全文获取类型
收费全文 | 947篇 |
免费 | 87篇 |
出版年
2023年 | 12篇 |
2022年 | 22篇 |
2021年 | 26篇 |
2020年 | 16篇 |
2019年 | 25篇 |
2018年 | 40篇 |
2017年 | 41篇 |
2016年 | 38篇 |
2015年 | 71篇 |
2014年 | 61篇 |
2013年 | 63篇 |
2012年 | 51篇 |
2011年 | 52篇 |
2010年 | 52篇 |
2009年 | 26篇 |
2008年 | 35篇 |
2007年 | 44篇 |
2006年 | 35篇 |
2005年 | 32篇 |
2004年 | 25篇 |
2003年 | 30篇 |
2002年 | 15篇 |
2001年 | 22篇 |
2000年 | 20篇 |
1999年 | 17篇 |
1998年 | 9篇 |
1997年 | 11篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 13篇 |
1990年 | 15篇 |
1989年 | 12篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 9篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1977年 | 3篇 |
1972年 | 4篇 |
1971年 | 4篇 |
1969年 | 2篇 |
1962年 | 2篇 |
排序方式: 共有1034条查询结果,搜索用时 140 毫秒
901.
dos Santos Carvalho C de Araujo HS Fernandes MN 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》2004,139(2):225-234
The cladoceran Daphnia pulex is well established as a model for ecotoxicology. Here, we show that D. pulex is also useful for investigating the effects of toxins on the heart in situ and the toxic effects in lactose intolerance. The mean heart rate at 10 degrees C was 195.9+/-27.0 beats/min (n=276, range 89.2-249.2, >80% 170-230 beats/min). D. pulex heart responded to caffeine, isoproteronol, adrenaline, propranolol and carbachol in the bathing medium. Lactose (50-200 mM) inhibited the heart rate by 30-100% (K(1/2)=60 mM) and generated severe arrhythmia within 60 min. These effects were fully reversible by 3-4 h. Sucrose (100-200 mM) also inhibited the heart rate, but glucose (100-200 mM) and galactose (100-200 mM) had no effect, suggesting that the inhibition by lactose or sucrose was not simply an osmotic effect. The potent antibiotic ampicillin did not prevent the lactose inhibition, and two diols known to be generated by bacteria under anaerobic conditions were also without effect. The lack of effect of l-ribose (2 mM), a potent inhibitor of beta-galactosidase, supported the hypothesis that lactose and other disaccharides may affect directly ion channels in the heart. The results show that D. pulex is a novel model system for studying effects of agonists and toxins on cell signalling and ion channels in situ. 相似文献
902.
Inhibition of DNA methyltransferase inhibits DNA replication 总被引:8,自引:0,他引:8
Knox JD Araujo FD Bigey P Slack AD Price GB Zannis-Hadjopoulos M Szyf M 《The Journal of biological chemistry》2000,275(24):17986-17990
Ectopic expression of DNA methyltransferase transforms vertebrate cells, and inhibition of DNA methyltransferase reverses the transformed phenotype by an unknown mechanism. We tested the hypothesis that the presence of an active DNA methyltransferase is required for DNA replication in human non-small cell lung carcinoma A549 cells. We show that the inhibition of DNA methyltransferase by two novel mechanisms negatively affects DNA synthesis and progression through the cell cycle. Competitive polymerase chain reaction of newly synthesized DNA shows decreased origin activity at three previously characterized origins of replication following DNA methyltransferase inhibition. We suggest that the requirement of an active DNA methyltransferase for the functioning of the replication machinery has evolved to coordinate DNA replication and inheritance of the DNA methylation pattern. 相似文献
903.
Maltose transport and maltase activities were inactivated during sporulation of a MAL constitutive yeast strain harboring different MAL loci. Both activities were reduced to almost zero after 5 h of incubation in sporulation medium. The inactivation of maltase and maltose permease seems to be related to optimal sporulation conditions such as a suitable supply of oxygen and cell concentration in the sporulating cultures, and occurs in the fully derepressed conditions of incubation in the sporulation acetate medium. The inactivation of maltase and maltose permease under sporulation conditions in MAL constitutive strains suggests an alternative mechanism for the regulation of the MAL gene expression during the sporulation process. 相似文献
904.
Gomes AP Ramos ML Vasconcellos RS Jensen JR Vieira-Bressan MC Araujo JV 《Memórias do Instituto Oswaldo Cruz》2000,95(6):873-876
In vitro tests were carried out to assess the activity of 26 Brazilian isolates of predatory fungi of the genus Arthrobotrys on a free-living nematode (Panagrellus sp.) and on infective larvae of Haemonchus placei, a parasitic gastrointestinal nematode of cattle. The results showed that the free-living nematode Panagrellus sp. was the most preyed upon, compared to H. placei, for all the fungal treatments. Also, variable predatory capacity was observed for different fungal isolates belonging to the same genus when applied to different nematode species. 相似文献
905.
