.1–75.4 kg/m2). Obese men were classified as eugonadal or hypogonadal according to serum total testosterone levels (i.e., greater or less than 9.9 nmol/l). Our study showed that QTc measurements corrected by either Bazett (419 ± 3.2 vs. 408 ± 3.4 ms, P < 0.05), Fridericia (406.3 ± 3.39 vs. 396.4 ± 3.03 ms, P < 0.05) or Hodges (407.0 ± 3.12 vs. 397.3 ± 2.84 ms, P < 0.05) were longer in hypogonadal compared with eugonadal obese men; further, prolonged QTc interval (i.e., >440 ms) was more frequent among hypogonadal compared with eugonadal obese men (23% vs. 10%, P < 0.05). The degree of weight excess, diabetes, sleep apnoea and potassium levels were not associated with prolonged QTc. In conclusion, obese hypogonadal men show a greater prevalence of prolonged QT interval compared with their eugonadal counterparts. It appears therefore that low levels of testosterone in obese men may contribute to the arrhythmogenic profile of these patients, a heretofore unknown link which warrants further clinical attention. 相似文献
5.
Cristiano Carlomagno Monia Cabinio Silvia Picciolini Alice Gualerzi Francesca Baglio Marzia Bedoni 《Journal of biophotonics》2020,13(3)
Alzheimer disease (AD) is the most common form of dementia in the elderly, progressively affecting the cognitive functions with a complex diagnostic procedure that limits the time for a prompt intervention. In this study we optimized a reliable protocol for the analysis of AD patients and healthy subjects' serum using the Surface Enhanced Raman Spectroscopy (SERS), taking into consideration the effect of different variables on the final spectra, analyzed and compared through multivariate analysis and correlated with hippocampus volume. As results, we demonstrated a statistical difference between the spectra collected from the two investigated groups, with an accuracy, precision and specificity of respectively 83%, 86%, and 86%. The correlation of these data with those obtained from MRI, demonstrated a direct correlation between Raman spectra and hippocampus degeneration showing the Raman Spectroscopy (RS) as a potential tool for the monitoring of AD progression and rehabilitation treatments. 相似文献
6.
7.
Magdalena Brzezowska Francesca Bernardi Nicola Gaggelli Gianni Valensin 《Journal of inorganic biochemistry》2010,104(2):193-198
Teicoplanin, a member of the “last chance” antibiotic family has a similar structure and the same mechanism of action as parent drug vancomycin, which is proved to be an effective binder of Cu(II) ions. However, the potentiometric and spectroscopic studies (UV-visible, CD, NMR) have shown that the modification of the N-terminal structure of the peptide backbone in teicoplanin affects considerably the binding ability towards Cu(II) ions. While vancomycin forms almost instantly the stable 3 N complex species involving the N-terminal and two amide nitrogen donors, in case of teicoplanin only two nitrogen donors derived from the N-terminal amino group and adjacent peptide bond are coordinated to Cu(II) ion within the whole pH range studied. The major factor influencing the binding mode is most likely the structure of the N-terminus of the peptide unit in the antibiotic ligand. 相似文献
8.
9.
Marcello Ventura Barbara Rieck Francesca Boldrin Giulia Degiacomi Marco Bellinzoni Nathalie Barilone Faisal Alzaidi Pedro M. Alzari Riccardo Manganelli Helen M. O'Hare 《Molecular microbiology》2013,90(2):356-366
Alpha‐ketoglutarate is a key metabolic intermediate at the crossroads of carbon and nitrogen metabolism, whose fate is tightly regulated. In mycobacteria the protein GarA regulates the tricarboxylic acid cycle and glutamate synthesis by direct binding and regulation of three enzymes that use α‐ketoglutarate. GarA, in turn, is thought to be regulated via phosphorylation by protein kinase G and other kinases. We have investigated the requirement for GarA for metabolic regulation during growth in vitro and in macrophages. GarA was found to be essential to Mycobacterium tuberculosis, but dispensable in non‐pathogenic Mycobacterium smegmatis. Disruption of garA caused a distinctive, nutrient‐dependent phenotype, fitting with its proposed role in regulating glutamate metabolism. The data underline the importance of the TCA cycle and the balance with glutamate synthesis in M. tuberculosis and reveal vulnerability to disruption of these pathways. 相似文献
10.
In this article we discuss the moral and legal aspects of causing the death of a terminal patient in the hope of extending their life in the future. We call this theoretical procedure cryothanasia. We argue that administering cryothanasia is ethically different from administering euthanasia. Consequently, objections to euthanasia should not apply to cryothanasia, and cryothanasia could also be considered a legal option where euthanasia is illegal. 相似文献