全文获取类型
收费全文 | 313篇 |
免费 | 21篇 |
出版年
2023年 | 3篇 |
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 7篇 |
2014年 | 16篇 |
2013年 | 22篇 |
2012年 | 20篇 |
2011年 | 27篇 |
2010年 | 11篇 |
2009年 | 10篇 |
2008年 | 15篇 |
2007年 | 8篇 |
2006年 | 19篇 |
2005年 | 11篇 |
2004年 | 10篇 |
2003年 | 6篇 |
2002年 | 8篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 11篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 11篇 |
1991年 | 7篇 |
1990年 | 11篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 8篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1965年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有334条查询结果,搜索用时 15 毫秒
21.
Calcium protects differentiating neuroblastoma cells during 50 Hz electromagnetic radiation 总被引:3,自引:0,他引:3
下载免费PDF全文
![点击此处可从《Biophysical journal》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Tonini R Baroni MD Masala E Micheletti M Ferroni A Mazzanti M 《Biophysical journal》2001,81(5):2580-2589
Despite growing concern about electromagnetic radiation, the interaction between 50- to 60-Hz fields and biological structures remains obscure. Epidemiological studies have failed to prove a significantly correlation between exposure to radiation fields and particular pathologies. We demonstrate that a 50- to 60-Hz magnetic field interacts with cell differentiation through two opposing mechanisms: it antagonizes the shift in cell membrane surface charges that occur during the early phases of differentiation and it modulates hyperpolarizing K channels by increasing intracellular Ca. The simultaneous onset of both mechanisms prevents alterations in cell differentiation. We propose that cells are normally protected against electromagnetic insult. Pathologies may arise, however, if intracellular Ca regulation or K channel activation malfunctions. 相似文献
22.
23.
Marcella Zollino Rosetta Lecce Marina Murdolo Daniela Orteschi Giuseppe Marangi Angelo Selicorni Alina Midro Giovanni Sorge Giuseppe Zampino Luigi Memo Domenica Battaglia Michael Petersen Effie Pandelia Yolanda Gyftodimou Francesca Faravelli Romano Tenconi Livia Garavelli Laura Mazzanti Rita Fischetto Pietro Cavalli Salvatore Savasta Laura Rodriguez Giovanni Neri 《Human genetics》2008,123(3):319-319
24.
Enantioselective Preparation,Conformational Analysis and Absolute Configuration of Highly Substituted Aziridines
下载免费PDF全文
![点击此处可从《Chirality》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Giorgio Bencivenni Paolo Righi Lodovico Lunazzi Silvia Ranieri Michele Mancinelli Andrea Mazzanti 《Chirality》2015,27(12):875-887
The first example of organocatalytic aziridination reaction of α‐substituted‐α,β‐unsaturated ketones is presented. The reaction was found to be highly enantio‐ and diastereoselective, yielding N‐tosylated aziridines. Low‐temperature nuclear magnetic resonance (NMR) spectra allowed for the determination of the N‐inversion barrier, that was found to be quite lower with respect to unsubstituted aziridines. A thorough conformational analysis supported by low‐temperature NMR data allowed for the determination of the absolute configuration of the main stereoisomer by means of time‐dependent Density Functional Theory simulation of the electronic circular dichroism spectra. Chirality 27:875–887, 2015. © 2015 Wiley Periodicals, Inc. 相似文献
25.
26.
