全文获取类型
收费全文 | 635篇 |
免费 | 41篇 |
专业分类
676篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 12篇 |
2020年 | 6篇 |
2019年 | 13篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 21篇 |
2015年 | 32篇 |
2014年 | 25篇 |
2013年 | 45篇 |
2012年 | 56篇 |
2011年 | 54篇 |
2010年 | 20篇 |
2009年 | 33篇 |
2008年 | 57篇 |
2007年 | 44篇 |
2006年 | 32篇 |
2005年 | 32篇 |
2004年 | 56篇 |
2003年 | 23篇 |
2002年 | 27篇 |
2001年 | 5篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 7篇 |
1997年 | 9篇 |
1996年 | 5篇 |
1995年 | 9篇 |
1994年 | 9篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有676条查询结果,搜索用时 15 毫秒
21.
Mathews II Krishna SS Schwarzenbacher R McMullan D Jaroszewski L Miller MD Abdubek P Agarwalla S Ambing E Axelrod HL Canaves JM Carlton D Chiu HJ Clayton T DiDonato M Duan L Elsliger MA Grzechnik SK Hale J Hampton E Haugen J Jin KK Klock HE Koesema E Kovarik JS Kreusch A Kuhn P Levin I Morse AT Nigoghossian E Okach L Oommachen S Paulsen J Quijano K Reyes R Rife CL Spraggon G Stevens RC van den Bedem H White A Wolf G Xu Q Hodgson KO Wooley J Deacon AM Godzik A Lesley SA Wilson IA 《Proteins》2006,65(1):249-254
22.
23.
Joan?GomàEmail author Frédéric?Rimet Jaume?Cambra Lucien?Hoffmann Luc?Ector 《Hydrobiologia》2005,551(1):209-225
Epilithic diatoms of mountain rivers from the upper Segre catchment (Oriental Pyrenees) were studied in 1998, during three
different seasons: March, July and September. Four rivers, the river Segre and its three most important tributaries, Duran,
Molina and Querol, were sampled in upstream and downstream stretches. The diatom communities were comparable in all upstream
stretches of these mountain rivers draining siliceous substrates. Dominant taxa were Achnanthidium subatomus, Diatoma mesodon, Encyonema cf. minutum, E. silesiacum, Fragilaria arcus, F. capucina, Gomphonema calcifugum, G. pumilum, Meridion circulare and Nitzschia pura. Changes in water quality in the downstream stretches lead to the appearance of pollution tolerant taxa, such as Eolimna minima, Gomphoneis minuta, Navicula gregaria, and Nitzschia inconspicua. As a result, the values obtained with the diatom water quality indices (IPS Specific Polluosensitivity Index, CEE and IBD
Biological Diatom Index) decreased. The diatom community composition and the derived water quality values did not change in
the upstream stretches over the year. In contrast, significant changes were observed in the downstream stretches with best
water␣quality in July, during high flows due to melting snow, and worst values in September, during low␣discharge. The diatom
indices, especially the IPS, showed a good performance in these mountain rivers. 相似文献
24.
25.
26.
27.
Aiming to provide a tentative framework for the study of the neural correlates of aesthetic preference, we review three recent neuroimaging studies carried out with the purpose of locating brain activity associated with decisions about the beauty of visual stimuli (Cela-Conde et al., 2004; Kawabata and Zeki, 2004; Vartanian and Goel, 2004). We find that the results of the three studies are not in line with previous neuropsychological data. Moreover, there are no coincidences among their results. However, when they are mapped on to Chatterjee's (2003) neuropsychological model of aesthetic preference it becomes clear that neuroimaging data are not contradictory, but complementary, and their interpretation is enriched. The results of these studies suggest that affective processes have an important role in aesthetic preference, and that they are integrated with cognitive processes to reach a decision regarding the beauty of visual stimuli. Future studies must aim to clarify whether certain methodological procedures are better suited to study any of the particular cognitive operations involved in aesthetic preference, and ascertain the extent to which the proposed framework is compatible with the aesthetic appreciation of musical stimuli. 相似文献
28.
Ana Rodríguez-Campello Jordi Jiménez-Conde ángel Ois Elisa Cuadrado-Godia Eva Giralt-Steinhauer Helmut Schroeder Gemma Romeral Mireia Llop Carolina Soriano-Tárraga Montserrat Garralda-Anaya Jaume Roquer 《PloS one》2014,9(12)
Background and Aims
Diet appears to have some role in stroke development. The objective of our study was to describe the dietary habits in patients admitted with acute ischemic stroke and compare selected dietary components with healthy controls. Adherence to healthy diet behaviors was also assessed.Methods
A case-control study of consecutive patients with acute ischemic stroke admitted to the Neurology Department of Hospital del Mar from 2007 to 2010. Patients were matched by age and sex with control subjects. A previously validated nutritional survey was administered to patients and controls. Demographic data, vascular risk factors, caloric intake and dietary nutrients were evaluated. Intention to follow a healthy diet was also assessed in both groups.Results
A total of 300 acute ischemic stroke patients and 300 controls with evaluation of dietary habits. No differences were observed in vascular risk factors, except smoking habit, diabetes and ischemic heart disease. Stroke patients reported a higher caloric intake: 2444.8(1736.8–3244.5) vs 2208.7(1753.1–2860.7) Kcal, p = 0.001. After adjusting for energy intake, patients had higher intake of proteins (p<0.001; OR 1.02), total cholesterol (p = 0.001; OR 1.04), and breaded foods (p = 0.001; OR 1.94) and lower consumption of probiotic yogurt (p = 0.002; OR 0.88). Compared to patients, control participants indicated greater intention to eat vegetables (p = 0.002; OR 1.5) and whole foods (p = 0.000; OR 2.4) and reduce their intake of salt (p = 0.002; OR 1.7), fat (p = 0.000; OR 3.7) and sweets (p = 0.004; OR 1.7) than patients.Conclusion
We observed different dietary patterns between stroke patients and controls. Stroke patients have a higher caloric intake and are less concerned about maintaining healthy nutritional habits. 相似文献29.
30.
Parthasarathy K Ng L Lin X Liu DX Pervushin K Gong X Torres J 《Biophysical journal》2008,95(6):L39-L41
Coronaviruses contain a small envelope membrane protein with cation-selective ion channel activity mediated by its transmembrane domain (ETM). In a computational study, we proposed that ion channel activity can be explained by either of two similar ETM homopentameric transmembrane α-helical bundles, related by a ∼50° rotation of the helices. Later, we tested this prediction, using site-specific infrared dichroism of a lysine-flanked isotopically labeled ETM peptide from the virus responsible for the severe acute respiratory syndrome, SARS, reconstituted in lipid bilayers. However, the data were consistent with the presence of a kink at the center of the ETM α-helix, and it did not fit completely either computational model. Herein, we have used native ETM, without flanking lysines, and show that the helix orientation is now consistent with one of the predicted models. ETM only produced one oligomeric form, pentamers, in the lipid-mimic detergent dodecylphosphocholine and in perfluorooctanoic acid. We thus report the correct backbone model for the pentameric α-helical bundle of ETM. The disruptive effects caused by terminal lysines probably highlight the conformational flexibility required during ion channel function. 相似文献