906.
Ana K.S. Braz Diógenes S. Moura Anderson S.L. Gomes Tymish Y. Ohulchanskyy Guanying Chen Maixian Liu Jossana Damasco Renato E. de Araujo Paras N. Prasad 《Journal of biophotonics》2018,11(4)
Core‐shell nanostructures associated with photonics techniques have found innumerous applications in diagnostics and therapy. In this work, we introduce a novel core‐shell nanostructure design that serves as a multimodal optical imaging contrast agent for dental adhesion evaluation. This nanostructure consists of a rare‐earth‐doped (NaYF4:Yb 60%, Tm 0.5%)/NaYF4 particle as the core (hexagonal prism, ~51 nm base side length) and the highly refractive TiO2 material as the shell (~thickness of 15 nm). We show that the TiO2 shell provides enhanced contrast for optical coherence tomography (OCT), while the rare‐earth‐doped core upconverts excitation light from 975 nm to an emission peaked at 800 nm for photoluminescence imaging. The OCT and the photoluminescence wide‐field images of human tooth were demonstrated with this nanoparticle core‐shell contrast agent. In addition, the described core‐shell nanoparticles (CSNps) were dispersed in the primer of a commercially available dental bonding system, allowing clear identification of dental adhesive layers with OCT. We evaluated that the presence of the CSNp in the adhesive induced an enhancement of 67% scattering coefficient to significantly increase the OCT contrast. Moreover, our results highlight that the upconversion photoluminescence in the near‐infrared spectrum region is suitable for image of deep dental tissue. 相似文献
907.
908.
G K Couto R O Fernandes D Lacerda C Campos-Carraro P Türck S E Bianchi G D Ferreira I S Brum V L Bassani A Belló-Klein A S R Araujo 《Journal of biosciences》2018,43(5):931-940
This study was designed to investigate the effect of pterostilbene (PTS) on cardiac oxidative stress in vitro, as this is a simple and promising methodology to study cardiac disease. Cardiac myoblasts (H9c2 cells) and homogenised cardiac tissue were incubated with the PTS and cyclodextrin (PTS?+?HPβCD) complex for 1 and 24 h, respectively, at concentrations of 50 μM for the cells and 25 and 50 μM for cardiac tissue. The PTS?+?HPβCD complex was used to increase the solubility of PTS in water. After the pretreatment period, cardiomyoblasts were challenged with hydrogen peroxide (6.67 μM) for 10?min, while cardiac tissue was submitted to a hydroxyl radical generator system (30?min). Cellular viability, oxidative stress biomarkers (e.g. total reactive oxygen species (ROS), carbonyl assay and lipoperoxidation) and the antioxidant response (e.g. sulfhydryl and the antioxidant enzyme activities of superoxide dismutase, catalase and glutathione peroxidase) were evaluated. In cardiomyoblasts, the PTS?+?HPβCD complex (50 μM) increased cellular viability. Moreover, the PTS?+?HPβCD complex also significantly increased sulfhydryl levels in the cells submitted to an oxidative challenge. In cardiac tissue, lipid peroxidation, carbonyls and ROS levels were significantly increased in the groups submitted to oxidative damage, while the PTS?+?HPβCD complex significantly reduced ROS levels in these groups. In addition, the PTS?+?HPβCD complex also provoked increased catalase activity in both experimental protocols. These data suggest that the PTS?+?HPβCD complex may play a cardioprotective role through a reduction of ROS levels associated with an improved antioxidant response. 相似文献
909.
Combining high‐pressure freezing with pre‐embedding immunogold electron microscopy and tomography
下载免费PDF全文
![点击此处可从《Traffic (Copenhagen, Denmark)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Michael W. Hess Georg F. Vogel Teodor E. Yordanov Barbara Witting Karin Gutleben Hannes L. Ebner Mariana E. G. de Araujo Przemyslaw A. Filipek Lukas A. Huber 《Traffic (Copenhagen, Denmark)》2018,19(8):639-649
Immunogold labeling of permeabilized whole‐mount cells or thin‐sectioned material is widely used for the subcellular localization of biomolecules at the high spatial resolution of electron microscopy (EM). Those approaches are well compatible with either 3‐dimensional (3D) reconstruction of organelle morphology and antigen distribution or with rapid cryofixation—but not easily with both at once. We describe here a specimen preparation and labeling protocol for animal cell cultures, which represents a novel blend of specifically adapted versions of established techniques. It combines the virtues of reliably preserved organelle ultrastructure, as trapped by rapid freezing within milliseconds followed by freeze‐substitution and specimen rehydration, with the advantages of robust labeling of intracellular constituents in 3D through means of pre‐embedding NANOGOLD‐silver immunocytochemistry. So obtained thin and semi‐thick epoxy resin sections are suitable for transmission EM imaging, as well as tomographic reconstruction and modeling of labeling patterns in the 3D cellular context. 相似文献
910.