Littler DR Assaad NN Harrop SJ Brown LJ Pankhurst GJ Luciani P Aguilar MI Mazzanti M Berryman MA Breit SN Curmi PM 《The FEBS journal》2005,272(19):4996-5007
The structure of CLIC4, a member of the CLIC family of putative intracellular chloride ion channel proteins, has been determined at 1.8 Angstroms resolution by X-ray crystallography. The protein is monomeric and it is structurally similar to CLIC1, belonging to the GST fold class. Differences between the structures of CLIC1 and CLIC4 are localized to helix 2 in the glutaredoxin-like N-terminal domain, which has previously been shown to undergo a dramatic structural change in CLIC1 upon oxidation. The structural differences in this region correlate with the sequence differences, where the CLIC1 sequence appears to be atypical of the family. Purified, recombinant, wild-type CLIC4 is shown to bind to artificial lipid bilayers, induce a chloride efflux current when associated with artificial liposomes and produce an ion channel in artificial bilayers with a conductance of 30 pS. Membrane binding is enhanced by oxidation of CLIC4 while no channels were observed via tip-dip electrophysiology in the presence of a reducing agent. Thus, recombinant CLIC4 appears to be able to form a redox-regulated ion channel in the absence of any partner proteins. 相似文献
27.
The presence of Fe(III), but not that of Fe(II), resulted in ca. 20-fold-lower levels of mRNA for fumarate reductase, inhibiting fumarate reduction and favoring utilization of fumarate as an electron donor in chemostat cultures of Geobacter sulfurreducens, despite the fact that growth yield with fumarate was 3-fold higher than with Fe(III). 相似文献
28.
29.
Cinthia Bachir Moysés Maria de Fatima Zambelli Daniel-Silva Carlos Eduardo Lopes Lurdes Foresti de Almeida-Toledo 《Genetica》2010,138(2):179-189
The genus Eigenmannia (Teleostei: Gymnotiformes), a widely distributed fish genus from the Neotropical region, presents very complex morphological patterns and many taxonomic problems. It is suggested that this genus harbors a species complex that is hard to differentiate using only morphological characteristics. As a result, many species of Eigenmannia may be currently gathered under a common name. With the objective of providing new tools for species characterization in this group, an analysis of the polymorphism of DNA inter-simple sequence repeats (ISSR), obtained by single primer amplification reaction (SPAR), combined with karyotype identification, was carried out in specimens sampled from populations of the Upper Paraná, São Francisco and Amazon river basins (Brazil). Specific ISSR patterns generated by primers (AAGC)4 and (GGAC)4 were found to characterize the ten cytotypes analyzed, even though the cytotypes 2n = 38 and 2n = 38 XX:XY, from the Upper Paraná basin, share some ISSR amplification patterns. The geographical distribution of all Eigenmannia specimens sampled was inferred, showing the cytotype 2n = 31/2n = 32 as the most frequent and largely distributed in the Upper Paraná basin. The cytotype 2n = 34 was reported for the first time in the genus Eigenmania, restricted to the São Francisco basin. Polymorphic ISSR patterns were also detected for each cytotype. Considering our results and the data reported previously in the literature, it is suggested that many of the forms of Eigenmannia herein analyzed might be regarded as different species. This work reinforces the importance of employing diverse approaches, such as molecular and cytogenetic characterization, to address taxonomic and evolutionary issues. 相似文献
30.
Spanevello RM Mazzanti CM Kaizer R Zanin R Cargnelutti D Hannel L Côrrea M Mazzanti A Festugatto R Graça D Schetinger MR Morsch VM 《Neurochemical research》2006,31(4):455-462
Apyrase and 5′-nucleotidase activities were analyzed in an ethidium bromide (EB) demyelinating model associated with interferon-β (IFN-β). The animals were divided in groups: I, control (saline); II, saline and IFN-β; III, EB and IV, EB and IFN-β. After 7, 15 and 30 days the animals (n=5) were sacrificed and the cerebral cortex was removed for synaptosome preparation and enzymatic assays. Apyrase activity using ATP as substrate increased in groups II, III and IV (P<0.001) after 7 days and in groups III and IV (P<0.001) after 15 days. Using ADP as substrate, an activation of this enzyme was observed in group III (P<0.05) after seven and 15 days. The 5′-nucleotidase activity increased in group III (P<0.05) after 7 days and in groups II, III and IV (P<0.001) after 15 days. After 30 days treatment, no significant alteration was observed in enzyme activities. Results showed that apyrase and 5′-nucleotidase activities are altered in demyelination events and that IFN-β was able to regulate the adenine nucleotide hydrolysis. 相似文献